Cervical myelopathy is a common cause of neurological disability among the elderly; however, the exact mechanism for the insidious and progressive deterioration remains to be elucidated. To study the pathophysiology, we developed a simple experimental model reproducing the course. In rats, a thin sheet of expanding polymer was implanted microsurgically underneath the C5-C6 laminae. In the control group, the polymer sheet was removed immediately. Changes in motor functions were monitored for 25 weeks after the operation, with voluntary exercise activity measured by odometer attached to revolving cages, and forced running capability measured by duration of exercise on a rotating treadmill. Motor neurons were counted stereologically in continuous sections. In the compression group, the forced running capability deteriorated after a latent period of 17 weeks and progressively thereafter. In the control group, it stayed unchanged throughout 25 weeks. Course of the voluntary exercise was comparable between the groups. Motor neuron density in the compression group decreased significantly in 9 weeks (-20.3%) and 25 weeks (-35.5%), but not in 1 or 3 weeks. This practical model properly reproduces characteristic features of the clinical cervical myelopathy, with progressive motor disturbance after a latency and insidious neuronal loss preceding the symptoms.

Cervical laminoplasty was developed as an alternative to cervical laminectomy for treatment of cervical myelopathy, in which hinges are created to lift the lamina. Various techniques of laminoplasty have since been developed after two prototype techniques: Hirabayashi’s open-door laminoplasty and Kurokawa’s spinous process splitting (double-door) laminoplasty. Several in vitro studies report superior biomechanical stability of the cervical spine after laminoplasty compared with laminectomy. In clinical situation, randomized control studies are scarce and superiority of one procedure over another is not uniformly shown. Lack of hard evidence supporting the purported advantages of laminoplasty over laminectomy, that is, reduced rate of postoperative instability and kyphosis development, while preserving range of motion (ROM), has been a weak selling point. Currently, laminoplasty is performed by majority of spine surgeons in Japan, but is rarely performed in the United States and Europe. Recent development in laminoplasty is preservation of muscle attachment, which enabled dynamic stabilization of the cervical spine by neck extensor muscles. After treatment with new laminoplasty techniques with active postoperative neck ROM exercises, postoperative instability, kyphosis, axial neck pain, and loss of ROM seems minimal. Well-designed clinical trials to show the effectiveness and long-term outcome of this surgical procedure are warranted.

Object Laminoplasty has been used to expand the cervical spinal canal, based on the belief that reconstruction of the laminae preserves musculoskeletal function. The true efficacy of laminoplasty for maintaining spinal alignment, stability, and flexibility, however, remains to be proven. The authors have developed a new method, myoarchitectonic spinolaminoplasty (MSLP), which preserves all of the nuchal muscles and reconstitutes all of the musculoskeletal couplings to the posterior elements of the vertebrae. The details of this technique are described, and the efficacy of the technique in conserving muscle volume, alignment, and motion, as well as in preventing postoperative musculoskeletal discomfort, is assessed. Methods The authors' previous midline-splitting laminoplasty procedure, which utilized a hydroxyapatite (HA) implant as a substitute for the spinous process, was improved. Detachment of the muscles is avoided with this new technique by cutting inside the spinous process. The bone–muscle flaps are affixed to the HA spinous process. Radiographs, computed tomography scans, and neurological evaluations obtained at the 1-year follow-up in the groups of consecutive patients assessed immediately prior to and after the modification of the previous technique (the control and the MSLP groups, respectively) were analyzed and compared. Results The HA bone constructs became integrated due to osteoconduction. The cross-sectional area of the semispinalis capitis, semispinalis cervicis, and multifidus muscles remained significantly larger in the MSLP group. Slight attenuation in lordosis was observed in the control group, but was prevented in the MSLP group. Range of motion was somewhat restricted in the MSLP group, but the incidence of neck pain and shoulder strain was significantly reduced. Conclusions The new MSLP method was effective in preserving the volume and functions of the nuchal musculature and helping to minimize postoperative musculoskeletal complaints.

Under chronic focal spinal cord compression, there was a decrease of the blood flow in the compressed segment in comparison to the rostral segment. Our data are compatible with the hypothesis that alteration in the spinal cord blood flow contributes to pathogenesis of myelopathy.

The authors conclude that satisfactory interbody fusion can be achieved by using HA implants, provided their design is appropriate and adequate surgical techniques are used.