Subtrochanteric femoral fractures and intramedullary nailing complications: a comparison of two implants.

Introduction: Intramedullary (IM) nails are considered the 'gold' standard treatment for subtrochanteric femoral fractures. The incidence and risk factors for re-operation in subtrochanteric fractures remain unclear. Furthermore, no studies have compared the outcomes of different nailing systems used to treat subtrochanteric fractures in the same study population.

Aims/objectives: Our study aimed to (i) investigate the cumulative incidence and factors associated with an increased risk of re-operation in subtrochanteric fractures treated with a long intramedullary (IM) nail, (ii) compare the outcomes of subtrochanteric fractures treated with long Affixus and Gamma nails, and (iii) establish whether the addition of a proximal anti-rotation screw in the Affixus nail confers any clinical benefit.

Methods: A retrospective review of all adult patients admitted to a level 1 trauma centre with a subtrochanteric femur fracture treated with a long cephalomedullary IM nail over an 8-year period was conducted. Exclusion criteria were primary surgery performed at another institution, prophylactic nailing because of tumours, incomplete fractures, and patients who were lost to follow-up or died before fracture healing. Data variables were assessed for normality prior to determining the use of either parametric or non-parametric tests. Logistic regression analysis was performed to identify potential factors associated with re-operation. For the comparison between the two nail types, patients were matched into two groups of 119 each by age (10-year intervals), gender and mechanism of injury (low energy, high energy and pathological fractures). A p-value < 0.05 was considered significant. The Kaplan-Meier nail survival curve was used to demonstrate the survival of each nail. Data were analysed using the statistical package R (R version 3.6.0).

Results: A total of 309 subtrochanteric fractures were treated with a distally locked long IM nail (re-operation rate: 22.33%) over an 8-year period. Logistic regression identified six factors associated with an increased risk of re-operation, including age < 75 years old, use of a long Gamma nail, pre-injury coxa-vara femoral neck shaft angles, an immediate post-operative reduction angle of > 10° varus, deep wound infection and non-union. Following matching, we compared the two long cephalomedullary nailing systems used (Gamma versus Affixus nail). The only differences identified from the unadjusted analysis were a higher overall incidence of nail failure in Gamma nails due to any cause, re-operation, and impingement of the nail tip distally against the anterior femoral cortex. When we corrected for covariates, no significant differences remained evident between the two nails. From the Kaplan-Meier nail survival curves, however, the Affixus nail demonstrated better survivorship up to 5 years post-implantation in terms of nail failure and re-operation for all causes. Finally, the addition of a proximal anti-rotation screw in the Affixus nail did not seem to confer any benefit.

Conclusion: We reported a 22.3% re-operation rate in our cohort of subtrochanteric fractures treated with a long IM nail. We have identified six risk factors associated with re-operation: age < 75 years old, pre-injury femoral neck shaft angle, choice of nail, varus reduction angle, fracture-related infection and non-union. The addition of a proximal anti-rotation screw in the Affixus nail did not confer any benefit.