Fit-and-Fill Analysis of Different Intramedullary Nails for the Proximal Femur A Numerical Simulation

Abstract

Background: The aim of this study was to evaluate the theoretical possibility of introducing the Trochanteric nail (Howmedica) into an undamaged proximal femur and to compare the results to those obtained with the Gamma nail (Howmedica) and the Proximal Femorel Nail (Stratec).

Material and Methods: A specific computerized program allowed virtual insertion of the various nails into three-dimensional reconstructions of the femur. This program, based on the 3-D study in computerized tomography by Hussmann et al, evaluated the nailbone superpositions of various geometries and calculated the bone volume to be removed for optimal insertion of the nail. Reaming was estimated according to surgical rules, thus considering carefully the antetorsion of the femoral neck and the antecurvation of the femur.

Results: Among 50 femurs, the smallest bone quantity to be removed was found using the Trochanteric nail; with the Gamma nail this quantity doubled, the results obtained with the Proximal Femoral Nail ranging in between. These results must be very cautiously analyzed, due to significant standard deviations. They will, however, awaken the surgeon's consciousness of the subject.

Conclusions: The most difficult situation of nail insertion is the small unbroken trumpet-shaped femur with a small cervicodiaphyseal angle. A properly reduced fracture slightly facilitates introduction of the nail, complemented by preparatory reaming of the femur.