Question: I really liked the article "Safeguard Your Spinal Instrumentation Claims by Busting These 5 Myths" featured in Neurosurgery Coding Alert, Vol. 10, No. 3, but could you explain more about anterior instrumentation? Does anterior instrumentation have to include a plate placed on the outside of the vertebral body, or can the plate be within the interspace and include having screws placed through the plate into the vertebral body? California Subscriber Answer: You need to determine the specific device. You seem to be describing an intervertebral prosthetic device secured to the vertebral body with screws through an intervertebral plate. You would still report only +22851 (Application of intervertebral biomechanical device[s] [e.g., synthetic cage(s), threaded bone dowel(s), methylmethacrylate] to vertebral defect or interspace ...). Remember: Report only a single unit of +22851, regardless of how many devices the surgeon places at one intervertebral defect. If the surgeon places devices on multi-ple spinal levels, however, you may report multiple units of +22851 (one unit for each individual intervertebral defect).