Radiographic assessment of femoral, acetabular and global offset following hip spacer implantation in staged total hip arthroplasty”

Background The number of total hip arthroplasties (THAs) performed worldwide is steadily increasing, and, consequently, the demand for revision procedures is expected to rise as well. two-stage revision procedure continues to be considered the gold standard in many clinical scenarios. During the first step, failure to restore femoral offset has been implicated as a contributor to instability and mechanical failure, although a clear consensus is still lacking. Objectives The primary aim of this study is to evaluate the restoration of biomechanical parameters of the hip—specifically leg length discrepancy (LLD), femoral offset (FO), acetabular offset (AO), and global offset (GO)—following implantation of a specific type of articulating hip spacer during the first stage of a two-stage revision for PJI. A secondary objective is to assess the correlation between variations in offset parameters and the rate of interstage mechanical complications. Materials and methods We retrospectively reviewed all patients undergoing staged revision with a specific articulating spacer between 2020 and 2022 at a single institution. Harris Hip Scores, Oxford Hip Scores, and Visual Analogue Scales for pain were obtained at different time points. Radiographic analysis included LLD, FO, AO and GO measurements on the affected (spacer and post-reimplantation) and the contralateral side. Complications were recorded during the interstage and post-reimplantation period. Results Forty-seven patients (47 hips), were enrolled. The mean follow-up was 25.3 months. Clinical outcomes showed significant improvement from pre-operative visit to interim period and at the last follow-up ( p < 0.01). No statistically significant differences for FO, AO and GO between contralateral and spacer side were observed. LLD before reimplantation was 10.1 ± 7.5 mm. GO increased of 4 ± 3.2 mm at final follow-up ( p < 0.05) with a final LLD of 5.6 ± 4.9 mm. Six complications (12.8%) occurred during the interstage period: 4 spacer dislocations (8.5%) and 2 intraoperative femoral peri-spacer fractures (4.3%). Comparison between stable and dislocated spacers showed statistically significant differences for mean ΔFO ( p = 0.02) and ΔGO ( p = 0.04). Conclusion The articulated spacer assessed in this study, especially when used in combination with a custom-made acetabular component, allowed approximation of the main biomechanical parameters, with small, non-significant differences compared to the contralateral side. Offset parameters reduction may be associated with spacer dislocation rate.