A biomechanical study comparing proximal femur nail and proximal femur locking compression plate in fixation of reverse oblique proximal femur fractures

Abstract

Background: The reverse oblique trochanteric fractures are common fractures and its treatment poses a challenge. The purpose of this study was to compare the biomechanical parameters of the construct using proximal femoral nail (PFN) and proximal femoral locking compression plates (PFLCP) in these fractures using cadaveric specimens.

Materials and methods: Twenty freshly harvested cadaveric femoral specimens were randomly assigned to two groups after measuring bone mineral density, ten of which were implanted with PFN and the other ten with PFLCP. The constructs were made unstable to simulate reverse oblique trochanteric fracture (AO type 31A3.3) by removing a standard size posteromedial wedge. These constructs were tested in a computer controlled cyclic compressive loading with 200kg at a frequency of 1 cycle/s (1Hz) and test was observed for 50,000 cycles or until implant failure, whichever occurred earlier. Peak displacements were measured and analysis was done to determine axial stiffness and subsidence in axial loading.

Results: All the specimens in PFN group completed 50,000 cycles and in PFLCP group, seven specimens completed 50,000 cycles. Average subsidence in PFN group was 1.24±0.22mm and in PFLCP group was 1.48±0.38mm. The average stiffness of PFN group (72.6±6.8N/mm) was significantly higher than of PFLCP group (62.4±4.9N/mm) (P=0.04). The average number of cycles sustained by PFLCP was 46634 and for PFN group was 50,000 (P=0.06).

Conclusion: The PFN is biomechanically superior to PFLCP in terms of axial stiffness, subsidence and number of specimens failed for the fixation of reverse oblique trochanteric fractures of femur.

Keywords: Dual energy X-ray absorptiometry; Gap-osteotomy; Proximal femoral locking compression plates; Proximal femoral nail; Reverse oblique; Trochanteric fractures; Unstable.