Collapse-Related Bone Changes in Osteonecrotic Femoral Heads at Multidetector CT: Comparison between Femoral Heads with Limited and Advanced Collapse.

Aim: To assess the frequency of bone changes in resected osteonecrotic femoral head (ONFH) specimens at multidetector computed tomography (MDCT) and compare their frequencies between ONFH with limited or advanced collapse.

Method: Fourteen ONFH were imaged using MDCT (n = 14) and microcomputed tomography ([µCT]; n = 8). Preoperative staging was performed using radiographs and MRI. Coronal reformats of MDCT images of the specimens were analyzed using the grid overlay method. There were 2,933 grid boxes containing cortical bone and 10,596 containing trabecular bone. Two MSK radiologists assessed in every grid box the presence of interface-related sclerosis, cortical bone interruption, trabecular bone interruption, and trabecular bone resorption. The frequency of grid boxes with bone changes at MDCT was calculated and compared between ONFH with limited (<1.5 mm) or advanced (≥1.5 mm) collapse.

Results: For both readers R1 and R2, there were 1111/10596 (10.5%) and 1362/10596 (12.9%) grid boxes with interface-related bone sclerosis, 557/2933 (19%) and 413/2933 (14.1%) with cortical bone interruption, 796/10596 (7.5%) and 665/10596 (6.3%) with trabecular bone interruption, and 331/10596 (3.1%) and 595/10596 (5.6%) with trabecular bone resorption. The frequency of grid boxes with cortical interruption and trabecular bone resorption was significantly higher in ONFH with advanced than in ONFH with limited collapse. There was no significant difference in frequency of grid boxes with trabecular interruption and interface-related bone sclerosis between ONFH with advanced or limited collapse.

Conclusion: Cortical interruption and trabecular resorption, but not trabecular interruption, were more frequent in osteonecrotic femoral heads with advanced than with limited collapse.