Biomechanical Consequences of Nail Insertion Point and Anterior Cortical Perforation for Antegrade Femoral Nailing.

Michael Ching,Christopher Del Balso,Aaron Gee,Radovan Zdero,Abdel Lawendy,Emil H Schemitsch,David Sanders,Thaqif El Khassawna

doi:10.1155/2020/5878607

Michael Ching, Christopher Del Balso + Show 6 more

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https://doi.org/10.1155/2020/5878607

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Abstract

This biomechanical study assessed the influence of changing antegrade cephalomedullary nail insertion point from anterior to neutral to posterior locations relative to the tip of the greater trochanter with or without anterior cortical perforation in the distal femur. Artificial osteoporotic femurs and cephalomedullary nails were used to create 5 test groups each with 8 specimens: intact femur without a nail or perforation, anterior nail insertion point without perforation, neutral nail insertion point without perforation, posterior nail insertion point without perforation, and posterior nail insertion point with perforation. Nondestructive biomechanical tests were done at 250 N in axial, coronal 3-point bending, sagittal 3-point bending, and torsional loading in order to measure overall stiffness and bone stress. The intact femur group vs. all femur/nail groups had lower stiffness in all loading modes (p ≤ 0.018), as well as higher bone stress in the proximal femur (p ≤ 0.027) but not in the distal femur above the perforation (p = 0.096). Compared to each other, femur/nail groups only showed differences in sagittal 3-point bending stiffness for anterior and neutral vs. posterior nail insertion points without (p ≤ 0.025) and with perforation (p ≤ 0.047). Although it did not achieve statistical significance (p ≥ 0.096), moving the nail insertion point from anterior to neutral to posterior to posterior with perforation did gradually increase bone stress by 45% (proximal femur) and 46% (distal femur). No femur or hardware failures occurred. Moving the nail insertion point and the presence of a perforation had little effect on stiffness, but the increased bone stress may be important as a predictor of fracture. Based on current bone stress results, surgeons should use anterior or neutral nail insertion points to reduce the risk of anterior cortical perforation.

Highlights

Hip fractures are a common problem in the elderly because of the increased prevalence of osteoporosis in this population
This study assessed the biomechanical effect of nail insertion point and anterior cortical perforation in the distal femur for antegrade femoral nailing in a postunion, rather than a postoperative, scenario
The INT group was less stiff than NEU, POS, and POS-P nail groups (0:002 ≤ p ≤ 0:016), but it was trending towards being less stiff than the ANT nail group (p = 0:052); there were no differences in stiffness between any nail groups (0:759 ≤ p ≤ 0:999)

Summary

Introduction

Hip fractures are a common problem in the elderly because of the increased prevalence of osteoporosis in this population. The proportion of hip fractures that involve the trochanteric region rises with age from 35% (55-59 years old) to 51% (84 years old and above) [1]. In men, the proportion of hip fractures that involve the trochanteric region slightly decreases with age from 47% (55-59 years old) to 44% (84 years old and above) [1]. Women are 2.5 times as likely as men to experience a hip fracture [2]. 90% of hip fractures occur in patients over 70 years of age, most of which occur due to a fall from a standing height; the force from such a fall exceeds the femoral strength of an older individual by about 50% [3]. The mortality rate of fractures associated with osteoporosis ranges from 15 to 30%, while 50% of osteoporotic women with hip fractures develop disability, which may lead to institutionalization [4]

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