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'Aubigné 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.

LEVEL OF EVIDENCE

IV, retrospective study.