Influence of Implant Acetabular Component Orientation on Hip Stability

Abstract

Introduction. Acetabular component malposition at total hip arthroplasty is a common situation that may affect the frequency of dislocation and the rate of implant friction unit wear. The purpose of the study was to determine the influence of different factors on the variability of acetabular component orientation and evaluate the role of orientation in dislocation development. Patients and methods. Total number of patients made up 1408. Out of them 695 patients were operated on at RSRITO named after R.R. Vreden using standard approaches (group 1), 184 - using low invasive approach (group 2) and 55 patients were admitted with implant head dislocation (group 4). At City St. Petersburg hospitals 474 patients (group 3) were operated on. Orientation of acetabular component (inclination and anteversion angles) was evaluated on digital pelvis and plain hip roentgenograms. Dispersion unifactorial analysis was used to evaluate the dependence of the precision of acetabular component positioning upon the surgeon’s experience, patient’s body mass index, type of surgical approach and the use of guide for acetabular component implantation. Results. Within the first postoperative year the rate of femoral component dislocation in group 1 made up 0.9%. Within the Lewinnek safe zone 76.6% of acetabular components were implanted with the use of a guide and 71.8% without. The rate of dislocation in group 2 made up 71.8% and 63.4% of components were implanted within the safe zone. In group 3 the intra-hospitalization dislocation developed in 1.9% of patients and satisfactory positioning relative to Lewinnek safe zone was achieved in 68.2% of cases. The risk factors for acetabular component malposition included high body mass indices, use of low invasive approach and insufficient experience of the operating surgeon. No direct influence of acetabular component orientation upon the femoral component dislocation was detected. Conclusion. Further studies directed to the more detailed analysis of additional factors that either directly or indirectly affect the implant function and to the optimization of surgical technique that would enable the reproducibility of total hip arthroplasty results are required.