Further studies of degenerative hip disease; antitrochanteric degeneration in turkeys and broiler type chickens.

Postmortem examination revealed antitrochanteric degeneration in turkeys (8 male, 2 female) and broiler type chickens (5 male, 1 female). Antitrochanteric degeneration was detected in birds aged 20 weeks or older but histological examination identified lesions in others with grossly normal antitrochanters. Normal and abnormal antitrochanteric development was studied in male, skeletally immature, turkeys and broilers. Differential subchondral bone growth occurred, with relatively delayed ilial bone development. As a result, hyaline cartilage was retained dorsally and persisted even in adult birds. Retained hyaline, and in younger birds growth plate, cartilage was prone to osteochondrosis. When cartilage flap formation involved fissures traversing retained hyaline cartilage, the term osteochondrosis dissecans was appropriate. In other cases of antitrochanteric degeneration, changes typical of osteoarthrosis were present with, in some instances, no evidence of pre-existing osteochondrosis. Certain sites of antitrochanteric cartilage may be susceptible to fatigue failure in these cases.