A726. STRATEGY FOR FEMORAL LIFT-UP IN THA THROUGH DIRECT ANTERIOR APPROACH – CADAVER STUDY AND CLINICAL EXPERIENCES

Direct anterior approach (DAA) is an inter-muscular approach that needs no muscle detached. In THA through DAA approach, exposure of the acetabulum is facilitated, while the key points of this approach are femoral lift-up and hip extension to get sufficient access to the femoral canal. To investigate the strategy for femoral lift-up, we released the capsule step by step and measured the distance of femoral lift-up at each step in cadavers and clinical cases. The effects of hip extension on femoral lift-up were also evaluated. Three fresh frozen cadavers were used. In supine position, the hip joint was exposed through DAA by two experienced surgeons. After anterior capsulotomy and femoral head resection, posterior capsule release was performed followed by superior capsule release in one side, and superior release was followed by posterior release in the other side. Finally, internal obturator muscle was released in both side. At each step, the distance of femoral lift-up was measured under the traction force of 70N. The effects of hip extension were investigated in 0, 15 and 25 degrees hyper-extension. Thirty-six THA were performed through DAA. Posterior capsule release was performed followed by superior capsule release in 13 hips, and superior release was followed by posterior release in 23 hips. At each step, the distance of femoral lift-up was measured under the traction force of 70N at each step same as the cadaver study. In cadaver study, anterior capsulotomy and posterior capsule release affected little the femoral lift-up. The distance increased after superior capsular release. The distance decreased as hip hyperextension unless the superior capsule was released. The effect of internal obturator muscle release was not observed. In clinical studies, the same tendency was observed in clinical cases. Superior capsule release was the most effective for the femoral lift-up. The results of this study indicate that superior capsule release is the first step for the femoral liftup. The second step is hip extension to get access to the femoral canal. By performing these procedures step by step, rasping and stem insertion can be achieved with minimal soft tissue release.