THE OTTO AUFRANC AWARD: Highly Cross-linked Polyethylene in Total Hip Arthroplasty: Randomized Evaluation of Penetration Rate in Cemented and Uncemented Sockets Using Radiostereometric Analysis

How Research Improves Clinical Care: The Case for Orthopaedic Surgeon Research Leadership and Collaboration: AOA Critical Issues Symposium

ABSTRACT

Improving the performance and impact of orthopaedic research is a critical leadership challenge. Musculoskeletal (MSK) conditions are a leading cause of disability worldwide, for which research investment and performance lags far behind the burden of disease. In the United States, MSK disorders account for the highest health care costs, have increased in incidence at the fastest rate, and exceed the combined costs of cardiovascular diseases and neoplasms. Despite the cost to society, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), with primary responsibility for MSK research, receives <1.4% of the funds allocated to the National Institutes of Health (NIH). Although orthopaedic surgeons are leading providers of MSK clinical care, the dearth of orthopaedic clinician-scientists also greatly reduces representation of MSK scientific and clinical expertise among academic and scientific leaders. The goals of this symposium were to highlight the critical need for greater prioritization and investment in orthopaedic research and to engage orthopaedic leaders in addressing these needs. Compelling stories of research success from 3 orthopaedic chairs were featured to highlight how orthopaedic surgeon leadership in bench-to-bedside research substantially advances MSK clinical care. Seminar participants also emphasized the need to improve evidence-based clinical practice for which multicenter prospective cohort and registry studies represent opportunities for broader involvement. Prioritization of orthopaedic clinician-scientist development and formation of multidisciplinary partnerships with basic and translational scientists were emphasized as critical needs to advance MSK health. It is critical for orthopaedic chairs to "be invested in" and to "invest in" the success of orthopaedic research. This investment includes developing a professional climate that values research achievement and collaboration as well as implementing strategies to support and sustain research success. Finally, orthopaedic leaders need to advocate for federal research funding to be proportional to the economic burden of disease for which MSK conditions carry the highest current and projected costs. With health-care costs accounting for nearly one-fifth of the U.S. economy, increasing the investment in orthopaedic research to reduce the prevalence, disability, and morbidity from MSK disease needs to be a top orthopaedic and national leadership priority.

Migration patterns of acetabular cups: a systematic review and meta-analysis of RSA studies

BACKGROUND AND PURPOSE

We conducted a systematic review and meta-analysis of RSA studies to investigate the early and long-term migration patterns of acetabular cups and the influence of implant factors on cup migration over time.

METHODS

We performed a systematic search of PubMed, Embase, and Scopus databases to identify all RSA studies of cup migration following primary total hip replacement (THR). Proximal migration at 3 and 6 months, 1, 2, 5, and 10 years were considered for analysis. Implant factors investigated included fixation type, head size, bearing surface, uncemented coating design, and the decade of RSA introduction.

RESULTS

47 studies reported the proximal migration of 83 cohorts (2,328 cups). Besides 1 threaded cup design, no implant factor investigated was found to significantly influence proximal migration. The mean pooled 2-year proximal migration of cemented cups (0.14 mm, 95% confidence interval [CI] 0.08-0.20) was not significantly different from uncemented cups (0.12 mm, CI 0.04-0.19). The mean pooled proximal migration at 6 months was 0.11 mm (CI 0.06-0.16) and there was no significant increase between 6 months and 2 years (0.015 mm, CI 0.000-0.030). 27 of 75 cohorts (36%) reported mean proximal migration greater than 0.2 mm at 2 years, which has previously been identified as a predictor of implants at risk of long-term loosening.

CONCLUSION

Our meta-analysis demonstrated that the majority of cup migration occurs within the first 6 months. With one exception, no implant factors influenced the 2-year proximal migration of acetabular cups. 36% of studies with 2-year migration were considered at risk of long-term loosening. Further investigation and comparison against long-term survivorship data would validate 6-month and/or 1-year proximal migration measurements as an earlier predictor of long-term loosening than the current 2-year threshold.

Head, acetabular liner composition, and rate of revision and wear in total hip arthroplasty: a Bayesian network meta-analysis

Total hip arthroplasty (THA) is a common procedure for patients suffering from hip pain e.g. from osteoarthritis, osteonecrosis, or hip fractures. The satisfaction of patients undergoing THA is influenced by the choice of implant type and material, with one key factor being the selection of the appropriate material combination for the bearing surface. In this Bayesian network meta-analysis, we investigated the impact of material combinations for the bearing surface on the longevity of hip implants. The wear penetration rate per year and the total wear penetration in the liner resulting from different material combinations, as well as the survival rate at last follow-up, were examined. We analyzed a total of 663,038 THAs, with 55% of patients being women. Mean patient age was 59.0 ± 8.1 years and mean BMI 27.6 ± 2.6 kg/m2. The combination of an aluminium oxide (Al2O3) head and an Al2O3 liner demonstrated the lowest wear penetration at last follow-up and the lowest rate of wear penetration per year. Additionally, the combination of a crosslinked polyethylene (XLPE) liner and a zircon oxide (ZrO2) head demonstrated the lowest rate of revision at last follow-up. These findings underscore the importance of careful material selection for hip implant bearing surfaces to optimize their longevity and patient satisfaction after THA.

Risk factors for liner wear and head migration in total hip arthroplasty: a systematic review

Total hip arthroplasty (THA) is a successful orthopaedic surgical procedure, and its longevity depends on bearing components and implant fixation. Optimizing polyethylene and ceramics has led to improved wear parameters and contributed to improved long-term outcomes. The present systematic review investigated whether time span from implantation, patient characteristics and performance status exert an influence on liner wear and head migration in THA. This study was conducted in conformity to the 2020 PRISMA guidelines. All the clinical investigations which reported quantitative data on the amount of liner wear and head migration in THA were considered. Only studies which reported quantitative data at least on one of the following patient characteristics were suitable: mean age, mean BMI (kg/m2), sex, side, time span between the index THA and the last follow-up (months) were eligible. A multiple linear model regression analysis was employed to verify the association between patient characteristics and the amount of liner wear and/or head migration. The Pearson Product-Moment Correlation Coefficient was used to assess the association between variables. Data from 12,629 patients were considered. The mean length of the follow-up was 90.5 ± 50.9 months. The mean age of patients at surgery was 58.4 ± 9.4 years, and the mean BMI was 27.2 ± 2.5 kg/m2. 57% (7199 of 12,629 patients) were women, and in 44% (5557 of 12,629 patients) THAs were performed on the left. The mean pre-operative Harris hip score was 46.5 ± 6.0 points. There was evidence of a moderate positive association between the amount of liner wear and the time elapsed between the index surgery to the follow-up (P = 0.02). There was evidence of a moderate positive association between the amount of head migration and the time elapsed between the index surgery to the follow-up (P = 0.01). No further statistically significant association was found. The time elapsed between the index surgery to the follow-up was the most important factor which influence the head migration and liner wear in THA. Patients' characteristics and preoperative physical activity did not influence the amount of head migration and liner wear.

Cup positioning and its effect on polyethylene wear of vitamin E- and non-vitamin E-supplemented liners in total hip arthroplasty: radiographic outcome at 5-year follow-up

BACKGROUND

Aseptic loosening remains a challenging problem after total hip arthroplasty. Accurate cup placement and supplementation of antioxidants in acetabular liners might reduce material failure rates. The aim of this study is to assess the effect of the cup position on the wear behaviour of UHMWPE-XE and UHMWPE-X liners in vivo using virtual radiographs.

METHODS

We conducted a prospective, randomized, controlled, multicenter trial. Clinical data of 372 probands were analyzed. Anteroposterior pelvic X-rays of 324 patients immediately postoperatively and after 1 and 5 years were evaluated by the RayMatch® analysis software regarding cup position and wear behaviour.

RESULTS

Mean cup anteversion was 20.3° (± 7.4) and inclination was 41.9° (± 7.0) postoperatively. 62.3% of all patients had an anteversion and inclination within the Lewinnek safe zone. Anterior and anterolateral approaches led to significantly higher cup anteversion compared to lateral approaches (27.3° ± 5.5; 20.9° ± 7.2; 17.5° ± 6.6; p < 0.001 and p = 0.001, respectively). Mean anteversion increased to 24.6° (± 8.0) after 1 year (p < 0.001). Only one revision occurred because of implant dislocation. Wear rates from UHMWPE-X and UHMWPE-XE did not differ significantly. Anteversion angles ≥ 25° correlated to increased polyethylene wear (23.7 µm/year ± 12.8 vs. 31.1 µm/year ± 22.8, p = 0.012) and this was amplified when inclination angles were ≥ 50° (23.6 µm/year ± 12.8 vs. 38.0 µm/year ± 22.7, p = 0.062).

CONCLUSION

Anterior approaches lead to the highest inaccuracy of cup placement, but cup positioning outside the Lewinnek safe zone does not necessarily cause higher dislocation rates. Moreover, mean anteversion increased by approximately four degrees within the first year after operation, which is expected to be functional due to a regularization of pelvic tilt after intervention. Mid-term wear rates of UHMWPE-X and UHMWPE-XE liners are comparable, but steep cup positions lead to significantly increased polyethylene wear. In summary, a re-evaluation of target zones for intraoperative cup positioning might be considered. In the long-term reduced oxidative embrittlement could lead to superior wear behaviour of vitamin E-blended liners.

New polyethylenes in total hip arthroplasty : a 20- to 22-year follow-up study

AIMS

A significant reduction in wear at five and ten years was previously reported when comparing Durasul highly cross-linked polyethylene with nitrogen-sterilized Sulene polyethylene in total hip arthroplasty (THA). We investigated whether the improvement observed at the earlier follow-up continued, resulting in decreased osteolysis and revision surgery rates over the second decade.

METHODS

Between January 1999 and December 2001, 90 patients underwent surgery using the same acetabular and femoral components with a 28 mm metallic femoral head and either a Durasul or Sulene liner. A total of 66 hips of this prospective randomized study were available for a minimum follow-up of 20 years. The linear femoral head penetration rate was measured at six weeks, one year, and annually thereafter, using the Dorr method on digitized radiographs with a software package.

RESULTS

In the Durasul group, no patients underwent revision due to loosening or showed radiological evidence of osteolysis. In the Sulene group, four patients (four hips) were revised due to femoral component loosening. The 20-year cumulative failure incidence in the presence of the competing event of death for revision surgery was 4.5% (95% confidence interval (CI) 0.8 to 13.6) in the Durasul group, and 8.9% (95% CI 2.8 to 19.5) in the Sulene group. The mean wear one year after surgery was 0.09 mm (SD 0.007) in the Durasul group and 0.24 (SD 0.015) in the Sulene group (p < 0.001). From one to 20 years after surgery, the mean total penetration was 0.32 mm (SD 0.045) in the Durasul group and 1.07 mm (SD 0.13) in the Sulene group (p < 0.001). Mean femoral head penetration at 20 years was approximately 70.0% less in the Durasul group than the Sulene group.

CONCLUSION

The significant reduction in femoral head penetration obtained with the Durasul compared with Sulene in uncemented THA resulted in lower osteolysis and revision rates after 20 years.Cite this article: Bone Joint J 2022;104-B(9):1032-1038.

Oxidized zirconium versus cobalt-chrome femoral heads in total hip arthroplasty: a multicentre prospective randomized controlled trial with ten years' follow-up

AIMS

This study reports the ten-year wear rates, incidence of osteolysis, clinical outcomes, and complications of a multicentre randomized controlled trial comparing oxidized zirconium (OxZr) versus cobalt-chrome (CoCr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) and highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

METHODS

Patients undergoing primary THA were recruited from four institutions and prospectively allocated to the following treatment groups: Group A, CoCr femoral head with XLPE liner; Group B, OxZr femoral head with XLPE liner; and Group C, OxZr femoral head with UHMWPE liner. All study patients and assessors recording outcomes were blinded to the treatment groups. The outcomes of 262 study patients were analyzed at ten years' follow-up.

RESULTS

Patients in Group C were associated with increased mean liner wear rates compared to patients in Group A (0.133 mm/yr (SD 0.21) vs 0.031 mm/yr (SD 0.07), respectively; p < 0.001) and Group B (0.133 mm/yr (SD 0.21) vs 0.022 mm/yr (SD 0.05), respectively; p < 0.001) at ten years' follow-up. Patients in Group C were also associated with increased risk of osteolysis and aseptic loosening requiring revision surgery, compared with patients in Group A (7/133 vs 0/133, respectively; p = 0.007) and Group B (7/133 vs 0/135, respectively; p = 0.007). There was a non-statistically significant trend towards increased mean liner wear rates in Group A compared with Group B (0.031 mm/yr (SD 0.07) vs 0.022 mm/yr (SD 0.05), respectively; p = 0.128). All three groups were statistically comparable preoperatively and at ten years' follow-up when measuring normalized Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.410), 36-Item Short Form Health Survey (p = 0.465 mental, p = 0.713 physical), and pain scale scores (p = 0.451).

CONCLUSION

The use of UHMWPE was associated with progressively increased annual liner wear rates after THA compared to XLPE. At ten years' follow-up, the group receiving UHMWPE demonstrated an increased incidence of osteolysis and aseptic loosening requiring revision surgery compared to XLPE. Femoral heads composed of OxZr were associated with trend towards reduced wear rates compared to CoCr, but this did not reach statistical significance and did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two femoral head components. Cite this article: Bone Joint J 2022;104-B(7):833-843.

Discussion of Orientation and Performance of Crosslinked Ultrahigh-Molecular-Weight Polyethylene Used for Artificial Joints

Previously, the orientation structure of ultrahigh-molecular-weight polyethylene (UHMWPE) for artificial joints was considered to be unchanged after irradiation crosslinking. Therefore, much of the research related to the long-term failure of artificial joints has focused on material improvements. In this study, ultrasmall-angle X-ray scattering (USAXS) and the small/wide-angle X-ray scattering (SAXS-WAXS) combined technique reveal that the orientation structures of UHMWPE materials at all scales (nanoscale to microscale) are responsible for the long-term failure of artificial joints. To further illustrate the formation of these hierarchical oriented structures, a simple model is presented. In this model, first, the migration of free radicals plays a vital role, and the different steric hindrances in different directions directly lead to uneven migration behavior of free radicals. Second, the uneven migration of free radicals contributes to an inhomogeneous concentration of free radicals, thus resulting in observable crosslinking nonuniformities. Finally, all the hierarchical structural nonuniformities promote long-term failure of artificial joints after long-term wear.

Evaluation of Safety and Medium-Term Functional Outcomes of a Medial Fixed-Bearing Unicompartmental Knee Arthroplasty with Ultra-Highly Cross-Linked Polyethylene

The primary objective of this study was to evaluate the in vivo safety of a unicompartmental knee arthroplasty design with sequentially annealed cross-linked polyethylene by evaluating reoperation rate, in particular those related to excessive polyethylene wear or breakage. The secondary objective was to examine functional outcomes via standardized questionnaires. This was a 5-year institutional review board-approved prospective single-surgeon case series of the first 152 consecutive patients with symptomatic medial unicompartmental osteoarthritis implanted with a partial knee replacement between May 2010 and December 2014. Study participants were asked to complete the Knee injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthrtis Index (WOMAC) questionnaires at preoperation and 2 to 5 years postoperation. Major complications and all reoperations were recorded and we produced Kaplan-Meier survivorship curves with the end point of revision to TKA. Pre- and postoperative differences for KOOS and WOMAC were evaluated by paired t-tests. The median length of follow-up was 7.2 (0-9.72) years. Seven patients required revision surgery to TKA (4.9% of patients): four with progression of arthritis in other compartments, two for infection, and one for loosening of the femoral component and subsequent progression of pain. There were no failures of polyethylene. Survival of cohort was 99.3 and 97.9% at 2 and 5 years, respectively. Patients significantly improved (p-value < 0.001) between preoperative assessment and at 2 years, with no decline at 5 years postoperation. These preliminary midterm results with this fixed-bearing design and cross-linked polyethylene were encouraging with no catastrophic failures of polyethylene. Patient reported outcomes were significantly improved and revision rates were acceptable and lower than registry reported results.

Radiolucent lines do not affect the longevity of highly cross-linked polyethylene cemented components in total hip arthroplasty

AIMS

We aimed to evaluate the long-term outcome of highly cross-linked polyethylene (HXLPE) cemented acetabular components and assess whether any radiolucent lines (RLLs) which arose were progressive.

METHODS

We retrospectively reviewed 170 patients who underwent 187 total hip arthroplasties at two hospitals with a minimum follow-up of ten years. All interventions were performed using the same combination of HXLPE cemented acetabular components with femoral stems made of titanium alloy. Kaplan-Meier survival analysis was performed for the primary endpoint of acetabular component revision surgery for any reason and secondary endpoint of the appearance of RLLs. RLLs that had appeared once were observed over time. We statistically assessed potential relationships between RLLs and a number of factors, including the technique of femoral head autografting and the Japanese Orthopaedic Association score.

RESULTS

The mean follow-up period was 13.0 years (10.0 to 16.3). Femoral head autografting was performed on 135 hips (72.2%). One acetabular component was retrieved because of deep infection. No revision was performed for the aseptic acetabular loosening. The Kaplan-Meier survival curve for the primary and secondary endpoints were 98.2% (95% confidence interval (CI) 88.6% to 99.8%) and 79.3% (95% CI 72.8% to 84.6%), respectively. RLLs were detected in 38 hips (21.2%), at a mean of 1.7 years (1 month to 6 years) postoperatively. None of the RLLs were progressive, and the presence of RLLs did not show a significant association with the survival and clinical score. RLLs were more frequently observed in hips without femoral head autografts than in those with autografts.

CONCLUSION

The use of HXLPE cemented acetabular components in total hip arthroplasty demonstrated excellent clinical outcomes after ten years, and no RLLs were progressive, and their presence did not affect the outcome. Femoral head autografting did not negatively impact the acetabular component survival or the appearance of RLLs. Cite this article: Bone Joint J 2021;103-B(10):1604-1610.

The use of acetabular screws in total hip arthroplasty and its influence on wear and periacetabular osteolysis in the long-term follow-up

Purpose

The cementless implantation of hip replacement cups may be performed with and without the additional use of acetabular screws. If the surgeon uses screws or not depends on variable factors. In general, the use of screws is intended to increase the primary stability of the cup. Whether screws increase the initial stability of the cup construct, or even reduce it in part, is the subject of considerable debate in the literature. It is also unclear whether the additional screws lead to increased wear or increased periacetabular osteolysis over the long-term course.

Methods

Two hundred eleven patients from a previous study with a minimum follow-up of 10.7 years were included. Of these, 68 patients with 82 total hip arthroplasties (THA) were given clinical and radiological follow-up examinations. Of these, 52 had been fitted without screws and 30 with screws. On the basis of radiographs, annual wear and osteolysis were quantified. The clinical results were recorded by means of VAS, HHS, and WOMAC scores.

Results

Significantly more periacetabular osteolysis was found if additive acetabular screws had been used. No difference was found in relation to the volumetric wear per year. Likewise, no difference was found with regard to the clinical scores.

Conclusions

The use of additive acetabular screws leads to increased osteolysis in the periacetabular bone stock. Insofar as the primary stability of the cementless cup construct allows it, no additional acetabular screws should be used.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00264-021-05219-7.

Biomaterial Properties of Femur Implant on Acetabulum Erosion: A Review

The hip is one in every of the various joint at intervals the body. The correct operating of this joint is essential. For the aim once the hip is injured whole, a substitution procedure of the entire joint ought to be done to reinstate its operating, that is known as absolute hip surgical process. It is finished with the assistance of inserts of various biomaterials, as an example, polymers, metals, and pottery. The primary issues with regard to the utilization of various biomaterials are the reaction of the body's instrument to wear trash. Throughout this audit, biomaterials that are developing is talked regarding aboard the wear and tear and tear conduct and instrument. To boot, the numerous properties of the biomaterials are talked regarding aboard the expected preferences and drawbacks of their utilization. Further, the blends of various biomaterials at intervals the articulating surfaces are cleft and so the problems regarding their utilization are assessed. This paper hopes to passes away an in depth review of the trauma fringe of bearing surfaces of hip prosthetic devices. Additionally, this paper can offer AN ordered blueprint of the materials nearby their favorable circumstances and detriments and besides the conceivable outcomes of use. Keywords: - Hip implant; Biomaterials; Wear mechanism; Bearing surfaces; Polymers

Vitamin E-enriched polyethylene bearings are not inferior to Arcom bearings in primary total knee arthroplasty at medium-term follow-up

INTRODUCTION

The release of wear particles can be responsible for periprosthetic osteolysis, which can in turn, lead to aseptic loosening. Vitamin E-infused polyethylene (HXLPE Vit-E) has been shown, in vitro, to be more resistant to wear than conventional polyethylene (UHMWPE) by its crosslinking (HXLPE) and its higher resistance to oxidation. After reading a case report of a fracture of a vitamin E-enriched HXLPE bearing, the aim of this retrospective study was to evaluate fracture risk and clinical inferiority or not of vitamin-E HXLPE compared to conventional polyethylene in total knee arthroplasty (TKA).

MATERIALS AND METHODS

Three hundred and forty-nine patients (403 TKAs) were contacted, to find out whether they had undergone revision surgery for any reason after a mean (SD) of 7 (1.5) years. Follow-up control radiographs were analyzed for periprosthetic radiolucent lines (RLL) and loosening. Two different Patient Reported Outcome Measurements Scores (PROMS), KOOS and FJS-12, were utilized to assess the daily functionality and identify potential problems.

RESULTS

No statistically significant difference in revision rate, occurrence of aseptic loosening or RLL nor outcome as measured with PROMS was observed.

CONCLUSIONS

No bearing fractures or clinical inferiority was observed for vitamin E-enriched HXLPE at medium-term follow-up (7 years) compared to conventional Arcom polyethylene.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Incidence of Osteolysis and Aseptic Loosening Following Metal-on-Highly Cross-Linked Polyethylene Hip Arthroplasty: A Systematic Review of Studies with Up to 15-Year Follow-up

BACKGROUND

This study compared the incidence of osteolysis, aseptic loosening, and revision following use of highly cross-linked polyethylene (HXLPE) or conventional polyethylene (CPE) at medium to long-term (>5 to 15 years) follow-up in primary total hip arthroplasty (THA). Incidences were quantified and compared with regard to age and method of implant fixation.

METHODS

Using the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines, 12 randomized controlled trials and 18 cohort studies were investigated for evidence-based outcomes following HXPLE and CPE use in 2,539 hips over a 5 to 15-year follow-up.

RESULTS

Lower rates of osteolysis, aseptic loosening, and implant revision were reported following use of HXLPE liners. Osteolysis was reduced from 25.4% with CPE to 4.05% with HXLPE in young patients, and from 29.7% to 6.6% in the older patient cohort. Similarities in osteolysis rates were observed when cemented (24.9% for CPE and 6.5% for HXLPE) and uncemented components (32.8% for CPE and 7.1% for HXLPE) were compared. No clear advantage in the type of HXLPE used was observed.

CONCLUSIONS

Over a follow-up period of up to 15 years, when compared with CPE, use of HXLPE liners reduced the incidence of osteolysis, aseptic loosening, and implant revision, regardless of the fixation method and including in younger and potentially more active patients.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Short-term clinical and radiographic outcomes of total hip arthroplasty with PMPC-grafted highly cross-linked polyethylene liners against 32-mm femoral heads

We evaluated the clinical and radiographic outcomes of femoral head penetration and total hip arthroplasties with untreated and poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC)-grafted highly cross-linked polyethylene (HXLPE) acetabular liners against 26-, 28-, and 32-mm cobalt-chromium alloy femoral heads 3 years after the index surgery. Three combinations of the articulating surfaces were evaluated in the present study: untreated or PMPC-grafted HXLPE liner against 26- or 28-mm femoral heads (n = 16, 24) [control (26 or 28 mm) and PMPC (26 or 28 mm)] and PMPC-grafted HXLPE liner against 32-mm femoral heads (n = 64) [PMPC (32 mm)]. The clinical outcomes improved at 3 years postoperatively for the groups. No periprosthetic osteolysis or acetabular component migration was detected, and no revision surgery was performed among the groups. The steady-state wear rate of the PMPC (26 or 28 mm) group (0.021 mm/year) was lower than that of the control (26 or 28 mm) group (- 0.015 mm/year); the steady-state wear was under the clinical threshold. In contrast, the steady-state wear rate of the PMPC (32 mm) group (-0.006 mm/year) showed no significant difference when compared to that of the PMPC (26 or 28 mm) group (p < 0.01). The results obtained in the present study clearly demonstrate that PMPC-grafting onto an HXLPE surface improved the wear resistance of acetabular liners, even when coupled with larger femoral heads. Although further follow-up evaluations are required, PMPC-grafted HXLPE acetabular liners may be a promising approach to extend the longevity of artificial joints.

Pelvic tilt between supine and standing after total hip arthroplasty an RSA up to seven years after the operation

The pose of the prosthetic components after total hip arthroplasty (THA) is commonly evaluated on conventional radiographs. Any change of the pelvic position after the operation in supine and between supine and standing position with time will influence validity of the measurements. We evaluated the changed pelvic tilt angle (PTA) in supine and standing position up to 7 years after operation. The aims of our study were (a) to evaluate if the PTA change over time after THA, (b) to assess any difference in PTA between supine and standing positions, and (c) to investigate whether factors such as gender, the condition of the opposite hip or low-back pain have any influence on PTA after THA. Repeated radiostereophotogrammetric radiographs of 106 patients were studied. Patients had been examined in the supine position postoperatively, and in both supine and standing positions at 6 months and 7-year follow-up. Measurements of supine patients showed an increasing mean posterior pelvic tilt over time. From supine to standing, the pelvis tilted in the opposite direction. At 6 months, the mean anterior tilt was 3.6° ± 3.8° (confidence interval [CI]: 2.8° to 4.3°) which increased to 6.4° ± 3.9° (CI: 5.7° to 7.2°) at 7 years. The mean changes in pelvic rotations around the longitudinal and sagittal axis were less than 1 degree, in both positions. In individual patients, this change reached about 11.0 degrees in supine and 18.0 degrees when standing.

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

BACKGROUND

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.

METHODS

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 5 years postoperatively. The radiographs were analyzed using the observer-independent analysis software RayMatch^® (Raylytic GmbH, Leipzig, Germany).

RESULTS

The mean wear rate was measured to be 23.6 μm/year (SD 13.7; range 0.7-71.8 μm). There were no significant differences between the two cohorts (UHMWPE-X: 23.2 μm/year vs. UHMWPE-XE: 24.0 μm/year, p = 0.73). Cup anteversion significantly changed within the 1st year 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)].

CONCLUSION

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.

Polyethylene Wear With Ceramic and Metal Femoral Heads at 5 Years: A Randomized Controlled Trial With Radiostereometric Analysis

BACKGROUND

A common bearing combination in total hip arthroplasty today is a metal femoral head articulating with polyethylene in the cup. Ceramic heads are thought to be more resistant to third-body damage, and have better wettability and decreased surface roughness, which taken together have been suggested to result in less polyethylene wear. The purpose of this study is to compare the initial creep deformation and follow wear pattern, using radiostereometric analysis, of ceramic and metal femoral heads that articulate with a modern highly cross-linked polyethylene cup liner.

METHODS

Fifty patients with primary osteoarthritis and scheduled for an uncemented total hip arthroplasty were randomized 1:1 to either a ceramic (BIOLOX delta) or a metal (CoCr) femoral head. The patients were followed up for 5 years with repeated radiostereometric analysis examinations (postoperatively, then at 14 days, 3, 12, 24, and 60 months), as well as a hip-specific outcome questionnaire.

RESULTS

During the first 3 months both groups showed expected creep within the liner of 0.12 mm (standard deviation 0.03) for the ceramic and 0.08 mm (standard deviation 0.02) for the metal heads. Between 3 months and 5 years there was very little wear of the liner in either group, corresponding to 0.003 mm/y for ceramic and 0.007 mm/y for metal heads. There was no difference in cup migration or clinical outcome between the groups and no cups were revised.

CONCLUSION

With the introduction of modern highly cross-linked polyethylene, the ceramic head demonstrates no superiority when it comes to either early deformation or polyethylene wear compared with the metal head.

Results of a randomized controlled trial with five-year radiostereometric analysis results of vitamin E-infused highly crosslinked versus moderately crosslinked polyethylene in reverse total hip arthroplasty

Aims

Vitamin E-infused highly crosslinked polyethylene (VEPE) has been introduced into total hip arthroplasty (THA) with the aim of further improving the wear characteristics of moderately and highly crosslinked polyethylenes (ModXLPE and HXLPE). There are few studies analyzing the outcomes of vitamin E-infused components in cemented arthroplasty, though early acetabular component migration has been reported. The aim of this study was to measure five-year polyethylene wear and acetabular component stability of a cemented VEPE acetabular component compared with a ModXLPE cemented acetabular component.

Methods

In a prospective randomized controlled trial (RCT), we assessed polyethylene wear and acetabular component stability (primary outcome) with radiostereometric analysis (RSA) in 68 patients with reverse hybrid THA at five years follow-up. Patients were randomized to either a VEPE or a ModXLPE cemented acetabular component.

Results

Mean polyethylene wear in the proximal direction was 0.17 mm (SD 0.15) for the VEPE group and 0.20 mm (SD 0.09) for the ModXLPE group (p = 0.005) at five years. Annual proximal wear rates were 0.03 mm/year (VEPE) and 0.04 mm/year (ModXLPE). Total 3D wear was 0.21 mm (SD 0.26) and 0.23 mm (SD 0.10) for the VEPE and ModXLPE groups, respectively (p = 0.009). Total 3D cup translation was 0.72 mm (SD 0.70) (VEPE) and 0.50 mm (SD 0.44) (ModXLPE) (p = 0.409).

Conclusion

At five years, there was less polyethylene wear in the VEPE group than in the ModXLPE group. Both VEPE and ModXLPE cemented components showed low annual wear rates. Component stability was similar in the two groups and remained constant up to five years. Whether these results will equate to a lower long-term revision rate is still unknown. Cite this article: Bone Joint J 2020;102-B(12):1646–1653.

Vitamin E-doped total hip arthroplasty liners show similar head penetration to highly cross-linked polyethylene at five years: a multi-arm randomized controlled trial

Aims

The most frequent indication for revision surgery in total hip arthroplasty (THA) is aseptic loosening. Aseptic loosening is associated with polyethylene liner wear, and wear may be reduced by using vitamin E-doped liners. The primary objective of this study was to compare proximal femoral head penetration into the liner between a) two cross-linked polyethylene (XLPE) liners (vitamin E-doped (vE-PE)) versus standard XLPE liners, and b) two modular femoral head diameters (32 mm and 36 mm).

Methods

Patients scheduled for a THA were randomized to receive a vE-PE or XLPE liner with a 32 mm or 36 mm metal head (four intervention groups in a 2 × 2 factorial design). Head penetration and acetabular component migration were measured using radiostereometric analysis at baseline, three, 12, 24, and 60 months postoperatively. The Harris Hip Score, University of California, Los Angeles (UCLA) Activity Score, EuroQol five-dimension questionnaire (EQ-5D), and 36-Item Short-Form Health Survey questionnaire (SF-36) were assessed at baseline, three, 12, 36, and 60 months.

Results

Of 220 screened patients, 127 were included in this study. In all, 116 received the allocated intervention, and 94 had their results analyzed at five years. Head penetration was similar between liner materials and head sizes at five years, vE-PE versus XLPE was -0.084 mm (95% confidence interval (CI) -0.173 to 0.005; p = 0.064), and 32 mm versus 36 mm was -0.020 mm (95% CI -0.110 to 0.071; p = 0.671), respectively. No differences were found in acetabular component migration or in the patient-reported outcome measures.

Conclusion

No significant difference in head penetration was found at five years between vE-PE and XLPE liners, nor between 32 mm and 36 mm heads.

Cite this article: Bone Joint J 2020;102-B(10):1303–1310.

Projections and Epidemiology of Revision Hip and Knee Arthroplasty in the United States to 2030

BACKGROUND

As the incidence of primary total joint arthroplasty rises in the United States, it is important to investigate how this will impact rates of revision arthroplasty. The purpose of this study was to analyze the incidence and future projections of revision total hip arthroplasty (rTHA) and revision total knee arthroplasty (rTKA) to 2030. Anticipating surgical volume will aid surgeons in designing protocols to efficiently and effectively perform rTHA/rTKA.

METHODS

The national inpatient sample was queried from 2002 to 2014 for all rTHA/rTKA. Using previously validated measures, Poisson and linear regression analyses were performed to project annual incidence of rTHA/rTKA to 2030, with subgroup analyses on modes of failure and age.

RESULTS

In 2014, there were 50,220 rTHAs and 72,100 rTKAs. From 2014 to 2030, rTHA incidence is projected to increase by between 43% and 70%, whereas rTKA incidence is projected to increase by between 78% and 182%. The 55-64 and 65-74 age groups increased in revision incidence during the study period, whereas 75-84 age group decreased in incidence. For rTKA, infection and aseptic loosening are the 2 most common modes of failure, whereas periprosthetic fracture and infection are most common for rTHA.

CONCLUSION

The incidence of rTHA/rTKA is projected to increase, particularly in young patients and for infection. Given the known risk factor profiles and advanced costs associated with revision arthroplasty, our projections should encourage institutions to generate revision-specific protocols to promote safe pathways for cost-effective care that is commensurate with current value-based health care trends.

LEVEL OF EVIDENCE

IV.

Migration and Wear of a Dual Mobility Acetabular Construct at 3 Years Measured by Radiostereometric Analysis

BACKGROUND

The anatomic dual mobility (ADM) acetabular component was introduced because of previously described low dislocation rates for this type of construct. The shape of the anatomic cup and the motion of polyethylene liner may have implications for acetabular cup fixation and polyethylene liner wear; therefore, the purpose of this study was to assess the migration patterns and wear rates of the ADM component using radiostereometric analysis.

METHODS

Uncemented ADM acetabular components were implanted in 27 patients. Radiostereometric analysis exams were taken at 6 follow-up visits over 3 years. Proximal translation and sagittal rotation of the cup and polyethylene total wear and wear rates were calculated. Oxford 12 Hip scores and satisfaction were recorded.

RESULTS

Mean proximal translation was below the 0.2 mm threshold at 2 years associated with acceptable long-term survivorship (0.16 mm [standard deviation {SD} 0.31] at 3 years). Mean sagittal rotation was 0.29 degrees (SD 1.03) and was greater in female subjects (P < .001). Following bedding-in, the annual wear rate was 0.02 mm/y, below the 0.1 mm/y threshold. There was no association between cup migration and polyethylene wear. Patient satisfaction at 3 years was 96%. Mean Oxford 12 Hip scores improved from 21 (SD 7) preoperatively to 43 (SD 7) 3 years postoperatively.

CONCLUSIONS

The ADM cup demonstrated stable migration at 3 years indicating low risk for aseptic loosening. Bedding-in in the first year was followed by low annual wear rates. These finding suggest no increased risk of the dual mobility and anatomic design on fixation or wear.

Low failure rate at short term for 40 mm heads and second generation triple annealed HCLPE liners in hybrid hip replacements

INTRODUCTION

40 mm large diameter heads offer the advantages of lesser dislocation rates and better stability while highly cross linked polyethylene have lower wear rates than ultra high molecular weight polyethylene. Studies of the survivorship of 40 mm heads in hybrid hip replacements with Exeter stem and second generation highly cross linked polyethylene are limited. The purpose of the study is to report the short term of survivorship of the large diameter heads (40 mm) with Exeter stem with the secondary aim being the survival analysis of the thinnest second generation highly cross linked polyethylene.

METHODS

Retrospective case series of survivorship of patients with hybrid hip replacements of Exeter stems with 40 mm heads articulating with second generation triple annealed highly cross linked polyethylene liner on a uncemented acetabular shell was performed. As a subset, survival of thinnest second generation highly cross linked polyethylene survival (3.8 mm) at short term was assessed. Survival of the implants was confirmed from the hospital records and National joint registry as of 2015. Revision for any cause was taken as end point.

RESULTS

324 hybrid hip replacements with 40 mm heads had been performed for primary hip osteoarthritis. Of the 324 hip replacements, 154 hip replacements had thinnest second generation highly cross linked polyethylene (3.8 mm). Two patients had revision of components, one for periprosthetic fracture and one for deep infection. Mean age of the patients was 70.5 years (range 42-88 years, median 71, SD 8.3 years). None of the patients had revision due to trunion wear or loosening of components. The overall 5-year implant survival probability of hips with 40 mm heads was 99.4% (95% CI 98 to 100%) while the subset group of hip replacements with thinnest second generation highly cross linked polyethylene (3.8 mm) had 5-year implant survival probability of 99.3% (95% CI 97.1 to 100%).

CONCLUSION

Short term survivorship does not show significant evidence of early failure or higher rate of revision in our series of hybrid hip replacements with large diameter heads and second generation triple annealed highly cross linked polyethylene. Dislocation rate at the short term is none. Results from this series have to be carefully interpreted due to the relatively short follow up but so far results are encouraging. Long term follow up is required to conclude whether there is early or higher rate of failure. It is our intention to follow up this cohort and further publish our results at longer term.

Recent updates for biomaterials used in total hip arthroplasty

Background

Total hip arthroplasty (THA) is probably one of the most successful surgical interventions performed in medicine. Through the revolution of hip arthroplasty by principles of low friction arthroplasty was introduced by Sir John Charnley in 1960s. Thereafter, new bearing materials, fixation methods, and new designs has been improved. The main concern regarding failure of THA has been the biological response to particulate polyethylene debris generated by conventional metal on polyethylene bearing surfaces leading to osteolysis and aseptic loosening of the prosthesis. To resolve these problems, the materials of the modern THA were developed since then.

Methods

A literature search strategy was conducted using various search terms in PUBMED. The highest quality articles that met the inclusion criteria and best answered the topics of focus of this review were selected. Key search terms included ‘total hip arthroplasty’, ‘biomaterials’, ‘stainless steel’, ‘cobalt-chromium’, ‘titanium’, ‘polyethylene’, and ‘ceramic’.

Results

The initial search retrieved 6921 articles. Thirty-two articles were selected and used in the review.

Conclusion

This article introduces biomaterials used in THA and discusses various bearing materials in currentclinical use in THA as well as the newer biomaterials which may even further decrease wear and improve THA survivorship.

Femoral-Acetabular Mating: The Effect of Femoral and Combined Anteversion on Cross-Linked Polyethylene Wear

BACKGROUND

Cross-linked polyethylene (XLPE) has generally low rates of wear and osteolysis at 10 years, but component position may become important with longer follow-up. At 5-13 years, neither acetabular component lateral opening angle nor version were significantly correlated to wear. In the present study, we analyzed the effects of femoral anteversion and combined anteversion on XLPE wear.

METHODS

Forty-two well-functioning primary total hip arthroplasties in 36 patients, performed by a single surgeon via a posterior approach, were followed for a minimum of 5 years (mean, 7.1 years; range, 5.0-10.3). All hips had a modular, XLPE liner with a ≥36-mm bearing. Femoral anteversion was measured on the modified Budin view. Wear was measured on radiographs using a validated, computer-assisted, edge-detection-based algorithm. The mean lateral opening angle was 40.4° (range, 22.6°-50.3°). The mean acetabular version was 19.1° (range, 11.3°-27.5°). Neither of these variables was significantly correlated to wear. Effects of femoral anteversion and combined anteversion on XLPE wear were assessed using linear and polynomial regression analysis.

RESULTS

Femoral anteversion (mean, 18.4°; range, 6.8°-30.7°) was significantly correlated to linear wear (mean, 0.06 mm/y; range, 0-0.16), showing an inverse parabolic relationship with the least wear occurring at 18.2° (P = .02). Combined anteversion (mean, 37.2°; range, 21.8°-54.3°) showed a similar significant relationship with the least wear at 38.1° (P < .001). Based on regression, combined anteversion between 24.6° and 50.4° resulted in linear wear rates less than 0.1 mm/y.

CONCLUSION

To the authors' knowledge, this is the first study to identify femoral anteversion as an independent factor influencing XLPE wear, with least wear occurring around 18°. At 5-10 years, average linear wear of XLPE is below 0.1 mm/y over a 25°-50° range of combined anteversion, with the least wear around 38°. Femoral-acetabular mating is a product of both components. Femoral component version and combined anteversion had a greater effect on wear than acetabular component lateral opening angle. Additional studies are warranted, but these results indicate that the sensitivity of wear studies is increased with version assessments.

Cross-Linked Polyethylene for Total Hip Arthroplasty Markedly Reduces Revision Surgery at 16 Years

BACKGROUND

Total hip arthroplasty (THA) is an effective operation for the management of end-stage hip osteoarthritis, but long-term success can be limited by wear of the polyethylene bearing surface. Cross-linking conventional polyethylene has resulted in lower wear rates and a reduction in bone lysis in both laboratory and clinical studies. The aim of this study was to compare the rates of revision between cross-linked polyethylene (XLPE) and conventional non-cross-linked polyethylene (CPE) at 16 years after THAs performed for the treatment of osteoarthritis.

METHODS

We performed an observational study of data, from a national registry, on all patients who underwent THA for osteoarthritis in Australia from 1999 through December 31, 2016. The outcomes of THAs performed with CPE were compared with those of THAs performed with XLPE, along with an analysis of the effect of age, sex, femoral head size, the method of acetabular and femoral component fixation, and the reasons and types of revision. The principal outcome measure was the time to the first revision, determined using Kaplan-Meier estimates of survivorship.

RESULTS

CPE was used in 41,171 procedures, and XLPE was used in 199,131. The mean ages of the men and women treated with CPE were 70.0 years (standard deviation [SD] = 9.9 years) and 72.5 years (SD = 9.7 years), respectively, whereas the men and women who received XLPE were slightly younger (mean age, 68.6 years [SD = 10.3 years] and 70.7 years [SD = 9.9 years], respectively. XLPE was associated with a lower rate of revision than CPE at 6 months, and this difference became more apparent with time. The 16-year cumulative percentage of revisions of the primary THAs was 11.7% (95% confidence interval [CI] = 11.1% to 12.3%]) in the CPE group and 6.2% (95% CI = 5.7% to 6.7%) in the XLPE group. The hazard ratio at 9 years was 3.02 (p = 0.001).

CONCLUSIONS

The use of XLPE has resulted in a significant reduction in the rate of revision at 16 years following THA for osteoarthritis. This evidence suggests that the longevity of THA is likely to be improved, which may enable younger patients to undergo surgery, confident of a reduced need for revision in the long term.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Total hip arthroplasty: Survival and modes of failure

Total hip arthroplasty (THA) is a very satisfactory surgical procedure for end-stage hip disorders.

Implant modifications, such as large femoral heads to improve stability, porous metals to enhance fixation and alternative bearings to improve wear, have been introduced over the last decade in order to decrease the rate of early and late failures.

There is a changing pattern of THA failure modes.

The relationship between failure modes and patient-related factors, and the time and type of revision are important for understanding and preventing short and late failure of implants.

The early adoption of innovations in either technique or implant design may lead to an increased risk of early failure.

Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170068

Higher UHMWPE wear-rate in cementless compared with cemented cups with the Saturne® Dual-Mobility acetabular system

INTRODUCTION

Dual mobility (DM) total hip arthroplasty (THA) may reduce dislocation risk, but might increase the risk of high polyethylene (PE) wear due to double wearing surfaces.

METHODS

127 patients (97 female) with 129 hips operated with THA after displaced femoral neck fracture FNF between 2005 and 2011, were seen for a cross-sectional clinical follow-up. Acetabular components were Saturne® DM cups with 28mm chrome-cobalt heads in UHMWPE. Cementless cups (n = 73) were hydroxyapatite coated. Radiographs were obtained for analysis of cup placement, 2D polyethylene wear and wear-rate (PolyWare 3D), and further radiological evaluation. Activity measurements included Timed Up and Go test (TUG) and walking distance from Harris Hip Score (HHS).

RESULTS

At a mean follow-up of 2.83 (1.0-7.7) years the mean wear was 0.82 mm (range 0.17-4.51, SD 0.50), and the wear-rate was 0.37 mm (range 0.06-1.90, SD 0.29). Wear-rate of 0.43 mm/year (SD 0.30) in cementless cups was higher (p = 0.004) than 0.30 mm/year (SD 0.27) in cemented cups. Mean age at time of surgery was 75.1 years (range 30-95). There was no correlation between age at time of surgery and wear (p = 0.56). There was no correlation between cup inclination and wear-rate (p = 0.35). TUG was mean 13.4 seconds (range 4.5-30.1) and correlated with wear rate (p = 0.03).

CONCLUSIONS

At short term follow-up, the mean wear-rate in old and low demand patients was high, correlated to activity, and was above the generally accepted osteolysis threshold (0.1 mm/yr.). Cementless HA-coated cups had higher wear-rate than cemented cups.

Creep and Wear in Vitamin E-Infused Highly Cross-Linked Polyethylene Cups for Total Hip Arthroplasty: A Prospective Randomized Controlled Trial

BACKGROUND

Aseptic loosening, the most common indication for revision surgery in total hip arthroplasty, can result from osteolysis caused by polyethylene (PE) wear particles. PE wear is increased by age-related oxidation of PE and free radicals emerging during irradiation cross-linking. Diffusion of vitamin E into PE stabilizes free radicals to maintain the biomechanical properties of PE. The purpose of this study was to determine whether vitamin E-infused highly cross-linked PE cups could reduce wear rates.

METHODS

We performed a prospective randomized controlled trial, in which 62 patients were allocated to 2 groups: a study group that received a vitamin E-infused highly cross-linked PE (HXLPE/VitE) cup and a control group that received an ultra-high molecular weight PE (UHMWPE) cup. Using radiostereometric analysis, we measured the penetration of the femoral head into the cup 7 days after surgery (baseline) and then again at 6 months and at 1, 2, and 3 years later.

RESULTS

Baseline variables did not differ significantly between the groups. At 1, 2, and 3 years after surgery, the HXLPE/VitE cup showed significantly less cumulative penetration (creep and wear) than the UHMWPE cup (p = 0.004, p < 0.0001, and p < 0.0001, respectively). The cumulative penetration after 3 years was 0.200 mm for the HXLPE/VitE cup versus 0.317 mm for the UHMWPE cup (p < 0.0001). From 1 to 3 years after surgery, after creep had stabilized and further penetration was mainly due to wear, the mean penetration increased only 0.04 mm in the HXLPE/VitE cup and 0.116 mm in the UHMWPE cup.

CONCLUSIONS

Our results confirm that wear rates over the first 3 years following surgery were lower in HXLPE/VitE cups than in UHMWPE cups. This suggests that HXLPE/VitE cups may prevent osteolysis, implant loosening, and eventually revision surgery. Long-term follow-up data continue to be collected to confirm these findings.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Surface modifications and oxidative degradation in MPC-grafted highly cross-linked polyethylene liners retrieved from short-term total hip arthroplasty

Highly cross-linked polyethylene (HXLPE) hip liners grafted with 2-methacryloyloxyethyl phosphorylcholine (MPC) on their bearing surfaces have recently been commercialized as components of a new generation of artificial hip joints, while improvements in wear resistance and biocompatibility were reported based on in vitro studies. The present study aimed at evaluating the surface modification and oxidative degradation in short-term retrieved MPC-grafted liners by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) with attenuated total reflection (ATR) equipment and Raman spectroscopy. In none of 3 samples of retrieved MPC-grafted liners, detectable MPC graft remained on the bearing surfaces although 2 samples yet contained remains of MPC polymer in their rim zone. These results revealed that the MPC polymer might have quickly disappeared from the bearing surface under in vivo loading, which is more severe than the in vitro one. Furthermore, a detectable oxidation index (OI) value (>0.1) was not only observed in any zone of any sample investigated, but also in the rim zones of Samples 1 and 2, which surprisingly experienced the most remarkable increase in OI value detected in this study. We thus confirmed that: (i) annealing of HXLPE cannot completely remove free radicals; (ii) the MPC graft has no beneficial effect in protecting HXLPE against oxidation and wear; and, (iii) lipid absorption occurred even in the rim zone where the MPC layer remained. Based on these evidences we consider that the declaimed advanced MPC technology is not a suitable one to elongate the in vivo lifetime of hip joints.

STATEMENT OF SIGNIFICANCE

Several studies reported that highly crosslinked polyethylene (HXLPE) have resulted in reduced wear in total hip arthroplasty. Beyond those studies, HXLPE hip liners grafted with 2-methacryloyloxyethyl phosphorylcholine (MPC) on their bearing surface were extensively studied in vitro and then commercialized as a new generation of artificial hip joints. The present study reports for the first time results about the evaluation of surface modification and oxidative degradation in retrieved the MPC grafted liners. The findings of this investigation clearly show that the MPC layer has been peeled off on the bearing surface of the liner main wear zone although the MPC layer remained on the surface of the rim zones. Furthermore, we assessed the microstructural modifications and the oxidation drifts that occurred in vivo in the hip joints despite the presence of the MPC layer.

Wear rate and medium-term survival of a cemented, moderately cross-linked polyethylene acetabular prosthesis

INTRODUCTION

The moderately cross-linked Depuy Marathon® cemented acetabular component was introduced into the UK in 2007. The wear rate for the previously introduced Marathon® uncemented acetabular component has been reported to range from 0.06 to 0.01 mm/year. The aim of this study was to present the medium-term results and wear rate of the Marathon® cemented prosthesis used in primary total hip arthroplasty.

METHODS

103 Marathon® cemented acetabular components were implanted between 2008 and 2009 in primary arthroplasty, who were eligible for this study. All patients received a metal 28-mm head. Mean age was 68 years (range 27-87). Mean clinical follow-up was 55 months (range 50-61). Mean radiological follow-up was 46 months (range 24-57). Wear was calculated on AP radiographs using computer-assisted uni-radiographic technique.

RESULTS

The mean wear was 0.37 mm (range 0.0-0.78 mm). The wear rate was calculated as 0.03 mm/year (95% confidence interval 0.02-0.06). Postoperative complications included deep vein thrombosis (2%) and dislocation (0.8%); there were no deep infections. There were no revisions for failure of the Marathon® cemented acetabular component.

CONCLUSIONS

The Marathon® cemented acetabular component demonstrates satisfactory wear rates and survivorship at medium-term follow-up.

Higher UHMWPE wear-rate in cementless compared with cemented cups with the Saturne® Dual-Mobility acetabular system

INTRODUCTION

Dual mobility (DM) total hip arthroplasty (THA) may reduce dislocation risk, but might increase the risk of high polyethylene (PE) wear due to double wearing surfaces.

METHODS

127 patients (97 female) with 129 hips operated with THA after displaced femoral neck fracture FNF between 2005 and 2011, were seen for a cross-sectional clinical follow-up. Acetabular components were Saturne® DM cups with 28mm chrome-cobalt heads in UHMWPE. Cementless cups (n = 73) were hydroxyapatite coated. Radiographs were obtained for analysis of cup placement, 2D polyethylene wear and wear-rate (PolyWare 3D), and further radiological evaluation. Activity measurements included Timed Up and Go test (TUG) and walking distance from Harris Hip Score (HHS).

RESULTS

At a mean follow-up of 2.83 (1.0-7.7) years the mean wear was 0.82 mm (range 0.17-4.51, SD 0.50), and the wear-rate was 0.37 mm (range 0.06-1.90, SD 0.29). Wear-rate of 0.43 mm/year (SD 0.30) in cementless cups was higher (p = 0.004) than 0.30 mm/year (SD 0.27) in cemented cups. Mean age at time of surgery was 75.1 years (range 30-95). There was no correlation between age at time of surgery and wear (p = 0.56). There was no correlation between cup inclination and wear-rate (p = 0.35). TUG was mean 13.4 seconds (range 4.5-30.1) and correlated with wear rate (p = 0.03).

CONCLUSIONS

At short term follow-up, the mean wear-rate in old and low demand patients was high, correlated to activity, and was above the generally accepted osteolysis threshold (0.1 mm/yr.). Cementless HA-coated cups had higher wear-rate than cemented cups.

Vitamin E diffused highly cross-linked polyethylene in total hip arthroplasty at five years: a randomised controlled trial using radiostereometric analysis

AIMS

The objective of this five-year prospective, blinded, randomised controlled trial (RCT) was to compare femoral head penetration into a vitamin E diffused highly cross-linked polyethylene (HXLPE) liner with penetration into a medium cross-linked polyethylene control liner using radiostereometric analysis.

PATIENTS AND METHODS

Patients scheduled for total hip arthroplasty (THA) were randomised to receive either the study E1 (32 patients) or the control ArComXL polyethylene (35 patients). The median age (range) of the overall cohort was 66 years (40 to 76).

RESULTS

The five-year median (interquartile range) proximal femoral head penetration into the E1 was -0.05 mm (-0.13 to -0.02) and 0.07 mm (-0.03 to 0.16) for ArComXL. At three and five years, the penetration was significantly greater in the ArComXL group compared with the E1 group (p = 0.029 and p = 0.019, respectively). All patient-reported outcomes (PROs) improved significantly from the pre-operative interval compared with those at one year, and remained favourable at five years. There were no differences between the two groups at any interval.

CONCLUSION

The five-year results showed that E1 polyethylene does not wear more than the control, ArComXL. This is the longest-term RCT comparing the wear performance and clinical outcome of vitamin E diffused HXLPE with a previous generation of medium cross-linked polyethylene. Cite this article: Bone Joint J 2017;99-B:577-84.

Ultra-High Molecular Weight Polyethylene: Influence of the Chemical, Physical and Mechanical Properties on the Wear Behavior. A Review

Ultra-high molecular weight polyethylene (UHMWPE) is the most common bearing material in total joint arthroplasty due to its unique combination of superior mechanical properties and wear resistance over other polymers. A great deal of research in recent decades has focused on further improving its performances, in order to provide durable implants in young and active patients. From "historical", gamma-air sterilized polyethylenes, to the so-called first and second generation of highly crosslinked materials, a variety of different formulations have progressively appeared in the market. This paper reviews the structure-properties relationship of these materials, with a particular emphasis on the in vitro and in vivo wear performances, through an analysis of the existing literature.

Investigation of imaging magnification in radiostereometric analysis

Radiostereometric analysis is a highly accurate imaging technique. A recent advance in radiostereometric analysis is the use of flat panel digital radiography, which provides the opportunity for quick analysis using radiostereometric analysis. However, such a setup is expensive. Using large cassettes for small joints could minimize the cost. In this article, we investigated the influence of cassette size for small joint examinations with a biplanar radiostereometric analysis setup. Our results indicated that there is no significant difference in the precision when using large cassettes over small cassettes, whether or not imaging magnification is applied.

Highly cross-linked polyethylene improves wear and mid-term failure rates for young total hip arthroplasty patients

We compared clinical outcomes and polyethylene wear for 2 young primary THA patient cohorts (<50 years of age) at mid-term follow-up. In total, 72 patients (84 hips) received a coventional polyethylene liner (CPE) and 84 patients (89 hips) received a highly cross-linked polyethylene liner (HXLPE). Mean Harris Hip Score improved to 81 points for both groups. UCLA activity scores were higher for HXLPE patients (6.0 vs 5.3, p = 0.03), with lower mean linear wear (0.02 vs 0.13 mm/year, p<0.001) and lower mean volumetric wear (75.1 vs 229.8 mm3, p<0.001) at an average of 70 months follow-up. No HXLPE patient required revision for wear related concerns, compared to 5 CPE patients with revision for aseptic loosening or impending radiographic failure (0% vs 5.9%, p = 0.02). HXLPE is associated with reduced wear among young, active THA patients without increased risk of early mechanical failure.

Validation of a protocol based on Raman and infrared spectroscopies to nondestructively estimate the oxidative degradation of UHMWPE used in total joint arthroplasty

As a matter of fact, the in vivo oxidative degradation of highly cross-linked polyethylene (HXLPE) still remains one of the limiting factors that affect the long term survivorship of joint replacements. Recent studies clearly pointed out that also the new generation of highly cross-linked and remelted polyethylene components in total hip and knee replacement underwent unexpected oxidation after 5-10years of implantation. The standard methodology to investigate the oxidation of polyethylene (PE) relies on the use of infrared spectroscopy, which, if from one hand is a reliable technique for the detection of oxidized species containing carbonyl group, on the other hand it is not capable of discriminating the fraction of carboxyl acids that is responsible for chain scission and subsequent deterioration of the mechanical properties of the polymer. In the present study we validate a new protocol based on Raman spectroscopy, which is suitable on assessing the structural degradation of polyethylene induced by oxidation. Following in vitro accelerated aging experiments, the oxidation index (OI) of different commercially available HXLPEs, as calculated by infrared spectroscopy according to ASTM standard, has been univocally correlated to the most severe variation of crystalline phase (αc), as calculated by Raman spectroscopy. In each material, locations with equal values of OI showed different degree of recrystallization induced by chain scission, confirming that infrared spectroscopy might overestimate the effective mechanical degradation of the polymer. In addition, as compared to the standards based on infrared spectroscopy, this new method of assessing oxidation enables to investigate the degradation occurring on the original surface of HXLPE components, due to the nondestructive nature of Raman spectroscopy and its high spatial resolution.

STATEMENT OF SIGNIFICANCE

In the present study we validate a new protocol based on Raman spectroscopy, which is suitable on assessing the structural degradation of polyethylene induced by oxidation. In fact, the standard methodology to investigate the oxidation in polyethylene relies on the use of infrared spectroscopy, which is capable of detecting the presence of oxidized species containing carbonyl group, the main products of oxidation in polyolefins. If from one hand this technique enables quantitative analysis of oxidation, on the other hand it is not capable of discriminating the fraction of species with carbonyl groups responsible for the chain scission. In fact, esters, ketones and carboxyl acids are products of oxidation with carbonyl groups commonly formed on polyethylene at the end of the oxidative cascade initiated by the presence of free radicals, but only the latter are responsible for the chain scission and the subsequent deterioration of the mechanical properties. The oxidation index as obtained according to the ASTM standards is not univocally correlated to a certain degree of mechanical deterioration, but, in simple words, two retrievals with the same amount of carbonyl groups might have had different degradation of the mechanical properties. Recrystallization is a direct consequence of the reduction of molecular weight that occurs after chain scission. Raman spectroscopy (RS) is a viable non-destructive method to assess the fraction of crystalline phase in polyethylene and, due to its high spatial resolution, is perfectly suitable to analyze the microstructural modification at the mesoscopic scale, where the effects of oxidation manifest themselves. The aim of the present paper is twofold: i) to compare the microstructural modifications caused by in vitro oxidation on 5 different types of polyethylene currently available on the market of joint replacements; ii) to establish a protocol based on the comparative analysis of IR and RS results to obtain a phenomenological correlation capable to judge the mechanical deterioration of the material induced by the oxidative degradation.

Low wear, high stability - promises of success in a moderately cross-linked cup?

PURPOSE

Cross-linking has proven effective in reducing polyethylene wear in total hip replacements. However, increasing the amount of cross-links will impair other mechanical properties of the polyethylene. The optimal threshold of crosslinking has still not been established. This led to the development of a moderately cross-linked (5 Mrad) cemented cup in which wear and stability is yet to be determined.

METHODS

A total of, 70 hips were included in this case series on the cemented Marathon® cup. Mean age of the patients was 78 years (SD 15). We measured wear and migration by radiostereometry at 3, 12 and 24 months.

RESULTS

The proximal wear rate estimate between 3 to 24 months was 0.036 mm/year, and a total proximal wear estimate at 2 years of 0.11 mm (95% CI 0.09-0.14). Translations and rotations along the 3 cardinal axes were all at or below the precision limit, and less than what is believed to be predictive of later loosening, namely 0.2-1 mm for proximal migration. The cups remained stable after the initial "bedding in" that occurred during the first 3 months.

CONCLUSIONS

Our results indicate that moderate cross-linking (5Mrad) yields low wear and high stability in this specific acetabular cup, comparable to other cups with higher cross-linking.

A Novel Method for Measuring Polyethylene Hip Liner Wear Using a Coordinate Measuring Machine and a Dual Stylus Probe

Ex vivo high-resolution measurement of highly crosslinked (HXL) polyethylene hip liner wear is necessary to characterize the in vivo performance of these polymers that exhibit increased wear resistance. Current studies focus on using a coordinate measuring machine (CMM) to acquire data representing the bearing surface(s) of HXL hip liners and use this data to determine linear and volumetric wear. However, these current techniques are subject to error in both data acquisition and data analysis. The purpose of this study was to identify these sources of error and present a novel method for HXL wear measurement that minimizes these contributions to error: our novel methods use a CMM to measure both the articular and backside surfaces of HXL hip liners for subsequent data analysis in Geomagic Control and matlab. Our method involves a vertical orientation of the hip liner to enable one CMM scan of both sides of the hip liner. This method minimizes identified sources of error and proves to be an effective approach for data acquisition of HXL hip liner wear. We also find that our data analysis technique of calculating changes in wall thicknesses is effective in accounting for errors associated with data analysis. Validation of this technique occurred via measurement of two never-implanted HXL hip liners of different sizes (28 mm and 32 mm). In comparing the 32 mm hip liner to its corresponding computer-aided design (CAD) model, we found that our data acquisition technique led to a 0.0019 mm discrepancy between the scanned liner and its CAD model in measured thickness at the pole. We calculated 0.0588 mm and 0.0800 of linear wear for the 28 mm and 32 mm hip liners, respectively, based on our data analysis algorithm. We hypothesize that these reported linear wear values of the never-implanted hip liners are due to machining tolerances of the hip liners themselves.

Total hip replacement and surface replacement for the treatment of pain and disability resulting from end-stage arthritis of the hip (review of technology appraisal guidance 2 and 44): systematic review and economic evaluation

BACKGROUND

Total hip replacement (THR) involves the replacement of a damaged hip joint with an artificial hip prosthesis. Resurfacing arthroplasty (RS) involves replacement of the joint surface of the femoral head with a metal surface covering.

OBJECTIVES

To undertake clinical effectiveness and cost-effectiveness analysis of different types of THR and RS for the treatment of pain and disability in people with end-stage arthritis of the hip, in particular to compare the clinical effectiveness and cost-effectiveness of (1) different types of primary THR and RS for people in whom both procedures are suitable and (2) different types of primary THR for people who are not suitable for hip RS.

DATA SOURCES

Electronic databases including MEDLINE, EMBASE, The Cochrane Library, Current Controlled Trials and UK Clinical Research Network (UKCRN) Portfolio Database were searched in December 2012, with searches limited to publications from 2008 and sample sizes of ≥ 100 participants. Reference lists and websites of manufacturers and professional organisations were also screened.

REVIEW METHODS

Systematic reviews of the literature were undertaken to appraise the clinical effectiveness and cost-effectiveness of different types of THR and RS for people with end-stage arthritis of the hip. Included randomised controlled trials (RCTs) and systematic reviews were data extracted and risk of bias and methodological quality were independently assessed by two reviewers using the Cochrane Collaboration risk of bias tool and the Assessment of Multiple Systematic Reviews (AMSTAR) tool. A Markov multistate model was developed for the economic evaluation of the technologies. Sensitivity analyses stratified by sex and controlled for age were carried out to assess the robustness of the results.

RESULTS

A total of 2469 records were screened of which 37 were included, representing 16 RCTs and eight systematic reviews. The mean post-THR Harris Hip Score measured at different follow-up times (from 6 months to 10 years) did not differ between THR groups, including between cross-linked polyethylene and traditional polyethylene cup liners (pooled mean difference 2.29, 95% confidence interval -0.88 to 5.45). Five systematic reviews reported evidence on different types of THR (cemented vs. cementless cup fixation and implant articulation materials) but these reviews were inconclusive. Eleven cost-effectiveness studies were included; four provided relevant cost and utility data for the model. Thirty registry studies were included, with no studies reporting better implant survival for RS than for all types of THR. For all analyses, mean costs for RS were higher than those for THR and mean quality-adjusted life-years (QALYs) were lower. The incremental cost-effectiveness ratio for RS was dominated by THR, that is, THR was cheaper and more effective than RS (for a lifetime horizon in the base-case analysis, the incremental cost of RS was £11,284 and the incremental QALYs were -0.0879). For all age and sex groups RS remained clearly dominated by THR. Cost-effectiveness acceptability curves showed that, for all patients, THR was almost 100% cost-effective at any willingness-to-pay level. There were age and sex differences in the populations with different types of THR and variations in revision rates (from 1.6% to 3.5% at 9 years). For the base-case analysis, for all age and sex groups and a lifetime horizon, mean costs for category E (cemented components with a polyethylene-on-ceramic articulation) were slightly lower and mean QALYs for category E were slightly higher than those for all other THR categories in both deterministic and probabilistic analyses. Hence, category E dominated the other four categories. Sensitivity analysis using an age- and sex-adjusted log-normal model demonstrated that, over a lifetime horizon and at a willingness-to-pay threshold of £20,000 per QALY, categories A and E were equally likely (50%) to be cost-effective.

LIMITATIONS

A large proportion of the included studies were inconclusive because of poor reporting, missing data, inconsistent results and/or great uncertainty in the treatment effect estimates. This warrants cautious interpretation of the findings. The evidence on complications was scarce, which may be because of the absence or rarity of these events or because of under-reporting. The poor reporting meant that it was not possible to explore contextual factors that might have influenced study results and also reduced the applicability of the findings to routine clinical practice in the UK. The scope of the review was limited to evidence published in English in 2008 or later, which could be interpreted as a weakness; however, systematic reviews would provide summary evidence for studies published before 2008.

CONCLUSIONS

Compared with THR, revision rates for RS were higher, mean costs for RS were higher and mean QALYs gained were lower; RS was dominated by THR. Similar results were obtained in the deterministic and probabilistic analyses and for all age and sex groups THR was almost 100% cost-effective at any willingness-to-pay level. Revision rates for all types of THR were low. Category A THR (cemented components with a polyethylene-on-metal articulation) was more cost-effective for older age groups. However, across all age-sex groups combined, the mean cost for category E THR (cemented components with a polyethylene-on-ceramic articulation) was slightly lower and the mean QALYs gained were slightly higher. Category E therefore dominated the other four categories. Certain types of THR appeared to confer some benefit, including larger femoral head sizes, use of a cemented cup, use of a cross-linked polyethylene cup liner and a ceramic-on-ceramic as opposed to a metal-on-polyethylene articulation. Further RCTs with long-term follow-up are needed.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013003924.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Femoral Head Penetration of Vitamin E-Infused Highly Cross-Linked Polyethylene Liners: A Randomized Radiostereometric Study of Seventy Hips Followed for Two Years

BACKGROUND

Highly cross-linked polyethylene infused with vitamin E (E-poly) was developed to increase oxidative resistance without affecting mechanical properties. We evaluated this type of polyethylene in a randomized clinical study that used radiostereometric analysis. Our objective was to compare the early-term femoral head penetration of an E-poly liner with that of a heat-treated polyethylene liner, ArComXL. We hypothesized that the clinical outcome at two years following total hip arthroplasty would be unaffected by the choice of polyethylene.

METHODS

In this prospective study, sixty-one patients (seventy hips) with noninflammatory hip osteoarthritis and a median age of fifty-eight years were randomized to receive either an implant with an E-Poly or a heat-treated highly cross-linked polyethylene liner. The patients were followed for two years and evaluated at three time points (three months, one year, and two years).

RESULTS

The median proximal penetration in the E-poly group increased from 0.04 mm at three months to 0.06 mm at two years of follow-up. Corresponding values for the ArComXL group were 0.03 mm and 0.10 mm. In both groups, significantly increased penetration was observed between three months and two years (E-poly, p = 0.02; ArComXL, p < 0.001), but between one and two years, the increase was significant only in the control group (E-poly, p = 0.23; ArComXL, p = 0.002).

CONCLUSIONS

The femoral head penetration of E-poly was very low at two years. Whether the increase observed between three months and two years was caused by creep, deformation, wear, or a combination of these cannot be determined by our study. There were no significant differences observed in femoral head penetration rates between E-poly and ArComXL. Currently, the theoretical advantages of E-poly remain to be confirmed.

Thin-Walled Cross-Linked Acetabular Liners Need Not Exhibit Reduced Locking Strength

Use of larger diameter femoral heads has emerged as a promising strategy to reduce the risk of dislocation after total hip arthroplasty, but thinning the walls of cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) acetabular liners to accommodate these larger heads may compromise the locking mechanism of the liner. The purpose of this study was to test the mechanical integrity of the locking mechanism in cross-linked and re-melted UHMWPE acetabular components with reduced wall thickness. The locking mechanism of cross-linked (100 kGy/re-melted) acetabular liners in sizes 50/28, 50/36, and 52/36 mm of 1 design was evaluated by lever-out tests and torsion tests. Torsion tests were performed at 2 angles to isolate the liner's locking tabs independent of the contribution of its central post. Lever-out testing demonstrated nominally reduced failure strength in 50/36-mm liners (13.3 N · m) compared with 50/28-mm liners (12.3 N · m; P=.0502), whereas the lever-out strength of 52/36-mm liners was 12.2±0.94 N · m. Failure torques were similar between 50/28- and 50/36-mm liners at 45° and 90°, but the failure torque of size 52/36-mm liners was significantly higher at each angle. The use of larger diameter femoral heads does not compromise the locking mechanism of thinned MicroSeal (Signal Medical Corp, Marysville, Michigan) acetabular liners. Use of a cross-linked UHMWPE acetabular liner, with a locking mechanism that is not compromised when the liner is thinned to a thickness of at least 2.86 mm, appears to be a biomechanically sound construct when articulated with large diameter femoral heads.

In-vivo degradation of middle-term highly cross-linked and remelted polyethylene cups: Modification induced by creep, wear and oxidation

In this study Raman (RS) and Fourier Transform Infrared (FT-IR) spectroscopic techniques were exploited to study 11 retrieved liners made of remelted highly cross-linked polyethylene (HXLPE), with the intent to elucidate their in-vivo mechanical and chemical degradation. The retrievals had different follow-ups, ranging from a few months to 7 years of implantation time and belong to the first generation of highly cross-linked and remelted polyethylene clinically introduced in 1999, but still currently implanted. Raman assessments enabled to discriminate contributes of wear and creep on the total reduction of thickness in different locations of the cup. According to our results, although the most of the viscoelastic deformation occurred during the first year (bedding-in period), it progressed during the steady wear state up to 7 years with much lower but not negligible rate. Overall, the wear rate of this remelted HXLPE liner was low. Preliminary analysis on microtomed sections of the liners after in-vivo and in-vitro accelerated aging (ASTM F2003-02) enabled to obtain a phenomenological correlation between the oxidation index (OI) and the amount of orthorhombic phase fraction (αc), which can be easily non-destructively measured by RS. Profiles of αc obtained from different locations of the cups were used to judge the oxidative degradation of the 11 retrievals, considering also the ex-vivo time elapsed from the revision surgery to the spectroscopic experiments. Low but measurable level of oxidation was detected in all the short-term retrievals, while in the middle-term samples peaks of OI were observed in the subsurface (up to OI=4.5), presumably induced by the combined effect of mechanical stress, lipid absorption and prolonged ex-vivo shelf-aging in air.

Three Year RSA Evaluation of Vitamin E Diffused Highly Cross-linked Polyethylene Liners and Cup Stability

Vitamin E diffusion into highly cross-linked polyethylene (E-XLPE) is a method for enhancing oxidative stability of acetabular liners. The purpose of this study was to evaluate in vivo penetration of E-XLPE using radiostereometric analysis (RSA). Eighty-four hips were recruited into a prospective 10-year RSA. This is the first evaluation of the multicenter cohort after 3-years. All patients received E-XLPE liners (E1, Biomet) and porous-titanium coated cups (Regenerex, Biomet). There was no difference (P=0.450) in median femoral head penetration into the E-XLPE liners at 3-years comparing cobalt-chrome heads (-0.028mm; inter-quartile range (IQR) - 0.065 to 0.047) with ceramic heads (-0.043mm, IQR - 0.143to0.042). The 3-year follow-up indicates minimal E-XLPE liner penetration regardless of head material and minimal early cup movement.

Durability of highly cross-linked polyethylene in total hip and total knee arthroplasty

This article reviews the history of the development of highly cross-linked polyethylene and provides an in-depth review of the clinical results regarding the durability of highly cross-linked polyethylene (HXLPE) used in total hip arthroplasty (THA) and total knee arthroplasty (TKA). The use of polyethylene as a bearing surface has contributed to the success of THA and TKA; however, polyethylene wear and osteolysis can lead to failure. Ongoing clinical and retrieval studies are required to analyze outcomes at longer-term follow-up.

Five-year comparison of wear using oxidised zirconium and cobalt–chrome femoral heads in total hip arthroplasty

Oxidised zirconium (OxZi) has been developed as an alternative bearing surface for femoral heads in total hip arthroplasty (THA). This study has investigated polyethylene wear, functional outcomes and complications, comparing OxZi and cobalt–chrome (CoCr) as part of a three-arm, multicentre randomised controlled trial. Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and highly cross-linked polyethylene (XLPE) liner; Group B received an OxZi femoral head and XLPE liner; Group C received an OxZi femoral head and ultra-high molecular weight polyethylene (UHMWPE) liner. At five years, 368 patients had no statistically significant differences in short-form-36 (p = 0.176 mental, p = 0.756 physical), Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.847), pain scores (p = 0.458) or complications. The mean rate of linear wear was 0.028 mm/year (standard deviation (sd) 0.010) for Group A, 0.023 mm/year (sd 0.010) for Group B, and 0.09 mm/year (sd 0.045) for Group C. Penetration was significantly higher in the UHMWPE liner group compared with both XLPE liner groups (p < 0.001) but no significant difference was noted between CoCr and OxZi when articulating with XLPE (p = 0.153). In this, the largest randomised study of this bearing surface, it appears that using a XLPE acetabular liner is more important in reducing THA component wear than the choice of femoral head bearing, at mid-term follow-up. There is a non-significant trend towards lower wear, coupling OxZi rather than CoCr with XLPE but long-term analysis is required to see if this observation changes with time and becomes significant.

Cite this article: Bone Joint J 2015;97-B:883–9.

Wear of highly crosslinked polyethylene acetabular components

BACKGROUND AND PURPOSE

Wear rates of highly crosslinked polyethylene (XLPE) acetabular components have varied considerably between different published studies. This variation is in part due to the different techniques used to measure wear and to the errors inherent in measuring the relatively low amounts of wear in XLPE bearings. We undertook a scoping review of studies that have examined the in vivo wear of XLPE acetabular components using the most sensitive method available, radiostereometric analysis (RSA).

METHODS

A systematic search of the PubMed, Scopus, and Cochrane databases was performed to identify published studies in which RSA was used to measure wear of XLPE components in primary total hip arthroplasty (THA).

RESULTS

18 publications examined 12 primary THA cohorts, comprising only 260 THAs at 2-10 years of follow-up. The mean or median proximal wear rate reported ranged from 0.00 to 0.06 mm/year. However, differences in the manner in which wear was determined made it difficult to compare some studies. Furthermore, differences in RSA methodology between studies, such as the use of supine or standing radiographs and the use of beaded or unbeaded reference segments, may limit future meta-analyses examining the effect of patient and implant variables on wear rates.

INTERPRETATION

This scoping review confirmed the low wear rates of XLPE in THA, as measured by RSA. We make recommendations to enhance the standardization of reporting of RSA wear results, which will facilitate early identification of poorly performing implants and enable a better understanding of the effects of surgical and patient factors on wear.

Standing versus supine radiographs to evaluate femoral head penetration in the polyethylene liner after total hip arthroplasty

The linear penetration rates for ceramic femoral heads on conventional and highly cross-linked polyethylene were measured and compared with radiographs taken in the standing and supine position taken three weeks postoperatively and at final follow-up. Seventy-five patients (83 hips) with conventional polyethylene (group-1) and two hundred and seventy five patients (300 hips) with highly cross-linked polyethylene (group-2) were studied. Follow-up periods were 14.5years in group-1 and 8.6years in group-2. The average penetration rates in group-1 were 0.17mm/year in supine position and 0.18mm/year in standing position (P<0.05). On the other hand, the rates in group-2 were 0.03mm/year and 0.04mm/year respectively (P<0.05). Although there were statistical differences between groups, 0.01mm differences are probably not clinically relevant.