Faculty Bibliography

The Arnold-Chiari malformation is a developmental abnormality of the brainstem and cerebellum with displacement of these structures into the cervical spinal canal. Other anomalies involving the base of the skull and vertebral bodies are frequently present. In children, hydrocephalus and myelomeningocele may complicate the picture. In adults, symptoms usually do not occur until the third to fifth decade and then are often misdiagnosed as degenerative disease due to the presence of a syrinx in the cord. Treatment is focused on decompressing the spinal cord and brainstem.

Fourteen cervical spine motion segments consisting of two adjacent vertebral bodies and their connecting ligaments were tested in shear. Five had intact facet joints, five had bilateral facetectomy of 50% or less, and four had bilateral 70% facetectomy. Three to 5 mm of root could be exposed in the specimens with 50% facetectomy, and 8 to 10 mm in those with 70% facetectomy. Anterior-posterior shear tests were run alternately in compression and distraction. Facetectomy was found to have no effect on compression and distraction stiffness. Failure in the 70% facetectomized specimens was due to fracture of the remaining joint at 159 lbs. In the specimens with 50% facetectomy, a fracture load could not be established since failure of the specimen mounting occurred at 208 lbs, as it did in two of the specimens without facetectomy that were tested to failure. The difference in bone fracture at 159 lbs and mounting failure at 208 lbs is significant at p less than 0.05. Bilateral resection of more than 50% of the facet joint significantly compromises the shear strength of a cervical spine motion segment.

Chronic disc herniations into the vertebral body are a common finding and rarely produce symptoms. However, trauma may cause them to become symptomatic and to imitate other mass lesions

Several different syndromes, such as central cord, anterior cord, and root, have been described in injuries to the cervical spine. If stress analysis theory is used to analyze the applied forces that cause injury, the various syndromes appear to be interrelated and follow in an orderly progression that depend on the magnitude of the applied force. The modes of injury, either flexion or extension, theoretically produce similar injuries, dependent on the severity of the blow. These applied forces then cause the pathologic changes that have been described. This article applies commonly used principles of engineering design to analyze clinical syndromes and to demonstrate that these syndromes are related in a sequential manner.

Both the anterior and the posterior approaches are used in the treatment of cervical radiculopathy. An evaluation of the advantages and limitations of each method as compared to the other was made in isolated cervical spine segments. With a posterior approach, a quarter to a half of the facet joint must be removed to unroot the neural foramen. Anterior osteophytes in the region of the uncovertebral joint are difficult to reach from posteriorly unless they are very large. Using an anterior approach the amount of root decompression is easily overestimated. The lateral limits of the decompression must be beyond direct visualization to equal that obtained posteriorly. Osteophytes in the region of the uncovertebral joints are easily reached. Because some roots leave the dural tube a significant distance above the interspace, a soft disc fragment may migrate out of the interspace and behind the body to compress the root. This fragment may be missed from the anterior approach unless the root anatomy is evaluated carefully. X-ray films were taken at each step of the surgical procedures and were compared. A final set was taken using radiopaque markers to identify key structures. Plain x-ray films of the cervical spine reflect few if any of the anatomical alterations accomplished by operation. Oblique x-ray films do not visualize the entrance of the anatomical foramen, and osteophytes seen on this view may be well anterior in the neural canal.

A transthoracic approach with resection of a vertebral body was used to obtain access to an intramedullary vascular malformation of the thoracic spinal cord. The malformation consisted of three discrete intramedullary tufts of vessels fed by an abnormal branch of the anterior spinal artery arising from the T-9 intercostal artery. Although the abnormal branch of the anterior spinal artery did not appear to supply normal cord, the patient developed transient weakness postoperatively after occlusion of this artery. Follow-up angiography showed that one part of the malformation was still present and was fed by the T-y intercostal artery.