Herniated lumbar discs were making spontaneously increased amounts of matrix metalloproteinases, nitric oxide, prostaglandin E2, and interleukin-6. These products may be involved intimately in the biochemistry of disc degeneration and the pathophysiology of radiculopathy. Their exact roles certainly need further investigation, but their mere presence implicates biochemical processes in intervertebral disc degeneration.

This study shows that complication rates are similar for anterior versus posterior approaches to AIS deformity correction. Combined anterior and posterior instrumentation and fusion has double the complication rate of either anterior or posterior instrumentation and fusion alone. Combined anterior and posterior instrumentation and fusion also has a significantly higher rate of neurologic complications than anterior or posterior instrumentation and fusion alone.

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Incidence of C5 nerve palsy after cervical spine decompression was 6.7%. This is consistent with previously published studies and represents the largest series of North American patients to date. There is no statistically significant difference in incidence of C5 palsy based on surgical procedure, although there was a trend toward higher rates with laminectomy and fusion.

Study Design In vivo validation during functional loading. Objective To determine the accuracy and repeatability of a model-based tracking technique that combines subject-specific CT models and high-speed biplane X-ray images to measure three-dimensional (3D) in vivo cervical spine motion. Summary of Background Data Accurate 3D spine motion is difficult to obtain in vivo during physiological loading due to the inability to directly attach measurement equipment to individual vertebrae. Previous measurement systems were limited by two-dimensional (2D) results and/or their need for manual identification of anatomical landmarks, precipitating unreliable and inaccurate results. All previous techniques lack the ability to capture true 3D motion during dynamic functional loading. Methods Three subjects had 1.0 mm diameter tantalum beads implanted into their fused and adjacent vertebrae during ACDF surgery. High resolution CT scans were obtained following surgery and used to create subject-specific 3D models of each cervical vertebra. Biplane X-rays were collected at 30 frames per second while the subjects performed flexion/extension and axial rotation movements six months after surgery. Individual bone motion, intervertebral kinematics, and arthrokinematics derived from dynamic RSA served as a gold standard to evaluate the accuracy of the model-based tracking technique. Results Individual bones were tracked with an average precision of 0.19 mm and 0.33 mm in non-fused and fused bones, respectively. Precision in measuring 3D joint kinematics in fused and adjacent segments averaged 0.4 mm for translations and 1.1° for rotations, while anterior and posterior disc height above and below the fusion were measured with a precision ranging between 0.2 mm and 0.4 mm. The variability in 3D joint kinematics associated with tracking the same trial repeatedly was 0.02 mm in translation and 0.06° in rotation. Conclusions 3D cervical spine motion can be precisely measured in vivo with sub-millimeter accuracy during functional loading without the need for bead implantation. Fusion instrumentation did not diminish the accuracy of kinematic and arthrokinematic results. The semi-automated model-based tracking technique has excellent repeatability.