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Case: Salvage of 2 cases of distal femoral replacement loosening with massive osteolysis using impaction grafting are presented with 9- and 11-year follow-ups., Conclusion: Surgeons should keep impaction grafting in their armamentarium for cases of failed DFR with severe osteolysis. Doing so may allow for preservation of the native hip and deferment of more radical procedures (i.e. total femur replacement) that have high rates of complication and poor survivorship.

Background: Use of large clinical and administrative databases for orthopaedic research has increased exponentially. Each database represents unique patient populations and varies in their methodology of data acquisition, which makes it possible that similar research questions posed to different databases might result in answers that differ in important ways., Questions/purposes: (1) What are the differences in reported demographics, comorbidities, and complications for patients undergoing primary TKA among four databases commonly used in orthopaedic research? (2) How does the difference in reported complication rates vary depending on whether only inpatient data or 30-day postoperative data are analyzed?, Methods: Patients who underwent primary TKA during 2010 to 2012 were identified within the National Surgical Quality Improvement Programs (NSQIP), the Nationwide Inpatient Sample (NIS), the Medicare Standard Analytic Files (MED), and the Humana Administrative Claims database (HAC). NSQIP is a clinical registry that captures both inpatient and outpatient events up to 30 days after surgery using clinical reviewers and strict definitions for each variable. The other databases are administrative claims databases with their comorbidity and adverse event data defined by diagnosis and procedure codes used for reimbursement. NIS is limited to inpatient data only, whereas HAC and MED also have outpatient data. The number of patients undergoing primary TKA from each database was 48,248 in HAC, 783,546 in MED, 393,050 in NIS, and 43,220 in NSQIP. NSQIP definitions for comorbidities and surgical complications were matched to corresponding International Classification of Diseases, 9 Revision/Current Procedural Terminology codes and these coding algorithms were used to query NIS, MED, and HAC. Age, sex, comorbidities, and inpatient versus 30-day postoperative complications were compared across the four databases. Given the large sample sizes, statistical significance was often detected for small, clinically unimportant differences; thus, the focus of comparisons was whether the difference reached an absolute difference of twofold to signify an important clinical difference., Results: Although there was a higher proportion of males in NIS and NSQIP and patients in NIS were younger, the difference was slight and well below our predefined threshold for a clinically important difference. There was variation in the prevalence of comorbidities and rates of postoperative complications among databases. The prevalence of chronic obstructive pulmonary disease (COPD) and coagulopathy in HAC and MED was more than twice that in NIS and NSQIP (relative risk [RR] for COPD: MED versus NIS 3.1, MED versus NSQIP 4.5, HAC versus NIS 3.6, HAC versus NSQIP 5.3; RR for coagulopathy: MED versus NIS 3.9, MED versus NSQIP 3.1, HAC versus NIS 3.3, HAC versus NSQIP 2.7; p < 0.001 for all comparisons). NSQIP had more than twice the obesity as NIS (RR 0.35). Rates of stroke within 30 days of TKA had more than a twofold difference among all databases (p < 0.001). HAC had more than twice the rates of 30-day complications at all endpoints compared with NSQIP and more than twice the 30-day infections as MED. A comparison of inpatient and 30-day complications rates demonstrated more than twice the amount of wound infections and deep vein thromboses is captured when data are analyzed out to 30 days after TKA (p < 0.001 for all comparisons)., Conclusions: When evaluating research utilizing large databases, one must pay particular attention to the type of database used (administrative claims, clinical registry, or other kinds of databases), time period included, definitions utilized for specific variables, and the population captured to ensure it is best suited for the specific research question. Furthermore, with the advent of bundled payments, policymakers must meticulously consider the data sources used to ensure the data analytics match historical sources., Level of Evidence: Level III, therapeutic study.

Background: Short stem cementless femoral components were developed to aid insertion through smaller incisions, preserve metaphyseal bone, and potentially decrease or limit the incidence of thigh pain. Despite some clinical success, the senior author (DDG) believed a higher percentage of his patients who had received a cementless short stem design were experiencing thigh pain, which, coupled with concerns about bone ingrowth fixation, motivated the review of this case series., Questions/purposes: (1) What is the proportion of patients treated with a short stem cementless THA femoral component that develop thigh pain and what are the hip scores of this population? (2) What are the radiographic results, specifically with respect to bone ingrowth fixation and stress shielding, of this design? (3) Are there particular patient or procedural factors that are associated with thigh pain with this short stem design?, Methods: Two hundred sixty-one primary THAs were performed in 238 patients by one surgeon between November 2010 and August 2012. During this time period, all patients undergoing primary THA by this surgeon received the same cementless short titanium taper stem. Seven patients (eight hips) died and five patients (five hips) were lost to followup, leaving 226 patients (248 hips) with a mean followup of 3 years (range, 2-5 years). Patients rated their thigh pain during activity or rest at final followup on a 10-point visual analog scale. Harris hip scores (HHS) were obtained at every clinic appointment. Thigh pain was evaluated at the final followup or by contacting the patient by phone. Radiographs were evaluated for bone-implant fixation, bone remodeling, and osteolysis. An attempt was made to correlate thigh pain with patient demographics, implant specifications, or radiographic findings., Results: Seventy-six percent of hips (180 of 238) had no thigh pain, 16% of hips (37 of 238) had mild thigh pain, and 9% (21 of 238) had moderate or severe thigh pain. Preoperatively, mean HHS was 47 (SD, 16) and at last followup, mean HHS was 88 (SD, 13). There were two femoral revisions, one for severe thigh pain and the other for infection. All but two components demonstrated bone ingrowth fixation (99%). Femoral stress shielding was mild in 64% of hips (135 of 212), moderate in 0.5% (one of 212), and severe in no hips. There is an inverse linear relationship between age and severity of thigh pain (r = -0.196; p < 0.0024)., Conclusions: Although reliable fixation was achieved and good HHS were attained, the frequency and severity of thigh pain with this short cementless stem were concerning. The surgeon has subsequently abandoned this short stem design and returned to a conventional length stem. Future study direction might investigate the biomechanical grounds for the thigh pain associated with this stem design., Level of Evidence: Level IV, therapeutic study.

Background: Infection after total knee arthroplasty (TKA) can result in disastrous consequences. Previous research regarding injections and risk of TKA infection have produced conflicting results and in general have been limited by small cohort size., Questions/purposes: The purpose of this study was to evaluate if intraarticular injection before TKA increases the risk of postoperative infection and to identify if time between injection and TKA affect the risk of TKA infection., Methods: The Humana data set was reviewed from 2007 to 2014 for all patients who received a knee injection before TKA. Current Procedural Terminology (CPT) codes and laterality modifiers were used to identify patients who underwent knee injection followed by ipsilateral TKA. Postoperative infection within 6 months of TKA was identified using International Classification of Diseases, 9 th Revision/CPT codes that represent two infectious endpoints: any postoperative surgical site infection (encompasses all severities of infection) and operative intervention for TKA infection (surrogate for deep TKA infection). The injection cohort was stratified into 12 subgroups by monthly intervals out to 12 months corresponding to the number of months that had elapsed between injection and TKA. Risk of postoperative infection was compared between the injection and no injection cohorts. In total, 29,603 TKAs (35%) had an injection in the ipsilateral knee before the TKA procedure and 54,081 TKA cases (65%) did not. The PearlDiver database does not currently support line-by-line output of patient data, and so we were unable to perform a multivariate analysis to determine whether other important factors may have varied between the study groups that might have had a differential influence on the risk of infection between those groups. However, the Charlson Comorbidity index was no different between the injection and no injection cohorts (2.9 for both) suggesting similar comorbidity profiles between the groups., Results: The proportion of TKAs developing any postoperative infection was higher among TKAs that received an injection before TKA than in those that did not (4.4% versus 3.6%; odds ratio [OR], 1.23; 95% confidence interval [CI], 1.15-1.33; p < 0.001). Likewise, the proportion of TKAs developing infection resulting in return to the operating room after TKA was also higher among TKAs that received an injection before TKA than those that did not (1.49% versus 1.04%; OR, 1.4; 95% CI, 1.3-1.63; p < 0.001). Month-by-month analysis of time between injection and TKA revealed the odds of any postoperative infection remained higher for the injection cohort out to a duration of 6 months between injection and TKA (ORs ranged 1.23 to 1.46 when 1-6 months between injection and TKA; p < 0.05 for all) as did the odds of operative intervention for TKA infection when injection occurred within 7 months of TKA (OR ranged from 1.38 to 1.88 when 1-7 months between injection and TKA; p < 0.05 for all). When the duration between injection and TKA was longer than 6 or 7 months, the ORs were no longer elevated at these endpoints, respectively., Conclusions: Injection before TKA was associated with a higher risk of postoperative infection and appears to be time-dependent with closer proximity between injection and TKA having increased odds of infection. Further research is needed to better evaluate the risk injection before TKA poses for TKA infection; a more definitive relationship could be established with a multivariate analysis to control for other known risk factors for TKA infection., Level of Evidence: Level III, therapeutic study.

Background: A patient who dies during the followup period of a study about total hip arthroplasty (THA) cannot subsequently undergo a revision. The presence of competing events (such as deaths, in a study on implant durability) violates an assumption of the commonly used Kaplan-Meier (KM) survivorship approach. In that setting, KM-based estimates of revision frequencies will be high relative to alternative approaches that account for competing events such as cumulative incidence methods. However, the degree to which this difference is clinically relevant, and the degree to which it affects different ages of patient cohorts, has been poorly characterized in orthopaedic clinical research., Questions/purposes: The purpose of this study was to compare KM with cumulative incidence survivorship estimators to evaluate the degree to which the competing event of death influences the reporting of implant survivorship at long-term followup after THA in patients both younger than and older than 50 years of age., Methods: We retrospectively reviewed 758 cemented THAs from a prospectively maintained single-surgeon registry, who were followed for a minimum of 20 years or until death. Revision rates were compared between those younger than or older than age 50 years using both KM and cumulative incidence methods. Patient survivorship was calculated using KM methods. A total of 21% (23 of 109) of the cohort who were younger than 50 years at the time of THA died during the 20-year followup period compared with 72% (467 of 649) who were older than 50 years at the time of surgery (p < 0.001)., Results: In the cumulative incidence analysis, 19% of the younger than age 50 years cohort underwent a revision for aseptic causes within 20 years as compared with 5% in the older than age 50 years cohort (p < 0.001). The KM method overestimated the risk of revision (23% versus 8.3%, p < 0.001), which represents a 21% and 66% relative increase for the younger than/older than age 50 years groups, respectively., Conclusions: The KM method overestimated the risk of revision compared with the cumulative incidence method, and the difference was particularly notable in the elderly cohort. Future long-term followup studies on elderly cohorts should report results using survivorship curves that take into account the competing risk of patient death. We observed a high attrition rate as a result of patient deaths, and this emphasizes a need for future studies to enroll younger patients to ensure adequate study numbers at final followup., Level of Evidence: Level III, therapeutic study.

Background: Cemented femoral total hip arthroplasty may be one of the most successful surgical interventions of all time. However, although results are very encouraging over the early to mid-term followup, relatively few studies have analyzed the durability of these implants beyond 20 years followup. To evaluate the performance of contemporary implants, it is important to understand how previous implants perform at 20 or more years of followup; one way to do this is to aggregate the available data in the form of a systematic review., Questions/purposes: (1) How durable is cemented femoral fixation in the long term (minimum 20-year followup) with respect to aseptic loosening? (2) Is the durability of cemented femoral fixation dependent on age of the patient? (3) Are the long-term results of the cemented femoral fixation dependent on any identifiable characteristics of the prosthesis such as surface finish?, Methods: A systematic review was performed to identify long-term studies of cemented femoral components. After application of inclusion and exclusion criteria to 1228 articles found with a search in PubMed and EMBASE, 17 studies with a minimum of 20-year followup on cemented femoral components were thoroughly analyzed in an attempt to answer the questions of this review. The quality of the studies reviewed was assessed with the Methodological Index for Nonrandomized Studies (MINORS) instrument. All studies were case series and cohort sizes ranged from 110 to 2000 hips for patients older than 50 years of age and 41 to 93 hips for patients younger than 50 years at the time of surgery., Results: Among the six case series performed in patients older than 50 years of age, survivorship for aseptic loosening of the femoral component ranged from 86% to 98% at 20 years followup. There were no obvious differences for younger patients when analyzing the five studies in patients younger than age 50 years in which survivorship free from aseptic loosening for these studies ranged from 77% at 20 years in one study and 68% to 94% at 25 years in the other studies. Although data pooling could not be performed because of heterogeneity of the studies included here, it appeared that stems with a rougher surface finish did not perform as well as polished stems; survivorship of stems with rougher surface finishes varied between 86% and 87%, whereas those with smoother finishes ranged between 93.5% and 98% at 20 years., Conclusions: Excellent long-term fixation in both older and younger patients can be obtained with cemented, polished femoral stems. These results provide material for comparison with procedures performed with newer cementing techniques and newer designs, both cemented and cementless, at this extended duration of followup.

Background: Positioning of total hip bearings involves tradeoffs, because cup orientations most favorable in terms of stability are not necessarily ideal in terms of reduction of contact stress and wear potential. Previous studies and models have not addressed these potentially competing considerations for optimal total hip arthroplasty (THA) function., Questions/purposes: We therefore asked if component positioning in total hips could be addressed in terms of balancing bearing surface wear and stability. Specifically, we sought to identify acetabular component inclination and anteversion orientation, which simultaneously resulted in minimal wear while maximizing construct stability, for several permutations of femoral head diameter and femoral stem anteversion., Methods: A validated metal-on-metal THA finite element (FE) model was used in this investigation. Five dislocation-prone motions as well as gait were considered as were permutations of femoral anteversion (0°-30°), femoral head diameter (32-48 mm), cup inclination (25°-75°), and cup anteversion (0°-50°), resulting in 4320 distinct FE simulations. A novel metric was developed to identify a range of favorable cup orientations (so-called "landing zone") by considering both surface wear and component stability., Results: When considering both wear and stability with equal weight, ideal cup position was more restrictive than the historically defined safe zone and was substantially more sensitive to cup anteversion than to inclination. Ideal acetabular positioning varied with both femoral head diameter and femoral version. In general, ideal cup inclination decreased with increased head diameter (approximately 0.5° per millimeter increase in head diameter). Additionally, ideal inclination increased with increased values of femoral anteversion (approximately 0.3° per degree increase in stem anteversion). Conversely, ideal cup anteversion increased with increased femoral head diameter (0.3° per millimeter increase) and decreased with increased femoral stem anteversion (approximately 0.3° per degree increase). Regressions demonstrated strong correlations between optimal cup inclination versus head diameter (Pearson's r=-0.88), between optimal cup inclination versus femoral anteversion (r=0.96), between optimal cup anteversion versus head diameter (r=0.99), and between optimal cup anteversion and femoral anteversion (r=-0.98). For a 36-mm cup with a 20° anteverted stem, the ideal cup orientation was 46°±12° inclination and 15°±4° anteversion., Conclusions: The range of cup orientations that maximized stability and minimized wear (so-called "landing zone") was substantially smaller than historical guidelines and specifically did not increase with increased head size, challenging the presumption that larger heads are more forgiving. In particular, when the cup is oriented to improve not only stability, but also wear in the model, there was little or no added stability achieved by the use of larger femoral heads. Additionally, ideal cup positioning was more sensitive to cup anteversion than to inclination., Clinical Relevance: Positioning THA bearings involves tradeoffs regarding stability and long-term bearing wear. Cup positions most favorable to minimization of wear such as low inclination and elevated anteversion were detrimental in terms of construct stability. Orientations were identified that best balanced the competing considerations of wear and stability.

Background: Many patients undergoing TKA have both knee and ankle pathology, and it seems likely that some compensatory changes occur at each joint in response to deformity at the other. However, it is not fully understood how the foot and ankle compensate for a given varus or valgus deformity of the knee., Questions/purposes: (1) What is the compensatory hindfoot alignment in patients with end-stage osteoarthritis who undergo total knee arthroplasty (TKA)? (2) Where in the hindfoot does the compensation occur?, Methods: Between January 1, 2005, and December 31, 2009, one surgeon (JJC) obtained full-length radiographs on all patients undergoing primary TKA (N=518) as part of routine practice; patients were analyzed for the current study and after meeting inclusion criteria, a total of 401 knees in 324 patients were reviewed for this analysis. Preoperative standing long-leg AP radiographs and Saltzman hindfoot views were analyzed for the following measurements: mechanical axis angle, Saltzman hindfoot alignment and angle, anatomic lateral distal tibial angle, and the ankle line convergence angle. Statistical analysis included two-tailed Pearson correlations and linear regression models. Intraobserver and interobserver intraclass coefficients for the measurements considered were evaluated and all were excellent (in excess of 0.8)., Results: As the mechanical axis angle becomes either more varus or valgus, the hindfoot will subsequently orient in more valgus or varus position, respectively. For every degree increase in the valgus mechanical axis angle, the hindfoot shifts into varus by -0.43° (95% confidence interval [CI], -0.76° to -0.1°; r=-0.302, p=0.0012). For every degree increase in the varus mechanical axis angle, the hindfoot shifts into valgus by -0.49° (95% CI, -0.67° to -0.31°; r=-0.347, p<0.0001). In addition, the subtalar joint had a strong positive correlation (r=0.848, r2=0.72, p<0.0001) with the Saltzman hindfoot angle, whereas the anatomic lateral distal tibial angle (r=0.450, r2=0.20, p<0.0001) and the ankle line convergence angle (r=0.319, r2=0.10, p<0.0001) had a moderate positive correlation. The coefficient of determination (r2) shows that 72% of the variance in the overall hindfoot angle can be explained by changes in the subtalar joint orientation., Conclusions: These findings have implications for treating patients with both knee and foot/ankle problems. For example, a patient with varus arthritis of the knee should be examined for fixed hindfoot valgus deformity. The concern is that patients undergoing TKA, who also present with a stiff subtalar joint, may have exacerbated, post-TKA foot/ankle pain or disability or malalignment of the lower extremity mechanical axis as a result of the inability of the subtalar joint to reorient itself after knee realignment. A prospective study is underway to confirm this speculation., Level of Evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background: Long-term evaluation of knee arthroplasty should provide relevant information concerning the durability and performance of the implant and the procedure. Because most arthroplasties are performed in older patients, most long-term followup studies have been performed in elderly cohorts and have had low patient survivorship to final followup; the degree to which attrition from patient deaths over time in these studies might influence their results has been poorly characterized., Questions/purposes: The purpose of this study was to examine the results at 20-year followup of two prospectively followed knee arthroplasty cohorts to determine the following: (1) Are there relevant differences among the two implant cohorts in terms of revision for aseptic causes (osteolysis, or loosening)? (2) How does patient death over the long followup interval influence the comparison, and do the comparisons remain valid despite the high attrition rates?, Methods: Two knee arthroplasty cohorts from a single orthopaedic practice were evaluated: a modular tibial tray (101 knees) and a rotating platform (119 knees) design. All patients were followed for a minimum of 20 years or until death (mean, 14.1 years; SD 5.0 years). Average age at surgery for both cohorts was >70 years. The indications for the two cohorts were identical (functionally limiting knee pain) and was surgeon-specific (each surgeon performed all surgeries in that cohort). Revision rates through a competing risks analysis for implants and survivorship curves for patients were evaluated., Results: Both of these elderly cohorts showed excellent implant survivorship at 20 years followup with only small differences in revision rates (6% revision versus 0% revision for the modular tibial tray and rotating platform, respectively). However, attrition from patient deaths was substantial and overall patient survivorship to 20-year followup was only 26%. Patient survivorship was significantly higher in patients<65 years of age in both cohorts (54% versus 15%, p<0.001 modular tray cohort, and 52% versus 26%, p=0.002 rotating platform cohort). Furthermore, in the modular tray cohort, patients<65 years had significantly higher revision rates (15% versus 3%, p=0.0019)., Conclusions: These two cohorts demonstrate the durability of knee arthroplasty in older patients (the vast majority older than 65 years). Unfortunately, few patients lived to 20-year followup, thus introducing bias into the analysis. These data may be useful as a reference for the design of future prospective studies, and consideration should be given to enrolling younger patients to have robust numbers of living patients at long-term followup., Level of Evidence: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background: Increasing national expenditures and use associated with TKA have resulted in pressure to reduce costs through various reimbursement cuts. However, within the arthroplasty literature, few studies have examined the association of medical comorbidities on resource use and length of stay after joint arthroplasty., Questions/purposes: The purpose of this study was to examine the association between individual patient characteristics (including demographic factors and medical comorbidities) on resource allocation and length of stay (LOS) after TKA., Methods: We queried the 2009 Nationwide Inpatient Sample dataset for International Classification of Diseases, 9(th) Revision code, 81.54, for TKAs. An initial 621,029-patient cohort was narrowed to 516,745 after inclusion of elective TKAs on patients aged between 40 and 95 years. Using generalized linear models, we estimated the effect of comorbidities on resource use (using cost-to-charge conversions to estimate hospital costs) and the LOS controlling for patient and hospital characteristics. Across the 2009 national cohort with TKAs, 12.7% had no comorbidities, whereas 32.6% had three or more. The most common conditions included hypertension (67.8%), diabetes (20.0%), and obesity (19.8%). Mean hospital costs were USD 14,491 (95% confidence interval [CI], 14,455-14,525) and mean hospital LOS was 3.3 days (95% CI, 3.29-3.31) in this data set., Results: Patients with multiple comorbidities were associated with increased resource use and LOS. Higher marginal costs and LOS were associated with patients who had an inpatient death (USD +8017 [95% CI, 8006-8028], +2.3 [CI, 2.15-2.44] days over baseline), patients with recent weight loss (USD +4587 [95% CI, 4581-4593], +1.5 [CI, 1.45-1.61) days], minority race (USD +1037 [95% CI, 1035-1038], +0.3 [CI, 0.28-0.33] days), pulmonary-circulatory disorders (USD +3218 [95% CI, 3214-3221], +1.3 [CI, 1.25-1.34] days), and electrolyte disturbances (USD +1313 [95% CI, 1312-1314], +0.6 [CI, 0.57-0.60] days). All p values were < 0.001., Conclusion: Multiple patient comorbidities were associated with additive resource use and LOS after TKA. Current reimbursement may not adequately account for these patient characteristics. To avoid potential loss of access to care for sicker patients, payment needs to be adjusted to reflect actual resource use., Level of Evidence: Level IV, economic and decision analysis. See the Instructions for Authors for a complete description of levels of evidence.

Background: Wear and corrosion in joint arthroplasty are important causes of failure. From the standpoint of current clinical importance, there are four main categories of wear and tribocorrosion: polyethylene wear, ceramic-on-ceramic (CoC) bearing wear, metal-on-metal (MoM) bearing wear, and taper tribocorrosion. Recently, problems with wear in the knee have become less prominent as have many issues with hip polyethylene (PE) bearings resulting from the success of crosslinked PE. However, MoM articulations and taper tribocorrosion have been associated with soft tissue inflammatory responses, and as a result, they have become prominent clinical concerns. WHERE ARE WE NOW?: For PE wear in the hip, several advances include improved locking mechanisms and data supporting highly crosslinked polyethylenes (HXLPE). Edge-loading in CoC articulations can contribute to stripe wear and subsequent squeaking. For MoM articulations, the relationship of wear-to-edge loading, sensitivity to component positioning, typical soft tissue response, and use of imaging is increasingly understood. Taper tribocorrosion (from femoral head-neck junctions and other modular elements) and associated soft tissue inflammatory responses appear to be serious clinical issues that are not fully understood. WHERE DO WE NEED TO GO?: In the knee, clinical concerns remain with the efficacy of HXLPE, modular connections, and metal allergies. For PE wear in the hip, concerns remain regarding how to increase crosslinking of PE while minimizing PE fractures. With CoC articulations, questions remain on how to prevent noises, chipping, and impingement and if enhanced designs can contribute to improved results. For MoM articulations, we need to improve imaging tests for soft tissue reactions, determine best practices in terms of monitoring protocols, and better define if, how, and when to act on serum metal levels. For taper tribocorrosion, we need to use modularity wisely and also understand how to improve tapers and materials in the future. For patients at risk for tribocorrosion, we need to define realistic diagnostic and monitoring protocols. We also need to enhance revision methods, and the threshold of acceptable soft tissue damage, to minimize complications associated with soft tissue damage such as hip instability. HOW DO WE GET THERE?: HXLPE and other bearing surfaces will likely continue to be refined. We need to develop tapers with more resistance to tribocorrosion through improved understanding of the manufacturing process and ongoing engineering improvements. Revision procedures for wear and tribocorrosion can be enhanced by determining when partial component retention is appropriate and how best to manage soft tissue damage. For CoC articulations, enhanced designs are required to minimize noises, chipping, and impingement. Importantly, we must continue to promote and analyze joint replacement registries to identify early failures and analyze long-term successes.

Background: Large-diameter femoral heads for metal-on-metal THA hold theoretical advantages of joint stability and low bearing surface wear. However, recent reports have indicated an unacceptably high rate of wear-associated failure with large-diameter bearings, possibly due in part to increased wear at the trunnion interface. Thus, the deleterious consequences of using large heads may outweigh their theoretical advantages., Questions/purposes: We investigated (1) to what extent femoral head size influenced stability in THA for several dislocation-prone motions; and the biomechanics of wear at the trunnion interface by considering the relationship between (2) wear potential and head size and (3) wear potential and other factors, including cup orientation, type of hip motion, and assembly/impaction load., Methods: Computational simulations were executed using a previously validated nonlinear contact finite element model. Stability was determined at 36 cup orientations for five distinct dislocation challenges. Wear at the trunnion interface was calculated for three separate cup orientations subjected to gait, stooping, and sit-to-stand motions. Seven head diameters were investigated: 32 to 56 mm, in 4-mm increments., Results: Stability improved with increased diameter, although diminishing benefit was seen for sizes of greater than 40 mm. By contrast, contact stress and computed wear at the trunnion interface all increased unabatedly with increasing head size. Increased impaction forces resulted in only small decreases in trunnion wear generation., Conclusions: These data suggest that the theoretical advantages of large-diameter femoral heads have a limit. Diameters of greater than 40 mm demonstrated only modest improvement in terms of joint stability yet incurred substantial increase in wear potential at the trunnion., Clinical Relevance: Our model has potential to help investigators and designers of hip implants to better understand the optimization of trunnion design for long-term durability.

Background: There are two unusual remodeling patterns of the proximal femur around well-fixed Charnley total hip arthroplasties: cortical thinning leading to endosteal widening around the femoral component and hypertrophy of the distal femoral cortex. Previous studies have shown remodeling patterns are affected by stem design and occur early postoperatively. It is unclear if these changes are related to patient demographics or if they progress throughout the lifetime of the implant., Questions/purposes: We determined if patient demographic variables influence remodeling patterns after cemented Charnley total hip arthroplasty and if the observed remodeling changes persist long-term., Methods: We retrospectively reviewed the radiographs of 106 well-fixed Charnley femoral components. Using a novel digital edge detection program, we determined the femoral remodeling pattern and time-related changes in femoral dimensions. The minimum followup was 20 years (mean, 25.3 years; range, 19.5-37 years)., Results: We found no association between remodeling type and age at surgery, sex, preoperative diagnosis, body mass index, or postoperative activity level. There was also no association between initial implant alignment and remodeling type. Cortical thickening in the distal hypertrophy group was an early phenomenon occurring primarily within the first 2 years, whereas cortical thinning begins later and is a more progressive process., Conclusions: These data show remodeling after cemented Charnley total hip arthroplasty is not related to patient demographic variables; however, distal cortical hypertrophy can be predicted in the early postoperative period.

Background: There is a paucity of literature concerning functional assessment at long-term followup of THAs in general and in young patients specifically. Functional data may be useful in determining differences in the performance of various implants and surgical techniques in THA., Questions/purposes: The purposes of this study were to evaluate a group of young patients who were still active 10 years after THA to determine (1) which functional tests and (2) which patient-reported outcome assessments predicted long-term THA function, as measured by acetabular UHMWPE wear, and (3) whether medical comorbidities influenced patient performance on activity tests and patient outcome questionnaires., Methods: Fifty patients (58 hips) 50 years and younger at the time of THA were followed clinically and radiographically for a minimum of 10 years. All patients wore step activity monitors for up to 21 days, performed 6-minute walk (6-MW) tests, and every patient had minimum 10-year radiographs and sequential radiographs evaluated for wear using edge detection techniques. Mean age and BMI at surgery were 39 years and 29 kg/m(2), respectively., Results: Patients who walked more as determined by step activity monitor (average daily steps) had more linear acetabular UHMWPE wear per year and more volumetric wear per year. The 6-MW, University of California Los Angeles (UCLA), and Tegner Lysholm scores did not correlate with acetabular wear. Mean 6-MW distance was 335 m and pedometer data averaged 1.56 million steps per year. Average UCLA and Tegner Lysholm scores were 6 and 3, respectively. Mean linear wear rate was 0.266 mm/year; mean volumetric wear rate was 82.6 mm(3)/year. The number of comorbid medical conditions had a detrimental effect on our activity parameters and outcomes questionnaires, but the relationships were not statistically significant., Conclusions: Of functional tools measured, only pedometer data correlated with THA polyethylene wear. Obtaining pedometer data should be considered when trying to distinguish differences in various hip arthroplasty designs and techniques over the long term.

Background: Obesity has reached epidemic proportions in the United States. Recently, obesity, especially morbid obesity, has been linked to increased rates of dislocation after THA. The reasons are unclear. Soft tissue engagement caused by increased thigh girth has been proposed as a possible mechanism for decreased joint stability., Questions/purposes: We asked (1) whether thigh soft tissue impingement could decrease THA stability, and if so, at what level of BMI this effect might become evident; and (2) how THA construct factors (eg, head size, neck offset, cup abduction) might affect stability in the morbidly obese., Methods: The obesity effect was explored by augmenting a physically validated finite element model of a total hip construct previously comprising just implant hardware and periarticular (capsular) soft tissue. The model augmentation involved using anatomic and anthropometric data to include graded levels of increased thigh girth. Parametric computations were run to assess joint stability for two head sizes (28 and 36 mm), for normal versus high neck offset, and for multiple cup abduction angles., Results: Thigh soft tissue impingement lowered the resistance to dislocation for BMIs of 40 or greater. Dislocation risk increased monotonically above this threshold as a function of cup abduction angle, independent of hardware impingement events. Increased head diameter did not substantially improve joint stability. High-offset necks decreased the dislocation risk., Conclusions: Excessive obesity creates conditions that compromise stability of THAs. Given such conditions, our model suggests reduced cup abduction, high neck offset, and full-cup coverage would reduce the risks of dislocation events.

Background: Hypothesized risk factors for fracture of ceramic liners include impingement, edge-loading, and cup malpositioning. These risk factors are similar to those for generation of stripe wear. However, it is unclear whether the biomechanical conditions contributing to stripe wear generation also increase the risk for ceramic liner fracture, Questions/purposes: We asked whether (1) head stripe wear propensity; and (2) cup orientation would correlate with alumina liner fracture risk for instances of normal and elevated body weight., Methods: An eXtended Finite Element Method (XFEM) model was developed to investigate these mechanisms. Liner fracture risk for 36-mm alumina bearings was studied by simulating two fracture-prone motions: stooping and squatting. Twenty-five distinct cup orientations were considered with variants of both acetabular inclination and anteversion. Four separate body mass indices were considered: normal (25 kg/m(2)) and three levels of obesity (33, 42, and 50 kg/m(2)). Material properties were modified to simulate alumina with and without the presence of dispersed microflaws. The model was validated by corroboration with two previously published ceramic liner fracture studies., Results: Of 200 XFEM simulations with flaw-free alumina, fracture occurred in eight instances, all of them involving obesity. Each of these occurred with cups in ≤ 37° inclination and in 0° anteversion. For 200 corresponding simulations with microflawed alumina, fracture propensity was greatest for cups with higher (edge loading-associated) scraping wear. Fracture risk was greatest for cups with lower inclination (average 42° for fractured cases versus 48° for nonfractured cases) and lower anteversion (9° versus 20°)., Conclusions: Fracture propensity for 36-mm liners was elevated for cups with decreased anteversion and/or inclination and under conditions of patient obesity., Clinical Relevance: Factors causing stripe wear, including obesity and cup malpositioning, also involve increased risk of ceramic liner fracture and merit heightened concern.

Background: Modular tibial trays have been utilized in TKA for more than 20 years. However, concerns have been raised about modular implants and it is unclear whether these devices are durable in the long term., Questions/purposes: We determined (1) survival, (2) relationship of age and polyethylene thickness with revision, (3) function, and (4) radiographic lucencies and osteolysis in patients having a single TKA implant at 20-year followup., Methods: We prospectively followed 75 patients implanted with 101 Press-Fit Condylar(®) (Johnson and Johnson Professional, Inc, Raynham, MA, USA) posterior cruciate-retaining TKAs (with modular tibial trays) between 1988 and 1991. At 20 years, 59 patients were deceased. We clinically evaluated the living 16 patients (22 knees) and contacted the relatives of all deceased patients to confirm implant status. We clinically assessed 14 of the 16 patients with the Knee Society score, WOMAC, and UCLA and Tegner activity level scores. Radiographically, we determined lucencies, component migration, and osteolysis. We performed survival analysis including all original patients. Minimum followup was 20 years (mean, 20.6 years; range, 20-21.8 years)., Results: Six reoperations were performed in five patients (6% rate of revision) over the 20-year followup. All revisions were related to polyethylene wear and occurred at least 10 years after the primary procedure. Survivorship with revision for any reason as the end point was 91% (95% CI, 0.83-0.97) at 20 years. Average Knee Society clinical and functional scores were 90 (range, 60-100) and 59 (range, 30-87), respectively., Conclusions: Our data demonstrate the durability of this posterior cruciate-retaining TKA design. The data provide a standard for newer designs and newer bearing surface materials at comparable followup.

Patient-reported outcome measures are an important component of outcomes assessment in clinical trials to assess the treatment of femoroacetabular impingement (FAI). This review of disease-specific measures and instruments used to assess the generic quality of life and physical activity levels of patients with FAI found no conclusive evidence to support a single disease-specific questionnaire. Using a systematic review of study methodology, the Copenhagen Hip and Groin Outcome Score and the 33-item International Hip Outcome Tool scored the best. Nevertheless, both of these instruments were developed recently and have not been established in the literature. Although currently used generic and activity-level measures have limitations, as well, they should be considered, depending on the specific goals of the study. Additional research is needed to assess the properties of these measures fully when used to evaluate patients with FAI.

Osteoarthritis (OA) is a common and disabling disease. Because of improved treatment of chronic diseases and lower mortality from infectious diseases, the US population is aging, and older Americans are living with disabling conditions, including hip OA. The projected number of older adults with arthritis or other chronic musculoskeletal joint symptoms is expected to nearly double, from 21.4 million in 2005 to 41.1 million by 2030. The burden of hip OA is increasing due to the aging population and the obesity crisis; as a result, the need for total hip arthroplasty (THA) is expected to grow 174%, to 572,000 primary THAs per year by 2030 in the United States. Prior projections appear to have underestimated the actual number of primary and revision THAs that are in demand.

Background: In a previous experiment studying cementation of liners into cementless acetabular shells, placing grooves in the liner in a spider-web configuration created the greatest construct strength. Scoring shells without screw holes or other texturing helped prevent failure at the shell-cement interface. However, it was unclear whether these practices caused durable constructs in patients., Questions/purposes: We therefore determined (1) rerevision rates; (2) functional scores (Harris hip scores, WOMAC, and SF-36); (3) acetabular loosening rates; and (4) acetabular osteolysis rates in patients in whom we cemented nonconstrained liners into well-fixed and well-positioned acetabular shells., Methods: We prospectively followed 30 patients with 31 total hip arthroplasties in which a worn acetabular liner was revised by cementing a new liner into the existing shell that was stable and well positioned. Acetabular liners were prepared as determined by our previous study. Twenty-seven of the 30 patients (28 hips) were evaluated clinically. We recorded revisions and determined radiographic loosening and osteolysis. The minimum clinical followup was 2 years (mean, 5.3 years; range, 2-10 years). Twenty-six hips (87%) had minimum 2-year radiographic followup with an average length of 4.8 years., Results: No hip required rerevision during the followup interval. Two hips (6%) dislocated once, both treated nonoperatively. Harris hip scores, WOMAC, and SF-36 scores increased over preoperatively at last followup. All acetabular shells and liners were radiographically stable without evidence of loosening or progressive acetabular osteolysis., Conclusions: Cementation of a liner into a well-fixed cementless shell after scoring in a spider-web configuration provided secure fixation with no failures of the construct at average 5.3 years followup., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The surgical management of end-stage hip disease in patients aged <30 years remains a challenge. Hip-preserving surgical procedures in the setting of advanced disease often do not provide adequate pain relief, but the implications of joint arthroplasty surgery in the very young patient are a matter of concern. The outcome of total hip arthroplasty (THA) in these patients varies, largely because of the wide spectrum of diagnoses associated with hip disease in this group, the complexity of deformities requiring THA, and the need for prolonged durability. The greatest number of THAs in this population is performed for secondary osteoarthritis or osteonecrosis, whereas most reports in the orthopaedic literature have focused on the outcomes of cemented THA in patients with juvenile rheumatoid arthritis. Given the frequent complexity of THA in the very young patient, special attention should be given to preoperative planning, implant selection, and patient education as well as to joint-preservation techniques to facilitate future hip arthroplasty surgery.

Background: Impingement events, in addition to their role immediately proximate to frank dislocation, hold the potential to damage new-generation hard-on-hard bearings as a result of the relatively unforgiving nature of the materials and designs. Because of the higher stiffness and tighter design tolerances of metal-on-metal and ceramic implants, surgical positioning plausibly has become even more important., Questions/purposes: We asked (1) whether, and under what cup orientation conditions, hard-on-hard impingements might challenge implant material failure strength; and (2) whether particle generation propensity at impingement and egress sites would show similar dependence on cup orientation., Methods: Realistic computational simulations were enabled by multistage finite element analyses, addressing both global construct motion and loading, and focal stress concentrations at neck impingement and rim egress sites. The global model, validated by a cadaveric simulation in a servohydraulic hip simulator, included both hardware components and advanced anisotropic capsule characterization. Parametric computational runs explored the effect of cup orientation for both ceramic-on-ceramic and metal-on-metal bearing couples for two distinct motion sequences associated with dislocation., Results: Stress concentrations from impingement increased nearly linearly with increased cup tilt and with cup anteversion. In some situations, peak values of stress approached or exceeded 1 GPa, levels challenging the yield strength of cobalt-chromium implants, and potentially the fracture strength of ceramics. The tendency for impingement events to generate debris, indexed in terms of a new scraping severity metric, showed orientation dependences similar to that for bulk material failure., Conclusions: Damage propensity arising from impingement events in hard total hip bearings is highly orientation-dependent.

Background: Most long-term followup studies of younger patients who underwent TKA include a relatively high percentage of rheumatoid patients, whose function and implant durability may differ from those with osteoarthritis (OA)., Questions/purposes: The purpose of this study was to evaluate the minimum 10 year followup of TKA performed in more active patients with OA, using modular tibial components, to determine the durability of that construct. Specifically, we determined (1) survivorship; (2) revision rates; (3) functional scores; and (4) rates of radiographic failure at a minimum 10 year followup., Methods: We retrospectively reviewed 59 patients (67 knees) with OA who underwent primary total knee arthroplasty with posterior cruciate retaining (27%) or posterior cruciate substituting (73%) components which had modular tibial trays. Patients were evaluated clinically for need of revision and Knee Society, SF-36 and WOMAC scores as well as UCLA and Tegner activity scores. Radiographs were evaluated for loosening and osteolysis. The minimum followup of living patients was 10 years (mean, 12.4 years; range, 10 to 18.4 years). Ten patients (11 knees) died; two patients (2 knees) were lost to followup., Results: Ten patients (11 knees; 16%) had revisions for aseptic loosening and/or osteolysis. Thirty-one patients (65%) were still performing moderate labor or sports activities. The average UCLA score was 5.5 (range, 2-9). No nonrevised knee demonstrated radiographic loosening., Conclusion: Most patients in this active patient population continued to have acceptable function although 16% underwent revision for wear and/or osteolysis. Isolated tibial insert exchange alone was performed in four of the 11 (36%) revised knees. These data should provide comparison for total knee arthroplasties performed in younger patients with newer designs and newer bearing materials., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background: Liner exchange and bone grafting are commonly performed for wear and osteolysis around well-fixed modular acetabular components that otherwise would require structural allografting and revision THA. However, liner exchange in the face of substantial lysis around TKA has been performed rarely with reports of failure rates of up to 25% at 3 year followup., Questions/purposes: We therefore evaluated the technique of liner exchange and bone grafting for cases of wear and extensive osteolysis around TKAs in which the components were well-fixed and well-aligned to determine (1) rerevision rates; (2) fate of the bone graft; (3) radiographic loosening rates; and (4) functional scores., Methods: We retrospectively reviewed 22 patients (25 knees) who underwent revision TKA with exchange of the modular polyethylene insert and bone grafting in cases with well-fixed components and large areas of osteolysis (up to 54 cm(2) on a single projection) at the time of revision. The average area of osteolysis was 21 cm(2) and 10 cm(2) on the AP projection of the femur and tibia, respectively. On the lateral projection, the average area of osteolysis for the femur and tibia was 22 cm(2) and 9.3 cm(2). Minimum clinical and radiographic followup was 22 and 22 months (average, 61 and 59; range, 22-142 and 22-130, respectively)., Results: One of the 25 knees was revised for aseptic loosening or recurrence of osteolysis. On radiographs, 84.6% and 70% of femoral and tibial osteolytic lesions, respectively, showed evidence of complete or near complete graft incorporation. The remaining lesions showed evidence of partial graft incorporation with the exception of one tibial lesion, which was in the revised case. All other components were well fixed with no evidence of radiographic loosening., Conclusions: In this selected series of cases with extensive osteolysis around well-fixed and well-aligned TKAs, liner exchange and bone grafting provided durable midterm results with extensive graft incorporation., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Background: The treatment of end-stage hip disease in very young patients is controversial, with advocates for nonoperative treatment, hip arthrodesis and replacement procedures. The functional improvements in this group of patients are not well documented and whether the condition for which the surgery is performed influences function., Questions/purposes: We determined whether (1) modern THA provides major functional improvements; (2) disease-specific factors impact the magnitude of improvement; (3) these procedures are associated with early failures and complications; and (4) radiographically secure implant fixation is achieved with contemporary implants., Methods: We retrospectively reviewed 88 patients (102 hips) who had THA and were 25 years or younger at surgery. The most common diagnoses were osteonecrosis (44%) and secondary osteoarthritis (41%). All patients received a cementless socket of varying designs and all except five a cementless stem. Demographic data, Harris hip score, and Charnley classification were recorded. Radiographic evaluation was used to determine implant fixation. We identified complications and failure mechanisms. The minimum followup was 2 years (median, 4.2 years; range, 2-16 years)., Results: The 95 nonrevised hips were followed clinically an average of 61 months. The mean Harris hip scores improved from 42 preoperatively to 83 postoperatively. Lower Harris hip scores were associated with systemic disease (Charnley Class C). Seven hips (7%) underwent revision. There were nine (9%) major complications. One hundred percent of femoral stems and 98% of acetabular components were well-fixed at last followup., Conclusion: Contemporary total hip arthroplasty in patients 25 years of age and younger is associated with improved hip function, and secure fixation of cementless implants at early followup.

Background/rationale: A 10-year survivorship of 100% was reported for patients with PFC cruciate-retaining prostheses. Beyond 10 years, we observed additional polyethylene wear likely related to thin liners gamma-irradiated in air and were concerned this wear might predispose to implant construct failure., Questions/purposes: We therefore determined (1) the functional scores at a minimum of 15 years followup, (2) rates of radiographic failure, (3) overall revision rates, and (4) mode of failure after 10 years and the fate of the revised implants., Methods: We retrospectively reviewed 75 patients with 101 press-fit condylar posterior cruciate-retaining prostheses. At a minimum followup of 15 years, 35 patients (47 knees) were living and evaluated clinically. No patients were lost to followup., Results: There were no revisions during the first 11 years and six reoperations subsequently were performed in five patients (6% overall rate of revision but 12.8% in patients who survived more than 15 years). Three of six revisions had concerning liner wear at 10 years and all six were revised for polyethylene wear. Polyethylene exchange was performed in four of the five patients who underwent revisions, all of whom were doing well at an average of 7.2 years (range, 4.7-9.1 years) after the revision procedure., Conclusions: At long-term followup, the overall revision rate remained low (6%). For patients surviving 15 years or more, the rate of revision was 12.8% and all revisions were secondary to aseptic sequelae of polyethylene wear. All revisions occurred more than 10 years after the initial procedures., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Early versions of uncemented femoral total hip stems were often associated with thigh pain thought to be due to micromotion between the implant and bone in the distal uncoated regions. An extensively coated stem was introduced in 1992 to reduce that risk. We therefore asked whether second-generation extensively porous-coated cementless femoral stems in patients younger than 50 years of age would (1) be durable in terms of revisions; (2) provide high functional scores and reduce thigh pain; and (3) show radiographic signs of durability, including a reduction in stress shielding. We prospectively followed all 100 patients (115 hips) age 50 and younger treated with primary cementless total hip arthroplasties using a second-generation extensively porous-coated femoral stem between June 1994 and December 1999. The average age was 39.6 years (range, 17-50 years). The stems were mated to cementless acetabular components. Ninety patients were followed for a minimum of 5 years (mean, 8.6 years; range, 5-10 years). One stem was revised after a periprosthetic fracture. None were revised for loosening and all stems demonstrated bony ingrowth at last followup. No acetabular shell was revised for loosening and none was radiographically loose. Six acetabular liners were revised for wear (three each were 22-mm and 26-mm heads). This second-generation extensively porous-coated stem was durable at 5- to 10-year followup in this young active population., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The relatively high prevalence of thigh pain and stress shielding associated with the AML porous-coated cementless femoral component led to the development of the Prodigy, a femoral component with more extensive porous-coating and a distal polished bullet tip with medial diaphyseal relief to potentially decrease the flexural rigidity. We prospectively evaluated a cohort of 100 consecutive cementless total hip arthroplasties performed using this device. The minimum followup was 10 years (mean, 11.4 years; range, 10-12 years). At 10-year followup, 69 of the 86 patients (82 hips) were living, 14 patients with 15 hips were deceased, and three patients with three hips were lost to followup. No hips required a stem revision. Two patients (two hips) complained of thigh pain. All hips were bone ingrown. Distal tip radiolucencies and osteolysis occurred in 13 hips (17%) and none, respectively. Twenty-one hips (28%) demonstrated moderate or severe stress shielding. Only further followup will determine if this could be a clinical problem or one with revision surgery. These results encourage the authors to continue using second-generation extensively coated stems in their primary total hip arthroplasty constructs.

Aseptic loosening attributable to wear-related osteolysis historically has been the predominant cause of failure in THA. Advances in low-wear bearing couples show great promise to substantially reduce this long-standing problem. However, there always has been striking variability in wear rate in any given cohort of patients who are similarly implanted, with some individuals typically experiencing near order-of-magnitude elevations above group mean. Third-body wear is likely a major contributor to many of these most osteolysis-prone outliers. For the patients affected, third-body effects may obviate many of the gains otherwise achieved by contemporary bearing surface improvements. Toward heightening visibility in terms of consequences for patients, this review paper summarizes an interrelated series of investigations quantifying construct level manifestations of third-body wear. Long-term followup of a unique group of patients with elevated third-body challenge shows statistically significant and clinically important wear-rate increases. A series of finite element models, validated physically, shows the linkage of location of third-body damage with variability of volumetric wear-rate acceleration and shows the effects of various implant factors, surgeon factors, and patient factors in the presence of third-body challenge. Finally, a mechanism for third-body debris access to wear-critical locations on the bearing surface is identified analytically and corroborated in laboratory experiments and implant retrievals.

Osteolysis is a multifactorial process dependent on surgical technique, implant design, patient factors, and material composition. Alternative bearing surfaces, such as highly cross-linked polyethylene, ceramic-on-ceramic, and metal-on-metal articular surfaces, have been introduced in an attempt to reduce wear and osteolysis following total hip arthroplasty. Intermediate-term follow-up data available suggest that the prevalence and severity of osteolysis may be reduced with these materials compared with conventional metal-on-polyethylene bearing surface couples. However, long-term data are presently unavailable; the future performance of these bearings awaits clinical validation.

Although debate regarding minimally invasive hip surgery is inconclusive, information published to date on the risks and benefits of small-incision approaches focuses the discussion on quality and outcomes. Small-incision surgical approaches include the posterior, anterolateral, direct anterior, and two-incision approach. Computer navigation assists in mapping hip replacement surgery. Obesity is a risk factor and has been found to increase complications. Patient education, pain management, and rehabilitation are important to recovery after minimal incision hip arthroplasty. Total hip replacement may be successfully achieved via smaller incisions, but functional improvement, discharge to home, patient satisfaction, and analgesic requirement may be similar regardless of the length of the incision.

Third-body effects are a major cause of the substantial variability of wear in total hip replacements. One potential mechanism by which third-body debris can access wear-critical central regions of closely conforming metal-on-polyethylene bearing couples is by fluid convection during incidents of subluxation accompanying neck-on-liner impingement. To provide evidence for this premise, we determined the association of severity of liner rim indentation damage (indicative of impingement frequency/vigor) and the presence of embedded third-body debris in 194 implants retrieved at revision. Rim damage was graded using the five-point Hospital for Special Surgery scale. Particle embedment was assessed both manually and by means of an image analysis computer program that detected the composition, size, and location of each particle. Sixty-eight percent of the cups showed rim indentation damage. We found an association between severity of rim damage and presence of embedded debris. There was substantial nonuniformity of the spatial distribution of the embedded debris, with the predominance of embedded debris at intermediate latitudes. These findings support the premise of convection of debris-laden joint fluid during lever-out subluxation as a mechanism for wear-consequential third-body particles to gain access to highly loaded regions of the bearing surface, thus potentiating increased wear.

We asked, "What are the quantitative variances in sagittal femoral bowing in patients who were indicated for total knee arthroplasty?" We retrospectively evaluated 145 consecutive patients who underwent 166 primary total knee arthroplasties with adequate preoperative nonrotated sagittal plane full-leg lateral radiographs. Digital radiographs were processed such that each femoral shaft was divided into three segments. A purpose-written program determined the flexion/extension of the femoral component using the Knee Society method of focusing on the distal femur and a second method using the whole femur. The median angle of curvature of the proximal, middle, and distal thirds of the femora were 5.4 degrees, 0.2 degree, and 3.1 degrees, respectively, with the largest bow occurring in the proximal segment followed by the distal segment and with the least bow in the middle segment. The median angles for femoral component flexion were considerably different with the whole femur angle showing more flexion (4 degrees) than that of the Knee Society angle (1.421 degrees). We found an inverse relationship between distal angle of curvature and height as well as weight. Men had greater proximal bowing and less distal bowing than women. The effects of these variances may have implications in development of osteoarthritis and total knee arthroplasty component survival.

The partnership between the orthopaedic profession and industry has existed for more than half a century and has created advanced orthopaedic care and conflicting interest in the delivery of that care. The orthopaedic surgeon first initiated and controlled the relationship with industry as surgeon innovators strove to improve orthopaedic implants. Over time, the practice of orthopaedic surgery and the business of orthopaedic product supply have changed substantially, as has the environment within which each functions. The surgeon's scope of care has expanded enormously over the past decades. Today, orthopaedic care is delivered through a highly interdependent relationship of the orthopaedic profession, the products industry, healthcare providers, healthcare financers, and government agencies. In many ways the relative influence of the orthopaedic surgeon has diminished in this relationship as the influence of other parties has grown. This work outlines some of the current risks and opportunities for the beneficial delivery of patient care the orthopaedic profession and industry mutually face.

The Prodigy femoral component was extensively coated along its entire length, except for a smooth bullet-shaped distal tip. At a minimum 5 year followup we compared the results of that stem to those of a proximally coated first generation femoral component at comparable followup to address the question of which design performed better. For the extensively coated cohort, 86 patients (100 hips) underwent total hip arthroplasty by a single surgeon. At final followup, no patients were lost to followup and no hips were revised for aseptic loosening. Clinically, 3% of patients reported thigh pain (versus 15% in the proximally coated group). Radiographically, all hips had evidence of bone ingrowth (versus 94% in the PCA group). As expected with an extensively coated device there were fewer radiolucencies around the lower half of the prosthesis as well as less distal femoral lysis compared to the proximally coated stem.

Minimally invasive surgery (MIS) and computer-assisted orthopaedic surgery (CAOS) options for total knee arthroplasty (TKA) have become increasingly popular. However, few controlled studies document their efficacy and safety. We examined the Internet for Knee Society members' websites to evaluate the level of promotion for these procedures in terms of direct (surgeon endorsed) and indirect (surgeon associated) information. On 92 websites, 22.7% made indirect reference to MIS TKA, while only 10.9% made a direct reference. Of the sites referencing MIS TKA, faster recovery was reported on 90% of indirect sites and 50% of direct sites. Specific risks were discussed on only 35% of indirect sites, and on only 20% of direct sites. CAOS TKA was discussed on 6.5% of indirect sites and on 5.4% of direct sites. Although MIS and CAOS TKA are frequently discussed on the Internet, only a small percentage of KS members directly promote these techniques (10.9% and 5.4%, respectively). Information was often indirectly associated with KS surgeons through institutional websites or hospital affiliations. Information indirectly associated with a surgeon may be mistaken as endorsing the procedure by a prospective patient.

Unlabelled: Although total knee arthroplasty is a very effective intervention and increasing in prevalence, failures do occur. We studied patients presenting for total knee arthroplasty revision to determine any modifiable causes of failure, both short and long term, and where future efforts should be directed to reduce the incidence of failure. A multicenter prospective observational cohort study of 318 consecutive patients, with minimum 1 year follow-up, undergoing total knee arthroplasty revision was performed. Associations between modes of failure were also assessed. The mean time from primary procedure to total knee arthroplasty revision was 7.9 years. Many patients (64.4%) had more than one cause of failure. Thirty-one percent of patients were early (< 2 years) failures at a mean of 11 months. These had a higher prevalence of infection, perioperative factors and comorbidities. Late failures occurred at a mean of 119.2 months. Other major causes of failure included instability (28.9%), wear (24.5%) and component loosening suggesting the importance of modifications in technique, implants and other areas. Application of these findings will ultimately reduce revision numbers through continued refinement of total knee arthroplasty practice and through further specific investigation of these modes of failure., Level of Evidence: Therapeutic study, level II-2 (prospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: We report the results of a minimum 21-year followup of a consecutive series of 103 patients who had 136 Marmor cemented unicompartmental knee replacements done between 1975 and 1982. Patients were evaluated clinically and radiographically. At minimum 21-year followup 14 patients (19 knees) were alive, 87 patients (115 knees) had died, and only two patients (two knees) were lost to followup. The average age at surgery was 70.9 years. The average followup Hospital for Special Surgery knee score was 58. The average Knee Society final followup clinical and functional scores averaged 72 and 53 points, respectively. Nineteen knees (14%) were revised during the 21-year followup period: nine for progression of disease, eight for loosening, and two for pain, at an average of 10.6 years (range, 1-22 years). Of the 19 knees in the 14 patients who were still alive at final followup, seven (37%) were revised: two for tibial loosening, four for disease progression, and one for pain. Unicompartmental knee replacements in this relatively older age group of patients performed well at minimum 21-year followup. Although we are encouraged by these results, only 22% were done in patients who were younger than 65 years at the time of surgery and the results in this group were significantly less durable., Level of Evidence: Therapeutic study, Level IV-1 (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Polyethylene wear acceleration from (scratching) damage to the femoral head is a recognized hazard from constructs prone to generate third-body debris, but the phenomenon is nebulous and therefore often is subordinated to more direct and immediate considerations. To help delineate tangible quantitative relationships between counterface roughening and accelerated polyethylene wear, an experimentally validated sliding-distance-coupled finite element model of total hip replacement wear was adapted to incorporate regions of localized femoral head roughening. This computational formulation was used systematically to identify the sites on the femoral head for which a given severity of local roughening (parameterized in terms of roughening patch size and tribologic wear coefficient) was most consequential in terms of elevated polyethylene wear. Two such sites, of nominally comparable kinetic importance, were consistently evident throughout a wide range of roughening severities. These critical sites were located quasi-superiorly near the sagittal midline of the head, one slightly anterior and one slightly posterior of the coronal midline.

Constrained acetabular components have been used to treat certain cases of intraoperative instability and postoperative dislocation after total hip arthroplasty. We report our experience with a tripolar constrained component used in these situations since 1988. The outcomes of the cases where this component was used were analyzed for component failure, component loosening, and osteolysis. At average 10-year followup, for cases treated for intraoperative instability (2 cases) or postoperative dislocation (4 cases), the component failure rate was 6% (6 of 101 hips in 5 patients). For cases where the constrained liner was cemented into a fixed cementless acetabular shell, the failure rate was 7% (2 of 31 hips in 2 patients) at 3.9-year average followup. Use of a constrained liner was not associated with an increased osteolysis or aseptic loosening rate. This tripolar constrained acetabular liner provided total hip arthroplasty construct stability in most cases in which it was used for intraoperative instability or postoperative dislocation.

The purpose of this study was to report the functional results and mortality rates of a consecutive series of patients younger than 50 years after Charnley total hip arthroplasty. The original group of 69 patients (93 hips) was followed up until death or a minimum of 25 years after surgery. Of the original 93 hips, 29 had been revised at some point. Functional outcomes included the Short Form-36, Western Ontario and McMaster University University Osteoarthritis Index (WOMAC), 6-minute walk distance, Noyes activity scale, and Harris hip scores and included followup in 42 of 43 living patients. The functional outcome of patients was good, with comparable Short Form-36 scores compared with normative values of healthy age-matched subjects. The 6-minute walk distances and WOMAC scores were slightly lower than healthy normatives but were thought to be influenced by medical comorbidities. Although comorbid medical and musculoskeletal conditions significantly hindered most measures of function, revision surgery or radiographic loosening of components had no significant influence on function. The mortality rates of this cohort of patients were similar to normative values at both 10 and 25 years after surgery.

The current study systematically reviews the literature describing patient outcomes after revision total hip arthroplasties using conventional global hip score ratings. Two thousand one hundred thirty-seven English-language articles published from 1966 through 2000 were identified through a computerized literature search and bibliography review. A three-step filter process was used to identify articles to be included in the metaanalysis. Forty-two articles with 2578 patients had data abstracted for the analysis. Metaanalysis of global hip scores was done using a fixed effects model with the assumption that the variances of each measurement were identical across studies. Thirty-nine articles reporting on 46 cohorts progressed through three filters and went to data extraction and analysis. Revision total hip arthroplasty is a reasonably safe and effective procedure for failed hip replacement Based on this exploratory analysis revision hip procedures seem to have comparable longevity, to primary hip replacement but appear to have slightly lower functional outcome (as measured by global hip scores), and slightly higher morbidity and mortality rates than primary procedures. Inconsistent reporting in the original studies limited exploration of other factors that may have affected outcomes.

Functional load transmission and kinematic performance were compared for standard versus posterior-stabilized versions of a rotating-platform total knee implant, over a standardized loading cycle, using three-dimensional contact finite element analysis. These two design variants differ primarily in terms of the latter's polyethylene insert having a cam that engages with the femoral component during appreciable flexion, thereby inducing femoral component rollback. The finite element model, previously validated experimentally, afforded direct comparisons of anterior lift-off of the insert from the tibial tray, of bearing mobility (insert rotation about the pivot post), of femoral rollback, and of metal-on-polyethylene contact stresses at the bearing and backside surfaces of the insert. Both design variants generally performed comparably, exhibiting an internal and external rotation range of approximately 5 degrees, approximately 1.5 mm peak lift-off at the anterior aspect of the insert, and approximately 15 mm of posterior rollback, the respective maxima for both designs occurring at approximately the same instants in the gait cycle. However, the posterior-stabilized design had slightly more rollback, and slightly less anterior lift-off and rotation, than did the standard rotating-platform design. Peak polyethylene stresses occurred on the backside of the insert near the posterior edge of the medial compartment, the magnitude being approximately 18% higher for the posterior-stabilized design (21 MPa) than for the standard design.

Observation cohort studies, a sliding-distance-coupled finite element model, and an expanded finite element model that simulates dislocation were used to evaluate the benefits and compromises associated with the use of smaller femoral heads in the total hip arthroplasty construct. Wear studies of total hip arthroplasty cohorts showed less polyethylene wear and less deleterious effects of third body debris when smaller femoral head sizes were used. The sliding-distance-coupled finite element model findings were corroborated by these clinical wear studies. The dislocation model predicted the increased propensity for dislocation when smaller modular head femoral components were used in the cohort studies. Impingement is not the only contributor to frank dislocation. The dislocation model explicitly defined the range of motion changes from impingement to dislocation, and the resisting moment changes between construct designs.

Reports of posterior-stabilized total knee replacements have shown excellent clinical success. However, tibial post-femoral cam impingement has been seen in modular component retrievals. This finding has been associated with transmission of rotational forces to the modular tray-polyethylene interface with subsequent backside polyethylene wear and the development of osteolysis. Femoral cam-tibial post designs that allow hyperextension and limit rotational constraint may minimize this impingement. Technical considerations including the avoidance of femoral component flexion and posterior tibial slope will minimize anterior tibial post impingement.