Effect of axial dynamisation on time-to-union and mechanical failures in displaced atypical femoral fractures—A multicentre cohort analysis of 223 cases

Abstract

Introduction: Atypical femoral fractures (AFFs) have slow union and high reoperations rates. Axial dynamisation augments fracture opposition and micro-motion, may benefit healing. Methods: A consecutive multi-centre cohort (QEH, QMH, KWH, NDH) of 224 displaced AFFs in 207 patients (mean age 73.2 years, SD 9.5) (10 males) since 2007 fulfilling the ASBMR criteria treated with IM nailing were reviewed. Mean radiological follow-up was 4.02 years. The status of axial dynamisation was classed Dynamic or Static under two conditions (1):”By intention” at initial surgery, (2):”By effect” at latest radiological follow-up. Fracture reduction quality was assessed. Union was considered complete by RUST score >13 criteria. Time-to-event (TTE) analysis was carried out using the segmented Kaplan-Meier method. Results: Mean TTE for union was the same for “by intention” dynamic and static locking in the first 180 days. (176 d vs 176 d, log rank p=0.413) Following the first 180 days, initially dynamised femurs healed significantly faster (422 d vs 528 d, p=0.048). “By effect” dynamisation, with elective removal of distal locking bolts under LA, further yielded significantly faster healing rate after 180 days (418 d vs 548 d, p=0.17). The incidence of revision for mechanical failures are the same for dynamised or statically locked femurs (7 vs 6, χ2 p=0.6, overall 5.72%). Multivariate Cox regression showed that dynamisation “by effect” independently predicted faster union but not fracture reduction quality (OR=0.320, p=0.31). Conclusion: Routine axial dynamisation at primary fixation and elective removal of static locking bolt under enhanced healing of displaced AFFs with no noticeable detrimental effect apart from the additional minor operation.