Incidence of Hip Dislocation Following Bipolar Hemiarthroplasty via Posterior Approach in Patients With and Without Abductor Pillow Use: A Retrospective Cohort Study

Abstract

This study aimed to descriptively compare the incidence of hip dislocation between patients managed with and without abductor pillows following BHA via a posterior approach. This retrospective cohort study included 48 patients who underwent BHA via a posterior approach, performed by a single surgeon at Sirindhorn Hospital, Khon Kaen, from January 1, 2018 to May 1, 2025. Patients were divided into two groups: those managed with abductor pillows (n=15) and those without (n=33). All patients were followed for at least 12 weeks. Data were analyzed using descriptive and inferential statistics Chi-square test or Fisher's exact test, and 95% confidence intervals were estimated using the Rule of Three for zero-event outcomes. No instances of postoperative dislocation were observed in either group during the follow-up period (0%). Baseline characteristics, including age (mean 71.7 years), sex, comorbidities, surgical side, ASA classification, and length of hospital stay, showed no statistically significant differences between the two groups. The upper limits of the 95% CI (Rule of Three) were 20.0% and 9.1% for the abductor pillow and non-abductor pillow groups, respectively, and 6.25% for the entire cohort. Although no dislocations were observed in this cohort following BHA with meticulous posterior soft tissue repair, regardless of abductor pillow use, the study is underpowered to detect rare complications given the small sample size and absence of events, and a clinically meaningful risk of dislocation cannot be excluded. Larger prospective studies are required to confirm these findings and further refine postoperative care protocols.