Wear analysis of first-generation highly cross-linked polyethylene in primary total hip arthroplasty: an average 9-year follow-up

Wear of Third-Generation Cross-Linked Polyethylene in Primary Total Hip Arthroplasty: A 10-Year Analysis

BACKGROUND

Sequential modifications to the manufacturing process of highly cross-linked polyethylene (HXLPE) have improved the wear resistance and implant survival of these liners in total hip arthroplasty (THA). However, no study has examined the long-term (mean 10 year) wear rates and clinical outcomes of third-generation HXLPE in THA. The aim of our study was to report the longest-to-date analysis of wear rates and clinical outcomes of a third-generation HXLPE liner.

METHODS

A series of 133 THAs using a specific HXLPE acetabular liner were retrospectively evaluated. Linear and volumetric wear rates were determined using a validated radiographic technique and clinical outcomes were analyzed. Multivariate analyses were performed to determine risk factors for accelerated wear.

RESULTS

At a mean follow-up of 10.4 years (range, 8 to 13.4), the mean linear wear rate was 0.0172 mm/year and the mean volumetric wear rate was 16.99 mm3/year. There were no instances of osteolysis or mechanical failures at any time point and there was a 100% acetabular component survival rate. Younger age and use of offset liners were independent risk factors for increased wear (P < .01 for both).

CONCLUSIONS

Our series of a third-generation HXLPE demonstrated very low wear rates and excellent implant survival at a mean of 10.4 years following primary THA. Future comparative studies at the 15- and 20-year follow-up timepoints are necessary to determine if such findings translate to true improvements in the tribological properties and longevity of these liners when compared to previous generations of HXLPE liners.

Functional Ultra-High Molecular Weight Polyethylene Composites for Ligament Reconstructions and Their Targeted Applications in the Restoration of the Anterior Cruciate Ligament

The selection of biomaterials as biomedical implants is a significant challenge. Ultra-high molecular weight polyethylene (UHMWPE) and composites of such kind have been extensively used in medical implants, notably in the bearings of the hip, knee, and other joint prostheses, owing to its biocompatibility and high wear resistance. For the Anterior Cruciate Ligament (ACL) graft, synthetic UHMWPE is an ideal candidate due to its biocompatibility and extremely high tensile strength. However, significant problems are observed in UHMWPE based implants, such as wear debris and oxidative degradation. To resolve the issue of wear and to enhance the life of UHMWPE as an implant, in recent years, this field has witnessed numerous innovative methodologies such as biofunctionalization or high temperature melting of UHMWPE to enhance its toughness and strength. The surface functionalization/modification/treatment of UHMWPE is very challenging as it requires optimizing many variables, such as surface tension and wettability, active functional groups on the surface, irradiation, and protein immobilization to successfully improve the mechanical properties of UHMWPE and reduce or eliminate the wear or osteolysis of the UHMWPE implant. Despite these difficulties, several surface roughening, functionalization, and irradiation processing technologies have been developed and applied in the recent past. The basic research and direct industrial applications of such material improvement technology are very significant, as evidenced by the significant number of published papers and patents. However, the available literature on research methodology and techniques related to material property enhancement and protection from wear of UHMWPE is disseminated, and there is a lack of a comprehensive source for the research community to access information on the subject matter. Here we provide an overview of recent developments and core challenges in the surface modification/functionalization/irradiation of UHMWPE and apply these findings to the case study of UHMWPE for ACL repair.

Long-Term Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty

Background

Ceramic-on-ceramic (COC) bearings in total hip arthroplasty (THA) have long been considered the coupling with the lowest overall wear. However, concerns about complications such as ceramic breakage and noise, combined with the improved performance of polyethylene, have limited its use in the United States. This postapproval follow-up reports long-term (10 years) results of Delta COC in THA patients primarily enrolled in an Investigational Device Exemption study.

Methods

Patients received Delta COC THA in a prospective multicenter study with either 28-mm (N = 105 hips in 104 patients) or 36-mm (N = 81) articulations. Annual clinical and radiographic evaluations were performed for years 5 to 10, and study patients were asked about hip noises and reproducibility.

Results

There have been 4 additional reports of noise in 4 patients (COC 28, n = 3; COC 36, n = 1). The cumulative incidence rate for squeaking or noise at 10 years is 5.9% for COC 28 and 13.5% for COC 36. There have been 2 additional reports of dislocation in 2 patients (COC 28, n = 1; COC 36, n = 1). The cumulative incidence rate for dislocation at 10 years is 3.7% for COC 28 and 3.5% for COC 36. At 10 years, there were greater than 40 hips available for follow-up. At mean 10-year follow-up, there were a total of 3 ceramic liner fractures, but none since the previous report. There were no revisions in the 28-mm cohort, and 2 revisions in the 36-mm cohort (1 for recurrent dislocation and 1 for pain and noise). Overall Kaplan-Meier survivorship was 95.96% at 10.5 years (28 mm: 97.68% at 10.2 years; 36 mm: 94.11% at 10.4 years.)

Conclusions

At 10-year follow-up, we report excellent results in regard to survivorship, with one patient revised for pain with associated squeaking.

Highly cross-linked polyethylene still outperforms conventional polyethylene in THA: 10-year RSA results

Background and purpose - Cup wear in total hip arthroplasty (THA) can be affected by different manufacturing processes of the polyethylene (PE). We report the long-term wear pattern differences, as well as early creep behavior, between conventional PE and highly cross-linked PE (HXLPE) liners, as measured with radiostereometry (RSA) up to 10 years. We also compare migration and clinical outcome of 2 similar uncemented cups with different backside surface roughness.Patients and methods - We included 45 patients with primary osteoarthritis. 23 received a conventional liner and 22 an HXLPE liner in a similar uncemented cup, but with a slightly rougher surface. The patients were followed up with RSA and hip-specific outcome questionnaire (HOOS) at 3 months, 1, 2, 5, and 10 years.Results - During the first 3 months both liners showed expected deformation with mean proximal head penetration of 0.39 mm (conventional PE) and 0.21 mm (HXLPE). Between 3 months and 10 years there was a difference in annual wear with 0.12 mm/year for the conventional liner and 0.02 mm/year for the HXLPE liner. The cup with rougher surface had less initial migration but both types had stabilized after 3 months. The HOOS scores improved after surgery and remained high for both groups throughout the study period.Interpretation - Up to 10 years the HXLPE has consistent lower annual wear, possibly contributing to longer survival of the THA, compared with conventional PE. All patients reported good results regardless of liner type.

Prosthetic Bearing Surfaces in Anatomic and Reverse Total Shoulder Arthroplasty

Total shoulder arthroplasty (TSA) and reverse TSA have provided an effective treatment for glenohumeral osteoarthritis; however, longevity of the procedure may be limited by osteolysis and polyethylene wear. In TSA, glenoid component failure occurs through several mechanisms, the most common being aseptic loosening and polyethylene wear. Newer bearing surfaces such as highly cross-linked ultra-high-molecular-weight polyethylene, vitamin E processing, ceramic heads, and pyrolytic carbon surfaces have shown improved wear characteristics in biomechanical and some early clinical studies. The purpose of this review is to provide a historical perspective and current state of the art of bearing surface technology in anatomic and reverse TSA.

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.

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.

High survivorship of highly cross-linked polyethylene in revision Total hip Arthroplasty: a minimum 10-year follow-up study

Purpose

Highly cross-linked polyethylene has been introduced to decrease osteolysis secondary to polyethylene wear debris generation. However, few long-term data on revision total hip arthroplasty (THA) using highly cross-linked polyethylene liners are available. The objective of this study was to determine long-term outcomes of a highly cross-linked polyethylene liner in revision THA.

Materials & methods

We evaluated 63 revision THAs performed in 63 patients using a highly cross-linked polyethylene liner between April 2000 and February 2005. Of these, nine died and four were lost to follow-up. Thus, the final study cohort consisted of 50 patients (50 hips), including 26 males and 24 females with a mean age of 53 years (range, 27–75 years). Mean follow-up was 11 years (range, 10–14 years).

Results

The mean Harris hip score improved from 44 points preoperatively to 85 points at the final follow-up. No radiographic evidence of osteolysis was found in any hip. The mean rate of polyethylene liner wear was 0.029 mm/year (range, 0.003 to 0.098 mm/year). A total of 5 hips (10%) required re-revision arthroplasty, including one cup loosening, one recurrent dislocation, and three deep infections. Kaplan-Meier survivorship with an end point of re-revision for any reason was 91.1% and for aseptic cup loosening was 97.9% at 11 years.

Conclusion

At a minimum of 10 years, the highly cross-linked polyethylene liners showed excellent clinical performance and implant survivorship, and were not associated with osteolysis in our patients with revision THAs.

Comparison of Wear Rate between Ceramic-on-Ceramic, Metal on Highly Cross-linked Polyethylene, and Metal-on-Metal Bearings

Objective  Currently, there is a lack of evidence on the medium-term follow-up of cementless total hip arthroplasty (THA) using metal on highly cross-linked polyethylene (MoP), ceramic-on-ceramic (CoC), and metal-on-metal (MoM) bearings. Our aim was to calculate the 5- to 10-year wear rate and the incidence rate of osteolysis for 3 types of bearings.

Methods  A total of 77 patients underwent MoP, 105 underwent ceramic CoC, and 55 underwent MoM THAs. The average patient age at the time of surgery was 64.7, 55.9, and 59.9 years old in the MoP, CoC, and MoM bearings, respectively. Clinical and radiologic measurements at a mean follow-up of 7.6 years were analyzed.

Results  The mean postoperative Harris hip scores showed no difference among the groups. The mean annual liner wear rates were 0.0160, 0.0040 and 0.0054 mm/year in MoP, CoC bearings, and MoM bearings, with that of CoC bearings being significantly lower than the others. Osteolysis (14.5%) among MoM bearings was significantly more frequently observed compared with the others. Kaplan-Meier survival at 10 years with implant loosening, or revision THA as the endpoint, was 96.1% (95% confidence interval [CI]: 88.4–98.7) for MoP, 98.6% (95% CI: 90.3–98.6) for CoC bearing, and 98.2% (95% CI: 88.0–99.7) for MoM bearings ( p  = 0.360).

Conclusion  Excellent clinical and radiological outcomes were obtained for MoP and CoC bearings.

Up to 18-Year Follow-Up Wear Analysis of a First-Generation Highly Cross-Linked Polyethylene in Primary Total Hip Arthroplasty

BACKGROUND

The advent of highly cross-linked polyethylene (HCLPE) has significantly improved total hip arthroplasty survivorship. HCLPE has been shown to improve wear properties in midterm outcomes when compared to traditional polyethylene liners; however, there is a paucity of studies evaluating long-term outcomes. In addition, there is concern that wear rates may accelerate as the implant ages. Thus, the aims of this study are to report on the longest-to-date follow-up of a specific first-generation HCLPE liner and to determine whether there is a change in the annual wear rate over time.

METHODS

Forty hips in 38 patients which were previously reported on in a midterm study were included in this long-term follow-up study. Patients in this cohort all received total hip arthroplasty between March 1999 and August 2004 using the Crossfire HCLPE liner. Annual wear rates (mm/y) were calculated for this cohort. Patients were contacted and asked about complications or revision procedures they may have had since the index procedure.

RESULTS

Clinical follow-up averaged 12.9 years with a range of 7-18 years. The average follow-up duration was 12.5 years with a range of 10-17 years. Linear wear was found to be 0.056 ± 0.036 mm/y. Osteolysis was not observed in any of the patients with greater than 10-year radiographic follow-up. Furthermore, only 1 patient required revision surgery following a mechanical fall.

CONCLUSION

Our study demonstrates the long-term wear rates associated with HCLPE liners continue to match rates published in midterm studies. Previously, we have reported that this cohort had an average annual wear rate of 0.05 mm/y over 10 years. This most recent report demonstrates a similar wear rate with up to 18-year follow-up.

Comparison of cementless total hip arthroplasty survivorship between metal-on-highly cross-linked polyethylene and ceramic on ceramic bearings: A case control study with a 5-9-year follow-up

BACKGROUND

Currently, there is a lack of evidence on the medium-term follow-up of cementless total hip arthroplasty (THA) using metal-on-highly cross-linked polyethylene bearing (MoXPE), ceramic on ceramic bearing (CoC) at more than 5 years follow-up. Therefore, we performed a case control study to: compare the incidence rate of osteolysis; compare the longevity for both types of THAs, and to evaluate the wear rate of MoXPE THAs.

HYPOTHESIS

CoC THAs will have a lower rate of osteolysis and better longevity than MoXPE THAs.

PATIENTS AND METHODS

We performed a retrospective analysis of 77 MoXPE (68 women, 9 men) and 105 CoC (85 women, 20 men) THAs, with an average patient age at the time of surgery of 64.7 years (range, 27 to 76 years). The cohorts were matched according to sex, body mass index, or diagnosis of hip joint disease. Clinical and radiologic measurements were analyzed at a mean follow-up of 6.7 years (range, 5-9 years).

RESULTS

There were no between-group differences with regard to the Harris hip score (87.0 [64.0-98.0] and 89.9 [70.0-100.0] for the MoXPE and CoC group, respectively) and the incidence rate of osteolysis (2.6% and 1.9%, respectively). Revision was required for 1 case for each THA type. The Kaplan-Meier survival at 8 years, using implant loosening or revision as the end-point of analysis, was 96.1% (95% confidence interval [CI], 90.0-99.3) for the MoXPE group and 98.9% (95% CI, 92.2-99.8) for the CoC group (p=0.189). The mean annual liner wear rate was 0.0160mm/year (range, 0.0050 to 0.0390mm/year) for the MoXPE THAs.

DISCUSSION

There was no difference between CoC and MoXPE THAs in the incidence of osteolysis or in survival rate at 8 years post-surgery. Excellent clinical and radiological outcomes were obtained for both types of bearings.

LEVEL OF EVIDENCE

III, Case control study, case control retrospective design.

The influence of contact stress on the wear of cross-linked polyethylene

Generation of wear debris and wear particle-induced osteolysis are the main limitations of metal-on-polyethylene artificial joints. Cross-linked polyethylene has been recently used, particularly in hip replacements, as an alternative material to conventional ultrahigh molecular weight polyethylene due to its superior wear resistance. This study focused on the wear behaviour of cross-linked polyethylene under different contact stresses in order to make interpretations of its long-term in-vivo performance. A 50-station SuperCTPOD (pin-on-disc) machine was used to investigate the influence of contact stress on the wear of cross-linked polyethylene pins which were articulated against cobalt chromium discs. It was found that the wear rate of cross-linked polyethylene was lower at higher contact stresses.

Wear Kinetics of Highly Cross-Linked and Conventional Polyethylene Are Similar at Medium-term Follow-Up After Primary Total Hip Arthroplasty

BACKGROUND

Wear debris is a major factor in aseptic loosening of total hip arthroplasty. Ultra high molecular weight polyethylene inlays are known for significant wear, and the following generation, highly cross-linked polyethylene (HCLPE), has shown promising in vitro and short-term in vivo results. This study aimed to investigate wear debris of HCLPE liners with ceramic heads after 9 years to reveal the in vivo wear kinetics of this common bearing combination.

METHODS

Fifty-seven patients (72 hips; 46.5 ± 15.5 years; range 16-76 years) who underwent hip arthroplasty with an HCLPE liner (28- or 32-mm Biolox forte ceramic head) were followed up (mean 9.1 ± 2.4 years; range 3.9-13.8 years). Conventional anteroposterior X-rays were analyzed using Hip Analysis Suite software.

RESULTS

Volumetric wear had a mean of 38.67 ± 22.09 mm³/year, 333.08 ± 183.93 mm³ overall, and linear wear was 0.063 ± 0.03 mm/year and 0.546 ± 0.27 mm overall. Male patients had a significantly higher wear rate (46.42 ± 27.68 mm³/year) and total wear (400.71 ± 235.21 mm³). Larger femoral heads had a significantly higher wear rate (43.10 ± 23.93 mm³/year) and total wear (364.23 ± 203.68 mm³). Regression analysis showed a significant cubic relationship (R² = 0.307) with increasing yearly wear after approximately 108 months postoperatively.

CONCLUSIONS

HCLPE liners show significant in vivo wear after 9 years. While the total wear compared to ultra high molecular weight polyethylene liners was decreased, the wear kinetics show a comparable course. The increase in wear rate after only 108 months postoperatively is especially alarming. Longer term follow-up is needed to distinguish the long-term superiority of HCLPE liners in polyethylene-ceramic paired hip arthroplasty.

Long-term Wear Data From a Prospective Multicenter Study of Second-Generation Highly Cross-linked Polyethylene Inserts in Total Hip Arthroplasty

In a prospective multicenter trial on highly cross-linked polyethylene inserts in patients undergoing total hip arthroplasty, 118 patients consented to 10-year follow-up. Medium-term follow-up results showed low wear at 5 and 7 years after surgery. The current study focuses on long-term data at 10 years. Patients were followed up by either phone or office visit to collect long-term clinical data including Harris hip score and adverse events. There were 2 deaths and 2 revisions, 1 at 6.5 years for pelvic cyst and severe pain and another at 8.0 years for recurrent dislocation. For wear analysis, suitable radiographic images for 48 patients (52 hips) at minimum 10-year follow-up were available. Mean age of the cohort was 62.5 years (62% female). Femoral head penetration was measured using Martell's method from the radiographic images between the 6-week and the subsequent follow-ups. Polyethylene wear rate was calculated from the penetration data. Descriptive statistics were performed. There was no evidence of significant oxidation or locking mechanism failure. Mean Harris hip score of the group was 94.3. No osteolysis was noted by an independent radiographic reviewer. The slope of the bestfit regression line to the femoral head penetration data, which represents the overall linear wear rate of the polyethylene, was 0.014 mm/y. The wear rate was significantly below the 0.100 mm/y critical threshold for development of osteolysis. Volumetric wear rate was calculated to be 11.6 mm³/y. The second-generation highly cross-linked polyethylene acetabular inserts had low wear in the long term (10.3 years) with no incidence of osteolysis. [Orthopedics. 2018; 41(4):e529-e533.].

Enzymes and cytokines disease in total hip arthroplasty: promoters of immune loosening

Introducción. Una de las causas más importantes de falla de la prótesis de cadera lo constituye el fenómeno de aflojamiento, el cual se relaciona con la liberación de enzimas mediada por citocinas y produce la lisis del hueso que soporta el implante.Objetivo. Describir los mecanismos de interacción biológica de las moléculas promotoras del aflojamiento de la prótesis total de cadera que con mayor frecuencia están presentes en el proceso.Materiales y métodos. Se realizó una búsqueda de artículos originales y casos clínicos en las bases de datos PubMed y Scopus, sin límite de fecha de publicación, utilizando los términos MeSH “hip prosthesis loosening”, “aseptic loosening”, “cytokines” y “hip arthroplasty failure”. La extracción de datos se hizo mediante la lectura de 250 estudios, de los cuales se seleccionaron 66 para fines de redacción.Resultados. Los autores describen las moléculas más representativas implicadas en el aflojamiento de la prótesis de cadera, además se presentan las interacciones entre ellas.Conclusiones. Enzimas y citocinas han sido ampliamente estudiadas por cuatro décadas, aunque sus mecanismos de interacción son poco conocidos. Los autores proponen un mecanismo de interacción, proceso que podría denominarse “enfermedad de las enzimas y citocinas” o “aflojamiento inmunológico”.

Wear Analysis of Highly Cross-Linked Polyethylene in Young and Active Patients at Average Fourteen Years: A Concise Follow-Up of a Previous Report

BACKGROUND

Concerns persist regarding the oxidative stability of annealed highly cross-linked polyethylene (HXLPE) and hence its wear performance especially long term in young and active patients. The purpose of this study is to assess the wear rates and clinical outcomes of a first-generation annealed HXLPE.

METHODS

Forty-six patients (57 hips) with noncemented fixation, a mean age of 53 years, and a mean University of California Los Angeles activity score of 8 underwent primary total hip arthroplasty. A 28-mm femoral head against HXLPE liner was used in all cases. Linear wear rates were measured by 2 independent observers. Radiological and clinical assessments were recorded.

RESULTS

At a mean of 14 years (range 10-17), the wear rate was 0.03 mm/y (SD ±0.02). There were no revisions for wear-related complications. Using revision for wear-related complications as an endpoint, the survivorship was 100% and we observed no osteolysis. Western Ontario and McMaster Universities Osteoarthritis Index, patient administered questionnaire, and Hospital for Special Surgery hip scores were 91/100, 5/100, and 37/40 respectively.

CONCLUSION

This study confirms that a first-generation annealed HXLPE shows excellent wear and clinical results at 10-17 years in young and active patients. Oxidative degradation of an annealed HXLPE does not adversely affect wear and shows no other wear-related complications.

Results of Total Hip Arthroplasty with 36-mm Metallic Femoral Heads on 1st Generation Highly Cross Linked Polyethylene as a Bearing Surface in Less than Forty Year-old Patients: Minimum Ten-year Results

Purpose

We evaluated long-term clinical and radiographic results in patients underwent primary total hip arthroplasty (THA) using 36-mm metallic femoral head and 1st generation highly cross-linked polyethylene among patients aged 40 years and less, with minimum 10 years follow-up.

Materials and Methods

We retrospectively reviewed 20 hips underwent primary THA by one hip surgeon using 36-mm femoral head and 1st generation highly cross-linked polyethylene from 2004 to 2006. Mean follow up was 131.55 months. Clinical follow-ups included functional measurements. And we evaluated post operative complications, prosthesis loosening, failure, and osteolysis. For radiologic evaluations, together with position of acetabular cup at 6 weeks later of postoperation, we separately calculated the penentrations of femoral heads into polyethylene liners during postoperation and one year later check-ups, and during one year later check-ups and final check-ups. Polywear pro3D 5.10 software was used to measure penetrations of femoral head.

Results

Mean acetabular cup inclination and anteversion were 49.02° and 10.19°, respectively. Mean thickness of the polyethylene liner at 45° was 6.44 mm. There were no major complications such as implant loosening or osteolysis, and one case of dislocation occurred. Average modified Harris hip score at final follow-up was 91, and Merle d'Aubigne and Postel scores 15 were or over. Average femoral head penetration of bedding wear was 0.170±0.039 mm/year. Steady-state wear rates was 0.059±0.006 mm/year.

Conclusion

Results of THA with 36-mm metallic femoral heads on 1st generation highly cross linked as a bearing surface in less than 40 year-old patients were satisfactory.

Thirteen-year wear rate comparison of highly crosslinked and conventional polyethylene in total hip arthroplasty: long-term follow-up of a prospective randomized controlled trial

BACKGROUND

The purpose of this study was to report the radiographic wear rates from a previous randomized controlled trial of first-generation highly crosslinked versus conventional polyethylene in total hip arthroplasty (THA) at a minimum of 13 years' follow-up.

METHODS

Patients returned for radiographic imaging and radiostereometric analysis (RSA). Radiographs were reviewed for the presence of osteolysis or component loosening. Femoral head penetration (which includes both wear and creep) was measured using RSA. We compared Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), 12-Item Short Form Health Survey (SF-12) and Harris Hip Scores (HHS) with preoperative values.

RESULTS

There was 1 revision in each group. There was no difference in WOMAC, SF-12, or HHS outcome scores between the highly crosslinked and conventional polyethylene groups (all p ≥ 0.13). Wear rate was lower with crosslinked polyethylene than conventional polyethylene (0.04 ± 0.02 mm/year v. 0.08 ± 0.03 mm/year, p = 0.007).

CONCLUSION

First-generation crosslinked polyethylene demonstrates greater wear resistance than conventional polyethylene after 13 years of implantation. Crosslinked polyethylene continues to outperform conventional polyethylene into the second decade of implantation.

Wear Rates of Larger-Diameter Cross-Linked Polyethylene at 5 to 13 Years: Does Liner Thickness or Component Position Matter?

BACKGROUND

Cross-linked polyethylene (XLPE) has demonstrated significantly reduced wear and osteolysis into the second decade for total hip arthroplasty. There is a relative paucity of data with ≥36-mm bearings. Issues include potential effects of reduced liner thickness and component position on wear, osteolysis, and mechanical failure of the bearing.

METHODS

Radiographs of 48 primary total hip arthroplasties with ≥36-mm modular XLPE bearings were analyzed at a minimum 5 years postoperative on serial radiographs using a validated, edge-detection-based algorithm. Subgroups were examined to assess the effect of bearing diameter, liner thickness, acetabular abduction angle, and acetabular anteversion on XLPE wear.

RESULTS

There was no significant difference in volumetric wear when subgroups were stratified by component factors: liner thickness (<6.5 mm vs ≥6.5 mm) 40.69 mm³/y vs 24.47 mm³/y, respectively (P = .315); acetabular component abduction angle (<45° vs ≥45°): 38.68 mm³/y vs 27.8 mm³/y, respectively (P = .522); acetabular anteversion (<20° vs ≥20°): 41.32 mm³/y vs 31.79 mm³/y, respectively (P = .521). There were no dislocations, mechanical failures, or revisions. There were 7 hips with volumetric wear rates ≥80 mm³/y; 1 had possible osteolysis.

CONCLUSION

Larger-diameter XLPE wear was not measurably affected by liner thickness, acetabular abduction angle, or acetabular anteversion. However, there is a trend for increasing volumetric wear with increasing bearing size. Wear outliers do occur, and continued follow-up of larger-diameter XLPE bearings is warranted.

Long-term Results of a First-Generation Annealed Highly Cross-Linked Polyethylene in Young, Active Patients

The survivorship of total hip arthroplasty in younger patients is dependent on the wear characteristics of the bearing surfaces. Long-term results with conventional polyethylene in young patients show a high failure rate. This study assessed the long-term results of a first-generation annealed highly cross-linked polyethylene (HCLPE) in uncemented total hip arthroplasty in young, active patients. Between 1999 and 2003, 112 total hip arthroplasty procedures performed in 91 patients with an average University of California Los Angeles activity score of 8 and mean age of 53 years (range, 24-65 years) were included from a prospective database. In all patients, a 28-mm metal femoral head on annealed HCLPE (Crossfire; Stryker, Mahwah, New Jersey) was used. At minimum 10-year follow-up (11.5±0.94 years), Kaplan-Meier survivorship was 97% for all failures (1 periprosthetic infection and 1 late dislocation) and 100% for mechanical failure (no revisions for osteolysis or loosening). This study showed low revision rates for wear-related failure and superior survivorship in young, active patients. Oxidation causing failure of the locking mechanism has not been a problem with Crossfire for up to 10 years.

Polyethylene Wear Associated With 26- and 32-mm Heads in Total Hip Arthroplasty: A Multicenter, Prospective Study

BACKGROUND

Although there were many clinical studies of highly cross-linked polyethylene (XLPE) wear among different femoral head diameters, few referred to thickness of XLPE in case larger femoral heads were used because smaller sockets were frequently used for Asian population.

METHODS

This prospective study included 240 hips that underwent primary total hip arthroplasty using XLPE combined with 26-mm (group S) or 32-mm (group L) cobalt-chromium head with maximum follow-up of 10 years. We measured 3-dimensional (3-D) linear penetration rate of XLPE among same implant design groups except head diameter and estimated the validity of thinner XLPE.

RESULTS

Our study demonstrated comparable 3-D linear penetration rates, which were 0.06 ± 0.07 mm/y for group S and 0.03 ± 0.02 mm/y for group L at 10 years after surgery and penetration rates seemed to be almost constant with no significant difference after 3 years. Minimum liner thickness (5.3 mm for 48-mm socket in combination with 32-mm femoral head) and the second thinnest XLPE (6.3 mm in case of socket from 50 mm to 54 mm combined with 32-mm femoral head) was distributed in 25% and 72% with group L, respectively, and there were no significant differences in penetration rates between 5.3-mm- and 6.3-mm-thickness groups.

CONCLUSION

Our study suggested that whether to select 26- or 32-mm diameters of femoral head does not affect XLPE wear in combination with this type of articulation.

Wear Analysis of Second-generation Highly Cross-Linked Polyethylene in Primary Total Hip Arthroplasty

A major limiting factor in the longevity of total hip replacement is the wear rate of the hip bearing. As manufacturing technology has improved during the past several decades, much attention has been focused on developing newer generations of polyethylene that have lower rates of wear while minimizing free radical formation and subsequent osteolysis. The turning point for the manufacture of polyethylene was moving from gamma irradiation in air to irradiation in a low oxygen environment, which reduced free radical formation while increasing the wear resistance. New polyethylene manufacturing methods, including multiple cycles of irradiation and annealing, have resulted in greater wear resistance. Wear analysis studies are essential to determine if these new liners actually show a benefit from prior generations of polyethylene and, more importantly, if they are safe to use. This study involved a single center retrospective review of 60 patients with a mean follow-up of 5.5 years who underwent primary total hip arthroplasty with a second-generation highly cross-linked polyethylene manufactured by 3 cycles of sequential irradiation and annealing. Linear and volumetric wear rates were determined from digitized radiographs using contemporary wear analysis software. The mean linear wear rate for the entire group was 0.025 millimeters per year (mm/y). This value represents a linear wear rate 2.7 times less than that of a first-generation highly cross-linked polyethylene and 4.2 times less than that of a conventional polyethylene. At an average of 5 years, compared with a first-generation highly cross-linked polyethylene, a second-generation highly cross-linked polyethylene appears to show significant improvement regarding wear. [Orthopedics. 2016; 39(6):e1178-e1182.].

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.

Comparative Results From a National Joint Registry Hip Data Set of a New Cross-Linked Annealed Polyethylene vs Both Conventional Polyethylene and Ceramic Bearings

BACKGROUND

Major concerns in hip arthroplasty concern the fate of bearing surfaces. Highly cross-linked polyethylene materials (HXLPE) currently demonstrate successful in vitro results with new technical procedures of cross-linking the polyethylene material, whereas processing the polyethylene below its melting temperature to produce so-called "annealed HXLPE" would allow retention of important mechanical properties.

METHODS

Data released by the National Joint Registry of England and Wales addressing in 45,877 hips the same Trident uncemented cup, allowed us to compare the performance of a consecutive cohort of patients implanted with the newest generation of annealed HXLPE acetabular bearings (X3: 21,470) vs 2 consecutive nonselected cohorts, one with conventional polyethylene (N2vac: 8225) and one with ceramic-on-ceramic (CoC) hip bearings (AL: 16,182). The main end point in survivorship has been first defined as revision for any cause, then for any cause which could be related to a failure of the bearing couple.

RESULTS

At 6-year follow-up, all Trident cups demonstrated encouraging global survival cumulative rates all between 95% and 99%. A first study demonstrated better survivorship with X3-HXLPE liners vs conventional ultrahigh molecular weight polyethylene. On the second parallel study, the cumulative survival rates were better for X3 liners as compared to CoC bearings. Moreover, when ranking the yearly cumulative percent revision rates, again the best results were obtained with X3 liners with small alumina heads (cumulative percent revision rate at 0.298).

CONCLUSION

Within the frame of this Trident study, the use of this X3 highly cross-linked annealed polyethylene could be considered as a reliable alternate solution to CoC bearings.

Once Annealed Highly Cross-Linked Polyethylene Exhibits Low Wear at 9 to 15 Years

A once annealed highly cross-linked polyethylene (HXLPE) was introduced in 1998. Concerns regarding its long-term performance and oxidative resistance exist because of the presence of retained free radicals. The authors studied 48 patients with 50 hip implants having an average age of 62 years. They were followed for 9 to 15 years. The purpose of this study was to determine linear wear rate and the incidence of osteolysis and/or mechanical failure. At an average follow-up of 12.2 years, the annual linear wear rate was 0.018 mm (SD, 0.024 mm). No mechanical failures or osteolysis have been found to date. The clinical performance of this HXLPE continues to meet expectations despite the presence of free radicals. [Orthopedics. 2016; 39(3):e565-e571.].

Porous metals and alternate bearing surfaces in shoulder arthroplasty

Total shoulder arthroplasty (TSA) provides an effective solution for the treatment of glenohumeral arthritis. However, long-term outcomes have been limited by glenoid component aseptic loosening and polyethylene (PE) wear. Previous attempts to improve glenoid fixation with metal-backed glenoids resulted in inferior results. Newer component designs that contain porous metal allow for biological ingrowth of the prosthesis, potentially improving longevity and overall outcomes. Porous metal can also improve humeral component fixation, obviating the need for cement and simplifying revision surgery. Advances such as highly cross-linked polyethylene (HXLPE), vitamin E-doped HXLPE, and alternate bearing surfaces like ceramics and pyrolytic carbon have proven to provide superior wear characteristics in other joint replacements and may prove beneficial in the shoulder as well.

Long-Term Results of Total Hip Arthroplasty with 28-Millimeter Cobalt-Chromium Femoral Heads on Highly Cross-Linked Polyethylene in Patients 50 Years and Less

Highly cross-linked polyethylene (HXLPE) is the most commonly used bearing surface in total hip arthroplasty (THA) because of its superior wear properties, but long-term results in young patients are limited. We report on the clinical outcome, radiographic wear patterns and survivorship of 72 patients ≤50 years old who had a 28-millimeter cobalt-chromium femoral head on HXLPE acetabular liner. Mean and median true linear wear rates at average ten-year follow-up were 0.0104 and 0.01 mm per year ± 0.07 mm. Mean and median two-dimensional volumetric wear rates were 12.79 mm(3) and 5.834 mm(3) per year ± 26.1mm(3) as determined by Martell analysis. As a result of the minimal wear profile, there was no evidence of radiographic osteolysis and no wear-related revisions.

Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty

This study reports mid-term results of Delta ceramic on ceramic (COC) in total hip arthroplasty (THA). Subjects received Delta COC THA in a prospective multi-center study with either 28 mm (n=177) or 36 mm (n=168) articulations. Annual clinical and radiographic evaluations were performed, and patients were asked about hip noises. At mean 5.3-year follow-up there were 3 (0.9%) post-operative liner fractures. Nine revisions were performed (2 liner fracture, 4 stem loosening, 3 deep infection). Kaplan-Meier survivorship at 6 years was 96.9% (94.0-98.4). Twenty-six (7.5%) subjects reported squeaking, of whom none were revised. One (0.3%) subject could reproduce a sound in clinic. More patients reported squeaking with a 36 mm bearing (28 mm: 7/177, 36 mm: 19/168, P=0.013).

Fixation and Wear With Contemporary Acetabular Components and Cross-Linked Polyethylene at 10-Years in Patients Aged 50 and Under

We evaluated the mid-term performance of a moderately cross-linked polyethylene THA bearing in younger patients. One hundred consecutive THAs performed in patients 50 years of age and under using the same cementless acetabular component and moderately cross-linked polyethylene were evaluated at minimum 10 year follow-up. At final follow-up 75 patients (89 hips) were living, 7 patients (7 hips) were deceased and 4 patients (4 hips) were lost to follow-up. Average Tegner and UCLA scores were 3.7 and 5.8, respectively. Average steps per year were 1.84 million. The average linear wear rate was 0.05 mm/y and steady state wear rate was 0.033 mm/y. There was no detectable osteolysis. Minimum 10 year follow-up demonstrated durable fixation and reduced wear (P<0.001) when compared to our historical controls.

Is the use of thin, highly cross-linked polyethylene liners safe in total hip arthroplasty?

PURPOSE

Due to the high number of total hip arthroplasties (THA) revised due to instability, the use of large femoral heads to reduce instability is justifiable. It is critical to determine whether or not large femoral heads used in conjunction with thin polyethylene liners lead to increased wear rates, which can lead to osteolysis. Therefore, by using validated wear-analysis software, we evaluated linear wear rates in a consecutive cohort of patients who underwent primary THA with thin polyethylene liners.

METHODS

All patients were selected from a consecutive, prospectively collected database of 241 THAs performed at a single institution by two fellowship-trained joint-reconstruction surgeons between July 2007 and June 2011. These patients were 1:1 matched to a cohort of patients who had conventional-thickness polyethylene liners.

RESULTS

No significant differences were observed between linear wear rates of thin or conventional-thickness liners. The Kaplan-Meier survivorship for both cohorts was 100 %, and no cases of polyethylene fracture were observed in either cohort.

CONCLUSIONS

Our results suggest that according to a mean follow-up of 4 years, the use of thin liners in THA is promising. Longer follow-up is required to assess whether these outcomes are observed later.

Biotribology of artificial hip joints

Hip arthroplasty can be considered one of the major successes of orthopedic surgery, with more than 350000 replacements performed every year in the United States with a constantly increasing rate. The main limitations to the lifespan of these devices are due to tribological aspects, in particular the wear of mating surfaces, which implies a loss of matter and modification of surface geometry. However, wear is a complex phenomenon, also involving lubrication and friction. The present paper deals with the tribological performance of hip implants and is organized in to three main sections. Firstly, the basic elements of tribology are presented, from contact mechanics of ball-in-socket joints to ultra high molecular weight polyethylene wear laws. Some fundamental equations are also reported, with the aim of providing the reader with some simple tools for tribological investigations. In the second section, the focus moves to artificial hip joints, defining materials and geometrical properties and discussing their friction, lubrication and wear characteristics. In particular, the features of different couplings, from metal-on-plastic to metal-on-metal and ceramic-on-ceramic, are discussed as well as the role of the head radius and clearance. How friction, lubrication and wear are interconnected and most of all how they are specific for each loading and kinematic condition is highlighted. Thus, the significant differences in patients and their lifestyles account for the high dispersion of clinical data. Furthermore, such consideration has raised a new discussion on the most suitable in vitro tests for hip implants as simplified gait cycles can be too far from effective implant working conditions. In the third section, the trends of hip implants in the years from 2003 to 2012 provided by the National Joint Registry of England, Wales and Northern Ireland are summarized and commented on in a discussion.

Wear rates of highly cross-linked polyethylene humeral liners subjected to alternating cycles of glenohumeral flexion and abduction

BACKGROUND

Although short-term outcomes of reverse total shoulder arthroplasty have been promising, long-term success may be limited due to device-specific complications, including scapular notching. Scapular notching has been explained primarily as mechanical erosion; however, the generation of wear debris may lead to further biologic changes contributing to the severity of scapular notching.

METHODS

A 12-station hip simulator was converted to a reverse total shoulder arthroplasty wear simulator subjecting conventional and highly cross-linked ultra-high-molecular-weight polyethylene humeral liners to 5 million cycles of alternating abduction-adduction and flexion-extension loading profiles.

RESULTS

Highly cross-linked polyethylene liners (36.5 ± 10.0 mm(3)/million cycle) exhibited significantly lower volumetric wear rates compared with conventional polyethylene liners (83.6 ± 20.6 mm(3)/million cycle; P < .001). The flexion-extension loading profile exhibited significantly higher wear rates for conventional (P < .001) and highly cross-linked polyethylene (P < .001) compared with the abduction-adduction loading profile. Highly cross-linked wear particles had an equivalent circle diameter significantly smaller than wear particles from conventional polyethylene (P < .001).

CONCLUSIONS

Highly cross-linked polyethylene liners significantly reduced polyethylene wear and subsequent particle generation. More favorable wear properties with the use of highly cross-linked polyethylene may lead to increased device longevity and fewer complications but must be weighed against the effect of reduced mechanical properties.

Total hip replacement using a highly crosslinked polyethylene liner in Asians with small acetabulum

PURPOSE

To evaluate the medium-term outcomes of total hip replacement (THR) using a thin highly cross-linked polyethylene (HXLPE) liner in an Asian population.

METHODS

Medical records of 20 men and 44 women aged 26 to 80 (mean, 59) years who underwent 80 THRs using a thin HXLPE liner by a single surgeon were reviewed. Indications for THR included dysplasia (n = 26), avascular necrosis (n=26), osteoarthritis (n = 22), rheumatoid arthritis (n = 4), and ankylosing spondylitis (n = 2). The surgical technique, implant used, and rehabilitation protocol were standardised. Radiographs were evaluated for cup migration and peri-implant radiolucency. Femoral head penetration was assessed at day 1 and last follow-up using the Kang modification of the Dorr and Wan method and the PowerPoint method.

RESULTS

After a mean follow-up of 7.5 (range, 5.0-11.9) years, no patient had undergone acetabular revision. Two hips were revised for the femoral stem. Femoral head penetration did not correlate with sex, age at surgery, hip pathology, acetabular inclination angle, cup size, or liner thickness. The maximum femoral head penetration was 0.09 mm/year, which was below the osteolysis threshold of 0.1 mm/year. The mean ± standard deviation femoral head penetration was 0.29 ± 0.12 mm (or 0.04 ± 0.02 mm/year) by the PowerPoint method and 0.17 ± 0.22 mm (or 0.02 ± 0.03 mm/year) by the Kang modification of the Dorr and Wan method. Femoral head penetration correlated with the number of years of follow-up (p = 0.012).

CONCLUSION

The use of a thin HXLPE liner in primary THR for patients with small acetabulum achieved good outcomes after a mean of 7.5 years.

Fixation and wear with a contemporary acetabular component and cross-linked polyethylene at minimum 10-year follow-up

Long term total hip arthroplasty follow-up has demonstrated bearing surface wear and failure of fixation as the major modes of failure. The purpose of this study was to evaluate the minimum 10year results of a third generation cementless acetabular component using moderately cross-linked polyethylene liners. 150 primary THAs were evaluated clinically for need for revision and activity evaluated using accelerometers, WOMAC, Tegner and UCLA activity-level scores. Radiographs were evaluated for wear, osteolysis and loosening. We compared this cohort to three of our previously reported cohorts. The only revision was unrelated to liner wear and all acetabular components were bone ingrown. There were no cases of acetabular osteolysis and one case of femoral osteolysis. Average steps per year were 1.59 million. Mean steady state wear rate averaged 0.04mm/year. At 10-years, excellent fixation and low wear were demonstrated using a cementless acetabular construct and moderately cross-linked polyethylene liner.

LEVEL OF EVIDENCE

Therapeutic study, Level III (retrospective comparative study-prospective cohort with historical control).

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.

No differences found in bearing related hip survivorship at 10-12 years follow-up between patients with ceramic on highly cross-linked polyethylene bearings compared to patients with ceramic on ceramic bearings

At a minimum follow-up of ten years we compared clinical and radiographic findings and survivorship in a cohort of 412 patients (447 hips) who received alumina on alumina CoC bearings to findings from a cohort of 216 patients (228 hips) with alumina on highly cross-linked polyethylene (HXLPE) bearings. All patients were operated for osteoarthritis. With bearing-related complications as endpoint, analysis showed no significant difference in survivorship between cohorts (99.8% for the CoC vs. 99.4% for HXLPE). In addition, there were no significant differences in clinical and radiographic findings between cohorts. We concluded that alumina on HXLPE bearings are a reasonable lower cost alternative to ceramic on ceramic bearing couples.

10-year follow-up wear analysis of first-generation highly crosslinked polyethylene in primary total hip arthroplasty

Our goal was to report a 10-year follow up of linear penetration rates for HCLPE, and to determine whether a difference exists between penetrations measured on pelvis or hip anterior-posterior radiographs. We reviewed 48 total hip arthroplasties where a first-generation HCLPE liner was used. Femoral head penetration was measured on both AP pelvis and hip radiographs. Total wear and wear rate at 10 years were 1.26 mm and 0.122 mm/y, respectively. The rate decreased significantly after the first 2-3 years, plateauing at a wear rate of 0.05 mm/y for the last 5 years. The AP hip total wear and wear rate were 1.38 mm and 0.133 mm/y respectively, while rates were 1.13 mm and 0.109 mm/y respectively for the pelvis radiographs (P<.05). We found a significant difference in measurements of linear penetration when comparing AP pelvis vs. hip radiographs with lower rates recorded using an AP pelvis.

Short-term wear evaluation of thin acetabular liners on 36-mm femoral heads

BACKGROUND

Dislocation remains the leading cause of revision THA. One approach to decreasing prosthetic dislocation risk has been the use of larger femoral head component sizes. The upper limit of head size in metal-on-polyethylene hip arthroplasty has historically been limited because of concerns about increased wear on thin polyethylene components. It is not known to what degree this concern should apply to more wear-resistant polyethylene components.

QUESTIONS/PURPOSES

We therefore determined (1) in vitro wear rates of polyethylene liners of varying thicknesses, (2) whether there were differences in the microscopic wear characteristics as a function of polyethylene thickness, and (3) whether thin polyethylene components resulted in early catastrophic failures.

METHODS

We used a hip wear simulator to compare the wear performance of 12 highly crosslinked polyethylene acetabular inserts. The internal diameter of all components was 36 mm, and there were three samples tested of each thickness (1.9, 3.9, 5.9, or 7.9 mm). Testing was conducted for 2.4 million cycles. Gravimetric mass loss was converted to volumetric loss, which was subsequently converted to theoretical linear penetration rates.

RESULTS

Wear rates decreased with increasing polyethylene thickness. Mean ± SD wear rates for the 1.9-, 3.9-, 5.9-, and 7.9-mm groups were 5.0 ± 0.5, 3.2 ± 0.3, 2.5 ± 1.1, and 2.2 ± 1.3 mm(3)/million cycles, respectively (p < 0.016). Calculated penetration rates were 0.015, 0.012, 0.011, and 0.010 mm/million cycles, respectively (p < 0.016). There were no catastrophic failures in any group.

CONCLUSIONS

Thinner polyethylene components demonstrated higher wear rates, although even the highest wear rate observed in the thinnest polyethylene specimen was lower than that commonly reported for noncrosslinked polyethylene components. While encouraging, these findings should be validated in vivo before clinical recommendations can be made.

Total hip and knee replacement in the mature athlete

Context:

Total hip replacement and total knee replacement are among the most successful and common surgical procedures in orthopaedics. These operations were traditionally reserved for older, sedentary patients. However, these are now being increasingly performed in patients expecting to return to athletic activities.

Evidence Acquisition:

The peer-reviewed medical literature was searched via PubMed from the years 2000 to 2013. Those studies pertinent to modern hip and knee replacement in an athletic population were selected for inclusion.

Study Design:

Literature review.

Level of Evidence:

Level 4.

Results:

There is a lack of high-quality evidence in the peer-reviewed literature relating to the replacement of hips and knees in younger athletic patients. Although many patients undergoing joint replacement are active in recreational activities, a minority engage in high-impact sports. Following surgery, overall activities tend to increase, but high-demand athletic activities may be limited by pain, functional outcome, or activity restrictions imposed by health care providers.

Conclusion:

Patients receiving hip and knee replacements should be counseled in that returning to high-impact and repetitive-loading athletic activities after surgery may shorten the life span of their implant.

Strength-of-Recommendation Taxonomy (SORT):

C.

Chronic inflammation in biomaterial-induced periprosthetic osteolysis: NF-κB as a therapeutic target

Biomaterial-induced tissue responses in patients with total joint replacement are associated with the generation of wear particles, which may lead to chronic inflammation and local bone destruction (periprosthetic osteolysis). Inflammatory reactions associated with wear particles are mediated by several important signaling pathways, the most important of which involves the transcription factor NF-κB. NF-κB activation is essential for macrophage recruitment and maturation, as well as the production of pro-inflammatory cytokines and chemokines such as TNF-α, IL-1β, IL-6 and MCP1. In addition, NF-κB activation contributes to osteoclast differentiation and maturation via RANK/RANKL signaling, which increases bone destruction and reduces bone formation. Targeting individual downstream cytokines directly (such as TNF-α or IL-1β) may not effectively prevent wear particle induced osteolysis. A more logical upstream therapeutic approach may be provided by direct modulation of the core IκB/IKKα/β/NF-κB signaling pathway in the local environment. However, the timing, dose and strategy for administration should be considered. Suppression of chronic inflammation via inhibition of NF-κB activity in patients with malfunctioning joint replacements may be an effective strategy to mitigate wear particle induced periprosthetic osteolysis.

Comparison of pre-bent titanium mesh versus polyethylene implants in patient specific orbital reconstructions

Introduction

Computerized tomography DICOM file can be relatively easily transformed to a virtual 3D model. With the help of additional software we are able to create the mirrored model of an undamaged orbit and on this basis produce an individual implant for the patient Authors decided to apply implants with any thickness, which are authors own invention to obtain volumetric support and more stable orbital wall reconstruction outcome. Material of choice was ultra-high molecular weight polyethylene (UHMWPE).

Objective

The aim of this study was to present and compare functional results of individual reconstructions of orbital wall using either titanium mesh or ultra-high molecular weight polyethylene.

Materials and methods

57 consecutive patients affected by orbital wall fracture (46 males, 11 females, mean age 34±14 year) were treated in Department of Maxillofacial Surgery from 2010 to 2012. In the first group we used patient specific treatment by titanium mesh shaped on a 3D printed model of a mirrored intact orbit (37 orbits) or by individually manufactured UHMW-PE implantby CAM milling in second group (20 orbits). All of these patients were subjected to preoperative helical computerized tomography and consultation of an ophthalmologist (including binocular single vision loss test - BSVL). Further on, patients were operated under general anaesthesia using transconjuctival approach. BSVL was again evaluated post-operationally in 1 month and 6 months later.

Results

Functional treatment results (BSVL) for both groups were similar in 1 month as well as 6 months post operational time. There was no statistically significant difference between these two groups.

Conclusions

This study of 6 months functional result assessment of pre-bent individual implants and CNC milled ultra-high molecular weight polyethylene of the orbital wall has shown it to be a predictable reconstruction method. Individually shaped UHMWPE seems to be as good as pre-bent titanium mesh.

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.

Comparative wear tests of ultra-high molecular weight polyethylene and cross-linked polyethylene

Wear particle-induced osteolysis is a major concern in hip implant failure. Therefore, recent research work has focussed on wear-resistant materials, one of the most important of which is cross-linked polyethylene. In view of this, the objective of this study was to compare the in vitro wear performance of cross-linked polyethylene to traditional ultra-high molecular weight polyethylene. In order to mimic appropriate in vivo conditions, a novel high-capacity wear tester called a circularly translating pin-on-disc was used. The results of this in vitro study demonstrated that the wear rate for cross-linked polyethylene was about 80% lower than that of conventional ultra-high molecular weight polyethylene. This difference closely matches in vivo results reported in the literature for total hip replacements that use the two biopolymers. The in vitro results were also verified against ASTM F732-00 (standard test method for wear testing of polymeric materials for use in total joint prostheses). The 50-station circularly translating pin-on-disc proved to be a reliable device for in vitro wear studies of orthopaedic biopolymers.