2015 Young Investigator Award Winner

Cervical Nerve Root Displacement and Strain During Upper Limb Neural Tension Testing

Part 2

Role of Foraminal Ligaments in the Cervical Spine

Abstract

Study Design. 

A cross-sectional cadaveric examination of the mechanical effect of foraminal ligaments on cervical nerve root displacement and strain.

Objective. 

To determine the role of foraminal ligaments by examining differences in cervical nerve root displacement and strain during upper limb neural tension testing (ULNTT) before and after selective cutting of foraminal ligaments.

Summary of Background Data. 

Although investigators have determined that lumbar spine foraminal ligaments limit displacement and strain of lumbosacral nerve roots, similar studies have not been conducted to prove that it is true for the cervical region. Because the size, shape, and orientation of cervical spine foraminal ligaments are similar to those in the lumbar spine, it is hypothesized that foraminal ligaments in the cervical spine will function in a similar fashion.

Methods. 

Radiolucent markers were implanted into cervical nerve roots C5–C8 of 9 unembalmed cadavers. Posteroanterior fluoroscopic images were captured at resting and upper limb neural tension testing positioning before and after selective cutting of foraminal ligaments.

Results. 

Selective cutting of foraminal ligaments resulted in significant increases in inferolateral displacement (average, 2.94 mm [ligaments intact]–3.87 mm [ligaments cut], P < 0.05) and strain (average, 9.33% [ligaments intact]–16.31% [ligaments cut], P < 0.03) of cervical nerve roots C5–C8 during upper limb neural tension testing.

Conclusion. 

Foraminal ligaments in the cervical spine limited cervical nerve root displacement and strain during upper limb neural tension testing. Foraminal ligaments seem to have a protective role, reducing displacement and strain to cervical nerve roots during tension events.

Level of Evidence: 2

In Brief

Upper limb neural tension testing on unembalmed cadavers caused displacement and strain of cervical nerve roots C5–C8. Significant increases were found after selective cutting of foraminal ligaments. Foraminal ligaments limited inferolateral displacement and strain of cervical nerve roots C5–C8, and may protect nerve roots from injury during tensile events.