gms | German Medical Science

Objectives: T1rho/T2 mapping MRI is a novel modality to assess cartilage degeneration with high efficient tissue differentiation, while intraoperative micro-CT is a promising modality to determine trabecular structure in three dimensions. We combined the accuracy of these two technologies to measure bone quality using specimen micro-CT with cartilage measurements using MRI pre-operative imaging in osteonecrosis of femoral head (ONFH).

Methods: 23 ONFH specimens in 23 patients in Association of Research Circulation Osseous (ARCO) III and 12 end-stage osteoarthritis participants with total hip arthroplasty had been involved. Median patient age was 45 years (range 33-53 years). A tabletop micro-CT was used to image necrotic femoral head specimens. The particular values on three-dimensional reconstructed micro-CT images of the specimen was compared with the measurements determined by pre-operative T1rho/T2 mapping MRI.

Results and Conclusion: The values of T1rho and T2 mapping in femoral head of OA patients (T1rho: 61.28±4.58ms, T2 mapping: 38.54±8.81ms, T: -3.76, P<0.001) were significantly higher than those in the ONFH group (T1rho: 50.98±13.23ms, T2 mapping: 25.47±9.04ms, T: -4.51, P<0.001). The ONFH group, compared with the OA group in the micro-CT, suggested that the value of Bone Volume/Tissue Volume (BV/TV), Connectivity Density (Conn.D.), Structure Model Index (SMI), Trabecular Number (Tb.N) and Trabecular Thickness(Tb.Th) were decreased in the ONFH group, while Bone Surface/Tissue Volume(BS/BV), Trabecular Separation/Spacing(Tb.Sp) increased (P<0.05). Among them, T1rho, T2 mapping value had the best correlation coefficient with Tb.Sp (r=0.82, p<0.001; r=0.89, p<0.001). When compared with T1rho, T2 mapping value, BV/TV had the negative coefficient (r=-0.83, p<0.01; r=-0.79, p<0.01). Overall, cartilage degeneration tend to correlate with bone volume decrease and trabecular disorder, suggesting the close relationship between cartilage and necrosis in the collpase of femoral head. T1rho/T2 mapping MRI and 3D intraoperative micro-CT are both the promising new technique which could potentially be used for accurate assessment of cartilage degeneration and trabecular structure in ONFH in order to guide dignosis and treatment. Future studies need to be carried out to see if this technology could have a role of necrotic tissue assessment.