Risk Factors for Dislocation After Direct Anterior Total Hip Arthroplasty

Abstract

Background: Dislocation is a leading indication for revision total hip arthroplasty (THA). Several patient factors, implant choices, and radiographic outcomes, including abnormal spinopelvic motion, have been linked to instability following posterior approach THA. To date, no study has analyzed these factors in an exclusively direct anterior approach (DAA) cohort. This study aimed to identify demographic, radiographic, and implant-related factors associated with postoperative dislocation in patients undergoing primary THA through the DAA. Methods: Patients who underwent primary THA via DAA for osteoarthritis from January 2012 to December 2022, complicated by postoperative dislocation (THA+D), were retrospectively reviewed. Demographics, surgical variables, and radiographic parameters were recorded. The 27 identified THA+D patients were matched 1:2 on age, sex, body mass index, and Charlson Comorbidity Index to a control group who underwent THA via DAA for osteoarthritis without postoperative dislocation (controls). Results: The THA+D patients had a higher prevalence of radiographically confirmed lumbar fusion (odds ratio 10.5, 95% confidence interval 2.4 to 45.5; P = 0.0016). There were no significant differences in other patient (diagnosis of lumbar degenerative disease, narcotic use), implant (head size, acetabular diameter, neck length), or radiographic (leg-length or offset change, acetabular inclination or anteversion) characteristics between the groups. Conclusions: This study demonstrates that spinal fusion may be a risk factor for dislocation after DAA THA. Furthermore, although no association between radiographic or implant-related factors and postoperative dislocation was observed in our sample, the limited number of cases may preclude definitive conclusions. Level of Evidence: Therapeutic study, Level III (retrospective cohort study).