Increase in Spinal Canal Area After Inverse Laminoplasty

Abstract

In vitro measurement of the area of the spinal canal in the rostral and caudal portions of lumbar vertebrae before and after application of a new technique called "inverse laminoplasty." To quantify the normal area of the spinal canal in the rostral and caudal portions of lumbar vertebrae and the amount of enlargement gained after inverse laminoplasty. Other types of laminoplasty have been proven to increase the area of the spinal canal. Inverse laminoplasty has been performed in 10 patients but has not been evaluated in vitro. The transverse and anteroposterior diameter of the spinal canal was measured in 34 vertebrae from seven cadavers using digital calipers. In each vertebra, the laminae and spinous process were removed en bloc using a high-speed drill. The removed piece was inverted and reattached with titanium mini-plates. The area of the spinal canal was again measured and compared with the prelaminoplasty measurements using paired Student's t tests. The anteroposterior diameter and area of the spinal canal were significantly smaller before surgery in the rostral than in the caudal part of the vertebrae (P <10(-3)). The rostral and caudal areas of the spinal canal increased by 61% and 17%, respectively, after the laminae were inverted (P <10(-3)). Because inverse laminoplasty is simple and increases the area of the spinal canal, it may prove to be a useful surgical technique for the treatment of lumbar spinal stenosis. Further studies are needed to determine whether the technique is biomechanically sound and whether it helps prevent perineural scarring.