Histomorphometric analysis of the proximal portion of the femur in dogs with osteoarthritis

OBJECTIVE: To describe cancellous architecture of the proximal portion of the femur in dogs with osteoarthritis. ANIMALS: 30 dogs with coxofemoral osteoarthritis. PROCEDURE: All dogs had femoral head and neck excision or total hip arthroplasty. Histomorphometry software was used to analyze computer images of 100-microm-thick coronal and transverse plane sections of the head and neck of the femur. Histologic preparations of coronal and transverse sections of articular cartilage were graded. RESULTS: Bone volume/total volume, trabecular thickness, trabecular number, and bone surface/total volume were significantly higher in the femoral head than femoral neck. Trabecular alignment (anisotropy) and separation were significantly higher in the femoral neck than femoral head. Anisotropy was significantly increased in the medial portion of the femoral head in the coronal plane and in the cranial portion of the femoral neck in the transverse plane, compared with healthy dogs. The medial half of femoral head cartilage that overlies the proximomedial cancellous bone region had significantly more degraded cartilage than the lateral half. Histologic grades for cranial and caudal halves of femoral head articular cartilage were similar. CONCLUSIONS AND CLINICAL RELEVANCE: Most findings were similar to those in healthy dogs. Greater trabecular alignment in the proximomedial region of the femoral head and craniolateral region of the femoral neck in dogs with osteoarthritis suggests an altered transfer of load through the coxofemoral joint. Greater cartilage degradation on the medial half of the femoral head supports an association between increased trabecular alignment and cartilage degradation.