Object The goal of this study was to perform a biomechanical study of cervical flexion myelopathy (CFM) using a finite element method. Methods A 3D finite element model of the spinal cord was established consisting of gray matter, white matter, and pia mater. After the application of semi-static compression, the model underwent anterior flexion to simulate CFM. The flexion angles used were 5° and 10°, and stress distributions inside the spinal cord were then evaluated. Results Stresses on the spinal cord were very low under semi-static compression but increased after 5° of flexion was applied. Stresses were concentrated in the gray matter, especially the anterior and posterior horns. The stresses became much higher after application of 10° of flexion and were observed in the gray matter, posterior funiculus, and a portion of the lateral funiculus. Conclusions The 5° model was considered to represent the mild type of CFM. This type corresponds to the cases described in the original report by Hirayama and colleagues. The main symptom of this type of CFM is muscle atrophy and weakness caused by the lesion of the anterior horn. The 10° model was considered to represent a severe type of CFM and was associated with lesions in the posterior fand lateral funiculi. This type of CFM corresponds to the more recently reported clinical cases with combined long tract signs and sensory disturbance.

Cervical myelopathy at the C4-5 level is a potential risk for motor dominant C5 paralysis. Although it is merely a speculation, when C5 radiculopathy occurs after laminoplasty, C5 paralysis becomes clinically apparent because the deltoid muscle gets predominantly innervated by C5 root due to intramedullary spinal cord damage on the C6 segment in C4-5 myelopathy before surgery. It may represent the high signal intensity area on T2-weighted MRI at the C4-5 level.

The residual function of motor and sensory nerve roots involved with cervical schwannoma differed between individuals and could be detected using intraoperative electrophysiologic assessment.

Ten patients with cervical spinal schwannomas were operated using a new posterior approach, termed cervical hemilaminoplasty. A thread wire saw (T-saw) was used to cut the lamina at the center of the spinous process and at the unilateral pars interarticularis on the affected side. The unilateral lamina, the inferior articular process, and half of the spinous process were resected as a single mass. After tumor excision, the resected lamina was restored to the original site and fixed. Fusion technique was not required. The mean number of resected and restored lamina was 1.5. No instability of the cervical spine was detected using flexion/extension x-ray photography. Although worsening of radicular motor function was observed in 2 cases, the weakness was not permanent and both cases showed full recovery. Postoperative magnetic resonance imaging was performed in 7 of the 10 cases and showed no recurrences. Cervical hemilaminoplasty is a useful posterior approach method for spinal tumors and especially dumbbell-type tumors. This method provides wide exposure of the foramen and of the inside of the canal. Furthermore, it allows reconstruction of the posterior element of the spinal canal and results in good stability.

Preliminary clinical results for selective laminoplasty were satisfactory in all but 1 case. Although long-term results are not yet available, we consider this method to be less invasive and capable of giving satisfactory clinical results and benefits for elderly patients.