Highly crosslinked polyethylene does not reduce aseptic loosening in cemented THA 10-year findings of a randomized study

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.

Large articulations do not increase wear rates of thin second-generation highly cross-linked polyethylene liners at ten years

Aims

Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA.

Methods

We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point.

Results

The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years.

Conclusion

The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material.

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.

What is the Role of Stem Size and Offset in the Risk of Nonseptic Revision of the Exeter® 150-mm Stem? A Study From the Swedish Arthroplasty Register

BACKGROUND

The Exeter® stem is used worldwide, often in older patients, and it is the second most commonly used cemented stem design in Sweden. Previous studies have shown that for cemented stems with a composite beam, the smallest sizes result in an increased risk of revision for mechanical failure. However, little is known about whether the survivorship of the polished Exeter stem, which generally has been shown to be good, might be associated with design parameters such as stem dimensions or offset at extreme implant sizes.

QUESTION/PURPOSE

Are differences in (1) stem size or (2) offset of the standard Exeter V40 150-mm stem associated with differences in the risk of stem revision for aseptic loosening?

METHODS

Between 2001 and 2020, 47,161 Exeter stems were reported to the Swedish Arthroplasty Register, with very high coverage and completeness documented during the period studied. In this cohort, we included patients with primary osteoarthritis who underwent surgery with a standard Exeter stem length of 150 mm and V40 cone with any type of cemented cups that had had at least 1000 reported insertions. This selection resulted in a study cohort representing 79% (37,619 of 47,161) of the total number of Exeter stems in the registry during that time. The primary study outcome was stem revision for aseptic indications such as loosening, periprosthetic fracture, dislocation, and implant fracture. A Cox regression was performed, with adjustment for age, gender, surgical approach, year of surgery, use of highly crosslinked polyethylene cups, and femoral head size and length dictated by the shape of the head trunnion. Adjusted hazard ratios are presented with 95% confidence intervals. Two separate analyses were performed. The first analysis excluded stems with the highest offsets (50 mm and 56 mm, which were not available for stem size 0). The second analysis excluded stem size 0 to include all offsets. Because stem survival was not proportional over time, we divided the analyses into two insertion periods, 0 to 8 years and beyond 8 years.

RESULTS

Stem size 0 (compared to size 1) was associated with an increased risk of revision up to 8 years when all stem sizes were included (first analysis 0 to 8 years, HR 1.7 [95% CI 1.2 to 2.3]; p = 0.002). Forty-four percent (63 of 144) of revisions of size 0 stems were for periprosthetic fracture. There was no consistent association between stem size and risk of aseptic stem revision when size 0 was excluded in the second analysis beyond 8 years. The most common offset (44 mm) was associated with an increased risk of revision (compared with 37.5 mm) up to 8 years when all sizes were included (first analysis, HR 1.6 [95% CI 1.1 to 2.1]; p = 0.01). In the second analysis (beyond 8 years, all offsets included), offset of 44 mm was compared with offset of 37.5 mm; compared with the first period, this offset was associated with a reduced risk (HR 0.6 [95% CI 0.4 to 0.9]; p = 0.005).

CONCLUSION

We found overall high survival of the Exeter stem, with generally little or no influence of stem variations on the risk of aseptic revision. However, stem size 0 was associated with an increased risk of revision mainly for periprosthetic fractures. If the femoral anatomy offers a choice between sizes 0 and 1 in patients with poor bone quality who are at risk of periprosthetic fracture, our data speak in favor of choosing the larger stem if the surgeon believes it is safe to insert the larger size, or, if available, another stem design that has a documented lower risk of this complication. For patients with good cortical bone quality but very narrow canals, a cementless stem may also be a good alternative.

LEVEL OF EVIDENCE

Level III, therapeutic study.

How is hip anatomy reconstruction and inlay wear associated up to 10 years after primary THA using ceramic on highly crosslinked polyethylene bearings?

INTRODUCTION

Conventional polyethylene (PE) wear has been reported to be associated with femoral offset reconstruction and cup orientation after THA. Thus, the present study aimed (1) to determine the polyethylene wear rate of 32 mm ceramic heads with highly cross-linked polyethylene (HXLPE) inlays up to 10 years postoperatively and (2) to identify patient and surgery-related factors affecting the wear rate.

METHODS

A prospective cohort study was performed, investigating 101 patients with 101 cementless THAs and ceramic (32 mm) on HXLPE bearings after 6-24 months, 2-5 years and 5-10 years postoperatively. The linear wear rate was determined using a validated software (PolyWare®, Rev 8, Draftware Inc, North Webster, IN, USA) by two reviewers, blinded to each other. A linear regression model was used to identify patient and surgery-related factors on HXLPE -wear.

RESULTS

After an initial bedding-in phase of 1 year after surgery, the mean linear wear rate was 0.059 ± 0.031 mm/y at ten years (mean 7.7 years; SD 0.6 years, range 6-10), being below the osteolysis relevant threshold of 0.1 mm/year. The regression analysis demonstrated that age at surgery, BMI, cup inclination or anteversion and the UCLA score were not associated with the linear HXLPE-wear rate. Only increased femoral offset showed a significant correlation with an increased HXLPE-wear rate (correlation coefficient of 0.303; p = 0.003) with a moderate clinical effect size (Cohen's f²=0.11).

CONCLUSION

In contrast to conventional PE inlays, hip arthroplasty surgeons may be less concerned about osteolysis-related wear of the HXLPE if the femoral offset is slightly increased. This allows focusing on joint anatomy reconstruction, hip stability and leg length.

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.

Highly Crosslinked Polyethylene Liners Have Negligible Wear at 10 Years: A Radiostereometric Analysis Study

BACKGROUND

The introduction of crosslinked ultra-high molecular weight polyethylene (XLPE) acetabular liners has been very successful, with decreased wear and reduction in the rates of revision hip arthroplasties. XLPE is the preferred articulation for most surgeons; however, there are concerns about the long-term performance of XLPE liners created with different manufacturing processes, which may lead to time-dependent failure, including accelerated wear, after several years.

QUESTIONS/PURPOSES

(1) What is the amount and rate of wear during the first 10 years using radiostereometric analysis (RSA) measurements of patients who had THAs that included a second-generation XLPE bearing? (2) Does the rate of wear change after 5 years in situ?

METHODS

This is a brief follow-up of a previous RSA study. In that study, we prospectively enrolled 21 patients with osteoarthritis who underwent primary cementless THA with an XLPE acetabular liner (three cycles of 3Mrad annealed) and 32-mm articulation. That group represented 44% of the 48 THAs performed by the surgeon at the hospital where RSA was available; 16 had cemented hips, leaving 32 who were invited to participate in this study. Of those, 11 lived rurally and declined to participate, leaving 21 patients who were included in the initial study. Since then, three patients died, one developed dementia and could not participate, and one had revision THA for reasons other than wear, leaving 16 patients available for analysis at 10 years. Tantalum markers were inserted during surgery, and all patients had RSA radiographs taken at 1 week, 6 months, and 1, 2, 5, and 10 years postoperatively. Femoral head penetration into the acetabular component was measured with RSA, including bedding-in during the first year and annual wear thereafter.

RESULTS

The median medial, proximal, anterior, two-dimensional (2D), and three-dimensional (3D) wear rates between 1 and 10 years were -0.001, 0.004, -0.012, 0.000, and 0.002 mm/year, respectively. No patient in this cohort had a proximal or 2D wear rate greater than 0.025 mm/year. The median proximal wear rate between 5 and 10 years (0.002 mm/year) was not greater than wear at 1 to 5 years (0.004 mm/year).

CONCLUSION

Femoral head penetration in this second-generation XLPE liner remained very low at 10 years and accelerated wear after 5 years in situ did not occur. Concerns about late-onset wear from oxidation of irradiated-annealed XLPE were not observed. The low level of wear remains encouraging for the future clinical performance of this material.

LEVEL OF EVIDENCE

Level II, therapeutic study.

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.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

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

Highly cross-linked versus conventional polyethylene inserts in total hip arthroplasty, a five-year Roentgen stereophotogrammetric analysis randomised controlled trial

BACKGROUND

Polyethylene (PE) particles produced by wear of the acetabular insert are thought to cause osteolysis and thereby aseptic loosening of the implant in total hip arthroplasty (THA). As highly cross-linked polyethylene (HXLPE) is presumed to give lower wear rates, in vivo studies are needed to confirm this.

AIM

To compare the wear of REXPOL, a HXPLE, with conventional PE within the first five years after implantation using Roentgen stereophotogrammetric analysis (RSA).

METHODS

Patients were randomised to receive either a HXLPE (REXPOL) or a conventional PE insert during primary THA. RSA images were obtained directly postoperative and after 6 wk, 12 wk, 6 mo, 12 mo, 24 mo and five years. Functional outcomes were assessed using the Hip Injury and Osteoarthritis Outcome Score and Harris Hip Score at baseline and five years after surgery.

RESULTS

The HXLPE (REXPOL) showed less wear in the latero-medial direction. Significant wear rates of conventional PE were seen in the latero-medial and center-proximal direction and in volume and corrected volume, whereas the REXPOL did not show these outcomes over time. Improvement from baseline in functional outcome did not significantly differ.

CONCLUSION

Total 3D wear is less in THAs inserted with a REXPOL inlay than a conventional PE inlay after five years. This study confirms, for the first, that the REXPOL HXLPE inlay is preferred to standard PE.

A higher degree of polyethylene irradiation is associated with a reduced risk of revision for aseptic loosening in total hip arthroplasties using cemented acetabular components: an analysis of 290,770 cases from the National Joint Registry of England, Wales, Northern Island and the Isle of Man

Aims

To investigate the effect of polyethylene manufacturing characteristics and irradiation dose on the survival of cemented and reverse hybrid total hip arthroplasties (THAs).

Methods

In this registry study, data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man (NJR) were linked with manufacturing data supplied by manufacturers. The primary endpoint was revision of any component. Cox proportional hazard regression was a primary analytic approach adjusting for competing risk of death, patient characteristics, head composition, and stem fixation.

Results

A total of 290,770 primary THAs were successfully linked with manufacturing characteristics. Overall 4,708 revisions were analyzed, 1,260 of which were due to aseptic loosening. Total radiation dose was identified as a risk factor and included in the Cox model. For statistical modelling of aseptic loosening, THAs were grouped into three categories: G1 (no radiation); G2 ( > 0 to < 5 Mrad); and G3 ( ≥ 5 Mrad). G1 had the worst survivorship. The Cox regression hazard ratio for revision due to aseptic loosening for G2 was 0.7 (95% confidence interval (CI) 0.58 to 0.83), and for G3 0.4 (95% CI 0.30 to 0.53). Male sex and uncemented stem fixation were associated with higher risk of revision and ceramic heads with lower risk.

Conclusion

Polyethylene irradiation was associated with reduced risk of revision for aseptic loosening. Radiation doses of ≥ 5 Mrad were associated with a further reduction in risk.

Cite this article: Bone Joint Res 2020;9(9):563–571.

Long-term performance of oxidized zirconium on conventional and highly cross-linked polyethylene in total hip arthroplasty

Introduction: Polyethylene wear and subsequent osteolysis remain obstacles to the long-term survivorship of total hip arthroplasty (THA). Highly cross-linked polyethylene (XLPE) with radical quenching represents a massive leap forward with dramatically improved wear rates compared to ultra-high molecular weight polyethylene (UHMWPE). In this study we evaluate the wear of UHMWPE and XLPE coupled with oxidized zirconium (OxZr) femoral heads. Methods: A longitudinal, retrospective analysis was performed identifying consecutive patients who received a 28-mm OxZr-on-polyethylene primary THA from 2003 to 2004 by a single, high-volume arthroplasty surgeon. Patients were divided into two groups: those that received (1) UHMWPE liner and (2) a highly XLPE liner. Patients were included if clinical follow-up was complete to 2014 or later. Radiographic analysis was performed by two blinded observers. Measures included cup position, annual linear wear rate, and presence of osteolysis. Pairwise comparisons, correlations, and inter-rater reliability were calculated. Results: Eighty patients were in the UHMWPE group with an average follow-up of 10 ± 1.23 years and 88 patients in the XLPE group with an average of 10 ± 1.03-year follow-up. Average age (68) was similar between groups (p = 0.288). Observer reliability was excellent for cup abduction (ICC = 0.940), anteversion (ICC = 0.942), and detection of osteolysis (ICC = 0.811). Annual linear wear rates were significantly higher (p = 1 × 10⁻¹⁹) with UHMWPE (0.21 ± 0.12 mm/year) compared to XLPE (0.05 ± 0.03 mm/year). Linear wear rate was significantly correlated to decreasing acetabular abduction (p = 0.035). Osteolysis was noted only in the UHMWPE group, with 17 patients (21.2%) exhibiting acetabular osteolysis and 37 (46.3%) patients exhibiting femoral osteolysis. Conclusions: OxZr coupled with XLPE showed minimal wear and no osteolysis at 10-year follow up. The yearly linear penetration rate is similar to that seen in other studies of XLPE THA. A careful longitudinal follow-up will be required to determine if advanced bearings such as OxZr or ceramic can show improved performance in the second decade of implantation.

Finite element analysis of polyethylene wear in total hip replacement: A literature review

Evaluation and prediction of wear play a key role in product design and material selection of total hip replacements, because wear debris is one of the main causes of loosening and failure. Multifactorial clinical or laboratory studies are high cost and require unfeasible timeframes for implant development. Simulation using finite element methods is an efficient and inexpensive alternative to predict wear and pre-screen various parameters. This article presents a comprehensive literature review of the state-of-the-art finite element modelling techniques that have been applied to evaluate wear in polyethylene hip replacement components. A number of knowledge gaps are identified including the need to develop appropriate wear coefficients and the analysis of daily living activities.

Is Oxidized Zirconium Femoral Head Superior to Other Bearing Types in Total Hip Arthroplasty? A Systematic Review and Meta-Analysis

BACKGROUND

Oxidized zirconium (OxZi) is a relatively new type of material that combines the strength of a metal with the surface/wears properties of a ceramic. Our aim was to investigate whether OxZi femoral heads lead to lower polyethylene wear, higher survival rate, and better clinical outcomes than the other bearing types in patients treated with total hip arthroplasty (THA).

METHODS

Two reviewers independently conducted a systematic search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses using the MEDLINE/PubMed database and the Cochrane Database of Systematic Reviews. These databases were queried with the terms: a. "oxidized" AND "zirconium" AND "total" AND "hip" AND "arthroplasty"; b. "oxinium" AND "total" AND "hip" AND "arthroplasty". The primary outcome measures were the survival rate of the bearing surfaces as well as the polyethylene wear.

RESULTS

The vast majority (85.7%) of the studies, which reported the mean polyethylene wear rate, showed that there was not any significant difference between OxZi and cobalt-chrome (CoCr) femoral heads (rate ratio: 0.836; 95% confidence interval: 0.362-1.928; P = .674). All studies comparing the survival rate of OxZi and CoCr femoral heads illustrated almost excellent survivorship with both implants.

CONCLUSION

OxZi femoral heads did not lead to lower polyethylene wear rate or higher survival rate, when compared with CoCr femoral heads in patients treated with THA. On the basis of these results and taking into account the higher cost of these implants, we would not recommend the routine use of OxZi femoral heads in primary THAs.

LEVEL OF EVIDENCE

Systematic review and meta-analysis of therapeutic studies I-III.

Vx-11e protects against titanium-particle-induced osteolysis and osteoclastogenesis by supressing ERK activity

Wear particle-induced osteolysis around the prosthesis is the most common long-term complication after total joint replacement surgery which often leads to aseptic loosening of the prosthesis. Osteoclasts play key roles in the osteolytic process. Currently there is a lack of clinically effective measures to prevent or treat peri-prosthetic osteolysis and thus identification of new agents that can inhibit the enhanced osteoclastic bone resorption is warranted. Through this study, we discovered that the specific and potent ERK1/2 inhibitor, Vx-11e, can protect against calvarial osteolysis caused by titanium (Ti) particles in vivo. Low doses of Vx-11e mildly reduced osteoclast resorption whilst no calvarial osteolysis was observed with high dose Vx-11e treatment. Histological examination showed fewer osteoclasts and reduced bone erosion in the Vx-11e treated groups. In vitro cellular analyses showed that Vx-11e inhibited osteoclast formation from BMM precursors in response to RANKL, as well as bone resorption by mature osteoclasts. Mechanistically, Vx-11e impaired RANKL-induced ERK1/2 signaling by inhibiting its kinase activity thereby blocking the phosphorylation of downstream substrates. Moreover, Vx-11e significantly reduced the expression of RANKL-mediated genes such as ACP5/TRAcP, CTR, MMP-9, CTSK. Collectively, our data provides evidence for the potential therapeutic use of Vx-11e for the treatment of osteolysis diseases caused by extremely actived osteoclastogenesis.

Cross-Linked Versus Conventional Polyethylene for Long-Term Clinical Outcomes After Total Hip Arthroplasty: A Systematic Review and Meta-Analysis

Background: Cross-linked polyethylene (HXLPE) liners have been used for total hip arthroplasty (THA) to address the problem of osteolysis and revision surgery associated with conventional polyethylene (CPE) liners. This systematic review and meta-analysis investigated the long-term efficacy of HXLPE in preventing revision surgery and radiological osteolysis in comparison to CPE. Materials and Methods: A comprehensive search of PubMed, Embase, and the Cochrane Library from their respective inception to September 2018 was conducted to identify potential candidate articles. Data were pooled using Stata software 14.0. The quality of randomized controlled trials (RCTs) and observational studies was assessed by two different authors using the Cochrane risk-of-bias tool and the Newcastle-Ottawa scale (NOS), respectively. Results: Eight RCTs and six observational studies were included in this review. The pooled results significantly favored HXLPE over CPE in terms of total number of revisions and radiological osteolysis, with a risk reduction of 78% (95% confidence interval [CI] 0.13-0.36; p < 0.001) and 80% (95% CI 0.13-0.29; p < 0.001), respectively. Additionally, subgroup analyses of pooled data from RCTs and observational studies both showed the efficacy of HXLPE in the prevention of revision and osteolysis. Polyethylene wear in the HXLPE group was significantly less than that in the CPE group in terms of linear wear rates and head penetration rates (both p < 0.001). No significant differences were observed with regard to functional outcomes. Conclusions: The current evidence shows that HXLPE significantly improved the clinical and radiographic outcomes, but not the functional outcomes, in comparison to CPE in long-term follow-up.

Does the femoral offset affect replacements? The results from a National Joint Registry

BACKGROUND

Femoral component offset influences the torque forces exerted on a femoral stem and may therefore adversely affect femoral component survival. This study investigated the influence of femoral component offset on revision rates for primary total hip replacements (THR) registered on the New Zealand Joint Registry (NZJR).

METHODS

There were 106,139 primary THRs registered, resulting in 4960 revisions for any cause. There were 46,242 THRs performed using the five commonest femoral components listed on the NZJR. A total of 41,100 were done for primary osteoarthritis of which 40,548 had all the offset information available for analysis. We defined low offset as < 42 mm, standard as 42-48 mm and high offset as > 48 mm offset and examined revision rates according to the reasons for revision. We performed survival analyses for both cemented and uncemented femoral components grouped by the different offsets.

RESULTS

The all-cause revision rate was 0.54/100 component years (cys). Stems with < 42 mm offset had a revision rate of 0.58/100 cys (mean 0.58; 95% confidence interval (CI) 0.53-0.63), 42-48 mm offset 0.47 (95% CI 0.43-0.52) and > 48 mm offset 0.67 (95% CI 0.57-0.79). There was no significant difference in all-cause revision rates between varying stem offsets in uncemented stems adjusting for age and gender. In cemented stems both high and low offset stems were more likely to be revised. Uncemented stems of all offsets were more likely to undergo revision for femoral fracture.

CONCLUSIONS

Femoral component offset affects the overall all-cause revision rate of the most commonly used cemented stem, but not uncemented stem designs. In cemented stems offset influences the rate of revision for loosening and periprosthetic fractures.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Crack initiation from a clinically relevant notch in a highly-crosslinked UHMWPE subjected to static and cyclic loading

Crosslinked Ultra High Molecular Weight Polyethylene (UHMWPE), which is used as a bearing material in total joint replacement components, is subjected to static and cyclic loads in vivo. Resistance to crack initiation from a notch as a function of static and cyclic loads is not well understood for crosslinked UHMWPE. This study estimated the resistance of crosslinked UHMWPE (crosslinked with 100 kGy gamma radiation and remelted to extinguish free radicals) to crack initiation for a clinically relevant notch under both static and cyclic loading conditions. For cyclic loading, four frequencies were applied with a sine waveform and two frequencies were applied with a square waveform to independently estimate the effect of frequency and rate of loading on crack initiation. Crack initiation time and cycles to crack initiation were determined. Crack initiation time for fatigue loading conditions was substantially lower compared to static loading conditions. Crack initiation time decreased with an increase in test frequency. A square wave resulted in shorter crack initiation time compared to a sine wave. The results suggest that crosslinked UHMWPE is more resistant to crack initiation from a notch under static loading conditions compared to fatigue loading conditions.

Manufacturing, oxidation, mechanical properties and clinical performance of highly cross-linked polyethylene in total hip arthroplasty

Ultra-high molecular weight polyethylene (UHMWPE) continues to be the gold standard bearing surface in total hip arthroplasty (THA) for nearly 5 decades. Highly cross-linked UHMWPE (HXLPE) was adapted for routine use in the early 2000s to reduce the revision rates related to wear, osteolysis, and aseptic loosening resulting from conventional UHMWPE wear. Since its inception, consistent evidence showing reduced wear rates and osteolysis supports the use of HXLPE in THA. High quality studies demonstrating the advantage in long term survivorship of HXLPE over conventional UHMWPE are emerging. Though retrieval studies have demonstrated evidence of in vivo oxidation and fatigue related damage at the rim of the first generation HXLPE liners, clinical significance of this remains to be seen. Second-generation sequentially annealed and vitamin E containing HXLPE liners demonstrate improved mechanical properties, resistance to oxidation, and equivalent wear rates in comparison to their first-generation counterparts, but long term success remains to be seen.

Competitive Running After Total Hip Arthroplasty: The World's Fastest Total Hip: A Case Report

CASE

We report the case of a young man who underwent total hip arthroplasty (THA) for osteonecrosis at the age of 20 years, and subsequently competed in collegiate long-distance running. The pinnacle of his career was setting the school record time of 3:47.64 (min:sec) in the 1,500-m "metric mile" run (equivalent to 4:05.09 for the "English" mile). This is the fastest known time for any patient who has undergone THA. Excellent clinical and radiographic outcomes had been maintained at 6 years postoperatively.

CONCLUSION

Patients who undergo arthroplasty procedures may be capable of remarkable physical accomplishments, but pursuing such feats is not advised.

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.

Tanshinone IIA protects against polyethylene particle-induced osteolysis response in a mouse calvarial model

The expression of β-catenin in detectable aseptic loosening after joint replacement and the surrounding osteolysis of the prosthesis is primarily caused by the abrasive particles introduced by the prosthesis, which results in a shortened service life of the prosthesis. Recent studies have shown that debris can induce many cytokines associated with osteolysis. In particular, RANKL directly stimulates osteoclast formation and activity. Thus, we hypothesize that the osteolysis induced by wear particles can be prevented by inhibiting the RANKL signaling pathway. In this study, we established a C57BL/J6 mouse calvarial model of PE granule induced osteolysis, and studied the inhibitory action of tanshinone IIA on osteoclast formation. Eight-week-old male c57BL/J6 mouse were randomly divided into four groups: Sham group (no PE particle-induced + PBS), positive group (PE particle-inducted + PBS), low dose group (PE particle-induced + 1 ug/g tanshinone IIA), and high-dose group (PE granule-induced + 2 ug/g tanshinone II). After 21 days, the mice were executed and the calvaria were collected and processed for micro-CT scan and histomorphometry analysis. Compared to the positive subgroup, Tanshinone IIA significantly reduced bone absorption induced by PE granules and inhibited the formation and activity of osteoclasts. In addition, ELISA test showed that tanshinone IIA significantly reduced OSCAR and CTX-1 expression. Further, tanshinone IIA enhanced the formation of OPG, thus reducing osteoclast damage to the bone around the implant. Overall, these data indicate that tanshinone IIA represents a promising drug for the treatment of bone absorption by particles and can be a new method of treatment for prophylaxis of aseptic loosening.

Developmental Dysplasia Treated With Cementless Total Hip Arthroplasty Utilizing High Hip Center Reconstruction: A Minimum 13-Year Follow-up Study

BACKGROUND

The primary aim of this study was to determine the clinical outcomes at 13-year follow-up of patients diagnosed with developmental dysplasia of the hip and subsequently treated with total hip arthroplasty (THA). The secondary aim was to investigate the effect of hip center location on clinical outcomes and polyethylene wear.

METHODS

We reviewed data from a consecutive series of 104 patients (123 hips) from a single center. Patients were treated with THA with the high hip center (HHC) technique using cementless acetabular shells and highly cross-linked liners. Radiographs were collected preoperatively and through 13-year follow-up to assess degree of dysplasia (Crowe classification), component positioning, occurrence of bone resorption, and polyethylene wear. The Harris Hip Score (HHS) was administered at 4 and 13 years.

RESULTS

No patients were lost to follow-up, and one was revised for femoral loosening. Radiolucency was seen in 20% of patients and was not associated with HHC (P = .560). No patients developed osteolysis. The wear rate was low for all patients (mean: 3 ± 19 μm/y) and not associated with HHC (P = .852). The median 13-year HHS was 91.9 (interquartile range: 84.8-97.0). There was a statistically significant decline from the 4- to 13-year HHS (P < .001) for the Crowe II-IV group, although 82% of these patients remained above 80 points at 13 years. The nondysplastic and Crowe I group showed no longitudinal change in HHS (P = .243).

CONCLUSION

This cup design and highly cross-linked polyethylene liner combination demonstrates excellent clinical outcomes, similar to THA for primary osteoarthritis, through 13-year follow-up in patients with various degrees of developmental dysplasia of the hip and HHC reconstructions.

ARTICULATION AND BACKSIDE WEAR ANALYSIS AFTER LONG-TERM IN VITRO WEAR SIMULATION OF VITAMIN E STABILIZED POLYETHYLENE ACETABULAR LINERS WITH A PRESS-FIT LOCKING MECHANISM

A previous retrieval study analyzed the backside wear of short-term implanted liners against in vitro tested liners of similar life in service and showed comparable results among both groups, with no significant backside wear due to micro-motion.

The purpose — to obtain a picture of the overall wear (articulation and backside surfaces) of 0.1% vitamin e blended polyethylene liners, with a locking mechanism based on a press-fit cone in combination with a rough titanium conical inner surface in the fixation area, under a 20 million cycles hip wear simulation.

Materials and Methods. A semi-quantitative method was used in order to assess the damage on the backside of the liners and a 3d measuring machine to assess the creep and wear at the articulation surface.

Results. The total average backside wear score was 22.00±2.59 from a maximum total score of 147 after 5 million cycles (mc), increased to 31.92±5.57 after 10 mc, but showed no further increment after 15 and 20 mc. The reference liners (subjected only to axial load) showed similar wear scores and modes as the liners under wear simulation (axial load and movement). Small scratches produced during insertion and removal were clearly seen at the rim (fixation) area and no considerable abrasion was observed. The machining marks on the convex surface were always visible. Regarding the articulation surface, a steady state wear rate of 7 µm/year was measured.

Conlusion. These results determined that most of the backside wear produced on the liners occurred during their insertion and removal rather than during their life in service. Moreover, the wear at the articulation surface was similar to that seen in vivo at short- and mid-term on highly cross-linked polyethylene liners with and without vitamin e content.

Contemporary Dual Mobility Head Penetration at Five Years: Concern for the Additional Convex Bearing Surface?

BACKGROUND

Dual mobility (DM) bearings are increasingly popular and second-generation designs contain highly cross-linked polyethylene. The purpose of this study is to report head penetration rates in modern DM bearings.

METHODS

A review of 63 consecutive DM bearings was performed. Radiographs were analyzed for head penetration using Martell methodology at regular postoperative intervals.

RESULTS

Thirty-four DM bearings were analyzed. Mean linear head penetration was 1.59 mm/y at 1 year, 1.07 mm/y at 2 years, and 0.27 mm/y at 5 years following an exponential regression model (R² = 0.999). Mean volumetric wear was 783 mm³/y at 1 year, 555 mm³/y at 2 years, and 104 mm³/y at 5 years following an exponential regression model (R² = 0.986).

CONCLUSION

Initial head penetration of DM bearings is larger than contemporary cross-linked polyethylene bearings; however, rates approach steady state after 2 years, analogous to traditional bearings. The larger "bedding-in" head penetration may be due to the additional convex bearing surface, creating 2 surfaces for deformation/wear.

Which is the best bearing surface for primary total hip replacement? A New Zealand Joint Registry study

INTRODUCTION

We have investigated the revision rates of all bearing surface combinations for primary total hip replacement (THR) registered on the New Zealand Joint Registry (NZJR) to determine which coupling has been the most durable and successful over the last 16 years.

METHODS

There were 106,139 primary THRs registered, resulting in 4,960 revisions for any cause. We examined all-cause revision rates, reasons for revision and performed survival analyses.

RESULTS

Ceramic-on-highly cross-linked polyethylene (CoPx) had the lowest all-cause revision rate of 0.54/100-component-years (cys) (95% confidence interval 0.48 to 0.61). This was superior to all other hard-on-soft bearing combinations in unadjusted analysis. Furthermore, the age of patients receiving CoPx was significantly lower than for metal-on-polyethylene (mean 62.9; standard deviation [SD] 10.1 vs. 69.1; SD 9.6; p<0.001). Acetabular loosening was the reason for revision in 14.5% of CoPx, compared to 33% of MoP THRs (p<0.001). Metal-on-metal bearings had the highest revision rate of 1.43/100 cys and were significantly inferior to CoPx (p<0.001). Kaplan-Meier analysis and Cox regression analyses were performed and we adjusted the analyses to control for age, femoral head size, surgical approach and fixation.

CONCLUSIONS

CoPx remained the most durable and successful coupling used in primary THR in New Zealand irrespective of age, gender or size of femoral head.

The influence of early radiolucent lines appearing on femoral head penetration into HXLPE cemented sockets

INTRODUCTION

This study investigates differences in femoral head penetration between highly cross-linked polyethylene (HXLPE) cemented sockets both with and without radiolucent lines (RLLs) in the early postoperative phase and at 5 years follow-up.

METHODS

There were 35 patients (37 hips), mean age of 66.8 years, who underwent total hip arthroplasty (THA) using highly HXLPE cemented sockets. They were divided into 2 groups based on postoperative the early appearance of RLLs. Femoral head penetrations on both anteroposterior- and Lauenstein-view radiographs were evaluated, and the mean polyethylene (PE) wear rate was calculated based on femoral head penetrations between 2 and 5 years.

RESULTS

Femoral head penetrations in the proximal direction were 0.075 mm and 0.150 mm in the RLL and non-RLL groups at 1 year postoperatively ( p = 0.019). At 5 years measured penetration was 0.107 mm and 0.125 mm in the RLL and non-RLL groups, respectively ( p = 0.320). The mean PE wear rates in anteroposterior-view were 0.008 mm/year and 0.003 mm/year in the RLL and non-RLL groups ( p = 0.390) and those in Lauenstein-view were 0.010 mm/year and 0.005 mm/year, respectively ( p = 0.239).

CONCLUSIONS

In the RLL group, the PE bedding-in was less compared with those in the non-RLL group. Additionally, the mean PE wear rate in the RLL group tended to be higher than that in the non-RLL group. The distribution of stress loading through the cement may differ according to whether early RLLs appear.

A long-term comparative study between two different designs of cemented stems: Distal-cylindrical versus distal-taper

Introduction

The aim of this study was to calculate the wear rate of highly cross-linked polyethylene (HXLPE) and investigate long-term clinical and radiographic outcomes related to two femoral stem designs, the distal-cylindrical (DC) and distal-taper (DT) stems.

Materials and methods

Outcomes for the DC and DT stems were evaluated in 110 patients, who underwent total hip arthroplasty using an HXLPE socket, over a 5-year follow-up period. There were 56 hips (53 patients) in the DC group and 60 hips (57 patients) in the DT group. Clinical outcomes were measured using the Japanese Orthopaedic Association (JOA) score and radiographic changes. Polyethylene wear rate was calculated using a computer software.

Results

The mean follow-up period was 135.7 and 124.0 months for the DC and DT groups, respectively. Both stem designs improved hip function. On radiographic assessment, osteolysis around the tip of the stem was more frequent in the DC than in the DT group. Three cases of aseptic loosening of the stem were identified in the DC group, and no cases were identified in the DT group. The 10-year stem survival, using aseptic loosening as the primary endpoint, was 94.1% and 100% for the DC and DT groups, respectively (p = 0.06). The polyethylene wear rate was comparable for both stem groups.

Conclusion

Better clinical outcomes were obtained with the DT stem than with the DC stem regardless of the equivalent polyethylene wear rate for the two designs. The DC shape of the stem may increase the risk of aseptic loosening.

Bearing Surfaces for Total Hip Arthroplasty

Metal-on-highly cross-linked polyethylene is considered the preferred bearing surface for conventional total hip arthroplasty because of its safety profile and excellent results in the first 10 to 15 years of use. However, with younger patient age, activity expectations increase, and the life expectancy of patients with total hip arthroplasty also has increased, so interest remains in other bearing couples. These other options include the use of various ceramic composites for the femoral head on highly cross-linked polyethylene, the so-called second-generation antioxidant polyethylenes, and ceramic acetabular liners. Several of these bearing couples have shown excellent wear rates in vitro, and short-term clinical studies have demonstrated favorable wear and safety results. It is uncertain whether any of these bearing couples should be adopted at present. Understanding the unique properties and possible complications of these bearing couples is critical for appropriate implant selection.

Polyethylene and highly cross-linked polyethylene for cemented total hip arthroplasty: A comparison of over ten-year clinical and radiographic results

INTRODUCTION

We investigated the long-term tribological outcomes of conventional polyethylene (CPE) and highly cross-linked polyethylene (HXLPE).

METHODS

Ninety-four consecutive primary cemented THAs were performed using either HXLPE or CPE at our hospital. CPE sockets were used in 26 hips, and HXLPE sockets were implanted in 68 hips.

RESULTS

A 10-year follow-up was completed for 69 cases. Linear wear rates of 0.138 ± 0.074 mm/year for CPE and 0.011 ± 0.020 mm/year for HXLPE were calculated. Osteolysis was identified in 10 cases (CPE group, 7; HXLPE group, 3).

CONCLUSION

HXLPE had significantly less wear than CPE, and polyethylene wear was associated with osteolysis.

Highly Cross-Linked Polyethylene Reduces Osteolysis Incidence and Wear-Related Reoperation Rate in Cementless Total Hip Arthroplasty Compared With Conventional Polyethylene at a Mean 12-Year Follow-Up

BACKGROUND

A number of studies on total hip arthroplasty have compared highly cross-linked polyethylene (HXLPE) with conventional polyethylene (CPE) liners beyond 10 years. However, the impact of HXLPE on the wear-related reoperation rate is unclear. The purpose of this study was to evaluate the clinical advantage of using a single manufacturer's HXLPE in terms of reducing the reoperation rate.

METHODS

The study was a follow-up retrospective cohort study over a mean of 12 years that examined patients aged 45-70 years with cementless total hip arthroplasty using a 26-mm-diameter cobalt-chromium head. Sixty-seven patients (79 hips; HXLPE group = 41 hips, CPE group = 38 hips) were evaluated for a minimum 10-year follow-up. Kaplan-Meier survival analysis was performed, with wear-related reoperations and radiographic osteolysis serving as the end points. The polyethylene wear rate was also assessed.

RESULTS

The mean 12-year follow-up rates of survivorship that were evaluated using wear-related reoperations as the end point were 100% and 91.4% in the HXLPE and CPE groups, respectively (P = .007), and the mean 12-year follow-up rates of survivorship with osteolysis as the end point were 100% and 36.2%, respectively (P < .001). Compared with the CPE group, the HXLPE group presented a significantly reduced wear rate (HXLPE group, 0.035 mm/y; CPE group, 0.118 mm/y).

CONCLUSION

A unique strength of this study is that we assessed a single manufacturer's HXLPE while keeping most other implant parameters uniform. This study reveals the clinical advantage of using a single manufacturer's HXLPE in terms of a reduced wear-related reoperation rate at a mean 12-year follow-up.

Differences in Femoral Head Penetration Between Highly Cross-Linked Polyethylene Cemented Sockets and Uncemented Liners

BACKGROUND

This study aimed at investigating differences in femoral head penetration between highly cross-linked polyethylene (HXLPE) cemented sockets and uncemented liners during 5 years postoperatively.

METHODS

Ninety-six patients (106 hips) with a mean age of 64.4 (range, 35-83) years underwent total hip arthroplasty using a HXLPE cemented socket or liner and were respectively divided into cemented (35 patients [37 hips]) and uncemented (61 patients [69 hips]) groups. Femoral head penetrations were evaluated on both anteroposterior (AP)-view and Lauenstein-view radiographs, and mean polyethylene (PE) wear rates were calculated based on femoral head penetration from 2 to 5 years. Multivariate analyses were performed to assess risk factors for PE wear.

RESULTS

At 5 years postoperatively, the cemented and uncemented groups exhibited proximal direction femoral head penetrations of 0.103 mm and 0.124 mm (P = .226) and anterior direction penetrations of 0.090 mm and 0.151 mm (P = .002), respectively. The corresponding mean PE wear rates were 0.004 mm/y and 0.009 mm/y in the AP-view (P = .286) and 0.005 mm/y and 0.012 mm/y in the Lauenstein-view (P = .168), respectively. Left-side operation and high activity were independent risk factors for PE wear on AP-view.

CONCLUSION

When HXLPE was used, all mean PE wear rates were very low and those of cemented sockets and uncemented liners were very similar. PE particle theory suggests that the occurrence of osteolysis and related aseptic loosening might consequently decrease.

Highly Cross-Linked Polyethylene Reduces Wear and Revision Rates in Total Hip Arthroplasty: A 10-Year Double-Blinded Randomized Controlled Trial

BACKGROUND

Highly cross-linked polyethylene (XLPE) was developed to address the problem of wear and osteolysis associated with metal-on-conventional ultra-high molecular weight polyethylene (UHMWPE) bearing surfaces. The purpose of this study was to compare in vivo wear rates and clinical and radiographic outcomes between XLPE and UHMWPE in a prospective double-blinded randomized controlled trial with a minimum of 10 years of follow-up.

METHODS

We randomized 122 patients to receive either a conventional UHMWPE liner (Enduron; DePuy) or an XLPE liner (Marathon; DePuy). Ninety-one patients were assessed clinically and radiographically at a minimum of 10 years (range, 10.08 to 12.17 years). Oxford Hip Scores and Short Form-12 Health Survey scores were collected. The radiographs were analyzed for osteolysis and for 2-dimensional (2-D), 3-dimensional (3-D), and volumetric wear using validated software.

RESULTS

All 122 patients were accounted for at the 10-year follow-up evaluation. Twelve patients had undergone revision surgery, 21 patients had died (1 of whom had previously undergone revision surgery), and 2 patients were unable to return for follow-up, leaving 91 patients available for clinical and radiographic evaluation. At a minimum of 10 years, 3-D wear rates were significantly lower (p < 0.001) in the XLPE group (mean, 0.03 mm/yr) than in the conventional UHMWPE group (mean, 0.27 mm/yr). The prevalence of osteolysis was also significantly lower in the XLPE group (38% versus 8%, p < 0.005), as was the revision rate (14.6% versus 1.9%, p = 0.012), with 10 of the 12 revisions being in the Enduron group. There was no significant difference between the clinical scores of the 2 groups.

CONCLUSIONS

XLPE liners have significantly reduced wear and are associated with a greater implant survival rate at 10 years compared with conventional UHMWPE liners.

LEVEL OF EVIDENCE

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

A 28-year clinical and radiological follow-up of alumina ceramic-on-crosslinked polyethylene total hip arthroplasty: a follow-up report and analysis of the oxidation of a shelf-aged acetabular component

AIMS

Our aim in this study was to describe a continuing review of 11 total hip arthroplasties using 22.225 mm Alumina ceramic femoral heads on a Charnley flanged femoral component, articulating against a silane crosslinked polyethylene.

PATIENTS AND METHODS

Nine patients (11 THAs) were reviewed at a mean of 27.5 years (26 to 28) post-operatively. Outcome was assessed using the d'Aubigne and Postel, and Charnley scores and penetration was recorded on radiographs. In addition, the oxidation of a 29-year-old shelf-aged acetabular component was analysed.

RESULTS

The mean clinical outcome scores remained excellent at final follow-up. The mean total penetration remained 0.41 mm (0.40 to 0.41). There was no radiographic evidence of acetabular or femoral loosening or osteolysis. There was negligible oxidation in the shelf-aged sample despite gamma irradiation and storage in air.

CONCLUSION

These results highlight the long-term stability and durability of this type of crosslinked, antioxidant containing polyethylene when used in combination with a small diameter alumina ceramic femoral head. Cite this article: Bone Joint J 2017;99-B:1286-9.

Polyethylene and highly cross-linked polyethylene for cemented total hip arthroplasty: A comparison of over ten-year clinical and radiographic results

INTRODUCTION

We investigated the long-term tribological outcomes of conventional polyethylene (CPE) and highly cross-linked polyethylene (HXLPE).

METHODS

Ninety-four consecutive primary cemented THAs were performed using either HXLPE or CPE at our hospital. CPE sockets were used in 26 hips, and HXLPE sockets were implanted in 68 hips.

RESULTS

A 10-year follow-up was completed for 69 cases. Linear wear rates of 0.138 ± 0.074 mm/year for CPE and 0.011 ± 0.020 mm/year for HXLPE were calculated. Osteolysis was identified in 10 cases (CPE group, 7; HXLPE group, 3).

CONCLUSION

HXLPE had significantly less wear than CPE, and polyethylene wear was associated with osteolysis.

Outcome in design-specific comparisons between highly crosslinked and conventional polyethylene in total hip arthroplasty

Background and purpose - Most registry studies regarding highly crosslinked polyethylene (XLPE) have focused on the overall revision risk. We compared the risk of cup and/or liner revision for specific cup and liner designs made of either XLPE or conventional polyethylene (CPE), regarding revision for any reason and revision due to aseptic loosening and/or osteolysis. Patients and methods - Using the Nordic Arthroplasty Register Association (NARA) database, we identified cup and liner designs where either XLPE or CPE had been used in more than 500 THAs performed for primary hip osteoarthritis. We assessed risk of revision for any reason and for aseptic loosening using Cox regression adjusted for age, sex, femoral head material and size, surgical approach, stem fixation, and presence of hydroxyapatite coating (uncemented cups). Results - The CPE version of the ZCA cup had a risk of revision for any reason similar to that of the XLPE version (p = 0.09), but showed a 6-fold higher risk of revision for aseptic loosening (p < 0.001). The CPE version of the Reflection All Poly cup had an 8-fold elevated risk of revision for any reason (p < 0.001) and a 5-fold increased risk of revision for aseptic loosening (p < 0.001). The Charnley Elite Ogee/Marathon cup and the Trilogy cup did not show such differences. Interpretation - Whether XLPE has any advantage over CPE regarding revision risk may depend on the properties of the polyethylene materials being compared, as well as the respective cup designs, fixation type, and follow-up times. Further research is needed to elucidate how cup design factors interact with polyethylene type to affect the risk of revision.

Ten-Year Cross-Sectional Study of Mechanically Assisted Crevice Corrosion in 1352 Consecutive Patients With Metal-on-Polyethylene Total Hip Arthroplasty

BACKGROUND

Mechanically assisted crevice corrosion (MACC) in metal-on-polyethylene total hip arthroplasty (THA) is of concern, but its prevalence, etiology, and natural history are incompletely understood.

METHODS

From January 2003 to December 2012, 1352 consecutive THA surgeries using a titanium stem, cobalt-chromium alloy femoral head, and highly cross-linked polyethylene liner from a single manufacturer were performed. Patients were followed at 1-year and 5-year intervals for surveillance, but also seen earlier if they had symptoms. Any patient with osteolysis >1 cm (n = 3) or unexplained pain (n = 85) underwent examination, radiographs, complete blood count, erythrocyte sedimentation rate, and C-reactive protein, as well as tests for serum cobalt and chromium levels.

RESULTS

Symptomatic MACC was present in 43 of 1352 patients (3.2%). Prevalence of MACC by year of implant ranged from 0% (0 of 61, 2003; 0 of 138, 2005) to 10.5% (17 of 162; 2009). The M/L Taper stem had a greater prevalence (4.9%) of MACC than all other Zimmer (Zimmer, Inc, Warsaw, IN) 12/14 trunnion stem types combined (1.2%; P < .001). Twenty-seven of 43 (62.8%) patients have undergone revision surgery, and 16 of 43 (37.2%) patients have opted for ongoing surveillance. Comparing symptomatic THA patients with and without MACC, no demographic, clinical, or radiographic differences were found. MACC was significantly more common in 0 length femoral heads (compared with both -3.5 mm and +3.5 mm heads).

CONCLUSION

The prevalence of MACC in metal-on-polyethylene hips is higher in this cross-sectional study than previously reported. A significantly higher prevalence was found in patients with M/L Taper style stem and THA performed both in 2009 and also between 2009 and 2012 with this manufacturer.

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

AIMS

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Validation of a new 2-D technique for radiographic wear measurement of cemented, highly cross-linked polyethylene acetabular cups

•

Mean wear penetration error of the system was −0.002 mm and the precision was 0.055 mm

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Above 0.25 mm penetration, wear direction error was within ±10° (median 1.15°)

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Good inter/intra observer agreement for clinical radiographs

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Penetration error equal to that of RSA for laboratory radiographs

A new 2-D radiographic wear measurement system has been developed which enables the low wear of highly cross-linked polyethylene acetabular cups to be accurately and precisely measured from standard, pelvis radiographs. The software was validated using radiographic images of a measurement jig which could vary the cup orientation and simulate the effect of pelvic tilt/rotation. Wear was simulated using accurately measured plastic shims to vary the position of the femoral head relative to the cup. The effects of varying “wear” penetration, “wear” direction, cup orientation and X-ray focus position were assessed. Further direct comparison tests were also carried out using radiostereometric analysis. Inter/intra-observer repeatability of the new system was assessed using clinical radiographs.

The mean (SD) “wear” penetration error was -0.002 mm (0.028 mm). The “wear” penetration precision was 0.055 mm. Changing the position of the X-ray focus point made no difference to the measurement error. Inter/intra-observer repeatability and limits of agreement had similar low values. Comparison tests with RSA showed the accuracy was similar.

The Relationship Between Polyethylene Wear and Periprosthetic Osteolysis in Total Hip Arthroplasty at 12 Years in a Randomized Controlled Trial Cohort

BACKGROUND

Polyethylene acetabular components are common in hip arthroplasty. Highly cross-linked polyethylene (HXLPE) has lower wear than ultra-high molecular weight polyethylene (UHMWPE). Evidence suggests that wear particles induce inflammation causing periprosthetic osteolysis contributing to implant loosening with wear rates of 0.05 mm/y were considered safe. We aimed to compare incidence and volume of periacetabular osteolysis between HXLPE and UHMWPE using computed tomography.

METHODS

Initially, 54 hips in 53 patients were randomized to HXLPE or UHMWPE acetabular liner. At 10 years, 39 hips in 38 patients remained for the radiostereometric analysis' demonstrating significantly lower wear in the HXLPE group. At 12 years, 14 hips in 13 patients were lost to follow-up leaving 25 hips for computed tomography assessment. Images were reconstructed to detect osteolysis and where identified, areas were segmented and volumized.

RESULTS

Osteolysis was observed in 8 patients, 7 from the UHMWPE group and only 1 from the HXLPE group (Fisher exact, P = .042). There was no correlation between the amount of polyethylene wear and osteolysis volume; however, the radiostereometric analysis-measured wear rate in patients with osteolysis from both groups was significantly higher than overall average wear rate.

CONCLUSION

This data demonstrates lower incidence of periacetabular osteolysis in the HXLPE group of a small cohort. Although numbers are too low to estimate causation, in the context of lower wear in the HXLPE group, this finding supports the hypothesis that HXLPE may not elevate osteolysis risk, and hence does not suggest that HXLPE wear particles are more biologically active than those generated by earlier generations of polyethylene.

Fifteen-Year Comparison of Wear and Osteolysis Analysis for Cross-Linked or Conventional Polyethylene in Cementless Total Hip Arthroplasty for Hip Dysplasia-A Retrospective Cohort Study

BACKGROUND

Cross-linked polyethylene (XLPE) acetabular liners used in cementless total hip arthroplasty (THA) have demonstrated better wear resistance at 10 years compared with conventional polyethylene (CPE) liners. No clinical studies have compared XPLE to CPE liners beyond 10 years.

METHODS

We performed a 15-year retrospective cohort study on cementless THA performed in patients with developmental hip dysplasia to measure the differences in polyethylene wear rates and the presence of osteolysis. Twenty-four THAs with XLPE and 17 THAs with CPE were evaluated. The mean age of patients was 55.9 years (41-68) in the XLPE group and 54.4 years (40-67) in the CPE group. The mean follow-up period was 15.1 years (13.9-16.1) in the XLPE group and 15.2 years (14.5-16.0) in the CPE group.

RESULTS

The XLPE group had a significantly lower wear rate at 5 and 10 years compared with the CPE group; however, no significant difference was found at 15 years (XLPE group, 0.040 mm/y; CPE group, 0.034 mm/y). In addition, the incidence of osteolysis did not differ significantly between the groups. However, the incidence of excessive wear between 10 and 15 years after surgery in the XLPE group was significantly higher than that in the CPE group.

CONCLUSION

XLPE demonstrated no advantage in the wear rate or the incidence of osteolysis at 15 years, despite having superior wear resistance up to 10 years. It is concerning that the incidence of excessive wear was higher in the XLPE group between 10 and 15 years, and this finding should alert the arthroplasty community to this possible problem with the more highly cross-linked polyethylene.

Comparison of Polyethylene Wear before and after Hip Revision with Liner Exchange Fixed with the Original Locking Mechanism

Objective

To compare the wear of conventional ultra-high molecular weight polyethylene (CUHMWPE) and highly cross-linked polyethylene (HCLPE) in hip revision with liner exchange fixed with original locking mechanism using analysis of history medical data.

Methods

From Jan. 1, 2000, to Dec. 31, 2007, 26 patients (with 29 involved hips) underwent liner exchange revision fixed with the original locking mechanism due to wear of CUHMWPE and/or osteolysis. The mean age was 53 ± 9 years at the time of the primary total hip arthroplasty (THA) and 64 ± 9 years at the revision. The exchanged liners (Marathon, Depuy) were made of HCLPE. Annual X-rays were used to measure linear wear and osteolysis. The annual linear penetration was measured using PolyWare® software (Draftware Inc.). Annual Harris Hip Scores(HSS) were recorded.

Results

The mean follow-up time between the primary and revision THAs was 11 ± 2 years and 8 ± 2 years after revision. The mean Harris Hip Score(HHS) before primary THA, 1 year after primary THA, before revision and 1 year after revision was 43±5, 85±5, 71±6, 83±7 individually. The mean penetration of the CUHMWPE and HCLPE liners occurring in the first year were 0.44 ± 0.28 mm and 0.38 ± 0.14 mm, respectively (p = 0.211). The mean annual linear penetration of CUHMWPE and HCLPE from the second year onward were 0.29±0.09 mm and 0.08 ± 0.03 mm respectively (p <0.01). All THAs with CUHMWPE showed osteolysis on acetabular and/or femoral side before revision. No HCLPE liner showed osteolysis at the last follow-up. Conclusion: The CUHMWPE liner had a significantly higher wear rate than did the HCLPE liner. The HCLPE liner showed a satisfactory liner penetration rate after revision with isolated liner exchange fixed with the original locking mechanism.

Thirteen-Year Evaluation of Highly Cross-Linked Polyethylene Articulating With Either 28-mm or 36-mm Femoral Heads Using Radiostereometric Analysis and Computerized Tomography

BACKGROUND

The objective of this 13-year prospective evaluation of highly cross-linked ultra high molecular weight polyethylene (HXLPE) was to (1) assess the long-term wear of HXLPE articulating with 2 femoral head sizes using radiostereometric analysis (RSA) and to (2) determine if osteolysis is a concern with this material through the use of plain radiographs and computerized tomography (CT).

METHODS

All patients received a Longevity HXLPE liner with tantalum beads and either a 28-mm or 36-mm femoral head. Twelve patients (6 in each head size group) agreed to return for 13-year RSA, plain radiograph, and CT follow-up. The 1-year and 13-year plain radiographs as well as the CT scans were analyzed for the presence of osteolysis.

RESULTS

The 13-year mean ± standard error steady-state wear was 0.05 ± 0.02 mm with no significant increase over time or between the 2 head size groups. Two patients' CT scans showed radiolucent regions in the acetabulum of 4.51 cm(3) and 11.25 cm(3), respectively. In one patient, this area corresponded to a partially healed degenerative cyst treated with autograft during surgery. The second patient had an acetabular protrusio treated with autograft, and the CT scan revealed areas of remodeling of this graft. One patient's 13-year plain radiographs showed evidence of cup loosening and linear radiolucencies in zones 2 and 3.

CONCLUSION

There was no evidence of significant wear over time using RSA. The CT scans did not show evidence of osteolysis due to wear particles. These results suggest that this material has reduced wear compared to conventional polyethylene, irrespective of head size.

Highly Cross-linked Polyethylene Provides Decreased Osteolysis and Reoperation at Minimum 10-Year Follow-Up

BACKGROUND

Highly cross-linked polyethylene was introduced to decrease periprosthetic osteolysis and reoperation, but this has not been conclusively proven.

METHODS

One surgeon performed 513 consecutive primary total hip arthroplasties (450 patients) using 1 modern, cementless, titanium-mesh acetabular component with screw fixation. This study analyzed the differences in the rate of reoperation and incidence of osteolysis between 133 hips with standard and 112 hips with highly cross-linked polyethylene at minimum 10-year follow-up time.

RESULTS

Of the entire cohort of 513 hips, no acetabular component was removed or revised for aseptic loosening. There were significantly more reoperations in the cohort with standard polyethylene (11 of 133, 8%) than highly cross-linked polyethylene (1 of 112, 1%; P = .03). Osteolysis was seen in 24% (32 of 133 hips) with standard polyethylene, compared with 13% (15 of 112 hips) with highly cross-linked polyethylene (P = .02). These differences occurred despite the presence of patients with greater BMI and higher activity in the cohort with highly cross-linked polyethylene.

CONCLUSION

We continue to use this acetabular component with highly cross-linked polyethylene. Longer follow-up is required to determine the progression of osteolysis.

The study of wear behaviors on abducted hip joint prostheses by an alternate finite element approach

An acetabular cup with larger abduction angles is able to affect the normal function of the cup seriously that may cause early failure of the total hip replacement (THR). Complexity of the finite element (FE) simulation in the wear analysis of the THR is usually concerned with the contact status, the computational effort, and the possible divergence of results, which become more difficult on THRs with larger cup abduction angles. In the study, we propose a FE approach with contact transformation that offers less computational effort. Related procedures, such as Lagrangian Multiplier, partitioned matrix inversion, detection of contact forces, continuity of contact surface, nodal area estimation, etc. are explained in this report. Through the transformed methodology, the computer round-off error is tremendously reduced and the embedded repetitive procedure can be processed precisely and quickly. Here, wear behaviors of THR with various abduction angles are investigated. The most commonly used combination, i.e., metal-on-polyethylene, is adopted in the current study where a cobalt-chromium femoral head is paired with an Ultra High Molecular Weight Polyethylene (UHMWPE) cup. In all illustrations, wear coefficients are estimated by self-averaging strategy with available experimental datum reported elsewhere. The results reveal that the THR with larger abduction angles may produce deeper depth of wear but the volume of wear presents an opposite tendency; these results are comparable with clinical and experimental reports. The current approach can be widely applied easily to fields such as the study of the wear behaviors on ante-version, impingement, and time-dependent behaviors of prostheses etc.