A pilot evaluation of the efficiency of cast and cervical rigid orthosis in the immobilization of Jefferson fractures via finite element analysis

Various orthoses are used to immobilize fractures of the first cervical vertebra (C1). However, it is not well determined which design of braces better immobilizes the C1 fracture. Therefore, this study aimed to determine the effectiveness of a cast and cervical orthosis in immobilizing C1 fractures. The motion of the cervical spine and the force of cervical muscles in flexion, extension, lateral bending, and rotation were determined in a normal subject using a motion analysis system and OpenSIM software. CT scan images of a normal subject were used to create a 3D model of the cervical spine in normal and fractured conditions. The efficiency of a cast and cervical orthosis (Philadelphia collar) in restricting rotatory and translatory motions of the cervical spine was determined using Abaqus software for both the upper and lower parts of the cervical spine. In normal condition, the range of flexion, extension, lateral bending, and rotation of the upper cervical spine was 13, 3, 7, and 7.1 degrees, respectively. The range of flexion increased to 38 degrees in fracture condition, while extension and lateral bending increased by 29 and 10 degrees, respectively. Although both the cast and orthosis limited the motion of the upper cervical spine, the cast was found to be more effective than a cervical collar. Based on the results of this study, rotational and translational motions of C1 vertebrae significantly increased in Jefferson fractures. Therefore, appropriate immobilization is necessary in this regard. While both a cast and collar effectively control the motion of C1, the cast appears to be more efficient than an orthosis.