Epidemiology of dislocation after total hip arthroplasty

Instability after total hip arthroplasty is an important complication. It usually occurs in the immediate postoperative period, but the risk also increases with time. There are numerous surgical treatment options, but they have relatively unpredictable outcomes. Numerous factors are associated with dislocation, but research has mainly focused on surgical factors. Epidemiological factors remain the subject of much debate. We aimed to establish the most significant epidemiological factors in Scotland and in particular the dislocation rate in neuromuscular conditions. The Scottish National arthroplasty nonvoluntary registry is based on SMR01 records (Scottish Morbidity Record) data. We analyzed the Scottish National Arthroplasty Project to find patients' dislocation rates up to 1 year postoperatively for surgeon volume, age, gender, previous surgery, diagnosis, and followup duration. There were 14,314 total hip arthroplasties performed from April 1996 to March 2004 with an annual incidence of dislocation of 1.9%. We found an association between rate of dislocation with age, surgical volume, and previous fracture. However, there was no increase in the rate of dislocation associated with gender or with diagnoses of stroke or Parkinson's disease. Our prognostic assessment of dislocation risk allows assessment for methods of reducing dislocation in high risk patients.