Background: Subcondral bone changes seem to contribute to the progression of osteoarthritis (OA). In early-stage OA there is a high rate of bone remodelling in the subchondral bone, whereas in late-stage disease this process slows down and subsequently bone formation increases. This results in subchondral bone thickening that is evident in X-rays of advanced stage disease. Whether these changes are the initiation or the result of cartilage degradation is not clear yet. Bone and cartilage are seen as a functional unit in which damage in one tissue will affect the other and vice versa, respectively. Microstructural analysis of late-stage OA of the hip demonstrated an increased density of subchondral in areas beneath cartilage damage. 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. Materials & 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 the medial compartment than valgus, whereas valgus alignment had a significantly higher subchondral bone fraction volume in the lateral compartment (p=0,011). Conclusion: 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 and the proper management of these changes might prevent or stop the progression of OA. Furthermore, during preparation of this study an intensive literature search and subsequent analysis (citation analyses) in the field of bone, joint and arthroplasty was performed that resulted in two publications of most cited research papers in arthroplasty as well as osteoporosis and associated diseases.
Microstructural Analysis of Subchondral Bone in Knee Osteoarthritis
Holzer, L. (Author). 2015
Student thesis: Doctoral thesis