Liner In Total Hip Arthroplasty Research Articles

Third-Generation Medium Cross-Linked Polyethylene Demonstrates Very Low Wear in Total Hip Arthroplasty.

BackgroundCross-linked polyethylene (XLPE) liners have shown lower wear rates than conventional polyethylene liners in total hip arthroplasty. The primary aim of our study was to report our most recent analysis of wear rates and clinical outcomes of a third-generation XLPE liner. Secondary aims were to investigate the rate of adverse events related to mechanical failure or oxidation of this liner.MethodsA series of 266 total hip arthroplasties using a specific XLPE liner were retrospectively reviewed. Radiographs were examined to determine linear and volumetric wear rates and presence of osteolysis. Clinical outcomes, revision rates, mechanical failures, and risk factors for accelerated polyethylene wear were additionally investigated.ResultsThe mean age at the time of surgery was 65.8 years and the mean follow-up was 5.5 years. The mean linear wear rate was 0.003 mm/year and the mean volumetric wear rate was 0.42 mm3/year, and there was no evidence of osteolysis. Harris hip scores increased from 50.9 preoperatively to 96.0 at the latest follow-up. The revision rate was 0.4%, with no liner rim fractures and no liner dissociations/loosenings. Femoral head material, head size, age, body mass index, and time since implantation had no effect on wear rates.ConclusionWear rates for this third-generation XLPE liner were low at mid-term follow-up, and no adverse sequelae of oxidation or deleterious mechanical properties were observed. This remained true regardless of femoral head size and material or patient age and body mass index. Further analysis will be necessary to ensure continued wear resistance, oxidative stability, and mechanical strength at long-term follow-up.

Vitamin E-blended highly cross-linked polyethylene liners in total hip arthroplasty: a randomized, multicenter trial using virtual CAD-based wear analysis at 5-year follow-up.

Progressive oxidation of highly cross-linked ultra-high molecular weight (UHMPWE-X) liners is considered to be a risk factor for material failure in THA. Antioxidants such as vitamin E (alpha-tocopherol) (UHMWPE-XE) were supplemented into the latest generation of polyethylene liners. To prevent inhomogenous vitamin E distribution within the polymer, blending was established as an alternative manufacturing process to diffusion. The purpose of the present study was to investigate the in vivo wear behavior of UHMWPE-XE in comparison with conventional UHMWPE-X liners using virtual CAD-based radiographs. Until now, 94 patients from a prospective, randomized, controlled, multicenter study were reviewed at 5-year follow-up. Of these, 51 (54%) received UHMWPE-XE and 43 (46%) UHMWPE-X liners. Anteroposterior pelvic radiographs were made immediately after surgery and at 1 and 5years postoperatively. The radiographs were analyzed using the observer-independent analysis software RayMatch® (Raylytic GmbH, Leipzig, Germany). The mean wear rate was measured to be 23.6μm/year (SD 13.7; range 0.7-71.8μm). There were no significant differences between the two cohorts (UHMWPE-X: 23.2μm/year vs. UHMWPE-XE: 24.0μm/year, p = 0.73). Cup anteversion significantly changed within the 1styear after implantation independent from the type of polyethylene liner [UHMWPE-X: 18.2-23.9° (p = 0.0001); UHMWPE-XE: 21.0-25.5° (p = 0.002)]. No further significant changes of cup anteversion in both groups were found between year 1 and 5 after implantation [UHMWPE-X (p = 0.46); UHMWPE-XE (p = 0.56)]. The present study demonstrates that the addition of vitamin E does not adversely affect the midterm wear behavior of UHMWPE-X. The antioxidative benefit of vitamin E is expected to become evident in long-term follow-up. Cup anteversion increment by 5° within the 1st year is likely a result of the released hip flexion contracture resulting in an enhanced posterior pelvic tilt. Therefore, a reassessment of target values in acetabular cup placement might be considered.

Femoral Head Penetration Rates of Second-Generation Sequentially Annealed Highly Cross-Linked Polyethylene at Minimum Five Years

BackgroundHighly cross-linked polyethylene (HXLPE) liners in total hip arthroplasty (THA) have demonstrated decreased wear rates, resilience to cup orientation, and reduced osteolysis compared to conventional polyethylene. Sequential irradiation and annealing below the melting temperature is unique compared to most HXLPE which is irradiated and remelted. This study purpose is to provide minimum 5-year femoral head penetration rates of sequentially annealed HXLPE in primary THA. MethodsA retrospective review of a prospectively collected database identified 198 consecutive, cementless primary THAs utilizing sequentially annealed HXLPE (X3; Stryker, Mahwah, NJ). Operative technique was standardized. Radiographs were analyzed utilizing the Martell method with minimum 5-year and 1-year radiographs as baseline to minimize the initial bedding-in period. ResultsSeventy-seven hips with minimum 5-year follow-up were analyzed. Mean steady state linear and volumetric head penetration rates were 0.095 mm/y and 76 mm3/y, respectively. Volumetric head penetration was significantly less for 32-mm compared to 36-mm (P = .028). In addition, less head penetration was observed for ceramic 32-mm heads at nearly half the rate compared to cobalt-chromium 36-mm heads (P ≥ .092). No correlations existed between penetration rates and age, body mass index, University of California Los Angeles Activity Level, polyethylene thickness, cup inclination, or anteversion (P ≥ .10). No radiographic osteolysis was observed. ConclusionSurprisingly, linear head penetration rates of sequentially annealed HXLPE were nearly identical to the osteolysis threshold for conventional polyethylene and greater than reports of irradiated and remelted HXLPE. Furthermore, these data corroborate reports that HXLPE is resilient to cup orientation and demographic variables. Longer term follow-up is recommended.

Optimal position of lipped acetabular liners to improve stability in total hip arthroplasty\u2014an intraoperative in vivo study

BackgroundLipped or elevated acetabular liners are frequently used in total hip arthroplasty to improve stability. However, the optimal position of the lip is not known. The purpose of this study was to determine the optimal position of lipped acetabular liners in total hip arthroplasty performed with a posterior approach.MethodsIn 14 hips, lipped trial liners were placed intraoperatively in various positions around the posterior clock-face of the implanted acetabular shell component. For each liner position, stability of the hip was tested at maximal hip flexion with gradually increasing internal rotation until subluxation occurred, at which point the position of the hip was measured using smartphone accelerometer-based goniometers. Smartphone goniometers were first validated against a computer-assisted navigation system. Post-operative radiographs were analyzed for cup inclination angle, cup anteversion angle, and femoral offset.ResultsMean cup inclination angle in our series was 31° ± 6°. The most common liner position that imparted the greatest stability to posterior subluxation was posteriorly and inferiorly (4 o’clock position for left hip, or 8 o’clock position for right hip). The range for most stable liner position for different patients varied from postero-superior (11 o’clock/1 o’clock position) to directly inferior (6 o’clock position). Comparing a non-lipped liner to a lipped liner placed in the optimal position, the average difference in internal rotation gained before dislocation was 23°. There was no association between cup inclination or anteversion angle with liner position of greatest stability.ConclusionIn hip replacements performed through a posterior approach and with mean cup inclination angle of 31° ± 6°, placing the lip of the elevated liner in the postero-inferior quadrant may impart more stability than in the postero-superior quadrant.

Cross-Linked Polyethylene for Total Hip Arthroplasty: A Model for Evaluation of a Medical Device: Commentary on an article by R. de Steiger, MBBS, FRACS, FAOrthA, et al.: "Cross-Linked Polyethylene for Total Hip Arthroplasty Markedly Reduces Revision Surgery at 16 Years".

Commentary The article by Professor de Steiger and associates describes an important study providing clinical confirmation of the promise of improved survivorship with highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA). The authors report the results of their survivorship analysis comparing 41,171 THAs performed with ultra-high molecular weight conventional polyethylene (CPE) and 199,131 performed with gamma, or electron beam, irradiated XLPE between 1999 and 2016. The 16-year cumulative percentage of revisions was 11.7% (95% confidence interval [CI] = 11.1% to 12.3%) for CPE compared with 6.2% (95% CI = 5.7% to 6.7%) for XLPE. The hazard ratio at 9 years was 3.02. Reduced in vitro wear of XLPE liners had previously been reported with preclinical testing1, but laboratory testing of earlier polyethylene enhancements, such as Hylamer, did not accurately predict clinical performance2. Early clinical experience with XLPE was encouraging as the devices were not identified as outliers in large national registries such as the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Reduced wear of XLPE liners in vivo was reported in radiostereometric analysis (RSA) studies3, resulting in further optimism for this bearing surface. Improved survivorship with XLPE liners was recently reported in a randomized controlled trial (RCT) with a 10-year follow-up that demonstrated a revision rate of 1.9% with Marathon liners compared with 14.6% with Enduron liners4. This was a single-center study of 122 THAs performed with cemented stems and cementless Duraloc cups by 2 experienced surgeons in 1 medical center. The Kaiser Permanente Total Joint Replacement Registry previously reported improved survivorship of XLPE liners compared with CPE liners5. The cumulative incidence of revision was 5.4% of 1,815 THAs with a CPE liner compared with 2.8% of 25,008 with an XLPE liner at 7 years; the hazard ratio for aseptic failure was 1.9. The study by de Steiger et al. utilized cases from the AOANJRR and expanded on this earlier report with longer follow-up, larger sample sizes, and a greater variety of hip implants. The AOANJRR was initiated in 1999, about the time that several highly cross-linked irradiated polyethylene products became commercially available. This timely coincidence allowed for a longitudinal clinical study of a large number of THA cases representing the gradual transition from CPE to XLPE. The registry quickly collected a large volume of cases performed by many surgeons, in many different hospitals, with a variety of implants. However, unlike prospective trials, in which interventions are performed concurrently, there are temporal differences between cohorts in registry analyses. At the beginning of the study period examined by de Steiger et al., most THAs were done with a CPE liner, whereas at the end of the study period most were performed with XLPE. During the 17-year study period, there may have been differences in patient selection, perioperative care protocols, and possibly surgeon experience. Although the authors speculated that any patient selection likely favored the use of XLPE in younger individuals, the opposite may be true because the study samples represented only 74% of the THAs performed for osteoarthritis. Until the AOANJRR formally recalled the ASR (Articular Surface Replacement) in 2009, surgeons may have chosen metal-on-metal or ceramic-on-ceramic bearings—not necessarily XLPE liners—for younger and more active patients. Despite this limitation, the subanalysis performed by de Steiger et al. showed a reduced risk of revision with XLPE cups even in patients under the age of 55 years. The strengths of this observational registry study include data that are generalizable to the “real world,” unlike the findings from an RCT, which may involve limited numbers of patients, few implant types, and limited numbers of surgeons in a single center. In the community, THA procedures are performed by a variety of surgeons with varying skills and specializations. Additionally, in the community, multiple implant combinations are utilized and procedures are performed in a variety of hospital settings. The story of XLPE liners is a good example of how new implants should be introduced and monitored: with careful preclinical testing, rigorous early clinical studies, widespread surveillance, and carefully performed mid-term clinical investigations. The current study is an important, and reassuring, contribution to the orthopaedic literature as XLPE has been widely used throughout the world in millions of patients.

10-Year Follow-Up Wear Analysis of Marathon Highly Cross-Linked Polyethylene in Primary Total Hip Arthroplasty

BackgroundShort-term and intermediate-term wear rates for highly cross-linked polyethylene (HCLPE) liners in total hip arthroplasty (THA) are significantly lower than published rates for traditional polyethylene liners. The aim of this study was to report the longest-to-date follow-up of a specific HCLPE liner. MethodsA series of 35 THAs using a specific HCLPE liner were reviewed. Anteroposterior radiographs were reviewed for femoral head penetration, the presence of femoral and/or acetabular osteolysis, long-term survival, total wear, and wear rates in all patients. ResultsThe average patient age at time of surgery was 70 years with an average follow-up of 10 years (118 months; range, 7.2-13.4 years). The mean wear rate in our cohort was 0.07 mm/y. Total wear was 0.71 mm over the study period. No hips showed evidence of osteolysis in any zones. Survivorship at latest follow-up was 100% with all-cause revision as an end point. ConclusionThe wear rate of HCLPE liners continues to be lower than published wear rates for traditional polyethylene and continues to reaffirm the acceptably low wear rates using HCLPE acetabular liner in primary THA.

CORR Insights(®): oxidized zirconium head on crosslinked polyethylene liner in total hip arthroplasty: a 7- to 12-year in vivo comparative wear study.

Where Are We Now? Hip surgeons and material scientists agree that while reducing bearing-surface wear after THA is important, the real goals are to prevent osteolysis and aseptic loosening. Most hip replacements are performed using highly crosslinked polyethylene (XLPE) liners, since many surgeons are concerned about problems associated with ceramic-on-ceramic and metal-on-metal (MoM) bearings, including squeaking and ceramic fractures for the former [1], and elevated serum ion levels from (MoM) couplings with the latter [6]. However, although a metaanalysis of randomized trials confirmed that XLPE decreased linear and volumetric wear rates [11], it remains unclear whether XLPE actually reduces the likelihood of aseptic loosening after THA [10]. Recommended as an alternative bearing surface, oxidized zirconium was developed to reduce the wear rates of cobalt-chrome heads against polyethylene bearings. The linear wear rate for oxidized zirconium with XLPE liners has been shown to be 4 μm/year [4]. However, in a 5-year followup of a randomized controlled trial, no difference in wear rates was noted between cobalt-chrome and oxidized zirconium heads with XLPE [9]. Crosslinked polyethylene liners seem to make a larger difference in wear than does the head surface against which the polyethylene is placed. Where Do We Need To Go? With the number of primary and revision THAs rising, it is crucial that we produce reliable implants with excellent long-term durability and biocompatability. Further study on the long-term data associated with oxidized zirconium on XLPE bearings is warranted. In their paper, Karidakis and colleagues report lower wear rates of oxidized zirconium heads on XLPE liners when compared to ceramic heads. We need solid long-term data reflecting not only the survival of the implant and the wear rates of bearing surfaces, but also the effects of the wear debris on our patients’ bodies. Because some reports have found that XLPE liners produce wear particles in the submicron range, which can be phagocytosed by human monocytes and so may over longer time periods yet result in osteolysis [12, 14], longer-term studies are needed. The production of rather round shaped submicron wear particles by XLPE liners is a concern that has not been adequately adressed by in vivo studies. Phagocytosed wear particles have the capability to get to the liver, spleen, and other organs [13]. As orthopaedic surgeons, we often rely on radiographs to follow our patients; while perhaps adequate to identify major problems like wear or loosening, I believe we have to do a better job of considering the impact of orthopaedic implants on the whole patient, and not just the hip. We need to learn more about the systemic effects of the arthroplasties we perform. How Do We Get There? To get these answers, we need carefully conducted, long-term clinical followup studies that evaluate THA bearings. Digitized radiographs with computer-aided wear analysis or radiostereometry [5, 10] can provide us with data about the rate of wear at the hip, but as I have suggested here, we need to begin to answer some larger questions about corrosion products and wear debris created by THAs in vivo. Ideally, future investigations will develop methods that can properly identify the fate of these wear particles. Autopsies of patients with THA could provide us with sections of liver, spleen, and other organs. Previous studies [2, 3, 13] have shown mostly metal but also ultrahigh molecular weight polyethylene particle dissemination to those organs. The detected polyethylene particles were in the submicron range. The increased production of such wear particles by XLPE calls for more and larger postmortem studies in order to rule out accumulation of wear debris in parenchymatous and lymphoreticular tissues. Flow cytometry could be a tool to identify monocytes loaded with polyethylene particles in vivo. Laser-scanning microscopy could potentially identify human monocytes containing wear particles. Wear debris from orthopaedic implants is present in lymphoreticular tissue. An increase in wear particle load of human monocytes could reduce the capacity of the immune system. Therefore, we must check the immune system for activity of interleukins, interferone, and tumor necrosis factor, as XLPE wear particles have been shown to induce an increased inflammatory response in vitro [7, 8]. We still have a great deal to learn about the wear particles generated by oxidized zirconium heads on XLPE liners, both at the local and systemic levels.

Effects of extra irradiation on surface and bulk properties of PMPC-grafted cross-linked polyethylene.

Sterilization using high-energy irradiation is an important aspect of implementing an ultra-high molecular weight polyethylene acetabular liner in total hip arthroplasty (THA). In this study, we evaluate the effects of extra irradiations such as gamma-ray or plasma irradiation during sterilization of the poly(2-methacryloyloxyethyl phosphorylcholine [MPC]) (PMPC) surface and cross-linked polyethylene (CLPE) substrate of a PMPC-grafted CLPE acetabular liner. The PMPC-grafted surface yielded high wettability and low friction properties regardless of the extra irradiations as compared with untreated CLPE. During a hip simulator test, wear resistance of the PMPC-grafted CLPE liner was maintained after extra irradiation, which is due to the high wettability characteristics of the PMPC surface. In particular, the PMPC-grafted CLPE liner treated with plasma irradiation showed greater wettability and wear resistance than that with gamma-ray irradiation. However, we could not clearly observe the changes in chemical properties and morphology of the PMPC surface after both extra irradiations. The physical and mechanical properties attributed to CLPE substrate performance were also unchanged. In contrast, PMPC-grafted CLPE treated with plasma irradiation showed improved oxidation resistance as compared to that treated with gamma-ray irradiation after accelerated aging. Thus, we conclude that PMPC-grafted CLPE with plasma irradiation has promise as a lifelong solution for bearing in THA.

A Novel Technique for Identification of Fractured Ceramic Acetabular Liner in Total Hip Arthroplasty: A Case Report

In total hip arthroplasty ceramic bearings are liable to fracture. We present the case of an 82-year-old male with groin pain and an audible squeak 6 months post ceramic on ceramic hip arthroplasty. Initial plain radiography and examination under anaesthetic (EUA) were normal. Fluoroscopy with normal image exposure was also unremarkable. Over penetration of the image intensifier film demonstrated a fracture of the ceramic acetabular liner. The patient subsequently underwent a revision of both acetabular and femoral bearing surfaces.Displaced ceramic liner fractures are easy to identify with plain radiographs. We recommend the use of over penetration using image intensification as a technique to help identify subtle ceramic liner fractures. To our knowledge this has not been previously reported in the literature.

Multidirectional wear and impact-to-wear tests of phospholipid-polymer-grafted and vitamin E-blended crosslinked polyethylene: a pilot study.

Modifying the surface and substrate of a crosslinked polyethylene (CLPE) liner may be beneficial for high wear resistance as well as high oxidative stability and excellent mechanical properties, which would be useful in contributing to the long-term performance of orthopaedic bearings. A grafted poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer on a vitamin E-blended crosslinked PE (HD-CLPE[VE]) surface may provide hydrophilicity and lubricity without compromising the oxidative stability or mechanical properties. (1) Will the modifications (PMPC grafting and vitamin E blending) affect the lubrication characteristics of the CLPE surface? (2) Will the modifications affect wear resistance? (3) Will the modifications affect fatigue resistance? We investigated the effects of surface and substrate modifications (PMPC grafting and vitamin E blending) on the wear and fatigue fracture of thin CLPE samples. For each of the untreated and PMPC-grafted CLPE surfaces with and without vitamin E blended (four groups), wettability and lubricity surface analyses were conducted as well as multidirectional wear and impact-to-wear tests using a pin-on-disk testing machine. The water wettability and lubricity (CLPE [mean ± 95% confidence interval]: 23.2° ± 1.8°, 0.005 ± 0.001; HD-CLPE[VE]: 26.0° ± 2.3°, 0.009 ± 0.003) of the PMPC-grafted surfaces were greater (p < 0.001) than that (CLPE: 90.3° ± 1.2°, 0.067 ± 0.015; HD-CLPE[VE]: 90.8° ± 2.0°, 0.063 ± 0.008) of the untreated surface regardless of vitamin E additives. It was observed that the PMPC grafting (CLPE: 0.23 ± 0.06 mg; HD-CLPE[VE]: 0.05 ± 0.10 mg) was associated with reduced gravimetric wear (CLPE: 0.53 ± 0.08 mg, p = 0.004 HD-CLPE[VE]: 0.23 ± 0.07 mg, p = 0.038) in the multidirectional wear test. The PMPC-grafted surface characteristics did not appear to affect the impact fatigue resistance regardless of vitamin E blending. PMPC grafting improved the surface hydrophilicity and lubricity, and it reduced the gravimetric wear in terms of multidirectional sliding. It did not result in differences in terms of the impact-to-unidirectional sliding regardless of vitamin E blending. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo. Our preliminary in vitro findings suggest that some improvement in the wear performance of crosslinked polyethylene acetabular liners in total hip arthroplasty could be obtained using PMPC grafting. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo.

A multicenter approach evaluating the impact of vitamin e-blended polyethylene in cementless total hip replacement.

Since polyethylene is one of the most frequently used biomaterials as a liner in total hip arthroplasty, strong efforts have been made to improve design and material properties over the last 50 years. Antioxidants seems to be a promising alternative to further increase durability and reduce polyethylene wear in long term. As of yet, only in vitro results are available. While they are promising, there is yet no clinical evidence that the new material shows these advantages in vivo. To answer the question if vitamin-E enhanced ultra-high molecular weight polyethylene (UHMWPE) is able to improve long-term survivorship of cementless total hip arthroplasty we initiated a randomized long-term multicenter trial. Designed as a superiority study, the oxidation index assessed in retrieval analyses of explanted liners was chosen as primary parameter. Radiographic results (wear rate, osteolysis, radiolucency) and functional outcome (Harris Hip Scores, University of California-Los Angeles, Hip Disability and Osteoarthritis Outcome Score, Visual Analogue Scale) will serve as secondary parameters. Patients with the indication for a cementless total hip arthroplasty will be asked to participate in the study and will be randomized to either receive a standard hip replacement with a highly cross-linked UHMWPE-X liner or a highly cross-linked vitamin-E supplemented UHMWPE-XE liner. The follow-up will be 15 years, with evaluation after 5, 10 and 15 years. The controlled randomized study has been designed to determine if Vitamin-E supplemented highly cross-linked polyethylene liners are superior to standard XLPE liners in cementless total hip arthroplasty. While several studies have been started to evaluate the influence of vitamin-E, most of them evaluate wear rates and functional results. The approach used for this multicenter study, to analyze the oxidation status of retrieved implants, should make it possible to directly evaluate the ageing process and development of the implant material itself over a time period of 15 years.

Body mass index as a risk factor for mis-seating of ceramic liners in total hip arthroplasty

Background A retrospective radiographic review was undertaken to determine the prevalence of mis-seated ceramic liners in primary total hip arthroplasty and the association between body mass index and mis-seating risk. Methods Patients with primary implantation of the Trident (Stryker, Mahwah, NJ) uncemented ceramic acetabular component were identified from a prospective database of 2227 primary total hip arthroplasties and radiographically reviewed. All procedures were performed at one center between 1999–2006. The mis-seating angle and location were determined. The risk of mis-seating by body mass index was calculated using logistic regression models. Results A total of 411 primary total hip arthroplasties were identified. Mis-seating occurred in 81 patients (19.7%). Of the 411 total hip arthroplasties, 83 (20.2%) were performed in patients with a body mass index of less than 25.0 defined as underweight to normal, 133 (32.4%) in patients who were overweight with a body mass index between 25.0–29.9, and 195 (47.4%) in patients who were obese with a body mass index of over 30.0. Adjustment for case mix revealed a significant association between body mass index and risk of mis-seating of ceramic components. Patients who were overweight at the time of total hip arthroplasty (body mass index 25.0–29.9) were at increased risk of mis-seating (adjusted odds ratio 2.52, 95% confidence interval (1.24-5.12, P=0.01). Conclusions Mis-seating of ceramic acetabular systems in total hip arthroplasty was a frequent occurrence. Patients who were overweight were more than two times more likely to suffer mis-seating than those who were underweight, of normal weight, or obese.

The Ringloc liner compared with the Hexloc liner in total hip arthroplasty

The aim of this study was to compare the 10-year survival rate, pelvic osteolysis frequency and linear head penetration rate of the Hexloc and Ringloc liners used together with a partially threaded porous and hydroxyapatite coated cup and the Bi-Metric uncemented femoral stem. The 15-year results for the cup with the Hexloc liner are also reported. We included 332 consecutive hips (166 Hexloc and 166 Ringloc) on 281 patients in the study. Revisions of prosthesis components were recorded and pelvic osteolytic lesions were assessed using radiographs and computed tomography. The linear head penetration rate was measured using the Martell method. The 10-year survival rate of the liner with revision due to liner wear and/or osteolysis as endpoint was 88% for the Hexloc liner and 98% for the Ringloc liner. The 15-year survival rate of the Hexloc liner was 67%. Pelvic osteolysis was found in 27% of the Hexloc and 19% of the Ringloc hips. After 15 years, 53% of the Hexloc hips had developed an osteolytic lesion. The linear head penetration rate was 0.16 mm/year for the Hexloc liner and 0.12 mm/year for the Ringloc liner. This paper is the first to describe the rapidly deteriorating survival up to 15 years with the old generation gamma-in-air sterilized polyethylene used in Hexloc liners. The newer Ringloc liner with the ArCom™ polyethylene has superior clinical results but a linear wear rate and frequency of osteolytic lesions that is higher than expected.

Wear Rate of Highly Cross-Linked Polyethylene in Total Hip Arthroplasty

Highly cross-linked polyethylene was introduced for clinical use in total hip arthroplasty with the expectation that it would exhibit less wear when compared with conventional polyethylene. The purpose of this study was to report the clinical and radiographic results, after a minimum of five years of follow-up, of a randomized, blinded, controlled trial comparing a conventional polyethylene with a first-generation highly cross-linked polyethylene. One hundred patients were enrolled in a prospective, randomized controlled study comparing highly cross-linked and conventional polyethylene acetabular liners in total hip arthroplasty. Fifty patients were in each group. At the time of follow-up, clinical outcomes were assessed and steady-state femoral head penetration rates (after bedding-in) for each patient were calculated with use of a validated radiographic technique. In addition, a statistical comparison of polyethylene wear between groups was performed with use of generalized estimating equations. At a mean of 6.8 years postoperatively, there were no differences between the two polyethylene groups with regard to the Harris hip score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), or Short Form-12 (SF-12) score. The mean femoral head penetration rate in the first through fifth years was found to be significantly lower in the group treated with the highly cross-linked polyethylene (0.003 mm/yr [95% confidence interval, +/-0.027]) than it was in the group treated with conventional polyethylene (0.051 mm/yr [95% confidence interval, +/-0.022]) (p=0.006). Men treated with a conventional polyethylene liner had a significantly higher (p<or=0.012) femoral head penetration rate (0.081 mm/yr [95% confidence interval, +/-0.065]) than both men and women with a highly cross-linked liner (-0.013 mm/yr [95% confidence interval, +/-0.074] and 0.009 mm/yr [95% confidence interval, +/-0.028], respectively). The general estimating equations demonstrated that the group with a highly cross-linked polyethylene liner had a significantly lower femoral head penetration rate than the group with a conventional polyethylene liner (p=0.025), and a significantly higher femoral head penetration rate was demonstrated in men with a conventional polyethylene liner when compared with both men and women with a highly cross-linked liner (p=0.003). At a minimum of five years postoperatively, the steady-state femoral head penetration rate associated with this first-generation highly cross-linked polyethylene liner was significantly lower than that associated with a conventional polyethylene liner. Long-term follow-up is required to demonstrate the clinical benefit of this new material.

Use of Constrained Acetabular Liners in Total Hip Arthroplasty

The use of constrained acetabular liners is indicated when soft-tissue tensioning techniques such as femoral neck lengthening, component repositioning, and use of lateralized acetabular liner are ineffective. It is most commonly used as a salvage procedure in revision situations. However, a locking acetabular insert may be used for primary THAs in patients with joint or soft-tissue laxity, neuromuscular disease, or intraoperative instability. In addition to the described commercially available liners, several manufacturers will provide customized components on request.

The role of constrained liners in total hip arthroplasty.

Recurrent instability after total hip replacement is a complex problem with extensive literature detailing multiple etiologies and solutions. It has been shown that the success of surgical treatment depends on the identification of the cause. Unfortunately, in certain situations, there may not be an optimal solution for dealing with the cause, or the cause may remain unidentified. In these cases, the success rate of surgical treatment of the unstable total hip replacement is only 40% to 50%. Constrained acetabular liners were developed to address the problem of recurrent instability by holding the femoral head captive within the socket. Before the use of constrained liners, there were no reliable solutions to dislocation arising from inadequate soft tissues, a deficient abductor mechanism, or neuromuscular disorders. We have used a constrained liner for these situations, with poor patient compliance and instability without a clear cause as relative indications for its use. Our experience with attaining joint stability using one type of constrained liner has resulted in a 97.6% success rate (83 of 85 hips) at 4.8 years, surpassing the outcomes achieved by other means. The intermediate followup after implantation of a constrained liner has not shown significant rates of component wear or loosening.

Failure Mode of Polyethylene Liner in Total Hip Arthroplasty with Harris-Galante II Acetabular Cup

Purpose: To assess the mode of a polyethylene liner failure in total hip replacement using a Harris-Galante II acetabular component. Materials and Methods: A retrospective review was performed and 128 consecutive primary total hip arthroplasties were analyzed in 111 patients who had a second-generation Harris-Galante cup. All patients were followed up for a minimum of five years, with a mean follow up of 7.4 years (range, 5 to 12.9 years). A total of 26 cups (20.2%) were revised at the time of the latest follow up. The medical records, radiographs, surgical notes, and retrieved components were analyzed in order to determine the precise causes of the revision. Results: Twenty-two cases (17.3%) were found to have experienced problems with the polyethylene liner. Three types of liner failure were identified; metallosis associated with polyethylene liner wear (14 cases), excessive wear without metallosis necessitating a revision (6 cases), and polyethylene liner dissociation without gross evidence of wear (2 cases). Conclusion: This study find that polyethylene liner failure is the main cause of the revision of this component. Early surgical intervention needs to be performed before fatal metal damage occurs in order to avoid metallosis, and severe bone stock damage in cases of excessive polyethylene wear.

A Comparative Study of the in vivo Wear of Zirconia and Metal Heads Articulating with Polyethylene Liners in Total Hip Arthroplasty

Purpose: The purposes of this paper was to determine the wear rates and volumetric wears of ceramic (Zirconia) and metal (Cobalt-chrome) femoral heads, and to differentiate creep from true wear. Another purpose was to determine the extent of wear and volumetric wear per annum. Materials and Methods: We examined 86 patients (111 hips) who were continuously followed up from 180 patients (225 hips) who received THRA with AVN of stage III or above at our hospital. Patients were followed until December 1999 for more than a minimum of 3 years from June for 1996. The hip joint AP radiographs that had been taken immediately after the operations, six weeks postoperatively and annually thereafter were compared. We used the computer assisted vector wear analysis program of Martell to measure the wear rate, volumetric wear and vector wear. Results: The wear rate and the volumetric wear in the zirconia ceramic head group (1.443 mm/year, 665.433 /year) and metal head group (2.161 mm/year, 1271.831 /year) were high immediately after operation and six weeks postoperatively, and this was significantly more than during all for other periods, giving a wear rate and volumetric wear in the ceramic head group of 0.180 mm/year and 81.101 /year, and in the metal head group of 0.219 mm/year and 124.149 /year. Moreover, the average wear rates and volumetric wear rates of these two groups were significantly different, and annual wear and volumetric wears showed a trend to decrease with time. Conclusion: Wear rate and volumetric wear six weeks after operation were remarkably high compared with the other periods. This is interpreted as the result of a creep phenomenon, which occurred mainly during the six weeks following the operation. The Zirconia ceramic head group showed little wear, which confirms the theoretical advantage of the zirconia ceramic head in vivo.

Independent contribution of elevated-rim acetabular liner and femoral head size to the stability of total hip implants

The use of an elevated-rim acetabular liner in total hip arthroplasty is widely accepted. We sought to determine quantitatively the amount of additional stability provided by the elevated-rim liner compared with the standard nonelevated liner. The stability of the hip with a 32-mm femoral head was compared with the standard 28-mm head. Our results show that a 15° elevated-rim acetabular liner placed in the posterior quadrant increased hip stability by an additional 8.9° of internal rotation. Similarly the 32-mm head provided 8.1° of additional internal rotation. The increases were statistically significant (P<.0001). We did not encounter increased anterior dislocation intraoperatively. The findings of this study indicate that the 32-mm head may contribute to hip stability in primary total hip arthroplasty, and in instances in which a posterior approach is used, an elevated-rim liner placed in the posterior quadrant may contribute independently to hip stability.

Abdominal cyst after early failure of polyethylene liner in total hip arthroplasty

We report a case in which the early failure of a polyethylene liner, coupled with a 32-mm CrCo ball head, caused pelvic cyst formation simulating an abdominal mass. The presence of the mass with inguinal swelling lead us to diagnosis liner failure, as shown by radiography. An extraperitoneal cyst surrounding the iliopsoas muscle from the lesser trochanter up to the lumbosacral junction was demonstrated with pre-operative computed tomography and sonography. The cyst contained fluid and many large particles of polyethylene debris. The liner and the head were substituted and the cyst was removed through a different abdominal approach. We hypothesize that debris falls out and concentrates along the iliopsoas muscle from the very beginning of wear, and then the muscle concentration forces pumped it along the muscle belly. From the histologic point of view, large polyethylene particles were observed in the removed tissue, and no major osteoclastic activation was found.