Hip joint preservation remains a preferred treatment option for hips with mechanically correctable pathologies prior to the development of significant secondary arthrosis. The pathologies most amenable to joint preservation are hip dysplasia and femoroacetabular impingement. These pathologies sometimes overlap. Untreated acetabular dysplasia of modest severity, if left uncorrected, always leads to arthrosis. Acetabular dysplasia is best treated by periacetabular osteotomy, usually combined with arthrotomy for management of labral pathology and associated cam-impingement if present. Pre-operative variables associated with the best long-term outcomes include less secondary arthrosis, younger age, and concentric articular surfaces. Femoroacetabular impingement has become progressively recognised as perhaps the most common cause of secondary arthrosis. The etiology of impingement is multifactorial and includes both genetic factors and stresses experienced by the hip prior to cessation of growth. Cam impingement can be quantified by the alpha angle as measured on plain radiographs and radial MR sequences. Further, significant cam impingement is clearly associated with the development of osteoarthrosis. Treatment can be performed either by arthroscopic or open femoral head-neck osteochondroplasty. As with hip dysplasia, prognosis following treatment is correlated with the severity of preoperative secondary arthrosis but unfortunately impinging hips more commonly have some degree of arthrosis preop whereas dysplastic hips can become symptomatic with instability in the absence of arthrosis. The scientific basis for the treatment of pincer impingement is less strong. Unlike cam impingement and hip dysplasia, pincer impingement pathology in the absence of coxa profunda has not been correlated with arthrosis and so rim trimming with labral refixation is probably performed more often than is clinically indicated. Similarly, caution should be exercised when considering rim-trimming for protrusion since high central contact pressures due to an enlarged acetabular notch are not corrected by rim trimming. Overall, joint preserving surgery remains the preferred treatment for hips with mechanically correctable problems prior to the development of significant secondary arthrosis.
Ceramic-on-ceramic (COC) bearing surfaces have consistently demonstrated reliable clinical results with when coupled with appropriated designed femoral stems and acetabular shells. Ceramic bearing surfaces are highly wettable and display both boundary and hydrodynamic fluid-film lubrication modes, which lead to extremely low wear rates. Furthermore, COC bearing couples have been shown to exhibit virtually no risk of adverse biologic reaction and have not been associated with corrosion-induced adverse tissue reactions that occur with metal taper junctions, particularly head-neck taper junctions. The relative brittleness of ceramics initially was thought to be a major disadvantage; however, four decades of improvement in the manufacture of ceramics and rigorous proof testing has led an extremely low risk of fracture, perhaps lower than that for cross-linked polyethylene. More recently it has become increasing appreciated that nearly all revisions for squeaking have been restricted to specific designs and materials, including the use of a titanium elevated metal rim on the acetabular side, and more flexible femoral components made of a beta-titanium alloy (TMZF) which had thin necks and relative small tapers. Multiple clinical studies document excellent long-term survival of COC bearing couples in young patients with revision for any reason as the primary endpoint. Our own experience with 341 hips with 2 to 15 and average 9.1 year f/u demonstrates a 95% overall survivorship (revision for any reason) at 13 years in patients under 50 years of age at the time of surgery. By contrast, cross-linked polyethylene bearings have not been studied so carefully and have not been shown to be superior to ceramic-ceramic bearings in young patients. These bearing surfaces represent a very heterogeneous group of products, with varying degrees of cross-linking, post-irradiation processing methods, and additives. Cross-linked polyethylenes in general have a lower fatigue strength than conventional polyethylene and are prone to fracture, especially when thin material is subjected to high stress. Some types of cross-linked polyethylenes are prone to in vivo oxidation, leading to further mechanical compromise over time. Studies also demonstrate the absence of reduction in femoral head penetration or risk of osteolysis in heads 32mm and larger, which are commonly used today. The most recent cross-linked polyethylene products have the least clinical support for their use. The long-term biologic effects of the smaller HXLPE wear particles and newer additives, including the more recently added vitamin E compounds are unknown. Indeed, in vitro, the debris has been shown to be cytotoxic. There is a paucity of survivorship data for hips utilising HXLPE, especially in younger, more active individuals. For these reasons, we believe that the ceramic-ceramic bearings are the gold standard for THA in the young patient and that cross-linked polyethylene bearing are being continually changed and have little long term clinical outcomes data to support their use.
Cup malposition leads to increased incidences of dislocation, impingement, wear, and revision. The HipSextant navigation system is a smart mechanical navigation device designed to indicate correct cup orientation at surgery. The current study assesses the effect of deliberately mis-docking the device on clinical accuracy. Ten patients (5 men and 5 women) presenting for total hip arthroplasty were assessed. Planning for the HipSextant Navigation System (Surgical Planning Associates, Inc., Boston, MA) was performed as usual. This is done by first creating a 3D surface model from CT imaging, establishing an Anterior Pelvic Plane coordinate system, and then creating a patient-specific HipSextant coordinate system. This coordinate system is defined by three points. The first point, called the basepoint, is located just behind the posterior wall of the acetabulum a fixed distance above the infracotyloid notch. The second point is located on the lateral aspect of the anterior superior iliac spine. The third point is located on the surface of the ilium and equally distant from the other two points. These three points define a patient-specific coordinate system that is known relative to the APP. Clinically, the instrument is then docked according to the plan and two protractors on the top of the instrument allow a direction indicator to point in the direction of desired cup orientation. For each of the hips, after the HipSextant plan was created (Figure 1), two additional plans were created: one where the basepoint was docked 5 mm closer to and one 5 mm further from the infracotyloind notch. The effect of the deliberate mis-docking was measured in degrees of operative anteversion and operative inclination.Introduction:
Methods:
Wear, wear-associated osteolysis, and instability are the most common reasons for revision total hip arthroplasty. These failures have been shown to be associated with acetabular component malpositioning. However, optimal acetabular component orientation on a patient-specific basis is currently unknown. The current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips. Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 99 hips in 93 patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the acetabular component. Cup orientation was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray. Both absolute cup position relative to the APP and tilt-adjusted cup position1 were calculated.Introduction:
Methods:
Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. A recent study measuring cup orientation on conventional radiodiographs demonstrated an incidence of cup malpositioning of 50% according to the safe zone that they defined1,2. A prior study of 105 conventionally placed cups using CT demonstrated a cup malpositioning incidence of 74%3. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT. We have performed CT-based navigation of hip arthroplasty and revision arthroplasty on a routine basis since 2003 and also use CT imaging to quantify periprosthetic osteolysis. In our image database from these, we have identified 98 hips and y patients who had a previously conventionally-placed cup on CT imaging. For each hip, cup orientation was determined in operative anteversion and operative inclination (according to the definitions of Murray) using an application specific software application (HipSextant Research Application 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts). This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. A multiplanar reconstruction module allows for creation of a plane parallel with the opening plane of the acetabulum and subsequent calculation of plane orientation in the AP Plane coordinate space.Introduction:
Methods:
While more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned, traditional surgical navigation and robotoics have not been widely adopted. This may be due to the additional time, expense, and complexity associated with this technology. As an alternative, smart mechanical navigation instruments, adjusted on a patient-specific basis, have been introduced to address the problem of cup malorientation. The current study assesses the accuracy of acetabular component alignment using a mechanical navigation instrument. The acetabular component was aligned in 58 consecutive hips in 58 patients using the HipSextant Mechanical Navigation System (Surgical Planning Associates, Inc. Boston, MA). The technique involves using a patient-specific plan and associated software. In planning for surgery, CT data are used to create a 3D model and to define the anterior pelvic plane (APP). A patient-specific HipSextant docking coordinate system is then determined by three points: one just behind the posterior acetabular rim, a second on the lateral side of the ASIS, and a third on the surface of the ilium (Figure 1). The HipSextant itself has two adjustable orthogonal protractors (in-plane and off-plane angle) and two adjustable arms so that the instrument is adjusted for each patient based on their specific anatomy. The instrument docks directly to the pelvis so the recommended orientation of the acetabular component is based on the actual position of the pelvis at the time of component implantation. A direction indicator points in the direction of the planned cup orientation (Figure 2). Cup alignment was further enhanced with the use of a parallel guide to improve parallel visualization (Figure 3). Postoperative cup orientation was measured using a validated two-dimensional/three-dimensional matching method [3,5].Background:
Patients and Methods:
Conventional methods of aligning the acetabular component during hip arthroplasty and hip resurfacing often rely upon anatomic information available to the surgeon. Such anatomical information includes the transverse acetabular ligament and the locations of the pubis, ischium and ilium. The current study assesses the variation in orientation of the plane defined by the pubis, ischium and ilium on a patient-specific basis as measured by CT. To assess the reliability of anatomical landmarks in surgery, we assessed 54 hips in 51 patients (32 male, 22 female) who presented for CT-based surgical navigation of total hip arthroplasty. The HipSextant Research Application (version 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts) was used to perform the calculations. This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. Standardized points on the ilium, ischium, and pubis were entered. These three points defined a plane and the orientation of the plane in the AP Plane coordinate system was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray1.Introduction:
Methods:
Adverse Local Tissue Reactions (ALTR) have been reported in association with both wear and corrosion. Tissue reactions have been reported in association with corrosion at CoCr head-CoCr neck, CoCr head-TiAl6V4 neck, and CoCr modular neck on beta-titanium (TMZF) stem junctions. The current abstract reports on 3 cases of ALTR in association with CoCr modular necks on convention titanium (TiAl6V4) stem junctions. Case 1. A 67 year old male (87 kg, 1.73 m, BMI 29.1) presented with new onset hip irritation 11 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 95, CRP = 5, Cr level = 1.0, Co level = 4.1, leukocyte transformation testing = highly reactive to nickel. Hip aspiration was culture negative with 11,250 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the greater trochanter. Case 2. A 52 year old male (89 kg, 1.83 m, BMI 26.5) presented with new onset hip irritation 30 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 7, CRP = 5.4, Cr level = 2.1, Co level = 4.8, leukocyte transformation testing = reactive to nickel. Hip aspiration was culture negative with 3995 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas. Case 3. A 52 year old male (104 kg, 1.85 m, BMI 30.1) presented with new onset hip irritation 26 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 33, CRP = 34.9, Cr level = 1.0, Co level = 3.7, leukocyte transformation testing = no reactivity to any of the biomaterials. Hip aspiration was culture negative with 3,780 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas. All three of these patients are scheduled for revision surgery. All three had ceramic-ceramic bearings. We have experience with 1029 ceramic-ceramic THA with fixed neck conventional titanium and modular titanium neck implants with minimum 2 yr f/u and have never diagnosed an adverse reaction in any of these patients. It is possible that corrosion at the CoCr neck on TiAl6V4 stem junction is the root cause of these reactions. Although the incidence of diagnosed reactions is roughly 1%, it appears that the use of CoCr at any junction under significant mechanical stress can result in adverse local tissue reaction and therefore should either be avoided or used with great caution and compelling indications.Introduction
Discussion
Young patients have been reported to have a higher risk of revision following total hip arthroplasty (THA) than older cohorts, possibly to due higher activity and a higher incidence of deformity and prior surgery. Ceramic-on-ceramic bearing surfaces have been proposed for use in young and active individuals due to their low wear, low risk of adverse biologic reaction, and long-term survivorship. We assessed the clinical results and long-term survivorship of uncemented ceramic-on-ceramic THA in a young patient population. 341 total hip arthroplasties in 218 patients under 50 years of age at the time of surgery were performed were performed using alumina ceramic-on-ceramic bearings from August 1999 to April 2009 as part of a prospective nonrandomized study. All patients received uncemented acetabular components with flush-mounted acetabular liners using an 18 degree taper and uncemented femoral components. The average patient age at the time of surgery was 41.7 years (range 17.8–49.9 years). The minimum follow-up time was 2 years, (mean 9.1, range 2–13.9). We evaluated implant-related complications and performed Kaplan-Meier analyses to determine survivorship of the femoral and acetabular components with revision for any reason as the endpoint.Introduction:
Methods:
Conventional methods of aligning the acetabular component during hip arthroplasty and hip resurfacing often rely upon anatomic information available to the surgeon. Such anatomical information includes the transverse acetabular ligament and the locations of the pubis, ischium and ilium. The current study assesses the variation in orientation of the plane defined by the pubis, ischium and ilium on a patient-specific basis as measured by CT. To assess the reliability of anatomical landmarks in surgery, we assessed 54 hips in 51 patients (32 male, 22 female) who presented for CT-based surgical navigation of total hip arthroplasty. From a 3D model of each patient, standardised points for the anterior pelvic plane and landmarks on the ilium, ischium, and pubis were entered. The plane defined by the anatomical landmarks was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray.Introduction
Methods
The optimal acetabular component orientation in general or on a patient-specific basis is currently unknown. In order to answer this question, the current study uses CT to assess acetabular orientation in a group of unstable hips as compared to a control group of stable hips. Our institutional database of CT studies performed in the region of the hip beginning in February of 1998 (41,975 CT studies) was compared against our institutional database of revision total hip arthroplasties beginning in August of 2003 (2262 Revision THA) to identify CT studies of any hip treated for recurrent instability by revision of the acetabular component. Twenty hips in 20 patients with suitable CT studies were identified for the study group. Our control group consisted of 101 hips in patients who had CT studies either for computer-assisted surgery on the contralateral side or for assessment of osteolysis. Using the CT data, the AP plane (APP) was defined, supine pelvic tilt was measured, and cup orientation was calculated by fitting a best fit plane to 6 points on the rim of the acetabular component. Cup orientation was calculated in degrees of operative anteversion and operative inclination according to the definitions of Murray. Both absolute cup position relative to the APP and tilt-adjusted cup position were calculated.Introduction
Methods
Correct postoperative leg length restoration is among the most important goals of hip arthroplasty. Therefore, we developed, validated and clinically applied a novel software algorithm based on surgical navigation, which allows the surgeon to restore a defined femur position without establishing a femoral coordinate system or the hip joint center and measure the leg length accurately and simply. This new leg length algorithm was used in 154 hips (145 patients) that underwent CT-based computer-assisted THA (VectorVision Build 274 prototype; BrainLAB AG, Helmstetten, Germany) with a tissue preserving superior capsulotomy. Intraoperatively, a pelvic and a femoral dynamic reference bases (DRB) were applied and the anterior pelvic plane (APP) was set as the pelvic coordinate system. Then, the hip joint was put in a neutral position and this position, and the relative position of the femoral DRB relative to the pelvic DRB, was captured and stored by the navigation system. After implantation of the prosthesis the same above described femoral position with the same amplitude of flexion/extension, abduction/adduction and rotation was restored. Now, any resulting difference was due to linear changes. Validation of this new algorithm was performed by comparing the navigated results to measurements from calibrated antero-posterior pre- and postoperative radiographs. The radiographic results were compared to the mean leg length change measured with the navigation system.Introduction
Material and Methods
Cup malposition in hip arthroplasty and hip resurfacing is associated with instability, accelerated wear, and the need for revision. The current study similarly assesses the variation in cup position using conventional techniques as measured by CT. We have performed CT-based navigation of hip arthroplasty and revision arthroplasty on a routine basis since 2003 and also use CT imaging to quantify periprosthetic osteolysis. In our image database, we have identified 91 hips in 87 patients (51 female, 36 male) who had a previously conventionally-placed cup on CT imaging. For each hip, cup orientation was determined in operative anteversion and operative inclination (according to the definitions of Murray) using an application specific software application (HipSextant Research Application 1.0.7, Surgical Planning Associates Inc., Boston, Massachusetts). This application allows for determination of the Anterior Pelvic Plane coordinates from a 3D surface model. A multiplanar reconstruction module allows for creation of a plane parallel with the opening plane of the acetabulum and subsequent calculation of plane orientation in the AP Plane coordinate space.Introduction
Methods
Acetabular component malalignment remains the since greatest root cause for revision THA with malposition of at least ½ of all acetabular component placed using conventional methods1. The use of local anatomical landmarks has repeatedly proven to be an unreliable. The reason for this is that the position of local anatomical landmarks varies widely from one patient to another. Another alternative is to simply place acetabular components in a supine position. Unfortunately, cups placed in the supine position under fluoroscopy had the highest incidence of cup malposition in the Callanan study. This is because acetabular anteversion is critically important and pelvic tilt during surgery in the supine position is unknown, uncontrolled, and not correlated with post-operative pelvic tilt. Image-free surgical navigation can be useful for cup alignment in the absence of pelvic deformity. Image-based surgical navigation can be effective for cup alignment in the presence or absence of pelvic deformity. Unfortunately, while these technologies have been available for a decade, few surgeons employ these technologies. This is likely due to added time, complexity, and expense. Current robotic technology embodies all of these limitations in an even more extreme form. The HipSextant is a smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment. The system is image based (CT or MR) and can handle extreme asymmetry and deformity. The instrument docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. Since the planning is provided, the surgeon needs to only review and adjust the plan as desired. Further the system is robust, showing greater accuracy than image-based traditional navigation. Finally, the system takes typically only 3 minutes to use, making it practical for busy practices and hospitals.
Indications for removal of well-fixed cementless femoral components include infection, improper femoral height/offset/anteversion, and fracture. More recently, removal of well-fixed but recalled femoral components that are associated with adverse local tissue reaction (ALTR) has created a new indication for this procedure. The goal in all cases is to preserve bone stock and soft-tissue attachments to the greatest extent possible during implant removal. The strategy for implant removal depends to a large extent on the type of implant to be removed. Implants with limited proximal fixation can often be removed from the top using narrow osteotomes. Implants with more extensive fixation typically require more extensive exposure. When performing an extended trochanteric osteotomy, plan for the bone flap length based on measurement from the tip of the greater trochanter. Instead of devascularising the lateral bone flap, be sure to preserve the quadriceps attachment to the bone flap, exposing the lateral femur only where the transverse and posterior osteotomies are planned. The anterior osteotomy can be performed using a dotted line of osteotomes trans-muscularly as described by Heinz Wagner. Placement of a prophylactic cerclage below the osteotomy is prudent. Most importantly, if the need for a transfemoral exposure is likely, it should be performed primarily so that the posterior capsule and short rotators can be preserved. There is no need to perform a full posterior exposure and then to secondarily perform a transfemoral exposure since the former is unnecessary if the latter is performed. Discrete, limited fixation of the lateral bone flap proximally and distally should be performed to prevent strangulation of the living bone flap during the refixation process. The transfemoral technique can be applied not only to removal of well-fixed devices but also for conversion from hip fusion and for Z-shortening of the femur during Crowe 4 reconstruction instead of using a transverse osteotomy and intercalary shortening.
Distal neck modularity places a modular connection at a mechanically critical location. However, this is also the location that confers perhaps the greatest clinical utility. Assessment of femoral anteversion in 342 of our THR patients by CT showed a range from −24 to 61 degrees. The use of monoblock stems in some of these deformed femurs therefore must result in a failure to appropriately reconstruct the hip and have increased risks of impingement, instability, accelerated bearing wear or fracture, and adverse local tissue reaction (ATLR). However, the risks of failing to properly reconstruct the hip without neck modularity must be weighed against the additional risks introduced by neck modularity. There are several critical design, material, and technique variables that are directly associated with higher or lower incidences of problems associated with modular neck femoral components. These include modular neck length, design and material of both parts including the junction design, wall thickness of the receiving junction, assembly force, and bearing diameter and material. With regard to stem design and material, it has been clearly shown that the incidence of titanium neck fractures is higher in stems with a thinner wall-thickness of the receiving junction than in stems with a thicker wall-thickness. Moreover, titanium necks have been largely replaced with CoCr necks with significantly higher yield and fatigue strength. It remains to be seen if the introduction of CoCr necks will decrease or increase the risks associated with distal neck modularity. With respect to titanium necks, our experience has shown no adverse local tissue reaction, no fractures of short necks (0 of 370) and a 0.34% incidence of fractures in long necks (2/580) at 3 to 8 years following surgery. This lower incidence of neck fracture compared to other reports may relate to the relatively more rigid stem and thicker wall of the junction receiving the neck compared to other stems. With respect to CoCr modular necks, one device that mated the CoCr modular neck with a beta-titanium alloy femoral component has been shown to have a high incidence of ALTR and has been recalled. While the CoCr on Conventional Titanium Alloy modular neck experience has had a statistically significantly lower incidence of problems, we believe that we have identified two cases of ALTR. If that is the case, the CoCr neck experience may well have a higher incidence of problems that the Ti neck experience. In summary, placing a modular connection at the stem-neck junction has great clinical utility but this is a very design sensitive location. There are risks associated with the use of non-modular neck components that are incapable of properly reconstructing the spectrum of pathology that presents. This failure can lead to instability, impingement, and polyethylene fracture. Yet, the use of titanium modular necks has a small risk of component fracture while the use of cobalt-chrome modular necks may have a higher risk of adverse local tissue reaction. While the existence of a modular neck may offer great advantages at the time of primary reconstruction and of future revision, currently the risk/benefit for the use of these components is strongest in patients with more significant anatomical abnormalities or more complex revision settings.
Young patients have been reported to have a higher risk of revision following total hip arthroplasty than older cohorts. This was attributed to the higher activity level which led to increased wear, osteolysis, and component fracture. We prospectively assessed the clinical results, wear and osteolysis, the incidence of squeaking, and the survivorship of ceramic on ceramic THA in patients younger than 50 years (mean age of 42 [18–50] years). The series included 425 THAs in 370 patients with 368 hips followed for a minimum of 2 years (mean 7.1 years, range 2–14 years). All patients received uncemented acetabular components with flush-mounted acetabular liners using an 18 degree taper. No osteolysis was observed in any uncemented construct. There was osteolysis around one loose cemented femoral component. The survivorship for reoperation for implant revision was 96.7%. There were only two acetabular liner fractures (0.47%) and one femoral head fracture (0.24%). Two of the three fractures involved a fall from a significant height. There were no hip dislocations. Five patients (1.17%) noted rare or occasional squeaking. None had reproducible squeaking. In summary, the current study shows that ceramic-on-ceramic THAs in the young patient population are extremely reliable with a very low revision rate and an absence of wear-induced osteolysis. In addition, it shows that both bearing fracture in this young patient population typically occurs with polytrauma and squeaking issues that have been raised relative to ceramic bearings occur very rarely with the flush-mounted ceramic liner design used in this study.
Early rehabilitation and discharge following minimally-invasive total hip arthroplasty has potential risks including the possibility that patients may become progressively anemic at home. The current study assess the use of pre-emptive autologous blood transfusion on the length of stay, readmission, and allogenous transfusion. Patients treated by primary total hip arthroplasty using the superior capsulotomy technique were studied. Patients were divided into two groups. Group 1 were patients who did donate autologous blood and received an intra-operative pre-emptive transfusion. There were 283 patients in Group 1. Group 2 were patients who were medically capable of donating autologous blood but did not for non-medical reasons. There were 71 patients in Group 2. Patients who did not donate autologous blood for medical reasons (preoperative Hgb less than 11.5, age over 80) were excluded. All patients received general anesthesia. Length of stay, allogenous transfusion and readmission were compared.Introduction
Methods
Half of all acetabular components placed using conventional methods are malpositioned1. The HipSextant™ Navigation System (Surgical Planning Associates, Boston, MA) is a mechanical navigation system, adjusted on a patient-specific basis, designed to achieve appropriate cup alignment as simply and rapidly as possible. The current study assesses the surgeon's ability to register and track the pelvis and align the cup using the system. A bioskills model pelvis (Pacific Research Laboratories, Inc., Vashon, WA) was prepared by placing screws to mark the anterior pelvic plane points and by inserting a long cup alignment pin, simulating a cup insertion handle, into the acetabulum. The bone model was then scanned using CT. The HipSextantTM Navigation System Planning Application was then used to plan the use of the HipSextant for the surgery. This is accomplished by creating a 3D model, designating the AP plane (marked by the screws), and then determining the HipSextant docking points. One of these three points is behind the posterior wall of the acetabulum (the basepoint). The second of these three points is on the lateral aspect of the anterior superior iliac spine. The third point, the landing point, is located on the surface of the ilium and equally distant from the other two points (Figure 1). The two protractors on the HipSextant planning application were then adjusted to be parallel with the cup alignment pin on the bone model. A surgeon and assistant were then asked to dock the HipSextant on the bone model and to visually align the direction indicator to be parallel with the cup alignment pin. The two protractor angles on the instrument were recorded. This allowed for calculation of error in operative anteversion and operative inclination between the plan and the actual alignment that was accomplished. Four pairs of surgeon and assistant each performed the docking and alignment procedure 10 times for a total of 40 measurements.Introduction
Methods
The current study reports on the impact of immediate mobilization of patients treated by tissue-preserving, computer-assisted total hip arthroplasty on length of stay, disposition, and complications. From March, 2010 to April, 2011, a total of 231 consecutive primary THA were performed. Of these, 218 hips met the inclusion criteria of treatment using the superior capsulotomy surgical technique1 (Fig. 1), navigation of acetabular component implantation using a patient-specific mechanical navigation device (HipSextant™ navigation System, Surgical Planning Associates, Inc., Boston, MA)2, and patient age less than 80 years. Mean age of the patients was 57.3 years (range 23.5–79.9 years). The superior capsulotomy approach1 was used in all cases. This technique allows for both the femoral and the acetabular components to be placed with the patient in a lateral position through an incision in the superior capsule, posterior to the abductors and anterior to the short external rotators. The hip is not dislocated during surgery. Rather, the femur is prepared in situ through the top of the femoral neck, the neck is then transected, and the femoral head is excised en bloc. The acetabulum is prepared under direct vision using angled reamers, and the socket is placed with an offset inserter. The final construct is then reduced in situ. The protocol also involved the use of pre-emptive oral analgesia, pre-emptive autologous blood transfusion, and immediate mobilization3. Length of stay and disposition in this study group were compared to a cohort of 698 total hip arthroplasty performed at the same institution by all other techniques.Introduction
Methods
