Guang-Ming Xu1, Zi-Yang Liang2, Wei Li1, Zheng-Zhong Yang1, Zhi-Bin Chen1, Jie Zhang1. 1. Department of Orthopaedics, Shenzhen Pingle Orthopedic Hospital & Shenzhen Pingshan Traditional Chinese Medicine Hospital, Shenzhen, China. 2. First Clinical Medical College, Guangzhou University of Chinese Medicine, Guangzhou, China.
Abstract
OBJECTIVE: To investigate the biomechanical effects of different insertion angles of absorbable screws for the fixation of radial head fractures. METHODS: The finite element models used to simulate the fractures were created based on CT scans. Two absorbable screws were used to fix and maintain the stability of the fracture, and the angles between the screws were set to 0°, 15°, 30°, 45°, 60°, 75°, and 90°. A downward force of 100 N was applied at the stress point, which was coupled with the surface, and the distal radius was limited to six degrees of freedom. The direction and location of the applied force were the same in each model. The values of the von Mises stress and peak displacements were calculated. RESULTS: Under the applied load and different screw angles, the maximum von Mises stress in the screws was concentrated on the surface contacting the fracture surfaces. The maximum von Mises equivalent stress in the screw decreased when the angle increased from 0° (19.54 MPa) to 45° (13.11 MPa) and increased when the angle further increased to 90° (24.63 MPa). The peak displacement decreased as the angle increased from 0° (0.19 mm) to 45° (0.15 mm) and increased when the angle further increased to 90° (0.25 mm). CONCLUSION: The computational stress distribution showed that fixation with absorbable screws is safe for patients. Moreover, the minimum von Mises stress and displacements were generated when the angle between the screws was 45°; hence, this setting should be recommended for Mason type II radial fractures.
OBJECTIVE: To investigate the biomechanical effects of different insertion angles of absorbable screws for the fixation of radial head fractures. METHODS: The finite element models used to simulate the fractures were created based on CT scans. Two absorbable screws were used to fix and maintain the stability of the fracture, and the angles between the screws were set to 0°, 15°, 30°, 45°, 60°, 75°, and 90°. A downward force of 100 N was applied at the stress point, which was coupled with the surface, and the distal radius was limited to six degrees of freedom. The direction and location of the applied force were the same in each model. The values of the von Mises stress and peak displacements were calculated. RESULTS: Under the applied load and different screw angles, the maximum von Mises stress in the screws was concentrated on the surface contacting the fracture surfaces. The maximum von Mises equivalent stress in the screw decreased when the angle increased from 0° (19.54 MPa) to 45° (13.11 MPa) and increased when the angle further increased to 90° (24.63 MPa). The peak displacement decreased as the angle increased from 0° (0.19 mm) to 45° (0.15 mm) and increased when the angle further increased to 90° (0.25 mm). CONCLUSION: The computational stress distribution showed that fixation with absorbable screws is safe for patients. Moreover, the minimum von Mises stress and displacements were generated when the angle between the screws was 45°; hence, this setting should be recommended for Mason type II radial fractures.
Authors: Paul R Rebgetz; Luca Daniele; Ian D Underhill; Andreas Öchsner; Fraser J Taylor Journal: J Shoulder Elbow Surg Date: 2019-01-24 Impact factor: 3.019