Comparing the rates and modes of failure of two third generation cephalomedullary nail systems in the treatment of intertrochanteric hip fractures

Abstract

Introduction: Cephalomedullary (CMN) implants are commonly used to address elderly intertrochanteric hip fractures. Multiple CMN implant systems exist with subtle variation between manufacturers. Multiple modes of CMN failure have been described in the literature. The present study assessed the local modes and rates of construct failure (nail fracture, cut-out and non-union) of two such implants, after a change in implant supply provided the opportunity for retrospective comparison. Additional investigation was undertaken to assess whether any predictors of failure could be identified based on common radiographic measurement parameters.

Methods: Based on local implant records, all consecutive patients who suffered an intertrochanteric fracture, treated at a tertiary care hospital with a cephalomedullary nail from January 2014 to January 2018 were included. Patients were excluded if they received a CMN for pathologic fracture. Within the collection period all patients received either a Synthes Trochanteric Fixation Nail (TFN) or Zimmer Natural Nail (ZNN). Patients were retrospectively assessed for fracture reduction and implant technique parameters at the time of initial surgery. Radiographic data were assessed at minimum two years post-operatively to assess for union. Patient demographic data was followed to assess rate and mode of failure.

Results: Six hundred and sixty-two patients were included in the study, from which a propensity matched cohort was derived. Comparing across equivalent cohorts, no differences in the rate or mode of construct failure were identified between the TFN and ZNN. When assessing the entire cohort we observed 39 construct failures (5.9%), which included 31 instances of nail cutout (4.7%), 4 episodes of nail fracture (0.6%) and 4 failures related to non-union (0.6%). Tip to apex distance, sagittal malalignment and Cleveland zone were identified as significant predictors of nail failure.

Conclusion: No difference in rates or modes of failure were identified between the TFN and ZNN constructs. Similar to previous reports we again identified the impact of tip to apex distance on construct failure and further identified Cleveland zone and sagittal malalignment as significant risks for failure.

Keywords: Cephalomedullary nail; Hip fracture; Intertrochanteric fracture.