Surgical treatment of degenerative spondylolisthesis.

Degenerative spondylolisthesis is a common pathology, often causing lumbar canal stenosis. There is, however, no strong consensus regarding the various medical and surgical treatments available. Surgery is indicated mainly for perceived functional impairment; when the indication is accepted, several questions determine the choice of surgical strategy. Improvement in neurological symptoms is one of the main treatment objectives. For this, it is useful to perform radicular decompression. Some authors recommend indirect decompression by interbody fusion (ALIF, TLIF, XLIF), others by means of an interspinous spacer but the most frequent technique is direct posterior decompression. In degenerative spondylolisthesis, functional results seem to be improved by associating stabilization to decompression, to prevent secondary destabilization. The following risk factors for destabilization are recognized: anteroposterior hypermobility, angular hypermobility and large disc height. Two stabilization techniques have been described: "dynamic" stabilization and (more frequently) fusion. Spinal instrumentation is frequently associated to fusion, in which case, it is essential for fusion position and length to take account of pelvic incidence and the patient's overall pattern of balance. Posterolateral fusion may be completed by interbody fusion (PLIF or TLIF). This has the theoretic advantage of increasing graft area and stability, restoring local lordosis and opening the foramina. Surgical treatment of degenerative spondylolisthesis usually consists in posterior release associated to instrumented fusion, but some cases can be more complex. It is essential for treatment planning to take account of the patient's general health status as well as symptomatology and global and segmental alignment.