Surgical treatment of adolescent idiopathic scoliosis requires focus on sagittal plane

Adolescent idiopathic scoliosis is hypokyphotic and, according to a presenter, physicians should work up patients that do not have the typical sagittal plane.

In a presentation, Lori A. Karol, MD, discussed treatment options for adolescent idiopathic scoliosis, when treatment is required and what surgical techniques are most effective in adolescents with this deformity.

“Idiopathic scoliosis is hypokyphotic. Patients that do not have the typical sagittal plane deformity require further evaluation. Posterior spine fusions can worsen hypokyphosis. Coronal plane correction is achievable with very rigid systems, but it can worsen thoracic hypokyphosis,” Karol, who is at the Texas Scottish Rite Hospital, in Dallas, said. “So we must pay attention to the sagittal plane.”

Lori A. Karol

Adolescent idiopathic scoliosis (AIS) is a lordotic deformity, according to Karol, and not just cosmetic.

Pulmonary testing has shown there is decreased pulmonary function in patients who have loss of thoracic kyphosis, she said.

Additionally, AIS can affect the quality of life in patients with this deformity, she said.

“There is diminished quality of life in patients who have exacerbated hypokyphosis following spinal fusions. When we look at patients’ quality of life questionnaires after surgery, it seems that they are better if their is thoracic kyphosis has been restored,” Karol said. “With thoracic hypokyphosis, there is a concomitant disturbance of the normal cervical lordosis and lumbar lordosis. What the implications of this are in the future are unknown.”

Boys seem to be more predisposed to postoperative loss of thoracic kyphosis, Karol said, and a patient with hypokyphosis preoperatively is more at risk.

Spinal instrumentation used during scoliosis fusion consists of rods and anchors, most commonly pedicle screws. The rods themselves, Karol said, can unbend intraoperatively. “Studies have shown that rods can plastically deform or lose their kyphotic bend when we insert them during the correction of thoracic scoliosis. This is especially true of the concave side rod, which can straighten up to 21° during surgery. Therefore, there are recommendations to over-contour the concave rod to try and address the hypokyphosis,” she said. “Maintenance of kyphosis is more likely when using a rod that is stiffer or larger in diameter.”

Also, according to Karol, limbering up the spine can be helpful and osteotomies may increase the flexibility of the spine. A study has come out that shows there was greater blood loss and greater operative time in patients who had releases, she said.

Another type of surgical technique using apical sublaminar wires has also been shown in studies to be helpful, Karol said.

“Using wires at the apex of the deformity may draw the spine up to a properly contoured rod, but it does increase the neurologic risk of the procedure,” she said. “Using screws that are less constrained can reduce the rigidity of the construct and allow for more kyphosis. Reduction screws are commonly used currently. They can function like a sublaminar wire and draw the spine closer to the rod to restore kyphosis. This is a more common technique currently,” according to Karol. – by Robert Linnehan

Reference:

Karol LA. Symposium D: Abnormal sagittal alignment in scoliosis: When is treatment required & what surgical techniques are effective? Presented at: American Academy of Orthopaedic Surgeons Annual Meeting; March 11-15, 2014; New Orleans.

For more information:

Lori A. Karol, MD, can be reached at, 2222 Welborn St., Dallas, TX 75219; email: lori.karol@tsrh.org.

Disclosure: Karol has no relevant financial disclosures.