The biomechanical effects of multilevel posterior foraminotomy and foraminotomy with double-door laminoplasty

The aim of this study is to evaluate the biomechanical effects of multilevel foraminotomy and foraminotomy with double-door laminoplasty compared with foraminotomy with laminectomy. Using fresh human cadaveric specimens (C2-T1), sequential injuries were created in the following order: intact, bilateral foraminotomies (C3-C4, C4-C5, C5-C6), laminoplasty (C3-C6) using hydroxyapatite spacer, removal of the spacers, and laminectomy. Changes in the rotations of each vertebra in each injury status were measured in six loading modes: flexion, extension, right and left lateral bending, and right and left axial rotation. Foraminotomy alone and following laminoplasty showed no significant differences in motion compared with intact except in axial rotation. After removal of the spacers and following laminectomy, the motion increased significantly in flexion and axial rotation. The ranges of initial slack showed similar trends when compared with the results at maximum load. Clinical implications of these observations are presented.