Geriatric femur fractures: Index fracture pattern is associated with the risk of subsequent peri-implant fracture.

INTRODUCTION

Following an index femoral fragility fracture, patients are at risk of a subsequent peri-implant fracture. Management of these injuries are further complicated by patient factors and multi-institutional care. This study quantifies such events and compare rate of identification between in-system and out-of-system patients.

METHODS

A retrospective chart review of index operative femoral fragility fractures at a level I trauma center from January 1, 2005 to January 1, 2018 identified 840 patients with twenty-two subsequent peri-implant fractures. Kaplan Meier survival analyses assessed associations between patient and injury characteristics with the subsequent fracture while accounting for differential follow-up. Cumulative incidence curves were reported, and Cox regression analyses estimated hazard ratios for statistically significant associations. In-system and out-of-system patients were compared with absolute rate of identifying subsequent fracture and follow-up time.

RESULTS

Cumulative incidence of subsequent fracture was 2.1 % at 2 years, 3.4 % at 4 years, and 4.6 % at 6 years. The index fracture pattern (intertrochanteric vs other) was associated with a cumulative incidence of subsequent peri-implant fracture (0.8 % at 2 years, 1.4 % at 4 years, and 2.7 % at 6 years for intertrochanteric fractures vs 3.4 % at 2 years, 5.3 % at 4 years, and 6.4 % at 6 years for non-intertrochanteric fractures), p = 0.029. Follow-up was shorter for out-of-system patients (median 6 versus 28 months, p < 0.001), and only 1 of 348 out-of-system patients (0.3 %) vs. 21 of 492 in-system patients (4.3 %) were diagnosed with a subsequent peri-implant fracture (p < 0.001). There was no association of subsequent peri-implant fracture with patient demographics or comorbidity burden.

CONCLUSION

Cumulative incidence of subsequent peri-implant fracture was higher for non-intertrochanteric (femoral neck, shaft and distal femur) fractures than intertrochanteric fractures. Out-of-system patients had shorter follow-up and were less likely to be diagnosed with a subsequent peri-implant fracture, indicating ascertainment bias and underscoring the importance of accounting for loss to follow-up.

LEVEL OF EVIDENCE

Therapeutic Level III.