Abstract
BACKGROUND: Dislocation is a well-known complication after total hip arthroplasty (THA), with reported rates ranging from 0.12% to 16.1%. This study aims to assess the incidence of dislocation in primary THAs performed with a small femoral head through a posterior approach, in which acetabular positioning was guided by the transverse acetabular ligament (TAL) and supported by meticulous posterior capsular repair. METHODS: Prospectively collected clinical data from all unilateral primary cemented THAs performed between 2005 and 2021 were retrospectively analysed. All procedures were carried out using a posterior approach with posterior soft-tissue repair, and acetabular component alignment was guided intraoperatively by the TAL. Patient demographics and postoperative dislocations were recorded. Functional outcomes were assessed using the Oxford Hip Score (OHS), the SF-12, and the UCLA Activity Score. RESULTS: A total of 1385 patients underwent primary THA with a mean follow-up of 6.6 years. Femoral head sizes used were 22 mm (47.4%), 28 mm (52.2%), and 32 mm (0.28%). The overall dislocation rate was 0.58% (95% CI, 0.25-1.14), with 1.06% (95% CI, 0.43-2.19) in the 22-mm group and 0.14% (95% CI, 0.003-0.78) in the 28-mm group. No dislocations occurred in the 32-mm group (chi-square p = 0.06; Fisher's exact test p = 0.029). All dislocations were posterior and were successfully managed with closed reduction, with no recurrence or need for revision. Functional outcomes improved markedly: OHS increased from 18.0 to 37.2, SF-12 from 30.4 to 63.2, and UCLA from 1.8 to 6.6 at one year. CONCLUSION: Primary total hip arthroplasty performed through a posterior approach using small femoral heads, with posterior capsular repair and transverse acetabular ligament-guided acetabular alignment, was associated with very low dislocation rates. The results are most applicable to high-volume surgeons and centres using a standardised posterior approach with TAL guidance.