Changes in the acetabular fossa of the hip: MR arthrographic findings correlated with anatomic and histologic analysis using cadaveric specimens.

ABSTRACT

OBJECTIVE: The objective of our study was to determine the morphologic and histologic pattern of tissue changes in the acetabular fossa and evaluate its association with osteoarthritis of the hip joint. MATERIALS AND METHODS: Eleven cadaveric hip joints derived from elderly persons were examined using MR arthrography. All 11 joints were then sectioned. The pattern of acetabular fossa changes determined during inspection of the anatomic and histologic sections in all cadaveric specimens was correlated with MR arthrographic findings. We classified acetabular fossa changes into three stages. Imaging findings of osteoarthritis were reviewed to assess for an association between acetabular cartilage changes and acetabular fossa changes. RESULTS: MR arthrographic findings of changes in the acetabular fossae included low signal intensity related to multiple thin or thick fibrous strands in the acetabular fat and a decrease in the amount of peripheral fatty tissue. Histologic findings revealed fat necrosis, fibrous strands, a decrease in the amount of fat, fibrocartilaginous metaplasia of fat, and chondroid metaplasia at the bony surface of the acetabular fossa. There was a statistically significant correlation between the advanced stage (stage IV) of acetabular cartilage degeneration and the advanced stage (stage 3) of acetabular fossa change (p < 0.001). CONCLUSION: In a small number of specimens, MR arthrographic findings and histologic analyses showed fibrofatty tissue changes and chondroid metaplasia in the acetabular fossae of cadavers derived from an elderly population. The advanced stage of acetabular fossa change was correlated statistically with the advanced stage of acetabular cartilage degeneration.