Mitsuhiro Yanase

Preoperative and postoperative magnetic resonance image evaluations of the spinal cord in cervical myelopathy.

To evaluate the morphologic changes of the spinal cord in patients with cervical myelopathy due to cervical spondylosis and ossification of the posterior longitudinal ligament, the authors measured the thickness and signal intensity of the cervical cord with magnetic resonance imaging in healthy adults and patients with cervicla myelopathy, and compared these findings. In patients with cervical myelopathy, the preoperative and postoperative magnetic resonance imaging findings were compared with the severity of myelopathy and postoperative results. In healthy adults, the anteroposterior diameter of the cervical cord wad 7.8 mm at the C3 level and decreased at lower levels. In the patients with cervical myelopathy, the preoperative spinal anteroposterior diameter was significantly reduced at various levels corresponding to the stenosis site within the vertebral canal. In the group with ossification of the posterior longitudinal ligament, the minimal anteroposterior diameter of the cervical cord tended to decrease with increasing severity of myelopathy. However no relationship was observed between the two parameters in the cervical spondylotic myelopathy group. In the group with ossification of the posterior longitudinal ligament, surgical results were good when the postoperative anteroposterior diameter was increased, whereas in the cervical spondylotic myelopathy group there was no relationship between the parameters. In the patients with myelopathy, a high intensity area was observed in about 40% of all patients before operation and about 30% after operation. However, the presence or absence of a high intensity area did not correlate with the severity of myelopathy or with surgical results in the group with ossification of the posterior longitudinal ligament and the cervical spondylotic myelopathy groups.

Indication of fusion for lumbar spinal stenosis in elderly patients and its significance.

Study Design Selection of surgical therapy for lumbar canal stenosis in elderly patients is discussed. Decompression alone and decompression with fusion were evaluated. Objectives To determine the indication of decompression with fusion for lumbar spinal stenosis in elderly patients. Summary of Background Data Although there is no objection to posterior decompression, which is regarded as the first choice of surgical therapy for lumbar spinal stenosis in the elderly, it is debatable whether or not fusion should be used with decompression. Methods The presence or absence of instability was defined by Posners method from preoperative plain radiographic lateral findings. Thirty-four elderly patients with lumbar canal stenosis were studied. Seventeen of the 34 patients were found to have instability. Ten of the 17 patients with spinal instability underwent decompression and instrumented fusion. The seven remaining patients with spinal instability underwent decompression alone. The 17 patients without spinal instability were treated by decompression alone. Preoperative symptoms, postoperative results, and changes in radiographic findings were compared among the three groups. Results The group treated by decompression and fusion showed the best results. The group treated by decompression in the presence of instability showed the worst results by the Japanese Orthopaedic Association back scores. Good results can be obtained by decompression alone only if the patients do not have instability as defined by Posner. Conclusions The definition of instability by Posners method proved useful for selecting elderly patients with instability for fusion treatment. Fusion with instrumentation should be performed on elderly patients with instability after decompression.

MRI findings in patients with a cervical spinal cord injury who do not show radiographic evidence of a fracture or dislocation

We investigated the usefulness of magnetic resonance imaging (MRI) in assessing cervical spinal cord injury in patients where there was no evidence of bone injury on radiographs, and examined the relationship between the MRI findings and the clinical prognosis of this injury. MRI allowed us to confirm directly the cause and severity of spinal cord compression in 30 of 31 cases. The patients with severe spinal cord compression demonstrated by MRI showed poor neurological improvement. In regard to the signal changes in the spinal cord, the patients who showed no signal change on Tl- and T2-weighted images had a better prognosis. MRI is a very useful non-invasive adjunctive imaging modality for diagnosis of this injury and for the evaluation of the compressed spinal cord. It also demonstrates potential in predicting neurological recovery.

Occipitocervical fusion with C1 laminectomy in children

Study Design. Eight children in whom atlantoaxial dislocation had developed underwent occipitocervical fusion using a rectangular rod. The postoperative results are presented, and the postoperative growth and deformation of the cervical spine were determined radiographically. Objectives. To investigate in a relatively long-term follow-up study whether occipitocervical fusion affects the growth of the cervical spine and induces spinal deformation. Summary of Background Data. It has been reported that children who have undergone C1-C2 posterior fusion are likely to develop abnormal curvature or deformation of the cervical spine as a result of a disturbance of growth of the fused vertebrae. There have been no studies, however, to confirm that these changes occur after occipitocervical fusion in children. Methods. The subjects were one boy and seven girls who had undergone occipitocervical posterior fusion during childhood. The average age at the time of surgery was 8.3 years, and the average follow-up period was 5.9 years. The following were assessed radiographically: redislocation of the atlas, bone union, changes in the curvature of the cervical spine, the height and width of the vertebral bodies, and the anteroposterior diameter of the spinal canal. Results. Solid bone union was achieved in all patients with maintenance of the reduced position at the time of surgery. None of the patients exhibited abnormal curvature of the cervical spine. The rate of increase in height of the C2 vertebral body was significantly less than that of vertebral bodies below C3. The rate of increase in width of the vertebral body and the anteroposterior diameter of the spinal canal of the C2 vertebral body and vertebral bodies below C3 did not differ significantly. Conclusions. Occipitocervical fusion with a rectangular rod is useful for treating atlantoaxial dislocation in children and yields excellent results because of the firm internal fixation it achieves. This surgery induced no apparent postoperative spinal deformations.

Transpedicular fixation of the lumbar and lumbosacral spine with screws. Application of the Diapason System

Forty-six patients with the Diapason transpedicular screw system for lumbar and lumbosacral fusions were analysed clinically. No implant breakage was observed, but one rod migrated. Additional sacral screws different in the length of the threaded portion are necessary in this system. Metallosis was noted in a few cases, but posed no significant clinical problems. This system, which is simple in structure, easy to use, and applicable to magnetic resonance scanning after surgery, is considered to be a useful instrumentation.