Bearings In Total Hip Arthroplasty Research Articles

Long-term results of the M2A-38-mm metal-on-metal articulation

BackgroundLarge-diameter head metal-on-metal (MoM) bearings in total hip arthroplasty (THA) are associated with increased whole blood levels of chromium (Cr) and cobalt (Co), adverse reactions to metal debris (ARMD) and poor survival rates. The prevalence of high metals concentrations, ARMD and the risk of revision surgery may vary significantly among different prostheses and long-term studies are few. This single-center study reports the long-term results of the 38-mm MoM bearing system.Materials and methodsBetween 2003 and 2009, 80 patients received primary cementless THA using the large head metal-on-metal articulating surface M2A-38 cup (Biomet, Inc., Warsaw, IN, USA) at a single institution. Forty-five patients (53 hips) were retrospectively reviewed for a mean follow-up of 127 months.ResultsTwo cups were revised. The cumulative implant survival rate was 98% at 10 years and 74% at 13 years. In the whole sample, the median Co and Cr concentrations were 4.8 µg/L (IQR 1.2–4.9 µg/L) and 2.5 µg/L (IQR 0.6–3.0 µg/L), respectively. The incidence of Co or Cr levels > 7 μg/L was 15.5% and the incidence of ARMD was 3.8%. Co and Cr levels showed no correlation with cup inclination, Harris Hip Score, or total Hip Disability and Osteoarthritis Outcome score.ConclusionsOur results confirm that the problems of release of metal ions with the possible increase of metal circulating levels and of adverse reactions may also occur in the long term with this brand of MoM large head, and that a structured follow-up program is mandatory.Levels of evidenceLevel 4.

The Current Role of Dual Mobility Articulations in Total Hip Arthroplasty

AbstractThe concept of dual mobility (DM) bearings in total hip arthroplasty was first introduced by Professors Gilles Bousquet and Andre Rambert in France in 1974 with the goal of enhancing hip stability. Although DM did not receive U.S. Food and Drug Administration approval for commercial use in the United States until 2009, there has been a surge in popularity of DM implants over the past several years, evidenced by the American Joint Replacement Registry data. The enthusiasm for DM stems from a growing body of literature that supports its use across a range of patient populations, most notably revision hip arthroplasty and high-risk primary scenarios. DM has been shown to effectively reduce the risk of dislocation while also exhibiting excellent survivorship. DM does incur some unique risks, namely, intraprosthetic dissociation, but many of the early concerns with DM have not been realized in the literature and do not seem to negatively impact its long-term survivorship. The exact indications for DM have yet to be defined and remain a matter of debate. It should be considered as an alternative for any primary or revision hip arthroplasty at high risk for postoperative instability. In this article, the authors review the current literature regarding the clinical success of DM implants for a variety of indications, all of which predispose to hip instability. The history, basic biomechanics, modern designs, and unique complications are also discussed.

Excellent results of large-diameter ceramic-on-ceramic bearings in total hip arthroplasty: Is Squeaking Related to Head Size.

This study reports the mid-term results of total hip arthroplasty (THA) performed using a monoblock acetabular component with a large-diameter head (LDH) ceramic-on-ceramic (CoC) bearing. Of the 276 hips (246 patients) included in this study, 264 (96%) were reviewed at a mean of 67 months (48 to 79) postoperatively. Procedures were performed with a mini posterior approach. Clinical and radiological outcomes were recorded at regular intervals. A noise assessment questionnaire was completed at last follow-up. There were four re-operations (1%) including one early revision for insufficient primary fixation (0.4%). No hip dislocation was reported. The mean University of California, Los Angeles (UCLA) activity score, 12-Item Short-Form Health Survey (SF-12) Mental Component Summary (MCS) score, SF-12 Physical Component Summary (PCS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and Forgotten Joint Score (FJS) were 6.6 (2 to 10), 52.8 (25.5 to 65.7), 53.0 (27.2 to 66.5), 7.7 (0 to 63), and 88.5 (23 to 100), respectively. No signs of loosening or osteolysis were observed on radiological review. The incidence of squeaking was 23% (n = 51/225). Squeaking was significantly associated with larger head diameter (p < 0.001), younger age (p < 0.001), higher SF-12 PCS (p < 0.001), and UCLA scores (p < 0.001). Squeaking did not affect patient satisfaction, with 100% of the squeaking hips satisfied with the surgery. LDH CoC THAs have demonstrated excellent functional outcomes at medium-term follow-up, with very low revision rate and no dislocations. The high incidence of squeaking did not affect patient satisfaction or function. LDH CoC with a monoblock acetabular component has the potential to provide long term implant survivorship with unrestricted activity, while avoiding implant impingement, liner fracture at insertion, and hip instability. Cite this article: Bone Joint J 2018;100-B:1434-41.

Ceramic bearings for total hip arthroplasty are associated with a reduced risk of revision for infection.

Periprosthetic joint infection (PJI) is a serious complication after total hip arthroplasty (THA) and bearing material's associations to PJI prevalence is largely unknown. The main purposes of this study were to determine if revision for infection varied depending on the type of bearing surface used in primary THA and to study whether patient or implant related factors had an effect on this variation. A total of 177,237 primary THA procedures from the Australian Registry (AOANJRR) were analysed. 3 bearing surfaces were compared. Metal-on-highly cross-linked polyethylene (MoXP) bearing had been used in 95,129 hips, ceramic-on-highly cross-linked polyethylene (CoXP) in 24,269 hips, and ceramic-on-ceramic (CoC) in 57,839 hips. Revision rates for infection were compared between the 3 groups. Both MoXP and CoXP had a higher revision rate for infection compared to CoC hips (hazard ratio [HR] 1.46 (1.25, 1.72), p < 0.001) and HR 1.42 (1.15, 1.75), p = 0.001 respectively). Patients aged 70 years or less had a lower revision rate for infection when a CoC bearing was used. This difference was independent of sex, and prostheses selection. No difference was evident if the femoral component was cemented or a head size of 28 mm was used. In this registry-based material, use of a CoC bearing was associated with a lower risk of revision for infection in patients younger than 70 years when cementless femoral components were used. Further studies are needed to verify this finding.

Ceramic-on-Ceramic in Total Hip Replacement Revision.

The use of Ceramic-on-Ceramic (CoC) bearings in primary total hip arthroplasty (THA) is increasing and has been intensively analysed. This bearing plays a particularly relevant role in young, active patients and shows advantages over other bearings in biocompatibility, wear rate and lubrication properties. On the contrary, CoC bearings in revision THA are seldom used and scarcely analysed. The aim of this study is to systematically review the available literature on CoC bearings in revision THA. A systematic research in the English literature was performed to identify all studies reporting results of THA revisions using ceramic-on-ceramic bearing. The initial search strategy revealed 555 articles for consideration. On the basis of eligibility criteria, 26 studies were included in this review. Twenty-six studies, accounting for 1846 procedures, were eligible and included in the review. No studies of Level I were identified. Eighteen studies reported on revisions of CoC implants for various reasons, performed either with CoC or different bearings. In 111 patients a CoC bearing was used for the revision. Six studies consistently reported outcome measures for CoC bearing THA revisions, so that a quantitative synthesis of the data was possible. The range of follow-up across the six studies varied between 2.1 and 19 years, with a cumulative avearage follow-up of 9.3 years. A good functional result was documented, with a cumulative weighted mean for postoperative Harris Hip Score (HHS) of 87 points. The rate of dislocation in this group was 3.45% and the risk of fracture of an alumina ceramic head was 0.35% (1 study). Squeaking was reported as complication of CoC bearing THA revisions in three studies, with a calculated incidence of 0.52%. Modern CoC bearings show advantages in preclinical and retrospective studies over other bearings also in revision cases and are therefore to be considered a promising alternative for this kind of operation. Reasonable indications for CoC bearing in revision THA are revisions for aseptic loosening or recurrent dislocation in young patients, fractures of ceramic components, large acetabular defects or in patients that are allergic to bone cement components. Nevertheless, prospectively designed or randomized studies are lacking and needed to confirm CoC as optimal solution for revision THA cases.

Midterm Prospective Comparative Analysis of 2 Hard-on-Hard Bearing Total Hip Arthroplasty Designs

IntroductionHard-on-hard (HoH) bearing surfaces in total hip arthroplasty (THA) are commonly utilized in younger patients and may decrease mechanical wear compared to polyethylene bearing surfaces. To our knowledge, no study has prospectively compared the 2 most common HoH bearings, ceramic-on-ceramic (CoC) and metal-on-metal (MoM) THA. Materials and MethodsWe prospectively enrolled 40 patients to undergo an MoM THA and 42 patients to undergo a CoC THA utilizing the same acetabular component. Patients were followed up for a minimum of 2 years. Comparative outcomes included clinical scores, revision or reoperation for any reason, complication rates, and radiographic outcomes. ResultsThe average follow-up was significantly longer in the CoC cohort (94 vs 74 months; P = .005). The CoC cohort had significantly improved Harris Hip Scores (95 vs 84; P = .0009) and pain scores (42 vs 34; P = .0003). The revision (0% vs 31%; P = .0001), reoperation (7.5% vs 36%; P = .004), and complication rates (10% vs 56%; P = .0001) were significantly lower in the CoC cohort. There were no statistically significant differences in radiographic parameters. ConclusionThe clinical outcomes in the CoC cohort exceeded the MoM cohort. It is unlikely that another prospective comparative study of HoH THAs will be conducted. Our midterm results support the use of CoC THA as a viable option that may reduce long-term wear in younger patients. Close surveillance of MoM THA patients is recommended considering the higher failure and complication rates reported in this cohort.

Total Hip Arthroplasty Bearing Surface Trends in the United States From 2007 to 2014: The Rise of Ceramic on Polyethylene

BackgroundWear of the bearing surface is a critical element in determining the longevity of a total hip arthroplasty (THA). Over the past decade, concerns related to modern metal-on-metal (MoM) bearings and corrosion at the femoral head-neck interface have influenced surgeon selection of bearing surfaces. The purpose of this study is to analyze trends in THA bearing surface selection from 2007 through 2014 using a large national database. MethodsThe Nationwide Inpatient Sample database was used to extract bearing surface data from patients who underwent a primary THA between 2007 and 2014. Patients were grouped by bearing surface type: metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), MoM, and ceramic-on-ceramic (CoC) bearings. Descriptive statistics were employed to describe trends. Univariate and multivariate analyses were performed to identify differences between bearing surface groups. ResultsDuring the study period, 2,460,640 THA discharges were identified, of which 1,059,825 (43.1%) had bearing surface data. A total of 496,713 (46.9%) MoP, 307,907 (29.1%) CoP, 210,381 (19.9%) MoM, and 44,823 (4.2%) CoC cases were identified. MoM utilization peaked in 2008 representing 40.1% of THAs implanted that year and steadily declined to 4.0% in 2014. From 2007 to 2014, the use of CoP bearing surfaces increased from 11.1% of cases in 2007 to 50.8% of cases in 2014. In 2014, CoP utilization surpassed MoP which represented 42.1% of bearing surfaces that year. ConclusionDuring the study period, MoM bearing surfaces decreased precipitously, while CoP surpassed MoP as the most popular bearing surface used in a THA.

Increase in Benign Squeaking Rate at Five-Year Follow-Up: Results of a Large Diameter Ceramic-on-Ceramic Bearing in Total Hip Arthroplasty

BackgroundSqueaking is an on-going complication with a variable incidence of 0.5%-20.7%. The mechanism of squeaking has not been understood completely and is most likely multifactorial in nature. Previously, we have reported on a squeaking rate of 7.3% at 2 years. Our current results show a substantial increase in the squeaking incidence from 7.3% to 17.4% with the DeltaMotion articulation at the 5-year follow-up. MethodsTwo hundred six total hip arthroplasties with a large ceramic-on-ceramic bearing were performed on 195 patients by 2 senior authors. The minimum duration of follow-up was 5 years (range 5-6.2). ResultsThe mean Harris Hip Score remained stable at 91.7 at 5 years compared to 92 after 2 years. However, we observed an increase in the squeaking rate from 7.3% after 2 years to 17.4% after 5 years. As in previous studies, we did not find significant differences between the silent and squeaking group in relation to age, height, weight, and femoral head diameter. In contrast, others reported no significant differences regarding range of motion and gender between the silent and the squeaking hip group at 2 years of follow-up, whereas at 5 years, the squeaking group showed a significantly higher combined range of motion and a higher relative risk of squeaking in women compared to the silent group. ConclusionWhile large diameter ceramic bearings may produce squeaking, especially in female patients, our mid-term clinical results of a large ceramic-on-ceramic bearing in total hip arthroplasty are encouraging. Nevertheless, long-term follow-up is recommended.

Increased Serum Ion Levels After Ceramic-on-Metal Bearing Total Hip Arthroplasty: Influence of an Asian Lifestyle

BackgroundRecent clinical studies have suggested that systemic metal ion levels are significantly elevated at midterm follow-up in patients with ceramic-on-metal (COM) bearing. However, it is not clear whether there is a correlation between patient-related factors including the lifestyle and elevated levels of serum metal ions following COM total hip arthroplasty (THA). MethodsSerum metal levels were measured in 201 patients (234 hips) including 121 COM patients (140 hips) and 80 non-COM patients (94 hips). The Harris Hip Score, University of California, Los Angeles activity scale score, and Western Ontario and McMaster Universities Osteoarthritis Index score were measured and radiographs were obtained for the analysis. ResultsSignificantly higher levels of cobalt (Co) and chromium (Cr) were detected in the serum of the COM THA group (Co: 1.86 ± 4.0 μg/L; Cr: 1.81 ± 2.87 μg/L) than those of the non-COM THA group (Co: 0.27 ± 0.14 μg/L; Cr: 0.19 ± 0.25 μg/L; P < .001).The serum metal levels of patients who achieved the squatting position and the kneeling position were significantly higher than those of patients who could not squat (Co: P = .033; Cr: P = .074) and kneel (Co: P = .049; Cr: P = .031). The metal ion levels of the COM THA group correlated with the total range of motion (Co: P = .0293; Cr: P = .0399). ConclusionPatients who underwent a 36-mm COM THA showed high serum metal levels although good clinical outcomes at the midterm follow-up. We found that COM THA patients who were capable of greater range of motion, squatting, and kneeling are at risk of metal ion–related problems.

Early results of 500 primary total hip arthroplasties with a large diameter bearing ceramic monoblock acetabular components

Introduction Ceramic on ceramic (CoC) bearings in total hip arthroplasty (THA) with 32 or 36 mm head sizes have good reported long-term track record. Current manufacturing advancement allow the use of larger head diameters with ceramic monoblock acetabular components. We present the early results of 500 delta ceramic monoblock acetabular components THA with a minimum of 2 years follow up. Materiel et methodes We report the radiographic and clinical follow up of our first consecutive 500 primary THAs where a delta ceramic large diameter bearing monoblock acetabular component was implanted. The acetabular component consists of a titanium (Ti) shell with a biolox delta ceramic liner inserted & locked into the cup by the manufacturer. The bearing diameters corresponds with the acetabular component's size (36–48 mm). Resultats The 500 components have been implanted in 442 patients (250 women, 192 men) with a mean age of 55y. The mean acetabular and femoral head sizes were 54 mm and 44 mm. At a minimum of 2y follow-up (mean 3.8y): 5 (1%) patients have been revised. Causes for revision were: 4 peroperative, undetected, fractures of the femur and only 1 due to early displacement of the acetabular component (0.2%). Other adverse events without revision were: 12 (2.4%) cases of intermittent squeaking which resolved spontaneously, 4 (0.8%) occasional clicking and 1 (0.2%) symptomatic heterotopic ossification. Three (0.6%) suffered from infection. Two (0.4%) had a traumatic hip dislocation without recurrence after closed reduction. The mean postoperative UCLA score was 6.9. The WOMAC score improved from 57.4 to 4.4 postoperatively (P Discussion Early problems reported with CoC are intraoperative liner fracture (handling problem) or postoperative implant fracture secondary to poor taper junction or implant impingement. Noise generation was also a significant problem with some devices. Our resul. Conclusion This prospective study shows the excellent early results of a new design delta ceramic monoblock acetabular component with large diameter CoC bearing which is an alternative to large femoral head metal on metal implants to avoid adverse local reaction to metal debris.

Current Insights Regarding Metal-on-Metal Bearings for Hip Arthroplasty

Modern small diameter metal-on-metal (MoM) bearings for total hip arthroplasty (THA) have been developed in the nineteen-eighties to address the problem of polyethylene wear related osteolysis. Subsequently large diameter MoM hip resurfacings (HRA) were designed for young and active patients to preserve bone and avoid dislocation. Large diameter MoM THA were originally meant as an easy femoral component-only revision solution for femoral neck fractures in HRA, but were then advocated for primary THA as well. In the last decade however, increasing numbers of revisions for adverse local tissues reactions (ALTR) to metal debris have been reported. These ALTR are due to excessive wear of the MoM bearings, usually related to malpositioning of the components leading to edge loading, or in rare cases to metal sensitivity. Besides the immunological reactions, metal particles and ions have a potential local and systemic toxicity. Wear and tribocorrosion at the taper-trunnion connections of MoM THA but also THA with polyethylene and ceramic bearings have also been recognized as a cause of ALTR with extensive tissue destruction. Despite the fact that the long-term survivorship and functional results of certain MoM HRA are excellent and better than THA in the young and active patients group, MoM bearings have become very unpopular and are likely to be replaced by bearing couples of other materials.

Are Trends in Total Hip Arthroplasty Bearing Surface Continuing to Change? 2007-2015 Usage in a Large Database Cohort

BackgroundBearing surface issues related to trunnionosis or metal-on-metal (MoM) articulations have likely impacted recent trends in bearing surface choice. The purpose of this study is to evaluate trends in total hip arthroplasty (THA) bearing surface use, including 2015 data, with respect to the date of operation and patient demographics. MethodsThe Humana dataset was reviewed from 2007 through 2015 to analyze bearing surface usage in primary THA. Four bearing surface types were identified by International Classification of Disease, 10th Revision codes and trended throughout the years: metal-on-polyethylene (MoP), ceramic-on-ceramic (CoC), ceramic-on-polyethylene (CoP), and MoM. Prevalence was analyzed as a function of age and sex. ResultsOf the 28,504 primary THA procedures, the most commonly used bearing was MoP (46.1%), followed by CoP (33.2%), MoM (17.1%), and ceramic-on-ceramic (3.6%). The use of CoP bearings significantly increased from 6.4% in 2007 to 52.0% in 2015, while MoM bearings decreased during this period. MoP bearings decreased over 2012-2015 (P < .001). CoP usage decreased with age, while MoP bearings increased with a transition occurring at 65-69 years of age. Women were more likely to receive MoP bearings (odds ratio [OR] 1.2), while men were more likely to receive MoM and CoP bearings (OR 1.1). Multivariate logistic regression showed age to be an independent predictor of bearing surface choice with patients 65 and older more likely to receive MoP bearings (OR 3.2). ConclusionBearing surface choice in primary THA has changed tremendously from 2007 to 2015. MoM bearing use has decreased as a result of adverse effects. Age continues to remain a significant factor in bearing surface choice.

Ceramic-on-ceramic bearing fractures in total hip arthroplasty: an analysis of data from the National Joint Registry.

Ceramic-on-ceramic (CoC) bearings in total hip arthroplasty (THA) are commonly used, but concerns exist regarding ceramic fracture. This study aims to report the risk of revision for fracture of modern CoC bearings and identify factors that might influence this risk, using data from the National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man. We analysed data on 223 362 bearings from 111 681 primary CoC THAs and 182 linked revisions for bearing fracture recorded in the NJR. We used implant codes to identify ceramic bearing composition and generated Kaplan-Meier estimates for implant survivorship. Logistic regression analyses were performed for implant size and patient specific variables to determine any associated risks for revision. A total of 222 852 bearings (99.8%) were CeramTec Biolox products. Revisions for fracture were linked to seven of 79 442 (0.009%) Biolox Delta heads, 38 of 31 982 (0.119%) Biolox Forte heads, 101 of 80 170 (0.126%) Biolox Delta liners and 35 of 31 258 (0.112%) Biolox Forte liners. Regression analysis of implant size revealed smaller heads had significantly higher odds of fracture (chi-squared 68.0, p < 0.001). The highest fracture risk was observed in the 28 mm Biolox Forte subgroup (0.382%). There were no fractures in the 40 mm head group for either ceramic type. Liner thickness was not predictive of fracture (p = 0.67). Body mass index (BMI) was independently associated with revision for both head fractures (odds ratio(OR) 1.09 per unit increase, p = 0.031) and liner fractures (OR 1.06 per unit increase, p=0.006). We report the largest independent study of CoC bearing fractures to date. The risk of revision for CoC bearing fracture is very low but previous studies have underestimated this risk. There is good evidence that the latest generation of ceramic has greatly reduced the odds of head fracture but not of liner fracture. Small head size and high patient BMI are associated with an increased risk of ceramic bearing fracture. Cite this article: Bone Joint J 2017;99-B:1012-19.

Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints.

Metal-on-metal (MoM) bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII) may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa), a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and prevented the adhesion of wear debris. The results of this study suggest that the CII surface stabilizes the wear status due to the low friction coefficient and low infiltration of partner materials, and these properties also prevent the adhesion of wear debris and inhibit excessive wear. Carbon is considered to be biologically inert; therefore, CII is anticipated to be applicable to the bearing surfaces of MoM prostheses.

Late Dislocations After Total Hip Arthroplasty: Is the Bearing a Factor?

BackgroundDislocation is a leading cause of revision after primary total hip arthroplasty (THA). Although more common in the first few years after the procedure, dislocation can occur at any time. This study investigated the difference in late dislocation in ceramic-on-ceramic (CoC) bearings compared with metal-on-polyethylene and ceramic-on-polyethylene bearings in THA. MethodsData were used from the Australian Orthopaedic Association National Joint Replacement Registry, and the cumulative percent revision for dislocation was estimated using the Kaplan-Meier method for the different bearing surfaces. There were 192,275 THAs included in the study with 101,915 metal-on–cross-linked polyethylene (MoXLPE), 30,256 ceramic-on–cross-linked polyethylene (CoXLPE), and 60,104 CoC. ResultsThe cumulative percent revision for dislocation at 13 years for MoXLPE, CoXLPE, and CoC groups was 1.2 (95% confidence interval [CI], 1.1-1.3), 1.0 (95% CI, 0.7-1.4), and 0.9 (95% CI, 0.8-1.1), respectively. There was an increased risk of revision for dislocation for MoXLPE compared with CoXLPE and CoC. When stratified for head size, there was no difference in the risk of revision for dislocation between MoXLPE, CoXLPE, and CoC in the 28- and 32-mm head sizes. With a head size of 36 mm, MoXLPE had a higher rate of dislocation compared with other materials. ConclusionBearing surface has little impact on revision for dislocation.

Mechanical Stability of the Taper Connection of Large Metal Femoral Heads With Adapter Sleeves in Total Hip Arthroplasty Analyzed Using Explicit Finite Element Simulations

BackgroundLarge diameter heads (LDHs) of metal-on-metal bearings in total hip arthroplasty provide increased range of motion and reduced dislocation rates. However, major concerns grew over high wear rates from the modular connection between femoral stem and head, especially in combination with adapter sleeves. MethodsA computational study on the taper connection stability of LDH (50 mm) with adapter sleeves of different lengths (S, M, L, and XL) compared with a standard femoral head (32 mm) without adapter sleeves was conducted using explicit finite element analyses. Four different impact configurations were considered resulting from varied mallet mass (0.5 vs 1.0 kg) and velocity (1.0 vs 2.0 m/s). The taper stability was evaluated by determination of the pull-off forces and micromotions due to simulated joint loads during walking (2 kN and 7.9 Nm, respectively). Moreover, the deformations of the adapter sleeves and the contact area in the taper connections were evaluated. ResultsAlthough the pull-off forces of the LDH with different-sized adapter sleeves were comparable, contact area decreased and adapter sleeve deformations increased (up to 283%) with an increasing adapter sleeve length. Moreover, the micromotions of LDH with adapter sleeves were up to 7-times higher, as compared with the standard femoral head without an adapter sleeve. ConclusionThe present numerical study confirms that the assembly technique of LDH with adapter sleeves reveals increased micromotions compared with standard femoral head sizes. We could demonstrate that deviations of the stem trunnion geometry and improper surgical instructions led to worse mechanical stability of the taper connection.

Ceramic-on-ceramic bearings in total hip arthroplasty: “The future is now”

Total hip arthroplasty (THA) currently provides durable long-term outcomes, but osteolysis secondary to polyethylene wear debris remains a cause of aseptic loosening and revision. Ceramic-on-ceramic bearings surfaces have a long history of successful clinical use. Reported limitations of ceramic bearings are fracture and squeaking, but their incidence has been reduced through the evolution of fourth-generation ceramic compounds and a greater understanding of the role of component positioning, edge loading and resultant noise generation. The optimum bearing surface is one with very low wear rates, a low coefficient of friction, scratch resistance and is biologically inert. It is also one that can safely accommodate larger femoral head sizes to minimize dislocation rates without damaging the taper junction. Such a material already exists with modern ceramics, making them the ideal bearing material for total hip arthroplasty. “The future is now”.

Equivalent wear performance of dual mobility bearing compared with standard bearing in total hip arthroplasty: in vitro study

Osteolysis in total hip arthroplasty (THA) depends on polyethylene wear and dictates the survival of the prosthesis. Dual mobility in THAs, which is claimed to reduce dislocation risk, has very good long-term clinical results. However, little is known about how the liner wears in this design, compared to the standard single mobility model. A comparative study looking at wear of a conventional ultra-high-molecular-weight polyethylene liner, using gravimetric measurement, between dual mobility implants and standard implants, was performed on a simulator in accordance with a normed protocol based on the same dimensions, environmental conditions and stresses. A linear regression test was employed. Under the same conditions (loading, cycles, sterilization, material and surface roughness), the gravimetric wear (for conventional polyethylene) is comparable between a standard and a dual mobility cup. This correlates to ten year follow-up results of dual mobility cup. This in vitro equivalent wear serves to confirm the very good long-term clinical results observed with dual mobility bearing, whose use should not be restricted by concerns about increased polyethylene wear.

Incidence of Adverse Reactions to Metal Debris From 28-mm Metal-on-Metal Total Hip Arthroplasties With Minimum 10 Years of Follow-Up: Clinical, Laboratory, and Ultrasound Assessment of 44 Cases

BackgroundTotal hip arthroplasty with metal-on-metal (MoM) bearings has been suspected to cause adverse reactions to metal debris (ARMD), with the incidence varying greatly by implant type and patient gender. The prevalence of ARMD from small-diameter MoM bearings in women is unknown, especially after 10 years of follow-up (FU). MethodsCementless 28-mm MoM total hip arthroplasty bearings (Metasul) were implanted consecutively in 42 active women between 1996 and 2002. They were reviewed after a minimum of 10 years' FU with clinical, laboratory, radiological, and ultrasound assessments. ResultsMean FU was 15.9 years (range, 13-18). The mean Postel-Merle d'Aubigné and Oxford scores were 16.9 (range, 13-18) and 15.1 (range, 12-24), respectively, at FU. Mean cup inclination angle was 46.3° (range, 35°-57°). No femoral osteolysis was detected, but limited acetabular osteolysis (11%) over the screw holes occurred in 5 cases. No liquid or solid synovial reactions or ARMD were apparent on ultrasound, even in the 5 cases of pelvic osteolysis. Mean chromium levels were 1.32 μg/L (range, 0.1-7.9) and cobalt levels were 1.85 μg/L (range, 0.35-13.6). Cobalt was >3 μg/L in only 3 cases. The 15.9-year survivorship was 95% (range, 94.1%-98.9%). ConclusionReliable results were obtained with 28-mm MoM bearings, notably in young, active patients. This implant configuration requires very accurate positioning. No ARMD was seen in this group at 16 years' FU.

Patient-Reported Outcomes After Revision of Metal-on-Metal Total Bearings in Total Hip Arthroplasty

BackgroundFailure of metal-on-metal (MOM) total hip arthroplasty (THA) bearings is often accompanied by an aggressive local reaction associated with destruction of bone, muscle, and other soft tissues around the hip. Little is known about whether patient-reported physical and mental function following revision THA in MOM patients is compromised by this soft tissue damage, and whether revision of MOM THA is comparable with revision of hard-on-soft bearings such as metal-on-polyethylene (MOP). MethodsWe identified 75 first-time MOM THA revisions and compared them with 104 first-time MOP revisions. Using prospective patient-reported measures via the Veterans RAND-12, we compared Physical Component Score and Mental Component Score function at preoperative baseline and postoperative follow-up between revision MOM THA and revision MOP THA. ResultsPhysical Component Score did not vary between the groups preoperatively and at 1 month, 3 months, and 1 year postoperatively. Mental Component Score preoperatively and 1 and 3 months postoperatively were lower in patients in the MOM cohort compared with patients with MOP revisions (baseline: 43.7 vs 51.3, P < .001; 1 month: 44.9 vs 53.3, P < .001; 3 months: 46.0 vs 52.3, P = .016). However, by 1 year, MCS scores were not significantly different between the revision cohorts. ConclusionPostrevision physical function in revised MOM THA patients does not differ significantly from the outcomes of revised MOP THA. Mental function is markedly lower in MOM patients at baseline and early in the postoperative period, but does not differ from MOP patients at 1 year after revision. This information should be useful to surgeons and physicians facing MOM THA revision.