Ischemic necrosis as a complication of treatment of C.D.H.

Ischemic necrosis is seen after both closed and open reduction. Its causes have been clarified during the last two decades. The position of the immobilized hip after reduction is an important factor; the method of reduction is another. There are other factors such as development of the epiphyseal nucleus and the degree of dislocation. In a collective series of 20 hospitals our study group on hip dysplasia investigated 3316 hip joints reduced by different techniques. It was shown that methods working with the Lorenz position of immobilization have an average rate of 27% ischemic necrosis. Lange's position of abduction with internal rotation, without flexion of the hip joint, has a 17% necrosis rate. Pavlik's harness, as a more functional method, had a 7% rate. Methods reducing bij increased flexion and less abduction, such as that of Fettweis, Hanausek and Krämer, had 2% on the average. The percentage of necrosis was increased with the degree of dislocation. The length of time of immobilization had no influence. These findings correspond with the investigations on the femoral blood circulation in different positions of the femoral head and under pressure that have been published by Schoenecker et al. and Law et al. The cartilaginous epiphysis may be squeezed so much that the circulation is interrupted. Another cause is direct pressure to epiphyseal vessels in extreme Lorenz and Lange positions (Ogden and others). There has been a question as to what degree the reduction itself is the cause of ischemic necrosis. The method of reduction was determined by arthrography. If it seemed possible, a cast in squatting position according to the method of Fettweis was applied immediately. In the beginning we even allowed the joints to reduce themselves slowly against a narrow introitus of the joint. In other joints traction was applied first, and in a few older patients open reduction was performed immediately. A total of 388 joints was evaluated. There was an increasing rate of ischemic necrosis from open acetabular inlets (3.6% necrosis) to constricted joints (8.5%) and those with an inverted upperlabrum (31%). The width of the acetabular introitus, as measured between the upper and lower labrum (ligamentum transversum), also showed a correlation with ischemic necrosis. When the degree of reduction is classified as "deeply seated", there is a definite correlation with ischemic necrosis. Also when the distance of the femoral head from the acetabular floor is measured, the same increase in incidence of necrosis is noted.(ABSTRACT TRUNCATED AT 400 WORDS)