Distinct immunohistomorphologic changes in periprosthetic hip tissues from historical and highly crosslinked UHMWPE implant retrievals

Abstract

Assessment of immune response to implant wear debris in periprosthetic tissue following total hip arthroplasty suggests that multiple factors are involved in the loss implant function. The current study investigated wear debris and the associated immunohistomorphologic changes in tissues from nine patients with historical (gamma air-sterilized) and nine highly-crosslinked UHMWPE implant components. Paraffin embedded tissue sections were evaluated for the presence of histiocytes, giant cells, fibrocartilage/bone and necrosis. To determine the incidence, degree and co-localization of immunohistomorphologic changes and wear, overlapping full-field tissue arrays were collected in brightfield and polarized light. The historical cohort tissues predominantly showed histiocytes associated with significant accumulations of small wear (0.5–2 μm), and giant cells associated with large wear (≥2 μm). Frequently, focal regions of necrosis were observed in association with wear debris. For the highly-crosslinked cohort, inflammation and associated wear debris were limited, but in tissues from patients revised after implantation times of >2 years a response was observed. Whereas significant amounts of fibrocartilage/bone were observed in patients at earlier implantation times. In both cohorts, tissue responses were more extensive in the retroacetabular or proximal femoral regions. The current findings suggest that wear debris-induced inflammation may be a major contributor to the loss of implant function for both the historical and highly-crosslinked cohorts, but it is not the primary cause of early implant loosening. This study highlights the importance of using a more quantitative and standardized assessment of immunohistomorphologic responses in periprosthetic tissues, and emphasizes differences in specific anatomical regions of individual patient tissues.

Do Tissues From THA Revision of Highly Crosslinked UHMWPE Liners Contain Wear Debris and Associated Inflammation?

“…We recently reported the presence of histomorphologic changes in HXLPE revision tissues [8]. Specifically, our results showed a prevalence of fibrocartilage in tissues from HXLPE revisions implanted for less than 3 years (four of nine patients), implicating poor osseointegration in the development of loosening [71].…”

“…We collected tissue samples from 18 consenting patients undergoing revision THA of uncemented, metal-on-UHMWPE hip components using a standardized tissue retrieval protocol; these are the same tissues used in the previous study [8]. UHMWPE liners were classified into two cohorts: conventional gamma air-sterilized UHMWPE (n = 9) and gamma inert-sterilized HXLPE (n = 9).…”

“…Initial validation of EPLIS was performed using scanning electron microscopy in a prior study of histomorphologic changes and wear debris in periprosthetic hip tissues [8].…”

“…Strictly where indicated, differences in the median number of immune cells/mm 2 were compared by the Wilcoxon Mann-Whitney test for each UHMWPE cohort (conventional versus HXLPE) and tissue region (pseudocapsular versus periprosthetic). Based on a prior evaluation of the same patient tissues, the sample sizes in the current study were sufficiently powered ([ 0.9) to identify similar differences in inflammatory cell responses [8]. Statistical analysis was performed using JMP 8.0 (SAS Institute Inc, Cary, NC, USA).…”

“…The interaction of particles and cells in periprosthetic tissue and surrounding bone contributes to the deregulation of bone homeostasis resulting in osteolysis at the bone-implant interface [27,61,63]. Consequently, highly crosslinked UHMWPE (HXLPE) was introduced to improve wear properties of the bearing surface [8,32,44,54,57], and in vitro studies have shown 40% to 95% reductions in wear rate as compared with conventional UHMWPE [37,53,58]. However, the brittle nature of the HXLPE [11], generation of predominantly submicron-sized particles [55,61,64], and studies showing the effect of particle size, shape, and number raise concerns regarding the long-term clinical performance of HXLPE [30,43,69,73].…”