NEGLECTED CONGENITAL DISLOCATION OF THE HIP - ROLE OF COMPUTED-TOMOGRAPHY AND COMPUTER-AIDED-DESIGN FOR TOTAL HIP-ARTHROPLASTY

Computed tomography (CT) provides important three-dimensional anatomic details in congenital dislocation of the hip that are useful for tota l hip arthroplasty (THR) and are not obtainable with conventional radi ographic evaluation. In this study 84 patients (119 hips) with congeni tal dislocation of the hip were evaluated with CT before surgery. Spec ifically, both the acetabulum and the femur were analyzed to make the best selection of the prosthesis. The average anteversion of the aceta bulum was 23 degrees, with an opening of 30.9 mm and a depth of 14.7 m m. The bone stock of the true acetabulum was calculated and the averag e available diameter for the acetabular implant was 44.9 mm. The CT to pogram revealed the true leg-length discrepancy (average, 0.5-1.9 cm), and the amount of a shortening osteotomy when necessary was determine d. Finally, to determine the stem with optimum fit and fill, a three-d imensional reconstruction of the femoral canal using CT data and compu ter-aided design (CAD) was matched with a three-dimensional geometry o f several stem designs and sizes obtained from a CAD system.