Dual mobility cups associated with proximal femoral replacement in nontumoral indications: Results and complications.

Introduction: Reconstruction of extensive proximal femoral bone loss is a major challenge during total hip arthroplasty (THA). Proximal femoral replacement (PFR), initially used for bone tumors, is an alternative to allograft-prosthetic composite reconstruction. However, PFRs present a high complication rate, particularly related to dislocation. Moreover, dual mobility cups (DMCs) are effective in preventing dislocation, and no study has yet assessed their association with PFRs. Therefore, the aim of this study was to assess the dislocation and complication rates in THA using PFRs with DMCs.
Hypothesis: The use of a DMC decreases the dislocation rate associated with PFRs in nontumoral indications.
Methods: From 2008 to 2017, 66 PFRs associated with a DMC (40 women, mean age=71 years [26-94]) were included in our total joint registry and retrospectively reviewed. The main indications were complex periprosthetic and pertrochanteric fractures (26 THAs, 40%), aseptic loosening (22 THAs, 33%) and periprosthetic joint infections (18 THAs, 27%). A single design of PFR implant was used (Global Modular Replacement System (GMRS), Stryker, Mahwah, NJ, USA) with an uncemented stem in 54 THAs (82%).
Results: Eighteen complications (27%) were reported at a mean follow-up of 4.6 years [2-10]: 5 dislocations (7.5%), 9 periprosthetic joint infections (13.6%), 2 aseptic loosening (3%) and 2 femur fractures (3%). Overall survivorship at 5 years was 72% (95% CI: 58-82). Survivorship free from dislocation was 94% (95% CI: 85-98) at 1 year. The mean Harris Hip Score was 70±16.4 [26-100] at latest follow-up.
Conclusion: The use of DMCs limits the risk of PFR dislocation, in comparison to other series in the literature that used large femoral heads, without compromising implant survivorship. In addition, DMCs make it possible to overcome the potential risks of mechanical failure associated with constrained acetabular components.
Level of Evidence: IV; retrospective cohort.
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