Surgical Treatment: Fixed Sagittal Imbalance in a Very Young Female Created by Settling of Cages at L4/L5 and L5/S1, Terated by Pedicle Subtraction Osteotomy

Surgical Treatment
At this point in time (12/01), she then presented for surgical revision to the author of this case report. She has lost 30-degrees of lordosis from L4 to the sacrum. She cannot stand erect. Her C7 plumb falls substantially in front of her L5/S1 disc. She appears to have a solid fusion at L5/S1 and a pseudarthrosis at L4/L5.

It is anticipated that any efforts to try to remove the threaded cages at L4/L5 would be quite complex. They were placed through a paramedian approach. The vena cava swings across the L4 and L5 segments anteriorly. Although it may be relatively easy to remove threaded cages at L3/L4 and L5/S1 after they have been placed through an anterior approach, it is anticipated that removing them at L4/L5 would be potentially quite difficult and potentially dangerous because of difficulties with getting the vena cava dissected again.

Therefore, the choice was made to do a pedicle subtraction osteotomy at L4 and to extend the fusion up to L3. The bone graft used was exclusively local bone graft. The patient had the ilium harvested on both sides with prior surgeries.

Note at 6 days postop, the patient is able to stand more erect than preoperatively. Also note the difference in her gait. She still has to achieve a solid fusion from L3 to the sacrum, and in particular from L3 to L5. We obviously will not know if we have achieved a solid fusion until she is 3 to 5 years postop.

Figure 5

This is her standing long cassette AP and lateral x-rays done 6 days following the surgical reconstruction. The surgical reconstruction consisted of a pedicle subtraction osteotomy at L4 and otherwise posterior fusion and instrumentation from L3 to the sacrum. Because of congenital anomalies, it was not possible to safely place a pedicle screw at S1 on the right side.

This case shows, though, how easy it is to produce a sagittal imbalance problem when fusing segments in the distal lumbar spine and also demonstrates that sagittal imbalance can be created by producing a relative kyphosis rather than a frank kyphosis.

Bibliography
1. Bridwell KH, Lewis SJ, Lenke LG, Baldus C, Blanke K: The results and complications of pedicle subtraction osteotomies for treated of fixed sagittal imbalance. J Bone Joint Surg [Am] (in press)

2. Thomasen E: Vertebral osteotomy for correction of kyphosis in ankylosing spondylitis. Clin Orthop 1985;194:142-152