Planning acetabular redirection osteotomies based on joint contact pressures

Acetabular redirection osteotomy can be used to relieve pain, improve funct ion, and extend the life of dysplastic hip joints. To understand better the factors that may determine the acetabular reorientation that minimizes pre ssures, joint contact pressures were calculated by computer assisted method s in 70 dysplastic and 12 normal hips (82 patients). Calculated pressures w ere consistent with pressures estimated and measured by other investigators . Contact areas were 26% smaller, and contact pressures were 23% higher, in the dysplastic hips compared with the normal hips. When the acetabula were reoriented to minimize contact pressures for an activity such as the midst ance phase of gait, then contact pressures were elevated for dissimilar act ivities such as stair ascent. Contact pressures in the dysplastic hips were reduced when the acetabula were rotated in the frontal plane to increase l ateral coverage or rotated in the sagittal plane to increase anterior cover age. In most of the dysplastic hips, contact pressures were reduced twice a s much when the acetabulum was rotated in the frontal and the sagittal plan es. Computer assisted methods to quantify joint contact pressures can be us ed to assess potential candidates for reconstruction, plan acetabular redir ection surgery, and possibly may improve the long term success of acetabula r redirection osteotomy.