A Publication of WTVP

Digital motion X-ray (DMX), or video fluoroscopy, describes a technique used to evaluate the spine and peripheral joint movement or function, which isn’t accurately assessed by other diagnostic modalities such as traditional X-rays, MRI, and CAT scans.

Fluoroscopy isn’t a new diagnostic tool; however, before our modern imaging and recording devices were available, the radiation dose was increased and image quality was limited. Today’s DMX technology allows these studies to be performed quickly using much lower radiation doses. The study is recorded on videotape and a DVD instead of the traditional X-ray film. The studies can then be reviewed in real time, slow motion, or freeze frame. The ability to instantaneously review the image allows for better and more accurate interpretation. Each frame (30 per second) can be frozen and produced individually, allowing for a total of 2,700 individual views from one DMX study. A special picture-in-picture feature during the study allows for both patient identification and correlation of the patient’s range of motion to the X-ray findings.

The ligaments are responsible for the majority of the structural integrity of the joints. The ligaments are composed primarily of collagen, which is elastic. The elasticity, like a rubber band, helps protect the ligament and allows for the normal motion of the joints. There are pain fibers associated with these structures. When a ligament is damaged, the collagen is replaced with fibrous tissue better known as scar tissue. Fibrous tissue doesn’t have the elastic properties of collagen and is more susceptible to repeat trauma. Since the ligaments no longer have their normal elasticity, even normal motion often causes pain. In an attempt to prevent pain, especially in the spine, the muscles often go into spasm attempting to restrict the painful movement. Muscle spasm also is painful, and the patient is caught in a vicious cycle.

Conventional flexion and extension X-ray views of the spine often fail to demonstrate ligament instability. The time delay between positioning the patient and taking the X-ray allows the muscles to realign the spine. Some joint dislocations, such as in the shoulder, may sublux and reduce spontaneously. This type of condition wouldn’t be demonstrated with static films, and a DMX would be a better diagnostic tool.

Information obtained from a DMX provides the treating physician detailed information, thus increasing treatment specificity, improving the treatment outcome, and decreasing the necessity for additional diagnostic tests and referrals. DMX is a valuable and accepted diagnostic modality in the assessment of soft tissue injury. Ligamentous injuries never fully heal and, therefore, are considered permanent. DMX provides a cost-effective, low-radiation tool to better diagnose and document soft tissue/ligamentous injury. It’s the diagnostic test of choice in the proper setting. IBI