Total hip arthroplasty with exclusive use of dual-mobility cup after failure of internal fixation in trochanteric fracture

Introduction: Failure of internal fixation in trochanteric fracture (or extracapsular proximal femoral fracture: PFF) is a serious complication often requiring total hip arthroplasty (THA). THA after PPF incurs a higher risk of complications than in intracapsular fracture due to frequent impact on local anatomy, notably with risk of implant dislocation. Recent studies demonstrated a protective effect of dual-mobility (DM) cups against instability in these cases but in a population mixing failure of internal fixation in intra and extracapsular fractures. We therefore conducted a retrospective study focusing on fixation failure in PFF: 1) to assess surgical complications and notably dislocation rate using DM cups, and 2) to analyse the characteristics of the initial fixation and assess conformity with established standards. Hypothesis: DM cups exert a protective effect in PFF fixation failure at high risk of instability. Materials and methods: A single-centre retrospective study included 40 cases over a 10-year period: 30 women, 10 men; mean age, 77 years [range, 31-91 years]. All THAs used DM cups. Approaches were transgluteal in 24 cases, posterior in 15 and anterolateral in one. Clinical assessment comprised of: pain on visual analog scale (VAS), Harris Hip Score (HSS), and Postel Merle-d'Aubigne score (PMA). The rate of surgical complications (periprosthetic fracture, infection, non-union, dislocation) was assessed and the primary fixation quality was analysed for fracture complexity and conformity to standards. Results: At a mean 54 months' follow-up [range, 24-122 months], the post-THA complications rate was 22% (9/40), although with no cases of implant dislocation. Pre- to postoperative comparison found significant improvements on VAS (7.9 +/- 1.6 versus 1.35 +/- 1.5, respectively), HHS (20 +/- 11.8 versus 78 +/- 12.3) and PMA (4.7 +/- 2.9 versus 14.6 +/- 2.1) (p < 0.0001), but non-significant change in Parker-Palmer score (5.5 +/- 2 and 4.8 +/- 1.9) (p = 0.4). Fracture instability rate was 77% and 85% (31 and 34/40) on the AO and Evans-Jensen classifications respectively. Analysis of primary fixation found non-conformity with reduction standards in 68% of cases (27/40): most frequently, cervical screw centering defect (58%, 23/40) and reduction defect (28%, 11/40). The non-conformity rate was 44% (4/9) in AO stable fracture and 74% (23/31) in unstable fracture. Conclusion: The study hypothesis was confirmed, with no dislocations in this high-risk population. This can be attributed to exclusive use of DM cups, which should be systematic in high-risk contexts. The study confirmed the importance of primary fixation quality, although a risk of failure remains, even in stable fractures. (C) 2020 Elsevier Masson SAS. All rights reserved.