Dislocation after primary unilateral total hip arthroplasty - hip geometry and risk factors (a matched cohort analysis)

Introduction/Objective The purpose of this study was to determine if patient-related factors, such as hospitalization length and preoperative use of walking aids, and geometrical factors, measured with antero-posterior radiographs of hip, affect the risk of hip dislocation after total hip arthroplasty. Methods A total of 36 of 433 (8.31%) patients with hip dislocation were identified in the institutional registry during a two-year period. The data for patients with and without hip dislocation were matched and compared. Results Hip dislocation more often occurred in patients who had used walking aids before the operation compared to the ones who had not (p < 0.001). Also, a difference in the number of hip dislocations was noticed between the patients who stayed longer in the hospital after THA (p < 0.001). The patients with higher acetabular inclination angle (p < 0.005) and height of greater trochanter (p < 0.001) on radiographs had been more prone to hip dislocation. In addition to this, the "safe-zone" was not identified in our study (p > 0.005). Conclusion Several factors which influence hip dislocation were identified in this study: patient characteristics and radiograph characteristics. Both groups of factors require attention and monitoring in future studies.