The Journal of Bone and Joint Surgery, Vol 66, Issue 8 1281-1288, Copyright © 1984 by Journal of Bone and Joint Surgery, Inc
A dynamic canine model of experimental hip dysplasia. Gross and histological pathology, and the effect of position of immobilization on capital femoral epiphyseal blood flow
PL Schoenecker, PA Lesker and K Ogata
We produced a dynamic model of experimental hip dysplasia in growing
puppies by cast immobilization of a single hind leg with the knee in
extension. Serial roentgenographic studies demonstrated a progressive
acetabular dysplasia with subluxation and eventually dislocation of the
femoral head. A consistent finding in the dysplastic hip was significant
hypertrophy of the ligamentum capitum femoris, both in length and in
cross-sectional area. Quantitative studies of blood flow in the femoral
head by the hydrogen-washout technique in normal and dysplastic hips
demonstrated a significant decrease in blood flow to the dysplastic femoral
heads. The dysplastic hips were then placed in various positions of
immobilization and blood-flow determinations were repeated. The position of
forced abduction significantly reduced circulation in the femoral head,
whereas immobilization in flexion consistently resulted in the highest rate
of blood flow in the femoral head. These experimental data indicate the
potential ischemic hazards of immobilization in the forced abducted
position in the treatment of congenital dislocation of the hip. Progressive
degenerative changes developed in the articular cartilage of the dislocated
joint, with severe reduction of safranin-O staining, fibrocartilaginous
metaplasia, and hypocellularity. The degenerative changes in the acetabular
cartilage were more severe than those in the femoral head. These findings
further emphasize the importance of reducing the dislocated hip at the
earliest opportunity in order to prevent irreversible degenerative changes.