Developing coxal joint of the dog: gross morphometric and pathologic observations

The growth and development of the proximal parts of femurs and the acetabula were studied in 32 English Pointers. The dogs were allotted to 8 age groups, birth through 9 months of age. Dogs were euthanatized, and at necropsy, 6 linear measurements were made on the proximal part of each femur: the cranial-caudal and the dorsal-ventral diameters of the femoral head, and the widths of the articular surface of the head from the center of the fovea to the cranial, caudal, dorsal, and ventral articular margins. Also 7 linear measurements were made on each acetabulum, including the cranial-caudal and the dorsal-ventral diameters, the length and width of the acetabular fossa, and the width of the lunate surface from the acetabular lip to the acetabular fossa in 3 places. All of the linear values increased rapidly during the first 4 weeks of life and slowly thereafter, and most of them increased simultaneously and proportionately. By 9 months of age, average body weight had increased by a factor of 52 (from initial 0.4 kg to 20.9 kg) and the diameter of the femoral heads and acetabula had increased by a factor of 4.5. Other coxal joint features were also evaluated, including the relative thickness of the joint capsule, the presence of fraying or disruption of the ligament of the femoral head, and the smoothness and regularity of the articular surfaces. Coxal joints in the younger dogs were free of grossly detectable pathologic changes. However, abnormalities of various joint components were present in 1 of the 6 dogs in the 5-month age group, in 2 of the 6 dogs in the 7-month age group, and in 4 of the 6 dogs in the 9-month age group.