[Risk of Hip Dislocation - which Patients Need Special Treatment?].

Introduction: Dislocation of a hip arthroplasty is one of the main complications after primary or revision surgery. Definition of specific risk factors concerning patient, indication and surgery makes it possible to determine risk patients for dislocation.

Aim: The aim of this study is to identify patient-specific risk factors, such as body mass index (BMI), age and gender, in order to evaluate primary dislocation and to correlate with secondary dislocation. It is investigated whether high BMI, advanced age or female gender are able to promote secondary dislocation.

Method: In order to identify risk factors for dislocation after primary and revision hip arthroplasty, a retrospective analysis for dislocation was performed of all hip arthroplasties treated in our hospital between 2007 and 2011. 106 patients without an indication for surgical revision were included and treated conservatively. The patient cohort was divided into two groups, depending on the success of the therapy and were analysed for BMI, age and gender. Group I (n = 32) included patients without a re-dislocation event, in contrast to group II (n = 74), which included patients with re-dislocation of the hip arthroplasty.

Results: The mean age at the time of primary dislocation was 68 ± 14 years (32 % male and 68 % female). Re-dislocation was presented in 74 cases (70 %). Group II showed a significantly higher BMI (27.11 ± 6.24 kg/m(2)) than group I (24.49 ± 4.86 kg/m(2); p = 0.02). There was no significant effect of age (p = 0.70). The mean age in group I was 71 ± 16 years and in group II of 70 ± 13 years. The incidence of hip dislocation was 2.33-fold higher in women than in men. There was no significant difference between the genders with respect to the risk of re-dislocation.

Summary: A higher BMI correlates significantly with a greater risk of re-dislocation of a hip arthroplasty. On the other hand, age and gender do not influence the risk. However, the dislocation of a hip arthroplasty is a multifactorial event, which can be influenced by patient-specific factors as well as specific factors for indication and operation technique.