Leg length control in total hip replacement with CT-free computed assisted surgery

摘要

Introduction: Ideally, leg lengths should be equal after total hip arthroplasty. However, achieving this goal can be difficult, and leg-length discrepancy has been among the most common causes of litigation after primary total hip arthroplasty. Multitudes of different preoperative and intra-operative techniques have been described for maintaining appropriate leg lengths during total hip arthroplasty (intra-operative x-rays or ultrasounds (1), mechanical devices, etc.). Accurate preoperative templating (2), appropriate component selection and positioning and intra-operative diligence in restoring hip anatomy can minimize the chance of limb length discrepancy. However there are circumstances in which lengthening of the extremity results from the need to, obtain optimal soft- tissues tension and to afford stability to the prosthetic hip (3). Recently computer assisted surgery has been introduced in total hip replacement. Different Authors report good results in positioning the cup in the correct anteversion and inclination angles (4). The purpose of this work was to verify the possibility of the navigation system to have a intra-operative control of the leg length. Material and methods: 40 patients were included in the present study. They all underwent total hip arthroplasty (Depuy, Warsaw, IN - Pinnacle cup, G2 or Corail stems) through a postero-lateral approach. We used the navigation system Brainlab, Vector Vision supported by the software Hip 3.1 CT-free. The navigation system calculates the preoperative center of rotation of the hip determined by pivoting. The mechanical axis of the femur goes from the center of rotation to the mid-point of the epicondylar axis. The epicondylar axis is denned by two points, which have been acquired during femur registration corresponding to the medial and lateral epicondyles.