Comparison of wear rate and osteolysis between second-generation annealed and first-generation remelted highly cross-linked polyethylene in total hip arthroplasty. A case control study at a minimum of five years

Large Femoral Heads With Small Acetabular Components: An Examination of 10-Year Polyethylene Wear

Highly cross-linked polyethylene (HXLPE) has improved polyethylene (PE) wear rates while decreasing osteolysis and aseptic loosening. However, concerns exist regarding the risk of mechanical failure with thin HXLPE liners in total hip arthroplasty (THA). Our purpose was to evaluate long-term outcomes and PE wear rates in primary THAs pairing large femoral heads with small acetabular components and thin HXLPE liners. We retrospectively reviewed 29 patients who underwent 33 primary THAs using large femoral heads (32 or 36 mm) with small acetabular components (48 or 50 mm) and thin HXLPE liners (3.9 or 5.9 mm) at minimum 10-year follow-up. PE liner wear was measured using a validated radiographic technique. Mean age was 66 years, 97% of the patients were women, and mean body mass index was 26.3 kg/m2. Thirty hips (90.9%) had ceramic femoral heads, and 13 hips (39%) had 36-mm femoral heads with 3.9-mm HXLPE liners. All cases used a neutral PE design. Mean linear wear rate and volumetric wear rate were 0.04 mm/year and 39.6 mm3/year, respectively, at mean 10.9-year follow-up. There were no instances of liner fracture, liner dissociation, or revision. Mean Hip disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS, JR) was 92.1. In the largest long-term study of primary THAs using large femoral heads with small acetabular components and thin HXLPE liners, we found low linear and volumetric wear rates and no cases of liner mechanical failures. Thin HXLPE liners are a safe and viable option for THA surgeons. [Orthopedics. 2024;47(2):118-122.].

Characterization of residual debris on packaged hip arthroplasty stems demonstrates the dominance of less than 10 μm sized particulate: Updated USP788 guidelines for orthopedic implants

Past evaluation of particle contamination on packaged implants has typically been conducted using US Pharmacopeia (USP) 788, a 1970s pharmaceutical guideline created to evaluate contaminant particles in injectable fluids and syringes. Our objective was to reestablish relevant acceptance criteria for residual orthopedic and other implant debris, including smaller particles (i.e., <10 μm in diameter). Packaged total hip arthroplasty (THA) titanium (Ti6Al4V)-alloy femoral stems were used (hydroxyapatite [HA]-coated and non-coated stems). Short-term ultrasonication and longer-term 24-hour soak/agitation methods were used to elute surface-bound contaminant particles, and released particles were analyzed via scanning electron microscopy, energy-dispersive x-ray analysis, image analysis, and particle characterization. For HA-coated THA-stems, >99% of eluted particles were calcium phosphate. For plain non-coated THA-stems, >99% of eluted particles were titanium-alloy-based. The number-based median size of particles in both groups was approximately 1.5 μm in diameter despite being composed of different materials. The total volume of particulate removed from HA-coated stems was 0.037 mm3 (671 × 103 particles total), which was approximately >50-fold more volume than that on plain non-coated stems at 0.0006 mm3 (89 × 103 particles total). Only non-coated THA stems passed reestablished USP788 acceptance criteria, compared by using equivalent total volumes of contaminant particulate within new and legacy guideline ranges of >10 and >25 μm ECD, that is, <1.0 × 107 particles for <1 μm diameter in size, <600,000 for <1-10 μm, <6000 for 10-25 μm and <600 for >25 μm. These results fill a knowledge gap on how much residual debris can be expected to exist on packaged implants and can be used as a basis for updating acceptance criteria (i.e., termed USP788-Implant [USP788-I]). Residual implant particulate assessment is critical given the increasing implant complexity and new manufacturing techniques (e.g., additive manufacturing).

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

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

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

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

Wear rate and osteolysis in two types of second-generation annealed highly cross-linked polyethylene in total hip arthroplasty: A retrospective comparative study with a minimum of five years

BACKGROUND

As no previous study has directly compared the linear wear rate in two types of second-generation annealed highly cross-linked polyethylene, we performed a retrospective study with a minimum of 5-year follow-up to assess primary arthroplasties in the (1) wear rates and (2) incidence of osteolysis of the two types of HXLPE.

HYPOTHESIS

There was no significant difference in the linear wear rate and the incidence of osteolysis between the two types of second-generation annealed highly cross-linked polyethylene.

PATIENTS AND METHODS

In this single-center study, we reviewed 257 cases of primary cementless total hip arthroplasties between 2011 and 2015, which were performed with 32mm delta ceramic on second-generation annealed highly cross-linked polyethylene (X3 and E1 were used in 105 and 103 cases, respectively.). The mean wear rate was evaluated using a computer-assisted method, and the incidence of osteolysis was evaluated based on the appearance of a localized area with loss of trabecular bone or cortical erosion adjacent to the implants during the latest follow-up.

RESULTS

In total, we evaluated 208 cases, followed postoperatively for over 5 years (mean, 6.1 years, range: 5.0-8.0). There were no significant differences between the two groups with respect to age (list in order of Group X, Group E, p value) (61.2±12.3, 62.7±12.1, p=0.36), sex (ratio of male: 17.1%, 14.6%, p=0.61), body mass index (22.9±3.7, 22.8±4.0, p=0.91), pre- (49.9±14.8, 48.5±13.8, p=0.49) and post-operative (91.3±9.1, 92.7±7.0, p=0.23) Japanese Orthopaedic Association Hip Score, cup size (50.8±3.0, 50.9±2.2, p=0.70), cup inclination (38.7±4.8, 37.6±4.8, p=0.10), and cup anteversion (18.7±6.9, 18.5±7.6, p=0.80). The mean linear wear rates of the X3 and E1 groups were 0.057±0.039 (range: 0-0.16) and 0.054±0.037mm/year (range: 0-0.15), respectively (p=0.61). No osteolysis was found on the final plain radiographs in both groups.

DISCUSSION

This study revealed that both types of highly cross-linked polyethylene have excellent linear wear rates and were equally safe to use. However, the difference between the two materials in terms of the long-term wear rate should be further validated.

LEVEL OF EVIDENCE

III; retrospective case control study.

Ceramic Femoral Heads Exhibit Lower Wear Rates Compared to Cobalt Chrome: A Meta-Analysis

BACKGROUND

Wear between the femoral head and acetabular liners continues to limit the longevity of total hip arthroplasty implants despite advances in implant materials. The purpose of this meta-analysis was to compare linear wear rates of cobalt-chromium (CoCr) and fourth-generation ceramic femoral heads on highly cross-linked polyethylene (XLPE) liners.

METHODS

A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted to identify all studies between 2003 and 2020 that examined in vivo wear rates of either fourth-generation ceramics or CoCr femoral heads on XLPE liners. Studies were analyzed in a weighted means analysis of wear rates and a random effects meta-analysis.

RESULTS

A total of 36 studies met inclusion criteria (1,657 CoCr and 659 ceramic patients). The pooled, weighted mean wear rate was 0.063 mm/year (standard deviation [SD]: 0.061, confidence interval [CI]: 0.049-0.077) for CoCr and 0.047 mm/year (SD: 0.057, CI: 0.033-0.062; P < .01) for ceramic (P < .01). A meta-analysis of 4 studies directly comparing ceramic and CoCr found that CoCr heads demonstrated 0.029 mm/year more wear than ceramic heads (95% CI: 0.026-0.059, P = .306). Mean wear for 32-mm heads was significantly higher for ceramic (P < .01), while mean wear for 36-mm heads was significantly higher for CoCr (P < .01).

CONCLUSION

Fourth-generation ceramic femoral heads were found to have significantly lower wear rates than CoCr heads. Unlike previous studies, this meta-analysis included only in vivo studies and those with the same generation of highly XLPE liners.

Long-Term Wear-Related Complications of Cross-Linked Versus Conventional Polyethylene After Total Hip Arthroplasty: A Meta-Analysis

BACKGROUND

Highly cross-linked polyethylene (HXLPE) liners have been developed to address the wear-related problems associated with conventional polyethylene (CPE) such as osteolysis or aseptic loosening in total hip arthroplasty (THA). In this systematic meta-analysis, we compared the long-term efficacy in preventing radiological osteolysis and revision surgery between HXLPE and CPE.

METHODS

We included 14 studies that compared HXLPE and CPE reporting the incidence of wear-related complications with a minimum follow-up of 10 years. We investigated 5 wear-related complications: osteolysis, excessive wear, linear wear rate, revision surgery due to wear, and progress of osteolysis/aseptic loosening. We conducted a pair-wise meta-analysis to estimate odds ratio (OR) and a proportional meta-analysis to estimate the incidence of each complication.

RESULTS

Among 1,175 THAs, 220 osteolysis and 78 wear-related revisions were detected. The use of HXLPE reduced the risk of overall osteolysis (OR 0.30; P = .001), excessive wear (OR 0.10; P < .001), linear wear rate (weighted mean difference 0.09; P < .001), the risk of overall wear-related revisions (OR 0.06; P < .001), and revisions due to aseptic loosening (OR 0.23; P = .015). As per the proportional meta-analysis, the pooled prevalence of osteolysis, excessive wear, and the overall wear-related revision rate were 14%, 8%, and 3% in HXLPE and 25%, 33%, and 20% in CPE, respectively.

CONCLUSION

The current evidence shows that HXLPE dramatically reduced the rate of osteolysis and wear-related revision surgery. However, as polyethylene wear and osteolysis still lead to revision surgery, ongoing clinical and retrieval studies are required to analyze long-term outcomes.

Pairing 40-mm Femoral Heads With the Smallest Compatible Acetabular Components in Total Hip Arthroplasty: Mid-Term Outcomes in 177 Cases

BACKGROUND

Contemporary total hip arthroplasty (THA) often employs larger femoral heads to optimize hip stability. However, pairing 40-mm femoral heads with the smallest compatible acetabular components poses a potential risk for implant failure. The purpose of this study is to evaluate the outcomes of primary THAs using 40-mm femoral heads and the smallest compatible acetabular components.

METHODS

Between 2007 and 2018, 177 primary THAs involving 40-mm femoral heads and acetabular components ≤56 mm with highly cross-linked polyethylene liners were identified. Mean age was 61 years, 56% were females, and mean body mass index was 32 kg/m². Cumulative incidences of dislocation, any revision, and any reoperation were determined utilizing a competing risk model. Osteolysis and femoral head penetration were assessed at minimum 8-year follow-up (n = 16). Mean follow-up was 6 years.

RESULTS

There were no cases of liner fractures or dissociations. The 10-year cumulative incidences of dislocation, any revision, and any reoperation were 3.6%, 4.2%, and 6.8%, respectively. Mean linear femoral head penetration was 0.01 mm/y and mean volumetric wear rate was 50 mm³/y. One THA demonstrated stable, asymptomatic periacetabular radiolucent lines at most recent follow-up.

CONCLUSION

In 177 primary THAs pairing 40-mm femoral heads with the smallest compatible acetabular components, there were no liner fractures or dissociations. The cumulative incidence of dislocation was modest at 10 years. The cumulative incidences of any revision and any reoperation were low at mid-term.

LEVEL OF EVIDENCE

IV.

Sequentially Irradiated and Annealed Highly Cross-Linked Polyethylene: Linear Vector and Volumetric Wear in Total Hip Arthroplasty at 10 Years

Background

There is a paucity of data on the long-term performance of highly cross-linked polyethylene (HXLPE). Therefore, this study evaluated 10-year 1) functional, 2) radiographic, and 3) surgical outcomes in patients who underwent total hip arthroplasty with sequentially irradiated and annealed HXLPE.

Methods

A retrospective, multicenter study was conducted on patients who underwent primary total hip arthroplasty and received HXLPE polymer (n = 151). Two-dimensional radiographic linear and volumetric wear analyses were quantified using the Martell Hip Analysis software, while functional outcomes were assessed by analyzing postoperative Short-Form-12 (SF-12) Physical and Mental Health Surveys and Harris Hip Scores. Radiographic outcomes included yearly linear (mm/y) and volumetric (mm³/y) wear rates. Surgical outcomes included additional operations and survivorship.

Results

SF-12 scores were within 1 standard deviation (SD) of the normal population (SF-12 Physical: 47.0; SF-12 Mental: 52.0), while the Harris Hip Scores of 89.5 was borderline between “good” and “excellent.” Total and annual linear wear rates were 0.164 mm (SD: 0.199 mm) and 0.015 mm/y (SD: 0.018 mm/y), respectively. The mean total volumetric wear rate was 141.4 mm³ (SD: 165.0) and 12.6 mm³/y (SD: 14.9 mm³/y) when broken down into a yearly rate. Eleven patients required revisions, resulting in an all-cause polyethylene survivorship of 92.7%, with a polyethylene wear survivorship of 100.0%.

Conclusions

Our results demonstrate clinically undetectable linear and volumetric wear rates after 10 years in those who received the unique sequentially irradiated and annealed HXLPE. Furthermore, high rates of survivorship coupled with low all-cause revision rates illustrate the polymers' capability to potentially increase implant longevity.

The Lawrence D. Dorr Surgical Techniques & Technologies Award: Using Big Heads and Small Acetabular Components With Highly Cross-Linked Polyethylene in Total Hip Arthroplasty: Is It Safe?

BACKGROUND

Contemporary total hip arthroplasty (THA) employs larger femoral heads to optimize hip stability. However, the combination of large femoral heads and comparatively small acetabular components poses a potential risk for implant failure secondary to polyethylene (PE) liner fracture or dissociation. The purpose of this study was to evaluate the incidence of liner fracture or dissociation, implant survivorship, and PE wear rates in primary THAs using large femoral heads and small acetabular components.

METHODS

Between 2000 and 2017, we retrospectively identified 882 primary THAs with 36 mm femoral heads and acetabular components ≤52 mm with highly cross-linked polyethylene liners. Mean age was 66 years, 88% were females, and mean body mass index was 30 kg/m². We evaluated the cumulative incidences of dislocation, any revision, and any reoperation utilizing a competing risk model. Osteolysis and femoral head penetration were assessed with a validated radiographic technique at minimum 10-year follow-up (n = 18). Mean follow-up was 4 years.

RESULTS

There were no liner fractures or dissociations in the entire cohort. The 10-year cumulative incidences of dislocation, any revision, and any reoperation were 3.2%, 5.6%, and 9.3%, respectively. Mean linear femoral head penetration was 0.042 mm/y and mean volumetric wear rate was 44 mm³/y. No THAs demonstrated evidence of osteolysis or component loosening at long-term follow-up.

CONCLUSION

In a large cohort of primary THAs pairing large femoral heads with small acetabular components, there was no evidence of liner fracture or dissociation. Cumulative incidences of dislocation, any revision, and any reoperation were low at mid-term.

LEVEL OF EVIDENCE

IV.

Polyethylene manufacturing characteristics have a major effect on the risk of revision surgery in cementless and hybrid total hip arthroplasties

Aims

The aim of this study was to identify the effect of the manufacturing characteristics of polyethylene acetabular liners on the survival of cementless and hybrid total hip arthroplasty (THA).

Methods

Prospective cohort study using linked National Joint Registry (NJR) and manufacturer data. The primary endpoint was revision for aseptic loosening. Cox proportional hazard regression was the primary analytical approach. Manufacturing variables included resin type, crosslinking radiation dose, terminal sterilization method, terminal sterilization radiation dose, stabilization treatment, total radiation dose, packaging, and face asymmetry. Total radiation dose was further divided into G1 (no radiation), G2 (> 0 Mrad to < 5 Mrad), G3 (≥ 5 Mrad to < 10 Mrad), and G4 (≥ 10 Mrad).

Results

A total of 5,329 THAs were revised, 1,290 of which were due to aseptic loosening. Total radiation dose, face asymmetry, and stabilization treatments were found to significantly affect implant survival. G1 had the highest revision risk for any reason and for aseptic loosening and G3 and G4 the lowest. Compared with G1, the adjusted hazard ratio for G2 was 0.74 (95% confidence interval (CI) 0.64 to 0.86), G3 was 0.36 (95% CI 0.30 to 0.43), and G4 was 0.38 (95% CI 0.31 to 0.47). The cumulative incidence of revision for aseptic loosening at 12 years was 0.52 and 0.54 per 100 THAs for G3 and G4, respectively, compared with 1.95 per 100 THAs in G1. Asymmetrical liners had a lower revision risk due to aseptic loosening and reasons other than aseptic loosening compared with symmetric (flat) liners. In G3 and G4, stabilization with vitamin E and heating above melting point performed best.

Conclusion

Polyethylene liners with a total radiation dose of ≥ 5 Mrad, an asymmetrical liner face, and stabilization with heating above the melting point demonstrate best survival. Cite this article: Bone Joint J 2020;102-B(1):90–101

Comparing In Vivo Performance of Two Highly Cross-Linked Polyethylene Thermal Treatments: Remelting vs Annealing in Acetabular Liners

BACKGROUND

The introduction of highly cross-linked polyethylene (HXLPE) acetabular liners has greatly improved the wear performance of metal-on-PE bearing surfaces used in total hip arthroplasty. Changing the sterilization environment and adding thermal treatments, such as remelting or annealing, were introduced to limit on-shelf and in vivo oxidation of cross-linked liners. This study compares the wear properties of the remelted A-CLASS (MicroPort) HXLPE liner to a sequentially annealed HXLPE.

METHODS

This retrospective study assessed linear and volumetric wear rates using Martell Hip Analysis Suite, and clinical performance through incidences of revision surgeries. A total of 80 remelted and 53 annealed liners were included in the wear analysis. All hips were reviewed for revisions.

RESULTS

There were no significant differences in steady-state linear or volumetric wear rates for remelted and annealed liners, 0.01 (-0.07 to 0.14) vs -0.01 (-0.11 to 0.1) mm/y (P = .28) and -1.03 (-30.99 to 45.43) vs -1.31 (-32.23 to 23.70) mm³/y (P = .30), respectively. Both cohorts were below the 0.1 mm/y linear wear threshold. The wear rates for patients with femoral head sizes ≥36 mm were not significantly different than those with 32 and 28 mm femoral head sizes (P = .60). Similarly, wear rates for patients with an excessively vertical acetabular component (>50°) were not significantly different than those with standard acetabular component orientations (P = .97). No hips were revised due to liner-related complications.

CONCLUSION

The wear rates of the A-CLASS remelted HXLPE acetabular liner wear rates were comparable to those of a sequentially annealed HXLPE. Further long-term studies are required to ensure acceptable resistance to fatigue and in vivo oxidation.

Materials for Hip Prostheses: A Review of Wear and Loading Considerations

Replacement surgery of hip joint consists of the substitution of the joint with an implant able to recreate the articulation functionality. This article aims to review the current state of the art of the biomaterials used for hip implants. Hip implants can be realized with different combination of materials, such as metals, ceramics and polymers. In this review, we analyze, from international literature, the specific characteristics required for biomaterials used in hip joint arthroplasty, i.e., being biocompatible, resisting heavy stress, opposing low frictional forces to sliding and having a low wear rate. A commentary on the evolution and actual existing hip prostheses is proposed. We analyzed the scientific literature, collecting information on the material behavior and the human-body response to it. Particular attention has been given to the tribological behavior of the biomaterials, as friction and wear have been key aspects to improve as hip implants evolve. After more than 50 years of evolution, in term of designs and materials, the actual wear rate of the most common implants is low, allowing us to sensibly reduce the risk related to the widespread debris distribution in the human body.

Do screws and screw holes affect osteolysis in cementless cups using highly crosslinked polyethylene? A 7 to 10-year follow-up case-control study

BACKGROUND

The use of screws and the presence of screw holes may cause acetabular osteolysis and implant loosening in cementless total hip arthroplasty (THA) using conventional polyethylene. In contrast, this issue is not fully understood using highly crosslinked polyethylene (HXLPE), particularly in large comparative study. Therefore, we performed a case-control study to assess the influence of screw usage and screw holes on: (1) implant fixation and osteolysis and (2) polyethylene steady-state wear rate, using cases with HXLPE liners followed up for 7-10 years postoperatively.

HYPOTHESIS

The screw usage and screw holes adversely affect the implant fixation and incidence of wear-related osteolysis in THA with HXLPE.

PATIENTS AND METHODS

We reviewed 209 primary cementless THAs performed with 26-mm cobalt-chromium heads on HXLPE liners. To compare the effects of the use of screws and the presence of screw holes, the following groups were established: (1) with-screw (n=140); (2) without-screw (n=69); (3) no-hole (n=27) and (4) group in which a cup with screw holes, but no screw was used (n=42). Two adjunct groups (no-hole cups excluded) were established to compare the differences in the two types of HXLPE: (5) remelted group (n=100) and (6) annealed group (n=82). Implant stability and osteolysis were evaluated by plain radiography and computed tomography. The wear rate from 1 year to the final evaluation was measured using plain X-rays and PolyWare Digital software.

RESULTS

All cups and stems achieved bony fixation. On CT-scan, no acetabular osteolysis was found, but there were 3 cases with a small area of femoral osteolysis. The mean steady-state wear rate of each group was (1) 0.031±0.022, (2) 0.033±0.035, (3) 0.031±0.024, (4) 0.029±0.018, (5) 0.030±0.018 and (6) 0.034±0.023mm/year, respectively. A comparison of the effects of screw usage or screw holes found no significant between-group differences in the implant stability, prevalence of osteolysis [no acetabular osteolysis and 3/209 at femoral side (1.4%)] and steady-state wear rate.

DISCUSSION

This study suggests that there are no adverse effects on the results of THA with HXLPE from the use of cups with screw holes and the use of screws for cup fixation.

LEVEL OF EVIDENCE

Level III retrospective case-control study.

Wear Rates With Large Metal and Ceramic Heads on a Second Generation Highly Cross-Linked Polyethylene at Mean 6-Year Follow-Up

BACKGROUND

Bearing surface wear and osteolysis are major factors limiting the durability of total hip arthroplasty (THA). Second generation annealed highly cross-linked polyethylene (HXLPE) and ceramics were introduced to THA for their excellent wear rates. However, there is little data comparing the wear rates of metal and ceramic heads on second generation HXLPE.

METHODS

Sixty patients who received a noncemented THA with a 32- or 36-mm delta ceramic head were matched with 60 THAs with a 32- or 36-mm metal head based on gender, head size, follow-up, and University of California, Los Angeles activity score. Linear and volumetric wear rates were measured.

RESULTS

At mean 6-year follow-up, the mean linear wear rates were 0.012 mm/y (standard deviation [SD] 0.045; 95% confidence interval [CI] 0.001-0.024) and 0.018 mm/y (SD 0.025; 95% CI 0.012-0.025) for the ceramic and metal groups, respectively (P = .724). The mean volumetric wear rates for the ceramic and metal head groups were 11.9 (SD 43.0; 95% CI 0.7-23.0) and 17.3 (SD 23.9; 95% CI 11.1-23.4), respectively. No significant differences were detectable in either the mean linear or volumetric wear rates (P = .380 and P = .398, respectively).

CONCLUSION

Second generation HXLPE had low wear rates and we were unable to detect a significant difference in wear rates with 32- or 36-mm metal and ceramic heads. We believe that this is due to the excellent tribological properties of second generation HXLPE. We continue to use ceramic as standard of care because of issues of trunnionosis with metal heads.