The benefits of HXLPE in total knee arthroplasty (TKA) have not been as evident as total hip arthroplasty (THA). A systematic review and meta-analysis to assess the impact of highly-crosslinked polyethylene (HXLPE) on TKA outcomes compared to conventional polyethylene (CPE) is described. All studies comparing HXLPE with CPE for primary TKA were included for analysis. The minimum dataset included revision rates, indication for revision, aseptic component loosening and follow-up time. The primary outcome variables were all-cause revision, aseptic revision, revision for loosening, radiographic component loosening, osteolysis and incidence of radiolucent lines. Secondary outcome measures included postoperative functional knee scores. A random-effects meta-analysis allowing for all missing data was performed for all primary outcome variables. Six studies met the inclusion criteria. In total, there were 2,234 knees (1,105 HXLPE and 1,129 CPE). The combined mean follow-up for all studies was 6 years. The aseptic revision rate in the HXLPE group was 1.02% compared to 1.97% in the CPE group. There was no difference in the rate of all-cause revision (p = 0.131), aseptic revision (p = 0.298) or revision for component loosening (p = 0.206) between the two groups. Radiographic loosening (p = 0.200), radiolucent lines (p = 0.123) and osteolysis (p = 0.604) was similar between both groups. Functional outcomes were similar between groups. The use of HXLPE in TKA yields similar results for clinical and radiographic outcomes when compared to CPE at midterm follow-up. HXLPE does not confer the same advantages to TKA as seen in THA

Introduction. Highly cross-linked (HXL) polyethylene has demonstrated clinical advantages as a wear resistant acetabular bearing material in total hip arthroplasty (THA) [1]. In vitro wear testing has predicted a tenfold reduction in the wear rate of HXL polyethylene, as compared to its conventional, non-HXL counterpart [2]. To date, radiographic studies of head penetration represent the state-of-the-art in determining clinical wear of polyethylene hip liners [3]. However, as the amount of wear drops to very low levels, it becomes important to develop a precise and reliable method for measuring wear, facilitating a comparison of clinical results to expectations. This study focuses on locating and quantifying the maximum linear wear of retrieved acetabular poly liners using a coordinate measuring machine (CMM). Specifically, HXL liners are compared to a baseline of conventional, non-HXL bearings. Methods. An IRB-approved retrieval laboratory received 63 HXL acetabular bearing retrievals from 5 manufacturers with in vivo durations of 1.01–14.85 years. These were compared with 32 conventional, non-HXL controls (including gas plasma, gamma-barrier and EtO) from 3 manufacturers with in vivo durations of 1.03–20.89 years. Liners were mounted in a tripod of axial contacts with the liner face positioned in a vertical plane. Each bearing was scanned with a CMM dual-probe head, with one horizontal probe scanning the articular surface and the other scanning the non-articular, sequentially. Surface-normal wall thickness values along each latitude were calculated using a custom developed algorithm (Figure 1). Because the liners are axially symmetric as manufactured, deviation in wall thickness at a given latitude represents linear wear [4]. Results. Total wear penetration for the HXL liners ranged from 0.02 to 1.03 mm, and for the conventional, non-HXL controls ranged from 0.07 to 6.85 mm. The HXL liners had an average linear wear rate of 0.02 mm/year, compared to 0.20 mm/year for the conventional, non-HXL controls (Figure 2). The direction of maximum wear, as measured in degrees from the cup pole, ranged from 8.32 to 73.86 degrees. Differences in wear rates as a function of crosslinking dose, as well as presence/absence of a lip can be identified. Discussion. This wear measurement study of retrievals is the first application of a novel CMM technique to locate and quantify wear in HXL liners compared to conventional polyethylene controls. The study confirms the expectations of a tenfold reduction in wear rates that were based on in vitro testing [2]. The results are consistent with those of radiographic studies that have documented lower wear of HXL polyethylene in the hip compared to conventional polyethylene [3]. However, the current technique offers higher precision and reliability, and eliminates the large proportion of negative wear measurements common amongst radiographic methods. A sufficient number of liners have been measured to begin to differentiate wear between different radiation doses

Introduction:. Although commonly used, the clinical performance of highly crosslinked polyethylene in total knee arthroplasty (TKA) remains unknown and concerns exist regarding fatigue resistance and oxidation, particularly in posterior-stabilized (PS) designs. The purpose of this study is to compare highly crosslinked and conventional polyethylene in a PS TKA design at a minimum of 5-years. Methods:. A prospective cohort study of 114 consecutive TKAs in 83 patients was performed as a subset of a multi-center prospective study. All TKAs utilized an identical PS design. Conventional polyethylene inserts were used in 50 knees and second-generation highly cross-linked polythethylene inserts were implanted in 64 TKAs. All patients were followed with clinical outcome measures (Short-Form 36, Knee Society Scores, WOMAC and LEAS) and radiographically for a minimum of 5 years. Results:. The mean age of the highly cross-linked polyethylene group was 4 years less than the conventional group (p = 0.03). There was no difference in BMI (p = 0.3) or preoperative outcome measures between groups with numbers available. Seven patients died or were lost to follow up and one underwent revision for infection at 3 months postoperatively. 103 TKAs obtained minimum 5-year follow up. Mean Knee Society Scores were 12 points higher (p = 0.01) and 14 points higher (p = 0.005) in the physical function subset of the SF-36 in the highly cross-liked polyethylene group. There was no difference in the other outcome measures with the numbers available. There was no radiographic osteolysis or mechanical failures related to the tibial polyethylene in either group. Conclusion:. Mechanical failure or radiographic osteolysis was not observed with either conventional or highly cross-linked polyethylene in this PS TKA design at mid-term follow up. To our knowledge, this is the first minimum 5-year follow-up of highly cross-linked polyethylene in a posterior-stabilized design. While the results support comparative safety, longer-term follow-up is warranted to determine if wear resistance and mechanical properties of highly crosslinked polyethylene are maintained. Significance: Concerns regarding early fatigue failure and mechanical complications related to the PS post-cam articulation of highly-crosslinked polyethylene in TKR were not substantiated at a minimum of 5 years clinical followup in this prospective cohort study. Highly cross-linked polyethylene demonstrated clinical equivalency compared to conventional polyethylene, even when used in a younger and presumably more active patient group

Purpose. Cross-linking of polyethylene greatly reduces its wear rate in hip simulator studies. We conducted a systematic review and meta-analysis of randomized controlled trials comparing cross-linked to conventional polyethylene liners for total hip arthroplasty to determine if there is a clinical reduction of: 1) wear rates, 2) radiographic osteolysis, and 3) need for total hip revision. Method. A systematic search of MEDLINE, EMBASE, and COCHRANE databases was conducted from inception to May 2010 for all trials involving the use of cross-linked polyethylene for total hip arthroplasty. Eligibility for inclusion in the review was: use of a random allocation of treatments; a treatment arm receiving cross-linked polyethylene and a treatment arm receiving conventional polyethylene for total hip arthroplasty; and use of radiographic wear as an outcome measure. Eligible studies were obtained and read in full by two co-authors who then independently applied the Checklist to Evaluate a Report of a Nonpharmacological Trial to each study. Pooled mean differences were calculated for the following continuous outcomes: bedding-in, linear wear rate, three dimensional linear wear rate, volumetric wear rate, and total linear wear. Pooled risk ratios were calculated for radiographic osteolysis and revision hip arthroplasty. Results. The literature search strategy identified 194 potential studies of which 12 met inclusion criteria. All studies reported a significant reduction in radiographic wear with cross-linked polyethylene. Pooled mean differences for linear wear rate, three dimensional linear wear rate, volumetric wear rate, and total linear wear were all significantly reduced for cross-linked polyethylene. The risk ratio for radiographic osteolysis was 0.40 (95% C.I. of 0.27 to 0.58; p<0.01; I2=0%), favoring cross-linked polyethylene. There were no significant differences in need for revision total hip arthroplasty or amount of bedding-in. Conclusion. Cross-linked polyethylene liners demonstrate reduced radiographic wear and osteolysis up to 8 years after implantation. Follow up is not long enough to show a difference in need for revision total hip arthroplasty. Cross-linked polyethylene should be considered for young patients undergoing total hip arthroplasty

Introduction. Ceramic femoral heads have proven to be more scratch resistant with better wettability and improved wear characteristics compared to metal heads in the laboratory setting. The objective of this study was to compare long-term survivorship and in vivo wear rates of ceramic and metal femoral heads against conventional polyethylene articulation in young patients. Materials and Methods. Thirty-one matched pair of alumina and metal femoral heads against conventional polyethylene in young patients (≤ 65 years) were analyzed for wear and failures for mechanical reasons. The match was based on gender and age at the time of surgery. All procedures were performed between June 1989 and May 1992 by a single surgeon via posterolateral approach, using non-cemented RB (Ranawat-Bernstein) stems, HG II (Harris-Galante) cups, 4150 conventional polyethylene and 28mm femoral heads. Hospital for Special Surgery (HSS) hip score was used for clinical analysis. Wear measurements were performed between the initial anteroposterior standing pelvis radiographs, at a minimum of one year after the index procedure to eliminate the effect of bedding-in period, and the latest follow-up. Two independent observers analyzed polyethylene wear rates using the computer-assisted Roman 1.70 software. In revision cases, the wear rates were calculated from radiographs prior to revision surgery. A pair student t test was performed to analyze the statistical difference. Two-tailed ρ values less than 0.05 were considered statistically significant. Results. The mean age was 54.5 ± 8.5 at the time of surgery (range 23.3–65). Average clinical and radiographic follow-up were 17 ± 2.1 (range 12.8–20) and 14.1 ± 2.6 years (range 10–19.1) respectively. The mean HSS score in ceramic and metal groups were 30.4 ± 8 (range 24–56) and 36.6 ± 4.7 (range 20–40) respectively. The mean wear rate for the ceramic group and the metal group were 0.086 ± 0.046 mm/year and 0.137 ± 0.052 mm/year, respectively which was statistically significant (p < 0.001). There were no revisions in the ceramic group for osteolysis or loosening, however one patient required a strut graft for femoral osteolysis that was distal to the tip of the implant due to non-circumferential porous coating of the stem. There were 3 cup revisions in the metal group, all for acetabular osteolysis, and no stem lysis or loosening. The Kaplan-Meier survivorship for revision for mechanical failure in the ceramic and metal group was 100% and 90.3% respectively. Discussion. The low mean wear rate of ceramic compared to metal in this study is consistent with previously published laboratory reports. There was no revision for loosening or osteolysis in the ceramic group, with 100% survivorship for revision due to mechanical failures, which demonstrates superior durability of this material compared to metal femoral heads. The strength of this study is that this the first long-term report comparing ceramic and metal femoral heads against conventional polyethylene using a matched pair analysis in young patients

Purpose. The objective of this study was to compare the wear characteristics and damage scores in highly crosslinked (XLPE) and conventional polyethylene (CPE) acetabular liners. Methods. This was a retrieval analysis of 13 XLPE liners obtained from patients who underwent revision surgery from 1999 to 2011. These patients were matched on patient demographics (age, BMI, side, sex, and length of implantation) and implant characteristics (inner diameter, outer diameter, and lip angle) to another group with CPE who underwent revision in the same time period. The only difference between implants was the use of XLPE. Wear analysis was performed with micro-computed tomography (micro-CT), provided thickness measurements across four quadrants of the bearing surface. Surface damage was scored and the pattern documented. The mean duration of implantation was 5.00 ± 3.36 years in the XLPE group and 5.19 ± 3.69 years in the CPE group (p = 0.12), with the longest duration exceeding 10 years. Results. CPE demonstrated more wear at time of retrieval with a mean thickness of 8.18 ± 1.50 mm compared to XLPE with a mean thickness of 8.91 ± 1.76 mm (p < 0.001). Damage scoring was not significantly different between the two groups, with a total damage score of 13.77 ± 3.95 in XLPE and 15.23 ± 4.63 in CPE (p = 0.18). There was no difference in the distribution of wear and damage. Conclusion. XLPE undergoes less wear than CPE, however this may not be apparent by using damage scoring alone, which is the most common retrieval analysis technique. The superior wear properties of XLPE may reduce the need for revision surgery as a result of decreased wear and osteolysis

Introduction. Total knee replacement (TKR) implant designs and materials have been shown to have a significant impact on tibial insert wear. A medial-pivot (MP) design theoretically should generate less wear due to a large contact area in the medial compartment and lower contact stresses. Synovial fluid aspiration studies have confirmed that a first generation MP TKR system (ADVANCE®, MicroPort Orthopedics Inc., Arlington, TN, USA) generates less wear debris than is seen with other implant designs articulating against conventional polyethylene (CP). Objectives. The objective of this study was to evaluate the in vitro wear rate of a second generation MP TKR system (EVOLUTION® Cruciate-Sacrificing, MicroPort Orthopedics Inc., Arlington, TN, USA) using CP tibial inserts and compare to previously published values for other TKR designs with CP and first or second generation crosslinked polyethylene (XLPE) tibial inserts. Methods. In vitro wear was assessed for five MP CP tibial inserts, each loaded for 5 megacycles (Mc) of simulated gait in accordance with ISO 14243–3. Insert cleaning and wear measurements were performed every 0.5 Mc in accordance with ISO 14243–2. Manufacturer websites and the MEDLINE database were searched for previously published in vitro wear rates for other TKR designs used in combination with CP and first or second generation XLPE inserts. Second generation XLPE inserts are those with additives or additional manufacturing, such as sequentially annealed and irradiated XLPE (X3®, Stryker, Mahwah, NJ, USA) and vitamin E infused polyethylene (E1®, Biomet, Warsaw, IN, USA). All TKR designs utilized cobalt-chrome (CoCr) femoral components, except Legion-Verilast that included Oxinium™ femoral components (Smith & Nephew, Memphis, TN, USA). Results. The mean wear rate for the MP system (2.0+0.2 mg/Mc) was less than half the wear rates reported for other TKR designs using CP inserts (Figure 1). The wear was also reduced or similar to those reported for all but three designs used in combination with XLPE inserts (Figure 2). Interestingly, wear rates for the MP system were approximately one-third of those reported for E1 and X3 used in combination with the Scorpio and Triathlon CR TKR systems (Stryker, Mahwah, NJ, USA). The main limitation to the current study is the use of literature comparators. While the comparison studies were all conducted using similar methods on knee wear simulator machines, there were some experimental differences that could potentially impact wear rates (e.g. diluted vs. non-diluted serum, gait patterns, types of testing machines). Conclusions. In vitro wear for a second generation MP TKR system was similar or lower than what has been previously reported for other TKR systems used with CP or XLPE tibial inserts. These results suggest that implant design may play a larger role in TKR wear debris generation than the material used for the tibial insert

We report the outcome of 320 primary Total Hip Arthroplasties (THA) with minimum 10-year follow-up (range 10–17 years, mean 12.6 years), performed by a single surgeon in Tauranga New Zealand, with the Exeter Contemporary Flanged all-polyethylene cup and Exeter femoral stem via a posterior approach. The aim of the study is to compare the results with the published results from the design centre and create a baseline cohort for further outcomes research in this centre.

All patients were prospectively followed at 6 weeks, 1 year, 5 years, 10 years, (and 15 years when available). Of 333 cases that matched the inclusion criteria, 13 procedures in 12 patents were excluded because of concomitant bone grafting and/or supplementary cage fixation, leaving 320 primary THA procedures in 280 patients, including 26 bilateral procedures in 13 patients.

Mean follow-up of the surviving cases was 12.6 (range 5.0-17.1) years. There were 12 revisions – 2 for fracture, 5 for instability, 1 for impingement pain and 4 for infection. There were no revisions for aseptic cup loosening. Kaplan-Meier survivorship with revision for aseptic loosening as the endpoint was 100% at 15.0 years (with minimum 40 cases remaining at risk). All-cause acetabular revision in 12 cases result in a Kaplan-Meier survival of 95.9% (95% CI: 93.5 to 98.3%).

Cemented THA with the Exeter Contemporary Flanged cup and the Exeter stem is a durable combination with results that can be replicated outside of the design centre. The Exeter Contemporary Flanged cup has excellent survivorship at 15 years when used with the Exeter stem. Cemented THA with well-proven components should be considered the benchmark against which newer designs and materials should be compared.

The 2021 Australian Orthopaedic Association National Joint Replacement Registry report indicated that total shoulder replacement using both mid head (TMH) length humeral components and reverse arthroplasty (RTSA) had a lower revision rate than stemmed humeral components in anatomical total shoulder arthroplasty (aTSA) - for all prosthesis types and diagnoses. The aim of this study was to assess the impact of component variables in the various primary total arthroplasty alternatives for osteoarthritis in the shoulder. Data from a large national arthroplasty registry were analysed for the period April 2004 to December 2020. The study population included all primary aTSA, RTSA, and TMH shoulder arthroplasty procedures undertaken for osteoarthritis (OA) using either cross-linked polyethylene (XLPE) or non-cross-linked polyethylene (non XLPE). Due to the previously documented and reported higher revision rate compared to other anatomical total shoulder replacement options, those using a cementless metal backed glenoid components were excluded. The rate of revision was determined by Kaplan-Meir estimates, with comparisons by Cox proportional hazard models. Reasons for revision were also assessed. For a primary diagnosis of OA, aTSA with a cemented XLPE glenoid component had the lowest revision rate with a 12-year cumulative revision rate of 4.7%, compared to aTSA with cemented non-XLPE glenoid component of 8.7%, and RTSA of 6.8%. The revision rate for TMH was lower than aTSA with cemented non-XLPE, but was similar to the other implants at the same length of follow-up. The reason for revision for cemented aTSR was most commonly component loosening, not rotator cuff deficiency. Long stem humeral components matched with XLPE in aTSA achieve a lower revision rate compared to shorter stems, long stems with conventional polyethylene, and RTSA when used to treat shoulder OA. In all these cohorts, loosening, not rotator cuff failure was the most common diagnosis for revision

Contemporary polyethylene liners for total hip replacements were introduced in the late 1990's to address osteolysis associated with wear of conventional polyethylene. Every major device manufacturer introduced an “enhanced polyethylene”. In the ensuing decade plus, every major arthroplasty meeting had presentations and debates about the wear resistance and mechanical properties of these new polymers. The results have been remarkable and now with 17 to 18 years of use in patients, we have yet to see clinically significant osteolysis in our patients regardless age or activity level. The results can be summarised as follows: All currently commercially available highly crosslinked polyethylenes produced by major device companies have demonstrated a reduction in wear and osteolysis. At the 2016 Closed Meeting of The Hip Society, none of the surgeons attending had seen a clinically significant case of osteolysis associated with highly crosslinked polyethylene. Registry data demonstrates the superiority of the highly crosslinked materials over conventional polyethylenes. Historical concerns over a reduction in mechanical properties have not been borne out in clinical studies. Although highly crosslinked polyethylene liner fractures have been reported, they are rare and probably related to specific designs or surgical technique issues. It is important to remember that there were rare cases of fracture of conventional polyethylene as well. With currently reported wear rates of the enhanced polyethylenes, polyethylene thickness is unlikely to be a factor in long-term durability with well-designed sockets. Bench data has demonstrated that polyethylene thickness is not a risk factor for wear or fracture if well supported by the metal shell. Thin unsupported polyethylene is at risk for fracture. Although the new anti-oxidant polyethylenes (eg. Vitamin E) have performed well in wear studies, there is no clinically available evidence to support their use based on enhanced fracture toughness

Isolated liner and head exchange procedure has been an established treatment method for polyethylene wear and osteolysis when the acetabular component remains well-fixed. In this study, its mid-term results were evaluated retrospectively in 34 hips. Among the consecutive patients operated upon from September 1995, 2 patients (3 hips) were excluded because of inadequate follow-up and the results of remaining 34 hips of 34 patients were evaluated. They were 20 men and 14 women with a mean age of 49 years at the time of index surgery. Conventional polyethylene liner was used in 26 cases and highly cross-linked polyethylene liner was used in 8 cases. In 3 cases, liner was cemented in the metal shell because compatible liner could not be used. After a minimum follow-up of 5 years (range, 5∼20.2), re-revision surgery was necessary in 10 cases (29.4%); 8 for wear and osteolysis, 2 for acetabular loosening. In all re-revision cases, conventional polyethylene was used. There was no failure in the cases in which highly cross-linked polyethylene was used. There was no case complicated with dislocation. The results of this study suggest more promising results with the use of highly cross-linked polyethylene in isolated liner exchange

INTRODUCTION. Since the early 2000s, highly cross-linked (HXL) UHMWPE's have become a popular option with multiple experimental and clinical studies showing that gamma or electron radiation doses between 50–100kGY reduce wear and potentially extend the bearing life of UHMWPE. However, the increased wear resistance came at a compromise to mechanical properties due to the cross-linking process. Vitamin E has been added to some HXL UHMWPE materials to offer a solution to the compromise by increasing oxidation resistance and maintaining sufficient fatigue strength. However, limited data is available on the effect of the fabrication process, especially the method of irradiation, on the properties of the Vitamin E blended HXL UHMWPE. The purpose of this study was to evaluate the effects of adding the antioxidant vitamin E to highly crosslinked UHMWPE on wear rates. METHODS. Wear testing was performed on six highly crosslinked UHMWPE acetabular liners containing vitamin E (0.1% wt. alpha tocopherol) fabricated using the Cold Irradiation Mechanically Annealed (CIMA) process, initially cross-linked with approximately 100 kGy gamma irradiation, and terminally gamma sterilized. The liners were paired with three 40mm CoCr femoral heads and 40mm three ceramic femoral heads. Testing was completed per ASTM F1714 and ISO 14242 on an orbital hip joint wear simulator (Shore Western, California) and lubricated with 90% bovine calf serum, 20mM EDTA, 0.2% wt. NaN. 3. and DI water. A 1.1Hz Paul-type loading waveform with a peak of 2kN was used for a total of 5E6 wear cycles. Three loaded soak controls were used in parallel to adjust for fluid absorption. Samples were weighed every 5E5 wear cycles. RESULTS. The wear rates for the HXL blended vitamin-E liners were calculated using the slope of the linear regression over the steady state and resulted in a wear rate of 0.49mg/Mc. This is a decrease of approximately 95% compared to the 9.54 mg/Mc 28mm ID conventional UHMWPE wear rates as well as a notable difference for the other HXL UHMWPE liner wear rates discussed in the review. DISCUSSION. HXL blended vitamin-E 40mm liners demonstrated an approximate 95% reduction in wear rates compared to a 28mm ID conventional UHMWPE. The reduced wear rate confirmed the design expectation that a higher irradiation dose in the fabrication process resulted in an increased amount of polymer crosslinking. Additionally, the wear rate of the HXL blended vitamin-E liners studied was well below 20mg/Mc, which was shown by Dowd et al. to be the threshold of osteolysis in THA. SIGNIFICANCE. The HXL vitamin E blended UHMWPE liner tested in this study demonstrated reduced wear rates by approximately 95% compared to conventional polyethylene. Osteolysis-causing wear debris is reduced while maintaining other mechanical properties. This liner material and manufacturing process is a promising alternative to conventional polyethylene, but long-term clinical results are warranted

Introduction. Ceramic femoral heads have superior scratch resistant with better wettability and improved wear characteristics compared to metal heads in the laboratory setting. The objective of this study was to compare long-term in vivo wear rates of ceramic and metal femoral heads against conventional polyethylene articulation with cementless stems in young, active patients. Materials and Methods. Thirty-one matched pair of alumina and metal (Cr-Co) femoral heads against conventional polyethylene in young patients (between 45 and 65 years old) were analyzed for wear and failures for mechanical reasons. The match was based on gender and age at the time of surgery. All procedures were performed between June 1989 and May 1992 by a single surgeon via posterolateral approach, using cementless RB (Ranawat-Bernstein) stems, HG II (Harris-Galante) cups, 4150 conventional polyethylene and 28 mm femoral heads. Hospital for Special Surgery (HSS) hip score was used for clinical analysis. Wear measurements were performed between the initial anteroposterior standing pelvis radiographs, at a minimum of one year after the index procedure to eliminate the effect of bedding-in period, and the latest follow-up. Two independent observers analyzed polyethylene wear rates using the computer-assisted Roman 1.70 software. In revision cases, the wear rates were calculated from radiographs prior to revision surgery. A pair student t test was performed to analyze the statistical difference. Two-tailed ρ values less than 0.05 were considered statistically significant. Results. The mean age was 54.5 ± 8.5 at the time of surgery (range 23.3–65). Average clinical and radiographic follow-up were 17 ± 2.1 (range 12.8–20) and 14.1±2.6 years (range 10–19.1) respectively. The mean HSS score in ceramic and metal groups were 30.4 ± 8 (range 24–56) and 36.6 ± 4.7 (range 20–40) respectively. The mean wear rate for the ceramic group and the metal group were 0.086 ± 0.046 mm/year and 0.137 ± 0.052 mm/year, respectively which was statistically significant (p < 0.001). There were no revisions in the ceramic group for osteolysis or loosening, however one patient required a strut graft for femoral osteolysis that was distal to the tip of the implant due to non-circumferential porous coating of the stem. There were 3 cup revisions in the metal group, all for acetabular osteolysis, and no stem lysis or loosening. Discussion and Conclusion. The low mean wear rate of ceramic compared to metal in this study is consistent with previously published laboratory reports. There was no revision for loosening or osteolysis in the ceramic group, which demonstrates superior durability compared to metal femoral heads. The strength of this study is that this is the first long-term report comparing ceramic and metal femoral heads against conventional polyethylene with cementless stems using a matched pair analysis in young patients

INTRODUCTION. Aseptic loosening is the most common failure mode for Total Elbow Arthroplasty (TEA) and is considered to be associated with accelerated polyethylene bearing wear [1, 2]. This study aimed to evaluate three commercially available implant designs under loads associated with daily living. The hypothesis was that more recent designs (Discovery and Nexel) provide greater articular contact areas resulting in lower polyethylene stresses compared to the Coonrad/Morrey (CM). METHODS. Motion tracking was performed on a healthy volunteer during elbow flexion at 0, 45, and 90° shoulder abduction because most daily activities occur with some shoulder abduction [3] resulting in varus stress about the elbow. This kinematic data was used in an OpenSim upper extremity musculoskeletal model [4] to estimate muscle and joint reaction loads with 5lb in hand, consistent with the common clinical restrictions following TEA. Computer aided assemblies of the smallest size implants for each system were imported to ANSYS for finite element analysis. Metallic components were treated as rigid and polyethylene components were modeled using a nonlinear elastoplastic constitutive model calibrated to material data. Articular contacts were frictional. Physiologic joint reaction forces and moments quantified in OpenSim were applied and the resulting peak articular contact area and peak bearing von Mises stresses were assessed. RESULTS. Simulated deformation patterns of CM bearings corresponded well to those reported in retrievals studies [1, 2] supporting the clinical relevance of the modeling approach. Peak stresses for CM and Nexel were consistently found in the central and side bearings respectively. The central bearing stresses remained 2–2.6 times lower in Nexel compared to CM. Peak stress for all three TEA systems increased with shoulder abduction (Fig.1, 2). Highest peak stresses (Fig.2) were obtained in CM and consistently exceeded the polyethylene yield limit; CM showed the lowest contact area (Fig.3). Nexel and Discovery experienced peak polyethylene stresses 26–34% and 17–39% lower than CM respectively (Fig.2). DISCUSSION. Our results support the hypothesis that newer TEA systems provide increased articular contact area and reduced bearing stresses during physiological loading. The cylindrical CM central bearing carries both the joint reaction force and moment leading to edge loading and high stresses (Fig.1). The design of the Nexel central bearing provides limited resistance to varus-valgus moment, thus transferring the moment to the side bearings and reducing central bearing stresses. The hemispherical Discovery bearing design was confirmed to offer a large articular contact area. However, non-concentricity of the contact spheres can lead to edge loading and high polyethylene stresses under off-axis forces. CM and Discovery utilize conventional polyethylene, whereas Nexel utilizes highly cross-linked Vitamin-E polyethylene. This study does not account for the increased wear resistance of Vitamin-E as compared to conventional polyethylene [5]. Long term clinical data are needed to demonstrate how these wear properties, as well as the geometric design which has been shown to impact stresses and contact patterns, translate to in vivo performance. For figures, please contact authors directly

Introduction. Technological advances in the processing of polyethylene have led to improved survivorship of total hip arthroplasty. The purpose of this study was to determine if a second generation highly cross-linked polyethylene could improve upon wear rates compared to conventional and first generation cross-linked polyethylene in patients undergoing primary total hip arthroplasty. Methods. Linear and volumetric wear rates of a second generation highly cross-linked polyethylene were evaluated following primary total hip arthroplasty. There were 44 patients with an average age of 68.6 years and mean follow-up of 5.3 years. Patients were evaluated at six weeks, one, two and five years. Wear rates were determined from digitized AP Pelvis radiograph by an independent observer using Martell's software. Acetabular inclination and femoral head size were also evaluated to determine variability in wear rates. Results. The mean linear wear rate for the entire group was 0.015mm/year (±0.055). There was a 64% decrease in linear wear rate when compared to a first generation highly cross-linked polyethylene from the same institution. There was a 90% decrease in wear rate compared to conventional polyethylene. There were no differences in the linear wear rate between the 32mm vs. larger head sizes (36mm and 40mm). However, there was a 30% increase in volumetric wear rate with larger head sizes. The mean wear rate in patients with cup inclination less than 45 degrees was 0.006mm/year compared with 0.024mm/year for those with an inclination greater than 45 degrees. The amount of linear wear was increased by 4 times in patients with a cup inclination of greater than 45 degrees. There was no evidence of any osteolysis in this group of patients. Conclusion. Our data with a mean follow-up of 5.3 years, using a second generation highly cross-linked polyethylene, demonstrates a dramatic decrease in incidents of linear wear compared to conventional polyethylene and first generation highly cross-linked polyethylene (Figure 1). Of concern is the higher volumetric wear rate noted with larger head sizes and increased linear wear rates with cup inclination angles of greater than 45 degrees. Despite improvements in wear rates using a second generation highly cross-linked polyethylene, cup orientation and choice of head size play significant roles in implant survivorship

Total hip arthroplasty (THA) is one of the most successful and commonly performed surgical interventions worldwide. Based on registry data, at one-year post THA, implant survivorship is nearly 100% and patient satisfaction is 90%. A novel, porous coated acetabular implant was introduced in Europe and Australia in 2007. Several years after its introduction, warnings were issued for the system when used with metal-on-metal bearings due to adverse local tissue reaction, with one study reporting a 24% failure rate (Dramis et al. 2014). A subsequent 2018 study by Teoh et al. showed that the acetabular system had a survival rate of 98.9% at five years when used with conventional polyethylene or ceramic bearing surfaces. The current study was conducted to determine the safety and effectiveness of the acetabular system using standard highly-crosslinked polyethylene (XLPE) and ceramic liners at five-year follow-up. Our hypothesis was that the acetabular system would exhibit survivorship comparable to other acetabular components on the market at five-year follow-up. A prospective, non-randomized study was conducted from February 2009 to June 2017 at eight sites in Canada and the USA. One hundred fifty-five hips were enrolled and 148 hips analyzed after THA indicated for degenerative arthritis. At five-year follow-up, 103 subjects remained for final analysis. All patients received a zero, three, or multi-hole R3 acetabular shell with Stiktite porous coating (Smith & Nephew, Inc., Memphis, TN, USA). Standard THA surgical techniques were employed, with surgical approach and either of a XLPE or ceramic bearing surface chosen at the discretion of the surgeon. The primary outcome was revision at five-years post-op with secondary outcomes including the Harris Hip Score (HHS), Hip Disability and Osteoarthritis Outcome Score (HOOS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), radiographic analysis, and post-operative adverse events. Data and outcomes were analyzed using summary statistics with 95% confidence intervals, t-tests, and Wilcoxon Rank tests. At five-year follow-up the overall success rate was 97.14% (95% CI: 91.88–100). When analyzed by liner type, the success rate was 96.81% (95% CI: 90.96–99.34) for polyethylene (n=94) and 100% (95% CI: 71.51–100) for ceramic (n=11), with no significant difference between either liner type (p=1). There were three revisions during the study (1.9%), two for femoral stem revision post fracture, and one for deep infection. The HHS (51.36 pre-op, 94.50 five-year), all 5 HOOS sub-scales, and WOMAC (40.9 pre-op, 89.13 five-year) scores all significantly improved (p < 0 .001) over baseline scores at all follow-up points. One (0.7%) subject met the criteria for radiographic failure at one-year post-op but did not require revision. Six (1.8%) of the reported adverse events were considered related to the study device, including four cases of squeaking, one bursitis, and one femur fracture. Results from this five-year, multicenter, prospective study indicate good survivorship for this novel, porous coated acetabular system. The overall survivorship of 97.14% at five-year follow-up is comparable to that reported for similar acetabular components and aligns with previous analyses (Teoh et al. 2018)

Introduction. Dislocation is one of the leading causes of revision after primary total hip arthroplasty (THA). Polyethylene wear is one of the risk factors for late dislocations (>2 years). It can induce an inflammatory response resulting in distension and thinning of the pseudocapsule, predisposing the hip to dislocation. Alternatively, eccentric seating of the femoral head in a worn out socket may result in an asymmetric excursion arc predisposing the hip to impingement, levering out and dislocation. Highly cross linked polyethylene has a significantly lower wear rate as compared to conventional polyethylene. Incidence of late dislocations has been shown to be significantly greater with conventional polyethylene bearings as compared to ceramic bearings. However, there is no literature comparing the risk of dislocation between ceramic- on- ceramic (CoC) bearings with metal/ceramic- on- cross linked polyethylene (M/CoP) bearings and this was the aim our study. Methods. Data regarding revision for dislocation after primary THA for osteoarthritis (OA) between September 1999 and December 2013 was obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOA NJRR). Revision risk for dislocation was compared between CoC, CoP, and MoP bearings. Only those THAs with 28 mm, 32 mm, or 36 mm heads were included in the study. Results. The numbers at risk (0 years) in the CoC, CoP, and MoP groups were 53,648; 23,746; and 90,040 THAs respectively. The overall revision (dislocation)/100 observed years was 0.13. Revision rate/100 observed years in the CoC, CoP, and MoP groups was 0.12, 0.12, and 0.16 respectively. The cumulative percentage revision for dislocation (CPRD) for the three bearing types is shown in figure 1. The CPRD at 12 years in the CoC, CoP, and MoP groups was 0.9, 1.0 and 1.2 respectively. The rise in CPRD between 2 and 12 years (late dislocations) was 0.4, 0.6, and 0.6 in the CoC, CoP, and MoP groups respectively (Figure 1). The age and gender adjusted hazards ratio (HR) for revision for dislocation in CoC vs. CoP groups was 1.05 (p=0.684, 1month+); in MoP vs. CoP group was 1.45 (p<0.001, entire period) and MoP vs. CoC group was 1.55 (p<0.001, 6 month+). Computation of age and gender adjusted HR comparing the three bearing groups after stratification according to head sizes (28 mm, 32 mm and 36 mm) showed no significant difference in HR after 3 months (p≥0.061). Conclusion. The revision (dislocation)/100 observed years was greater in the MoP group as compared to CoC and CoP groups (MoP > CoC = CoP). The age and gender adjusted HR (revision for dislocation) was significantly greater in the MoP group as compared to CoC and CoP groups after 6 months. However, when the data was stratified according to head sizes, the age and gender adjusted HR was similar between the three bearing groups after 3 months. In conclusion, there is no significant difference in the risk of revision for dislocation between CoC, CoP, and MoP bearings after adjusting for age, gender, and head size after 3 months

Dual mobility components for total hip arthroplasty provide for an additional articular surface, with the goals of improving range of motion, jump distance, and overall stability of the prosthetic hip joint. A large polyethylene head articulates with a polished metal acetabular component, and an additional smaller metal or ceramic head is snap-fit into the large polyethylene. In some European centers, these components are routinely used for primary total hip arthroplasty. However, their greatest utility will be to prevent and manage recurrent dislocation in the setting of revision total hip arthroplasty. Several retrospective series have shown satisfactory results for this indication at medium-term follow-up times. The author has used dual mobility components on two occasions to salvage a failed constrained liner. At least one center reports that dual mobility outperforms 40mm femoral heads in revision arthroplasty. Modular dual mobility components, with screw fixation, are the author's first choice for the treatment of recurrent dislocation, revision of failed metal-on-metal resurfacing or total hips, unipolar arthroplasties, and salvage of failed constrained liners. There are concerns of elevated metal levels with one design, and acute early intra-prosthetic dissociation following attempted closed reduction. Total hip surgeons no longer use conventional polyethylene, autologous blood donation, or a hemovac drain; now constrained components join these obsolete techniques! In 2018, a dual mobility component, rather than a constrained liner, is the preferred solution in revision surgery to prevent and manage recurrent dislocation

INTRODUCTION. Many studies have looked at the effects of titanium tibial baseplates compared to cobalt chrome baseplates on backside wear. However, the surface finish of the materials is usually different (polished/unpolished) [1,2]. Backside wear may be a function not only of tray material but also of the locking mechanism. The purpose of this study was to evaluate the wear performance of conventional polyethylene inserts when mated with titanium tibial trays or cobalt chrome tibial trays that both have non-polished topside surfaces. MATERIALS AND METHODS. Three titanium (Ti) trays were used along with three cobalt chrome (CoCr) trays. The Ti trays underwent Type II anodization prior to testing. All trays were Triathlon® design (Stryker Orthopaedics, Mahwah, NJ). Tibial inserts were manufactured from GUR 1020 conventional polyethylene then vacuum/flush packaged and sterilized in nitrogen (30 kGy). Appropriate sized CoCr femoral components articulated against the tibial inserts (Triathlon®, Stryker Orthopaedics, Mahwah, NJ). Surface roughness of the tibial trays was taken prior to testing using white light interferometry (Zygo Corp, Middlefield, CT). A 6-station knee simulator (MTS, Eden Prairie, MN) was used for testing. Two phases were conducted. The first phase used a normal walking profile, as dictated by ISO 14243-3 [3]. The second phase used waveforms created specifically for stair climbing kinematics. Testing was conducted at a frequency of 1 Hz for 2 million cycles for each test with a lubricant of Alpha Calf Fraction serum (Hyclone Labs, Logan, UT) diluted to 50% with a pH-balanced 20-mMole solution of deionized water and EDTA (protein level = 20 g/l) [4]. The serum solution was replaced and inserts were weighed for gravimetric wear at least every 0.5 million cycles. Standard test protocols were used for cleaning, weighing and assessing the wear loss of the tibial inserts [5]. Soak control specimens were used to correct for fluid absorption with weight loss data converted to volumetric data (by material density). Statistical analysis was performed using the Student's t-test (p<0.05). RESULTS. White light interferometry measurements (Figure 1) showed a significant difference in surface roughness between the Ti and CoCr tibial trays (p < 0.01). Figure 2 displays the results of wear testing after 2 million cycles for walking and stair climbing kinematics and showed no significant difference in wear rate between the two tibial trays for either test. The large standard deviation for the CoCr trays during stair climbing kinematics is due to one outlier that had 60% higher wear than the remaining two stations. Without this station, the average of the remaining two CoCr stations was 7.6 mm. 3. /mc, which was similar to the average obtained using Ti tibial trays. Figure 3 shows the backside surfaces of the polyethylene inserts after 2 million cycles using the stair climbing kinematics. Visually, the inserts mated with the Ti trays showed less of a stenciling effect that those mated with CoCr trays. The location of the stenciled area corresponded to the location of the femoral condyle during the loading cycle. DISCUSSION. Although Ti has different material properties than CoCr, the results of this study show that the wear performance was not adversely affected when Ti tibial trays were substituted for standard CoCr tibial trays under normal walking and stair climbing kinematics. Even though there are differences between the two materials, the documented wear was not significantly different possibly owing to the specific locking mechanism tested

Dual mobility components for total hip arthroplasty provide for an additional articular surface, with the goals of improving range of motion, jump distance, and overall stability of the prosthetic hip joint. A large polyethylene head articulates with a polished metal acetabular component, and an additional smaller metal or ceramic head is snap-fit into the large polyethylene. In some European centers, these components are routinely used for primary total hip arthroplasty. However, their greatest utility will be to prevent and manage recurrent dislocation in the setting of revision total hip arthroplasty. Several retrospective series have shown satisfactory results for this indication at medium-term follow-up times. The author has used dual mobility components on two occasions to salvage a failed constrained liner. At least one center reports that dual mobility outperforms 40mm femoral heads in revision arthroplasty. Modular dual mobility components, with screw fixation, are the author's first choice for the treatment of recurrent dislocation, revision of failed metal-metal resurfacing, total hips, unipolar arthroplasties, and salvage of failed constrained liners. There are concerns of elevated metal levels with one design, and acute early intra-prosthetic dissociation following attempted closed reduction. Total hip surgeons no longer cement Charnley acetabular components, use conventional polyethylene, autologous blood donation, or a drain; now constrained components join these obsolete techniques! In 2017, a dual mobility component, rather than a constrained liner, is the preferred solution in revision surgery to prevent and manage recurrent dislocation