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Woman with Ankylosing Spondylitis

Deformity Makes It Difficult to Look People in the Eye


A 66-year-old-female with ankylosing spondylitis (AS) presents with deformity and difficulty with forward gaze. She's on medications for her AS but is otherwise in good health. She ambulates independently without any aids. Her main complaint is her hip positioning and difficulty looking people in the face when they speak to her. She has no previous surgeries.


Her neurological exam was normal. She had good rotation of her neck but had limitations in flexion and extension. She had a forward posture and a forward head position. She was coronally balanced.

Pre-treatment Images

ankylosing spondylosis, clinical photographs, pre-treatment radiographsPre-treatment clinical photographs and images


Ankylosing spondylitis with sagittal imbalance

Suggest Treatment

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Selected Treatment

Choice 4: Upper thoracic pedicle subtraction osteotomy and lumbar pedicle subtraction osteotomy. 

The imaging showed a lack of lumbar lordosis as well as kyphosis in the proximal thoracic region. It was felt both were contributing to her sagittal malalignment and that both needed to be addressed to provide her proper balance. The upper thoracic was chosen to avoid any possible complications with regards to the lower cervical nerve roots and would provide greater correction as it is more distal.

Post-treatment Images

ankylosing spondylitis, post-operative images


She was in the hospital for one week. She is now 3 months post-op and has no complaints.

Case Discussion

Ankylosing spondylitis (AS) represents a classic disease process for dealing with fixed sagittal plane abnormalities. With a completely ankylosed spine, the issue becomes what is the functional problem and that, therefore, directs how to fix it. Horizontal gaze is the most conserved feature in the human being. It is why AS patients will go to extremes to maintain it. Initially, they flex their hips and knees. In extreme cases, they resort to hip flexion, looking between their knees, and walking backwards.

This patient has a chin thrust and inability to see the horizon. In addition, she has lost her lumbar lordosis. The questions, then, are how much is needed and where should it be done. A real danger in this case is over correction resulting in the so-called birdwatchers gaze, being unable to see the ground.

The neurological strategy with the lowest risk is probably a lumbar pedicle subtraction osteotomy. The strategy, to most physiologically correct the deformity, would be to fix it in the cervical spine. This, however, carries a significant risk for neurological complications and potentially vascular problems involving the vertebral arteries. An alternative would be a cervicothoracic osteotomy below the entry of the vertebral artery into the bony canal. There may be a risk of C8 nerve root problems associated with this osteotomy. In the past, Zielke did multiple level Smith-Petersen osteotomies to restore true normal segmental sagittal contour.

My initial approach to this problem has been to perform the lumbar PSO first and then assess the patient after healing to determine if the amount of correction is adequate. It is possible to do trigonometric calculations to determine the precise amount of correction necessary, but the execution of the osteotomies and obtaining this precise correction has proven challenging.

Dr. Lewis has done a superb job correcting the radiographic abnormality. In looking at the post-operative lateral, I suspect that the patient has to rotate her hips (trunk flexion) in order to see the ground. However, this motion is probably very well tolerated. She may find sitting and looking down more challenging. I suspect this limitation is minimal and is such that the patient does not feel that it would merit additional intervention.

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