The Effects of Modified Cervical Laminoplasty With C3 Laminectomy on Motion and Stability

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.