Characterization of the cervical spine as stable or unstable is frequently an important part of diagnosing and treating patients with cervical spine disorders. This characterization of the spine is particularly important in determining whether to treat the patient conservatively or with surgery, and for monitoring the success of the treatment. Over 800,000 flexion-extension x-rays are used each year to diagnose spine stability, despite the fact that numerous studies have shown substantial errors in the assessments made using these studies. Despite the accepted importance of spinal stability in many patients, there are no validated, reliable measurements of stability that clinicians can commonly use in their day-to-day practice. Software that provides quantitative measurements of cervical spine stability, which could be used in routine clinical practice, has been developed by the applicant company, independently validated, and approved by the FDA. During Phase I, a database describing normal motion was started, and data were collected that show that a much higher proportion of motion abnormalities in patients with cervical spine disorders. The data also suggest the focus of clinicians and researchers on intervertebral rotation may be ineffective, since other motion abnormalities are more common in patients. Although the basic technical development is largely completed, this innovative technology is not in widespread clinical practice. Proof of clinical efficacy is required before clinicians will adopt a new technology and before payors will routinely reimburse for its use. The specific aims of Phase II are to provide evidence that the measurements have clinical value and can be effectively delivered in routine clinical practice. These aims will be accomplished by collecting and analyzing cervical spine stability in 100 patients with specific cervical spine disorders. A trial implementation of the technology, delivered via a remote image processing laboratory, will also be completed and analyzed. Successful completion of these aims will yield data showing that quantitative measurements of intervertebral motion significantly improve inter- and intra-observer error, and that these measurements significantly change the treatments offered to patients. This would facilitate adoption of the new technology into routine clinical practice. A clinically efficacious method to quantify cervical spine stability could benefit hundreds of thousands of patients. [unreadable] [unreadable] [unreadable]