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.

Theoretical study on the grafting reaction of maleimide containing 2-hydroxy-benzophenone onto polyethylene

A theoretical study on the multi-channel hydrogen addition of maleimide containing 2-hydroxy-benzophenone onto polyethylene in ultra-violet (UV) radiation cross-linking process was carried out using density functional theory (DFT) method at the B3LYP/6-311 + G(d,p) level. The energetic information and the minimum energy path (MEP) are calculated for nine reaction channels. The electrophilic addition reactions at two positions in the target molecule (maleimide containing 2-hydroxy-benzophenone) were investigated, which are on the C atom of C = C groups and on the O atom of C = O groups. Frontier molecular orbitals (MOs) and natural bond orbital (NBO) charge population of the target molecule have been analyzed in detail. As a result, the reaction site of C in C = C group is more active than the site of O in C = O groups. The target molecule can be used as a multi-functional additive candidate. The predicted mechanism may provide a theoretical basis for the real application of cross-linked polyethylene (XLPE) high-voltage insulation cables.

Different wear in two highly cross-linked polyethylene liners in THA: wear analysis with EBRA

INTRODUCTION

The purpose of this study was (1) to compare early wear rates in bedding-in periods of two highly cross-linked polyethylene liners frequently used in THA and (2) to evaluate risk factors indicating a possible higher wear rate.

MATERIALS AND METHODS

1120 patients who received a Crossfire or a Marathon highly cross-linked (HXLPE) ultra-high-molecular-weight polyethylene liner in primary THA at our Department between 2004 and 2018 were retrospectively reviewed. Patients with (1) only alumina heads on HXLPE acetabular bearings, (2) a minimum of four radiographs per patient for EBRA analysis, (3) no osteolysis around the acetabular cup and (4) no dislocations that occurred during the study period were included.

RESULTS

A total of 328 patients (female: 183; male: 145; Marathon: 179; Crossfire: 149) fulfilled the inclusion criteria. Mean follow-up was 24 (range 7-51) months. With 0.22 (SD 0.27) mm mean total wear for the Marathon was three times greater than for the Crossfire, namely 0.07 (SD 0.14) mm. Mean cup migration during the investigated follow-up period was 0.7 (SD 0.8) mm for the Pinnacle and 0.5 mm (SD 0.7) for the Trident PSL cups.

CONCLUSION

Initial early wear of highly cross-linked polyethylene in combination with alumina heads differs strongly between products. Long-term survivorship of these liners should be observed to determine whether early wear has an impact on aseptic loosening.

LEVEL OF EVIDENCE

Level III (retrospective comparative study with prospective cohort).

Third-Generation Medium Cross-Linked Polyethylene Demonstrates Very Low Wear in Total Hip Arthroplasty

Background

Cross-linked polyethylene (XLPE) liners have shown lower wear rates than conventional polyethylene liners in total hip arthroplasty. The primary aim of our study was to report our most recent analysis of wear rates and clinical outcomes of a third-generation XLPE liner. Secondary aims were to investigate the rate of adverse events related to mechanical failure or oxidation of this liner.

Methods

A series of 266 total hip arthroplasties using a specific XLPE liner were retrospectively reviewed. Radiographs were examined to determine linear and volumetric wear rates and presence of osteolysis. Clinical outcomes, revision rates, mechanical failures, and risk factors for accelerated polyethylene wear were additionally investigated.

Results

The mean age at the time of surgery was 65.8 years and the mean follow-up was 5.5 years. The mean linear wear rate was 0.003 mm/year and the mean volumetric wear rate was 0.42 mm³/year, and there was no evidence of osteolysis. Harris hip scores increased from 50.9 preoperatively to 96.0 at the latest follow-up. The revision rate was 0.4%, with no liner rim fractures and no liner dissociations/loosenings. Femoral head material, head size, age, body mass index, and time since implantation had no effect on wear rates.

Conclusion

Wear rates for this third-generation XLPE liner were low at mid-term follow-up, and no adverse sequelae of oxidation or deleterious mechanical properties were observed. This remained true regardless of femoral head size and material or patient age and body mass index. Further analysis will be necessary to ensure continued wear resistance, oxidative stability, and mechanical strength at long-term follow-up.

Electrical tree inhibition by SiO2/XLPE nanocomposites: insights from first-principles calculations

It has been extensively observed in experiments that nanoparticle additives can efficiently inhibit the electrical tree growth of the cross-linked polyethylene (XLPE) matrix of power cables. Inspired by this, the first-principles calculations employing the density functional theory (DFT) method were performed in this study to investigate the significant role of SiO₂ nanosized fillers as a voltage stabilizer for power cable insulation. Several different types of α-SiO₂ fillers, including hydroxylated, reconstructed, doped or oxygen vacancy surface structures, were constructed to model the interfacial interaction for SiO₂/XLPE nanocomposites. It is found that the SiO₂ additives can restrict the movement of the polyethylene chain through van der Waals physical interaction. More importantly, based on the Bader charge analysis we reveal that SiO₂ could effectively capture hot electrons to suppress space charge accumulation in XLPE. However, some particular modified-surface SiO₂, such as incompletely hydroxylated, B-doped, and oxygen vacancy defect on the top layer, could induce the H migration reaction and consequent electrical tree growth of the XLPE chain. In contrast, the SiO₂ particles that have N-doped or oxygen vacancy on the lower layer with completely hydroxylated surfaces, as well as the reconstructed surface, are predicted to be favorable additives because of their quite strong physical interaction and very weak chemical activity with XLPE. The present study is useful to understand the mechanism of the nanosized voltage stabilizer and also provide important information for further experimental investigation.

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

BACKGROUND

There is no previous report that directly compared wear resistance of second-generation annealed highly cross-linked polyethylene with that of first-generation remelted highly cross-linked polyethylene. We therefore performed a retrospective study at a minimum of 5-year follow-up comparing second-generation annealed and first-generation remelted highly cross-linked polyethylene in order to: (1) assess wear rates and (2) compare the incidence of osteolysis between, (3) identify the frequency of complication related to the two types of highly cross-linked polyethylene.

HYPOTHESIS

There is a difference in the linear wear rate and the incidence of osteolysis between the two types of highly cross-linked polyethylene in total hip arthroplasty.

MATERIALS AND METHODS

In a single centre study, we reviewed 123 primary cementless total hip arthroplasties between 2010 and 2011 that were performed with 32mm alumina ceramic on second-generation annealed (X3) or first-generation remelted (Longevity) highly cross-linked polyethylene liner. There was no specific reason for the choice of the type of highly cross-linked polyethylene. There were no significant differences between the two groups in respect of gender, diagnosis, body mass index, pre- and post-operative functional and activity score, cup size, and cup orientation except the younger age in the X3 group. The mean wear rate and the incidence of osteolysis were evaluated at the latest follow-up.

RESULTS

One hundred nine cases followed over 5 years post-operatively (88.6% in all consecutive cases) were evaluated. X3 and Longevity were used in 54 and 55 cases, respectively. The mean follow-up was 5.3 years in both groups. The mean linear wear rate of X3 and Longevity group was 0.045±0.023mm/year and 0.076±0.031mm/year, respectively (P<0.001). No osteolysis was found on plain X-rays in both groups and no specific complication was related to these highly cross-linked components.

DISCUSSION

Excellent wear resistance of both types of highly cross-linked polyethylene liner was revealed in our study. The difference of wear rate between two materials should be monitored in a longer follow-up.

LEVEL OF EVIDENCE

Level III retrospective case control study.

Single-sided Nuclear Magnetic Resonance for condition monitoring of cross-linked polyethylene exposed to aggressive media

The potential of single-sided Nuclear Magnetic Resonance (NMR) to monitor truly non-invasive changes in polymer materials during aging under aggressive media is for the first time evaluated. For this, the NMR method is used in combination with other condition monitoring methods including mechanical measurements, mass uptake, and differential scanning calorimetry. It is validated by studying for the first time the aging kinetics of silane cross-linked polyethylene (PEX) exposed to media used in oil and gas production and transportation, including aliphatic and aromatic hydrocarbons, sulphur solvents, and corrosion inhibitors in combination with CO2 and H2S. All investigated parameters changed, with the strongest effects detected for the NMR chain mobility and in the presence of hydrocarbons. Furthermore, a universal linear correlation curve could be established between the depression of the tensile strength and the chain mobility. This result represents a fundamental step towards establishing single-sided NMR as a new analytical tool for in situ condition monitoring of polyethylene working under sour conditions. The proposed approach can be easily extended to other polymer materials.