gms | German Medical Science

Objective: Dislocation following revision total hip arthroplasty is a serious complication and the primary cause for revision surgery after two-stage exchange total hip arthroplasty (THA) due to periprosthetic joint infection (PJI).

The aims of our study were (1) to determine the incidence of dislocation after two-stage THA reimplantation without spacer placement, (2) to evaluate relevant risk factors for dislocation and (3) to assess the efficacy of dual-mobility constructs to mitigate instability.

Methods: We prospectively analyzed 187 patients who underwent a two-stage revision THA after being diagnosed with PJI from 2013 to 2019. 36 patients (19%) received a dual-mobility construct. The mean duration of follow-up was 54.2±24.9 months (>36 months). The incidence of postoperative dislocation and subsequent revision was estimated through Kaplan-Meier curves and potential risk factors were identified using Cox hazard regression. The functional outcome of the patients was assessed using the modified Harris Hip Score (mHHS).

Results: The estimated cumulative dislocation-free survival was 87.2% (95% CI: 81.2%–91.3%) with an estimated 10% and 12% risk for dislocation within the first 6 and 12 months, respectively. The use of a dual-mobility construct had no significant impact on the dislocation rate. Increasing body mass index (BMI) (HR=1.11, 95% CI: 1.02–1.19, p=0.011), abductor mechanism impairment (HR=2.85, 95% CI: 1.01–8.01, p=0.047), the extent of elongation of the affected extremity between stages (HR=1.04, 95% CI: 1.01–1.07, p=0.017), the final leg length discrepancy (HR=1.04, 95% CI: 1.01–1.08, p=0.018) and PJI recurrence (HR=2.76, 95% CI: 1.00–7.62, p=0.049) were found to be significant risk factors for dislocation. Overall revision rates were 17%. Unstable hips were 62% more likely to undergo re-revision surgery (p<0.001, Log-rank= 78.05). A significant average increase of 30 points in mHHS scores after second-stage reimplantation (p=0.001, Wilcoxon-rank) was recorded, but no difference in the final HHS measurements between stable and unstable hips.

Conclusion: Dislocation rates after two-stage THA reimplantation remain high independent of the use of dual-mobility constructs. Besides careful leg length restoration, an intact abductor mechanism appears to be critical to ensure stability in these complex patients.