Edward D. Simmons

Goals of Surgical Treatment

Osteotomy of the spine in ankylosing spondylitis is done to correct fixed-rigid deformities of the cervical, thoracic, or lumbar spine that are impairing functional status and quality of life. These deformities are predominantly in the sagittal plane.

Diagnosis

Ankylosing spondylitis is an inflammatory arthritis of the spine presenting in the early stages with an inflammatory arthritic pain typically involving the sacroiliac joints initially and then spreading to involve other portions of the spine. Early on there is normal or very mildly limited range of motion; however, as the disease progresses, a fixed ankylosed spine typically results. The diagnosis is confirmed with clinical and radiographic evaluation as well as serologic testing. The patients typically have a human leukocyte antigen (HLA) B27 tissue type.

Indications for Surgery

With ossification of the spine in ankylosing spondylitis, the spine may eventually fuse in a kyphotic position, and this can involve lumbar, thoracic, and cervical areas of the spine. In the cervical spine, the flexion deformity is often a result of a misdiagnosed fracture that went on to heal in a forward flexed position.

1. Indications for cervical spine osteotomy are for flexion deformity where there is impairment of the visual field to see ahead and where patients have difficulty with personal hygiene and function. Difficulty with swallowing is common. The most severe case of this is the “chin on chest” deformity.

2. Kyphotic deformity of the thoracic spine in ankylosing spondylitis does not usually reach proportions that require surgical correction. Combined anterior and posterior approaches are necessary. The diaphragm must not be violated, as these patients breathe solely with their diaphragms due to absence of motion through the costovertebral joints.

3. Osteotomy of the lumbar spine is commonly done for lumbar hypolordosis or actual kyphosis giving rise to a fixed flexion deformity.

Contraindications

Contraindications include patients who are not suitable candidates for medical reasons and where the severity of the deformity does not warrant the procedure. Severe osteopenia is also a relative contraindication.

Advantages

The technique as described allows for the osteotomy to be done from a single-stage posterior approach in the lumbar and cervical spines and allows for a high degree of correction to be obtained in a safe manner with the least morbidity to the patient. The results can be very gratifying in terms of overall improvement in functional status and quality of life.

Disadvantages

The disadvantages of the procedure predominantly are those related to potential complications or morbidity from the procedure. Many of these patients have concomitant medical illnesses and cardiac problems, and must be carefully evaluated preoperatively from a medical standpoint. Major neurologic problems are relatively infrequent; however, they can be a major problem when they occur.

Lumbar Spine Osteotomy

Procedure

The lumbar spine osteotomy is done with the patient in the prone position. The patient must be carefully positioned on the operating table in a flexed knee-chest position. The typical table used is an Andrews table. Careful positioning is also necessary as these patients have fixed ankylosed spines, and undue pressure in any one particular area must be avoided. The thoracic chest support must often be elevated considerably to accommodate the patients on the operating table. The procedure is done under spinal cord monitoring. A wake-up test can also be used if necessary. The osteotomy is done at the L3-L4 level, which is the normal center of lumbar lordosis. This is also below the conus medullaris, and the spinal canal volume is fairly reasonable at this level. A preoperative computed tomography (CT) scan should be done to evaluate the spinal canal preoperatively. The apex of the osteotomy is at the L3–4 disc space and the posterior elements are removed to accomplish the realignment of the spine. The bone is removed with rongeurs as well as power burs and Kerrisons.