The principle of both techniques is injecting bone cement into the vertebral body. This is usually done percutaneously, which means through a needle inserted through the skin. It can also be done during open spine surgery. The main difference between vertebroplasty and kyphoplasty is the technique of administering the bone cement. In vertebroplasty, the cement is injected under pressure into the bone. In kyphoplasty, a balloon (or other device) is inserted into the vertebral body first to create a space where the cement is then injected under lower pressure. Inflating the balloon will also restore some of the height of the collapsed vertebra. This is not possible with vertebroplasty. Depending on the underlying problem, different kinds of cement can be injected. Kyphoplasty is significantly more expensive than vertebroplasty due to the equipment necessary for the procedure.
Both procedures are always done under close x-ray control.
The classic and still best indication for both techniques is pain due to vertebral collapse. This frequently occurs in osteoporotic fractures in elderly patients. Other indications include tumours like myeloma. Often the vertebral body collapsed in a wedge-shape form. Restoring some of the normal box-like shape is thought to prevent further collapses at other levels although the evidence for this is very limited. In patients with multiple fractures it seems more important to restore the shape than in a single level.
It is essential that patients had appropriate examination and investigations to decide whether a vertebroplasty or kyphoplasty is indicated. A simple x-ray showing a vertebral collapse and some back pain are not sufficient and patients should be seen by a spinal specialist / surgeon before.
Leakage of cement into the spinal canal can lead to paralysis although this is very rare. It also may leak into the veins just in front of the spine leading to tiny cement particles blocking vessels in the lung (so-called ‘cement-embolus’). Again, this is rare. These two complications are more frequent in vertebroplasty because of the higher pressure used to inject the cement.
Insertion of the needle through the pedicle of the vertebral body (see ‘The normal structure of the spine’) can injure nerve roots, the spinal cord or fracture ribs, or part of the vertebral body (transverse process, pedicle). Injury to the lungs (haemothorax) or great vessels in front of the spine can also occur but is exceptionally rare.