Can Dual Mobility Cups Reduce Revision and Dislocation Risks? An Analysis of 107,528 Primary Total Hip Arthroplasties in the United States.

BACKGROUND: Dual mobility acetabular cups (DMC) were designed to increase the effective femoral head size and improve stability with the goal of reducing revision risk at the potential cost of polyethylene thickness. We sought to evaluate revision risk following primary elective total hip arthroplasty with DMC compared to highly cross-linked polyethylene (XLPE). METHODS: A cohort study was conducted using data from a Kaiser Permanente's total joint arthroplasty registry. Patients ≥18 years who underwent primary elective total hip arthroplasty using DMC, unipolar Metal-on-XLPE (MoXLPE), or unipolar Ceramic-on-XLPE (CoXLPE) were identified (2010 to 2021). The final sample comprised 2,219 DMC, 48,251 MoXLPE, and 57,058 CoXLPE. Multiple Cox proportional hazard regressions were used to evaluate aseptic revision and any dislocation regardless of revision within 6 years follow-up. RESULTS: In adjusted analyses, no differences in aseptic revision risk were observed for MoXLPE (hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 0.72 to 1.51) or CoXLPE (HR = 0.98, 95% CI = 0.69 to 1.40) compared to DMC. No differences in dislocation risk were observed for MoXLPE (HR = 1.42, 95% CI = 0.93 to 2.15) or CoXLPE (HR = 1.25, 95% CI = 0.84 to 1.87) compared to DMC. CONCLUSIONS: In a US-based cohort, 6-year aseptic revision risk of DMC was similar to metal or ceramic femoral head unipolar constructs. Furthermore, no difference in dislocation risk was observed. Continued longer-term follow-up may reveal if there is a reduced risk of dislocation that comes at the cost of increased late revision. LEVEL OF EVIDENCE: Level III.

In Vivo Oxidation and Wear in Remelted Highly Cross-Linked Polyethylene Liners Retrieved at a Minimum of 10 Years After Total Hip Arthroplasty.

BACKGROUND: With the decreasing age threshold for patients undergoing total hip arthroplasty (THA), there is an escalating demand for enhanced polyethylene durability. Although reports assessing wear in remelted highly cross-linked polyethylene (HXLPE) through radiographic imaging exist, a consensus regarding its oxidation level is lacking. This study investigated the wear, oxidation levels, and degradation of remelted HXLPE that was retrieved at least 10 years after THA. METHODS: Our analysis focused on 7 cases of melted HXLPE liners retrieved ≥10 years after THA. All patients were women, who had an average age of 64 ± 6.5 years at the initial operation, and the mean postoperative period after THA was 12 years and 11 months ±1 year and 5 months. The wear conditions were measured by matching the shape analysis data obtained from a coordinate-measuring machine with a spherical model. Fourier-transform infrared spectroscopy was used to study the oxidation of polyethylene, and the polyethylene structure was evaluated using scanning electron microscopy. RESULTS: Osteolysis was not observed in any case on X-rays, computed tomography, or intraoperative findings during revision surgery. The average oxidation index (OI) of the sliding surface under load was 0.31 ± 0.22 in the 6 cases calculated after hexane treatment, and 0.69 for one case without hexane treatment. In the 6 cases calculated after hexane treatment, the average OI of the non-load-bearing sliding surface was 0.11 ± 0.20. Average wear values were 0.33 ± 0.11 mm at 45 degrees from the equatorial direction and 0.04 ± 0.07 mm in the opposite direction. The initial structure of the polyethylene was preserved at all sites with low oxidation levels; however, in one case with stem subsidence, morphological changes and a high OI were observed. CONCLUSIONS: Long-term oxidation and wear of remelted HXLPE liners retrieved from THA patients were minimal.

Highly Cross-Linked Polyethylene in Patients 50 Years of Age and Younger: A 20-year Follow-Up Analysis.

BACKGROUND: Highly cross-linked polyethylene (HXLPE) has been an excellent bearing for total hip arthroplasty (THA) due to improved wear characteristics compared to conventional materials. Patients 50 years of age or younger are at high risk for wear-related complications of their THA, and few studies have followed these patients who have HXPLE into the third decade. METHODS: In a retrospective review of 88 consecutive THAs performed in 77 patients aged 50 years and younger (mean 41; range, 20 to 50), in which HXLPE was utilized, they were evaluated for their clinical and radiographic results at an average of 20-year follow-up (range, 18 to 24). The current study reports on longer-term follow-up from our previously published series at shorter follow-up times. Patients were categorized by femoral head material: cobalt chrome (n = 14), ceramic (n = 30), and oxidized zirconium (n = 22) and by femoral head size: 26 mm (n = 12), 28 mm (n = 46), and 32 mm (n = 8). Harris Hip Scores were collected preoperatively and at the most recent follow-up. Radiographs were evaluated for linear and volumetric wear, radiolucent lines, and osteolysis. RESULTS: Mean Harris Hip Scores improved from 47.1 (standard deviation [SD] 8.8) preoperatively to 92.0 (SD 7.7) (P < .0001) at 20-year follow-up. There was one hip that was revised for recurrent instability, and no hip demonstrated radiographic evidence of loosening or osteolysis. The mean polyethylene linear wear rate was 0.017 (SD 0.012) mm/y, and the mean polyethylene volumetric wear rate was 3.15 (SD 2.8) mm3/year, with no significant differences based on articulation type or head size. CONCLUSIONS: Total hip arthroplasty with HXLPE in patients ≤ 50 years of age continues to demonstrate excellent long-term clinical and radiographic outcomes with low wear characteristics at 20-year follow-up, regardless of femoral head material or size.

No Revisions Attributable to Wear of Highly Cross-Linked Polyethylene Liners: A Long-Term Follow-Up Study.

BACKGROUND: There is a paucity of data beyond 15 years on the survivorship of total hip arthroplasty since the introduction of highly cross-linked polyethylene (HXLPE) liners. Our aim was to evaluate implant survivorship, liner wear rates, and clinical outcomes after primary total hip arthroplasty using HXLPE liners implanted between 1999 and 2002. METHODS: Between 1999 and 2002, 690 primary total hip arthroplasties utilizing 28-mm femoral heads and HXLPE liners of a single design were identified using our institutional total joint registry. Femoral heads were made of metal in 96% of cases and ceramic in 4%. The mean age was 56 years, 48% were women, and the mean body mass index was 30. Survivorship analyses were performed for the outcomes of implant revision, reoperation, and complications for the entire cohort. Linear HXLPE liner wear rates were determined on 197 hips with radiographs with more than 18.5 years of follow-up. RESULTS: At 20 years, survivorship free of revision was 94%, free of reoperation was 92%, and free of any complication was 81%. There were no documented wear-related revisions. The linear wear rate at a mean of 20.3 years postoperatively was 0.02 mm/y. There was no statistically significant difference in measured wear observed between the first available postoperative radiographs and those taken at the final follow-up. The use of elevated liners, patient body mass index, age, preoperative diagnosis, acetabular component inclination, and anteversion angles were not associated with increased wear rates. Mean Harris hip scores improved from 52 preoperatively to 90 at greater than 18.5 years CONCLUSIONS: Primary total hip arthroplasties using a single first-generation HXLPE liner demonstrated excellent survivorship and clinical outcomes at long-term follow-up with no wear-related revisions. Wear rates of HXLPE liners at 20 years are exceedingly low and are not significantly impacted by acetabular component position or patient-dependent variables such as BMI. LEVEL OF EVIDENCE: IV.

Mean 16-Year Results of Total Hip Arthroplasty With Alumina Ceramic Femoral Heads on Highly Cross-Linked Polyethylene in Patients 50 Years or Less.

BACKGROUND: Highly cross-linked polyethylene (HXLPE) is a widely used bearing surface in total hip arthroplasty (THA); long-term results in young patients are limited. We previously demonstrated excellent results in HXPLE on cobalt-chrome femoral heads at 15-year mean follow-up. The purpose of the present study was to investigate polyethylene wear rates, implant survivorships, wear-related revisions, and patient-reported outcomes (PROs) in a young patient cohort who had alumina ceramic on HXPLE coupling at an average 16-year follow-up. METHODS: This was a retrospective study of 128 hips that underwent THA with HXLPE on alumina ceramic bearings between March 1, 2004, and April 15, 2007. The patient's mean age was 38 years (range, 13 to 50). All THAs utilized HXPLE liners with alumina ceramic heads. The University of California, Los Angeles activity score and modified Harris hip scores were collected preoperatively and at each follow-up. Martell hip analysis suite was used for wear calculations. RESULTS: At average 16 years (range, 13 to 18), aseptic revision survivorship was 93.3% and osteolysis/wear survivorship was 99.2%. The mean linear wear rate was 0.0191 mm/year and mean volumetric wear rate was 19.43 mm3/y, both of which were clinically undetectable. We observed excellent PROs with a significant increase in mean modified Harris hip scores (43.6 to 87.4, P < .0001) and the University of California, Los Angeles activity scores (4.0 to 6.0, P < .0001). There were no statistically significant differences in PROs or wear rates between ceramic and cobalt-chrome groups. CONCLUSION: At a mean 16-year follow-up, young patients who had HXLPE on ceramic coupling had excellent wear properties, PROs, and acceptable survivorships.

Polyethylene Dual Mobility Liners Show Minimal Polyethylene Changes in Early Retrievals.

BACKGROUND: Dual mobility (DM) liners were introduced to reduce instability in total hip arthroplasty. They were found to allow for motion predominantly at the femoral head and the inner bearing of the acetabular liner; however, little is known if this motion is sufficient to alter polyethylene material characteristics. We assessed cross-link (XL) density and oxidation index (OI) measurements of the inner and outer bearing articulations. METHODS: Thirty-seven DM liners were collected with a duration of implantation greater than 2 years. Clinical and demographic data were collected from a chart review. A cylinder was cored from the apex of each liner and cut into 4.5 mm long inner and outer diameter segments for XL density swell ratio testing. The OI was measured from sagittal 100 µm microtome slices using Fourier transform infrared spectroscopy. Student's t-tests were used to determine differences in OI and XL density between the bearings. Spearman's correlation assessed relationships between patient demographics, OI, and XL density. Duration of implantation for the cohort was a mean of 35 (range, 24-96) months. RESULTS: The inner and outer bearing had similar median XL densities (0.17 mol/dm3 versus 0.17 mol/dm3, P = .6). The inner bearing had an increased OI when compared to the outer bearing (0.16 versus 0.13, P = .008). The OI was inversely correlated with XL density (r = -0.50, P = .002). CONCLUSION: Small differences were found in oxidation between the inner and outer bearing of the DM construct. Failures at an average of 3 years indicate low levels of oxidation, unlikely to impact the mechanical properties of the material.

A Review of Early In Vivo Performance of Antioxidant Stabilized Polyethylene for Total Knee Arthroplasty.

BACKGROUND: The incorporation of antioxidants into highly cross-linked polyethylene (HXLPE) has emerged as an alternative to postirradiation thermal treatments for improving oxidation resistance. Currently, use of antioxidant stabilized HXLPE (AO-XLPE) in total knee arthroplasty (TKA) is increasing. In this literature review, we asked: (1) How does the clinical performance of AO-XLPE compare to conventional ultra-high molecular weight polyethylene (UHMWPE) or HXLPE for TKA? (2) What material changes occur in vivo for AO-XLPE in TKA? and (3) What is the risk of revision for AO-XLPE in TKA? METHODS: We performed a search of the literature according to the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines using PubMed and Embase. Included studies reported the in vivo behavior of vitamin E-doped polyethylene in TKA. We reviewed 13 studies. RESULTS: Across the studies, clinical results including revision rates, patient-reported outcome measurement scores, and the occurrence of osteolysis or radiolucent lines tended to be similar for AO-XLPE as compared to conventional UHMWPE or HXLPE controls. In retrieval analyses, AO-XLPE exhibited excellent resistance to oxidation and typical surface damage. Survival rates were positive and not significantly different from conventional UHMWPE or HXLPE. There were no cases of osteolysis for AO-XLPE and no revision due to polyethylene wear reported. CONCLUSION: The purpose of this review was to provide a comprehensive overview of the literature regarding the clinical effectiveness of AO-XLPE in TKA. Overall, the results of our review indicated positive early-to mid-term clinical performance for AO-XLPE in TKA and similar outcomes as compared to conventional UHMWPE and HXLPE.

Comparative Study of Highly Cross-Linked Polyethylene Liner Wear by Hip Center Location Using Elevated Hip Center Technique in Crowe I to III Hip Dysplasia: Outcomes for a Minimum of Eighteen Years of Follow-Up.

BACKGROUND: The literature has reported that supero-lateralization of the femoral head increases the rates of aseptic loosening and prosthesis revision. However, there are few reports on the influence of different hip center positions on liner wear with more than a 15-year follow-up period. METHODS: From April 2000 to August 2003, 91 patients underwent 108 total hip arthroplasties using a highly cross-linked polyethylene liner combined with zirconia femoral head and cup components. Pelvic radiographs were used to assess the vertical and horizontal distances to the center of the hip and the amount of liner wear. Mean patient age at the time of surgery was 54 years (range, 33 to 73), and mean follow-up duration was 19 years (range, 18 to 21). RESULTS: Average liner wear was 0.221 mm, with average annual wear of 0.012 mm/year. Mean vertical and horizontal distances for the hip center were 24.9 and 31.8 mm, respectively. There was no difference in linear wear between patients who had different hip center heights (<20, 20 to 30, and >30 mm), and quadrant partitioning showed no differences across the 4 quadrant zones. CONCLUSION: At a minimum of 18 years of follow-up in patients having developmental dysplasia of the hip who had different Crowe subtypes and different hip centers, elevated hip center and uncemented fixation techniques using a highly cross-linked polyethylene on ceramic components were associated with very low wear rates and excellent functional scores.

Is Highly Cross-Linked Polyethylene Safe for Use in High-Flexion Posterior Stabilized Total Knee Arthroplasty?

BACKGROUND: Application of highly cross-linked polyethylene (HXLPE) to a posterior cruciate-substituting total knee arthroplasty (TKA) might add the risk of fracture and failure of the tibial polyethylene insert. The purpose of this study is to evaluate the long-term (up to 19 years) clinical and radiographic results of posterior cruciate-substituting TKAs with HXLPE or conventional polyethylene. METHODS: This study analyzed the results of 1,217 patients (444 men and 773 women; mean age of 65 ± 7 years, range, 31-85) (2,434 knees) who had received a NexGen LPS-Flex prosthesis with a conventional tibial insert in one knee and the same prosthesis with an HXLPE tibial insert in the contralateral knee. The mean duration of follow-up was 17 years (range, 15-19). RESULTS: The 2 groups did not differ significantly (P > .05) with regard to the clinical and radiographic results. No knee in either group had a fracture of the tibial polyethylene post or failure of the locking mechanism of the tibial polyethylene insert or osteolysis. Twenty-eight knees (2.3%) in the HXLPE group and 26 knees (2.1%) in the conventional polyethylene group were revised. The estimated survival rate at 17 years was 97.7% in the HXLPE group and 97.9% in the conventional polyethylene group. CONCLUSION: The data suggest that clinical and radiographic findings at a mean of 17 years after posterior cruciate-substituting TKA are the same for patients treated with HXLPE and those treated with conventional polyethylene.

Long-term outcome of primary total hip arthroplasty with cementless bioactive glass ceramic bottom-coated implants and highly cross-linked polyethylene: A minimum 10-year analysis.

BACKGROUND: Cementless glass ceramics containing apatite and wollastonite (AW-GC) bottom-coated titanium hip implants were developed; early excellent clinical and radiographic results have been reported previously. This study aimed to investigate the long-term clinical and radiographic outcomes in detail, and the wear rate of HXLPE. METHODS: We retrospectively evaluated 99 patients (117 hips) between November 2001 and December 2007. The survival rate was estimated using the Kaplan-Meier method. Hip joint function was evaluated using the Japanese Orthopaedic Association (JOA) score. The extent of radiographic signs was determined from the radiographs performed at the last follow-up. Polyethylene wear was measured using Martell's Hip Analysis Suite. We assessed the possible factors affecting the steady-state linear wear rate. RESULTS: The mean follow-up period was 14.8 ± 2.1 (10-18.6) years. The mean JOA score improved to 88.7 ± 9.4 (59-100) at the final follow-up from 47.8 ± 12.5 (17-76) before surgery. The overall survival rate with the end point of all-cause revision and wear-related revision was 99% and 100% respectively. There was no osteolysis or loosening of either the acetabular or femoral component. All hips were classified as having bone ingrowth fixation. The mean steady-state wear rate was 0.008 ± 0.025 mm/year. We found no significant correlation between the wear rate and age, body weight, body mass index, cup inclination and femoral head size. CONCLUSION: The combination of AW-GC bottom-coated implants and HXLPE showed excellent implant survival and wear resistance for 15 years.

No higher tibial post fracture rate with highly cross-linked polyethylene inserts in total knee arthroplasty at a minimum 10-year follow-up.

PURPOSE: The purpose of this study was to assess tibial post fracture between highly cross-linked polyethylene (HXPE) and conventional polyethylene inserts in consecutive posterior-stabilized (PS) total knee arthroplasty (TKA) over a minimum 10-years follow-up period. METHODS: Between July 2008 and December 2011, a consecutive series of 3264 primary TKAs was performed in 2098 patients using a PS total knee prosthesis at a single institution. The final cohort was classified into the HXPE group (792 cases) and the conventional group (2113 cases) according to insert material used during the procedure. RESULTS: The mean follow-up period was 11.4 years in the HXPE group and 11.8 years in the conventional group. Both cases of tibial post fracture occurred in the HXPE group, a complication rate of 0.25%. These two cases required replacement with a thicker tibial insert with retention of the femoral and tibial components. There were no cases of tibial post fracture in the conventional group. CONCLUSION: There was no difference in tibial post fracture rate between the HXPE group and the conventional group in PS TKA on long-term follow-up. LEVEL OF EVIDENCE: IV.

Wear analysis of the first-generation cross-linked polyethylene at minimum 10 years follow-up after THA: no significant effect of sports participation.

The impact of sports on long-term wear of highly cross-linked polyethylene (XLPE) after total hip arthroplasty (THA) is not fully understood. We investigated (1) the wear performance of the first-generation XLPE, and (2) whether sports participation influences the steady wear rate of XLPE. The femoral head penetration into the cup was measured digitally on radiographs of hips undergoing THA with XLPE. We retrospectively reviewed data that included age, gender, body mass index, follow-up period, preoperative diagnosis, types of XLPE, ball diameter, head material, inclination of the cup, physical function score, and sports participation. Statistical analyses were applied to determine whether sports affect the wear of XLPE and which factors were associated with the steady wear rate. Creep and steady wear rate were found to be 0.18 mm and 0.005 mm/year, respectively. Sports participation, regardless of impact, provided no significant difference in the steady wear rate. Multiple regression analysis demonstrated that sports did not increase the steady wear rate. Our findings showed excellent wear performance of the first-generation XLPE at a minimum of ten years after THA, without significant effect of sports participation on the liner wear.

High rate of tibial post-fracture in highly cross-linked polyethylene compared to conventional polyethylene in posterior-stabilized total knee arthroplasty at a minimum 12-year follow-up.

PURPOSE: The purpose of this study was to assess tibial post-fracture between highly cross-linked polyethylene (HXPE) and conventional polyethylene inserts in consecutive posterior-stabilized (PS) total knee arthroplasty (TKA) over a minimum 12-year follow-up period. METHODS: Between January 2007 and June 2008, a consecutive series of 2446 primary TKAs was performed in 1478 patients at a single institution. The final cohort was classified into two groups (1559 in the HXPE group and 887 in the conventional group) based on the insert material used during the procedure. RESULTS: The mean follow-up period was 13.1 years in the HXPE group and 13.4 years in the conventional group. All 16 cases of tibial post-fracture occurred in the HXPE group. This complication rate was 1.03%. The mean elapsed time from primary TKA to the diagnosis of post-fracture was 3.9 years (range 0.5-10.0 years). Ten cases required replacement with a thicker polyethylene insert, and six cases underwent tibial revision surgery. There were no cases of tibial post-fracture in the conventional group. CONCLUSION: Tibial post-fracture is not a rare complication in PS TKA with HXPE. Therefore, the possibility of a tibial post-fracture should be considered if newly developed pain, acute subluxation, effusion, patellar clunking, or instability occurs in patients treated with PS Scorpio knee system TKA using an HXPE insert. LEVEL OF EVIDENCE: IV.

Low Wear at 10-Year Follow-Up of a Second-Generation Highly Cross-Linked Polyethylene in Total Hip Arthroplasty.

BACKGROUND: Characterizations and factors influencing longer term performance of second-generation sequentially irradiated and annealed highly cross-linked polyethylene (HXLPE) are lacking. We evaluated patients who underwent total hip arthroplasty with HXLPE at mean 10-year follow-up for (1) linear and volumetric wear rates, (2) patient and implant characteristics, (3) implant survivorships, and (4) functional scores. METHODS: We evaluated 130 hips (110 patients) that received HXLPE acetabular liners at a single center. The mean age was 56 years (range, 20-79 years), with a mean follow-up of 10 years (range, 8-15). Radiographic linear (millimeters/year) and volumetric (cubic millimeters/year) wear rates were quantified using radiographic analysis. Survivorship was assessed by all-cause and wear-related revision rates. Functional outcomes were assessed by Short Form 12 and modified Harris Hip Scores. RESULTS: The mean linear wear rate was 0.02 ± 0.03 mm/y, and the mean volumetric wear rate was 12.6 ± 5.3 mm3/y. Younger age had higher volumetric wear (total and yearly, P = .01). Increasing body mass index trended toward higher total and yearly linear (both, P ≤ .09) and volumetric wear (both, P ≤ .07). Ten patients required revisions, with an all-cause survivorship of 92% and a wear survivorship of 100%. The mean modified Harris Hip Scores was 84, and the mean Short Form 12 scores were 46 (physical) and 55 (mental). CONCLUSION: We observed low linear and volumetric wear rates for HXLPE at 10-year mean follow-up. Younger age and higher body mass index at the time of surgery may be important patient characteristics influencing long-term wear. These results illustrate the potential for this second-generation HXLPE to be an appropriate long-term total hip arthroplasty interface.

Large Femoral Heads in Total Hip Arthroplasty With Vitamin E Highly Cross-Linked Polyethylene: Head Penetration Rates Compared to Highly Cross-Linked Polyethylene.

BACKGROUND: Highly cross-linked polyethylene with vitamin E (VE-HXLPE) has shown superior tribological properties and has been rapidly adopted in total hip arthroplasty. However, the majority of studies compare VE-HXLPE to conventional or moderately cross-linked polyethylene using standard femoral head sizes. This study's purpose was 2-fold: (1) compare radiographic femoral head penetration (FHP) between VE-HXLPE and HXLPE and (2) evaluate FHP in large femoral heads ≥40 mm. METHODS: One hundred forty-two consecutive primary total hip arthroplasties using ceramic femoral heads (n = 84 VE-HXLPE; n = 58 HXLPE) in a single implant system were retrospectively reviewed. FHP was measured radiographically utilizing Martell method at 4-week, 1-year, and latest radiographs. FHP, cup position, and demographic variables were compared between VE-HXLPE and HXLPE liners. RESULTS: Median linear FHP was lower for VE-HXLPE compared to HXLPE during the initial "bedding-in" period between 4-week and 1-year (0.383 vs 0.551 mm, P = .650) and between 1-year and latest follow-up (0.131 vs 0.270 mm/y, P = .636) although without statistical significance. Acetabular cup inclination and anteversion did not influence linear or volumetric FHP (P ≥ .204). Large femoral heads (≥40 mm) were predictive of higher FHP during the early bedding-in period (P ≤ .025) but did not have an effect beyond 1 year in multivariate regression with numbers available. No radiographic osteolysis was observed in any case. CONCLUSION: These findings support others that VE-HXLPE is the optimal polyethylene bearing surface to minimize FHP during the bedding-in period and beyond. Surprisingly, large ceramic femoral heads appear to influence FHP during the initial bedding-in period but do not increase FHP beyond 1 year. Further longer term follow-up remains warranted. LEVEL OF EVIDENCE: III.

Polyethylene wear of dual mobility cups: a comparative analysis based on patient-specific finite element modeling.

PURPOSE: Concerns remain about potential increased wear with dual mobility cups related to the multiple articulations involved in this specific design of implant. This finite element analysis study aimed to compare polyethylene (PE) wear between dual mobility cup and conventional acetabular component, and between the use of conventional ultra-high molecular weight PE (UHMWPE) and highly cross-linked PE (XPLE). METHODS: Patient-specific finite element modeling was developed for 15 patients undergoing primary total hip arthroplasty (THA). Five acetabular components were 3D modeled and compared in THA constructs replicating existing implants: a dual mobility cup with a 22.2-mm-diameter femoral head against UHMWPE or XLPE (DM22PE or DM22XL), a conventional cup with a 22.2-mm-diameter femoral head against UHMWPE (SD22PE) and a conventional cup with a 32-mm-diameter femoral head against UHMWPE or XLPE (SD32PE or SD32XL). RESULTS: DM22PE produced 4.6 times and 5.1 times more volumetric wear than SD32XL and DM22XL (p < 0.0001, Cohen's d = 6.97 and 7.11; respectively). However, even if significant, the differences in volumetric wear between DM22XL and SD32XL as well as between DM22PE and SD22PE or SD32PE were small according to their effect size (p < 0.0001, Cohen's |d|= 0.48 to 0.65) and could be therefore considered as clinically negligible. CONCLUSION: When using XLPE instead of UHMWPE, dual mobility cup with a 22.2-mm-diameter femoral head produced a similar amount of volumetric wear than conventional acetabular component with a 32-mm-diameter femoral head against XLPE. Therefore, XLPE is advocated in dual mobility cup to improve its wear performance.

Minimum 10-Year Follow-Up of Cementless Total Hip Arthroplasty With a 32-mm Cobalt-Chromium Head on Highly Cross-Linked Polyethylene and a Tapered, Fiber Metal Proximally Coated Femoral Stem.

BACKGROUND: The clinical and radiographic results of cementless total hip arthroplasty using a 32-mm cobalt-chromium head on remelted highly cross-linked polyethylene (HXLPE) and a tapered, fiber metal proximally coated femoral stem were evaluated at a mean follow-up of 12 years. METHODS: A total of 57 cementless total hip arthroplasties using remelted HXLPE combined with a 32-mm cobalt-chromium head, and a tapered, fiber metal proximally coated femoral stem were performed from October 2004 to December 2006. Clinical evaluation was performed using the Merle d'Aubigné and Postel scoring system. Standardized anteroposterior and lateral radiographs of the pelvis and femur without weight-bearing were analyzed. Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up. RESULTS: The mean Merle d'Aubigné and Postel score improved significantly from 10.7 points preoperatively to 15.6 postoperatively (P < .001). No osteolysis was found around the implant. Stem fixation in all cases showed stable bone ingrowth. Third-degree stress shielding was found in 46% of all stems. The total head penetration rate was 0.05 mm/y, and the steady-state wear rate was 0.01 mm/y. The Kaplan-Meier survivorship with the end point of revision was 95% (95% confidence interval, 85%-98%) at 12 years. CONCLUSION: A 32-mm cobalt-chromium head on remelted HXLPE demonstrated low wear properties, and a tapered, fiber metal proximally coated femoral stem showed good results at long-term follow-up.

Thirteen-year results of cementless total hip arthroplasty with zirconia heads on highly cross-linked polyethylene.

OBJECTIVES: Zirconia ceramic was introduced for femoral heads because of its mechanical strength and fracture toughness. Highly cross-linked polyethylene has been shown to achieve wear reduction compared to conventional polyethylene. The purpose of this study was to investigate the long-term results of cementless total hip arthroplasty with zirconia femoral heads on highly cross-linked polyethylene. METHODS: Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method (PolyWare) in 93 hips at a mean follow-up of 13 years. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up. RESULTS: The mean Merle d'Aubigné and Postel score had improved significantly from 10.9 points preoperatively to 15.3 postoperatively (p < 0.001). Osteolysis was not found around the implant, and no zirconia heads had fractures. The total head penetration rate was 0.04 mm/year, and the steady-state wear rate was 0.02 mm/year. Kaplan-Meier survivorship with the endpoint of revision was 97% (95% confidence interval [CI], 92% to 99%) at 10 years. CONCLUSION: Zirconia on highly cross-linked polyethylene demonstrated extremely low wear properties at long-term follow-up.

Early failure for wear after ceramic-on-highly cross-linked polyethylene total hip arthroplasty: a case report.

BACKGROUND: Highly cross-linked polyethylene (HXLPE) enhances the anti-wear characteristics of the conventional polyethylene (PE). Early failure for wear after ceramic-on-highly cross-linked polyethylene (CoHXLPE) total hip arthroplasty (THA) is extremely rare. CASE PRESENTATION: We described the case of a 60-year-old man who underwent right CoHXLPE THA because of the developmental dysplasia hip (DDH) complained pain 32 months after this procedure. Plain radiographs showed that eccentric wear existed at the polyethylene insert. However, the patient refused surgery at that time and did not stop weight-bearing. The right hip pain continued for 7 months. Plain radiographs of the pelvis showed that the HXLPE liner was penetrated and partial inner wall of acetabular shell was worn. Acetabular cup revision was performed, and the ceramic head and HXLPE were exchanged. CONCLUSIONS: Difficult reduction during primary THA, especially for DDH, can result in higher abductor tension, which may lead to early eccentric wear of the prosthesis. Whenever eccentric wear of HXLPE liner was found, weight-bearing must be stopped to avoid the accelerated wear and adverse reactions to metal debris (ARMD).

Highly Cross-Linked Polyethylene in Total Hip Arthroplasty in Patients Younger Than 50 Years With Osteonecrosis of the Femoral Head: A Minimum of 10 Years of Follow-Up.

BACKGROUND: Polyethylene wear and subsequent periprosthetic osteolysis remain a major concern of total hip arthroplasty (THA) failure in young, active patients with osteonecrosis of the femoral head (ONFH). The literature is lacking regarding the long-term performance of highly cross-linked polyethylene (HXLPE) in these patients. The purpose of this study is to evaluate long-term results for cementless THA using metal-on-HXLPE bearing couplings in patients younger than 50 years with ONFH. METHODS: We retrospectively evaluated the clinical and radiographic results of a consecutive series of 85 THAs (in 67 patients) performed with HXLPE liners (Durasul) in patients younger than 50 years who had ONFH. All procedures were performed at a single institution by a single surgeon using the same type of implants. The minimum duration of follow-up was 10 years (mean, 13.5 years; range, 10-17.3 years). Wear was measured using computer software. Osteolysis was evaluated with the use of radiography and computed tomography. RESULTS: The mean Harris hip score was 49.3 points (range, 26-68 points) before surgery, which improved to 93.6 points (range, 87-98 points) after surgery. Neither femoral nor acetabular components displayed mechanical loosening, and no components had been revised by the final follow-up evaluation. Radiographs and computed tomography scans did not demonstrate osteolysis. The mean liner wear was 0.037 mm/y (range, 0-0.099 mm/y). With the data available, univariate regression analysis did not demonstrate that age, sex, weight, activity level, underlying cause of osteonecrosis, liner thickness, or cup inclination had any influence on liner penetration. CONCLUSION: Although the long-term effects of HXLPE particles remain unknown, the implant survivorship rate and wear rate in our study are promising and support the continued use of metal-on-HXLPE bearing couplings in these high-risk patients because they do not produce any of the issues associated with hard-on-hard couplings. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.