Review Question - QID 8991

In this patient with progressive infantile idiopathic scoliosis with no tether, cyst, or syrinx on MRI and RVAD >20 serial casting is the next best step in treatment.

Infantile idiopathic scoliosis is a form of early onset scoliosis (EOS) that presents in children under 3 and most commonly as a left thoracic curve. Patients may present with a family history and should be examined for neurologic findings or physical exam findings of spinal dysraphism. Standard AP and lateral radiographs should be examined for congenital vertebral defects as well as Cobb angle, rib vertebrae angle difference (RVAD), and rib phase. MRI can be obtained to evaluate for other associated conditions such as tethered cord, cyst, syrinx, or tumor. Patients with phase 2 ribs, RVAD >20, Cobb angle >30, and flexible curves should be treated with serial derotational casting. Those with Cobb angles >60 and who have failed derotational casting should be considered for growing rod constructs as close to skeletal maturity as possible.

Sanders et al. followed 55 patients with progressive infantile idiopathic scoliosis for 1 year following casting. They found 49 of the 55 patients responded to casting with improved alignment and space available for the lung. They conclude that serial casting for infantile scoliosis results in full correction if done in patients with curves less than 60 degrees and under 20 months of age.

Tis et al. reviewed the available treatment options for early onset scoliosis (EOS). They state those patients in whom no surgical correction has been attempted with curve progression of 10 to 20 degrees or an RVAD >20 and rib phase 2 did well with derotational serial casting. Larger magnitude curves and older aged patients were at risk for failure of casting and subsequent surgical intervention.

Waldron et al. studied 20 patients with early-onset scoliosis treated with serial Risser casting. They found a mean major curve decrease from 74 degrees to 53 degrees in those patients treated with Risser casting. The conclude that serial Risser casting is safe and effective and can stabilize children with large curves until they are at a suitable age for other treatment options such as growing rods.

Figure A shows a patient with a left side thoracic curve. Figure B shows an MRI of the same patient with the conus medullaris ending well proximal to the L2 level.
Illustration A shows the calculated RVAD value for this patient of roughly 80 degrees. Illustration B shows this patient with significant curve correction following 8 months of serial derotational casting. Illustration C depicts RVAD calculation by subtracting the difference in the angle of the vertebra and rib at the apex of the deformity.

Incorrect answers:
Answer 1: Observation would be appropriate for a Cobb angle <30 degrees and RVAD <20 degrees
Answer 3: Obtaining an MRI to evaluate for tether, cyst, or syrinx is important however this MRI shows no tethering of her cord.
Answer 4: Vertebrectomy with fusion is indicated in some cases of congenital scoliosis or severe spinal deformity but is not required in this case. She is also too young/small for instrumentation
Answer 5: Posterior spinal fusion is most commonly used for adolescent idiopathic scoliosis