Aims

Refobacin Bone Cement R and Palacos R + G bone cement were introduced to replace the original cement Refobacin Palacos R in 2005. Both cements were assumed to behave in a biomechanically similar fashion to the original cement. The primary aim of this study was to compare the migration of a polished triple-tapered femoral stem fixed with either Refobacin Bone Cement R or Palacos R + G bone cement. Repeated radiostereometric analysis was used to measure migration of the femoral head centre. The secondary aims were evaluation of cement mantle, stem positioning, and patient-reported outcome measures.

Aims

In metal-on-polyethylene (MoP) total hip arthroplasty (THA), large metal femoral heads have been used to increase stability and reduce the risk of dislocation. The increased size of the femoral head can, however, lead to increased taper corrosion, with the release of metal ions and adverse reactions. The aim of this study was to investigate the relationship between the size of the femoral head and the levels of metal ions in the blood in these patients.

In metal-on-polyethylene (MoP) THA large femoral metal heads are designed to increase stability and to reduce dislocation risk. The increased head size could lead to increased taper corrosion with the release of metal ions and adverse reactions. Using blood ion measurements, we aimed to investigate the association between femoral head size and metal-ion release after MoP THA.

96 patients were enrolled at two centers and randomized to receive either a 32-mm metal head or a 36–44 mm metal head (the largest possible fitting the thinnest available polyethylene insert). Blood metal ions and PROMs (OHS, UCLA) were measured at two- and five-year follow-ups.

Both 2- and 5-year median chrome, cobalt, and titanium levels were below taper corrosion indicative ion levels. At 5 years, median chrome, cobalt, and titanium levels were 0.5 μg/L (0.50–0.62), 0.24 μg/L (0.18–0.30), and 1.16 μg/L (1.0–1.68) for the 32-mm group, and 0.5 μg/L (0.5–0.54), 0.23 μg/L (0.17–0.39), and 1.30 μg/L (1–2.05) for the 36–44 mm group, with no difference between groups (p=0.825, p=1.000, p=0.558). At 2 years, 7 (32-mm) versus 4 (36–44-mm) patients had elevated ions. At 5 years, 6 (32-mm) versus 7 (36–44-mm) patients had elevated ions. There was no difference in either OHS (p=0.665) or UCLA (p=0.831) between patients with or without elevated blood metal ions.

5 years after the insertion of MoP THAs, we found no differences in the blood metal ion levels between 32 mm heads and 36–44 mm heads and no corrosion-related revisions. As taper corrosion can debut after 5 years, there is still a need for long-term follow-up studies on the association between head size and corrosion in MoP THA.

Periprosthetic joint infections (PJI) are challenging complications following arthroplasty. Staphylococci are a frequent cause of PJI and known biofilm producers.

Reoperations for PJI of the hip or knee between 2012 and 2015 performed at Sahlgrenska University Hospital were identified. Medical records were reviewed, and clinical parameters recorded for patients whose intraoperative bacterial isolates had been stored at the clinical laboratory. Staphylococcal strains isolated from reoperations due to first-time PJI were characterised by their ability to form biofilms using the microtiter plate test.

The study group included 49 patients (70 bacterial strains) from first-time PJI, whereof 24 (49%) patients had recurrent infection. Strong biofilm production was significantly associated with recurrent infection. Patients infected with strong biofilm producers had a five-fold increased risk for recurrent infection.

Strong biofilm production was significantly associated with increased antimicrobial resistance and PJI recurrence. This underscores the importance of determining biofilm production and susceptibility as part of routine diagnostics in PJI. Strong staphylococcal biofilm production may have implications on therapeutic choices and suggest more extensive surgery. Furthermore, despite the increased biofilm resistance to rifampicin, results from this study support its use in staphylococcal PJI.

Aims

We aimed to investigate if the use of the largest possible cobalt-chromium head articulating with polyethylene acetabular inserts would increase the in vivo wear rate in total hip arthroplasty.

Aims

The most frequent indication for revision surgery in total hip arthroplasty (THA) is aseptic loosening. Aseptic loosening is associated with polyethylene liner wear, and wear may be reduced by using vitamin E-doped liners. The primary objective of this study was to compare proximal femoral head penetration into the liner between a) two cross-linked polyethylene (XLPE) liners (vitamin E-doped (vE-PE)) versus standard XLPE liners, and b) two modular femoral head diameters (32 mm and 36 mm).

Aims

The primary aim of this paper was to outline the processes involved in building the Partners Arthroplasty Registry (PAR), established in April 2016 to capture baseline and outcome data for patients undergoing arthroplasty in a regional healthcare system. A secondary aim was to determine the quality of PAR’s data. A tertiary aim was to report preliminary findings from the registry and contributions to quality improvement initiatives and research up to March 2019.

Aims

To investigate the experience and emotional impact of prosthetic joint infection (PJI) on orthopaedic surgeons and identify holistic strategies to improve the management of PJI and protect surgeons’ wellbeing.

Aims

The aim of this study was to describe implant and patient-reported outcome in patients with a unilateral transfemoral amputation (TFA) treated with a bone-anchored, transcutaneous prosthesis.

Introduction

This analysis aims to provide an update of the Level-IV Partners Arthroplasty Registry (PAR), a quality-improvement initiative and research data repository.

Aims

Vitamin E-diffused, highly crosslinked polyethylene (VEPE) and porous titanium-coated (PTC) shells were introduced in total hip arthroplasty (THA) to reduce the risk of aseptic loosening. The purpose of this study was: 1) to compare the wear properties of VEPE to moderately crosslinked polyethylene; 2) to assess the stability of PTC shells; and 3) to report their clinical outcomes at seven years.

Aims

The primary aim of this study was to quantify the improvement in patient-reported outcome measures (PROMs) following total hip arthroplasty (THA), as well as the extent of any deterioration through the seven-year follow-up. The secondary aim was to identify predictors of PROM improvement and deterioration.

Aims

The primary aim of this study was to compare the wear properties of vitamin E-diffused, highly crosslinked polyethylene (VEPE) and one formulation of moderately crosslinked and mechanically annealed ultra-high molecular weight polyethylene (ModXLPE) in patients five years after primary total hip arthroplasty (THA). The secondary aim was to assess the clinical results of patients treated with VEPE by evaluating patient-reported outcome measures (PROMs), radiological evidence of fixation, and the incidence of mechanical failure.

Introduction

The aim of this study was to evaluate the effects of posterior tibial slope (PTS) and posterior condylar offset (PCO) on patient-reported pain and function one year after TKA.

Introduction

Within the field of arthroplasty, the use of patient-reported outcome measures (PROMs) is becoming increasingly ubiquitous in an effort to employ more patient-centered methods of evaluating success. PROMs may be used to assess general health, joint-specific pain or function, or mental health. General and joint-specific questionnaires are most often used in arthroplasty research, but the relationship between arthroplasty and mental health is less well understood. Furthermore, longitudinal reports of PROM changes after arthroplasty are lacking in the literature.

Our primary aim was to quantify the improvement in general, joint-specific, and mental health PROMs following total hip arthroplasty (THA) as well as the extent of any deterioration through the 7 years follow-up. Our secondary aim was to identify predictors of clinically significant PROM decline.

Introduction

The goal of the current study was to determine if SES affects PROMs in patients treated with THA. Specifically, we sought to determine any potential differences between low and high SES patients in pre-surgical PROMs, post-surgical PROMs, and PROM improvement after surgery while controlling for any potential confounding demographic factors.

Introduction

As orthopaedics shifts towards value-based models of care, methods of evaluating the value of procedures such as a total hip arthroplasty (THA) will become crucial. Patient reported outcome measures (PROMs) can offer a meaningful way for patient-centered input to factor into the determination of value.

Despite their benefits, PROMs can be difficult to interpret as statistically significant, but not clinically relevant, differences between groups can be found. One method of correcting this issue is by using a minimal clinically important improvement (MCII), defined as the smallest improvement in a PROM determined to be important to patients.

This study aims to find demographic and surgical factors that are independently predictive of failing to achieve a MCII in pain and physical function at 1-year following THA.

The primary purpose of the current study was to evaluate and compare the wear properties of vitamin E-doped, highly-crosslinked PE (VEPE) and one formulation of moderately cross-linked and mechanically-annealed ultra-high molecular weight PE (ModXLPE) in patients five years after primary THA. We also sought to understand whether polyethylene wear is associated with radiographic evidence of bone resorption or with deterioration in patient-reported outcome measures (PROMs).

A total of 221 patients from four international centers were recruited into a prospective RSA and clinical outcomes study. Seventy percent (76%) of patients received VEPE (vs. ModXLPE) liners, and 36% received ceramic (vs. metal) femoral heads. PROMs and radiographs were collected preoperatively and at one, two, and five years postoperatively. In addition, RSA radiographs were collected to measure PE wear.

We observed similar bedding in through the one-year interval and wear through the two-year interval between the two liner types. However, there was significantly more femoral head penetration in the ModXLPE cohort compared to the VEPE cohort at the five-year follow-up (p<0.001). The only variables independently predictive of increased wear were ModXLPE (vs VEPE) liner type (β=0.22, p=0.010) and metal (vs. ceramic) femoral head type (β=0.21, p=0.013). There was no association between increased wear and radiolucency development (p=0.866) or PROMs. No patients were found to have evidence of osteolysis.

At five-years postoperatively, patients treated with VEPE (vs. ModXLPE) and ceramic (vs. metal) femoral heads demonstrated decreased wear. At the longest follow-up (five years postoperatively), the wear rates for both liner groups were very low and have not led to any osteolysis or implant failures via aseptic loosening.

The Swedish Hip Arthroplasty Register started in 1979 and celebrates its 40^th anniversary in 2019. The Swedish Hip Arthroplasty Register is not primarily a device register or research database; we strive to provide an overall assessment of the care provided with a multidimensional approach, and to disseminate knowledge on best practices in our network of participating hospitals. Since the inception of the register, there has been a marked change in trends and outcomes.

The completeness of registrations has been 97–99% for primary THA, 93–95% for revisions, and 95–98% for HA over the last 10 years. The register contains 371,125 primary THAs, 55,893 HAs, 83,233 reoperations, and 408,110 PROM responses registered in 352,585 unique patients. All outcome measures have improved over time; primary THA has 0.71% 90-day mortality, 94.3% 10-year implant survival, and 2.2% 2-year reoperation rate. At 1-year follow up, 91% of the patients report a clinically significant pain reduction, 76% report a substantial improvement in health-related quality of life, and 89% are satisfied with the result of the operation.

Moving forward, we are developing enhanced online applications for surgeons, patients and the implant industry to access real-time information. This work involves constructing a shared decision-making tool that helps clinicians assessing the future benefits and risks of THA by offering individualized outcome predictions. Further steps forward include randomized clinical trials and nested studies through the registry's platform. The trends and changes in Swedish arthroplasty practice have largely been promoted and facilitated by the register over the last 40 years.

Deep infection after THA is a devastating complication that implies major suffering for the patients and large costs for society. Reports from multiple national and regional registries show increasing incidence of deep infection. Is this a consequence of improved diagnostics, changed virulence of the causative organism, increased co-morbidity of the patients?

An open database will be setup and hosted by an existing, high quality registry. All possible variables including patient demographic, detailed surgical information, bacteria/fungus characteristics, antibiotic treatment, radiographic findings and follow-up for 3 years will be collected. The incoming data will be displayed on a dashboard with continuous analyses and statistics. Any individual surgeon or hospital can report data.

A board with members from the International Hip Society and the International Society of Arthroplasty Registries will supervise the process and facilitate scientific analyses from collected data.

Osteolysis secondary to ultra-high molecular weight polyethylene (UHMWPE) wear is a leading cause of late-term implant failure via aseptic loosening in patients treated with total hip arthroplasty (THA). Radiation crosslinking of UHMWPE has been shown to decrease wear. However, the resulting polymer (crosslinked-PE) has a high free radical content. Two different methods that have been used to reduce the remaining free radicals are mechanical annealing and chemical stabilization using Vitamin E, a free radical scavenger.

The primary purpose of the current study was to evaluate and compare the wear properties of vitamin E-doped crosslinked-PE (VEPE) and one formulation of mechanically annealed crosslinked-PE using radiostereometric analysis (RSA) in patients five years after primary THA. We also sought to understand the association between polyethylene wear and patient-reported outcome measures (PROMs).

Three-hundred and five patients from six international centers were enrolled. Seventy-six percent were treated with highly-crosslinked (95 kGy) VEPE liners, and the rest received moderately-crosslinked (50 kGy) (ModXL), mechanically annealed liners. Data was collected prospectively at one-, two-, and five-year intervals.

At the 5-year follow-up, proximal femoral head penetration into the VEPE liners (median = 0.05mm (range, −0.03–1.20)) was significantly lower than the penetration into the ModXL liners (median = 0.15mm (range, −0.22–1.04)) (p<0.001). In the VEPE cohort the median proximal penetration did not increase from one- to five-year follow-up (p=0.209). In contrast, there was a significant increase in femoral head penetration for the ModXL group (p<0.001) during that same time. Multivariable regression showed that the only variable predictive of increased wear was ModXL liner type (B=0.12, p<0.001). There were no differences in PROMs between the liner groups, and there was no correlation between polyethylene wear and PROMs for the cohort as a whole.

The current study is the largest analysis of polyethylene wear at five-year follow-up using the RSA technique. We observed similar bedding in through the two-year interval between the two liner types, however, there was significantly more wear in the ModXL cohort at five-years. Currently, the wear rates for both liner groups are below the osteolysis threshold and have not led to any implant failures via aseptic loosening. Continued follow-up will provide a better understanding of the association between wear rate and clinical outcomes.

The gold standard for PJI treatment comprises the use of antibiotic-loaded bone cement spacers, which are limited in their load bearing capacity[1]. Thus, developing an antibiotic-eluting UHMWPE bearing surface can improve the mechanical properties of spacers and improve the quality of life of PJI patients. In this study, we incorporated vancomycin into UHMWPE to investigate its elution characteristics, mechanical properties and its efficacy against an acute PJI in an animal model.

Vancomycin hydrochloride was incorporated into UHMWPE (2 to 14%) by blending and consolidation. We studied drug elution with blocks in PBS and UV-Vis spectroscopy at 280 nm. We determined the tensile mechanical properties and impact strength [3]. We implanted osteochondral plugs in rabbits using either control UHMWPE, bone cement (40g) containing vancomycin (1g) and tobramycin (3.6g) or vancomycin-eluting UHMWPE (n=5) plugs in the patellofemoral groove of rabbits. All rabbits received a beaded titanium rod in the tibial canal. All groups received two doses of 5×10⁷ cfu of bioluminescent S. aureus in the distal tibial canal prior to insertion of the rod and the articular space after closure of the joint capsule. No intravenous antibiotics were used. Bioluminescence signal was measured when the rabbits expired, or at 21-day post-op. Hardware, polyethylene implants, and joint tissues were sonicated to further quantify live bacteria via plate seeding.

Vancomycin elution increased with increasing drug loading. Vancomycin elution above MIC for 3 weeks and optimized mechanical properties were obtained at 6–7 wt% vancomycin loading in UHMWPE. In our lapine acute infection model using bioluminescent S. aureus, knees treated with UHMWPE without antibiotics and bone cement containing vancomycin and tobramycin had significantly higher bioluminescence compared to those treated with vancomycin-eluting UHMWPE.

These results suggest that an antibiotic-eluting UHMWPE spacer with acceptable properties as a bearing surface could be used to treat periprosthetic joint infection in lieu of bone cement spacers and this could allow safer load bearing and a higher quality of life for the patients during treatment. In addition, this presents a safer alternative in cases where the second stage surgery for the implantation of new components is hindered.

Prospectively collected data is an important source of information subjected to change over time. What surgeons were doing in 1999 might not be the case anymore in 2016 and this change in time also applies to a number of factors related to the performance and outcome of total hip replacement. We evaluated the evolution of factors related to the patient, the surgical procedure, socio-economy and various outcome parameters after merging the databases of the Swedish Hip Arthroplasty Register, Statistics Sweden and the National Board of Health and Welfare.

Data on 193,253 THRs (164,113 patients) operated between 1999 and 2012 were merged with databases including general information about the Swedish population and about hospital care. We studied the evolution of surgical volume, patient demographics, socio-economic factors, surgical factors, length of stay, mortality rate, adverse events, re-operation and revision rates and PROMs.

Most patients were operated because of primary osteoarthritis and this share increased further during the period at the expense of decreasing number of patients with inflammatory OA and hip fracture. Comorbidity and ASA scores increased for each year. The share of all cemented implants has dropped from 92% to 68% with a corresponding increase of all uncemented from 2% to 16%.

Length of stay decreased with about 50 percent to 4.5 days in 2012. The 30- and 90-day mortality rate dropped to 0.4% and 0.7%. Re-operation and revision rates at 2 years were lower in the more recent years. The postoperative PROMs are improving despite the preoperative pain scores getting worse.

Even in Sweden, always been considered as a very conservative country with regards to hip replacement surgery, the demographics of the patients, the comorbidities and the primary diagnosis for surgery are changing. Despite these changes the outcomes like mortality, re-operations, revisions and PROMs are improving.

Aims

The objective of this five-year prospective, blinded, randomised controlled trial (RCT) was to compare femoral head penetration into a vitamin E diffused highly cross-linked polyethylene (HXLPE) liner with penetration into a medium cross-linked polyethylene control liner using radiostereometric analysis.

Aims

Our first aim was to determine whether there are significant changes in the level of metal ions in the blood at mid-term follow-up, in patients with an Articular Surface Replacement (ASR) arthroplasty. Secondly, we sought to identify risk factors for any increases.

One of the key factors responsible for altered kinematics and joint stability following contemporary total knee arthroplasty (TKA) is resection of the anterior cruciate ligament (ACL). Therefore, retaining the ACL is often considered to be the “holy grail” of TKA. However, ACL retention can present several technical challenges, and in some cases may not be viable due to an absent or non-functional ACL. Therefore, the goal of this research was to investigate whether substitution of ACL function through an anterior post mechanism could improve kinematic deficits of contemporary posterior cruciate ligament (PCL) retaining (CR) implants. This was done using KneeSIM, a previously established dynamic simulation tool based on an Oxford-rig setup. Deep knee bend, chair-sit, stair-ascent and walking were simulated for a contemporary ACL sacrificing (CR) implant, two ACL retaining implants, and an ACL substituting and PCL retaining implant. The motion of the femoral condyles relative to the tibia was recorded for kinematic comparisons.

Our results revealed that, like ACL retaining implants, the ACL substituting implant could also provide kinematic improvements over contemporary ACL sacrificing implants by reducing early posterior femoral shift and preventing paradoxical anterior sliding. Such ACL substituting implants may be a valuable addition to the armament of joint surgeons, allowing them to provide improved knee function even when ACL retention is not feasible. Further research is required to investigate this mechanism in vitro and in vivo to verify the results of the simulations, and to determine whether kinematic improvements translate into improved clinical outcomes.

Introduction

Radiation cross-linking of ultrahigh molecular weight polyethylene (UHMWPE) has reduced the in vivo wear and osteolysis associated with bearing surface wear (1), significantly reducing revisions associated with this complication (2). Currently, one of the major and most morbid complications of joint arthroplasty is peri-prosthetic infection (3). In this presentation, we will present the guiding principles in using the UHMWPE bearing surface as a delivery device for therapeutic agents and specifically antibiotics. We will also demonstrate efficacy in a clinically relevant intra-articular model.

Introduction

Dual-mobility (DM) liners provide increased range of motion and stability. However, large head diameters have been associated with anterior hip pain due to impingement with surrounding soft-tissues, particularly the iliopsoas. Further, during hip extension the liner can get trapped due to anterior soft-tissue impingement that resists rotation being imparted to the liner from posterior stem-liner contact. Over time this can cause liner rim damage, leading to intra-prosthetic dislocation of the small diameter inner head. To address this, an anatomically contoured dual mobility (ACDM) liner was designed to reduce the volume of the liner below the equator that can interact with soft-tissues (Fig. 1). In this study, we utilized finite element analysis to evaluate tendon-liner contact pressure and tendon stresses with ACDM and conventional designs during hip extension, wherein the posterior edge of liner is in contact with the stem while the anterior edge is exposed to the soft-tissue.

Introduction

When following patients with metal-on-metal (MoM) hip replacements, current evidence suggests that orthopaedic surgeons should avoid reliance on any single investigative tool. In 2014, guidelines for stratifying patients with MoM hip replacement into groups of low, medium, and high risk of failure based on multiple criteria were published. However, such risk stratification guidelines can be difficult to interpret due to the numerous risk factors related to MoM hip replacements. This is especially true for patients with various (high and low) risk levels for different criteria within the guidelines.

The first purpose of this study was to assess if a scoring system can be applied to the current MoM guidelines. The second purpose was to test, using this scoring system, how the contemporary guidelines would classify a cohort of patients with a recalled MoM hip replacement system.

Introduction

Complication and revision rates have shown to be high for all metal-on-metal (MoM) bearings, especially for the ASR Hip System (ASR hip resurfacing arthroplasty (HRA) and ASR XL total hip arthroplasty (THA)). This prompted the global recall of the ASR Hip System in 2010. Many studies have previously explored the association between female gender and revision surgery MoM HRA implants; yet less research has been dedicated to exploring this relationship in MoM THA.

The first purpose of this study was to assess the associations between gender and implant survival, as well as adverse local tissue reaction (ALTR), in patients with MoM THA. Secondly, we sought to report the differences between genders in metal ion levels and patient reported outcome measures (PROMs) in patients with MoM THA.

Introduction

Studies of metal-on-metal (MoM) hip resurfacing arthroplasty (HRA) have reported high complication and failure rates due to elevated metal ion levels. These rates were shown to be especially high for the Articular Surface Replacement (ASR) HRA, possibly due to its unique design. Associations between metal ion concentrations and various biological and mechanical factors have been reported. Component positioning as measured by acetabular inclination has been shown to be of especially strong consequence in metal ion production in ASR HRA patients, but few studies have evaluated acetabular anteversion as an independent variable.

The primary objective of this study was to evaluate the associations between component orientation, quantified by acetabular inclination and anteversion, and blood metal ions. Secondly, we sought to report whether conventional safe zones apply to MoM HRA implants or if these implants require their own positioning standards.

Introduction

In vitro studies showed that the anti-oxidative properties of vitamin E stabilize free radicals while retaining the mechanical strength of UHMWPE. The purpose was to evaluate vitamin E diffused polyethylene (VEPE) wear and stability of femoral components using RSA. Patient reported outcome measures (PROMs) were evaluated to determine the clinical outcome at 5 years.

Introduction

The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998 and femoral heads larger than 32mm in diameter introduced 2004.

The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against large diameter femoral heads at a minimum of 10 years follow-up.

Introduction

The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998. Numerous publications have reported reduced wear rates and a reduction in particle induced peri-prosthetic osteolysis at short to mid-term follow-up.

The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against 32mm femoral heads or less at a minimum of 13 years follow-up.

Introduction

Stem revision with retention of the old cement mantle (cement-in-cement revision) in cases with an intact cement/bone interface is an appealing option. There has been an increasing use of this technique. In 2014 this cement-in- cement technique was used in 10% of all stem revisions reported to the Swedish Hip Arthroplasty Register (SHAR). We analysed the outcome of cement-in-cement stem revisions reported to the SHAR during years 2001–2014

Introduction

Dislocation as a primary cause of revision has been on the increase in Sweden (14% in 2014). The increasing use of Dual Mobility cups (DMC) could well be explained by the increased revision burden due to dislocation, patients undergoing revision having increased comorbidities and reports that dual articular cup designs reduce the risk of dislocation. The aim of this study was to analyze the change in utilization pattern of the dual articular designs used in acetabular revision surgery in Sweden. The short-term survival of DMC was compared to traditional designs.

INTRODUCTION

In native knees anterior cruciate ligament (ACL) and asymmetric shape of the tibial articular surface with a convex lateral plateau are responsible for differential medial and lateral femoral rollback. Contemporary ACL retaining total knee arthroplasty (TKA) improves knee function over ACL sacrificing (CR) TKA; however, these implants do not restore the asymmetric tibial articular geometry. This may explain why ACL retention addresses paradoxical anterior sliding seen in CR TKA, but does not fully restore medial pivot motion. To address this, an ACL retaining biomimetic implant, was designed by moving the femoral component through healthy in vivo kinematics obtained from bi-planar fluoroscopy and sequentially removing material from a tibial template. We hypothesized that the biomimetic articular surface together with ACL preservation would better restore activity dependent kinematics of normal knees, than ACL retention alone.

Introduction

Infection remains a serious complication following primary total hip arthroplasty (THA). Many factors including primary diagnosis, comorbidities and duration of procedure are known to influence the rate of infection. Although the association between patient and surgical factors is increasingly well understood, little is known about the role of the prosthesis. This analysis from the Australian Registry (AOANJRR) was undertaken to determine if revision for infection varied depending on the type of bearing surface used.

Introduction

Dual Mobility (DM) implants have gained popularity for the treatment and prevention of hip dislocation, with increased stability provided by a large diameter mobile liner. However, distal regions of the liner can impinge on soft-tissues like hip capsule and iliopsoas, leading to anterior hip pain. Additionally, soft-tissue impingement may trap the mobile liner, leading to excessive loading of the liner rim, from engagement with the femoral stem, and subsequent intra-prosthetic dislocation. The hypothesis of this study was that reducing the liner profile below the equator (contoured design) can mitigate soft-tissue impingement without compromising inner-head pull-out resistance and overall hip joint stability (Fig. 1).

Introduction

Dual-mobility (DM) liners have increased popularity due to the range of motion and stability provided by these implants. However, larger head diameters have been associated with anterior hip pain, due to surrounding soft-tissue impingement, particularly the iliopsoas. To address this, an anatomically contoured dual mobility (ACDM) liner was designed by reducing the volume of the liner below the equator (Fig1). Previous cadaver studies have shown that the ACDM significantly reduces iliopsoas tenting and trapping of the liner compared to conventional designs. We created a finite element study based on previous cadaver testing to further analyze the effectiveness of the ACDM design in reducing soft-tissue impingement, specifically the tendon-liner contact pressure and the tendon stress.

Introduction

The large diameter mobile polyethylene liner of the dual mobility implant provides increased resistance to hip dislocation. However, a problem specific to the dual mobility system is intra-prosthetic dislocation (IPD), secondary to loss of the retentive rim, causing the inner head to dissociate from the polyethylene liner. We hypothesized that impingement of the polyethylene liner with the surrounding soft-tissue inhibits liner motion, thereby facilitating load transfer from the femoral neck to the liner and leading to loss of retentive rim over time. This mechanism of soft-tissue impingement with the liner was evaluated via cadaver experiments, and retrievals were used to assess polyethylene rim damage.

INTRODUCTION

In native knees the anterior cruciate ligament (ACL) plays a major role in joint stability and kinematics. Sacrificing the ACL in contemporary total knee arthroplasty (TKA) is known to cause abnormal knee motion, and reduced function. Hence, there is growing interest in the development of ACL retaining TKA implants. Accommodation of ACL insertion around the tibial eminence is a challenge with these designs. Therefore, a reproducible and practical test setup is necessary to characterize the strength of the ACL/bone construct in ACL retaining implants. Seminal work showed importance of loading the ACL along its anatomical orientation. However, prior setups designed for this purpose are complex and difficult to incorporate into a standardized test for wide adoption. The goal of this study was to develop a standardized and anatomically relevant test setup for repeatable strength assessment of ACL construct using basic force-displacement testing equipment.

Introduction

Dual Mobility (DM) implants have gained popularity for the treatment and prevention of hip dislocation, with increased stability provided by a large diameter mobile insert. However, distal regions of the insert may impinge on soft tissues like the iliopsoas, leading to groin pain. Additionally, soft-tissue impingement may trap the mobile insert, leading to excessive loading of the insert rim from engagement with the femoral neck and subsequent intra-prosthetic dislocation. To address this, an Anatomically Contoured Dual Mobility (ACDM) insert with a soft-tissue friendly distal geometry was developed (Fig.1). Previously, the ACDM insert was shown to maintain the femoroacetabular contact area and joint stability of a conventional DM insert [Duffy et al. BJJ 2013, 95-B:34, p298; Zumbrunn et al. BJJ 2013, 95-B:34, p605]. The goal of this study was to utilize cadaver specimens to verify whether the ACDM insert could reduce soft-tissue impingement relative to a conventional DM insert.

Introduction

Osteolysis caused by wear of the ultrahigh molecular weight polyethylene (UHMWPE) often leads to failure. Cross-linking improves wear, but also produces residual free radicals that decrease oxidative stability. In vitro studies have shown that the anti-oxidative properties of vitamin E UHMWPE stabilize free radicals while retaining the physical and chemical properties of UHMWPE. The porous surface of the Regenerex™ shell was developed for improved bone in-growth fixation. The increased porosity of the Regenerex™ shell promotes early bony in-growth with the goal of greater long-term stability. The purpose of this study was to evaluate vitamin E infused polyethylene (VEPE) wear and stability of acetabular and femoral components using RSA.

Introduction

In Cruciate Retaining (CR) Total Knee Arthroplasty (TKA), the Posterior Cruciate Ligament (PCL) is preserved but the Anterior Cruciate Ligament (ACL) is sacrificed. In contemporary CR implants, failure to substitute for ACL function causes abnormal knee motion, with the femur being located excessively posterior on the tibia in full extension (Fig. 1), and sliding forward during early flexion. To address this kinematic abnormality, we developed an ACL Substituting Cruciate Retaining (ASCR) TKA implant that substitutes for the absent ACL, while preserving the native PCL. The ASCR tibia includes an ACL substituting post that engages the intercondylar notch of the femoral component in low flexion to act for the missing ACL (Fig. 1). With continued flexion, the post disengages from the femoral component and the native PCL guides further motion of the femur (femoral rollback). Thus the ACL substituting post mimics the native ACL function. The hypothesis of this study was that the ASCR implant can address the abnormal femoral sliding seen in contemporary CR implants.

Introduction

RSA is widely accepted as a precise method to asses wear and migration early in the postoperative period. In traditional RSA, one segment defines both the acetabular shell and the polyethylene liner. However, inserting beads into the liner permits employment of the shell and liner as two separate segments, thus enabling distinct analysis of the precision of three measurement methods in determining wear and acetabular shell migration. The purpose of this in vivo follow-up study was to determine if assigning the shell and liner as one combined, or two individual segments affected the precision of RSA measurements of wear and shell stability.

The limitations and benefits of patient-reported outcome measures, in defining the merits of arthroplasty surgery, are discussed.

Cite this article: Bone Joint J 2015;97-B:578–81.

Introduction:

The ASR™ Articular Surface Replacement and ASR™ XL Metal-on-Metal systems were recalled due to high revision rates at five years. A worldwide clinical follow-up of patients was initiated. This paper summarizes current findings in South Africa (SA) in comparison with those outside SA (OSA).

Summary

Four highly cross-linked UHWMPEs except vitamin E-stabilised explants

Summary Statement

We analysed impaction bone grafting used together with cemented or uncemented fixation in acetabular revision surgery. The overall risk for re-revision did not differ between the cemented and uncemented group. However, aseptic loosening was more common in the cemented group.

Summary

Sequentially irradiated and annealed UHMWPE hip and knee retrievals showed subsurface in vivo oxidation in both the articular surface and unloaded surfaces, while three of four never-implanted shelf stored liners had oxidation in the bulk.

INTRODUCTION

Femoral head diameter has a major influence on stability and dislocation resistance of the hip joint after Total Hip Arthroplasty (THA). Dual Mobility (DM) implants can also reduce the risk of dislocation due the large diameter mobile liner which forms the femoroacetbular articulation. However, recent studies have shown that large head prostheses can directly impinge against native soft tissues, particularly the iliopsoas, leading to anterior hip pain. Dual mobility systems have emerged as a revision option in the treatment of failed metal on metal devices because of the high incidence of post revision instability secondary to abductor loss and need for capsulectomy. We hypothesized that an Anatomically Contoured Dual Mobility (ACDM) liner could provide joint stability while better accommodating the soft tissues surrounding the hip joint.

Introduction:

While kinematic abnormalities of contemporary TKA implants have been well established, a solution has not yet been achieved. We hypothesized that contemporary TKA implants are not compatible with normal soft-tissue function and normal knee motion. We propose a novel technique for reverse engineering advanced implant articular surfaces (biomimetic surface), by using accurate 3D kinematics of normal knees. This technique accounts for surgical placement of the implants, and allows design of tibial and femoral articular surfaces in conjunction.

Introduction:

Large diameter femoral heads have been used successfully to prevent dislocation after Total Hip Arthroplasty (THA). However, recent studies show that the peripheral region of contemporary femoral heads can directly impinge against the native soft-tissues, particularly the iliopsoas, leading to activity limiting anterior hip pain. This is because the spherical articular surface of contemporary prosthesis overhangs beyond that of the native anatomy (Fig. 1). The goal of this research was to develop an anatomically shaped, soft-tissue friendly large diameter femoral head that retains the benefits of contemporary implants.

Introduction:

Dual Mobility (DM) hip implants have gained popularity for the treatment and preventions of instability. In DM implants a large diameter mobile insert matches the native femoral head size. However, studies have shown that the peripheral regions of such large diameter implants overhang beyond the native anatomy and can directly impinge against nearby soft tissues, especially the iliopsoas, leading to groin pain (Fig. 1). Soft-tissue impingement can also trap the mobile DM insert, leading to damage of its peripheral rim, which secures the small diameter inner head (Fig. 2). The goal of this research was to develop an anatomically contoured soft-tissue friendly DM insert.

Introduction

Large diameter femoral heads provide increased range-of-motion and reduced dislocation rates compared to smaller diameter femoral heads. However, several recent studies have reported that contemporary large head prostheses can directly impinge against the local soft tissues leading to anterior hip pain. To address this we developed a novel Anatomically Contoured large diameter femoral Head (ACH) that maintains the profile of a large diameter femoral head over a hemispherical portion and then contours inward the distal profile of the head for soft-tissue relief. We hypothesized that the distal contouring of the ACH articular surface would not affect contact area. The impact of component placement, femoral head to acetabular liner radial clearance, and joint loading during different activities was investigated.

Introduction

Dual mobility (DM) implants provide increased stability and range-of-motion through the use of a large diameter mobile liner articulating against an acetabular shell. However, recent studies have reported that such contemporary large head prostheses can directly impinge against the local soft tissues leading to anterior hip pain. To address this drawback, a novel Anatomically Contoured Dual Mobility (ACDM) liner was developed that maintains the outer spherical geometry over an approximately hemispherical portion and then contours inward the distal profile of the DM liner for soft-tissue relief. The extent of the inner profile encapsulating the small diameter head is increased to provide more coverage of the head and maintain the inner head pullout force. We hypothesized that the ACDM liner for soft-tissue relief would not affect retention of the small diameter inner head or liner-acetabular load-bearing contact area.

Introduction:

Contemporary Posterior Cruciate Ligament (PCL) retaining TKA implants (CR) are associated with well-known kinematic deficits, such as absence of medial pivot motion, paradoxical anterior femoral sliding, and posterior femoral subluxation at full extension. The hypothesis of this study was that a biomimetic implant, reverse engineered by using healthy knee kinematics to carve the tibial articular surface, could restore normal kinematic patterns of the knee.

Introduction:

Acetabular component orientation has been linked to hip stability as well as bearing mechanics such as wear. Previous studies have demonstrated wide variations of cup placement in hip arthroplasty using conventional implantation techniques which rely upon either anatomic landmarks or the use of commercial positioning guides. Enabling technologies such as navigation have been used to improve precision and accuracy. Newer technologies such as robotic guidance have been postulated to further improve accuracy. The goal of our study was to evaluate the clinical reproducibility of a consecutive series of haptically guided THR.

Introduction:

Acetabular cup position is an important factor in successful total hip arthroplasty (THA). Optimal cup placement requires surgeons to possess an accurate perception of pelvic orientation during cup impaction, however, varying pelvic anatomy and limited visual cues in the surgical field may interfere with this process. The purpose of this study was to evaluate the utility of an inertial measurement unit (IMU) in monitoring pelvic position during THA.

INTRODUCTION

Femoral head diameter has a major influence on stability and dislocation resistance after Total Hip Arthroplasty (THA). Although routine use of large heads is common, several recent studies have shown that contemporary large head prostheses can directly impinge against native soft tissues, particularly the iliopsoas which wraps around the femoral head, leading to refractory anterior hip pain. To address this, we developed a novel Anatomically Contoured large diameter femoral Head (ACH). We hypothesized that anatomical contouring of the ACH implant for soft tissue relief would not compromise dislocation resistance, and the ACH implant would provide increased stability compared to small heads.

Introduction

In total hip arthroplasty, the positioning of the acetabular cup, in particular, has been shown to play an important role in the survivorship of the prosthetic joint. The commonly accepted “safe zone” extends from 5–30° of anteversion to 30–50° of inclination. However, several studies have utilized a more restrictive safe zone of 5–25° of anteversion and 30–45° of inclination, a modification of the Lewinnek zone. Many attempts have been made to develop a more reliable method of positioning the acetabular component. Robotic-assisted surgery is one such method. The purpose of this study was to compare the resulting position of the acetabular component after robotic-assisted surgery with the intraoperative robotic data to determine if improved accuracy can be achieved with the robotic-assisted method.

Introduction

Proper cup positioning is a critical component in the success of total hip arthroplasty surgery. A multicenter study has been initiated to study a new type of highly cross-linked polyethylene. This study provides a unique opportunity to a review the acetabular cup placement of over 500 patients implanted in the past 2 years from 13 medical centers from the U.S., Mexico, and Europe.

Introduction

Total hip replacements using highly cross-linked polyethylene show excellent clinical outcomes, low wear, and minimal lysis at 5 years follow-up. A recent RSA study reports a significant increase in femoral head penetration between 5 and 7 years. This study is a multi-center radiographic analysis to determine whether the RSA observation is present in a large patient cohort.

Introduction

Acetabular cup positioning has been linked to dislocation and increased bearing surface wear. A previous study found correlations between patient and surgical factors and acetabular component position. The purpose of this study was to determine if acetabular cup positioning improves when surgeons receive feedback on their performance.

Purpose: The purpose of this study was to determine if correlation exists between acetabular cup positioning and factors relating to the surgeon and patient.

Method: Data for 2063 patients who underwent primary or revision THA from 2004 – 2008 were compiled. The post-op anteroposterior (AP) and cross-table lateral digital radiographs for each patient were obtained. The AP radiograph was measured using Hip Analysis Suite to calculate the cup abduction and version angles (version direction determined separately). Acceptable ranges were 35–45° for abduction, and 5–20° for version. Correlations were then determined with SPSS™ software.

Results: There were 1980(96%) qualifying patients. There were 1025(52%) acetabular cups that fell within the 35–45° abduction range, and 1287(70%) cups in the 5–20° version range. Regression analysis showed that the only independent predictor of acceptable abduction angle was the surgical approach (p< 0.001). Posterolateral approach was the most accurate (57% acceptability). In contrast to the posterolateral, the MIS (2 incision) approach was 3 times (95%C.I. 1.5–5, p=0.001), and the mini anterolateral approach 2.5 times (95%C.I. 1–6.5, p=0.035) more likely to have unacceptable abduction angles. The only independent predictor of acceptable version was the performing surgeon (p< 0.001), with higher volume surgeons showing greater accuracy.

Conclusion: The posterolateral approach was superior to MIS (2 incision) and mini anterolateral approaches for acceptable abduction angle, and surgeon volume influenced version angle acceptability. Further analysis on variables and their influence on cup position at a lower volume medical center would provide a valuable comparison.

Radiation crosslinking decreases the wear of ultra-high molecular weight polyethylene (UHMWPE) and subsequent heating increases its oxidative stability. Clinical trials are showing lower femoral head penetration rate with highly crosslinked vs. conventional UHMWPE liners. Recently, a follow-up report showed a surprising increase in the femoral head penetration rate with a highly crosslinked UHMWPE, prompting us to closely analyze surgically explanted highly crosslinked UHMWPEs.

Thirty-four highly crosslinked components, all irradiated (100kGy) and melted, were included in the study. The components were surgically removed from patients for non-polyethylene related reasons. Oxidation was determined at the rim immediately after explantation. After shelf storage in air for 5–77 months, oxidation and crosslink density were measured at the rim and articular surfaces. An additional retrieval (92 mos. in vivo) was tested on the hip simulator; oxidation and crosslink density were determined after simulator testing.

All components showed no detectable oxidation immediately after explantation; however, surprisingly oxidation levels increased during shelf storage. Areas with increased oxidation showed a decrease in crosslink density. These changes did not correlate with in vivo duration; however, they correlated strongly with ex vivo duration. The component subjected to hip simulator testing showed no measurable wear and showed no detectable oxidation or marked decrease in crosslink density.

Two mechanisms may have reduced the oxidation resistance of highly crosslinked UHMWPE upon exposure to in vivo elements and subsequent exposure to air. One mechanism is based on free radical formation during cyclic loading; the other is based on an oxidation cascade initiated by absorbed lipids. Further studies are necessary to determine the impact of these mechanisms, if any, on the stability of components during in vivo service.

There are a variety of patient and surgical factors shown to increase post-operative complication risk for a total hip arthroplasty (THA). While many studies have linked patient and surgical factors to unsuccessful outcomes post total hip arthroplasty (THA), no study has attempted to correlate the infiuence of these factors to the positioning of the acetabular cup. The purpose of this study was to determine if a correlation exists between patient and surgical factors and the anatomical position of the acetabular component.

Data for 2063 patients from 2004–2008 who underwent a primary total hip arthroplasty (THA), revision THA, or Birmingham Hip Resurfacing procedure was compiled. The post- op anteroposterior pelvis (AP) and the cross table lateral digital radiographs for each patient were measured to determine cup inclination and version. Acceptable angle ranges were defined as 30–45° for abduction, and 5–25° for version. Correlations between variables and cup abduction and version angles were determined with SPSS™ statistical software.

There were 1954(95%) qualifying patients. There were 1218(62%) acetabular cups that fell within the 30–45° optimal abduction range, and 1576(87%) cups in the 5–25° optimal version range. There were 921(47%) patients that had both inclination and version angles that fell within the optimal range. Regression analysis showed that surgical approach (p> 0.001), high/low volume surgeon (p< 0.001), and obesity (BMI > 30, p=0.01) were independent predictors for abduction and version combined analysis. Both surgical approach (p< 0.001) and BMI (p=0.018) were independent predictors in the individual analysis of both abduction and version. High/low volume surgeon was significant for the independent analysis of abduction (p=0.013). In the combined analysis, low volume surgeons showed a 2 fold increase (95% C.I. 1.5–2.8) in risk for cup malpositioning compared to high volume surgeons. The MIS surgical approach showed a 6 fold increase (95% C.I. 3.5–10.7) in risk for cup malpositioning compared to the posterolateral approach. Obesity (BMI> 30) showed a 1.3 fold increase (95% C.I. 1.1–1.7) in risk for cup malpositioning compared to all other body mass index groups.

Posterolateral surgical approach was superior to MIS surgical approaches for independent and combined abduction and version analysis. High volume surgeons had greater accuracy for cup positioning, specifically for achieving optimal cup abduction angle. Compared to all other body mass index categories, patients that were obese (BMI> 30) displayed a greater risk for cup malpositioning for independent and combined abduction and version analysis. Further statistical analyses on patient and surgical variables and their infiuence on cup position at a lower volume medical center would provide a valuable data comparison.

Studies of patients having primary THR using highly cross-linked polyethylene show excellent clinical outcomes and very low radiographic wear results at a minimum of 5 years follow-up. Recently, a radiostereometric analysis (RSA) study of a small group of patients reported that after no detectable wear during years 1–5, they found a significant increase in femoral head penetration between 5 and 7 years follow-up. However, this increase in head penetration after 5 years has not been confirmed in a larger patient cohort.

The purpose of this study was to organize a multicenter radiographic study involving leading medical centers in the U.S. having the longest-term follow-up available on this type of highly cross-linked polyethylene in order to determine if the RSA observation can be confirmed in a larger study.

Six academic centers agreed to contribute radiographic data to this study. All patients received primary total hip replacements with Longevity polyethylene liners (Zimmer, Warsaw, IN) coupled with 26, 28, and 32mm cobalt chrome femoral heads. The radiographic inclusion criteria required a minimum of four radiographs per patient: one at 1 year; at least one from 2 to 4.5 years; one 4.5 to 5.5 years; and at least one from 5.5 to 9 years follow-up. The Martell Hip Analysis Suit-eTM software was used for the wear analysis. All wear values were determined by calculating head penetration between the follow-up radiograph and the 1-year radiograph to remove creep, the majority of which has been shown to occur during the first year. Separate linear regressions, representing the wear rates, were computed for the early period from 1 year to 5.5 years and the late period from 5.5 years to 9 years follow-up. The Zar test was used to determine the significance of the difference between these two linear regressions.

We present the completed analysis of 165 hips. When the early and late data points were combined into one data set, the second-order regression indicated an inflection point at 6.3 years with a slightly positive inflection. There were 402 film comparisons in the early time period, and the slope and confidence interval of the regression line was 4.9μm/yr (95% CI of −28μm/yr to 38μm/yr). There were 188 film comparisons in the late period, and slope of the regression line for the late period was 10.8 μm/yr (95% CI of −58μm/yr to 80μm/yr). The Zar test showed no significant difference between the two slopes (Figure 1, p=0.886).

No significant increase in femoral head penetration was found for the late period after 5 years compared to the early period before 5 years follow-up in either analysis. Additionally, no significant late increase in wear was seen within individuals. While we continue to enroll patients, at this time we do not observe the increase in wear seen in the RSA study after 5 years.

Of 960 first-revision total hip replacements (THR) because of deep infection identified in the Swedish Hip Arthroplasty Registry, 16.9% were treated with a permanent implant extraction, while a staged or direct reconstruction revision protocol were employed in 56.2% and 26.9% respectively. The majority of the interventions were performed more than one year after index THR, and the dominating pathogen was coagulase negative staphylococci (CNS). We found a significant shift in types of bacteria over the years (Chi-square test, p smaller than 0.001): an increase in the CNS group and a decrease in Gram-negative aerobes. Patients treated with a permanent resection were generally older (p< 0.001), had more often a previous ipsilateral hip fracture (p< 0.001), and had more frequently Gram-negative infections (p=0.02). No systematic differences in patient characteristics or pathogens were detected between one-stage or two-stage procedures, of which the latter had a median re-implantation time of 2 (range: 0.2–62) months. Of 798 (one- or two-stage) revisions, 60 (7.5%) were revised again due to recurrent infection, with no difference between the two methods, and implying a 10-year survival of 90%; 95% confidence interval (CI95%) 88.2–93.0. Previous surgery for soft-tissue problems (RR 3.2 (CI95% 1.3–7.2)) predicted a worse outcome for one-stage procedures. The prognosis of two-staged revisions improved with increasing re-implantation interval (RR 0.8 (CI95% 0.7–1.0)) per month, and a 6 month interval carried the lowest risk of repeat revision due to infection; RR 0.1 (CI95% 0.0–0.9). Staged revisions in female patients (RR 2.3, (CI95% 0.9–5.7)) and with Staphylococcus aureus infections (RR 2.3 (CI95% 0.9–5.5)) predicted a worse outcome. Ten-year survival with repeat revision for aseptic loosening as end-point was 89% (95%CI 85.7–92.0), but decreased to 79% when all reasons for revision were taken into account (95%CI 75.0–82.3) mainly because of revision for peri-prosthetic fractures.

The results suggest that direct and staged revision protocols can have a good prognosis on a national level, but efforts must be made to counteract periprosthetic fractures and the high incidence of permanent implant extraction in elderly patients.

Background: Abductor failure after total hip arthroplasty is a rare but debilitating problem. The diagnosis is difficult, and when recognized, there are few successful treatment options. The purpose of this study is to review our experience with a new surgical technique using fresh-frozen Achilles tendon allograft with an attached calcaneal bone graft to reconstruct a deficient abductor mechanism after total hip arthroplasty.

Methods: From 2003 to 2006, we performed seven abductor reconstructions with Achilles tendon allograft for patients with abductor deficiency after total hip arthroplasty. Four patients had a prior posterior approach and three had a prior anterolateral approach. At a mean of 29 months from index procedure, all seven patients suffered from symptoms of lateral hip pain and abductor weakness as documented by positive Trendelenburg sign, limp, and limited motor strength with side-lying abduction. Hip arthrograms were obtained in five of seven patients.

Results: The average pre-reconstruction Harris Hip Score was 34.7 and average pain score was 11.4. All five hip arthrograms showed extravasation of dye over the greater trochanter, confirming the diagnosis of a bald greater trochanter and massive abductor loss found at time of surgery. At a minimum 24 month follow-up and an average follow-up of 31 months, the post-reconstruction Harris Hip Score was 85.9 and the average pain score was 38.9.

Conclusions: Abductor reconstruction with Achilles tendon allograft using calcaneal bone block fastened to the greater trochanter has offered significant relief of pain and improvement in function at early follow-up in this series of patients.

Highly cross-linked polyethylene liners in total hip replacement (THR) have allowed the use of larger diameter femoral heads. Larger heads allow for increased range of motion, decreased implant impingement, and protection against dislocation. The purpose of this study is to report the clinical and radiographic outcomes of patients with large femoral heads with HXLPE at 5 years post-op.

A group of 124 patients (132 THRs) who had a primary THR with a 36mm or larger cobalt-chrome femoral head and a Durasul or Longevity liner (Zimmer; Warsaw, IN) were prospectively enrolled in this study. 93 THRs (88 patients) had minimum 5 year follow-up. All patients received a cementless acetabular shell (Trilogy or Inter-op, Zimmer Inc, Warsaw IN) and a highly cross-linked polyethylene liner with an inner diameter of 36 or 38mm. The median radiographic follow-up was 5.6 years (range 5.0–8.0), and patients were assessed clinically by Harris Hip score, UCLA activity score, EQ-5D, and SF-36 functional scores. Femoral head penetration was measured using the Martell Hip Analysis Suite.

No osteolysis was seen in the pelvis or proximal femur, and no components failed due to aseptic loosening. Four patients have questionable signs of bone changes around the acetabular shell with future CT scans scheduled to help reach a final determination. The median acetabular shell abduction and anteversion were 44° (30–66°) and 13° (3–33°) respectively. There was no evidence of cup migration, screw breakage, or eccentric wear on the liner. Regarding the femoral component, there were no episodes of loosening, migration, osteolysis, or fracture. There was no significant difference in the median penetration rate from post-op to longest follow-up between the 36mm (24 patients) and 38mm (4 patients) femoral head groups (0.056±0.10mm/yr and 0.060±0.05mm/yr respectively). Therefore, the data were pooled into one group. Using every post-op to follow-up comparison, the linear regression penetration rate of this combined group was 0.003 mm/yr which is within the error detection of the Martell method. The median femoral head penetration rate during the first post-op year measured 0.59±1.04 mm/yr. In contrast, the median steady state wear rate from the 1yr film to the longest follow-up measured -0.009±0.15mm/yr. A linear regression steady state wear rate from the 1 year film to every follow-up of −0.031 mm/yr indicated no correlation between the magnitude of polyethylene wear and time.

The mid-term results on this series of patients with THRs with a 36 or 38mm femoral head articulating with highly cross-linked polyethylene showed excellent clinical, radiographic, and wear results. The lack of early signs of osteolysis with the use of these large diameter femoral heads is encouraging. Continued and longer-term follow-up is needed to provide survivorship data.

Highly cross-linked polyethylene (HXLPE) is one of the most widely utilized bearing surfaces for total hip arthroplasty (THA). The first patients to receive XLPE will be 10 years post-op as of December 31, 2008. The purpose of this study is to report the long-term clinical and radiographic outcomes of patients implanted with HXLPE.

A group of 247 primary total hip replacements (224 patients) using HXLPE liners (Longevity or Durasul, Zimmer Inc.) with 22, 26, 28, or 32mm femoral heads were implanted between 1999 and 2001. Clinical evaluation measures included the Harris hip, EQ-5D, SF-36 functional scores, and UCLA activity scores. In addition to plain radiograph assessment, the computerized Martell method was used to measure head penetration over time. A matched group of 241 primary total hip replacements (201 patients) with the same head sizes using conventional polyethylene (PE) with a minimum of 7 years follow-up was used as a Martell method control group. The steady state penetration rate was defined as the slope of the linear regression line of the plot of head penetration from the 1 year film to each subsequent film to discount the early bedding-in process. A student’s t-test was used to compare wear rates between head sizes in each group, and a repeated-measures mixed model ANOVA was used to compare the groups for the 28mm head size.

There were no osteolytic lesions around the cup or stem, and no revisions were performed for polyethylene wear or liner fracture. Clinical outcome scores were averaged: Harris Hip 88.1±11.97, EQ-5D 74.0±27.0, SF-36 physical activity scores 53.3±8.4, SF-36 mental score 46.9±11.1, and UCLA activity 6.4±2.1. The steady state wear of the conventional polyethylene patients increased with time for both 26 and 28mm head sizes (0.144 and 0.127mm/year, respectively). No significant difference was found between the head sizes coupled with conventional polyethylene (p=0.14). Femoral head penetration in the highly cross-linked polyethylene did not increase over time after the first year. The steady state wear rates of HXLPE liners with 28mm or 32mm femoral heads were not significantly different than a slope of zero (p=0.54 for both head sizes).

Clinical follow-up results are typical of a primary THR patient population, and the radiographic results are excellent with no signs of peri-prosthetic osteolysis. Patients with PE show wear rates that are significantly different than zero indicating significant wear of the material. Conversely, patients with HXLPE display no measureable wear at 7–9 years as the wear rates were within the error detection of the Martell method. This long-term clinical and radiographic follow-up study for this new bearing material shows excellent clinical outcomes with very low in vivo wear.

Objective: The Charnley grading system (A, B, C) has previously been shown to be a valid predictor concerning outcome after joint replacement surgery. In this study we hypothesized that anxiety/depression, one of five dimensions in the health related quality of life measurement tool EQ-5D, could predict the outcome after total hip replacement surgery.

Methods: Data from the Swedish Hip Arthroplasty Register including 6 158 patients with primary osteoarthritis were analysed. To examine the association of anxiety with respect to the outcome of pain (VAS) and satisfaction (VAS) a general linear regression model was used.

A subgroup of 481 patients in the Western Region of Sweden with complete data on individual CPP (cost per patient) was selected for the health economic analysis.

Results: The preoperative EQ-5D anxiety/depression dimension was a strong predictor for pain relief, patient satisfaction, and cost-effectiveness with surgery. Patients with comorbidity (Charnley category C) had a significant worse outcome with regards to pain relief, satisfaction and EQ-5D index scores than patients in Charnley category A and B (p< 0.001). Females generally had worse outcome scores than males in all three outcome measurements (p< 0.001).

Conclusion: Orthopaedic surgeons involved with the care of patients eligible for THR surgery should be alert to the fact that mental health may influence pain-experience and HRQoL outcome. Appropriate assessment of mental health may enable us to modify the approach in which we manage these patients, in order to optimize the outcome following joint replacement surgery.

Introduction: Electron beam irradiated highly cros-slinked polyethylene has been used in total hip arthroplasty for over 8 years. Due to its low wear characteristics, the use of femoral heads that are greater than 32mm in diameter is now available, allowing for an increase in range of motion and increased stability against dislocation when necessary. The purpose of this study is to provide a summary report on the radiographic analysis of the longest term data available on primary THR patients receiving highly cross-linked polyethylene and to compare the results of two methods of measuring femoral head penetration.

Methods: Three prospective clinical studies involving electron beam irradiated highly cross-linked polyethylene have been initiated at our center. To date, the results of: 200 hips with a minimum of 6 year follow-up with conventional sized femoral heads (primarily 28 and 32mm); 45 hips with minimum 5 year follow-up with larger sized femoral heads (primarily 36 and 38mm); and 30 hips with 5 year follow-up enrolled in a Radiostereometric analysis (RSA) study (15 patients with 28mm and 15 patients with 36mm diameter femoral heads); were available for this summary report. Data from patient administered questionnaires (Harris Hip score, UCLA activity score, and WOMAC), radiographic review, and wear analysis using RSA or the Martell Hip Analysis Suite™. In addition, for comparative purposes, wear was measured in a subset of patients using the Devane Polyware™ program.

Results: All hips had good clinical outcome at longest follow-up regardless of which femoral head size was used. There were no revisions due to polyethylene wear and no evidence of peri-prosthetic osteolysis. In general, after the bedding in period, there was no significant increase in femoral head penetration regardless of head size.

For RSA, the wear rate for the 28mm femoral head group was 0.05±0.02 while the 36mm femoral head group was 0.03±0.02, p=0.13.

For the Martell analysis, the average steady-state wear rate was −0.002 ± 0.01 mm per year and −0.026 ± 0.13 mm per year for 28mm and 32mm head sizes, respectively, p=0.62. There was no correlation between wear and time in situ or femoral head size for any of the clinical studies.

In comparing the Martell and Devane programs, the total average wear rates were significantly different, 0.07±0.05 and 0.03±0.06mm/year respectively, p=0.01. However, when the absolute values of the Martell results were used, there was no difference, p=0.22.

Conclusion: The mid-term follow-up of a large group of primary THR patients receiving highly cross-linked polyethylene components have shown no problems related to the new bearing material. Extremely low wear and lack of peri-prosthetic osteolysis are encouraging results requiring further long-term study.

Background: The rates of primary and revision knee arthroplasty in the United States have been increasing. Simultaneously, several studies have reported increased complication rates when these procedures are performed at low-volume centers. One innovation designed to improve knee arthroplasty outcomes is computer navigation, which aims to reduce revision rates by improving the alignment achieved at surgery. The purpose of this study was to examine the impact of hospital volume on the costeffectiveness of this new technology in order to determine its feasibility and the level of evidence that should be sought prior to its adoption.

Methods: A Markov decision model was used to evaluate the cost-effectiveness of computer-assisted knee arthroplasty, in relation to hospital volume. Transition probabilities were estimated from the arthroplasty literature, and costs were based on the average reimbursement for primary and revision knee arthroplasty at out institution. Outcomes were measured in quality adjusted life years.

Results: The results demonstrate that computer-assisted surgery becomes less cost-effective as the annual hospital volume decreases, as the cost of navigation increases, and as the impact on revision rates decreases. If a center performs 250 cases per year, computer navigation will be cost-effective if the annual revision rate is reduced by 2% per year over a twenty-year period. If a center performs 150 cases per year, computer navigation is cost-effective if it results in a 2.5% reduction in the annual revision rate over a twenty-year period. If a center performs only 25 cases per year, the annual reduction in revision rates must be 13% for computer navigation to be cost-effective.

Conclusion: This analysis demonstrates that computer navigation is not likely to be a cost-effective investment in health care improvement in low volume joint replacement centers, where its benefit is most likely to be realized. However, it may be a cost-effective technology for higher volume joint replacement centers, where the decrease in the rate of knee revision needed to make the investment cost-effective is modest, if improvements in revisions rates with the use of this technology can be realized. This illustrates that hospital volume can have a substantial impact on the cost-effectiveness of new technology in surgery, and this should be carefully considered by any center considering such a large capital investment.

In a previous report from a randomised study we reported excellent fixation and less proximal periprosthetic bone mineral loss around the Epoch design at 2 years follow-up when compared with a solid stem of similar design. We now present the 7 years follow-up.

Forty consecutive patients (20 men, 10 women, mean age 57, 41–74) with non-inflammatory osteoarthritis were randomised to receive either a cementless porous-coated composite stem with reduced stiffness (Epoch) or a cementless stiff stem with a porous coating (Anatomic). Patients were followed for 7 years with repeated evaluations using radiostereometry, DXA, conventional radiography and Harris Hip Score (HHS).

At 7 years 1 stem had been revised (Anatomic) due to late infection. Subsidence and stem rotations were close to zero without any difference between the two groups (p> 0,12). Median wear rates were lower than expected (0.4mm up to 7 years) for both stem designs. At 2 years loss bone mineral density was less in Gruen regions 1, 2, 6 and 7 for the Epoch stems (p< 0.04), but this difference tended to disappear with time. At 7 years only the calcar region (Gruen region 7) had significantly denser bone in the Epoch group (p< 0.001). The HHS scores did not differ (median 98, 51–100). No stem was radiographically loose.

The Epoch stem achieved excellent fixation. Wear rates were low despite use of conventionally gamma-sterilised polyethylene. This low modulus stem had positive effects on early proximal bone remodeling, but this effect decreased with time.

Starting in the 1970s, long-term survivorship of total hip and knee arthroplasty has been under investigation for the Scandinavian population with the aid of implants registries. In the United States, no national arthroplasty registry currently exists. Nationwide inpatient discharge databases in the United States have proven useful when comparing the revision burden in the United States and Scandinavia. For this study, we compared the implant survivorship in the Medicare population with contemporaneous registry-based data from well-established and validated Scandinavian arthroplasty registries. The 5% systematic sample of Medicare claims from 1997 to 2004 were examined for primary and revision THA and TKA claims. The Medicare beneficiary ID was used to follow patients longitudinally between primary and revision surgery. De-identified data from the Norwegian and Swedish national hip and knee registry were also obtained for the same time period. During the 8-year study period, 30,583 and 62,878 elective primary total hip or knee replacements, respectively, were extracted from the Medicare data. In the same time period, 41,823 and 15,927 primary total hips or knees replacements were identified from the Norwegian registry. 82,037 primary total hips were identified from the Swedish registry. Survivorship was assessed by the Kaplan-Meier method, and Cox regression was used to evaluate the effect of patient attributes and cross-country comparisons. The K-M estimate showed that 8 years post-primary surgery, 93.6% of THA and 96.2% of TKA remained revision-free among the elderly Medicare population. By comparison, among Norwegians aged 65 and above, 96.0% of THA and 93.6% of TKA remained revision-free. In the US, men had a significantly higher risk of knee revision than women, but no significant gender difference among hip revision. In Norway, men had a significantly higher risk of hip revision, but no differences in knee revisions. In Sweden, men had a significantly higher risk of hip revision (5.4% vs. 3.3%). Older patients had a reduced risk of revision as compared with younger patients, in both the US and in Norway. The survival of THA is significantly better in Norway than in the US with a hazard ratio of 1.64 (p< 0.05). On the other hand, TKA had a better survival experience in the US than in Norway, with a hazard ratio of 0.55 (p< 0.05). This is the first study to evaluate the utility of Medicare as a source of THA and TKA survivorship data and to compare prosthesis outcomes in Medicare with those from Scandinavian arthroplasty registries. Unlike the Norwegian and Swedish registry data, the reasons for revision (e.g., femoral loosening) are not captured and thus greatly limited the value of the Medicare data as a tool to understand the need for revision, thereby helping to improve implant longevity and to reduce the associated cost and burden to the patient and care provider.

INTRODUCTION: The postoperative periprosthetic femoral fracture is a severe complication after total hip surgery. It has become the third most common reason for revision. Three-hundred and twenty one fractures operated during 1999–2000, were followed in a prospective nationwide study. The study focused on the failure rate, patient satisfaction, treatment and radiographic evaluation.

PATIENTS AND METHODS: During 1999–2000, 230 fractures after a primary THR and 91 after a revision THR were reported to the Swedish National Hip Arthroplasty Register. All hospital records were collected. At follow-up the Harris hip score, a health-related quality of life measure (EQ-5D) and patient satisfaction were used as outcome measurement. A radiologist performed the radiographic evaluation.

RESULTS: A high number of patients had a loose implant at fracture time (66% in the primary group and 51% in the revision group). Eighty-eight percent of the fractures were classified as Vancouver type B fractures. A major finding was the association between the type of implant and the risk of a periprosthetic fracture. The Charnley and the Exeter prostheses were significantly over represented among patients with fractures and the Lubinus prosthesis significantly under represented. The surgeons grading of the Vancouver type B1 fracture was not in agreement with the study radiologist in more than 34% of the cases. Patient’s satisfaction concerning mobility, self-care, normal activities, pain and anxiety compared to an age matched population with a THR were poor. There was a high failure rate and by December 31, 2004, 22% had been reoperated.

DISCUSSION: A recommendation is to follow all THR patients with regularly radiographic monitoring and to intervene before the fracture. Implant related factors have to be considered when choosing implant for routine use. Difficulty in evaluating the x-rays concerning the stability of the prostheses might lead to sub optimal treatment. We recommend exploration of the implant for all patients with a Vancouver type B fracture if there is any doubt about the fixation status.

In this study we hypothesised that anxiety/depression, one of five dimensions in the health-related quality of life (HRQoL) measurement tool EQ-5D, could predict outcome after total hip replacement surgery.

Pre-operative and one-year post-operative data from the Swedish Hip Arthroplasty Register, including 6158 patients with primary osteoarthritis of the hip, were analysed. In order to examine the association between anxiety and outcome with respect to pain and satisfaction an analysis of covariance was used.

The pre-operative EQ-5D anxiety/depression dimension was a strong predictor for pain relief and patient satisfaction (p < 0.001).

Orthopaedic surgeons involved in the care of patients eligible for total hip replacement surgery should be aware that mental health may influence post-operative pain and HRQoL. An appropriate assessment of mental health may enable a modification in the way these patients are managed in order to optimise the outcome after joint replacement surgery.

Introduction: The annual wear rate in polyethylene articulations should be 0.1 mm or less to avoid future osteolysis. Highly Crosslinked polyethylene demonstrates 80–90% wear reduction in hip simulator testing, but the clinical documentation of this new polyethylene is still inadequate. We evaluated the highly crosslink PE in two prospective randomised clinical studies. Patients and Methods: Thirty two patients (12 male, 20 female, 64 hips) with a median age of 48 years (range, 29–70 years) with bilateral primary or secondary arthrosis of the hip received hybrid THA. With liners made of highly cross-link on one side and conventional PE on the other one. Twenty-seven patients in this study have passed 2 years follow up. Further Sixty patients (61 hips) with a median age of 55 years (range, 35–70 years) were randomized to receive either highly crosslink or conventional cemented all PE of the same design. Forty-nine patients have been followed for 3 years. In both studies all patients received Spectron stems with 28mm cobalt-chromium head. Radiostereometric examinations with the patient supine or standing were done at regular intervals. Wear was measured in the supine position from the postoperative week, whereas standing examinations were initiated three months after the operation. Results: The penetration rate was almost identical in the study and control groups in 6 months after the operation. Thereafter the penetration rate levelled out in the 2 groups with highly crosslink PE. At two years the highly crosslink PE liner showed 62% lower proximal penetration and 31% lower total (three-dimensional) penetration when the patients were examined in supine position. The highly crosslink all PE cemented cups showed significantly lower proximal penetration in both position. Discussion: The better wear performance of highly crosslink PE could increase the implant longevity. Longer follow up is needed to evaluate if this new material is associated with less occurrence of osteolysis.

Objectives. The Swedish National Total Hip Arthroplasty Register, initiated in 1979, describes the epidemiology of total hip replacement (THR) in Sweden. The objective of this study was to describe the epidemiology, demographics and to perform an outcome analysis on patients, younger than 55 years, who underwent a total hip replacement in Sweden between 1992–2002. Methods. From the Swedish National Total Hip Arthroplasty Register 11579 patients, younger than 55 years at the time of surgery, were identified who had undergone a primary total hip replacement from 1992–2002. The patients selected were checked with the Swedish Cause of Death Register (CDR), based on the unique identification number used in Sweden, to ensure that only living patients were addressed. Epidemiological and demographical analysis was then performed using SPSS (SPSS Inc, Chicago, IL). Outcome. 11362 patients were identified. 5260 (46,3 %) men and 6102 (53,7 %) women, the mean age was 48, 2 years (14–55). The indication for surgery was in over 60% of the cases Osteoarthrosis (OA) but over-represented diagnosis, when compared to the remaining THR operations in Sweden, were arthritis, osteonecrosis and sequele after childhood disease. The most common fixation technique used was cemented total hip replacement in 6160 (54,2 %) followed by Hybrid 2442 (21,5 %) and uncemented 2235 (19,7 %) technique. Survival for cemented, uncemented and hybrid implants in male patients with Osteoarthrosis after 10 years was 65,8 % (+/− 2,6%), 66,6 % (+/− 2,9%) and 64,0 % (+/− 3,0 %) respectively. In the arthritis group the survival was slightly better with a 10 year survival of 72,8 % (+/− 3,6%), 66,8 % (+/− 5,9%) and 71,5 % (+/− 7,5%) respectively, male patients had a slightly inferior outcome compared to females across all diagnosis groups. Conclusions. This young cohort is epidemiologically and demographically different than the older one previously studied in the Swedish National Hip Register. Survival analysis shows that 10 year survival in this population is considerably worse than for the older cohort. Patients with arthritis fare better than patients with Osteoarthrosis and females have superior outcome to males. In this study the mode of implant fixation did not appear to influence survival in patients with OA, however it does seem to affect the outcome in patients with inflammatory arthritis. This study shows that the outcome in this patient category is poor when compared with the older THR patients. There is an obvious need to increase use of alternative and conservative methods in treatment of the young patient with degenerative hip disease. Continuous research and referral of the young patients to dedicated centres is recommended.

Periprosthetic fracture of the femur is an uncommon complication after total hip replacement, but appears to be increasing. We undertook a nationwide observational study to determine the risk factors for failure after treatment of these fractures, examining patient- and implant-related factors, the classification of the fractures and the outcome.

Between 1979 and 2000, 1049 periprosthetic fractures of the femur were reported to the Swedish National Hip Arthroplasty Register. Of these, 245 had a further operation after failure of their initial management. Data were collected from the Register and hospital records. The material was analysed by the use of Poisson regression models.

It was found that the risk of failure of treatment was reduced for Vancouver type B2 injuries (p = 0.0053) if revision of the implant was undertaken (p = 0.0033) or revision and open reduction and internal fixation (p = 0.0039) were performed. Fractures classified as Vancouver type B1 had a significantly higher risk of failure (p = 0.0001). The strongest negative factor was the use of a single plate for fixation (p = 0.001). The most common reasons for failure in this group were loosening of the femoral prosthesis, nonunion and re-fracture.

It is probable that many fractures classified as Vancouver type B1 (n = 304), were in reality type B2 fractures with a loose stem which were not recognised. Plate fixation was inadequate in these cases. The difficulty in separating type B1 from type B2 fractures suggests that the prosthesis should be considered as loose until proven otherwise.

Aims: The aim of this study was to evaluate a highly cross-linked polyethylene WIAM in cemented hip arthroplasty. This new polyethylene has been resistant to wear in laboratory tests. Methods: 60 patients (30 women, 30 men) with a median age of 55 years (35–70) and a median weight 82 kg (47–120) were included. All patients received a Spectron femoral stem with a 28 mm head in chrome-cobalt. The patients were randomised to acetabular cups made of either WIAM (electron beam irradiation 9.5 Mrad) or conventional polyethylene (CP) sterilized in inert atmosphere. Radiostereometric examinations (supine) were done 7 days after the operation and after 3, 6 12 and 24 months. Examinations (standing) were performed at 3, 6 12 and 24 months. The migration of the femoral head centre in relation to the polyethylene marker represented the femoral head penetration. Results:. 43 hip (19 WIAM 24 CP) were available for 24 months FU. There were no differences in cup migrations between the two groups. The mean proximal penetration (supine and standing) was less than 0.2 mm at 24 months in both groups p> 0,06 Conclusions: The femoral head penetration during the first two years may be dominated by creep. There is tendency for lower proximal penetration at standing examination in the WIAM group. Futher studies and longer follow up is necessary until highly crosslink polyethylene can be recommended for general use.

Aims: In 1979 a national observation study of total hip arthroplasties was started in Sweden. The Swedish Hip Register describes the epidemiology of primary and revision surgery and identifies risk factors for failure. Every unit reports details concerning implants, surgical and cementing technique and revision procedures online via the Internet home page (www.jru.orthop.gu.se). Methods: Currently the register contains 203 625 primary total hip arthroplasties performed during 1979–2001 and 18 067 revision procedures. Revision is the failure endpoint definition and modified Kaplan-Meier statistics and Poisson models are used for survival analysis. Each hospital receive their results annually providing a system for continuous improvement. Results: The results show that serious complications have declined significantly despite an increasing number of patients at risk. The revision burden for cemented THR (94% of the implants are cemented) is only 7.5%, which is much lower than in other countries. Over the 22 year period revision for aseptic loosening has been reduced to one quarter. Demographics are important since male gender and young age significantly increase the risk for revision. Cementless implants have in general had a worse outcome than expected but improved during the last decade. Conclusion: Problem areas are the young population and revision surgery which must be improved. The revision burden is about two times higher in all other countries. This finding implies that the register is extremely cost-effective and the reduction in direct costs for the health care service in Sweden corresponds to approximately USD 140 millions over the last ten years.

The purpose of this study was to compare the 2D and 3D linear and volume wear readings of the three most commonly used methods for measuring polyethylene wear: the Livermore, Devane and Martell techniques. Inter-observer variation of measurements using the techniques of Devane and of Martell on conventional radiographs was also performed. The radiographs of 80 patients (mean age 60+/−10 yrs) who had a Harris-Galante I total hip arthroplasty were measured. Nine different reviewers for the Devane technique readings including Dr Devane and eight reviewers for the Martell technique readings including Dr Martell made blinded independent wear observations for each radiograph set. One reviewer measured the 20 annual linear wear rate for all radiograph sets using the 2D Livermore technique. Inter-observer variation as a function of patient, reviewer, and total variation was statistically assessed using variance component analysis. Mean wear measured using the Livermore technique was the same as with the Devane and Martell method, but with a greater variation. Comparison of the Devane and Martell method for patient STD, reviewer STD, error STD (multiple reviews of same radiographs), total STD (randomly picked reviewer), mostly show a mean 50% lower STD with the Devane technique. Correlation (correlation coefficient of two randomly selected reviewers) is significantly better with the Devane technique.

Introduction: In a pioneer study Oonishi et al (1988) found reduced socket wear with the use of polyethylene subjected to high radiation doses. This observation has stimulated the development of a new generation polyethylene. In addition to high radiation doses the plastic is also subjected to various types of heat treatment to reduce the amount of free radicals. The purpose of the present study is to evaluate one of the new highly cross-linked polyethylenes in a randomized controlled study of cemented THA. The hypothesis is that the improved wear resistance will reduce the prevalence of osteolytic lesions with long-term follow-up.

Methods and materials: Patients in clinical and radiographic need of a THR with non-inflammatory osteoarthritis of the hip were randomized in two groups. Group 1 received a cemented Weber cup (Sulzer®, Switzerland) made of highly cross-linked (WIAM) polyethylene, group 2 got a conventional cup. All patients received a cemented Spectron (Smith & Nephew, USA) with a 28mm cobalt-chromium head.

So far 15 patients, (6 male and 9 females) with a median age of 55 years (range 42–62) have been evaluated in group 1 and 14 (9 male and 5 females) with a median age of 55 years (range 45–70) in group 2. The penetration of the femoral heads has so far been measured postoperatively (all hips supine), after 3 month (17 hips supine and standing) and after 6 month (11 hips supine and standing) using radiostereometry.

Results: The median proximal and three-dimensional (3-D) penetration (total wear) 0–6 month (supine position) was almost equal in the two groups. Group 1 had a proximal penetration of 0.08 mm (range 0.00–0.17) and a total penetration of 0.11 mm (range 0.06–0.14). The corresponding values for group 2 were 0,10 mm (0.05–0.21) for proximal penetration and 0.13 mm (0.10–0.16) for total penetration. Between 3 and 6 month the penetration (median values) was 0.04 mm/0.10 mm (proximal/3-D) for group 1 and 0.07 mm/0.12 mm for group 2. With the patients standing we found a proximally migration of the socket (0–6 month) in group 1 of 0,08 mm (−0.07 – 0.21) and 0.12 mm (0.1–0.13) in group 2.

Discussion: Use of a highly cross-linked polyethylene in the socket did not influence the early penetration rate after THR. Early creep of the material is possible explanation.

1-year follow-up on approximately 50% of the patients will be presented at the meeting.

We revised 24 consecutive hips with loosening of the femoral stem using impaction allograft and a cemented stem with an unpolished proximal surface. Repeated radiostereometric examinations for up to two years showed a slow rate of subsidence with a mean of 0.32 mm (−2.0 to +0.31). Fifteen cases followed for a further year showed the same mean subsidence after three years, indicating stabilisation. A tendency to retroversion of the stems was noted between the operation and the last follow-up. Retroversion was also recorded when displacement of the stem was studied in ten of the patients after two years. Repeated determination of bone mineral density showed an initial loss after six months, followed by recovery to the postoperative level at two years. Defects in the cement mantle and malalignment of the stem were often noted on postoperative radiographs, but did not correlate with the degrees of migration or displacement. After one year, increasing frequency of trabecular remodelling or resorption of the graft was observed in the greater trochanter and distal to the tip of the stem. Cortical repair was noted distally and medially (Gruen regions 3, 5 and 6). Migration of the stems was the lowest reported to date, which we attribute to the improved grafting technique and to the hardness of the graft.

We assessed 100 patients with a primary total hip replacement using the Harris hip score and the Nottingham Health Profile at one, three and five years after operation. They were derived from two prospective randomised series of cemented and uncemented replacements.

Both scoring systems correlated highly and were each heavily influenced by the system of functional classification defined by Charnley. After five years both reflected the function of the implant and the general state of the patient. A higher degree of sensitivity is needed to show differences in the performance of an implant in the short and medium term. We do not yet have an ideal system of clinical assessment and the overall function must always be properly assessed.

We enrolled 98 patients (107 hips) with a mean age of 47 years (SD 8.6) into a prospective study of the Madreporic Lord THR; 34 hips had primary and 73 secondary osteoarthritis.

After ten years, the survival rate using revision as the endpoint for failure was 70% (±9) for the cup and 98% (±0.3) for the stem. The combined clinical and radiological survival rates were 46% (±11) and 81% (±10), respectively. Osteoporosis due to stress-shielding was observed in the proximal femur. Hips with radiologically dense bone postoperatively showed the most pronounced bone loss.

We recommend continued radiological follow-up of patients with this type of implant to allow revision to be performed before there is severe bony destruction of the pelvis.