Prospective randomized study comparing two cephalomedullary nails for elderly intertrochanteric fractures: Zimmer natural nail versus proximal femoral nail antirotation II.

OBJECTIVES: Although both clinical and biomechanical studies suggest that cephalomedullary implants have a mechanical advantage over extramedullary implants, a high rate of complications or implant failure remains in elderly patients with osteoporosis. In an attempt to address some of these challenges, new implants with improved designs named proximal femoral nail antirotation II (PFNA II) and Zimmer natural nail (ZNN) were developed for elderly patients. Although the PFNA II reportedly has good clinical outcomes, it is unclear which implant achieves better safety and efficacy for treating intertrochanteric hip fractures. The primary objective of this prospective, randomized trial involved 353 patients was to evaluate Harris Hip Score (HHS). The secondary objective was to compare results associated with clinical outcome such as operation time, fluoroscopy time, lateral hip pain, walking ability, and reoperation rate as well as the incidence of cut-out by using implant position and fracture reduction quality.

METHODS: 353 patients with an intertrochanteric fracture amenable to either ZNN implant or PFNA II with a mean age of 77.0 years and a mean follow-up period of 12.3 months were included. We analyzed 353 patients with an intertrochanteric fracture treated using a ZNN implant (n=172, group I) or a PFNA II (n=181, group II) between January 2011 and August 2014.

RESULTS: There were no significant inter-group differences in HHS, walking ability, and reoperation rate were observed. However, operation and fluoroscopy time were significantly different between the two groups as well as group I showed a higher incidence of lateral hip pain than group II. In addition, no significant inter-group differences in cut-out rate determined by implant position and fracture reduction quality. We also found that cut-out was associated with lag screw position in the femoral head measured by Tip-apex distance (TAD) but not with reduction quality.

CONCLUSIONS: Although group I had significant longer operation and fluoroscopy time than group II, both implants are useful tools in the treatment of elderly intertrochanteric fractures as well as only TAD, but not Cleveland zone significantly correlated with lag screw cut-out.