Introduction: Bipolar hemiarthroplasty (BHA) is widely used for femoral neck fractures, particularly in elderly patients. However, complications such as the rare dissociation of the bipolar cup can severely impact outcomes. This study aims to investigate iatrogenic BHA dissociation following closed reduction, identify risk factors, and discuss preventive strategies. Material and Methods: A retrospective study was conducted on patients who underwent BHA for femoral neck fractures at our institution between 2019 and 2024. Included patients had a minimum post-operative survival of 3 months. Parameters analyzed included demographics, comorbidities, implant design, dislocation characteristics, and revision procedures. Results: Among 490 patients who underwent BHA, 64 dislocation episodes were identified. The incidence of component dissociation related to closed reduction was 20.3%, representing 13 iatrogenic cases. One patient experienced two episodes of dissociation. The mean Charlson comorbidity index was 6.0, indicating a high comorbidity burden. All dissociations involved implants with a single circumferential polyethylene locking ring. The “O-shape sign” was evident in nine cases. Revision procedures included total hip arthroplasty, open reduction with component replacement, or Girdlestone resection arthroplasty. Conclusion: Iatrogenic dissociation of BHA following closed reduction, though rare, represents a serious complication with significant clinical implications. This study highlights the critical role of implant design, particularly single locking mechanisms, in increasing dissociation risk. Careful pre-reduction assessment, use of fluoroscopic guidance, and awareness of radiographic risk signs are vital to prevention. Multidisciplinary management addressing frailty and comorbidities is essential for optimizing outcomes. Keywords: Bipolar hemiarthroplasty, dissociation, dislocation, closed reduction, polyethylene locking ring.
Rodrigues et al. (Thu,) studied this question.