31-year-old Man with Ankylosing Spondylitis
How to Treat?
The patient is a 31-year-old male with a long history of intractable lumbar back pain. He was diagnosed with ankylosing spondylitis and has been unable to work for the last 10 years secondary to pain. All of his pain is in the back and he denies any pain in his legs.
He notes that he has become increasingly "pitched forward" over the last several years and that he is unable to see more than 20 feet in front.He has almost no motion throughout his spine and walks with his knees flexed to allow him to see forward.
Clinical photos (Figures 1 and 2) demonstrate the patient's "pitched forward" posture.
Radiographs (Figures 3 and 4) of the patient's entire spine demonstrate almost complete autofusion through the thoracolumbar spine. The lateral radiograph (Figure 4) demonstrates a marked loss of lumbar lordosis and global sagittal imbalance with the C7 vertical plumb line (yellow line) roughly 10 cm in front of the pelvis.
The patient has ankylosing spondylitis with a loss of lumbar lordosis, as well as fixed sagittal imbalance.
Treatment Option Information
Traditionally, ankylosing spondylitis has been treated with extension osteotomies at the level of the deformity.
Originally described by Smith-Petersen in 1945, these osteotomies are done by taking the posterior elements completely off at the level of the disc space; the spine is then extended through the osteotomized segments and disc spaces. The amount of correction attainable through each disc space is roughly 10° to 15°.
After the osteotomy is done, it is usually necessary to perform anterior structural grafting at the levels of osteotomy to prevent anterior collapse and settling.
Another option for improving the sagittal imbalance is with a pedicle subtraction osteotomy. In a pedicle subtraction osteotomy, the posterior elements are carefully resected along with a decancellation of the body via a transpedicular route. The lateral margins of the pedicle and body are carefully removed and the entire spine is extended through the osteotomy.
The advantages of a pedicle subtraction osteotomy are that it is entirely accomplished through a posterior approach without the need for an anterior procedure. As well, 35° to 40° of lordosis can be expected with an adequate osteotomy.
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Because of the dramatic global sagittal imbalance and the fact that the patient already had a complete autofusion through his thoracolumbar spine, it was decided that a pedicle subtraction osteotomy was the best option. He underwent an L3 PSO with instrumentation and fusion from T12-S1. The amount of correction that was achieved in the sagittal plane as a result of the PSO was roughly 45°.
Lateral radiograph (Figure 5) demonstrate a much more physiologic lordosis. Note the wedged L3 vertebral body and the absence of pedicles at the L3 vertebral body. Also the C7 plumb line is at the back of the sacral endplate, a correction of 10 cm. In the lateral x-ray, the resected pedicles are seen at L3 (yellow arrow).
Clinical photos (Figures 6 and 7) taken 6 weeks post-operatively show a much improved posture.
The patient is happy with his progress and has much better vision because of improved posture.
Update on Selected Treatment
Dr. Lenke treated this patient about 10 years ago: If this patient came to him today, would he make the same treatment decision, given various advances in spine surgery techniques?
After reviewing the case in October 2012, Dr. Lenke said, "I would treat it exactly the same way today, and actually did the same operation on an ankylosing spondylitis patient 1 month ago. So although some things have changed over the past 10 years, some things have not!"
This case was treated in exactly the manner that I would have treated it.
When doing a pedicle subtraction osteotomy on an ankylosing spondylitis patient, it is essential that the surgeon does not cut all the way through anteriorly. In fact, all that is needed is to implode the posterior wall, pushing it anteriorly into the void of the vertebral body, and making sure the lateral cortex is also slightly weakened so that when you "crack" the spine, the spine remains coronally stable. From clinical experience I would note that with this type of patient, if you cut too far, you can destabilize the spine, thus risking coronal decompensation, and/or subluxation of the canal and vertebra resulting in the anterior cortical hinge at the front of the spine, breaking and destabilizing.
There should be some concern about blood loss during this procedure, although in these patients it's not that severe. In addition, if your screw fixation is questionable, you may have to use cement to augment the screws. However the best bone structure in a patient with ankylosing spondylitis is the posterior lamina. Therefore, you may elect to use hooks for fixation, although I prefer to use screws.