Quantitative discomanometry and acute disk injuries: an experimental model.

Quantitative discomanometry is a study of intradiscal pressure changes during quantitative injection. The purpose of this study was to determine if correlations exist between discomanometric parameters and disk injuries. Sixteen three-vertebrae porcine spine segments, with two intervening disks, were subjected to standardized high-speed trauma. The injuries were documented by a radiographic injury score (RIS), using pre- and posttrauma lateral radiographs. An anatomic injury score (AIS) also was obtained, based on an anatomic dissection and mid-sagittal plane cuts of the frozen specimen. Before the cutting, each of the disks was subjected to quantitative discomanometry, providing pressure/volume curves. Significant negative correlations were found between the RIS and the maximum pressure sustained (R = -0.60, p < 0.001), and pressure/volume slope (R = -0.60, p < 0.001). Similar relationships were found between the AIS and the maximum pressure (R = -0.71, p < 0.001), and pressure/volume slope (R = -0.63, p < 0.001). This study suggests that quantitative discomanometry can be used to quantify disk injuries. Because the intradiscal pressurization mimics the physiology with weight bearing, its use as a measure of integrity of the end-plate-annulus-end-plate enclosure might be justified.

An anatomic basis for spinal instability: a porcine trauma model.

To determine the anatomic basis for spinal instabilities, 16 porcine cervical spine specimens were subjected to a well-defined sagittal plane trauma. The multidirectional instability of each specimen was measured before and after trauma. Detailed anatomic dissections were performed on each traumatized specimen to quantitate the extent of injury to several distinct anatomic structures and columns. Multiple regression models were constructed to determine which anatomic structures and columns correlated best with each multidirectional instability. Flexion instability correlated best with injury to the interspinous/supraspinous ligaments and the ligamentum flavum. Extension instability correlated best with anterior longitudinal ligament and pedicle injury. Axial rotation instability correlated best with anterior disc-end-plate and capsular ligament injuries, while lateral bending instability correlated best with posterior disc-end-plate injuries. Anterior column injuries correlated best with extension, axial rotation, and lateral bending instabilities, while posterior column injuries correlated best with flexion instability. Finally, individual anatomic structural injuries had higher correlations with multidirectional instabilities than did the injuries defined by the anatomic columns.

Cervical spine stabilization. A three-dimensional, biomechanical evaluation of rotational stability, strength, and failure mechanisms.

The three-dimensional rotational biomechanical properties of several different types of posterior stabilizing procedures are reported. A severe ligamentous and bony injury was simulated with three vertebral body human cervical spine segments. Good stabilization was noted for all of the repairs in flexion loading. Without polymethylmethacrylate supplementation, none of the repairs was stable in extension. All of the repairs provided reasonable stabilization for lateral bending except for the posterior wiring without methacrylate, and all but the posterior wiring and facet fusion provided reasonable stabilization against axial rotation loading. The supplementation of all of these repairs with polymethylmethacrylate added considerably to the stability of all the constraints. These findings may be useful in clinical decision-making for determining the kind of repairs and postoperative brace protection to use.

Cervical spine injury patterns in three modes of high-speed trauma: a biomechanical porcine model.

Cervical spine fractures and dislocations account for a large number of deaths and disabilities in the United States each year. More knowledge of the anatomic injuries produced by known trauma may yield practical information regarding injury mechanisms and treatment alternatives. In this experiment, 16 porcine cervical spine three-vertebrae segments were subjected to flexion-compression, extension-compression, and compression-alone trauma modes. The resultant injuries were scored by anatomic dissection. The results were analyzed for variance with trauma mode using nonparametric analysis. The three modes of trauma were found to have statistically significant differences in the degree of injury to the spine and its structural components. Extension-compression trauma produced the greatest injury scores to the whole spine and to the anterior structures. Flexion-compression trauma produced the highest posterior element injury scores. Compression trauma alone produced the lowest injury scores and no definitive pattern of anatomic injuries. The severity of anatomic injuries in this model relates most to the addition of bending moments to high-speed axial compression of the spine segment.

Multidirectional instabilities of traumatic cervical spine injuries in a porcine model.

Spinal injuries due to high-speed trauma are significant problems. The method of treatment depends on the stability determination of the injured spine. Young pig spines were injured at high speed to produce clinically relevant fractures and dislocations. The injuries were produced by dropping a mass onto the superior vertebra and causing three major types of trauma: flexion-compression, extension-compression, and pure compression. The multidirectional instability of each spine was measured before and after trauma by applying pure moments to the three vertebrae segments. Lateral radiographs were taken of each intact and injured spine. Flexion trauma produced the greatest instabilities in flexion and extension, while extension trauma produced the greatest instabilities in axial rotation and lateral bending. Lateral radiographs were found to be inaccurate predictors of spinal instability.