What factors drive polyethylene wear in total knee arthroplasty? : results of a large retrieval series

Is Wear Still a Concern in Total Knee Arthroplasty With Contemporary Conventional and Highly Crosslinked Polyethylene Tibial Inserts in the mid- to Long-Term?

Background

Modern literature has brought into question if wear of tibial inserts made from conventional or highly crosslinked polyethylene (HXL PE) is still a factor limiting longevity of total knee arthroplasty (TKA) in the mid- to long-term. It is the objective of this study to determine: 1) most common causes of mid- to long-term TKA failure, 2) the prevalence of delamination, and 3) the medial/lateral linear wear rates of conventional and HXL PE tibial inserts retrieved in the mid- to long-term.

Methods

A tibial insert retrieval cohort of 107 inserts (79 conventional, 28 HXL PE) with a minimum time in situ of 6.5 years (mean 11.7 ± 4) was studied. Failure causes were determined from chart-review, delamination presence was assessed microscopically, and medial/lateral linear wear was determined by minimal thickness changes measured with a dial-indicator.

Results

The most common mid-to long-term etiologies for failure were instability (44.9%), PE wear 15%), aseptic loosening (14%), and infection (13.1%). Delamination occurred in 70% of inserts (72.1% conventional, 64.3% HXLPE). Gross material loss due to delamination appeared to be the underlying reason for at least 33.3% of cases exhibiting instability. Of the cases removed for infection, 75% exhibited no histopathological hallmarks of acute infection. The medial/lateral wear rates were 0.054/0.051 (conventional) and 0.014/0.011 (HXL) mm/y, respectively.

Conclusions

Polyethylene wear still appears to be a major primary and secondary cause for TKA revision in the mid- to long-term. Wear may manifest as destabilizing delamination or as continuous release of fine wear particles potentially resulting in inflammatory responses and subsequent failure.

Diffusion doping of analgesics into UHMWPE for prophylactic pain management

Pain management after total joint arthroplasty is often addressed by systemic delivery of opioids. Local delivery of non-opioid analgesic drugs directly in the joint space from the UHMWPE component of the prosthesis would be highly beneficial to increase the efficacy of the drugs, decreasing the overall side effects and the risk of opioid addiction. It has been shown that effective concentrations of local analgesics can be achieved by eluting from analgesic-blended UHMWPE; however, this approach is limited by the decrease in mechanical properties resulting from the extent of phase separation of the blended drugs from the polymeric matrix. Here we hypothesized that mechanical properties could be maintained by incorporating analgesics into solid form UHMWPE by diffusion as an alternative method. Lidocaine or bupivacaine were diffused in solid form UHMWPE with or without radiation crosslinking. The loaded drug content, the spatial distribution of the drugs and their chemical stability after doping were characterized by FTIR and NMR spectroscopy, respectively. Drug release kinetics, tensile mechanical properties and wear rates were assessed. The results showed that diffusion doping could be used as a promising method to obtain a therapeutic implant material without compromising its mechanical and structural integrity.

Long-term clinical outcomes and retrieval analysis of a cementless total knee replacement in a dog

OBJECTIVE

The aim of the study was to describe long-term outcomes and report post-retrieval implant analysis following cementless total knee replacement (TKR) in a dog.

ANIMAL

A seven-year-old, male neutered, Labrador retriever.

METHODS

The dog presented for evaluation of chronic left pelvic limb lameness. Orthopedic examination identified bilateral cranial drawer and medial buttress. Radiographs revealed severe bilateral osteoarthritis with moderate joint effusion/synovial hypertrophy. Given the end-stage osteoarthritis, TKR was considered more appropriate than tibial plateau leveling osteotomy (TPLO). The dog underwent a left cementless TKR.

RESULTS

Immediate postoperative radiographs showed appropriate implant positioning. Moderate left pelvic limb lameness with full, pain free and stable stifle range of motion (ROM) was documented at 2 weeks. Increased left hindlimb weight-bearing with a peak vertical force of 70% bodyweight (BW) versus 50% BW on the contralateral leg was reported at 6 weeks. Radiographs showed good implant osseointegration. Left stifle ROM was 50°/170°, a 30° increase compared to preoperative values. Additional rechecks at 14 and 30 weeks showed gradual improvement in stifle ROM and weight-bearing. The dog was euthanized 6 years after surgery for reasons unrelated to TKR. Radiographs demonstrated static implant position without signs of osteolysis and gross examination revealed mild polyethylene wear on the caudal aspects of the tibial insert. Histological evaluation of the implant-bone interface showed extensive and robust osseointegration.

CONCLUSION

This case demonstrates that cementless TKR can be associated with excellent clinical function over the course of at least 6 years and suggests that early surgical intervention could be considered.

Linear and Volumetric Polyethylene Wear Patterns after Primary Cruciate-Retaining Total Knee Arthroplasty Failure: An Analysis Using Optical Scanning and Computer-Aided Design Models

(1) Background: Analyses of retrieved inserts allow for a better understanding of TKA failure mechanisms and the detection of factors that cause increased wear. The purpose of this implant retrieval study was to identify whether insert volumetric wear significantly differs among groups of common causes of total knee arthroplasty failure, whether there is a characteristic wear distribution pattern for a common cause of failure, and whether nominal insert size and component size ratio (femur-to-insert) influence linear and volumetric wear rates. (2) Methods: We digitally reconstructed 59 retrieved single-model cruciate-retaining inserts and computed their articular load-bearing surface wear utilizing an optical scanner and computer-aided design models as references. After comprehensively reviewing all cases, each was categorized into one or more of the following groups: prosthetic joint infection, osteolysis, clinical loosening of the component, joint malalignment or component malposition, instability, and other isolated causes. The associations between volumetric wear and causes of failure were estimated using a multiple linear regression model adjusted for time in situ. Insert linear penetration wear maps from the respective groups of failure were further processed and merged to create a single average binary image, highlighting a potential wear distribution pattern. The differences in wear rates according to nominal insert size (small vs. medium vs. large) and component size ratio (≤1 vs. >1) were tested using the Kruskal-Wallis test and the Mann-Whitney test, respectively. (3) Results: Patients with identified osteolysis alone and those also with clinical loosening of the component had significantly higher volumetric wear when compared to those without both causes (p = 0.016 and p = 0.009, respectively). All other causes were not significantly associated with volumetric wear. The instability group differentiated from the others with a combined peripheral antero-posterior wear distribution. Linear and volumetric wear rates showed no significant differences when compared by nominal insert size (small vs. medium vs. large, p = 0.563 and p = 0.747, respectively) or by component (femoral-to-insert) size ratio (≤1 vs. >1, p = 0.885 and p = 0.055, respectively). (4) Conclusions: The study found increased volumetric wear in cases of osteolysis alone, with greater wear when combined with clinical loosening compared to other groups. The instability group demonstrated a characteristic peripheral anterior and posterior wear pattern. Insert size and component size ratio seem not to influence wear rates.

Early monitoring of inlay wear after total knee arthroplasty on plain radiographs using model-based wear measurement

Wear of the ultra-high molecular-weight polyethylene (UHMWPE) component in total knee arthroplasty contributes to implant failure. It is often detected late, when patients experience pain or instability. Early monitoring could enable timely intervention, preventing implant failure and joint degeneration. This study investigates the accuracy and precision (repeatability) of model-based wear measurement (MBWM), a novel technique that can estimate inlay thickness and wear radiographically. Six inlays were milled from non-crosslinked UHMWPE and imaged via X-ray in anteroposterior view at flexion angles 0°, 30°, and 60° on a phantom knee model. MBWM measurements were compared with reference values from a coordinate measurement machine. Three inlays were subjected to accelerated wear generation and similarly evaluated. MBWM estimated inlay thickness with medial and lateral accuracies of 0.13 ± 0.09 and 0.14 ± 0.09 mm, respectively, and linear wear with an accuracy of 0.07 ± 0.06 mm. Thickness measurements revealed significant lateral differences at 0° and 30° (0.22 ± 0.08 mm vs. 0.06 ± 0.06 mm, respectively; t-test, p = 0.0002). Precision was high, with average medial and lateral differences of - 0.01 ± 0.04 mm between double experiments. MBWM using plain radiographs presents a practical and promising approach for the clinical detection of implant wear.

Vitamin E-stabilized polyethylene shows similar survival rates at minimum 7-year follow-up compared to conventional polyethylene in primary total knee arthroplasty

Purpose

The aim of this cross-sectional study was to compare survival, clinical and radiographic results of total knee arthroplasty (TKA) with vitamin E-stabilized polyethylene (VEPE) or conventional polyethylene (CPE) at a minimum of 7-year follow-up.

Methods

Patients who underwent primary TKA between 2011 and 2015, receiving the same cemented rotating platform knee design with VEPE or CPE tibial inserts, were identified. Patients were contacted for clinical and radiographic follow-up. American Knee Society Score (KSS), Forgotten Joint Score (FJS-12), presence of periprosthetic radiolucent lines (RLLs) and osteolysis were evaluated at the last follow-up. Any revision, reintervention or other complications were recorded.

Results

Among 350 TKAs initially identified, 102 VEPE and 97 CPE knees were included for analysis with mean follow-up of 8.5 and 8.3 years, respectively. No significant difference was found in survival rates at 10-year follow-up with revision due to aseptic loosening (95.0% vs. 97.8%, p = 0.29) or due to any reason (87.6% vs. 89.6%, p = 0.78) between VEPE and CPE TKA. KSS function score resulted significantly higher in the VEPE group over CPE (77 vs. 63, p = 0.01). RLLs were more frequent in VEPE than CPE (54% vs. 32%, p = 0.05), mainly noticed medially and posteriorly beneath the tibial plate, adjacent to the trochlear shield and the posterior condyles. Osteolysis was observed in one knee per group, but patients were asymptomatic with stable implants.

Conclusion

TKA with VEPE and CPE tibial inserts showed comparable survival rates, complications and clinical and radiographic results up to 10-year follow-up.

Level of Evidence

Level III.

The influence of implant design and limb alignment on in vivo wear rates of fixed-bearing and rotating-platform knee implant retrievals

Analysis of polyethylene (PE) wear in knee implants is crucial for understanding the factors leading to revision in total knee arthroplasty. Importantly, current experimental and computational methods for predicting insert wear can only be validated against true in vivo measurements from retrievals. This study quantitatively investigated in vivo PE wear rates in fixed-bearing (FB) (n = 21) and rotating-platform (n = 53) implant retrievals. 3D surface geometry of the retrievals was measured using a structured light scanner. Then, a reference surface that included the deformation, but not the wear that the retrievals had experienced in vivo, was constructed using a fully automatic surface reconstruction algorithm. Finally, wear volume was calculated from the deviation between the worn and reconstructed surfaces. The measurement and analysis techniques were validated and the algorithm was found to produce errors of only 0.2% relative to the component volumes. In addition to quantifying cohort-level wear rates, the effect of mechanical axis limb alignment on mediolateral wear distribution was examined for a subset of the retrievals (n = 14 + 26). Our results show that FB implants produce significantly (p = 0.04) higher topside wear rates (24.6 ± 10.1 mm3/year) than rotating-platform implants (15.3 ± 8.0 mm3/year). This effect was larger than that of limb alignment, which had a smaller and nonsignificant influence on overall wear rates (+4.5 ± 11.6 mm3/year, p = 0.43). However, increased varus alignment was associated significantly with greater medial compartment wear in both the FB and rotating-platform designs (+1.7 ± 1.3%/° and +1.8 ± 1.6%/°). Our findings emphasize the importance of implant design and limb alignment on wear outcomes, providing reference data for improving implant performance and longevity.

A Polished Cobalt-Chrome Baseplate is not Associated With a Lower Revision Rate Than Matt Titanium in a Single Total Knee Arthroplasty Implant System With Identical Baseplate Design

BACKGROUND

Polished baseplates were introduced into total knee arthroplasty (TKA) systems to reduce the incidence of backside wear. In 2004, a fixed-bearing knee arthroplasty system underwent a change in baseplate material from matt titanium to polished cobalt-chrome (CoCr) with the intention to reduce backside wear. Other design aspects were left unchanged. The aim of this study was to compare these implants with each baseplate using data from the Australian Orthopaedic Association National Joint Replacement Registry.

METHODS

Primary TKA procedures performed between January 2010 and December 2021 for osteoarthritis, using a single design with cross-linked polyethylene inserts and matt titanium or polished CoCr baseplates, were analyzed. The primary outcome was all-cause revision, summarized using Kaplan-Meier estimates, with age- and sex-adjusted hazard ratios estimated from Cox proportional hazards models. In total, there were 2,091 procedures with matt titanium and 2,519 procedures with polished CoCr baseplates.

RESULTS

The 9-year cumulative percent revision was 2.5% (95% confidence interval [CI] 1.8 to 3.5%) and 4.2% (95% CI 3.1 to 5.6%) for the matt titanium and CoCr groups, respectively. Compared to matt titanium, the revision rate of CoCr baseplates was not significantly higher (hazard ratio 1.44; 95% CI 0.96 to 2.15; P = .076).

CONCLUSIONS

Polished CoCr baseplates in a single TKA system were not associated with reduced all-cause revision rates compared to matt titanium up to 11 years post-TKA. Our results suggest that the predicted reduction in wear particle debris production from polished CoCr baseplates may not correlate with reduced revision rates in vivo, but further evaluation is required.

Vitamin E-enriched medium cross-linked polyethylene in total knee arthroplasty (VIKEP): clinical outcome, oxidation profile, and wear analysis in comparison to standard polyethylene-study protocol for a randomized controlled trial

BACKGROUND

The gliding surface of total knee endoprostheses is exposed to high loads due to patient weight and activity. These implant components are typically manufactured from ultra-high molecular weight polyethylene (UHMWPE). Crosslinking of UHMWPE by ionizing radiation results in higher wear resistance but induces the formation of free radicals which impair mechanical properties after contact with oxygen. Medium-crosslinked UHMWPE enriched with vitamin E (MXE) provides a balance between the parameters for a sustainable gliding surface, i.e., mechanical strength, wear resistance, particle size, and oxidation stability. Therefore, a gliding surface for knee endoprostheses made up from this material was developed, certified, and launched. The aim of this study is to compare this new gliding surface to the established predecessor in a non-inferiority design.

METHODS

This multicenter, binational randomized controlled trial will enroll patients with knee osteoarthritis eligible for knee arthroplasty with the index device. Patients will be treated with a knee endoprosthesis with either MXE or a standard gliding surface. Patients will be blinded regarding their treatment. After implantation of the devices, patients will be followed up for 10 years. Besides clinical and patient-related outcomes, radiological data will be collected. In case of revision, the gliding surface will be analyzed biomechanically and regarding the oxidative profile.

DISCUSSION

The comparison between MXE and the standard gliding surface in this study will provide clinical data to confirm preceding biomechanical results in vivo. It is assumed that material-related differences will be identified, i.e., that the new material will be less sensitive to wear and creep. This may become obvious in biomechanical analyses of retrieved implants from revised patients and in radiologic analyses.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04618016. Registered 27 October 2020, https://clinicaltrials.gov/study/NCT04618016?term=vikep&checkSpell=false&rank=1 . All items from the World Health Organization Trial Registration Data Set can be found in Additional file 1.

Five-year migration and insert wear of uncemented tibial components with either conventional polyethylene or sequentially annealed highly crosslinked polyethylene inserts: a blinded randomized controlled trial using radiostereometric analysis

The primary objective of this study was to compare the five-year tibial component migration and wear between highly crosslinked polyethylene (HXLPE) inserts and conventional polyethylene (PE) inserts of the uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary objectives included clinical outcomes and patient-reported outcome measures (PROMs). A double-blinded, randomized study was conducted including 96 TKAs. Tibial component migration and insert wear were measured with radiostereometric analysis (RSA) at three, six, 12, 24, and 60 months postoperatively. PROMS were collected preoperatively and at all follow-up timepoints. There was no clinically relevant difference in terms of tibial component migration, insert wear, and PROMs between the HXLPE and PE groups. The mean difference in tibial component migration (maximal total point migration (MTPM)) was 0.02 mm (95% confidence interval (CI) -0.07 to 0.11), which is below the value of 0.2 mm considered to be clinically relevant. Wear after five years for HXLPE was 0.16 mm (95% CI 0.05 to 0.27), and for PE was 0.23 mm (95% CI 0.12 to 0.35). The mean difference in wear rate was 0.01 mm/year (95% CI -0.02 to 0.05) in favour of the HXLPE group. Wear is mainly present on the medial side of the insert. There is no clinically relevant difference in tibial component migration and insert wear for up to five years between the HXLPE conventional PE inserts. For the implant studied, the potential advantages of a HXLPE insert remain to be proven under clinical conditions at longer-term follow-up.

Outcomes After Revision Total Knee Arthroplasty from a Specific, Now-recalled Implant System

BACKGROUND

A specific total knee arthroplasty (TKA) implant system was recently recalled for high incidence of early polymeric wear and osteolysis. We analyzed the early outcomes of aseptic revision with these implants.

METHODS

We identified 202 aseptic revision TKAs of this implant system performed at a single institution between 2010 and 2020. Revision indications included aseptic loosening (n=120), instability (n=55), and polymeric wear/osteolysis (n=27). In 145 cases (72%) components were revised and 57 cases (28%) were isolated polyethylene insert exchange. Kaplan-Meier and Cox proportional hazards analyses were used to determine survivorship free from all-cause re-revision and re-revision risk factors.

RESULTS

At 2 and 5 years, survivorship free from all-cause re-revision was 89 and 76% in the polyethylene exchange cohort versus 92 and 84% in the component revision cohort (P=0.5). At 2 and 5 years, survivorship in revision with components from the same manufacturer was 89 and 80% compared to 95 and 86% in revision with components from a different manufacturer (P=0.2). Among re-revisions (n=30), cones (37%), sleeves (7%), hinge/distal femoral replacement implants were frequently used (13%). Men had increased risk for re-revision (Hazard Ratio=2.3, P=0.04).

CONCLUSIONS

In this series of aseptic revision TKAs performed on a now-recalled implant system, survivorship free from re-revision was lower than expected when components from the same manufacturer were utilized, but comparable to contemporary reports when both components were revised with an alternative implant system. Metaphyseal fixation with cones and sleeves as well as highly constrained implants were frequently utilized at time of re-revision TKA.

Mid-term survivorship of primary total knee arthroplasty with a specific implant

The purpose of this study was to assess mid-term survivorship following primary total knee arthroplasty (TKA) with Optetrak Logic components and identify the most common revision indications at a single institution. We identified a retrospective cohort of 7,941 Optetrak primary TKAs performed from January 2010 to December 2018. We reviewed the intraoperative findings of 369 TKAs that required revision TKA from January 2010 to December 2021 and the details of the revision implants used. Kaplan-Meier analysis was used to determine survivorship. Cox regression analysis was used to examine the impact of patient variables and year of implantation on survival time. The estimated survivorship free of all-cause revision was 98% (95% confidence interval (CI) 97% to 98%), 95% (95% CI 95% to 96%), and 86% (95% CI 83% to 88%) at two, five, and ten years, respectively. In 209/369 revisions there was a consistent constellation of findings with varying severity that included polyethylene wear and associated synovitis, osteolysis, and component loosening. This failure mode, which we refer to as aseptic mechanical failure, was the most common revision indication. The mean time from primary TKA to revision for aseptic mechanical failure was five years (5 months to 11 years). In this series of nearly 8,000 primary TKAs performed with a specific implant, we identified a lower-than-expected mid-term survivorship and a high number of revisions with a unique presentation. This study, along with the recent recall of the implant, confirms the need for frequent monitoring of patients with Optetrak TKAs given the incidence of polyethylene failure, osteolysis, and component loosening.

What Patient and Implant Factors Affect Trunnionosis Severity? An Implant Retrieval Analysis of 664 Femoral Stems

BACKGROUND

Corrosion at the modular head-neck taper interface of total and hemiarthroplasty hip implants (trunnionosis) is a cause of implant failure and thus a clinical concern. Patient and device factors contributing to the occurrence of trunnionosis have been investigated in prior implant retrieval studies but generally with limited sample sizes and a narrow range of models. The purpose of the present investigation was to determine which patient and device factors were associated with corrosion damage on the femoral stem taper across a large collection of different implant models retrieved following revision hip arthroplasty.

METHODS

A retrieval study of 664 hip arthroplasty modular stem components was performed. Patient and device information was collected. Trunnions were imaged under digital microscopy and scored for corrosion damage using a scaling system. Damage was related to patient and device factors using regression analyses.

RESULTS

Greater duration of implantation (P = .005) and larger head size (P < .001) were associated with an elevated corrosion class. Older age at index surgery (P = .035), stainless steel stem material (P = .022), indication for revision as bone or periprosthetic fracture (P = .017), and infection (P = .018) and certain larger taper geometries were associated with a decreased corrosion class.

CONCLUSION

Factors identified as contributing to a higher or lower risk of more severe corrosion are consistent with most prior smaller retrieval studies. Surgeons should be aware of these risk factors when selecting implants for their patients and when diagnosing trunnionosis in symptomatic hip arthroplasty patients.

The impact of posterior-stabilized vs. constrained polyethylene liners in revision total knee arthroplasty

AIM

Posterior stabilized (PS) and varus valgus constrained (VVC) knee polyethylene liners have been shown to confer excellent long-term functional results following revision total knee arthroplasty (rTKA). The purpose of this study was to compare outcomes of patients who underwent rTKA using either a PS or VVC liner.

METHODS

A retrospective comparative study of 314 rTKA with either PS or VVC liner and a minimum follow-up time of two years was conducted. Patient demographics, complications, readmissions, and re-revision etiology and rates were compared between groups. Kaplan-Meier survivorship analysis was performed to estimate freedom from all-cause revision.

RESULTS

Hospital LOS (3.41 ± 2.49 vs. 3.34 ± 1.93 days, p = 0.793) and discharge disposition (p = 0.418) did not significantly differ between groups. At a mean follow-up of 3.55 ± 1.60 years, the proportion of patients undergoing re-revision did not significantly differ (19.1% vs. 18.7%, p = 0.929). In subgroup analysis of re-revision causes, the VVC cohort had superior survival from re-revision due to instability compared to the PS cohort (97.8% vs. 89.4%, p = 0.003). Freedom from re-revision due to aseptic loosening did not significantly differ between groups (85.2% vs. 78.8%, p = 0.436). Improvements in range of motion (ROM) from preoperative to latest follow-up were similar as well.

CONCLUSIONS

PS and VVC liners confer similar survivorship, complication rates, and overall knee ROM in rTKA. VVC liners were not associated with increased postoperative aseptic loosening and demonstrated superior freedom from re-revision due to instability. Future studies with longer follow-up are warranted to better determine significant differences in clinical outcomes between the two bearing options.

LEVEL III EVIDENCE

Retrospective Cohort Study.

A review of advances in tribology in 2020–2021

Around 1,000 peer-reviewed papers were selected from 3,450 articles published during 2020–2021, and reviewed as the representative advances in tribology research worldwide. The survey highlights the development in lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology, providing a show window of the achievements of recent fundamental and application researches in the field of tribology.