Reliability and reproducibility of a simplified leg length measurement algorithm in total hip arthroplasty

摘要

Introduction: Leg length inequality is a major source of dysfunction and dissatisfaction following THAI, 2,3. Mechanical methods of measuring leg length change during surgery can be unreliable. Variation in flexion/extension, internal/external rotation, and adduction/abduction between the pre- and post-reconstruction mechanical measurements can lead to significant measurement error4. Prior computer-assisted methods of measuring leg-length change during surgery have also had significant problems. These methods have typically required the establishment of coordinate systems for both the pelvis and femur, calling for calculation of the hip joint center. Unfortunately, since the hip joint is usually destroyed, calculating the center of the hip joint is often impossible. Further, establishment of the femoral coordinate system is time-consuming. To address these problems, a method was developed where the position of the femur is tracked in the pelvic coordinate system before and after reconstruction. This allows for calculation of leg length change during surgery without having to calculate the center of the hip joint or to establish a femoral coordinate system. This method also ensures that the leg is placed in the exact same orientation relative to the pelvis before and after reconstruction. Moreover, the method can be applied to any method of navigation whether image-free or image-based. The advent of a simple and accurate method of measuring leg length change during total hip arthroplasty may solve one of the most common problems associated with this surgery. The current study assesses leg length change measured using the algorithm compared to leg length change measured using magnification-corrected radiographs.