Download The Innominate Tubercle and Superimposition of the Rasp – an

The Innominate Tubercle and Superimposition of the Rasp – an Accurate Technique for the
Femoral Neck Osteotomy during the Direct Anterior Approach to the Hip
R Williams, M Goodson, M Maheson
Department of Orthopaedic Surgery, University Hospital of Wales, Cardiff, UK INTRODUCTION The increasingly popular Direct Anterior Approach is the only true internervous and intermuscular approach to the hip. Technical challenges in achieving an accurate femoral neck osteotomy have been described with this approach. OBJECTIVES We describe a new technique combining the superimposi1on of the femoral rasp on the proximal femur in addi1on to using the “Innominate Tubercle”, a landmark on the anterolateral aspect of the greater trochanter, as a reliable method of referencing the femoral neck osteotomy. METHODS In a consecu1ve single surgeon series of 151 pa1ents, the Innominate Tubercle was used as the lateral reference point for the femoral cut. The Innominate Tubercle was iden1fied ini1ally by palpa1on and then verified with image intensifier. To delineate the neck osteotomy angle, we then place a femoral rasp, with a trial neck and head aFached, on the anterior soG 1ssue envelope and use image intensifier superimposi1on. We use leg length discrepancy as a surrogate marker of the accuracy of the femoral neck osteotomy. A validated method of measuring leg length discrepancy on postopera1ve radiographs was performed on pa1ents in the series. The Innominate Tubercle of the Proximal Femur A prominence occurs at the junc1on of the upper part of the neck with the greater trochanter; it is the point of mee1ng of five muscles: the Gluteus minimus laterally, the Vastus lateralis below, and the tendon of the Obturator internus and two Gemelli above. RESULTS Our series of 151 hips, preformed via the direct anterior approach u1lising the innominate tubercle as a landmark and radiographic superimposi1on of the trial rasp, showed a leg length discrepancy range of -­‐3 to +3mm with a mean of +1.7 mm. CONCLUSION The new technique of radiological superimposi1on of the femoral rasp guides the neck osteotomy. In addi1on, the Innominate Tubercle provides a reliable landmark for precise referencing of the lateral femoral neck osteotomy.