Patients with AS can suffer severe changes in the spine. Some may become so bent forward they can no longer lie down flat, stand up straight, or look where they’re going. Surgery to fuse the spine in a more upright position is often advised.
Opening wedge osteotomy (OWO) is one operation used to correct the deformity. In this procedure, several vertebra are cut loose and tipped backward. This is called sagittal rotation. Metal rods and screws are used to hold the bones in this position. The effect is to extend or straighten the spine.
This is the first report of sagittal translation (ST) of the vertebra as a result of the operation. In ST the tilted vertebra slide forward over the vertebra below. The authors document how often this happens and suggest how this change might affect patients.
In this study of the 127 adults having an OWO, 27 percent developed ST. The authors suggest this may be one way the vertebra shifts to further correct the spine. ST may be linked to the amount of tilt or correction.
The elasticity and tension of the soft tissues around the OWO may also be a factor. If the soft tissues are tight and hold back the tilt or rotation, then ST may be more likely to occur.
The authors advise surgeons to watch for ST after OWO. Further surgery may be needed to prevent or treat neurologic problems from the ST. More studies are needed to measure and grade ST. Predicting the results of SR may help prevent problems like ST.