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.
Intradiscal gas accumulation, better known as vacuum disc, is considered to be a benign indication of degenerative disc disease. On occasion it can be a cause of symptoms. A case is reported in which gas leaked after surgery into the spinal canal, causing a foot drop. The symptoms and gas disappeared spontaneously without further treatment.
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.
Normal neck motion is a complicated phenomenon. A primary motion results from an applied force or torque. Secondary coupled motions also result as a consequence of the primary motion. These resulting coupled motions were measured in isolated cervical motion segments using three-dimensional videophotogrammetry with a coordinate system fixed in space. A cross coupling algorithm provided error correction and conversion from local to true cartesian coordinates. The data were analyzed by computer, and the true coupled motions resulting from any applied force were obtained. A second group of specimens was facetectomized, and the experiments were repeated. After facetectomy, a moment about the anteroposterior axis resulted in marked reduction in lateral displacement, decrease in vertical displacement, and decrease in rotation about the vertical axis. Results were significant at P less than 0.01 and represent a significant decrease in coupled motions resulting from lateral bending. At P less than 0.05, a laterally applied force causes less lateral displacement and lateral flexion, but more longitudinal displacement. Flexion and extension movements are not significantly altered after facetectomy.
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