Biomechanical Study of Cervical Posterior Decompression

STUDY DESIGN: Biomechanical study. PURPOSE: We examined the dynamic characteristics of different operative procedures using three-dimensional finite-element models. OVERVIEW OF LITERATURE: Cervical laminoplasty is often selected for patients requiring multilevel spinal decompression. Many laminoplasty techniques have been developed and are continually being improved. METHODS: Images were extracted for the two intervertebral joints between C3 and C5 in domestic rabbits. The following models were created: preoperative, laminectomy, Z-plasty, open door laminoplasty, French open door laminoplasty, en-bloc laminoplasty, and double-door laminoplasty. The loads required for sagittal rotation of 2.5°, 5°, and 7.5° were measured in vitro and respectively placed at the bottom of the C5 model. Displacement of the plate in the X, Y, and Z coordinates was measured and the rotational angles of the plate were determined. RESULTS: The sagittal rotation angle was greater in the laminectomy model than in the preoperative model, but was almost the same in the preoperative and Z-plasty models. Compared with the preoperative model, sagittal rotation angles were smaller in the French open door, open door, en-bloc, and double-door laminoplasty models. CONCLUSIONS: Laminectomy and various types of laminoplasty are associated with different mechanical features, such as stability and mobility, allowing for selection of the most appropriate surgical procedure for each case.