Oral Presentation 33rd ASM of the Australian & New Zealand Bone & Mineral Society 2023

Histological changes to the osteocyte peri-lacunocanalicular bone matrix that distinguish aseptic loosening from periprosthetic joint infection (#56)

Dzenita Muratovic 1 , Dongqing Yang 1 , Anja Zelmer 1 , Lucian B Solomon 1 2 , Gerald J Atkins 1
  1. Centre for Orthopaedic & Trauma Research, The University of Adelaide, Adelaide, South Australia, Australia
  2. Orthopaedic and Trauma Service, The Royal Adelaide Hospital and the Central Adelaide Local Health Network, ADELAIDE, SA, Australia

Introduction

Previous analysis of bone from patients with periprosthetic joint infection (PJI) revealed widespread lack of intact or mature collagen, commonly surrounding osteocytes [1]. This was attributed to increased expression of matrix degrading enzymes by osteocytes and was independent of infective organism. It has been proposed that aseptic loosening may represent cases of subclinical infection. We sought to examine possible means of distinguishing between these pathologies at the bone histological level.

Methods

We examined histology of bone taken from patients with aseptic loosening due to osteolysis with no clinical signs of infection (n = 15) and compared these with bone from confirmed PJI cases (n = 50) and control bone taken from patients undergoing primary hip arthroplasty (n = 10). Samples were formalin fixed, demineralised, paraffin embedded and sectioned, and then subjected to Masson’s trichrome and Ploton silver stains.

Results

PJI specimens all showed characteristic type I collagen degradation. A modified trichrome stain highlighted perilacunar ‘collars’ of degraded collagen in PJI. Aseptic loosening cases also showed areas of degraded collagen although less severe. Aseptic loosening bone also had a distinctive ‘mottled’ appearance, with circular clearings in the matrix often aligned along canaliculi. Overall, aseptic loosening bone showed many more prominent canaliculi than control bone, while PJI bone had a relative deficit of canaliculi. Silver stain confirmed an increased canalicular size in aseptic loosening bone, with circular lesions corresponding to apparent nodules along these.

Conclusions

Aseptic loosening bone in all cases displayed characteristic prominent canaliculi with associated nodules due likely to increased pericanalicular osteolysis/remodelling. This was distinct from PJI bone where more widespread matrix degradation was evident with a relative lack of canalicular structures emanating from osteocyte lacunae. Histological examination of bone collagen composition and osteocyte lacunocanalicular morphology may therefore provide a useful means of distinguishing cases of aseptic loosening from PJI.

  1. Ormsby RT, Zelmer AR, Yang D, Gunn NJ, Starczak Y, Kidd SP, et al. Evidence for osteocyte-mediated bone-matrix degradation associated with periprosthetic joint infection (PJI). Eur Cell Mater 2021; 42: 264-280.