Instability after hip hemiarthroplasty for femoral neck fracture: an unresolved problem

Background: The dislocated hip hemiarthroplasty (HA) remains a difficult condition to treat owing to frailty, comorbidity, poor quality of bone and soft tissues. We aimed to identify parameters contributing to instability following hip HA and describe the operative management and patient outcomes. Methods: We retrospectively reviewed consecutive cases of all patients with hip fracture treated between 2004 and 2019 at a single tertiary care institution. We propensity matched patients with and without hip dislocations on a 1:2 basis for age, sex, and approach. We reviewed risk factors for HA dislocation, performed radiographic measurements, and recorded management of dislocation and further complications. Results: Of the 1472 patients treated with HA, we included 18 patients (1.2%) who sustained at least 1 dislocation in our analysis. Of the dislocations identified, 13 and 17 occurred within 1 and 3 months postoperative, respectively. The presence of dementia and low preoperative lateral centre-edge angle were associated with increased risk of dislocation. The 2-year mortality rate was significantly higher in the dislocation group (n = 9) than the control group (n = 2) (p = 0.0003). Nine of 18 (50%) patients were treated with an initial closed reduction; 5 of these 9 (56%) sustained further dislocations and required additional treatment. Six of 18 cases were treated with a total hip arthroplasty after their first dislocation. By final follow-up, 2 of 18 patients had Girdlestone procedures. Conclusion: This study highlights patient factors associated with increased dislocation risk following hip HA. A thorough preoperative assessment is indicated when presented with dislocated HA to prevent further complications.