Effect of sterilization method and other modifications on the wear resistance of acetabular cups made of ultra-high molecular weight polyethylene. A hip-simulator study

Polyethylene wear and cup migration of cemented total hip arthroplasty with femoral heads made of oxidized zirconium, steel, or cobalt chromium: a 10-year secondary analysis from a randomized trial using radiostereometry

BACKGROUND AND PURPOSE

We aimed to evaluate polyethylene (PE) wear, cup migration, and clinical outcome over 10 years in total hip arthroplasties (THA) using different articulations.

METHODS

 This is a secondary analysis of 150 patients randomized into 5 groups, using different articulations: Charnley/Charnley Ogee for steel and conventional polyethylene (CPE), or Spectron EF/Reflection with either CPE or highly cross linked polyethylene (XLPE) cups, paired with heads made of either cobalt-chromium (CoCr) or oxidized zirconium (OxZr). All cups were cemented. Patients underwent repeated radiostereometric analysis (RSA) measurements for up to 10 years to assess wear and migration. Clinical outcome was assessed using Harris Hip Score (HHS).

RESULTS

 After 10 years, the XLPE cups demonstrated low wear rates: 0.08 mm (95% confidence interval [CI] -0.11 to 0.26 mm) with CoCr heads and 0.06 mm (CI -0.14 to 0.26 mm) with OxZr heads, with a mean difference of 0.01 mm (CI -0.26 to 0.29 mm). In contrast, CPE cups exhibited significantly more wear: 1.35 mm (CI 1.16 to 1.55 mm) with CoCr heads and 1.68 mm (CI 1.44 to 1.92 mm) with OxZr heads, with a mean difference of 0.33 mm (CI 0.02 to 0.64 mm). The Charnley/Ogee group (CPE) showed PE wear of 0.34 mm (CI 0.12 to 0.56 mm). The CPE groups with OxZr and CoCr heads had 0.67 mm (CI 0.38 to 0.96 mm) and 0.35 mm (CI 0.09 to 0.61 mm) greater proximal migration respectively than the corresponding XLPE groups. HHS was similar across all groups.

CONCLUSION

 We found no significant advantage of OxZr over CoCr heads in reducing wear or migration. XLPE demonstrated a major reduction in wear as well as a reduction in cup migration compared with CPE. Charnley performed better than the other CPE cups in terms of PE wear and cup migration. No differences in clinical outcome were found.

Excellent 20-Year Results of Total Hip Arthroplasty With Highly Cross-Linked Polyethylene on Cobalt-Chromium Femoral Heads in Patients ≤50 Years

BACKGROUND

Highly cross-linked polyethylene (HXLPE) acetabular bearing surfaces have appeared to offer excellent wear resistance, low incidence of wear-related osteolysis, and high implant survivorship at 10-year to 15-year follow-up. However, concerns over potential performance deterioration at longer-term follow-up remain - particularly in younger patients - and outcome data into the third decade have not been available.

METHODS

We retrospectively assessed 62 patients (68 hips) who underwent primary total hip arthroplasty (THA) at age ≤50 years with a single manufacturer's cementless components, remelted HXLPE liner, and small diameter (26 and 28 millimeter) cobalt-chromium (CoCr) femoral heads at minimum 18-year follow-up. We assessed clinical outcomes (modified Harris Hip score, University of California Los Angeles Activity Score, polyethylene wear rates, radiographic findings (osteolysis, component loosening), and implant survivorship.

RESULTS

At 20.6-year mean follow-up (range, 18 to 23 years) modified Harris Hip scores for surviving hips remained an average of 41 points above preoperative baseline (49 versus 90, P < .001) and UCLA scores 2.8 points above baseline (3.7 versus 6.4, P < .001). Wear analysis revealed a population linear wear rate of 0.0142 mm/y (standard deviation (SD), 0.0471) and volumetric wear rate of 10.14 mm3/y (SD, 23.41). Acetabular lysis was noted in 2 asymptomatic hips at 16.6 and 18.4 years. No components were radiographically loose. Survivorship free from wear-related revision was 100% at 20 years (97% free from any revision).

CONCLUSION

The HXLPE-CoCr bearing couple with small femoral heads continues to be extremely effective 20 years after primary THA in the younger patient population.

Short-term outcomes of thin highly cross-linked polyethylene liners in primary total hip arthroplasty

INTRODUCTION

The use of thin highly cross-linked polyethylene (HXLPE) liners in total hip arthroplasty (THA) allows utilisation of larger femoral heads. However, concern surrounding postoperative complications remains. This study aims to investigate rates of revision and re-admission associated with thin HXLPE liners at short-term follow-up.

METHODS

We retrospectively reviewed 3047 patients who underwent THA with a cementless modular acetabular implant with a 36-mm femoral head, and different thicknesses of HXPLE liners from 2011 to 2021. We identified 723 patients (23.7%) with a minimum 2-year follow-up and 206 patients (6.8%) with a minimum 5-year follow-up. Patients in the thin group (TG, n = 1020) received <5.1-mm liners with 52-mm size cups while patients in the non-thin group (NTG, n = 2027) received >5.1-mm liners with >52-mm size cups. Outcomes were compared using multi-variable logistic regressions while controlling for all significant demographic differences.

RESULTS

We found no significant differences in re-admission (3.9% vs. 4.3%, OR 0.97; 95% CI, 0.63-1.49; p = 0.874) and revision (2.5% vs. 3.2%, OR 0.72; 95% CI, 0.41-1.26; p = 0.246) rates between groups. The difference in fracture rate between groups was not significant, but the 1 recorded acetabular fracture (5%) occurred in the NTG. Although the rate of liner exchange was lower in the TG (1.1%) compared to the NTG (2.3%), the difference was not statistically significant (OR 0.51; 95% CI, 0.24-1.05; p = 0.068). Liners were exchanged for liner wear in 1 hip (1%), aseptic reasons in 38 hips (66%), and peri-prosthetic joint infection in 19 hips (33%).

CONCLUSIONS

Patients undergoing THA with a thin liner were not significantly predisposed to higher rates of revision surgery or poorer clinical outcomes at short-term follow-up when compared to those who received a thicker liner. Consequently, further long-term studies regarding the utility of thin HXLPE implants in reducing complications should be pursued.

Long-term outcomes of the Universal 2 total wrist replacement: revision and loosening at 10 years and beyond

The aim of this study was to ascertain the long-term revision rates of the Universal 2 wrist prosthesis in a previously published cohort of patients with rheumatoid arthritis. The time to, and reasons for revision were determined. Radiographs were analysed to determine whether loosening had occurred in the long-term according to the Wrightington zonal classification of loosening. Seventy-eight wrists from the original cohort of 85 wrists could be identified for analysis. The longest follow-up was 16 years and 29 wrists had follow-up beyond 10 years. Seventeen wrists had been revised or were on the waiting list for revision, an overall revision rate of 22%. The 10-year survivorship was 78%. Long-term revision was commonly for periprosthetic loosening with pain and component subsidence. In those with more than 10-year follow-up, significant lucency was seen in 16 carpal components and 15 radial components. Explant analysis showed significant polyethylene wear and we postulate this is the principal reason for component loosening.Level of evidence: IV.

European Database of Explanted UHMWPE Liners from Total Joint Replacements: Correlations among Polymer Modifications, Structure, Oxidation, Mechanical Properties and Lifetime In Vivo

This contribution lays the foundation for the European database of explanted UHMWPE liners from total joint replacements. Three EU countries (Czech Republic, Italy and Spain) have joined their datasets containing anonymized patient data (such as age and BMI), manufacturer data (such as information on UHMWPE crosslinking, thermal treatment and sterilization), orthopedic evaluation (such as total duration of the implant in vivo and reasons for its revision) and material characterization (such as oxidative degradation and micromechanical properties). The joined database contains more than 500 entries, exhibiting gradual growth, and it is beginning to show interesting trends, which are discussed in our contribution, including (i) strong correlations between UHMWPE oxidative degradation, degree of crystallinity and microhardness; (ii) statistically significant differences between UHMWPE liners with different types of sterilization; (iii) realistic correlations between the extent of oxidative degradation and the observed reasons for total joint replacement failures. Our final objective and task for the future is to continuously expand the database, involving researchers from other European countries, in order to create a robust tool that will contribute to the better understanding of structure-properties-performance relationships in the field of arthroplasty implants.

Total Hip Arthroplasty With Subtrochanteric Osteotomy for Developmental Hip Dysplasia: A Long-term Follow-up Study

Background

Total hip arthroplasty (THA) for developmental hip dysplasia (DDH) often requires a subtrochanteric shortening derotational osteotomy (SDO) to limit leg lengthening, mitigate risk of peripheral nerve palsy, and reduce excessive femoral anteversion. Few studies exist detailing long-term clinical outcomes and survivorship. The aim of this study is to analyze the long-term outcomes and survivorship of an SDO-THA cohort.

Methods

We retrospectively reviewed all patients who underwent cementless THA with femoral osteotomy due to Crowe I-IV DDH between 1991 and 2001. Primary outcome measures included revision surgery for any reason and functional outcome measures using modified Harris Hip scores. Secondary outcome measures included mode of implant failure and radiographic assessment for osteotomy union, polyethylene wear, osteolysis, and implant loosening.

Results

Our review resulted in 24 SDO-THA cases in 20 patients with a mean follow-up of 19 years (range, 8-27 years). Overall survivorship was 67%. All 8 failures were treated with acetabular revision at a mean time to revision of 11 years (range, 1-25 years). Of the failures, there were 5 cases due to polyethylene wear (62.5%), 2 cases due to acetabular loosening (25%), and 1 case due to recurrent instability (12.5%). The mean postoperative modified Harris Hip score was 76 (range, 52-91) with long-term improvement of 43 points maintained (P < .001).

Conclusions

THA with SDO can produce durable long-term outcomes for the patient with DDH. It is important to consider some common reasons for revision, namely polyethylene wear and osteolysis, acetabular loosening, and recurrent acetabular dislocations.

Comparable results between crosslinked polyethylene and conventional ultra-high molecular weight polyethylene implanted in total knee arthroplasty: systematic review and meta-analysis of randomised clinical trials

PURPOSE

Total knee arthroplasty (TKA) has experienced exponential growth over the last decade, including increasingly younger patients with high functional demands. Highly crosslinked polyethylene (HXLPE) has been proven effective in reducing osteolysis and loosening revisions while improving long-term survival and performance in total hip arthroplasty; nevertheless, this superiority is not demonstrated in TKA. The aim of this systematic review and meta-analysis was to examine whether HXLPE improved overall survival and postoperative functional and radiological outcomes compared to conventional polyethylene (CPE) in TKA.

METHODS

According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, a literature search of five databases (PubMed, Medline, Scopus, Science Direct and Embase) was made. A PICOS model was performed. The initial screening identified 2541 studies. Each eligible clinical article was analysed according to the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence (LoE). Only randomised clinical trials (RCTs) of LoE 1 and 2 were included. The methodological quality of the articles was assessed using the Risk of Bias 2 (RoB 2) tool.

RESULTS

Six clinical studies were included in the final study. This systematic review and meta-analysis were registered on the International Prospective Register of Systematic Reviews (PROSPERO). A total of 2285 knees were included. Eight outcomes (total reoperations, reoperations for prosthesis loosening and infections, radiolucent lines, osteolysis, mechanical failure, postoperative KSS knee score and function score) were analysed. For none of them, a statistically significant difference was found about the superiority of HXLPE over CPE (p > 0.05).

CONCLUSIONS

There were no statistically significant differences between HXLPE and CPE for TKA concerning clinical, radiological, and functional outcomes; nevertheless, HXLPE did not show higher failure rates or complications and can be safely used for TKA.

LEVEL OF EVIDENCE

II.

Do total hip arthroplasty polyethylene liners without free radicals oxidize in vivo or ex vivo?

Crosslinking substantially reduces the wear of ultra-high molecular weight polyethylene (UHMWPE) used in total hip arthroplasty (THA) but some reports have indicated that first generation liners manufactured without antioxidants may be vulnerable to in vivo oxidation. This study evaluated maximum oxidation using Fourier transform infrared spectroscopy per ASTM F2102-06^ε1 and linear head penetration using a coordinate measuring machine among 66 revision-retrieved THA components with in vivo durations ranging from 0.02 to 24.6 years. These included 30 liners crosslinked with 5 Mrad of gamma radiation and then melted, 13 non-crosslinked, never-irradiated liners sterilized with gas plasma and 23 non-crosslinked, never-irradiated liners sterilized with ethylene oxide. All liners were vacuum-sealed and stored at -20°C prior to analysis with the exception of three retrievals of each material type that were stored in air for 9.9 to 21.5 years. All 57 vacuum-sealed and frozen retrievals demonstrated good oxidative stability with maximum oxidation indices (OIs) less than 1.0 and 75% (43/57) of these liners had maximum OIs less than 0.1. Linear penetration measurements were lower in the crosslinked liners compared to non-crosslinked retrievals. Although instances of oxidation and embrittlement were found after ex vivo storage in air among liners that did not have free radicals at the time of implantation, in vivo oxidation does not appear to be a clinical concern through the first decade of service for crosslinked liners and at up to 25 years after surgery for non-crosslinked liners.

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

Implant survival of 2,723 vitamin E-infused highly crosslinked polyethylene liners in total hip arthroplasty: data from the Finnish Arthroplasty Register

Background and purpose - The use of crosslinked polyethylene in total hip arthroplasty (THA) has decreased wear remarkably. It has been suggested that the antioxidative effects of vitamin E may enhance the wear properties of polyethylene even further. This study evaluates revision rates between vitamin E-infused polyethylene liners (E1 and E-poly, ZimmerBiomet, Warsaw, IN, USA) versus moderately crosslinked polyethylene (ModXLPE) liners from the same manufacturer used in primary THA.Patients and methods - We conducted a study based on data from the Finnish Arthroplasty Register. The study group consisted of 2,723 THAs with a vitamin E-infused liner and a reference group of 2,707 THAs with a moderately crosslinked polyethylene liner. Survivorship, revision risk, and re-revision causes were compared between groups.Results - The 7-year survival of the vitamin E-infused polyethylene liner group and of the reference group with revision for any reason as the endpoint was comparable (94% [95% CI 92.9-94.9] and 93% [CI 91.9-93.9], respectively). The adjusted hazard ratio (HR) for any revision was similar between the groups (0.7 [CI 0.4-1.1]). When revision for aseptic loosening was studied as the endpoint, the survival for the study group was 99% (CI 98.6-99.4) and for the reference group 99% (CI 98.7-99.5), and the risk of revision was comparable between the study groups (HR 1.3 [CI 0.7-2.5]).Interpretation - After an observation period of 7 years vitamin E-infused liners shows results equal to results obtained with crosslinked polyethylene liners.

Total Hip Arthroplasty in Adolescents and Young Adults for Management of Advanced Corticosteroid-Induced Osteonecrosis Secondary to Treatment for Hematologic Malignancies

BACKGROUND

Osteonecrosis of the femoral head (ONFH) is a potentially severe toxicity associated with glucocorticoid treatment for pediatric hematologic malignancy. We examined clinical outcomes of THA in adolescents and young adults treated for hematologic malignancies who developed advanced ONFH.

METHODS

In a single-institution cohort, we retrospectively reviewed medical records and imaging for perioperative complications, reoperations, functional assessment at last follow-up, and radiological outcomes. Twenty-seven patients (41 hips) underwent THA (bilateral in 14 patients). There were 11 males. Median (interquartile range [IQR]) age at primary diagnosis was 14.9 years [1.8-18.9]. The median (IQR) age at THA was 19.8 years [14.6-30.3]. Mean (range) post-THA follow-up was 111.5 months (65.4-165.8).

RESULTS

Perioperative complications included one intraoperative calcar fracture that was secured with a cerclage wire and one posterior hip dislocation that occurred 6 days postoperatively, requiring closed reduction. One hip required a revision 21.1 months post-THA due to a fractured ceramic liner. The radiographic review was available for 38 of 41 hips and demonstrated none with loosening, subsidence, or osteolysis; nine developed periacetabular stress shielding. Incidence of stress shielding was associated with increased postoperative pain (P = .0130). There was a significant functional improvement in range of motion (ROM), pain, use of supports, participation in school, work, and sports, and use of pain medication from preoperative to postoperative clinical visits (P < .001).

DISCUSSION

Total hip arthroplasty in adolescents and young adults offers symptomatic and functional improvement in patients with ONFH. We found it to be safe with low perioperative complication rates even in patients undergoing active treatment for malignancy.

LEVEL OF EVIDENCE

Level IV, case series study. See Instructions for authors for a complete description of levels of evidence.

Identification of Key Candidate Genes Related to Inflammatory Osteolysis Associated with Vitamin E-Blended UHMWPE Debris of Orthopedic Implants by Integrated Bioinformatics Analysis and Experimental Confirmation

PURPOSE

This study aims to identify differentially expressed genes (DEGs) in macrophages exposed to ultra-high-molecular-weight polyethylene (UHMWPE) or vitamin E-blended UHMWPE (VE-UHMWPE) particles, thereby providing potential targets for the treatment of inflammatory osteolysis.

METHODS

The GSE104589 dataset of genome expression in macrophages exposed to UHMWPE and VE-UHMWPE was downloaded from the Gene Expression Omnibus database to identify DEGs. Functional enrichment analysis was performed using DAVID, and the corresponding protein-protein interaction (PPI) network was constructed from the STRING database. Important modules were selected using the molecular complex detection algorithm, and hub genes were identified in cytoHubba. MicroRNAs targeting these DEGs were obtained from the TarBase, miRTarBase, and miRecords databases, while transcription factors (TFs) targeting DEGs were predicted from the ENCODE database. Finally, the top five DEGs were validated by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

A total of 112 DEGs (44 upregulated and 68 downregulated DEGs) were screened. Immune and inflammatory responses were significantly related in gene ontology analysis, and 18 signaling pathways were enriched according to Kyoto Encyclopedia of Genes and Genomes pathway analysis. The PPI network involving 85 nodes and 266 protein pairs indicated that IL1β, CXCL1, ICAM1, CCL5 and CCL4 showed higher degrees. qRT-PCR analysis of the top five DEGs revealed a decreasing trend in the VE-UHMWPE group compared with the UHMWPE group. Key microRNAs (hsa-miR-144, hsa-miR-21, and hsa-miR-221) and TFs (RELA and NFKB1) were predicted to be correlated with the pathogenesis of inflammatory osteolysis through microRNA-TF regulatory network analysis.

CONCLUSION

The present study helps shed light on the molecular mechanisms underlying the changes in the wear-induced inflammatory process after blending vitamin E with UHMWPE. Hub genes including IL1β, CXCL1, ICAM1, CCL5, and CCL4, key microRNAs (hsa-miR-144, hsa-miR-21, and hsa-miR-221) and TFs (RELA and NFKB1) may serve as prognostic and therapeutic targets of inflammatory osteolysis.

Results of primary THA using 36 mm femoral heads on first-generation highly cross-linked polyethylene in patients less than 60 years of age: Minimum 10-year follow-ups

PURPOSE

Long-term results of total hip arthroplasty (THA) using highly cross-linked polyethylene (HXLPE) and metal femoral head with more than 10 years of follow-up have already been reported. However, most studies included results with a head size of 28 mm that could affect wear rates. The aim of this study was to evaluate the results of 36-mm metallic femoral heads on first-generation HXLPE in patients less than 60 years of age with a minimum follow-up of 10 years.

METHODS

Retrospective analysis included 54 cases from 47 patients. The mean age at the time of surgery was 47.22 years and the mean follow-up period was 131.04 months. Porous-coated cementless acetabular cups (Trilolgy®; Zimmer Inc., Warsaw, Indiana, USA) and HXLPE acetabular liners (Longevity®; Zimmer Inc.) were used for all cases. Acetabular cup abduction angles, anteversion angles, and wear rates of liner were measured using polyWare pro 3D distal version 5.10.

RESULTS

The average modified Harris hip score at the final follow-up was 88.48 (range 80-96). Average Merle d'Aubigne and Postel score was 15.57 (range 14-18). There was no acetabular cup or femoral stem failing due to aseptic loosening. The average steady-state wear rate determined using radiographs taken at 1 year postoperatively and at the latest follow-up was 0.053 ± 0.025 mm/year. There were no statistically significant differences in liner wear rate with respect to age, variety of the femoral stem, or liner thickness.

CONCLUSION

Results of THA with 36-mm metallic femoral heads on first-generation HXLPE in patients less than 60 years of age were satisfactory.

Does vitamin E highly-crosslinked polyethylene convey an advantage in primary total hip replacement? A systematic review and meta-analysis

BACKGROUND

Vitamin E highly cross-linked polyethylene (HXLPE) was developed to reduce wear in total hip replacement (THR). This formal systematic review and meta-analysis aimed to provide independent synthesis of wear characteristics of Vitamin E treated HXLPE compared to HXPLE/UHMWPE. Secondary outcome measures were differences in revision rates and functional scores.

METHODS

We performed a formal systematic review as per PRISMA guidelines; literature searches were conducted on 14 November 2017 (MEDLINE, Embase on Ovid, and the Cochrane Library). We included randomised controlled trials, analyses of joint registries, and case-controlled studies of primary THR comparing cups with a vitamin E HXLPE bearing with bearing surfaces made from other types of polyethylene. Initial screening was performed by 2 independent assessors; disagreement resolved in discussion with a third reviewer. Studies were evaluated using the Cochrane risk of bias tool. Data extraction permitted meta-analysis.

RESULTS

372 studies were identified on initial screening, 5 studies met the eligibility criteria. There was no significant heterogeneity between studies. There was variable risk of bias. At a mean of 35 (range 20-60) months, Vitamin E HXLPE had significant advantages over highly cross-linked polyethylene with regards total femoral head penetration (p = 0.004). Given the RSA measurement errors this may not be clinically significant.There were neither significant differences in revision rates nor Harris Hip Scores (p = 0.06).

CONCLUSION

At a minimum of 3 years follow-up there was reduced total femoral head penetration for vitamin E HXLPE over HXLPE. This bearing surface does not, as yet, have clinically significant advantages in terms of revision rates or patient function over HXLPE.

Clinical and radiological results with a 36-mm cobalt-chrome prosthetic head, cross-linked Durasul liners associated with Allofit cups: a more than 10-year follow-up period

BACKGROUND

Highly cross-linked polyethylene is currently a common articulation surface used for total hip arthroplasty (THA).

AIM

The aim of the present study is in vivo assessment of highly cross-linked Durasul polyethylene linear and volumetric wear when associated with a 36-mm prosthetic femoral head.

METHODS

We retrospectively reviewed clinical and radiographic data of 78 patients (81 hips) having primary THAs using Durasul liner combined with a 36-mm CoCr prosthetic head. All of them were followed for more than 10 years. Patient outcome was assessed with the Harris Hip Score (HHS) preoperatively and at last follow-up. 2-D prosthetic head penetration into polyethylene, 3D wear rates and cup migration were evaluated.

RESULTS

The preoperative and last follow-up HHS were 50.43 +/- 10.42 and 97.44 +/- 5.51 respectively. The annual penetration of the prosthetic head into Durasul^® liner was 0.029 +/- 0.003 mm. The annual linear penetration and volumetric wear extrapolation rates using Charnley and Ilchmann formulas were 37.84% and 57.76% respectively of that seen with conventional polyethylene liner. At last follow-up, the total loss of material in Durasul represents only 0.15% of the initial polyethylene mass. We did not observe any significant cup migration in the study group.

CONCLUSIONS

Results are promising, and we believe that these data authorise the continued use of highly cross-linked polyethylene liner associated with a 36-mm prosthetic head for total hip arthroplasties in older patients. More long-term follow-up studies are mandatory before we feel comfortable with the project of using cross-linked polyethylene in young and active patients instead of ceramic-on-ceramic bearings.

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.

Effects of vitamin E incorporation in polyethylene on oxidative degradation, wear rates, immune response, and infections in total joint arthroplasty: a review of the current literature

Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) was introduced to decrease wear debris and osteolysis. During cross-linking, free radicals are formed, making highly cross-linked polyethylene vulnerable to oxidative degradation. In order to reduce this process, anti-oxidant vitamin E can be incorporated in polyethylene. This review provides an overview of the effects of vitamin E incorporation on major complications in total joint arthroplasty: material failure due to oxidative degradation, wear debris and subsequent periprosthetic osteolysis, and prosthetic joint infections. Secondly, this review summarizes the first clinical results of total hip and knee arthroplasties with vitamin E incorporated highly cross-linked polyethylene. Based on in vitro studies, incorporation of vitamin E in polyethylene provides good oxidative protection and preserves low wear rates. Incorporation of vitamin E may have the beneficial effect of reduced inflammatory response to its wear particles. Some microorganisms showed reduced adherence to vitamin E-incorporated UHMWPE; however, clinical relevance is doubtful. Short-term clinical studies of total hip and knee arthroplasties with vitamin E-incorporated highly cross-linked UHMWPE reported good clinical results and wear rates similar to highly cross-linked UHMWPE without vitamin E.

Influence of hip joint simulator design and mechanics on the wear and creep of metal-on-polyethylene bearings

Hip joint simulators are used extensively for preclinical testing of hip replacements. The variation in simulator design and test conditions used worldwide can affect the tribological performance of polyethylene. The aim of this study was to assess the effects of simulator mechanics and design on the wear and creep of ultra-high-molecular-weight polyethylene. In the first part of this study, an electromechanical simulator and pneumatic simulator were used to compare the wear and creep of metal-on-polyethylene components under the same standard gait conditions. In the second part of the study, the same electromechanical hip joint simulator was used to investigate the influence of kinematics on wear. Higher wear rates and penetration depths were observed from the electromechanical simulator compared with the pneumatic simulator. When adduction/abduction was introduced to the gait cycle, there was no significant difference in wear with that obtained under the gait cycle condition without adduction/abduction. This study confirmed the influence of hip simulator design and loading conditions on the wear of polyethylene, and therefore direct comparisons of absolute wear rates between different hip joint simulators should be avoided. This study also confirmed that the resulting wear path was the governing factor in obtaining clinically relevant wear rates, and this can be achieved with either two axes or three axes of rotations. However, three axes of rotation (with the inclusion of adduction/abduction) more closely replicate clinical conditions and should therefore be the design approach for newly developed hip joint simulators used for preclinical testing.

Using a patterned microtexture to reduce polyethylene wear in metal-on-polyethylene prosthetic bearing couples

The longevity of metal-on-polyethylene prosthetic hip joint bearings, in which a CoCrMo femoral head articulates with a polyethylene liner, is often limited by polyethylene wear and osteolysis caused by polyethylene wear particles. Current approaches to reduce polyethylene wear include improving the mechanical properties of the polyethylene liner, and/or manufacturing ultra-smooth articulating surfaces. In contrast, this experimental work shows that adding a patterned microtexture of concave "dimples" to a polished CoCrMo surface significantly reduces polyethylene wear by promoting the formation of an elastohydrodynamic lubricant film, which reduces contact between the CoCrMo and polyethylene bearing surfaces. Using a gravimetric method to measure polyethylene pin wear during pin-on-disc experiments, it was demonstrated that microtextured CoCrMo caused reduced polyethylene wear compared to polished CoCrMo surfaces. Wear was quantified for different polyethylene materials currently used in commercial prosthetic hip joint bearings, and for several microtexture geometries. It was also documented by correlating polyethylene wear with surface topography measurements that the patterned microtexture reduced contact between the articulating bearing surfaces.

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.

RAW 264.7 co-cultured with ultra-high molecular weight polyethylene particles spontaneously differentiate into osteoclasts: an in vitro model of periprosthetic osteolysis

Wear-particle osteolysis affects prosthesis survival leading to implant loosening up to 70% of revisions. Therapeutic strategies are increasing, however alternative testing methods to experimentally evaluate such treatments are lacking. The aim of this study was to reproduce an in vitro osteolysis model recapitulating the events that, starting from the exposure of macrophages to polyethylene, lead to the establishment of osteoclastogenesis and inflammation. Responses to polyethylene, at 3 and 7 days, in a macrophage cell line, RAW 264.7, were determined by DNA quantification, immunofluorescence, pit assay, gene expression, cytokine production and NF-kB activation. Results showed that 3 days exposure to particles could induce a significant production of Tumor Necrosis Factor alpha (p < 0.0005) and Prostaglandin E₂ (p < 0.005) compared to controls. Particles also induced macrophages to spontaneously differentiate into mature and active osteoclasts, in terms of identification of multinucleated cells by Phalloidin staining and by the analysis of osteoclast-specific gene markers. In particular, at 3 days polyethylene induced a significant up-regulation of Nuclear Factor of Activated T-cells, cytoplasmic 1, Receptor Activator of Nuclear factor Kappa-B and Receptor Activator of Nuclear Factor Kappa-B Ligand genes (p < 0.0005) compared to controls. At protein level, the particles induced a significant increase of Receptor Activator of Nuclear Factor Kappa-B Ligand at day 7 over controls (p < 0.0005). Osteoclasts were capable to resorb bone even in absence of differentiating factors. The possible mechanism, beside spontaneous osteoclastogenesis mediated by wear debris, was identified in an autocrine up-regulation of Receptor activator of nuclear factor kappa-B ligand gene expression and protein synthesis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 510-520, 2017.

The Wear Rate of Highly Cross-Linked Polyethylene in Total Hip Replacement Is Not Increased by Large Articulations: A Randomized Controlled Trial

BACKGROUND

Larger articulations reduce the risk of dislocation following primary total hip arthroplasty, leading to increased use of these articulations. The wear rate of highly cross-linked polyethylene (XLPE) is low in standard-diameter articulations but remains unclear in larger articulations. The aim of this randomized controlled trial was to compare the mean wear rates of 36-mm and 28-mm metal-on-XLPE articulations between 1 and 3 years postoperatively.

METHODS

Fifty-six elderly patients undergoing primary total hip arthroplasty were randomized intraoperatively to receive either a 36-mm or 28-mm metal-on-XLPE articulation. Factors that may affect wear were controlled by study design. Wear was measured using radiostereometric analysis.

RESULTS

Mean annual proximal wear rates between 1 and 3 years were 0.00 and 0.01 mm/yr for the 36 and 28-mm articulation cohorts, respectively. No patient had a proximal wear rate of >0.1 mm/yr. Mean wear was very low in all directions, and the wear rate of 36-mm articulations was not significantly greater than that of 28-mm articulations on the basis of proximal, medial 2-dimensional, and 3-dimensional wear.

CONCLUSIONS

The wear rate of a larger 36-mm metal-on-XLPE articulation between 1 and 3 years following primary total hip arthroplasty was low and no greater than that of a 28-mm articulation. However, before a 36-mm metal-on-XLPE articulation is widely recommended, particularly in young active patients, long-term wear rates and association between wear and periprosthetic osteolysis should be determined.

LEVEL OF EVIDENCE

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

Wear testing of total hip replacements under severe conditions

Controlled wear testing of total hip replacements in hip joint simulators is a well-established and powerful method, giving an extensive prediction of the long-term clinical performance. To understand the wear behavior of a bearing and its limits under in vivo conditions, testing scenarios should be designed as physiologically as possible. Currently, the ISO standard protocol 14242 is the most common preclinical testing procedure for total hip replacements, based on a simplified gait cycle for normal walking conditions. However, in recent years, wear patterns have increasingly been observed on retrievals that cannot be replicated by the current standard. The purpose of this study is to review the severe testing conditions that enable the generation of clinically relevant wear rates and phenomena. These conditions include changes in loading and activity, third-body wear, surface topography, edge wear and the role of aging of the bearing materials.

Mechanisms of plastic deformation in highly cross-linked UHMWPE for total hip components--the molecular physics viewpoint

Plastic deformation is an unavoidable event in biomedical polymeric implants for load-bearing application during long-term in-vivo service life, which involves a mass transfer process, irreversible chain motion, and molecular reorganization. Deformation-induced microstructural alterations greatly affect mechanical properties and durability of implant devices. The present research focused on evaluating, from a molecular physics viewpoint, the impact of externally applied strain (or stress) in ultra-high molecular weight polyethylene (UHMWPE) prostheses, subjected to radiation cross-linking and subsequent remelting for application in total hip arthroplasty (THA). Two different types of commercial acetabular liners, which belong to the first-generation highly cross-linked UHMWPE (HXLPE), were investigated by means of confocal/polarized Raman microprobe spectroscopy. The amount of crystalline region and the spatial distribution of molecular chain orientation were quantitatively analyzed according to a combined theory including Raman selection rules for the polyethylene orthorhombic structure and the orientation distribution function (ODF) statistical approach. The structurally important finding was that pronounced recrystallization and molecular reorientation increasingly appeared in the near-surface regions of HXLPE liners with increasing the amount of plastic (compressive) deformation stored in the microstructure. Such molecular rearrangements, occurred in response to external strains, locally increase surface cross-shear (CS) stresses, which in turn trigger microscopic wear processes in HXLPE acetabular liners. Thus, on the basis of the results obtained at the molecular scale, we emphasize here the importance of minimizing the development of irrecoverable deformation strain in order to retain the pristine and intrinsically high wear performance of HXLPE components.

Correlation between in vivo stresses and oxidation of UHMWPE in total hip arthroplasty

The possibility of in vivo, stress-induced oxidation in orthopaedic UHMWPE has been investigated. EtO sterilised, uncrosslinked UHMWPE liners, explanted or shelf-aged, have been collected. Linear wear and wear rate were assessed and FTIR spectroscopy was employed to detect oxidation and to build up oxidation products spatial maps across the liners section. Oxidation profiles have been compared to stress distribution profiles, resulting from a FE analysis conducted on the same liners geometries and couplings. It was found that oxidised and stressed areas followed the same asymmetrical, localized distribution profile. It was therefore possible to establish a correlation between stressed areas and observed oxidation.

Polished trays reduce backside wear independent of post location in posterior-stabilized TKAs

BACKGROUND

Backside damage of the polyethylene in TKA is a potential source of debris. The location of the tibial post in posterior-stabilized implants may influence micromotion, and thus affect backside damage, as may surface roughness.

QUESTIONS

We used implant retrieval analysis to (1) examine if there were differences in backside damage among three modern posterior-stabilized implants attributable to variable surface roughness; (2) determine if the location of damage on the tibial post affected the pattern of backside damage; and (3) determine if demographics influenced backside damage.

METHODS

We identified 403 posterior-stabilized tibial retrieved inserts (147 NexGen(®), 152 Optetrak(®), 104 Genesis(®) II). The damage on the surfaces of the tibial posts was previously graded. The backside of the inserts (divided into quadrants) were scored for evidence of damage. The total quadrant damage was compared for each implant group, the relationship between post face damage and location of damage on the backside was determined for each implant group, and total backside damage was compared among the three implant groups.

RESULTS

No correlation was found between the location of damage on the post and location of damage on the backside of the implant for any of the three groups. The Genesis(®) II polyethylene implants, which articulate with a highly polished tibial tray, showed a significantly lower total backside damage score (p < 0.01) when compared with the other two implant groups. The Genesis(®) II and Optetrak(®) showed significantly more damage in the posterior quadrants of the implants (p < 0.01) when compared with the anterior quadrants. A linear regression analysis revealed that lower tibial tray surface roughness was correlated with decreased damage.

CONCLUSIONS

An implant design with a highly polished tibial tray was associated with decreased backside damage. However, tibial post design and location did not influence the location of backside damage.

CLINICAL RELEVANCE

Our study showed that a highly polished tibial tray was associated with decreased damage to the backside of polyethylene inserts independent of post design and location. These findings should be taken into consideration when new generations of implants are designed.

Physical properties and biocompatibility of UHMWPE-derived materials modified by synchrotron radiation

The applications of synchrotron radiation (SR) in medical imaging have become of great use, particularly in angiography, bronchography, mammography, computed tomography, and X-ray microscopy. Thanks to recently developed phase contrast imaging techniques non-destructive preclinical testing of low absorbing materials such as polymers has become possible. The focus of the present work is characterization and examination of UHMWPE-derived materials widely used in medicine, before and after their exposure to SR during such testing. Physical properties, such as wettability, surface energy, IR-spectroscopy, roughness, optical microscopy, microhardness measurements of UHMWPE samples were studied before and after SR. The relationship between a growth of UHMWPE surface hydrophilicity after SR and surface colonization by stromal cells was studied in vitro. Obtained results demonstrate that SR may be used as prospective direction to examine bulk (porous) structure of polymer materials and/or to modify polymer surface and volume for tissue engineering.

A patterned microtexture to reduce friction and increase longevity of prosthetic hip joints

More than 285,000 total hip replacement surgeries are performed in the US each year. Most prosthetic hip joints consist of a cobalt-chromium (CoCr) femoral head that articulates with a polyethylene acetabular component, lubricated with synovial fluid. The statistical survivorship of these metal-on-polyethylene prosthetic hip joints declines significantly after 10 to 15 years of use, primarily as a result of polyethylene wear and wear debris incited disease. The current engineering paradigm to increase the longevity of prosthetic hip joints is to improve the mechanical properties of the polyethylene component, and to manufacture ultra-smooth articulating surfaces. In contrast, we show that adding a patterned microtexture to the ultra-smooth CoCr femoral head reduces friction when articulating with the polyethylene acetabular liner. The microtexture increases the load-carrying capacity and the thickness of the joint lubricant film, which reduces contact between the articulating surfaces. As a result, friction and wear is reduced. We have used a lubrication model to design the geometry of the patterned microtexture, and experimentally demonstrate reduced friction for the microtextured compared to conventional smooth surrogate prosthetic hip joints.

Biotribology of a vitamin E-stabilized polyethylene for hip arthroplasty - Influence of artificial ageing and third-body particles on wear

The objective of our study was to evaluate the influence of prolonged artificial ageing on oxidation resistance and the subsequent wear behaviour of vitamin E-stabilized, in comparison to standard and highly cross-linked remelted polyethylene (XLPE), and the degradation effect of third-body particles on highly cross-linked remelted polyethylene inlays in total hip arthroplasty. Hip wear simulation was performed with three different polyethylene inlay materials (standard: γ-irradiation 30 kGy, N2; highly cross-linked and remelted: γ-irradiation 75 kGy, EO; highly cross-linked and vitamin E (0.1%) blended: electron beam 80 kGy, EO) machined from GUR 1020 in articulation with ceramic and cobalt-chromium heads. All polyethylene inserts beneath the virgin references were subjected to prolonged artificial ageing (70°C, pure oxygen at 5 bar) with a duration of 2, 4, 5 or 6 weeks. In conclusion, after 2 weeks of artificial ageing, standard polyethylene shows substantially increased wear due to oxidative degradation, whereas highly cross-linked remelted polyethylene has a higher oxidation resistance. However, after enhanced artificial ageing for 5 weeks, remelted XLPE also starts oxidate, in correlation with increased wear. Vitamin E-stabilized polyethylene is effective in preventing oxidation after irradiation cross-linking even under prolonged artificial ageing for up to 6 weeks, resulting in a constant wear behaviour.

Long-term outcome of a metal-on-polyethylene cementless hip resurfacing

Due to the well-documented problems surrounding metal-on-metal bearings, the use of hip resurfacing has declined. Since the potential benefits of hip resurfacing remain desirable, it may be beneficial to investigate the long-term outcome of hip resurfacings using metal-on-polyethylene in the 1980's. We report the long-term survivorship and modes of failure of a cementless metal-on-polyethylene resurfacing (n = 178) with different porous ingrowth surfaces. While acetabular loosening was absent, a high incidence of femoral failures (femoral loosening = 18.1%, osteolytic neck fracture = 21%) occurred despite using the same ingrowth surface for both components. Ongoing developments using the lessons learned from these previous generation components and utilizing modern low wear materials, e.g., cross-linked polyethylene, may lead to improved implants for future hip resurfacings.

Quantification of structural changes of UHMWPE components in total joint replacements

Background

At present time the number of implantations of joint replacements as well as their revisions increases. Higher demands are required on the quality and longevity of implants. The aim of this work was to determine the degree of oxidative degradation and the amount of free/residual radicals in selected ultra-high molecular weight polyethylene (UHMWPE) components of the joint replacements and demonstrate that the measured values are closely connected with quality and lifetime of the polymer components.

Methods

We tested both new (4 samples) and explanted (4 samples) UHMWPE polymers for total joint replacements. The samples were characterized by infrared spectroscopy (IR), electron spin resonance (ESR) and microhardness (MH) test. The IR measurements yielded the values of oxidation index and trans-vinylene index. The ESR measurements gave the free radicals concentration.

Results

In the group of new polyethylene components, we found oxidation index values ranging from 0.00-0.03 to 0.24. The trans-vinylene index values ranged from 0.044 to 0.080. The value of free radical concentration was zero in virgin and also in sample of Beznoska Company and non-zero in the other samples. In the group of explanted components, the measured values were associated with their history, micromechanical properties and performance in vivo.

Conclusions

We demonstrated that measuring of oxidative damage may help the orthopaedic surgeon in estimating the quality of UHMWPE replacement component and thus radically to avoid early joint replacement failure due to worse polyethylene quality.

Implants for total hip arthroplasty

This article is a comprehensive review of the published literature on total hip replacement design. It seeks to provide a nonbiased view of the technology related to total hip implants and bearing surfaces. Implant designs and fixation methods are discussed with summaries of their respective long-term outcome studies. Fixation methods include cemented, cementless and hybrid techniques and are explained and presented with current outcome data and their respective failure modes that have promoted new technological development. The current data point toward cementless acetabular fixation as being superior to cemented fixation. As for stem fixation, there are good data to suggest that either method of fixation is acceptable in the proper setting. Also included in this article is a brief review of bearing surfaces and hip biomechanics.

A minimum 5-year follow-up of an oxidized zirconium femoral prosthesis used for total knee arthroplasty

BACKGROUND

Bearing surface wear remains a potential concern amongst younger patients undergoing total knee arthroplasty (TKA). Because of the potential for lower prosthetic wear rates, oxidized zirconium is a potentially attractive bearing surface for TKA in young, active patients. This material is also well suited for patients with suspected nickel sensitivities as it has no measurable nickel content, in contrast to standard femoral bearings made of cobalt-chromium alloys. Although in vitro testing on knee wear simulators has demonstrated favorable wear characteristics of oxidized zirconium compared to traditional cobalt-chrome bearings, in vivo clinical outcome data with this novel bearing surface are sparse.

METHODS

We retrospectively reviewed 109 consecutive TKAs in 82 patients at a minimum of five years postoperatively to determine prosthetic survivorship and to assess whether any adverse clinical consequences could be attributed to this bearing. Knees were evaluated with Knee Society scores, UCLA activity scores, clinical examinations, and radiographs. The mean age for this cohort was 58.7 years.

RESULTS

Survivorship free of bearing related complications was 100% at a minimum of five years post-surgery. There were no revisions for loosening, osteolysis, implant failure, or deep infection. There were no knees with radiographic failure, visible wear, loosening, or osteolysis.

CONCLUSION

Oxidized zirconium remains an attractive option for patients with nickel sensitivities and in those patients at risk for prosthetic wear due to young age or high activity levels.

Large diameter metal on metal total hip replacement for femoral neck fractures with neurological conditions: A retrospective assessment

BACKGROUND

Patients with Parkinson's disease and poliomyelitis can have a femoral neck fracture; yet, the optimal methods of treatment for these hips remains controversial. Many constrained or semi-constrained prostheses, using constrained liners (CLs) with a locking mechanism to capture the femoral head, were used to treat femoral neck fractures in patients with neurological disorders. We retrospectively studied a group of patients with Parkinson's disease and poliomyelitis who sustained femoral neck fractures and were treated by total hip arthroplasty using an L-MoM prosthesis.

MATERIALS AND METHODS

We retrospectively reviewed 12 hips in 12 patients who underwent large-diameter metal-on-metal (L-MoM) total hip replacement between May 2007 and October 2009. Eight of the 12 patients (8 hips; 66.7%) had Parkinson's disease and 4 patients (4 hips; 33.3%) were affected with poliomyelitis.

RESULTS

The followup time was 5.2 years (range 3.6-6.0 years). At the latest followup, all the patients showed satisfactory clinical and radiographic results, with pain relief. No complications, such as dislocation or aseptic loosening occurred.

CONCLUSION

We believe the use of L-MoM can diminish the rate of instability or dislocation, after operation. The L-MoM is an option for patients with Parkinson's disease and poliomyelitis with femoral neck fracture.

Monotonic and fatigue behavior of five clinically relevant conventional and highly crosslinked UHMWPEs in the presence of stress concentrations

Five formulations of clinically relevant UHMWPE (conventional, moderately crosslinked annealed and remelted, and highly crosslinked annealed and remelted) were investigated in a physiologically relevant environment. Their monotonic stress-strain behavior in the presence of notches of two different severities and at two different displacement rates was examined using a custom developed video based system. It was found that both an elevation of yield stress and a truncation of orientation hardening took place under monotonic loading and that these changes were found to be material and elastic stress concentration factor dependent. The fatigue behavior of these materials was examined using the same geometries via a stress-life approach with failure defined as fracture of the specimen in the 1000 to 100,000 cycle lifetime range. The results were modeled using the Basquin relationship (σ=AN(b), where σ=stress and N=lifetime, and A and b are experimentally derived constants) via maximum likelihood estimation methods to account for specimen runout (no failure at 250,000cycles). The conventional material was found to have a greater slope, b, and intercept, A, than the crosslinked materials as well as appearing to have less variance in its failure distributions.

Total hip arthroplasty using highly cross-linked polyethylene in patients younger than 50 years with minimum 10-year follow-up

The purpose of this study was to investigate the relatively long-term outcomes in 50 patients (54 hips) younger than 50 years of age who underwent total hip arthroplasty using highly cross-linked polyethylene (HXLPE) liners. With a minimum follow-up of 10 years, mean age at time of surgery was 38.9 years (range, 15-50 years). Survivorship was 100%. There was no radiographic evidence of osteolysis or component loosening. Mean steady-state femoral head penetration rate was 0.020 ± 0.0047 mm/yr. Clinical outcomes were excellent, with mean Harris hip score of 91.2 (range, 72-99) points at final follow-up.

New polyethylenes in total hip replacement: A ten- to 12-year follow-up study

Between 1999 and 2001, 90 patients underwent total hip replacement using the same uncemented acetabular and femoral components with a 28 mm metallic femoral head but with prospective randomisation of the acetabular liner to either Durasul highly cross-linked polyethylene or nitrogen-sterilised Sulene polyethylene. We assessed 83 patients at a minimum follow-up of ten years. Linear penetration of the femoral head was estimated at six weeks, six and 12 months and annually thereafter, using the Dorr method, given the non-spherical shape of the acetabular component. There was no loosening of any component; only one hip in the Sulene group showed proximal femoral osteolysis. The mean penetration of the femoral head at six weeks was 0.08 mm (0.02 to 0.15) for the Durasul group and 0.16 mm (0.05 to 0.28) for the Sulene group (p = 0.001). The mean yearly linear penetration was 64.8% lower for the Durasul group at 0.05 mm/year (sd 0.035) for the Sulene group and 0.02 mm/year (sd 0.016) for the Durasul (p < 0.001). Mean linear femoral head penetration at ten years was 61% less in the Durasul than Sulene group. Highly cross-linked polyethylene gives excellent results at ten years.

Comparison of conventional polyethylene wear and signs of cup failure in two similar total hip designs

Multiple factors have been identified as contributing to polyethylene wear and debris generation of the acetabular lining. Polyethylene wear is the primary limiting factor in the functional behavior and consequent longevity of a total hip arthroplasty (THA). This retrospective study reviewed the clinical and radiographic data of 77 consecutive THAs comparing in vivo polyethylene wear of two similar acetabular cup liners. Minimum follow-up was 7 years (range 7-15). The incidence of measurable wear in a group of machined liners sterilized with ethylene oxide and composed of GUR 1050 stock resin was significantly higher (61%) than the compression-molded, GUR 1020, O2-free gamma irradiation sterilized group (24%) (P = 0.0004). Clinically, at a 9-year average followup, both groups had comparable HHS scores and incidence of thigh or groin pain, though the machined group had an increased incidence of osteolysis and annual linear wear rate.