Guidelines for Chiari's osteotomy in the immature skeleton developed from a canine model.

Three variations of Chiari's pelvic osteotomy were performed on 18 dysplastic hip joints in young, growing German shepherd dogs and rottweilers. The results of the operations and the reactions of the skeletal tissue were investigated radiologically and histologically after six and 12 months. By use of polyfluorochrome sequential labeling and microangiography, it was demonstrated that neither the formation of new bone nor the blood supply in the vicinity of the rim of the acetabulum (apophysis of the acetabular roof) was seriously impaired by the operation. Conversely, the operative technique was of decisive importance to the result of the operation. Only if the osteotomy was performed through the original acetabular rim, completely covering the femoral head, was the newly formed acetabular roof adequately biomechanically loaded, providing the conditions required for functionally adapted differentiation of skeletal tissue. Chiari's pelvic osteotomy can be performed on canine hips with good chances of success, provided one uses the proper operative technique. Apophyseal bone growth and the blood supply of the newly formed acetabular roof were apparently not disturbed by Chiari's operation.