Severe spinal problems with stenosis or herniated discs are often treated with surgery. Some or all of the bone and joint on the back of the spine is removed to take the pressure off the disc or spinal nerve roots. This is called dorsal decompression. In this case, dorsal means the back of the spine.
Researchers in Germany used a three-dimensional computer simulation of the spine. They found a way to create the effect of tiny degrees of movement, all parts of the disc, and some ligaments. They also simulated the capsule of the facet joints and normal or diseased discs.
Different methods of dorsal decompression were simulated. First the upper half of the facet joint was removed in the computer model. One of the ligaments was taken out, too. Then both upper parts of the joint (one on the right and one on the left) were removed.
Bit by bit pieces of the bone were removed or resected. Each time a new method was used, calculations were made of the stresses, loads, and strains on the parts of the spine. Loads were calculated during standing and for all motions (bending forward and back, as well as turning the spine). The authors looked for the points of greatest stress in the spine and when they occur. The forces between the facet joints were measured for each amount of resection.
The authors report that the computer model works better than using cadavers (human bodies preserved for study). Many different changes can be made with the push of a button on the computer. And the cost and small number of cadavers ready for use limit the number of studies that can be done.