Low dislocation rate one year after total hip arthroplasty at a tertiary hospital in South Africa

Abstract

Background: Total hip arthroplasty (THA) is one of the most performed and most researched procedures worldwide, and there is an ever-growing demand for THA in an already resource-constrained system in South Africa. Early dislocation after THA remains a serious and costly problem; however, few THA outcome studies have been performed locally. This study therefore aimed to calculate the incidence of dislocation after THA and to identify risk factors for dislocation after THA in a South African academic hospital.

Methods: In this retrospective cohort review, files and radiographs of 543 patients were reviewed for dislocation during the first year after primary THA. The reason for the THA, the surgical data, the implant data, and whether and when dislocation occurred were recorded for each patient. Fisher’s exact tests and independent t-tests were done to analyse the association between variables and a patient’s odds of experiencing a dislocation after THA.

Results: Twenty (3.7%) out of 543 THAs dislocated during the first year, 17 of these within the first three months. The surgical approach used was not shown to be a significant risk factor (p = 0.650) for dislocation, although the Hardinge approach had been used for all 20 cases of dislocation. Similar dislocation rates (p = 0.967) were found for THAs done for displaced neck of femur (NOF) fractures (3.6%) and for elective THAs (3.7%). Trauma THAs made up more than half (55%) of our study population. Femoral head sizes ≤ 32 mm (p = 0.390 for neck of femur THA and p = 0.451 for elective THA) and a single mobility design (p = 0.494) both produced a higher dislocation rate, although this was not statistically significant. Surgeon experience did not prove to be significant for our study population (p = 0.570).

Conclusion: The dislocation rate after THA at our institution is lower than rates reported in the literature for NOF THA and similar to rates reported for elective THA. This was found despite the dislocation rate for the Hardinge approach being nearly eight times higher than expected. Minimal surgeon experience, implant coupling and smaller femoral head size did not prove to be significant risk factors for dislocation after THA.

Level of evidence: Level 4