Necrobiosis and T-lymphocyte infiltration in retrieved aseptically loosened metal-on-polyethylene arthroplasties

Abstract

Background and purpose: Soft tissue necrobiosis and T-lymphocyte infiltration within the periprosthetic soft tissue have been linked to a suggested hypersensitivity reaction of the delayed-type following the metal-on-metal arthroplasty. While we observed both synovial necrobiosis and lymphocyte infiltrates in synovial tissues with failed metal-on-polyethylene prostheses, we hypothesized that both findings are unspecific for metal-on-metal bearing coupes. Thus, we wished to quantify the extent of necrobiosis and the amount of T-lymphocyte infiltration in aseptically loosened metal-on-polyethylene prostheses.

Materials and methods: We analyzed 28 consecutive synovial biopsy specimens obtained at revision surgery of aseptically loosened metal-on-polyethylene prostheses (19 hips and 9 knees) and quantified both the extent of necrobiosis vertically and the density of CD3+, CD4+, and CD8+ lymphocytes within the joint capsular tissue. We excluded patients with inflammatory skeletal disease or with a history of metal hypersensitivity.

Results: We found necrobiosis in 23 of 28 cases and it was most often connected with the superficial portions of the synovium. Necrobiosis of deeper tissues was seen in 8 specimens and it was strongly associated with superficial necrobiosis. While CD3+ lymphocytes were detected in each biopsy, 4 cases with more than 300 CD3+ lymphocytes were identified in the group of 26 cases that presented with more than 100 CD3+ lymphocytes within one high-power field. 16 cases with more than 100 CD3+ lymphocytes also showed concomitant superficial necrobiosis of the synovium. In the inflammatory infiltration of periprosthetic synovium, CD8+ lymphocytes predominated over CD4+ cells.

Interpretation: Synovial necrobiosis and infiltration of T-lymphocytes are common findings in tissues around aseptically loosened metal-on-polyethylene arthroplasty in patients without a clinically suspected metal hypersensitivity reaction. Thus, neither necrobiosis nor infiltration of T-lymphocytes should be considered to be specific for failed metal-on-metal bearings or metal hypersensitivity reaction.

Figure 1.

Synovial tissue necrobiosis. (A) Villous proliferations without stainable synoviocytes, blood vessel walls, stromal cells, and inflammatory infiltrates (at top right) were characteristic of villous necrobiosis. (B) Band-like acellular areas of the synovial surface (upper half) showing scattered ghost cells were a typical finding in synovial surface necrobiosis. Their maximal extent vertically was measured digitally and recorded in each case. (C) Similar acellular areas (at lower right) in deeper periarticular soft tissue without any contact with the synovial surface in this specimen were referred to as deep necrobiosis. (Hematoxylin and eosin).

Figure 2.

Immunohistochemistry with antibody to CD3 antigen was performed in order to identify T-lymphocytes within the synovial soft tissue. In this particular case, both perivascular (mid right) and diffuse CD3+ lymphocytes were detected. Polyethylene wear particles were apparent under polarized light microscopy in several foreign body giant cells and histiocytes. (Embedding in paraffin wax; microscopic analysis under polarized light; immunohistochemical reaction with CD3 antibody).