Biomechanical comparison of an orthogonal and parallel angle-stable interlocking nail in axial compression on a gap fracture model

Author(s)

Gislane Vasconcelos de Souza

• Document type: Master's Dissertation
• Press: Jaboticabal. 2022-09-05.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2022-05-05
• Advisor: Luís Gustavo Gosuen Gonçalves Dias

Abstract

The objective is to evaluate the orthogonal locking in interlocking nails, with and without angular stability, compared to the parallel locking system, through axial compression tests. For this purpose, prototyped specimens with critical failure (20 mm) were used, simulating diaphyseal comminution. The nails were made with 175 mm in length and 8 mm in diameter, and divided into four groups (seven units each). Group 1 (G1) was composed of intramedullary nails with two holes in the proximal segment and two in the distal segment, all threaded, to promote locking of the screws with the nail (stable angle) and with the cortical bones of the specimens; in this model, the implant holes were arranged in the same plane. In group 2 (G2), the same locking system as in G1 was used, but with an orthogonal disposition of the blocking holes. In group 3 (G3), the locking system was formed by specific bolts made for coupling with the nail holes without threading (no stable angle), with a solid and smooth body, and proximal end with threads for interaction with the cis cortical of the specimen. In this group the locking holes of the nail were arranged in a parallel way. In group 4 (G4), the locking mechanism was the same as in G3, but with orthogonally arranged. The means will be compared with Student's t test with a significance level of 5%. Group 2 obtained the highest absolute value of stiffness (4573.14 N/mm), but with no statistical difference regarding the mean between the other groups for this variable. Group 4, despite having sustained the lowest maximum force (16984.07 N) among the groups evaluated, was the group that deformed the least (average 8.74 mm). Thus, orthogonal locking presents mechanical similarity in destructive axial compression tests and may represent excellent alternatives to nails with parallel locking, especially when the fracture configuration limits its use, allowing the fixation of two screws even in the presence of limited bone stock. However, clinical studies are needed to evaluate the behavior of such implants in the biological environment. (AU)

• FAPESP's process: 20/06223-5 - Comparative analysis of different intramedullary locking nails configurations submitted to axial compression
• Grantee: Gislane Vasconcelos de Souza
• Support Opportunities: Scholarships in Brazil - Master