[Risk factors for total hip arthroplasty dislocation and its functional outcomes].

OBJECTIVES To evaluate risk factors for dislocation after primary total hip arthroplasty (THA), and its functional outcomes. MATERIAL AND METHODS A retrospective study was conducted on 22 cases with dislocation and 431 controls without dislocation, all performed with lateral access. The data were collected prospectively with a minimum follow-up of 5 years. Patient related factors, from primary surgery, and position of components on simple radiographs were analyzed. Harris and Merle D'Aubigné hip scores, and short Womac questionnaire were used. RESULTS Demographic, patient-related or surgical technique factors were not risk predictors of dislocation. With regard to position of components, an acetabular abduction >50° (p = 0.003) and anteversion lower or higher than 10°- 20° (p = 0.044) were risk factors. Controls and dislocation treated conservatively had similar outcomes, and in both were better than in those treated with surgical revision (p = 0.03). DISCUSSION Factors relating to the patient and soft tissues status may influence the stability of the arthroplasty, but malposition of the acetabular component seems to be the most important and common risk factor for dislocation.