SPINAL FUSION OVERVIEW
The spine is one of the most vital parts of the human body. It serves two purposes – provides skeletal support to the trunk and upper half of the body, and protects the spinal cord, which makes all bodily movements possible.
An increasing number of patients will experience some form of back pain during their lifetime. Depending on the severity of the pain and its cause, the patient may require medical attention such as spine surgery. In most cases, spine surgery involves correcting the skeletal structure and maintaining it in the corrected state, frequently referred to as Spinal Fusion.
Spinal fusion is a surgical technique to join two or more vertebrae. This is required to maintain any skeletal correction that was achieved during the surgical procedure. Implants such as screws and rods are used to provide an ‘internal cast’ and keep the fused vertebrae in the desired position, postoperatively.
Screws are used to anchor the ‘internal cast’ to the vertebral bodies. Screws that are placed in the vertebral bodies are inserted through pedicles. Pedicles are tubular bony structures on either side of the spinal cord at each vertebral level. Due to the proximity of the pedicles to critical neural elements (spinal cord on the medial side and nerve roots on the lateral side), it is important to ensure that the pedicle wall is not breached during screw insertion. Therefore, the exact positioning of these implants is necessary in order to avoid complications and achieve successful surgical outcomes.
The most frequently used technologies to ensure accurate placement of pedicle screws include:
- Fluoroscopy – Intra-operative x-ray radiography
- 3D navigation technologies
- Intra-operative neural monitoring (EMG – electromyography)
Fluoroscopy is a technique for continuous or intermittent x-ray monitoring. While the pedicle is being drilled (in preparation for screw insertion), the surgeon uses fluoroscopy to monitor the trajectory of the drill tool, and redirects as necessary to ensure accurate orientation. Fluoroscopic images are available only in one plane. However, since spinal correction and fusion is a three-dimensional procedure, fluoroscopic images in a minimum of two planes is necessary to ensure correct trajectory for the (pedicle) screw.
Fluoroscopic images are generated from low-dose x-rays. However, usage of bi-planar fluoroscopy can quickly accumulate the amount of x-ray radiation a patient is receiving. Several clinical papers have been published about the usage of fluoroscopy in spinal surgery.