Richard C Lee, Steven D Voinier, Sennay G Ghenbot, Cody D Schlaff, Olivia J Staser, Candace J Metcalfe, Scott C Wagner, Donald R Fredericks, Melvin D Helgeson, Alfred J Pisano
Modified laminoplasty does not destabilize the cervical spine in flexion-extension. Modified laminoplasty increases ROM and NZ in axial rotation, although its clinical implication remains unclear. Traditional laminoplasty from C3 to C6 significantly decreases ROM and NZ in flexion-extension.
STUDY DESIGN: Controlled laboratory study.
OBJECTIVE: The purpose of this study is to compare the mechanical stability of modified and traditional laminoplasties in multiple anatomic planes of motion.
SUMMARY OF BACKGROUND DATA: Traditional C3-C6 open-door laminoplasty is associated with postoperative axial pain and decreased range of motion (ROM). Modified laminoplasty with a C3 laminectomy is a promising technique that addresses these shortcomings. However, it is unclear whether this induces instability between C2 and C4.
METHODS: Sixteen cervical spine specimens were tested on a servohydraulic mechanical testing system (MTS) in flexion-extension, lateral bending, and axial rotation. The angular displacements of the total cervical spine (C2-C7) and the C2-C4 were tracked with the MTS and with Optotrak infrared triads. Each spine was tested in both its native state and after the assigned surgical treatment (n=8 traditional and n=8 modified). ROM and neutral zone (NZ) were calculated for each anatomic motion plane.
RESULTS: Compared with the native spine (1.00), traditional laminoplasty had significantly decreased relative flexion-extension ROM (0.86 total C-spine only) and NZ (0.78 total C-spine, 0.72 C2-C4), whereas modified laminoplasty did not (ROM 1.03 total C-spine, 1.10 C2-C4; NZ 1.02 total C-spine, 1.05 C2-C4). Modified laminoplasty had significantly larger relative ROM (1.15 total C-spine, 1.19 C2-C4) and NZ (1.18 total C-spine only) in axial rotation in the total cervical spine, whereas traditional laminoplasty did not (ROM 1.04 total C-spine, 1.02 C2-C4; NZ 1.00 total C-spine, 1.01 C2-C4).
CONCLUSIONS: Modified laminoplasty does not destabilize the cervical spine in flexion-extension. Modified laminoplasty increases ROM and NZ in axial rotation, although its clinical implication remains unclear. Traditional laminoplasty from C3 to C6 significantly decreases ROM and NZ in flexion-extension.