Stability of the C2-C3/C3-4 Level during C4-C6 Laminoplasty With and Without C3 Laminectomy in Cadaveric Biomechanical Models

Introduction: Cervical spondylotic myelopathy (CSM) is a progressive disorder that reduces quality-of-life and functional-ability. C3 laminectomy as part of a cervical laminoplasty may improve decompression and reduce postoperative morbidity, such as pain. Despite the benefit, complete laminectomy may result in instability. We performed an analysis of cadaveric spines to determine the effects of C3 laminectomy on C2-C3 stability and range of motion (ROM) during C4-C6 laminoplasty.

Methods: Eight human-cadaveric spines (C1-T2) were mounted to a six degree-of-freedom robotic-testing system (simVITRO®) and underwent preconditioning with pure-moment loading of ±1.5Nm in flexion/extension (FE), axial-rotation (AR), and lateral-bending (LB) to minimize viscoelastic effects. For testing, a 30N head-compressive force was maintained as a head-load while ±1.5Nm moments were applied to the native spine in FE, LB, AR, and in the coupled directions of flexion with axial rotation (FE±AR) and extension with axial rotation (E±AR). Total Spine, C2-C3, and C3-C4 ROM was collected during each applied moment test. Left-sided open-door laminoplasties were then performed at C4, C5, and C6 (Stryker). The specimens were tested again with the above approach. A complete C3 laminectomy was then performed; testing was repeated.

Results: At C2-C3, there were statistically-significant differences in ROM during left-axial rotation (p=0.030) and combined A-flexion and left-axial rotation (p=0.009) between surgical states. At C3-C4, there were statistically-significant differences in ROM during right-axial rotation (p=0.007), overall flexion (p < 0.001), combined A-flexion and right-axial rotation (p=0.011), and combined F-flexion and right-axial rotation (p=0.042). On quaternion difference analysis, at C2-C3, there were no statistically-significant differences in ROM between the two conditions. At C3-C4, ROM in overall flexion (p < 0.001), combined flexion and left-axial rotation (p=0.016), combined flexion and right-axial rotation (p=0.021), and right lateral-bending (p=0.011) were significant.

Conclusion : Augmenting standard C4-C6 laminoplasty with C3 laminectomy significantly alters the biomechanics at C3-4. Further studies are necessary to determine the clinical correlations of these findings.