How Does Wear Rate Compare in Well-functioning Total Hip and Knee Replacements? A Postmortem Polyethylene Liner Study

Abstract

Background The longevity of total hip (THR) and knee replacements (TKR) that used historical bearing materials of gamma-in-air sterilized UHMWPE was affected more by osteolysis in THRs than in TKRs, although osteolysis remains a concern in TKRs. Therefore, the study of polyethylene wear is still of interest for the knee, particularly because few studies have investigated volumetric material loss in tibial knee inserts. For this study, a unique collection of autopsy-retrieved TKR and THR components that were well-functioning at the time of retrieval was used to compare volumetric wear differences between hip and knee polyethylene components made from identical material. Questions/purposes The following questions were addressed: (1) How much did the hip liners wear and what wear patterns did they exhibit? (2) How much did the knee inserts wear and what wear patterns did they exhibit? (3) What is the ratio between TKR and THR wear after controlling for implantation time and patient age? Methods We compared 23 THR components (HarrisGalante [HG] and HG II) and 20 TKR components (MillerGalante [MG II]) that were retrieved postmortem. The components were made from the same polyethylene formulation and with similar manufacturing and sterilization (gamma-in-air) processes. Twenty-one patients (12 males, nine females) had THRs and 16 (four males, 12 females) had TKRs. Patients who had TKRs had an older (p = 0.001) average age than patients who had THRs (age, 75 years; SD, 10, versus 66 years; SD, 12, respectively). Only wellfunctioning components were included in this study. Therefore, implants retrieved postmortem from physically active patients and implanted for at least 2 years were considered. In addition, only normally wearing TKR components were considered, ie, those with fatigue wear (delamination) were excluded. The wear volume of each component was measured using metrology. For the tibial inserts an autonomous mathematic reconstruction method was used for quantification. Results The acetabular liners of the THR group had a wear rate of 38 mm 3 per year (95% CI, 29-47 mm 3 /year). Excluding patients with low-activity, the wear rate was 47 mm 3 per year (95% CI, 37-56 mm 3 /year). The wear rate of normally wearing tibial inserts was 17 mm 3 per year (95% CI, À6 to 40 mm 3 /year). After controlling for the relevant confounding variable of age, we found a TKR/THR wear rate ratio of 0.5 (95% CI, 0.29-0.77) at 70 years of age with a slightly increasing difference with increasing age. Conclusions Excluding delamination, TKRs exhibited lower articular wear rates than THRs for historical polyethylene in these two unique cohorts of postmortem retrievals.

High frequency circular translation pin-on-disc wear testing of UHMWPE using a ball-on-flat contact along a hypotrochoidal track

“…In the earlier HF-CTPOD study with a flat-onflat contact (prosthetic hip wear simulation), the mean wear rate was 0.82 mg/10 6 cycles [3], i.e., 2.3 times higher than the present ball-on-flat wear rate, 0.35 mg/10 6 cycles. Interestingly, this ratio was in agreement with a retrieval study in which it was found out that the mean wear rate of conventional UHMWPE acetabular hip liners (44 mm 3 /year) was twice that of conventional UHMWPE tibial knee inserts (22 mm 3 /year) in well-functioning prostheses that were free from oxidative damage, retrieved postmortem [17]. Clinical wear factors for tibial inserts are not available, so a comparison with the wear factor value obtained in the present study, 3.5 × 10 -6 mm 3 /Nm, is unfortunately not possible.…”

“…The polished appearance of the wear mark together with fine scratches observed in microscopy (Fig. 4) were in agreement with a retrieval study regarding well-functioning knee prostheses, free 8 from oxidative damage [17].…”

Joint line elevation and tibial slope are associated with increased polyethylene wear in cruciate‐retaining total knee replacement

“…The average wear rate of 11.6 mm 3 /y for the Nexgen tibial inserts in this study seems reasonable compared to other studies of this and similar designs. This study had a lower articular wear rate than what we previously reported for an earlier design, the Miller Galante (MG) II prosthesis (Zimmer Inc, Warsaw) 4 . The MG II system was the predecessor of the NexGen system and the higher wear rate of 18 mm 3 /y is likely attributable to a lower polyethylene quality 4 .…”

“…It is well recognized that wear is a multifactorial problem involving the manufacturer, the patient and the surgeon 2,3 . Progress has been made to understand material and design factors, as well as important patient factors such as age and activity 2,4 . Although, there have been computational biomechanics models that demonstrated the influence of surgical alignment on tibiofemoral kinematics, kinetics, and wear, 5,6 with the exception of grossly malpositioned components, there is little knowledge about the impact of implant positioning on wear.…”

The Rationale for Using Bacteriophage to Treat and Prevent Periprosthetic Joint Infections

“…The cost associated with each of these revisions is more than $25,000 and is associated with a significant morbidity as well as a one year mortality greater than 10% ( Zmistowski et al, 2013 ; Kamath et al, 2015 ). Despite being the focus of research efforts for many years, treatment failure of PJI can be high with failure rates up between 20 and 50% when the implant is retained ( Peel et al, 2011 ; Namba et al, 2013 ; Pourzal et al, 2016 ; Song et al, 2018 ).…”