Tip to Apex Distance in DHS Fixation. An audit of practice at a district general hospital.

摘要

BackgroundDynamic hip screw is still one of the most widely used devices for the fixation of extra-capsular neck of femur fractures. A recognised complication with this device, is the screw cut-out from the femoral head.The tip to apex distance has been shown to be the most reliable predicting factor of screw cut-out. A distance of less than 25 mm is generally predictive of a successful result. Aim The purpose of this audit was to assess the position of the lag screw, in dynamic hip screws performed in a district general hospital and to assess if the principle of tip to apex distance is put into practice. Method We used our theatre logbooks to retrospectively identify all consecutive patients who underwent DHS fixation over the period of Aug08- Nov08. The tip?apex distance for every DHS was measured using the intra-operative radiographs.The results were presented in a departmental audit meeting and the importance of tip- apex distance was emphasized.The audit cycle was repeated 3 months later between Mar09 and Jun09. ResultsIn the first cycle, 36 patients were studied. 9 out of 36 (25%) had a tip-apex distance of more than 25mm and there were 3 cut-outs requiring revision surgery.In the second cycle, 31 patients were studied. 5 out of 31 (16%) had a tip-apex distance of more than 25mm and there was 1 cut-out. ConclusionBy simply raising awareness and emphasising the importance of the tip-apex distance, we lowered our DHS cut-out rate, improving patients? safety and quality of life. We recommend that the tip-apex distance principle is emphasised and regularly re-enforced to all orthopaedic trainees, in order to improve the outcome of dynamic hip screws in patients with neck of femur fractures. Introduction Hip fractures remain one of the major causes of mortality and morbidity in the elderly population1. Dynamic hip screw (DHS) has been a successful device used in treating intertrochanteric hip fractures since the 1970s and is still one of the commonest trauma devices used to date. It allows controlled impaction of the fracture to a stable position whilst maintaining the neck to shaft angle. Despite been a highly successful device, it has a rate of mechanical failure which has been reported between 16 and 23%2. The commonest mechanism of failure of a DHS is to “cut out” from the femoral head. Many factors have been identified as causes for its mechanical failure, including quality of bone, patient age, fracture pattern, adequate fracture reduction and lag screw position.The most reliable predictor of mechanical failure in a DHS is the tip to apex distance (TAD)2. This measurement is the sum of the distance from the tip of the lag screw to the tip of the femoral head on the anterior-posterior and lateral intra-operative radiographs allowing for magnification (fig1).