Bearings In Total Hip Arthroplasty Research Articles

Squeaking in Large Diameter Ceramic-on-Ceramic Bearings in Total Hip Arthroplasty

We analyzed the results of 206 consecutive total hip arthroplasties performed using large diameter ceramic-on-ceramic bearings. At an average follow-up of 28months, the mean Harris Hip Score improved from 54 to 92. Fifteen (7.3%) hips were noted to squeak. There was no significant difference between silent and squeaking hips with regards to age, weight, height, BMI, range of movement, femoral head diameter, leg length, and offset or center of rotation. No correlation was present between incidence of squeaking and increasing cup inclination and anteversion. 5.2% of cups orientated within Lewinnek's safe zone squeaked. No hips required revision for squeaking. While large diameter ceramic bearings may produce squeaking, our early results of surgery using large head ceramic bearings are encouraging. However, long-term follow-up is required.

The 2014 Frank Stinchfield Award: The 'landing zone' for wear and stability in total hip arthroplasty is smaller than we thought: a computational analysis.

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. 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. 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. 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. 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. 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.

How have alternative bearings and modularity affected revision rates in total hip arthroplasty?

Total hip arthroplasty (THA) continues to be one of the most successful surgical procedures in the medical field. However, over the last two decades, the use of modularity and alternative bearings in THA has become routine. Given the known problems associated with hard-on-hard bearing couples, including taper failures with more modular stem designs, local and systemic effects from metal-on-metal bearings, and fractures with ceramic-on-ceramic bearings, it is not known whether in aggregate the survivorship of these implants is better or worse than the metal-on-polyethylene bearings that they sought to replace. Have alternative bearings (metal-on-metal and ceramic-on-ceramic) and implant modularity decreased revision rates of primary THAs? In this systematic review of MEDLINE and EMBASE, we used several Boolean search strings for each topic and surveyed national registry data from English-speaking countries. Clinical research (Level IV or higher) with ≥5years of followup was included; retrieval studies and case reports were excluded. We included registry data at ≥7years followup. A total of 32 studies (and five registry reports) on metal-on-metal, 19 studies (and five registry reports) on ceramic-on-ceramic, and 20 studies (and one registry report) on modular stem designs met inclusion criteria and were evaluated in detail. Insufficient data were available on metal-on-ceramic and ceramic-on-metal implants, and monoblock acetabular designs were evaluated in another recent systematic review so these were not evaluated here. There was no evidence in the literature that alternative bearings (either metal-on-metal or ceramic-on-ceramic) in THA have decreased revision rates. Registry data, however, showed that large head metal-on-metal implants have lower 7- to 10-year survivorship than do standard bearings. In THA, modular exchangeable femoral neck implants had a lower 10-year survival rate in both literature reviews and in registry data compared with combined registry primary THA implant survivorship. Despite improvements in implant technology, there is no evidence that alternative bearings or modularity have resulted in decreased THA revision rates after 5years. In fact, both large head metal-on-metal THA and added modularity may well lower survivorship and should only be used in select cases in which the mission cannot be achieved without it. Based on this experience, followup and/or postmarket surveillance studies should have a duration of at least 5years before introducing new alternative bearings or modularity on a widespread scale.

Mid-term result of ceramic bearings in total hip arthroplasty.

The purpose of this study was to evaluate our clinical experience with ceramic-on-ceramic cementless total hip arthroplasty (THA) and complications after an average follow-up of more than eight years. From January 2001 to December 2008, 540 THA with ceramic-on-ceramic bearings were performed in 448 patients (92 bilateral, 54 of which were operated simultaneously) with a mean age 49.9 years (range 18-84) by a senior surgeon. Pre-operative aetiological reasons were developmental dysplasia of the hip (DDH) in 205 hips, degenerative arthritis in 157 hips, avascular necrosis in 51 hips, rheumatoid diseases in 40 hips, posttraumatic arthritis in 40 hips, other reasons in 25 hips and revision surgery in 22 hips. Patients were evaluated with Harris hip score (HSS), and radiological findings of acetabular and femoral component loosening or osteolysis with ceramic bearing related complications like squeaking, liner and head fractures were recorded. The average duration of follow-up time was 8.2 years (range, five to 13.2). The main Harris hip score increased from 42.4 points preoperatively to 94.9 points at the time of last follow-up. We had one fracture of the ceramic head, 11 clicking and four squeaking; one of them was revised because of terrible squeaking due to acetabular liner fracture, the other three were seldom audible from the outside and followed conservatively. We did not observed loosening or osteolysis due to ceramic bearings at the time of the final follow-up. Our study has demonstrated that ceramic-on-ceramic bearings can be used safely in different etiological problems. Incidences of noisy hips are becoming less frequent.

Trends in Total Hip Arthroplasty Implant Utilization in the United States

Total hip arthroplasty (THA) implant usage has evolved as experience has been gained with newer implant designs. The purpose of this study was to characterize trends in THA implant usage between 2001 and 2012. The Orthopedic Research Network, which includes 174 hospitals and ~105,000 THA, was used to evaluate trends in fixation, bearings, acetabular cup and liner, and femoral head usage. In 2012, 93% of THAs were cementless; 56% of THA bearings were metal-HXLPE; and 35% were ceramic-HXLPE. 99% of acetabular cups were modular. 61% of femoral heads were metal, 39% were ceramic, 51% were 36mm, and 28% were 32mm. THA implant usage trends favor cementless fixation, metal-on-polyethylene or ceramic-on-polyethylene bearings, modular acetabular cups, and large diameter femoral heads.

Risk of Impingement and Third-body Abrasion With 28-mm Metal-on-metal Bearings

Concerns have been raised about the sequelae of metal-on-metal (MoM) bearings in total hip arthroplasty (THA). However, retrieval studies, which offer the best insight into the clinically relevant mechanisms of MoM wear, have followed predictable trends to date such as indicting cobalt-chromium (CoCr) metallurgy, cup design, high conformity between the head and cup, "steep cups," "microseparation," and "edge wear." We wished to evaluate a set of retrieved 28-mm MoM THA for signs of (1) cup-to-stem impingement; (2) normal wear pattern and concomitant stripe damage on femoral heads that would signify adverse wear mechanics; and (3) well-defined evidence of third-body scratches on bearings that would indicate large abrasive particles had circulated the joint space. Ten 28-mm MOM retrievals were selected on the basis that femoral stems were included. Revision surgeries at 3 to 8 years were for pain, osteolysis, and cup loosening. CoCr stems and the MoM bearings were produced by one vendor and Ti6Al4V stems by a second vendor. All but two cases had been fixed with bone cement. We looked for patterns of normal wear and impingement signs on femoral necks and cup rims. We looked for adverse wear defined as stripe damage that was visually apparent on each bearing. Wear patterns were examined microscopically to determine the nature of abrasions and signs of metal transfer. Graphical models recreated femoral neck and cup designs to precisely correlate impingement sites on femoral necks to cup positions and head stripe patterns. The evidence revealed that all CoCr cup liners had impinged on either anterior or posterior facets of femoral necks. Liner impingement at the most proximal neck notch occurred with the head well located and impingement at the distal notch occurred with the head rotated 5 mm out of the cup. The hip gained 20° motion by such a subluxation maneuver with this THA design. All heads had stripe wear, the basal and polar stripes coinciding with cup impingement sites. Analysis of stripe damage revealed 40 to 100-μm wide scratches created by large particles ploughing across bearing surfaces. The association of stripe wear with evidence of neck notching implicated impingement as the root cause, the outcome being the aggressive third-body wear. We found consistent evidence of impingement, abnormal stripe damage, and evidence of third-body abrasive wear in a small sample of one type of 28-mm MoM design. Impingement models demonstrated that 28-mm heads could lever 20° out of the liners. Although other studies continue to show good success with 28-mm MoM bearings, their use has been discontinued at La Pitie Hospital.

Ceramic-on-polyethylene: The experience of the Ranawat Orthopaedic Center

Traditionally, metal-on-polyethylene has been the gold standard bearing in total hip arthroplasty. Ceramics were introduced as an alternative bearing because of their superior mechanical properties. Our institution has found that ceramic-on-polyethylene has consistently shown lower in vivo wear rates compared to metal-on-polyethylene. The latest generation of ceramic-on-polyethylene, BIOLOX delta-on-highly cross-linked polyethylene, has shown an excellent linear wear rate (0.006mm/yr), which is much lower than previously found wear rates for cobalt–chrome-on-highly cross-linked polyethylene (0.011mm/yr). The minimal wear rate of BIOLOX delta-on-highly cross-linked polyethylene provides the potential to increase long-term survivorship and become the new gold standard bearing in THA.

The reliability of modern alumina bearings in total hip arthroplasty—Update to a 2006 report

Ceramic components׳ clinical fractures in total hip arthroplasty (THA) are a rare but, nonetheless, serious complication. As a result of continued improvements in ceramic material quality, manufacturing methods, and implant design made over the last 30 years, the incidence of such failures has been drastically reduced. In this report, the frequency of these ceramic components׳ clinical failures in THA will be examined. In addition, some information regarding the contribution that can be made by the surgeon to enhance the reliability of ceramic components will also be presented. In order to get a broad view, the largest supplier of these components, CeramTec Medical Products (Plochingen, Germany), was contacted, and they agreed to share their most recent data. In the year 2000, the largest supplier of alumina–ceramic bearings for orthopedic applications (CeramTec GmbH, Plochingen, Germany) began a rigorous program of collecting clinical fracture data for all of its ceramic components. The clinical fracture data for the period of January 2000–June 2013 are reported here, with a review of the material properties, historical component fracture trends, and relative risk of fracture associated with alumina THA bearings. The data reported is divided into two separate groups. The first one is the incidence of clinical fracture of the Biolox®forte material. This is their original material developed in the 1970s and is still available today and optimized over the years. The overall clinical fracture rate of these alumina components was 0.021%, or 21 in 100,000, during the January 2000–June 2013 time period. The second group is composed of components manufactured from their Alumina Matrix Composite, Biolox®delta. The overall clinical fracture rate for these components is 0.0001% or 1 in 100,000. Almost 80% of these alumina bearing failures occurred within 36 months following surgery. Using the latest material and increasing femoral head diameter were associated with a substantially reduced risk of fracture. Alumina bearings used in modern THA implants are safe and reliable, with a very low risk of failure. Improvements in the materials, developments in the manufacturing, the introduction of the Alumina Matrix Composite, and the trend to utilize larger-diameter ball heads are likely to continue to reduce the concerns that have been in the mind of surgeons using ceramics in THA.

A prospective study of a ceramic-on-metal bearing in total hip arthroplasty

We prospectively assessed the efficacy of a ceramic-on-metal (CoM) hip bearing with uncemented acetabular and femoral components in which cobalt-chrome acetabular liners and alumina ceramic heads were used. The cohort comprised 94 total hip replacements (THRs) in 83 patients (38 women and 45 men) with a mean age of 58 years (42 to 70). Minimum follow-up was two years. All patients had pre- and post-operative assessment using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), Oxford hip score and Short-Form 12 scores. All showed a statistically significant improvement from three months post-operatively onwards (all p < 0.001). After two years whole blood metal ion levels were measured and chromosomal analysis was performed. The levels of all metal ions were elevated except vanadium. Levels of chromium, cobalt, molybdenum and titanium were significantly higher in patients who underwent bilateral THR compared with those undergoing unilateral THR (p < 0.001). Chromosomal analysis demonstrated both structural and aneuploidy mutations. There were significantly more breaks and losses than in the normal population (p < 0.001). There was no significant difference in chromosomal aberration between those undergoing unilateral and bilateral procedures (all analyses p ≥ 0.62). The use of a CoM THR is effective clinically in the short-term, with no concerns, but the significance of high metal ion levels and chromosomal aberrations in the long-term remains unclear.

Squeaking total hip arthroplasty bearings.

Squeaking total hip arthroplasty bearings.

Metal Sensitivity After TKA Presenting With Systemic Dermatitis and Hair Loss

Recent problems with metal-on-metal bearings in total hip arthroplasty have highlighted a connection between metal particles and allergic responses. Metal sensitivity associated with total knee arthroplasty (TKA) is less understood and poorly characterized. However, metal sensitivity can lead to TKA failure. Accurate and reliable testing for this phenomenon is elusive; therefore, the diagnosis of metal sensitivity remains one of exclusion. Only skin testing and lymphocyte transformation testing are commonly available to assess hypersensitivity, and neither test is reliable.This article describes a woman who presented with severe whole-body dermatitis and hair loss. After prolonged pain and progressive stiffness, including failed manipulation while under anesthesia and open synovectomy, the patient had a positive skin test, but the lymphocyte transformation test was negative. She was treated for metal sensitivity with TKA revision to nonallergenic components, and all symptoms resolved. One year after revision, she had good range of motion, complete dermatitis resolution, and hair loss restoration.To the authors' knowledge, this is the only report that describes hair loss as a symptom of metal sensitivity secondary to TKA and hair regrowth after revision. The authors now include metal sensitivity in a differential of causes of pain and other unusual symptoms after TKA that are otherwise unexplained.

High Survivorship With a Titanium-encased Alumina Ceramic Bearing for Total Hip Arthroplasty

Although ceramic-on-ceramic bearings for total hip arthroplasty (THA) show promising results in terms of bearing-surface wear, fracture of the bearing, insertional chips, and squeaking remain a concern. Our primary objective of this report was to determine overall survivorship of a titanium-encased ceramic-on-ceramic bearing couple. Our secondary objectives were to evaluate for ceramic fracture, insertional chips, osteolysis, and device squeaking. Six surgeons at six institutions implanted 194 patients (209 hips) with an average age of 52 years with cementless hips and alumina ceramic bearings. One hundred thirty-seven patients (146 hips) have 10-year followup (70%). We determined Kaplan-Meier survivorship of the bearing surface and implant system and collected radiographic and clinical data to evaluate for osteolysis and squeaking. Survivorship using revision for any reason as the end point was 97% at 10 years and survivorship end point bearing surface failure or aseptic loosening of 99%. There was one ceramic insert fracture (0.5%), there were no insertional chips, there was no visible osteolysis on AP and lateral radiographs, and there was a 1% patient-self-reported incidence of squeaking at the last clinical followup. Six hips underwent revision (3.7%). Ceramic bearings for THA with a titanium-encased insert have high survivorship at 10 years followup and a fracture risk of 0.5%. We found at last followup on routine radiographs no evidence of osteolysis, and no patient has been revised for squeaking or has reported dissatisfaction with the clinical result because of noise. IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Poor Short Term Outcome with a Metal-On-Metal Total Hip Arthroplasty

Metal-on-metal (MoM) bearings for total hip arthroplasty (THA) have come under scrutiny with reports of high failure rates. Clinical outcome studies with several commercially available MoM THA bearings remain unreported. We evaluated 78 consecutive MoM THAs from a single manufacturer in 68 patients. Sixty-six received cobalt–chrome (CoCr) monoblock and 12 received modular titanium acetabular cups with internal CoCr liners. Femoral components were titanium with modular necks. At average 2.1years postoperatively, 12 THAs (15.4%) demonstrated aseptic failure (10 revisions, 2 revision recommended). All revised hips demonstrated capsular necrosis with positive histology reaction for aseptic lymphocytic vasculitis-associated lesions/adverse local tissue reactions. Prosthetic instability following revision surgery was relatively common. Female gender was a strong risk factor for failure, though smaller cups were not. Both monoblock and modular components fared poorly. Corrosion was frequently observed around the proximal and distal end of the modular femoral necks.

A late dissociation of the ceramic component of a sandwich liner cup in a total hip arthroplasty&amp;lt;br&amp;gt;—Case report and review of the literature

We present a case of a 71-year-old woman with unexplained instability of her total hip arthroplasty 12 years after implantation due to loosening of the ceramic component of a sandwich ceramic in polyethylene liner. She experienced in total 2 dislocations in 6 months. These events occurred without fracture of the ceramic liner. Sandwich ceramic liners were introduced with the idea of combining the benefits of ceramic and polyethylene bearings in total hip arthroplasty in order to reduce wear and to allow a ceramic on ceramic bearing to be used in a cup designed for polyethylene inserts only. Although some reports showed promising early results, case reports and later on retrospective analysis showed high fracture rates of the ceramic liner component. We believe that loosening of the ceramic component may precede fracture of the liner and that a ceramic on ceramic configuration is preferable.

Large Diameter Metal on Metal Articulations. Comparison of Total Hip Arthroplasty and Hip Resurfacing Arthroplasty

The use of large diameter metal bearing total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) increased in popularity in the last decade. More recent literature has highlighted the effect of head size in patient outcomes. Data was obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOA-NJRR) to evaluate the Birmingham (MoM) bearing surface when used with THA and HRA. There is no difference in the overall rate of revision between the THA and HRA but head size has a significant effect on revision rate. The data show that small diameter metal bearings in HRA (below 50mm) have a higher rate of revision than large diameter metal bearings in HRA (equal to and above 50mm) (P<.001). Conversely the large diameter metal bearings in THA have a higher rate of revision than the small diameter metal bearings in THA (P=.027). The revision rate for large diameter HRA compared to small diameter THA is not significantly different P=.670. We recommend caution when choosing either a large diameter (≥50mm) metal on metal THA or small diameter (<50mm) HRA.

Large-diameter Delta Ceramic-on-ceramic Versus Common-sized Ceramic-on-polyethylene Bearings in THA

The higher failure rate of total hip arthroplasty (THA) in young, active patients remains a challenge for surgeons. Recently, larger-diameter femoral heads combined with an alumina matrix composite ceramic (BIOLOX Delta; CeramTec AG, Plochingen, Germany) articulation was developed to improve implant longevity and meet patients' activity demands while reducing the risk of component-related complications. The purpose of this study was to determine whether this new device may provide advantages for young, active patients. A prospective, randomized, controlled trial was conducted on 93 patients (113 THAs) with more than 3 years of follow-up. Patients were randomly divided into a study group (51 THAs) with a 36-mm Delta ceramic-on-ceramic (COC) articulation and a control group (62 THAs) with a common-sized alumina ceramic head on polyethylene liner (COP) articulation. Clinical and radiographic results were collected to compare the outcomes and complications, including implant-related failures, osteolysis, and noises. The large-diameter Delta COC articulation provided greater range of motion improvement (6.1° more), similar Harris Hip Scores, and similar complication rates compared with the alumina COP articulation. This study suggests that in the short term, the large-diameter Delta COC articulation results in better range of motion with no higher complication rates; however, mid-term (8-10 years) or longer follow-up is necessary to determine its superiority in young, active patients.

In Vivo Dissociation Of A Dual Articulation Bearing In Revision THA - Case Report

Revision total hip arthroplasty (THA) can be a difficult reconstructive procedure that challenges the skills of even the adroit orthopaedic surgeon. Revision THA for aseptic failure after acetabular/pelvic fracture is one of the more difficult challenges in the realm of hip reconstruction. The high complication rate associated with this complex reconstruction remains the dominant obstacle for obtaining consistent satisfactory outcomes. The specific problems of boney defects, pelvic malalignment, heterotopic ossification, soft tissue scarring, and muscle atrophy compromise the goals of revision THA, which include osteointegration of implant to host bone, restoration of hip joint biomechanics, and joint stability12. Recurrent dislocation in revision THA is one of the more frustrating complications for both the patient and the surgeon, and it remains so even today. Despite this, there continues to be developments in surgical technique and prosthetic design to enhance prosthetic hip stability. One prosthetic design, the dual articulation hip bearing, was developed to enhance THA stability. The dual articulation concept was developed by professor Gilles Bousquet and engineer André Rambert in the late 1970’s14. The dual mobility design incorporates two articular surfaces within the THA bearing. The acetabular cup is composed of a metallic bearing that articulates with an ultra high molecular weight polyethylene (UHMWPE) ball. Within the UHMWPE head is an inner ball that is enclosed within the polyethylene (figure 1). This design concept increases hip primary arc range before impingement.The Bousquet dual mobility concept has been used over the last 20 years in Europe with successful clinical outcomes6,7,9,11. In the United States, the dual articulation bearing design received FDA clearance in 2011. However, as with the addition of any modular part, there is the potential for new in-vivo failure mechanisms. With the dual mobility construct, the new failure mechanism is dissociation of the inner head1,10. We report in this case an early traumatic dissociation of a dual mobility bearing utilized in a complex revision THA. To our knowledge, this is the first reported case of a traumatic in-vivo disassembly of a dual articulation bearing THA.Key Words: Dual Articulation, Dual Mobility, Active Articulation, THA, Revision, Dissociation, Dislocation

Long-term follow-up and metal ion trend of patients with metal-on-metal total hip arthroplasty

Long-term studies are required to support the use of metal-on-metal (MoM) bearings in total hip arthroplasty (THA) given the concern about systemic metal ion release and reports of adverse local soft tissue reactions. The purpose of this study was to report the seven to 13-year clinical, radiographic, and metal ion results in patients following MoM THA. We studied 163 prostheses after second-generation MoM THA between July 1997 and November 2003. Cobalt and chromium metal ions were collected using whole and analysed by inductively-coupled plasma-mass spectrometry. The mean follow-up was 8.87 years (range, 7-13 years). Four hips (2.5 %) were revised. The Kaplan-Meier survivorship was 91.3 % for revision for all causes, and 97.5 % when excluding the hips revised for a manufacturer's defect. Median whole blood cobalt levels peaked at a value of 2.87 μg/L at four years (p < 0.0001 vs. pre-operative) and subsequently decreased to 2.0 μg/L after nine years (p = 0.002 vs. four years). Median chromium levels maximally increased up to 0.75 μg/L after five years (p < 0.0001 vs. pre-operative) and tended to decrease thereafter to values of 0.56 μg/L after seven years. This seven to 13-year follow-up study indicates that the clinical and radiological results following MoM THA are satisfactory with low revision rates. Cobalt and chromium ion levels peaked at four and five years, respectively, and gradually decreased thereafter.

Ceramic-on-Ceramic THA の破損の2例

Ceramic-on-Ceramic THA の破損の2例

The Utility of MARS MRI in Patients with Metal-on-Metal Bearings

Metal-on-metal bearings for total hip arthroplasty have a long history of use that dates back to the introduction of the McKee-Farrar prosthesis in the 1960s. Metal-on-metal bearings ultimately fell out of favor because of the excellent clinical results of the Charnley low-friction arthroplasty concept, which employed metal-on-UHMWPE (ultra-high molecular weight polyethylene) bearing surfaces. However, the use of metal-on-metal bearings was revisited in the 1990s as polyethylene-associated periprosthetic osteolysis emerged as a major clinical problem limiting the longevity of hip reconstructions in high-demand patient populations. Within the last decade, numerous metal-on-metal designs for both total hip arthroplasty and hip resurfacing arthroplasty have been introduced into the marketplace. However, over the last several years it has become evident that contemporary metal-on-metal bearings are not immune to some of the problems, including periprosthetic osteolysis, that have plagued other bearing surface combinations. In addition, investigators described a distinct histological pattern, termed “aseptic lymphocyte-dominated vasculitis-associated lesion” (ALVAL), that was associated with symptomatic metal-on-metal bearings. More recently, investigators described local soft-tissue reactions termed “pseudotumors” in association with symptomatic metal-on-metal devices. Initially, studies of adverse local tissue reactions (including osteolysis, ALVAL, and pseudotumors) in retrospective studies of metal-on-metal implants did not indicate the prevalence. However, case-control studies and registries began to document that certain metal-on-metal bearing designs were associated with an unacceptably high failure rate, leading to high-profile device recalls that captured the attention of the worldwide media. In some cases, the adverse local tissue response …