Influence of femoral head diameter on intraoperative range of motion in total hip arthroplasty

Abstract

PurposeTo investigate the intraoperative change of range of motion (ROM) using different femoral ball head diameters in the same patient using a navigation system and to compare the postoperative ROM speculated by 3D computer simulation software and the actual intraoperative ROM. Materials and methodsFourteen patients (12 female and 2 male patients) who underwent one-sided primary total hip arthroplasty for hip osteoarthritis caused by developmental dysplasia of the hip from January 2016 to November 2017 were included. Dislocation was defined as the center of femoral head moved by 5 mm. After placing the cup and stem via the posterolateral approach, measurement of the ROM with 28-, 32-, and 36-mm-diameter femoral ball heads was carried out using the navigation system. Postoperative computed tomography (CT) was performed, and the ROM simulation of the same movement was measured intraoperatively using a small-sized ball head (ZedHip). ResultsThe intraoperative ROM was approximately closed to the preoperative ROM, and it tended to be in the following order: preoperative<28-mm head<32-mm head. As the diameter of the femoral head increased, the abduction increased significantly (p < 0.05). None reached 80% of the ROM simulated by ZedHip, and the movements that obtained 50% or more in the simulated ROM were flexion, abduction, and the angle until the dislocation. ConclusionsROM expansion due to the increase in femoral ball head diameter can be obtained even in vivo, but it was suggested that there is a limitation to the effect because of the interference of bone and soft tissue.