3:56 Axial harness loads of the cervical spine in supine posture simulates the upright loads

Abstract

Purpose of study: Patients with cervical degenerative diseases often have pain or tingling in their upper extremities in upright posture. However, computed tomography or magnetic resonance imaging (MRI) is typically performed in a supine position. We reported that axial loading of 50% body weight in the lumbar spine stimulates upright loading conditions [1]. The aim of our study was to simulate upright cervical spine loads using a new compression device and to examine the change of cervical spine alignment and dural tube before and during axial compression in healthy volunteers and in patients with cervical degenerative diseases.Methods used: Eighteen healthy volunteers (9 men, 9 women) with a mean age of 44 years and 12 symptomatic patients with cervical degenerative diseases with a mean age of 53 years participated in this study. Axial compression was applied between the head and the feet, in supine posture using a MRI-compatible compression device. The compression force between the helmet and the footplate was determined with four calibrated scales, one on each of the interconnecting straps. To determine how much axial compression force is required to simulate the upright cervical spine, the lordosis angle between C2 and C6 in a lateral plain radiograph in upright posture was compared with supine posture radiographs with axial loads of 0%, 7%, 10% and 13% of the subject's body weight. To study morphological changes of the dural tube before and during axial compression both in healthy volunteers and symptomatic patients, T2-weighted axial MRI was done using a 1.5T system. The axial images were angled parallel with each disc level of C2–C3 to C7–T1. The following parameters were measured on the dural tube: anterior posterior distance (AP, mm) and cross-sectional area (CSA, mm2).of findings: The lordosis angle of the cervical spine in upright posture between C2 and C6 was 13.4 ± 2.4 degrees (mean ± SEM) in healthy volunteers. The lordosis angle in supine posture with a load of 0%, 7%, 10% and 13% of the subject's body weight relative to upright posture was −8.1 ± 1.3, −2.3 ± 1.4, 1.3 ± 1.9 and 2.8 ± 2.0 degrees, respectively. Subsequent axial force is interpolated as 8.9% of body weight to simulate the upright cervical spine. A total of 8.5% of body weight was applied to simulate the normal load experienced by the cervical spine in upright posture. There was a significant difference in healthy volunteers before and during compression regarding AP of the dural tube at C5–C6 (11.1 ± 0.4; 10.6 ± 0.4 mm). In symptomatic patients, there was a significant difference regarding AP (9.2 ± 0.4; 8.8 ± 0.3 mm), CSA (142.1 ± 8.4; 136.1 ± 8.1 mm2) of the dural tube at C6–C7.Relationship between findings and existing knowledge: A previous cadaver study has demonstrated that the weight of the head plus neck is approximately 8.4% of body weight [2]. Similarly, our results indicated that 8.9% of body weight was required to simulate the upright cervical spine. In the lumbar spine, Willen and coworker have demonstrated that axial compression of the lumbar spine narrowed the lumbar dural tube in lumbar patients [3]. Our data documented that axial compression decreased the AP diameter of the dural tube at C5–C6 in healthy volunteers, and the AP distance as well as the CSA of the dural tube at C6–C7 decreased significantly during axial compression in patients with cervical degenerative diseases.Overall significance of findings: The present results provide more understanding of the pathophysiology of cervical compression myelopathy in upright posture.Disclosures: No disclosures.Conflict of interest: Shinji Kimura, grant research support, DynaWell Inc., Sweden.