The Role of Distraction in Improving the Space Available for the Cord in Cervical Spondylosis

Abstract

This study analyzed the effects of distraction via strut graft insertion on the canal dimensions in spondylotic human cadaver cervical spines. Transverse and anteroposterior diameters and cross-sectional areas were measured by transverse computed tomography imaging before and after distraction without direct decompression. This experiment was designed to address whether distraction across the disc space without direct canal decompression can improve the space available for the cord. Smith-Robinson anterior discectomy and fusion have been shown to improve clinical symptoms of radiculopathy and myelopathy even in the absence of direct decompression. This has been postulated to be the result of gradual resorption of intruding osteophytes. However, the immediate effects of indirect distraction alone have not been previously investigated. Four cadaver spines from elderly donors were harvested intact. The transverse diameter, anteroposterior diameter, and cross-sectional area of the spinal canal were measured before and after discectomy and distraction via insertion of fibular strut graft by digitization of contiguous computed tomography scan slices. The spinal canal dimensions before distraction were found to vary in a sinusoidal pattern around the disc space, with the maximum measurements located at the pedicle and the minimum measurements at the spondylotic ridge above or below the disc space. Distraction via strut graft insertion significantly increased the anteroposterior diameter and cross-sectional area, but had a negligible effect on transverse diameter. Anterior discectomy and distraction with a strut graft can significantly improve the space available for the cord in cervical spondylosis. Osteophyte debridement, which risks iatrogenic injury to the cord, may not always be necessary for improving clinical radiculopathy and myelopathy.