The 2020 London International Hamstring Consensus meeting was convened to improve our understanding and treatment of hamstring injuries.

The multidisciplinary consensus panel included 14 International specialists on the management of hamstring injuries. The Delphi consensus process consisted of two rounds of surveys which were completed by 19 surgeons from a total of 106 participants. Consensus on individual statements was regarded as over 70% agreement between panel members.

The consensus group agreed that the indications for operative intervention included the following: gapping at the zone of injury (86.9%); high functional demands of the patient (86.7%); symptomatic displaced bony avulsions (74.7%); and proximal free tendon injuries with functional compromise refractory to non-operative treatment (71.4%). Panel members agreed that surgical intervention had the capacity to restore anatomy and function, while reducing the risk of injury recurrence (86.7%). The consensus group did not support the use of corticosteroids or endoscopic surgery without further evidence.

These guidelines will help to further standardise the treatment of hamstring injuries and facilitate decision-making in the surgical treatment of these injuries.

Problem

Total hip replacement (THA) is among the most common and highest total spend elective operations in the United States. However, up to 7% of patients have 90-day complications after surgery, most frequently joint dislocation that is related to poor acetabular component positioning. These complications lead to patient morbidity and mortality, as well as significant cost to the health system. As such, surgeons and hospitals value navigation technology, but existing solutions including robotics and optical navigation are costly, time-consuming, and complex to learn, resulting in limited uptake globally.

Introduction

Lumbar spine fusion in patients undergoing THA (total hip arthroplasty) is a known risk factor for hip dislocation with some studies showing a 400% increased incidence compared to the overall THA population. Reduced spine flexibility can effectively narrow the cup anteversion safe zone while alterations in pelvic tilt can alter the center of the anteversion safe zone. The use of precision cup alignment technology combined with patient-specific cup alignment goals based on preoperative assessment has been suggested as a method of addressing this problem. The current study assess the dislocation rate of THA patients with stiff or fused lumbar spines treated using surgical navigation with patient-specific cup orientation goals.

Introduction

The effect of spine-pelvis position and motion on hip arthroplasty function has been increasingly appreciated in the past several years. Some authors have stressed the importance of using precision technologies for component placement while others have advocated the use of dual mobility articulations or large bearings and lateralized liners in patients with fused lumbar spines. The current study assesses the prevalence of stiff and fused spines in an elective total hip arthroplasty population.

The Superior Hip Approach allows for safe reconstruction of the hip while maximizing preservation of the surrounding soft tissues. The procedure involves an incision in the hip joint capsule posterior to the gluteus medius and minimus and anterior to the short external rotators. The technique involves preparation of the femur in-situ through the superior femoral neck and then excision of the femoral head, which avoids the attendant soft tissue dissection or injury associated with dislocation of the native hip. After component implantation, the capsule is closed anatomically.

Two separate studies have demonstrated that over a 90-day period, patients whose hips were replaced using this technique consumed the least amount of cost of any patients treated by hip arthroplasty in the Commonwealth of Massachusetts. One study assessed all hips replaced in patients insured by Medicare over a four-year period. In this study, patients treated by the Superior Hip Approach were less costly by an average of more than $7,000 over 90 days. A second study assessed all hips replaced in patients insured by a large private insurer. This study showed again that patients treated by the Superior Hip Approach were the lowest cost patients. Notable, the cost on average was $23,500 less per procedure compared to the most well-known medical care organization in the state or roughly half the cost. Lower cost was due to both lower inpatient cost and reduced utilization of post-acute care resources. Since reduced resource utilization is a direct measure of accelerated recovery, these economic data combine with clinical outcomes and anatomical studies that document that the Superior Hip Approach is a reliable technique for achieving optimal results following THA.

INTRODUCTION

In the United States, the Centers for Medicare and Medicaid Services consider rates of unplanned hospital readmissions to be indicators of provider quality. Understanding the common reasons for readmission following total joint arthroplasty will allow for improved standards of care and better outcomes for patients. The current study seeks to evaluate the rates, reasons, and Medicare costs for readmission after total hip and total knee arthroplasty.

Economic data, clinical outcome studies, and anatomical studies continue to support the Superior Hip Approach as a preferred approach for improved safety, maximal tissue preservation, rapid recovery, and minimised cost.

Clinical studies show exceedingly low rates of all major complications including femur fracture, dislocation, and nerve injury.

Economic data from Q1 2013 to Q2 2016 demonstrate that CMS-insured patients treated by the Superior Hip Approach have the lowest cost of all patients treated in Massachusetts by an average of more than $7,000 over 90 days. The data show that the patients treated by the Superior Hip Approach have lower cost than any other surgical technique.

Matched-pair bioskills dissections demonstrate far better preservation of the hip joint capsule and short external rotators than the anterior approach.

Design principles include: Preservation of the abductors; Preservation of the posterior capsule and short external rotators; Preparation of the femur in situ prior to femoral neck osteotomy; Excision of the femoral head, thereby avoiding surgical dislocation of the hip; In-line access to the femoral shaft axis; Ability to perform a trial reduction; Independence from intra-operative imaging; Independence from a traction table; Applicable to at least 99% of THA procedures.

Pre-operative knowledge

Knowledge-based total hip arthroplasty is becoming increasingly recognised for improved safety, efficiency, and accuracy. Pre-operative knowledge of native and planned femoral anteversion, the exact size of implants, neck length and offset, and head lengths can serve to safely accelerate surgery and reduce the need for intra-operative imaging. Pre-operative knowledge of the effect on change in leg length and offset effected by specific implant combinations can serve to minimise undesired changes. The use of a smart mechanical navigation tool superimposed on this knowledge, can serve to easily and swiftly achieve optimal component position.

INTRODUCTION

Interest in tissue-preserving or minimally invasive total hip arthroplasty (THA) is increasing with focus toward decreased hospital stay, enhanced rehabilitation, and quicker recovery for patients. Two tissue-preserving techniques, the anterior and superior approaches to THA, have excellent clinical results, but little is known about their relative impact on soft tissue. The purpose of this study was to evaluate the type and extent of tissue damage after THA with each approach, focusing on abductors, short external rotators, and the hip capsule.

Goals for total hip arthroplasty include acceleration of recovery, optimisation of component placement, minimisation of peri-operative complications, and maximal preservation of surrounding soft tissues. Achieving these goals when combined with appropriate implant design and manufacture can lead to decades of excellent hip function.

With the exception of relatively rapid recovery, which can also be achieved with virtually all modern surgical exposures, the anterior hip approach fails to reliably achieve these goals. Problems with the anterior exposure for total hip arthroplasty are becoming increasingly recognised. Complications with equal or higher incidences than alternative exposures include: 1.) Early wound complications, 2.) Infection, 3.) Intra-operative and post-operative femur fracture, 4.) Greater trochanteric fracture, 5.) Dislocation, 6.) Femoral component loosening, 7.) Poor component placement, 8.) Poor soft tissue balance, 9.) Incisions with poor aesthetics and associated superficial hypaesthesia and dysaesthesia.

These complications may be in part due to: 1.) The anterior and posterior soft tissue releases often necessary to complete the exposure, 2.) Poor ability to anatomically repair the hip joint capsule, 3.) Reduced choices of femoral components with restriction generally to those with less robust fixation, 4.) The poorly extensile nature of the interval, 5.) The need to place the incision in the region of the flexion crease, 6.) The limited ability to assess soft tissue balance and impingement-free range of motion at the time of surgery, 7.) The undue reliance on unvalidated, inaccurate imaging techniques to assess component placement.

While experienced surgeons can achieve excellent results with the anterior (or virtually any other) exposure for total hip arthroplasty, the anterior exposure is by no means close to being a first among equals.

Excellent outcomes following total hip arthroplasty require both optimal soft-tissue management and precise planning and placement of prosthetic components. The use of detailed and dynamic three-dimensional surgical plans combined with smart mechanical instruments for component placement facilitates precise and efficient surgery. Interest in these technologies has increased recently as surgeons and institutions are now responsible for poor outcomes in a growing percentage of the patient population.

Cloud-based, patient-specific planning allows the surgeon to review and refine and execute surgical plans efficiently (HipXpert System, Surgical Planning Associates, Boston, MA). The surgical plans include cup size, cup orientation, stem size, head length, femoral anteversion, and planned change in leg length and offset, all in relation to the patients bony anatomy in 3D and multiplanar views. The associated smart tool is adjusted specifically for that patient and when docked, provides orientation information to the surgeon.

The system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases including by an independent study. This compares to a recent study of robotic methods that 88% of inclination and 84% for anteversion and to even greater inaccuracy of conventional surgery.

Cloud-based 3D planning combined with smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problems of component sizing, orientation, and version, offset, and leg length correction. Knowledge of component sizing pre-operatively can facility inventory management and allows the surgery team to better anticipate the surgeon's goals during the procedure.

The high and ever increasing cost of medical care worldwide has driven a trend toward new payment models. Event based models (such as bundled payment for surgical events) have shown a greater potential for care and cost improvement than population-based models (such as accountable care organizations). Since joint replacement is among the most frequent and costly surgical events in medicine, bundled payments for joint replacement episodes have been at the forefront of evolution from fee-for-service to value-based care models and episode-based healthcare reform in general.

Our education as surgeons in medical school, residency, fellowship, and in continuing education has been almost entirely non-economic in focus. Yet, we surgeons are now evolving from being primarily responsive for our patients' medical care to being also responsible for all expenditures associated with our patients' care. Similarly, while the cost of our patients' care was not even available to us, every dollar of expenditure for a patient's episode of care is now available to us in some circumstances. For example, a typical primary joint replacement episode may cost $30,000 for a patient insured by Medicare in the US. A surgeon performing 400 joint replacements per year is therefore authorizing upwards of $12M a year in health care spending by making the decisions to perform reconstructive procedures on those patients.

The risk for value-based surgical episodes of care can be born by various entities including hospital systems or the surgeons themselves. Recent evidence demonstrates that quality improves and cost decreases more rapidly when surgeons take primary responsibility and risk for episodes of care as compared to when a hospital system or third party takes primary responsibility and risk. Yet, as surgeons, our education in the field of medical economics, value-based episodes of care, and payment reform is only just beginning. The more we understand about the cost and value of the services that we order for our patients, the more leadership can provide as healthcare evolves. The current presentation will describe the specific cost of care for the primary joint replacement patient preliminary experience with accepting risk and responsibility for these patients. It is likely that our patients will be best served if we surgeons provide as much leadership as possible in their care, both medically and economically.

Distal neck modularity places a modular connection at a mechanically critical location, which is also the location that confers perhaps the greatest clinical utility. The benefits of increased clinical options at that location must be weighed against the potential risks of adding an additional junction to the construct. Those risks include prosthetic neck fracture, taper corrosion, metal hypersensitivity, and adverse local tissue reaction. Further, in-vitro testing of ultimate or fatigue strength of femoral component designs has repeatedly failed to predict behavior in-vivo, raising questions about the utility of in-vitro testing that does not incorporate the effect of mechanically assisted crevice corrosion into the test design.

The material properties of Ti alloy and CoCr alloy place limits on design considerations in the proximal femur. The smaller taper junctions that are necessary for primary reconstruction are particularly vulnerable to failure whereas larger taper junctions commonly used in revision modular femoral component designs have greater opportunity for success. Modular junctions of CoCr alloy on conventional Ti alloy have been shown to have a greater incidence of clinically significant mechanically assisted crevice corrosion and adverse reaction. Designs that have proven clinical strength and utility universally have larger, more robust junctions, that extend into the metaphysis of the femur. While these designs are primarily designed for revision total hip replacement (THR), they are occasionally indicated for primary THR. Overall, however, while design options at the neck-stem junction have unmatched clinical utility, no design that does not extend into the metaphysis has proven to be universally reliable. While routine use of modular neck components for primary THR does not appear to be clinically indicated based on current evidence, modular designs with proven successful proximal junctions appear to be indicated for revision THR and rare primary THR with extreme version or other anatomical circumstances.

Introduction

Bundled budgeting of payments for joint replacement services has become increasing common in an effort to improve quality while lowering cost. In the US, some Medicare bundled payment programs are voluntary whereas some now are mandatory. Large medical care and medical management organizations have largely been assigned or seized control of management of these programs, leaving the surgeon in a subordinate role. The current abstract describes an experience where surgeons provide leadership and accept responsibility in bundled payment program.

Introduction

While total hip arthroplasty is considered to be one of the most cost-effective medical interventions, the total cost of care for a population patients treated by THR can present a significant burden on the payer, whether it be an employer, private insurer or government. Data on the true cost of care has rarely been made available to the treating physician. Such lack of information makes comprehensive management difficult. Bundled payment models of care require knowledge of all costs associated with the care of our patients and opens new opportunity for analysis to improve management and outcomes. The current study assess the influence of surgical technique on total cost of care for total hip arthroplasty.

BACKGROUND

Ideal treatment of displaced femoral neck fragility fractures in the previously ambulatory patient remains controversial. Treating these patients with total hip arthroplasty has improved patient reported outcomes and reduced rates of revision surgery compared to those treated with hemiarthroplasty. However, possible increased risk of dislocation remains a concern with total hip arthroplasty.

The anterolateral and direct anterior approaches to total hip replacement have been applied in the femoral neck fracture population to minimize dislocation rates. However, the anterolateral approach has been associated with abductor injury and increased rates of heterotopic ossification while the anterior approach has been associated with peri-prosthetic femur fracture, lateral femoral cutaneous nerve injury, and wound complications. The Supercapsular Percutaneously Assisted (SuperPATH) approach was developed to minimize disruption of the capsule and short-external rotators in an effort to reduce the risk of dislocation and assist in quicker recovery in the elective hip arthroplasty setting. To achieve this, the SuperPATH technique allows the femur to be prepared in situ and the acetabulum to be reamed percutaneously once the femoral head is removed.

This study investigates the post-operative time to ambulation, length of stay, discharge destination, and early dislocation rate of previously ambulatory patients with a displaced femoral neck fragility fracture that were treated with a total hip arthroplasty via the SuperPATH technique.

Introduction

Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago1. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation by comparing the orientation of acetabular components revised due to recurrent instability and to a series of stable hip replacements.

Introduction

Navigation of acetabular component orientation is still not commonly performed despite repeated studies that show that more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned¹. The current study uses postoperative CT to assess the accuracy of a smart mechanical navigation instrument system for cup alignment.

INTRODUCTION

Patients less than 60 years old have been reported to have a higher risk of revision following total hip arthroplasty (THA) than older patient cohorts, possibly to due higher activity, a higher incidence of deformity and greater probability of prior surgery. Ceramic-on-ceramic bearing surfaces have been proposed for use in young and active individuals due to their low wear, low risk of adverse biologic reaction, and long-term survivorship. We assessed the clinical results and long-term survivorship of uncemented ceramic-on-ceramic THA in a young patient population.

Distal neck modularity places a modular connection at a mechanically critical location which is also the location that confers perhaps the greatest clinical utility. Assessment of femoral anteversion in 342 of our total hip replacement (THR) patients by CT showed a range from −24 to 61 degrees. The use of monoblock stems in some of these deformed femurs therefore must result in a failure to appropriately reconstruct the hip and have increased risks of impingement, instability, accelerated bearing wear or fracture, and adverse local tissue reaction (ALTR). However, the risks of failing to properly reconstruct the hip without neck modularity must be weighed against the additional risks introduced by neck modularity.

There are several critical design, material, and technique variables that are directly associated with higher or lower incidences of problems associated with modular neck femoral components. Unfortunately, in vitro testing of the fatigue strength of these constructs has failed to predict their behavior in vivo. Designs predicted to tolerate loads that far exceed those experienced in vivo still fail at unacceptably high rates. Titanium alloy neck components subjected to the stresses at the neck-stem junction continue to fail at an unacceptable incidence. CoCr alloy neck components, while theoretically stronger, still fracture and are further compromised by mechanically assisted crevice corrosion, metal hypersensitivity, and rarely, adverse tissue reaction.

Designs that have proven clinical strength and utility universally have larger, more robust junctions that extend into the metaphysis of the femur. While these designs are primarily designed for revision THR, they are occasionally indicated for primary THR. Overall, however, while design options at the neck-stem junction have unmatched clinical utility, no design that does not extend into the metaphysis has proven to be universally reliable. While routine use for primary THR does not appear clinically indicated based on current evidence, modular designs with proven successful proximal junctions appear to be indicated for extreme version or anatomical circumstances.

Acetabular component malalignment remains the single greatest root cause for revision THA with malposition of at least half of all acetabular components placed using conventional methods. These studies repeatedly document that the concept of using local anatomical landmarks has no scientific basis over a breadth of presenting pathology. Traditional navigation and robotics can potentially lead to improved component placement but these technologies have not gained widespread use due to the increase in time of use, complexity, and cost of these systems. Robotic systems have also proven to be potentially hazardous and inaccurate in routine clinical use. The alternative of placing the cup in the supine position, even with the use of arthroscopy, has been proven to have an incidence of inaccuracy equal or greater than that in the lateral position.

A smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment (HipXpert System, Surgical Planning Associates, Boston, MA). The system is based on a low dose, low cost CT study and a customised patient-specific surgery plan. The laterally-based system docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. The anteriorly-based system also docks on a patient-specific basis with one leg on the anterior ischium and one leg on each ASIS, either to skin or to bone.

The lateral system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases and an independent study showing accurate cup placement in 98% of cases for both anteversion and inclination. This compares to a recent study of robotic methods that 88% of inclination and 84% for anteversion.

Smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problem of acetabular component malorientation.

Management of recurrent instability of the hip requires careful assessment to determine any identifiable causative factors. While plain radiographs can give a general impression, CT is the best methodology for objective measurement. Variables that can be measured include: prosthetic femoral anteversion, comparison to contralateral native femoral anteversion, total offset from the medial wall of the pelvis to the lateral side of the greater trochanter, comparison to total offset on the contralateral side, acetabular inclination, & acetabular anteversion.

Wera et al describe potential causes of instability. These are typed into I. Acetabular Component Malposition; II. Femoral Component Malposition; III. Abductor Deficiency; IV. Impingement; V. Late Wear; and VI. Unknown.

Acetabular component malposition is the most common cause of instability and so measurement of cup orientation is essential. It is well known that excessive or inadequate anteversion can lead to anterior and posterior dislocation respectively but horizontal components are also associated with posterior dislocation due to deficient posterior/inferior acetabular surface.

Similarly, excessive or inadequate femoral anteversion can be easily identified on CT as can insufficient total offset of the reconstructed joint compared to the contralateral side. This can be caused by medialization of the acetabular component.

Abductor deficiency can be a soft-tissue cause of instability, but it certainly isn't the only one. Knowledge of the prior surgical exposure can be instructive. Anterior exposures can be prone to deficient anterior capsule just as posterior exposures can be prone to deficient posterior capsule and short rotators, while anterolateral and lateral exposures can be associated with gluteus minimus and gluteus medius compromise.

Impingement, whether involving implants, bone, or soft tissue are primarily secondary to the above factors, if osteophytes were properly trimmed at the index procedure.

Correction of the incorrect variables is the primary goal of revision for instability and greatly preferable to using salvage options such as dual-mobility or constrained articulations which invoke additional concerns. Ultimately though, such salvage options are necessary if the cause of the instability cannot be determined or can be determined but not corrected. Bracing, while highly inconvenient and sometimes impractical for certain patients, still has a role in specific circumstances. Formal analysis of the unstable prosthetic reconstruction is the key to successful treatment.

Precision planning with correct sizing and placement of components is critical to proper execution of total hip arthroplasty. While the desire to achieve excellent outcomes has always been a surgeon's goal, value-based care programs such as the Comprehensive Joint Replacement (CJR) program apportion real expenditures for the cost of treating complications such as fracture or dislocation to the participants. Such accountability accentuates the importance of optimizing the planning and execution of joint replacement surgery. Acetabular component sizing and placement in particular remains the single greatest challenge to surgeons. This is simply due to the fact that the requisite spatial information is not available to the surgeon during conventional surgery. Basing component placement on local anatomical landmarks without knowing the patient-specific nature of those landmarks ensures poor component placement in many cases. As a result, studies demonstrate that at least ½ of all acetabular components placed using conventional methods are malpositioned.

Potential solutions include the using of intra-operative radiographic analysis, traditional navigation and robotics. Unfortunately, measurements of plain radiographs have repeatedly been shown to be inaccurate due to lack of knowledge of and correction for beam center location, magnification, beam divergence, and position of the pelvis itself on the image. As a result, such quantification of unquantifiable images can systematically lead to poor decisions. Intra-operative radiograph measurement methods have been shown to lead to anteversion measurement errors as high as 27 degrees. Similarly, there is a perception that performing total hip arthroplasty through the anterior exposure can result in reliable cup positioning when fluoroscopy is used, but such procedures have also been shown to have a high incidence of cup malposition.

Image-free navigation, image-based navigation, and image-based robotics can potentially lead to accurate component placement. Adoption of these technologies, however, has been limited, possibly due to the increase in time of use, complexity, and cost of these systems. Robotic systems have also proven to be potentially hazardous and inaccurate in routine clinical use. A cloud-based, patient-specific hip surgery planning and smart-tool cup navigation system was developed to address the most common technical problems affecting hip arthroplasty (HipXpert System, Surgical Planning Associates, Boston, MA). The methodology provides the surgeon with a full 3D plan of the surgery including cup size, cup orientation, stem size, head length, femoral anteversion, and planned change in leg length and offset. The application controlling the plan allows the surgeon to instantly change the plan and shows the implants in both 3D and on multiplanar cross-sectional views. The associated smart tool is adjusted specifically for that patient and when docked, provides orientation information to the surgeon.

The system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases including by an independent study. This compares to a recent study of robotic methods that measured 88% for inclination and 84% for anteversion.

Cloud-based 3D planning combined with smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problems of acetabular component malorientation and provides critical pre-operative information including acetabular and femoral component sizes, planned femoral anteversion, and planned changes in leg length and offset of the surgery.

Introduction

Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. The current study assesses the validity of intraoperative assessment using a specialized software to analyze intraoperative radiographs.

INTRODUCTION

Evolving payment models create new opportunities for assessment of patient care based on total cost over a defined period of time. These models allow for analyses of economic data that was previously unavailable and well beyond our familiar studies which typically include length of stay, surgical complications, and post-operative clinical and radiographic assessments. In the United States, the new Federal program entitled TheBundled Payment for Care Initiative created new opportunities for the assessment of surgical interventions. The purpose of the reported study was to assess the total reimbursement for care as a function of surgical technique in primary total hip arthroplasty (THA).

Introduction

Navigation of acetabular component orientation is still not commonly performed despite repeated studies that show that more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned1. The current study uses postoperative CT to assess the accuracy of a smart mechanical navigation instrument system for cup alignment.

INTRODUCTION

Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago¹. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation by comparing the orientation of acetabular components revised due to recurrent instability and to a series of stable hip replacements.

BACKGROUND

Cup malpositioning remains a common cause of dislocation, wear, osteolysis, and revision. The concept of a “Safe Zone” for acetabular component orientation was introduced more than 35 years ago. The current study assesses CT studies of replaced hips to assess the concept of a safe zone for acetabular orientation.

Introduction

Studies show that cup malpositioning using conventional techniques occurs in 50 to 74% of cases defined. Assessment of the utility of improved methods of placing acetabular components depends upon the accuracy of the method of measuring component positioning postoperatively. The current study reports on our preliminary experience assessing the accuracy of EOS images and application specific software to assess cup orientation as compared to CT.

INTRODUCTION

Young patients (< 50 years old) have been reported to have a higher risk of revision following total hip arthroplasty (THA) than older patient cohorts, possibly to due higher activity, a higher incidence of deformity and greater probability of prior surgery. Ceramic-on-ceramic bearing surfaces have been proposed for use in young and active individuals due to their low wear, low risk of adverse biologic reaction, and long-term survivorship. We assessed the clinical results and long-term survivorship of uncemented ceramic-on-ceramic THA in a young patient population.

Introduction

Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. A recent study measuring cup orientation on conventional radiodiographs demonstrated an incidence of cup malpositioning of 50% according to the safe zone that they defined 1,2. A prior study of 105 conventionally placed cups using CT demonstrated a cup malpositioning incidence of 74%3. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT.

Acetabular component malalignment remains the single greatest root cause for revision THA with malposition of at least ½ of all acetabular components placed using conventional methods. The use of local anatomical landmarks has repeatedly proven to be unreliable due to individual variation of these structures. As a result, the use of such landmarks without knowledge of their three-dimensional orientation may actually be a major cause of component malpositioning. Traditional navigation and robotics can potentially lead to improved component placement but these technologies have not gained widespread use due to the increase in time of use, complexity, and cost of these systems. The alternative of placing the cup in the supine position, even with the use of arthroscopy, has been proven to have an incidence of inaccuracy equal or greater than that in the lateral position.

A smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment (HipXpert System, Surgical Planning Associates, Boston, MA). The system is based on a low dose, low cost CT study and a customised patient-specific surgery plan. The laterally-based system docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. The anteriorly-based system also docks on a patient-specific basis with one leg on the anterior ischium and one leg on each ASIS, either to skin or to bone.

The lateral system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases and an independent study showing accurate cup placement in 98% of cases for both anteversion and inclination. This compares to a recent study of robotic methods with 88% for inclination and 84% for anteversion.

Smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problem of acetabular component malorientation.

Hip joint preservation remains a preferred treatment option for hips with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity always leads to arthrosis if uncorrected. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement if present. Pre-operative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces. The earlier PAO series show 20 year survivorship of 81% and 65% in Tonnis Grade 0 and 1 hips.

Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Cam impingement can be treated by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of pre-operative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis pre-operatively whereas dysplastic hips can become symptomatic with instability in the absence of arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctable problems prior to the development of significant secondary arthrosis.

Properly designed ceramic-on-ceramic total hip arthroplasty has consistently shown excellent clinical outcomes without the problems associated with crosslinked polyethylene bearings such as liner dissociation, debris associated osteolysis, polyethylene fracture, clinically measurable wear, and taper-corrosion associated adverse tissue reaction when metal heads are used. The recognition of these results has been affected by the confusion with the poorer results of designs with elevated metal rims especially when coupled with the use of femoral components made of beta-titanium alloys. Our clinical experience, now at 18 years, with flush mounted liners and Ti-Al6-V4 stem and cup alloy demonstrate consistently excellent outcomes without osteolysis or ALTR. Ceramic-Ceramic THA remains the gold standard for the young active patient.

Background

Stratifying patients with Low Back Pain (LBP) using the STarT Back Tool and delivering targeted treatment has demonstrated efficacy in individual physiotherapy settings. Physiotherapy interventions for LBP patients are often delivered in groups. This study aimed to explore the sustainability and cost effectiveness of a group stratified intervention in primary care.

Several design principles were considered paramount when the surgical technique of performing total hip arthroplasty through an incision in the superior capsule without dislocation of the hip joint was developed. These design principles include: Preservation of the abductors; Preservation of the posterior capsule and short external rotators; Preparation of the femur in situ without dislocation of the hip; In-line access to the femoral shaft axis; Ability to perform a trial reduction; Independence from intraoperative imaging; Independence from a traction table; Applicable to at least 99% of THA procedures

Personal experience with more than 1950 THA using the superior capsulotomy technique over a 12-year period has demonstrated several observations: Dislocation rate of 0.15% (3 in 1950); Acute deep infection rate of 0% (0 in 1950); Universal applicability: used in 99.7% of primary THA; Lateral femoral cutaneous nerve palsy incidence: 0/1950; Femoral nerve palsy incidence: 0/1950; Transient peroneal palsy incidence: 2/1950; Length of stay (since 2010): 1.55 days; Discharge to home: 98%; 90-day cost (2/13 to 2/14) compared to other exposures in CMS patients in the same institution: $24,200 vs $30,100; Readmission costs (CMS 2/13 to 2/14) at 90 days: $0.

Conclusion: Performing total hip arthroplasty without dislocation and with preservation of the abductors, posterior capsule and short external rotations has proven to have a low dislocation rate, a low infection rate, and wide applicability. CMS 12-month expenditure data documenting ZERO dollars spent on readmission for any reason within 90 days of surgery demonstrates the potential for simultaneously improving incomes and reducing cost, with particular benefit within the CMS BPCI and private bundled payment programs.

Hip joint preservation remains a preferred treatment option for hips with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity always leads to arthrosis if uncorrected. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement if present. Preoperative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces.

Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Cam impingement can be treated by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of preoperative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis preop whereas dysplastic hips can become symptomic with instability in the absence of arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctible problems prior to the development of significant secondary arthrosis.

Acetabular component malalignment remains the single greatest root cause for revision THA with malposition of at least ½ of all acetabular components placed using conventional methods. The use of local anatomical landmarks has repeatedly proven to be unreliable due to individual variation of these structures. As a result, the use of such landmarks without knowledge of their three-dimensional orientation may actually be a major cause of component malpositioning. Traditional navigation and robotics can potentially lead to improved component placement but these technologies have not gained widespread use due to the increase in time of use, complexity, and cost of these systems. The alternative of placing the cup in the supine position, even with the use of arthroscopy, has been proven to have an incidence of inaccuracy equal or greater than that in the lateral position.

A smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment (HipXpert System, Surgical Planning Associates, Boston, MA). The system is based on a low dose, low cost CT study and a customised patient-specific surgery plan. The laterally-based system docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. The anteriorly-based system also docks on a patient-specific basis with one leg on the anterior ischium and one leg on each ASIS, either to skin or to bone.

The lateral system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases and an independent study showing accurate cup placement in 98% of cases. The newer anterior system has the potential for even greater accuracy.

Smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problem of acetabular component malorientation.

Surgical invention to preserve the native hip joint remains a preferred treatment option for hips in young patients with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The two most common pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity, if left uncorrected, always leads to arthrosis. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement, if present. Correction of deformities on the femoral side is now less common and reserved for only the more severe combined femoral and acetabular dysplasias or the rare isolated femoral dysplasia. Pre-operative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces.

Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Further, significant cam impingement is clearly associated with the development of osteoarthrosis. Treatment can be performed either by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of pre-operative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis pre-op whereas dysplastic hips can become symptomatic with the onset of instability in the absence of significant secondary arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Similarly, caution should be exercised when considering rim-trimming for protrusion since high central contact pressures due to an enlarged acetabular notch are not corrected by rim trimming.

Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctable problems prior to the development of significant secondary arthrosis.

While crosslinked polyethylene has reduced the rate of wear and osteolysis in THA, osteolysis still occurs and taper-corrosion induced wear has become recognised as an increasing problem especially when larger diameter metal bearings are used. Long-term follow up studies of newer polyethylene bearings continue to lag those of ceramic-on-ceramic bearings by several years.

Ceramic-on-ceramic (CoC) bearing surfaces have consistently demonstrated reliable clinical results with when coupled with appropriated designed femoral stems and acetabular shells and have been shown to exhibit virtually no risk of adverse biologic reaction. Further, CoC bearings have not been associated with corrosion-induced adverse tissue reactions that occur with metal taper junctions.

Revisions for squeaking have been associated with specific designs and materials, including the use of a titanium elevated metal rim on the acetabular side, and more flexible femoral components made of a beta-titanium alloy (TMZF) which had thin necks and relatively small tapers.

Multiple clinical studies document excellent long-term survival of CoC bearing couples in young patients with revision for any reason as the primary endpoint. Our own experience with 341 hips in patients under 50 with 2–15 years and average 9.1-year follow up demonstrates a 95% overall survivorship (revision for any reason) at 13 years.

CoC bearings continue to show excellent durability in young, high demand patients with an absence of osteolysis in any case. CoC bearings continue to represent an excellent alternative to bearing couples containing polyethylene.

Hip joint preservation remains a preferred treatment option for hips with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity, if left uncorrected, always leads to arthrosis. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement if present. Pre-operative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces.

Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Further, significant cam impingement is clearly associated with the development of osteoarthrosis. Treatment can be performed either by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of preoperative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis preop whereas dysplastic hips can become symptomatic with instability in the absence of arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Similarly, caution should be exercised when considering rim-trimming for protrusion since high central contact pressures due to an enlarged acetabular notch are not corrected by rim trimming.

Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctable problems prior to the development of significant secondary arthrosis.

Ceramic-on-ceramic (COC) bearing surfaces have consistently demonstrated reliable clinical results with when coupled with appropriated designed femoral stems and acetabular shells. Ceramic bearing surfaces are highly wettable and display both boundary and hydrodynamic fluid-film lubrication modes, which lead to extremely low wear rates. Furthermore, COC bearing couples have been shown to exhibit virtually no risk of adverse biologic reaction and have not been associated with corrosion-induced adverse tissue reactions that occur with metal taper junctions, particularly head-neck taper junctions. The relative brittleness of ceramics initially was thought to be a major disadvantage; however, four decades of improvement in the manufacture of ceramics and rigorous proof testing has led an extremely low risk of fracture, perhaps lower than that for cross-linked polyethylene. More recently it has become increasing appreciated that nearly all revisions for squeaking have been restricted to specific designs and materials, including the use of a titanium elevated metal rim on the acetabular side, and more flexible femoral components made of a beta-titanium alloy (TMZF) which had thin necks and relative small tapers. Multiple clinical studies document excellent long-term survival of COC bearing couples in young patients with revision for any reason as the primary endpoint. Our own experience with 341 hips with 2 to 15 and average 9.1 year f/u demonstrates a 95% overall survivorship (revision for any reason) at 13 years in patients under 50 years of age at the time of surgery.

By contrast, cross-linked polyethylene bearings have not been studied so carefully and have not been shown to be superior to ceramic-ceramic bearings in young patients. These bearing surfaces represent a very heterogeneous group of products, with varying degrees of cross-linking, post-irradiation processing methods, and additives. Cross-linked polyethylenes in general have a lower fatigue strength than conventional polyethylene and are prone to fracture, especially when thin material is subjected to high stress. Some types of cross-linked polyethylenes are prone to in vivo oxidation, leading to further mechanical compromise over time. Studies also demonstrate the absence of reduction in femoral head penetration or risk of osteolysis in heads 32mm and larger, which are commonly used today. The most recent cross-linked polyethylene products have the least clinical support for their use. The long-term biologic effects of the smaller HXLPE wear particles and newer additives, including the more recently added vitamin E compounds are unknown. Indeed, in vitro, the debris has been shown to be cytotoxic. There is a paucity of survivorship data for hips utilising HXLPE, especially in younger, more active individuals. For these reasons, we believe that the ceramic-ceramic bearings are the gold standard for THA in the young patient and that cross-linked polyethylene bearing are being continually changed and have little long term clinical outcomes data to support their use.

Introduction:

Cup malposition leads to increased incidences of dislocation, impingement, wear, and revision. The HipSextant navigation system is a smart mechanical navigation device designed to indicate correct cup orientation at surgery. The current study assesses the effect of deliberately mis-docking the device on clinical accuracy.

Introduction:

Wear, wear-associated osteolysis, and instability are the most common reasons for revision total hip arthroplasty. These failures have been shown to be associated with acetabular component malpositioning. However, optimal acetabular component orientation on a patient-specific basis is currently unknown. The current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips.

Introduction:

Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. A recent study measuring cup orientation on conventional radiodiographs demonstrated an incidence of cup malpositioning of 50% according to the safe zone that they defined^1,2. A prior study of 105 conventionally placed cups using CT demonstrated a cup malpositioning incidence of 74%³. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT.

Background:

While more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned, traditional surgical navigation and robotoics have not been widely adopted. This may be due to the additional time, expense, and complexity associated with this technology. As an alternative, smart mechanical navigation instruments, adjusted on a patient-specific basis, have been introduced to address the problem of cup malorientation. The current study assesses the accuracy of acetabular component alignment using a mechanical navigation instrument.

Introduction:

Conventional methods of aligning the acetabular component during hip arthroplasty and hip resurfacing often rely upon anatomic information available to the surgeon. Such anatomical information includes the transverse acetabular ligament and the locations of the pubis, ischium and ilium. The current study assesses the variation in orientation of the plane defined by the pubis, ischium and ilium on a patient-specific basis as measured by CT.

Introduction

Adverse Local Tissue Reactions (ALTR) have been reported in association with both wear and corrosion. Tissue reactions have been reported in association with corrosion at CoCr head-CoCr neck, CoCr head-TiAl6V4 neck, and CoCr modular neck on beta-titanium (TMZF) stem junctions. The current abstract reports on 3 cases of ALTR in association with CoCr modular necks on convention titanium (TiAl6V4) stem junctions.

Case 1. A 67 year old male (87 kg, 1.73 m, BMI 29.1) presented with new onset hip irritation 11 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 95, CRP = 5, Cr level = 1.0, Co level = 4.1, leukocyte transformation testing = highly reactive to nickel. Hip aspiration was culture negative with 11,250 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the greater trochanter.

Case 2. A 52 year old male (89 kg, 1.83 m, BMI 26.5) presented with new onset hip irritation 30 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 7, CRP = 5.4, Cr level = 2.1, Co level = 4.8, leukocyte transformation testing = reactive to nickel. Hip aspiration was culture negative with 3995 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas.

Case 3. A 52 year old male (104 kg, 1.85 m, BMI 30.1) presented with new onset hip irritation 26 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 33, CRP = 34.9, Cr level = 1.0, Co level = 3.7, leukocyte transformation testing = no reactivity to any of the biomaterials. Hip aspiration was culture negative with 3,780 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas.

Introduction:

Young patients have been reported to have a higher risk of revision following total hip arthroplasty (THA) than older cohorts, possibly to due higher activity and a higher incidence of deformity and prior surgery. Ceramic-on-ceramic bearing surfaces have been proposed for use in young and active individuals due to their low wear, low risk of adverse biologic reaction, and long-term survivorship. We assessed the clinical results and long-term survivorship of uncemented ceramic-on-ceramic THA in a young patient population.

Introduction

Conventional methods of aligning the acetabular component during hip arthroplasty and hip resurfacing often rely upon anatomic information available to the surgeon. Such anatomical information includes the transverse acetabular ligament and the locations of the pubis, ischium and ilium. The current study assesses the variation in orientation of the plane defined by the pubis, ischium and ilium on a patient-specific basis as measured by CT.

Introduction

The optimal acetabular component orientation in general or on a patient-specific basis is currently unknown. In order to answer this question, the current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips.

Introduction

Correct postoperative leg length restoration is among the most important goals of hip arthroplasty. Therefore, we developed, validated and clinically applied a novel software algorithm based on surgical navigation, which allows the surgeon to restore a defined femur position without establishing a femoral coordinate system or the hip joint center and measure the leg length accurately and simply.

Introduction

Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT.

Acetabular component malalignment remains the since greatest root cause for revision THA with malposition of at least ½ of all acetabular component placed using conventional methods1. The use of local anatomical landmarks has repeatedly proven to be an unreliable. The reason for this is that the position of local anatomical landmarks varies widely from one patient to another. Another alternative is to simply place acetabular components in a supine position. Unfortunately, cups placed in the supine position under fluoroscopy had the highest incidence of cup malposition in the Callanan study. This is because acetabular anteversion is critically important and pelvic tilt during surgery in the supine position is unknown, uncontrolled, and not correlated with post-operative pelvic tilt.

Image-free surgical navigation can be useful for cup alignment in the absence of pelvic deformity. Image-based surgical navigation can be effective for cup alignment in the presence or absence of pelvic deformity. Unfortunately, while these technologies have been available for a decade, few surgeons employ these technologies. This is likely due to added time, complexity, and expense. Current robotic technology embodies all of these limitations in an even more extreme form.

The HipSextant is a smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment. The system is image based (CT or MR) and can handle extreme asymmetry and deformity. The instrument docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. Since the planning is provided, the surgeon needs to only review and adjust the plan as desired. Further the system is robust, showing greater accuracy than image-based traditional navigation. Finally, the system takes typically only 3 minutes to use, making it practical for busy practices and hospitals.

Indications for removal of well-fixed cementless femoral components include infection, improper femoral height/offset/anteversion, and fracture. More recently, removal of well-fixed but recalled femoral components that are associated with adverse local tissue reaction (ALTR) has created a new indication for this procedure. The goal in all cases is to preserve bone stock and soft-tissue attachments to the greatest extent possible during implant removal. The strategy for implant removal depends to a large extent on the type of implant to be removed. Implants with limited proximal fixation can often be removed from the top using narrow osteotomes. Implants with more extensive fixation typically require more extensive exposure. When performing an extended trochanteric osteotomy, plan for the bone flap length based on measurement from the tip of the greater trochanter. Instead of devascularising the lateral bone flap, be sure to preserve the quadriceps attachment to the bone flap, exposing the lateral femur only where the transverse and posterior osteotomies are planned. The anterior osteotomy can be performed using a dotted line of osteotomes trans-muscularly as described by Heinz Wagner. Placement of a prophylactic cerclage below the osteotomy is prudent. Most importantly, if the need for a transfemoral exposure is likely, it should be performed primarily so that the posterior capsule and short rotators can be preserved. There is no need to perform a full posterior exposure and then to secondarily perform a transfemoral exposure since the former is unnecessary if the latter is performed. Discrete, limited fixation of the lateral bone flap proximally and distally should be performed to prevent strangulation of the living bone flap during the refixation process. The transfemoral technique can be applied not only to removal of well-fixed devices but also for conversion from hip fusion and for Z-shortening of the femur during Crowe 4 reconstruction instead of using a transverse osteotomy and intercalary shortening.

Distal neck modularity places a modular connection at a mechanically critical location. However, this is also the location that confers perhaps the greatest clinical utility. Assessment of femoral anteversion in 342 of our THR patients by CT showed a range from −24 to 61 degrees. The use of monoblock stems in some of these deformed femurs therefore must result in a failure to appropriately reconstruct the hip and have increased risks of impingement, instability, accelerated bearing wear or fracture, and adverse local tissue reaction (ATLR). However, the risks of failing to properly reconstruct the hip without neck modularity must be weighed against the additional risks introduced by neck modularity.

There are several critical design, material, and technique variables that are directly associated with higher or lower incidences of problems associated with modular neck femoral components. These include modular neck length, design and material of both parts including the junction design, wall thickness of the receiving junction, assembly force, and bearing diameter and material. With regard to stem design and material, it has been clearly shown that the incidence of titanium neck fractures is higher in stems with a thinner wall-thickness of the receiving junction than in stems with a thicker wall-thickness. Moreover, titanium necks have been largely replaced with CoCr necks with significantly higher yield and fatigue strength. It remains to be seen if the introduction of CoCr necks will decrease or increase the risks associated with distal neck modularity.

With respect to titanium necks, our experience has shown no adverse local tissue reaction, no fractures of short necks (0 of 370) and a 0.34% incidence of fractures in long necks (2/580) at 3 to 8 years following surgery. This lower incidence of neck fracture compared to other reports may relate to the relatively more rigid stem and thicker wall of the junction receiving the neck compared to other stems.

With respect to CoCr modular necks, one device that mated the CoCr modular neck with a beta-titanium alloy femoral component has been shown to have a high incidence of ALTR and has been recalled. While the CoCr on Conventional Titanium Alloy modular neck experience has had a statistically significantly lower incidence of problems, we believe that we have identified two cases of ALTR. If that is the case, the CoCr neck experience may well have a higher incidence of problems that the Ti neck experience.

In summary, placing a modular connection at the stem-neck junction has great clinical utility but this is a very design sensitive location. There are risks associated with the use of non-modular neck components that are incapable of properly reconstructing the spectrum of pathology that presents. This failure can lead to instability, impingement, and polyethylene fracture. Yet, the use of titanium modular necks has a small risk of component fracture while the use of cobalt-chrome modular necks may have a higher risk of adverse local tissue reaction. While the existence of a modular neck may offer great advantages at the time of primary reconstruction and of future revision, currently the risk/benefit for the use of these components is strongest in patients with more significant anatomical abnormalities or more complex revision settings.

Young patients have been reported to have a higher risk of revision following total hip arthroplasty than older cohorts. This was attributed to the higher activity level which led to increased wear, osteolysis, and component fracture. We prospectively assessed the clinical results, wear and osteolysis, the incidence of squeaking, and the survivorship of ceramic on ceramic THA in patients younger than 50 years (mean age of 42 [18–50] years). The series included 425 THAs in 370 patients with 368 hips followed for a minimum of 2 years (mean 7.1 years, range 2–14 years). All patients received uncemented acetabular components with flush-mounted acetabular liners using an 18 degree taper. No osteolysis was observed in any uncemented construct. There was osteolysis around one loose cemented femoral component. The survivorship for reoperation for implant revision was 96.7%. There were only two acetabular liner fractures (0.47%) and one femoral head fracture (0.24%). Two of the three fractures involved a fall from a significant height. There were no hip dislocations. Five patients (1.17%) noted rare or occasional squeaking. None had reproducible squeaking. In summary, the current study shows that ceramic-on-ceramic THAs in the young patient population are extremely reliable with a very low revision rate and an absence of wear-induced osteolysis. In addition, it shows that both bearing fracture in this young patient population typically occurs with polytrauma and squeaking issues that have been raised relative to ceramic bearings occur very rarely with the flush-mounted ceramic liner design used in this study.

Introduction

Early rehabilitation and discharge following minimally-invasive total hip arthroplasty has potential risks including the possibility that patients may become progressively anemic at home. The current study assess the use of pre-emptive autologous blood transfusion on the length of stay, readmission, and allogenous transfusion.

Introduction

Half of all acetabular components placed using conventional methods are malpositioned¹. The HipSextant™ Navigation System (Surgical Planning Associates, Boston, MA) is a mechanical navigation system, adjusted on a patient-specific basis, designed to achieve appropriate cup alignment as simply and rapidly as possible. The current study assesses the surgeon's ability to register and track the pelvis and align the cup using the system.

Introduction

The current study reports on the impact of immediate mobilization of patients treated by tissue-preserving, computer-assisted total hip arthroplasty on length of stay, disposition, and complications.

Introduction

The optimal goal for cup positioning in hip arthroplasty in individual patients is affected by many factors including surgical exposure, femoral anteversion, and pelvic tilt. Some navigation systems ignore pelvic tilt and are based strictly on the anterior pelvic plane while others incorporate pelvic tilt, as measured in the supine position on the operating table. Neither approach incorporates knowledge of preoperative spino-pelvic flexibility or predictions of the change in spino-pelvic attitude or flexibility following surgery. While prior studies have shown little change in pelvic tilt postoperatively, one recent study based on gait analysis, suggested that changes in pelvic tilt are not predictable. The current study aims to assess changes in pelvic tilt following surgery.

Acetabular component malpositioning is the most common reason for instability and wear resulting in revision total hip arthroplasty (THA). The current study aimed to assess a novel mechanical navigation device which was designed to simply and efficiently indicate appropriate cup orientation during surgery. The accuracy was compared to a series of hip arthroplasties performed using CT-based computer-assisted cup placement.

The study group consisted of 70 THAs performed using the mechanical device. The control group consisted of 146 THAs performed using CT-based computer navigation. Postoperative cup positioning was measured using a validated 2D/3D-matching method. An outlier was defined outside a range of ± 10 degrees from the planned inclination or anteversion.

In the study group the mean accuracy for inclination was 1.3 ± 3.4 (-6.6 – 8.2) and 1.0 ± 4.1 (-8.8 – 9.5) for anteversion with no outliers for either parameter. In the control group the accuracy for anteversion (3.0 ± 5.8 [-11.8 - 19.6]; p=0.6%) and the percentage of outliers (6.8%; p=3.3%) differed significantly. The accuracy for inclination (3.5 ± 4.1 [-12.7 - 9.5]; p=21.4%) and the percentage of ouliers (4.8%; p=9.9%) did not differ significantly.

The use of this mechanical navigation device can result in similar accuracy of acetabular cup orientation compared with CT-based surgical navigation. All cups were placed within a zone of ± 10 degree range of inclination and anteversion. This mechanical navigation device allows accurate cup navigation with minimal additional time and equipment.

Introduction

The use of less invasive techniques for total hip arthroplasty (THA) has remained controversial with some studies showing a higher incidence of complications. The technique of performing total hip arthroplasty through a superior capsulotomy was developed to maximally preserve the soft tissue envelope surrounding the hip. The current study assesses the recovery and complications of hips replaced using conventional and tissue preserving techniques.

Total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH) has been associated with increased rates of complications and revision. Hip instability and wear-induced osteolysis are among the more common and serious of these problems. The current investigation prospectively assessed the survivorship and clinical results of patients with DDH treated by alumina ceramic-ceramic THA.

We investigated 161 consecutive hips in 145 patients with DDH classified as Crowe type I (131 hips, 81%), II (26 hips, 16%), III (2 hips, 1%), and IV (2 hips, 1%). All patients had an uncemented titanium acetabular component with a flush mounted alumina ceramic-ceramic bearing. The mean age at operation was 48.0 ± 12.2 years (range, 18 – 79 years). The preoperative Merle d'Aubigné score was 11.4 ± 1.7 (6 – 15). 27 hips (17%) had at least one previous surgical procedure. 92 hips (57%) were replaced with the use of surgical navigation for acetabular component positioning. The mean cup diameter was 49.9 ± 3.4 mm (46 – 60 mm). 88 (55%) bearings were 28mm and 73 (45%) bearings were 32mm.

At a mean follow-up of 6.1 ± 2.5 years (2 – 11.3 years), the mean Merle d'Aubigné score was 17.4 ± 0.9 (14 – 18). There were no cases of osteolysis or dislocation. There was one reoperation of an early displaced cup. In addition, there was one calcar crack that was cerclaged, one intraoperative trochanteric fracture also repaired at surgery. No patient complained of squeaking. 94 patients with 100 hips (61%) completed a questionnaire specifically asking for squeaking. None of these patients reported squeaking. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 99.4% (95% confidence interval 98.2-100%).

Results of ceramic-ceramic THA in young patients with low to middle graded DDH after two to eleven years follow-up are promising with no radiographic signs of osteolysis or dislocation.

While alumina ceramic-ceramic THA has been performed in the US for more than 12 years, the phenomenon of frequent, clinically reproducible squeaking is relatively new. The current study investigates the influence of implant design on the incidence of squeaking.

We reviewed implant information on 1275 consecutive revision THAs performed from 10/2002 through 10/2007 to identify any patients who had complained of squeaking or grinding. We also identified, 2778 consecutive primary ceramicceramic THA. Of these, we reviewed the clinical records of 1,039 patients (37%) to date. Any patient complaint of squeaking or grinding at the time of an office visit or by phone interview was recorded. Hips were divided into group 1: flush mounted ceramic liner; group 2a: recessed ceramic liner mated with a stem made of TiAlV and using a 12/14 neck taper; and group 2b: recessed ceramic liner mated with a stem made of a beta titanium alloy comprised of 12% molybdenum, 6% Zirconium, and 2% Iron and using a neck taper smaller than a 12/14 taper.

Of the revision THAs, 5 hips (0.4%) were in patients who had complained of squeaking or grinding. All 5 hips had a recessed, metal-backed ceramic liner and evidence of metallosis. In primary THAs, Group 2b had statistically significantly (p=0.04) more squeaking (7.6%) than group 2a (3.2%) which had statistically significantly (p=0.002) more squeaking than group 1 (0.6%).

Squeaking following ceramic-ceramic THA is associated with use of a recessed metal-backed ceramic liner in combination with a femoral component made of a betatitanium alloy and using a relatively small head-neck taper. Since all revised hips in our study had metallosis, it is possible that metal debris is adversely affecting the bearing and that the elevated metal rim combined with a small head neck taper and the beta-titanium alloy contribute to this problem. Use of bearings with a flush-mounted ceramic liner mated with femoral components made of TiAlV and using a 12/14 taper appears to be prudent.

Patients who are less than 50 years old at the time of total hip arthroplasty (THA) have been known to have higher failure rates than patients who are older. Wearinduced osteolysis and associated component loosening is the most common mode of failure reported. The current investigation prospectively assessed the survivorship and clinical results of alumina ceramic-ceramic THA in patients younger than 50 years.

238 consecutive hips in 201 patients treated by alumina ceramic-ceramic THA were studied. The mean age at operation was 41.4 ± 7.5 years (range, 18 – 50 years).

The preoperative Merle d’Aubigné score was 11.1 ± 1.6 (6 – 15). The preoperative diagnosis included primary osteoarthritis or impingement (105 hips, 44%), developmental dysplasia of the hip (90 hips, 38%), osteonecrosis of the femoral head (17 hips, 7%), post-traumatic osteoarthrosis (16 hips, 7%), and rheumatoid arthritis (6 hip, 3%). 144 hips (61%) were replaced with the use of surgical navigation for acetabular component positioning. The mean cup diameter was 51.8 ± 3.7 (range, 46 – 60 mm). 73 (31%) bearings were 28 mm and 165 (69%) bearings were 32 mm.

At mean follow-up of 5.6 ± 2.3 years (2 – 11 years), the mean Merle d’Aubigné score was 17.4 ± 0.9 (14 – 18). There were no radiographic signs of osteolysis. There were two revisions (0.8%): one for acute cup displacement and one for a ceramic liner fracture. In addition, one hip was treated by I& D for acute infection and another with I& D but without evidence of infection. Other complications included one greater trochanter fracture and one calcar fracture, both repaired at surgery, and one transient peroneal nerve palsy. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 98.7% (95% confidence interval 96.3–100%). There were no hip dislocations.

Results of THA in patients less than 50 years using alumina ceramic-ceramic bearings at two to eleven years follow-up are promising with no case of osteolysis or dislocation.

Introduction: Malposition of the pelvis at the time of acetabular component insertion can contribute to malpositioning of the acetabular component. This study measures the variation in intraoperative positioning of the pelvis on the operating table during surgery by matching intraoperative radiographs with pre-operative computed tomograms (CT) using 2D-3D matching.

Methods: This prospective study was comprised of a random sample of 45 patients (n = 45, 26 female, 19 male) who had received a total hip arthroplasty (THA) from a single surgeon from 10/21/2003 to 9/6/2007. No THA candidate was excluded for any reason, including body habitus (mean BMI = 27.7, range 17.5 – 42.3), underlying disease process, age (mean age at surgery = 57, range 27 – 80), sex or side of surgery (21 left THAs, 24 right THAs). According to our standard clinical treatment protocol, each patient had a pre-operative CT scan for CT-based surgical navigation of the hip arthroplasty and each patient had an intraoperative radiograph taken to assess component positioning. All THAs were performed in the lateral decubitus position on a radiolucent peg-board positioning device. Each patient’s intraoperative pelvic radiograph was taken after acetabular component and trial femoral component insertion with the leg placed in a neutral position on the operating table and with the xray plate aligned squarely with the operating table. The orientation of the pelvis on the operating table was calculated by comparing the intraoperative 2D projection to the 3D CT dataset using software that can perform 2D-3D matching (XAlign). This software has been validated previously. By matching the 3D CT dataset to the magnification and orientation of the plain radiograph, the position of the anterior pelvic plane relative to the operating table could be calculated.

Results: The mean pelvic tilt (rotation around the medial-lateral axis) was 6.84 degrees of anterior pelvic tilt (lordosis) with a standard deviation of 7.95 degrees and a range from 27.24 degrees of lordosis to 4.96 degrees of kyphosis. The mean pelvic obliquity (rotation around the longitudinal axis) was 2.89 degrees anterior from neutral with a standard deviation of 9.44 degrees and a range from 29.36 anterior to 16.59 posterior from neutral. The mean pelvic rotation (rotation around the anterior-posterior axis) was 2.56 degrees cephelad, with a standard deviation of 4.10 degrees and a range from 10.88 degrees cephalad to 5.97 degrees caudad. Pearson correlation statistics showed no relation among pelvic position and body mass index or age. A correlation was seen between pelvic obliquity and pelvic rotation.

Conclusion: This study shows a high variability of intraoperative pelvic positioning in the clinical setting using accurate measurement tools. The greatest variation was seen in pelvic obliquity which has the greatest influence on anteversion/retroversion of the acetabular component. Additionally, pelvic obliquity and rotation appear related in our series. Since all of our intraoperative radiographs were taken with the leg in a neutral position, it is likely that the pelvis is even more greatly malpositioned at other times during the surgery when forces applied by retractors or upon the leg may be greater.

Acetabular component malpositioning increases the risk of impingement, dislocation, and wear. The goal of computer-assisted techniques is to improve the accuracy of component positioning, in particular optimizing the orientation of the acetabular cup.

The goal of the current study was to measure accuracy of cup placement in a large clinical series of hips that underwent CT-based computer-assisted THA.

146 hips in 140 patients underwent CT-based computer-assisted THA between 2006 and 2008. In all cases cup orientation was planned according to the individual preoperative CT and the anterior pelvic plane with an inclination of 41° and anteversion of 30°. For the procedure, all patients were placed in the lateral position and the cup was implanted using angled instruments. Intra-operatively all cases were navigated using an optoelec-tronic camera and tracked instruments (Vector Vision prototype, BrainLab, Germany).

Post-operatively, cup orientation was measured using a previously validated technique of 2D/3D-matching using the preoperative CT and post-operative radiographs. This technique allows for accurate measurement of cup position from plain radiographs corrected for individual pelvic orientation.

The mean accuracy for inclination was −2.5° ± 4.0° (−12° – 10°) and for anteversion it was 0.7° ± 5.3° (−11° – 15°). In 2 hips (1.4%) a deviation of more then 10° in inclination and in 4 hips (2.7%) a deviation of more then 10° in anteversion were found.

The current study demonstrates that the acetabular component can routinely be implanted with the assistance of CT-based navigation with reasonable agreement between the navigation measurements of component orientation at the time of surgery. Nonetheless, outliers still occasionally occur. These might be due to unrecognized loosening of the pelvic reference base, inaccurate registration or the use of the ipsilateral surface-based registration algorithms which rely heavily on points near the center of rotation of the hip.

Alumina ceramic-ceramic bearings have the benefit of very low wear and studies showing the complete absence of osteolysis during the first decade of close study. However, good results depend on several critical factors including surgical exposure, surgical technique, component placement, and choice of component design. The following abstract discusses our experience with several of these factors.

Initially, there were concerns that the use of ceramic-ceramic bearings would lead to a higher incidence of hip dislocation since the bearings have fewer femoral head-length choices and the absence of lipped-liners. In our prospective study of 418 hips the incidence of hip dislocation at 1 to 10 year followup is 0.5% (2/418). This experience suggests that the use of alumina ceramic-ceramic bearings is not associated with an increased incidence of dislocation.

More recently, concerns about squeaking of alumina ceramic-ceramic bearings have been reported, particularly from centers in the United States. To investigate this issue, we reviewed information on 1275 consecutive revision THAs and 1039 consecutive primary ceramic-ceramic THA that had been performed at two institutions between 1996 and 2007. To identify the influence of the implant design on the incidence of squeaking we divided the primary hips into three groups with group 1: flush mounted ceramic liner; group 2a: recessed ceramic liner mated with a stem made of TiAlV; and group 2b: recessed ceramic liner mated with a stem made of a beta titanium alloy comprised of 12% molybdenum, 6% Zirconium, and 2% Iron.

Analysis of the 1275 revision hips revealed 5 alumina ceramic-ceramic hips in patients who complained of squeaking or grinding. All 5 hips were designs that included a ceramic liner that was recessed inside of an elevated metal rim. All 5 hips also demonstrated metallosis at the time of revision.

In primary THA, Group 2b had statistically significantly more squeaking (9 of 118) than group 2a (10 of 321) which had statistically significantly more squeaking than group 1 (6 of 700). In addition, the severity of squeaking between the groups was qualitatively different. Patients in Group 2b who complained of squeaking would often experience squeaking frequently throughout the day and could be demonstrated in the physician’s office. By contrast, patients in Group 1 who noted squeaking stated that the hip squeaked once a day to once a year. No patient in Group 1 complained of frequent squeaking or could demonstrate squeaking in the physicians’ office. Further, joint fluid analysis from a patient in Group 2b who complained of squeaking revealed metal from both the femoral (Molybdenum) and acetabular (Aluminum) components.

As reported in another abstract at this meeting, 10 year survivorship of flush-mounted alumina ceramic-ceramic THA is 98.4% (95% confidence interval 97.1–100%) and no patient in that prospective clinical studies demonstrated radiographic evidence of osteolysis or wear.

These experiences demonstrate that THA using alumina ceramic-ceramic is extremely reliable with low revision and dislocation rates and an absence of osteolysis. Significant squeaking is not associated with flush-mounted alumina ceramic liners and is clearly associated with elevated metal rims and metallosis. Finally, squeaking is statistically significantly associated with femoral components made of a beta titanium alloy consisting of Titanium, Molybdenum, Aluminum, and Iron.

The long-term result of a total hip arthroplasty (THA) strongly depends on the correct component positioning of the acetabular cup and stem. To measure cup orientation out of a postoperative anteroposterior (AP) pelvic radiograph is highly inaccurate due to the wide variation of individual pelvic tilt and rotation. The goal of this study was to develop and validate a 2D-3D matching software (HipMatch) that allows matching a postoperative AP pelvic radiograph with a preoperative CT to accurately measure cup orientation corrected for individual pelvic orientation.

The software is based on a spline-based multi-resolution 2D-3D image registration algorithm and a Markov random field theory based on similarity measurement. Based on a cone projection (imitating the path of the x-rays), the software is able to match the three-dimensional CT-based data set with the contours of the projected pelvis on the AP pelvic radiograph. This gives the possibility to correct the measured cup orientation (inclination and anteversion) by measuring it according to an anatomical defined coordinate system (anterior pelvic plane). The validation of the software consisted of accuracy, reproducibility and observer reliability measurements using cadaver and clinical data. For the cadaver validation 10 human pelves (20 hips) were used. From each pelvis 2 CT scans, one with and one without an inserted cup were acquired. The CT scan with the cup was used as the ground truth. With the cup inserted 4 AP pelvic radiographs with the pelvis in an unknown arbitrary position during acquisition were performed resulting in 80 measurements for accuracy. These measurements were performed by 2 observers at 2 different occasions resulting in a total of 320 measurements for reproducibility and observer reliability. The intraclass correlation coefficient (ICC) was used for quantification of reproducibility and observer reliability and the Bland-Altman analysis was used to detect systemic errors. The clinical validation included 33 patients with a pre- and a postoperative CT and 49 patients with only a postoperative CT in addition to the postoperative radiographs. In the cases with only a postoperative CT, for the 2D-3D matching the postoperative CT after manual excision of the cup from the CT slice sticks was used. In all cases the postoperative CT was used as the ground truth. For each patient all the available postoperative radiographs were used resulting in 236 measurements of accuracy.

In the cadaver validation the cup orientation ranged from 34° – 57° for the inclination and from 1° – 24° for the anteversion measured on the CT. The accuracy showed a mean difference for the inclination of 0.9° ± 1.6° (−3.2° – 4.0°) and of 1.2 ± 2.4° (−5.3° – 5.6°) for the anteversion. The ICC for the reproducibility ranged from 0.96 to 0.99 and for the interobserver reliability from 0.95 to 0.98. No relevant systematic error was detected. In the clinical validation the cup orientation measured on the postoperative CT ranged for the inclination from 22° – 57° and for the anteversion from 7° – 35°. In the clinical setup the accuracy showed a mean difference for inclination of 1.8° ± 1.6° (−4.0° – 5.3°) and of −1.1° ± 2.9° (−5.9° – 5.7°) for the anteversion.

The 2D-3D matching technique showed a good accuracy and a very good reproducibility and observer reliability. This technique allows to measure the exact cup orientation out of an AP pelvic radiograph with the help of a preoperative CT and to correct the parameters for the individual pelvic position. Therefore this software is a powerful tool to measure accuracy of CT-based computer-assisted cup placement in a large clinical series.

Traditional total hip arthroplasty (THA) using metal-on-polyethylene bearings has been established as a reliable procedure but wear and wear debris-associated osteolysis are among the most frequent reasons for revision. Ceramic-ceramic bearings represent an alternative for THA with improved wear characteristics and low biological reactivity of wear particles. We investigated the clinical outcome of alumina ceramic-ceramic THA in a series of more than 400 THAs.

A total 418 alumina ceramic-ceramic THAs performed in 360 patients treated between 1997 and 2007 were studied prospectively. All patients had an uncemented titanium acetabular component with a flush mounted alumina ceramic-ceramic bearing (Wright Medical Technology, Inc. and Ceramtec AG). The mean age at operation was 51.7 ± 12.3 years (range, 18 – 79 years). 47 cases (11%) had previous hip surgery. The indication for surgery included primary osteoarthritis or impingement (58%), developmental dysplasia of the hip (32%), osteonecrosis of the femoral head (5%), post-traumatic osteoarthrosis (2%), and other indications (3%). In 202 (48%) a minimally invasive approach, the superior capsulotomy, was used with the help of the surgical navigation for acetabular component placement.

There were no cases of osteolysis or wear. We found 7 (1.1%) implant revisions: 1 acute cup displacement, 1 acetabular liner fracture, 1 case with failure of osseointegration of the cup, and 4 trochanteric wafer nonunions. A dislocation of the hip was found in 2 (0.5%) cases. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 98.4% (95% confidence interval 97.1–100%).

The results of alumina ceramic-ceramic THA after one to ten years are promising, especially considering the young age and high incidence of previous surgery in this patient population. The data are especially encouraging since no hip has demonstrated osteolysis. In particular, we are not aware of any other bearing that has shown an absence of lysis and 10 years follow-up. Since many of these patients are quite young, we await further assessment at 15 and 20 years.

INTRODUCTION: Malposition of the pelvis at the time of acetabular component insertion can contribute to malpositioning of the acetabular component. This study measures the variation in intraoperative positioning of the pelvis on the operating table during surgery by matching intraoperative radiographs with pre-operative computed tomograms (CT) using 2D-3D matching.

METHODS: This prospective study was comprised of a random sample of 45 patients (n = 45, 26 female, 19 male) who had received a total hip arthroplasty (THA) from a single surgeon from 10/21/2003 to 9/6/2007. No THA candidate was excluded for any reason, including body habitus (mean BMI = 27.7, range 17.5 – 42.3), underlying disease process, age (mean age at surgery = 57, range 27 – 80), sex or side of surgery (21 left THAs, 24 right THAs). According to our standard clinical treatment protocol, each patient had a pre-operative CT scan for CT-based surgical navigation of the hip arthroplasty and each patient had an intraoperative radiograph taken to assess component positioning. All THAs were performed in the lateral decubitus position on a radiolucent peg-board positioning device. Each patient’s intraoperative pelvic radiograph was taken after acetabular component and trial femoral component insertion with the leg placed in a neutral position on the operating table and with the xray plate aligned squarely with the operating table. The orientation of the pelvis on the operating table was calculated by comparing the intraoperative 2D projection to the 3D CT data-set using software that can perform 2D-3D matching (XAlign). This software has been validated previously. By matching the 3D CT dataset to the magnification and orientation of the plain radiograph, the position of the anterior pelvic plane relative to the operating table could be calculated.

RESULTS: The mean pelvic tilt (rotation around the medial-lateral axis) was 6.84 degrees of anterior pelvic tilt (lordosis) with a standard deviation of 7.95 degrees and a range from 27.24 degrees of lordosis to 4.96 degrees of kyphosis. The mean pelvic obliquity (rotation around the longitudinal axis) was 2.89 degrees anterior from neutral with a standard deviation of 9.44 degrees and a range from 29.36 anterior to 16.59 posterior from neutral. The mean pelvic rotation (rotation around the anterior-posterior axis) was 2.56 degrees cephelad, with a standard deviation of 4.10 degrees and a range from 10.88 degrees cephalad to 5.97 degrees caudad. Pearson correlation statistics showed no relation among pelvic position and body mass index or age. A correlation was seen between pelvic obliquity and pelvic rotation.

CONCLUSION: This study shows a high variability of intraoperative pelvic positioning in the clinical setting using accurate measurement tools. The greatest variation was seen in pelvic obliquity which has the greatest influence on anteversion/retroversion of the acetabular component. Additionally, pelvic obliquity and rotation appear related in our series. Since all of our intraoperative radiographs were taken with the leg in a neutral position, it is likely that the pelvis is even more greatly malpositioned at other times during the surgery when forces applied by retractors or upon the leg may be greater.

Total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH) has been associated with increased rates of complications and revision. Hip instability and wear-induced osteolysis are among the more common and serious of these problems. The current investigation prospectively assessed the clinical results and the survivorship of patients with DDH treated by alumina ceramic-ceramic THA.

We investigated 164 consecutive hips in 147 patients with DDH. Twenty-five hips (15%) had prior surgery to improve acetabular coverage, 108 hips (66%) were classified as Crowe type I, 21 (13%) as type II, and 10 (6%) as type III. All patients had an uncemented titanium acetabular component with a flush mounted alumina ceramic-ceramic bearing and were treated between 1997 and 2006. The mean age at operation was 48.5 ± 12.2 years (range, 18–75 years). The preoperative Merle d’Aubigné score was 11.3 ± 1.6 (6–15). Ninety-four hips (57%) were replaced with the use of surgical navigation for acetabular component positioning. The mean cup diameter was 51.2 ± 3.9 mm (46–60 mm). Seventy-seven (47%) bearings were 28mm and 87 (53%) bearings were 32mm.

At a mean follow-up of 4.5 ± 2.3 years (2–10 years), the mean Merle d’Aubigné score was 17.5 ± 1.2 (14–18). There were no cases of osteolysis or dislocation. There was one reoperation of an early displaced cup. In addition, there was one calcar crack that was cerclaged, one intraoperative trochanteric fracture also repaired at surgery. No patient complained of squeaking. Ninety-four patients with 100 hips (61%) completed a questionnaire specifically concerning squeaking. None of these patients reported on squeaking either. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 99.1% (95% confidence interval 98.0–100%).

Results of ceramic-ceramic THA in young patients with low to middle graded DDH after two to ten year follow-up are promising with no radiographic signs of osteolysis or dislocation.

Common problems following total knee arthroplasty include tibial component malpositioning, ligament imbalance, and clinical and subclinical fat embolism associated with intramedullary alignment guides. Tibial component malaligment can lead to component loosening. Ligament imbalance can lead to dysfunction and the need for revision. Fat embolism had been shown to occur in 46% of unilateral and 65% of bilateral total knee arthroplasty patients with neurological sequelae in 2 and 4% of patients respectively (Kim YH, J. Arth. 1999). All three of these common problems can be addressed with the use of surgical navigation.

Instruments designed for the Genesis II total knee arthroplasty (Smith-Nephew, Memphis, TN) are tracked optically using the ION virtual fluoroscopy surgical navigation system (Medtronics SNT, Louisville, CO). A software system specifically designed for TKR navigation is employed. Following exposure, reference frames are attached to the femur and tibia and fluoroscopic images of the knee are obtained. Hip and Ankle centres can be determined either kinematically or with images. Proper alignment and component rotation is determined using navigation without intramedullary alignment guides. Proper implant sizing is determined before the cuts are made by superimposing images of the proposed implants into the fluoroscopic images of the knee. Motion and ligament integrity can be quantified kinematically. The system was used to perform total knee arthroplasty on 14 cadavers. Post-operative alignment was measured radiographically.

As compared to the mechanical axis measured radiographically, the coronal femoral alignment measured 0.03 degrees of valgus (95% confidence:−1.81 to 1.88 degrees). Coronal tibial aligment measured 0.88 degrees of valgus (95% confidence: −2.17 to 0.41 degrees). Sagittal tibial aligment measured 1.81 degrees of posterior slope (95% confidence: −0.14 to 3.76 degrees)

The use of surgical navigation for TKA results in appropriately aligned implants. Surgical navigation has the potential to improve many of the most common problems encountered during and following total knee arthroplasty including component malaligment and malsizing, malrotation, ligament imbalance, and fat embolism.

Acetabular component malposition is the cause of half of all cases of recurrent hip dislocation. Intraoperative xrays after component insertion are helpful, yet it is certainly more useful to know the exact component position before final component insertion. The current study reviews results of acetabular component positioning using surgical navigation.

A prospective study of acetabular component positioning using surgical navigation was conducted in 22 hips of 21 patients. The technique involves insertion of a dynamic reference frame onto the pelvis during the surgical exposure and the acquisition of AP fluoroscopic views of each hip. Using the Fluoronav software and the ION surgical navigation system (Medtronics, Louisville, Colorado) a virtual horizontal line was then drawn between the teardrops. Acetabular component abduction was then aimed for 41 degrees. Component abduction was measured intra-operatively during component insertion by measuring the angle between the acetabular insertion handle and the virtual horizontal line between the teardrops. Post-operative xrays were analyzed for acetabular component abduction angle.

Using surgical navigation and aiming for 41 degrees of abduction resulted in post-operative cup positions averaging 40.8 degrees (range 37 to 44 degrees). These results show dramatically improved accuracy as compared to 85 acetabular component inserted without navigation showing a mean abduction of 42.8 degrees but with a range of 25 to 59 degrees. Frame placement and image acquisition required about 10 minutes. All intra-operative imaging after component insertion in complex cases was unnecessary. Having the dynamic reference frame in place also allowed assessment of pelvic position during surgery. Pelvic orientation varied greatly between patients on the operating table from about 12 degrees abducted to 12 degrees adducted. Further, pelvic orientation varied during surgery.

Surgical navigation allows extremely accurate positioning of the acetabular component at the time of total hip replacement surgery with an accuracy far greater than any study of acetabular component positioning reported in the literature. The pelvis is typically not orthogonal to the operating table during total hip arthroplasty and its position varies widely between patients and in the same patient during the procedure. Since acetabular component malposition represents the cause of half of all cases of recurrent dislocation, surgical navigation has been shown to directly address and potentially eliminate the problem of acetabular component malposition.

We report our early Boston experience with the technique of Ganz, et al., for surgical dislocation of the hip, which provides a safe, powerful approach to certain major intraarticular hip problems.

Materials and Methods: Forty-seven hips with various mechanical disorders have been treated using the Ganz technique of trochanteric flip osteotomy and anterior dislocation (JBJS 83-B: 1119-1124, 2001). Diagnoses include slipped epiphysis 14, Perthes 12, aspherical head/ anterior offset 12, dysplasia 14, multiple exostoses 2, other 3.Seven patients had simultaneous femoral oste-otomies; four had subcapital osteotomies for epiphys-iolysis. All patients had pain and limitation of motion preoperatively, and more than fifty percent had severe deformity and/or some arthrosis. Follow-up was six months to five years. Ages at surgery were eight to forty-eight years (mean twenty years).

Results: The variety of pathologies render objective analysis difficult, though all patients reported greatly reduced pain and increased motion post operatively. Only five patients were totally pain free and had objectively totally normal hips. No patient felt unimproved. No patient had radiographic signs of osteonecrosis.

Conclusion: Paralleling the Bernese experience of more than eight hundred cases, we find the Bernese technique of surgical dislocation to be a safe, effective tool for treating intra-articular hip pathology, increasing treatment possibilities for hip joint preservation. We anticipate greatly expanding its use in the future.