Microstructural analysis of subchondral bone in knee osteoarthritis

Abstract

Purpose: Subcondral bone changes seem to contribute to the progression of knee osteoarthritis (OA). This study aimed to analyse subchondral bone microstructure in specimens of late-stage knee OA in respect to articular cartilage damage, meniscus integrity and knee joint alignment. Methods: 30 proximal tibiae of 30 patients (20 female and 10 male) with late-stage OA that were retrieved during total knee arthroplasty (TKA) were scanned using a high-resolution Micro-Computed Tomography (μCT). The scans were semi-automatically segmented into five regions of interest (ROIs). The ROIs were than further analysed using a commercially available software. The degree of articular cartilage damage was assessed semiquantitatively by magnetic resonance imaging (MRI) before surgery. Results: The mean bone fraction volume in the medial compartment was significantly higher compared to the mean bone fraction volume in the lateral compartment (62,07 ± 12,53 vs. 52,57 ± 13,33). The differences were statistically significant (p=0,007). The submeniscal mean bone fraction volume in the medial compartment was statistically significantly higher compared to submeniscal mean bone fraction volume in the lateral compartment (56,76 ± 12,8 vs. 47,36 ± 14,97; p=0,015). There was a significantly lower bone fraction volume in the medial submeniscal subchondral bone compared to the subchondral bone fraction volume from the medial tibial plateau compartment (p=0,041). There was a significant difference in the lateral submeniscal subchondral bone fraction volume compared to the subchondral bone fraction volume from the lateral tibial plateau compartment (p=0,024). The bone fraction volume in all weight bearing locations (medial meniscus, medial tibial plateau, lateral meniscus, lateral tibial plateau) was significantly higher compared to the non weight-bearing reference point below the ACL (p=0,000). In intact menisci, there was a significantly lower subchondral bone fraction volume compared to subluxated or luxated meniscus in the medial (p=0,020) and lateral compartment (p=0,005). Varus alignment had a significantly higher subchondral bone fraction volume in the medial compartment than valgus, whereas valgus alignment had a significantly higher subchondral bone fraction volume in the lateral compartment (p=0,011). Conclusions: The results of this study show significant differences of subchondral bone microstructural parameters in respect to cartilage damage, meniscus’ structural integrity and knee joint alignment. Therefore, subchondral microstructural bone changes seem to be a secondary process in the late-stage OA of knee caused by mechanical changes.