The hip in adults with classic bladder exstrophy: A biomechanical analysis

We studied the untreated pelvic deformity in 14 adult patients with bladder exstrophy to determine the relative hip-joint force and stress and their e ffects on the clinical status of the hip. Pelvic radiographs were used for biomechanical analysis to calculate joint force and joint stress (force/are a) relative to partial body weight, which allowed comparison between patien ts and age-matched controls. IOWA hip ratings were used for clinical evalua tion, and hips were scored radiographically for degenerative joint disease. The mean relative joint force and joint stress was significantly higher fo r exstrophy patients (p < 0.001). In addition, the mean distance from the b ody center to the center of the femoral head was significantly increased (p < 0.001) in bladder exstrophy patients. An increase in diastasis correlate d with an approximate 30% increase in the distance from the center of the f emoral head to the body midline. The mean distance from the greater trochan ter to the femoral head center was significantly less (p < 0.02) and the ce nter-edge angle was significantly decreased in exstrophy patients (p < 0.05 ). Two patients' hips showed significant subluxation, and one of these show ed degenerative hip disease in association with poor IOWA and radiographic scores. The force and stress on the hip joint are increased in untreated ad ult bladder exstrophy patients. Further longitudinal study is indicated to validate these findings and to determine whether clinically important degen erative changes are occurring. This could affect treatment recommendations in childhood.