Abstract
Abstract
OBJECTIVES
Hip dislocations remain one of the most common complications of total-hip-arthroplasty (Zahar et al.,2013). There is contradicting evidence whether the surgical approach affects dislocation rates (Sheth et al., 2015; Maratt, 2018). The aim of this study was to develop instrumentation to measure hip forces during simulated range-of-motion tests where the hip was forced to dislocate in cadaveric specimen.
METHODS
A total-hip-replacement was completed on both hips of a single cadaveric specimen by a trained orthopaedic surgeon during a lab initiated by DePuy. A direct-anterior surgical approach was performed on the right leg and a posterior approach was performed on the left. Before final implantation of the femoral component, a trial reduction with a femoral neck trial was performed. The neck trial was modified with strain gauges placed around the shaft which were designed to measure resultant hip forces throughout the range-of-motion assessment. A force-calibration was performed using a calibration-block to convert strain to force values.
RESULTS
The developed method was able to measure joint forces. Initially the leg was flexed which led to a decrease of joint force for the load component in direction of the neck-axis which was the predominant force during hip dislocation. The leg was subsequently rotated internally which led to a sharp increase with maximum forces of 150N for the direct-anterior approach and 130N for posterior approach. The average absolute calibration error was 6.7%.
CONCLUSIONS
The peak force in neck direction was slightly higher for the direct-anterior approach compared to the posterior approach which indicates that the soft tissue tension was potentially higher. Limitations of this study were potentially lower soft tissue tension of cadaveric specimens, the sample size and low calibration accuracy. Component position was not assessed, which is another significant contributor to joint stability. However, the data will be useful for enhanced understanding of dislocation mechanisms.
Declaration of Interest
(a) fully declare any financial or other potential conflict of interest
