Increase in spinal canal area after inverse laminoplasty - An anatomical study

Study Design. in vitro measurement of the area of the spinal canal in the r ostral and caudal portions of lumbar vertebrae before and after application of a new technique called "inverse laminoplasty." Objectives. To quantify the normal area of the spinal canal in the rostral and caudal portions of lumbar vertebrate End the amount of enlargement gain ed after inverse laminoplasty. Summary and Background Data. Other types of laminoplasty have been proven t o increase the area of the I spinal canal. Inverse laminoplasty has been pe rformed in 10 patients but has not been evaluated in vitro. Methods. The transverse and anteroposterior diameter of the spinal canal wa s measured in 34 vertebrae from seven cadavers using digital calipers. In e ach vertebra. the laminae and spinous process were removed en bloc using a high-speed drill. The removed piece was inverted and reattached with titani um mini-plates. The area of the spinal canal was again measured and compare d with the prelaminoplasty measurements using paired Student's t tests. Results. The anteroposterior diameter and area of the spinal canal were sig nificantly 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 can al increased by 61% and 17%, respectively, after the laminae were inverted (P < 10(-3)). Conclusion. Because inverse laminoplasty is simple and increases the area o f the spinal canal, it may prove to be a useful surgical technique for the treatment of lumbar spinal stenosis. Further studies are needed to determin e whether the technique is biomechanically sound and whether it helps preve nt perineural scarring.