Introduction: Previous animal models for spinal cord injury required laminectomy and exposure of the spinal cord to create direct trauma. Imaging studies were not always possible during these experiments. Furthermore, previous studies did not permit a correlation of extent of cord compression with cord injury. The purpose of our study is to determine the relationship between extent of cord compression and the increase in cord pressure in an in-vitro burst fracture model of graded cord compression.
Methods: 12 Porcine spinal sections, six thoracic, and six lumbar were harvested from 30kg pigs. Each spine segment consisted of 7 vertebrae. With the cord exposed and tied off at each end. A hole was drilled in the middle of the most central vertebra of the segment that was carefully created from the most anterior portion of the vertebral body through the posterior wall of the vertebral body without damaging the underlying cord. A 12.5 mm diameter DHS hip screw with 3 mm thread pitch was then inserted into this hole and advanced in a graded fashion. Pressure at the cord was monitored by means of the central hole running longitudinally down the DHS screw toward the cord. As the DHS screw was advanced, pressure was measured at the tip of the screw where it contacted the spinal cord. A radiolucent dye was administered in the subdural space to create a myelogram during the procedure. All the segments were observed under fluoroscopy to monitor the advance of the DHS screw.
Results: Accurate measurement of the time averaged pressure showed no significant difference (p<0.05) in the pressure/compression curves before and after radiopaque dye injection. . Cord Pressures increase dramatically at approximately 65% to full compression.
Conclusions: Cord Compression can be obtained in a systematic and controlled manner. Cord Pressures increase dramatically when cord compression reaches approximately 65% to full compression. Our samples exhibited Creep Phenomenon- the tendency of a material to slowly move or deform permanently under the influence of stresses, as repeated measurements at same percentage of compression showed substantially decreased pressures.
Patient Care: Basic understanding of the bio-mechanics of the spine. The correlation between cord compression and injury by measuring the intra-spinal pressure applied on the cord. will assess in better surgeries, care of the spine and the inventions of spine related medical devices.
Learning Objectives: DESIGN A MODEL FOR SPINAL CORD COMPRESSION USING PORCINE SPINES TO DETERMINE POINT AT WHICH COMPRESSION RESULTS IN INCREASED CORD PRESSURE
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