Potential of polymethylmethacrylate cement-augmented helical proximal femoral nail antirotation blades to improve implant stability--a biomechanical investigation in human cadaveric femoral heads

Abstract

Background: Cement augmentation may improve fixation stability and reduce cut-out rate in the treatment of intertrochanteric hip fractures. The aim of this study was to compare the number of cycles to failure of polymethylmethacrylate (PMMA)-augmented helical blades with nonaugmented ones in human cadaveric femoral heads.

Methods: Six pairs of cadaveric femoral heads were instrumented with a perforated proximal femoral nail antirotation blade. Within each pair, one blade was augmented using 3 mL of PMMA. All specimens underwent cyclic axial loading under physiologic conditions.Starting at 1,000 N, the load was monotonically increased by 0.1 N/cycle until construct failure occurred. To monitor the migration of the blade, anteroposterior radiographs were taken at 250 cycle increments. Nonparametric test statistics were done to calculate correlations and identify differences between study groups.

Results: Inducing failure required a significantly higher number of cycles in the augmented group (p = 0.028). Bone mineral density was significantly related with the number of cycles to failure in nonaugmented specimens (p 0.001, R2 = 0.97), but not in the augmented group (p = 0.91, R2 = 0.34).

Conclusion: Implant augmentation with small amounts of PMMA enhances the cut-out resistance in proximal femoral fractures. Especially in osteoporotic bone, the procedure may improve patient care.