Effect of multilevel open-door laminoplasty and laminectomy on flexibility of the cervical spine: an experimental investigation

STUDY DESIGN.: A biomechanical comparison of 2 commonly used posterior surgical procedures for spinal cord decompression in the cervical spine: laminoplasty (open door) and laminectomy. OBJECTIVE.: To delineate differences in cervical motion after laminoplasty (2-level and multilevel) and laminectomy. SUMMARY OF BACKGROUND DATA.: Cervical spondylotic myelopathy is a common spinal cord disorder in persons aged 55 years or older. Laminectomy and laminoplasty are the 2 common posterior-based techniques used for decompression of spinal cord. There is lack of adequate literature data on the intersegmental rotations at the operated and adjacent levels. METHODS.: Five human cadaveric specimens were tested sequentially as follows: (1) intact, (2) laminoplasty at C5-C6, (3) laminoplasty at C3-C6, and (4) laminectomy at C3-C6, each subjected to 2 N·m moments in flexion/extension, right/left lateral bending, and right/left axial rotation. For laminoplasty, the laminae of the involved vertebrae were stabilized with standard 10-mm plates and screws. The total and segmental motions of the specimens were measured before and after the surgical procedures. Statistical analysis was performed using repeated measures analysis of variance, with P < 0.05 as the level of significance. RESULTS.: Two-level laminoplasty led to minimal decrease (<7% in the 3 loading modes) in C2-T1 motion. Multilevel laminoplasty resulted in a minimal increase during lateral bending (4%) and axial rotation (6%). During flexion/extension, both C4-C5 and C2-C3 showed a decrease of 20% (P > 0.05) and 17% (P > 0.05) after 2-level and multilevel laminoplasty, respectively. Laminectomy resulted in a statistically significant (P < 0.05) increase in the C2-T1 range of motion compared with the intact condition during the 3 loading modes (21% in flexion/extension, 8% in lateral bending, and 15% in axial rotation). CONCLUSION.: Both 2-level and multilevel laminoplasty preserved the C2-T1 range of motion. Laminectomy resulted in a significant increase in C2-T1 motion due to the loss of the posterior structures.