Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord.

STUDY DESIGN

A study to measure the shifts of the spinal cords and the effects of decompression laminoplasty in 65 patients with cervical lesions who underwent computed tomographic myelography before and after laminoplasty.

OBJECTIVES

To investigate limitations of the spinal cord posterior shift after laminoplasty and to clarify the optimal decompression areas to obtain effective posterior shifting.

SUMMARY OF BACKGROUND

Although several types of laminoplasty have been performed, all procedures share the common purpose of posterior decompression. No previous studies have examined the limitations of posterior decompression or the optimal decompression range.

METHODS

The distance from the posterior edge of each vertebral body or disc level to the posterior edge of the spinal cord was measured by computed tomographic myelography. After the posterior shift was determined by calculating the difference between pre- and postsurgical distances, the relations between posterior shift and neck alignment, clinical results, and the areas of decompression were analyzed.

RESULTS

The spinal cord shift ranged from a maximum of 6.6 mm to a minimum of 0 mm. Clinically, spinal cord shifts greater than 3 mm were associated with good clinical outcomes. Upward or downward advanced laminoplasty was related to larger spinal cord shifts at the upper or lower cervical spine.

CONCLUSIONS

A mean spinal cord shift of > 3 mm was associated with good clinical outcomes after laminoplasty. In cases with compressive lesions at the upper or lower cervical spine, extension of decompression one level above or one level below likely results in a greater posterior spinal cord shift at these lesions.