Posterior Column Spinal Osteotomies in the Treatment of Adolescent Idiopathic Scoliosis. A Randomized Clinical Trial

Background AIS is the most common indication for major surgery in adolescents. The current standard of care for idiopathic scoliosis with a curve magnitude of over 40-50˚ is posterior spinal fusion (PSF) with pedicle screw fixation. Pedicle screws are implanted using posterior subperiostal approach into pedicles and vertebral bodies and the screws are then connected with longitudinal rods to allow correction of scoliosis. Spinal fusion is obtained by local bone graft on decorticated posterior spinal elements. 70% correction of scoliosis is expected with standard PSF surgery for idiopathic scoliosis (1).

Posterior osteotomies are used to facilitate correction of scoliosis during PSF. Concept of PCO was originally introduced in 1945 for treatment of spinal deformities in patients with rheumatoid arthritis and ankylosing spondylitis (2). Indications for use of PCO have later broadened to surgical correction of Scheuermann´s kyphosis and idiopathic scoliosis (3). Currently, the most commonly used technique was described by Ponte (4). In Ponte osteotomy a wide resection of the thoracic facet joints, laminae, and ligamentum flavum is conducted to generate a 5-10 mm posterior gap that closes with segmental instrumentation (4). Originally these osteotomies were utilized to correct hyperkyphotic deformities allowing approximately a 10-degree correction per spinal level (5). In AIS increase of curve correction up to 7%, and 15% correction of rip hump has been described with PCO (6). Up to 15% critical neuromonitoring changes have been observed in patients undergoing PCO (7). Although there is enhanced correction of the curve in AIS, no differences have been observed in patient reported outcome measures (PROM) (8). PCO is currently used to facilitate correction of AIS with reported enhancement of coronal and axial parameters. There are not any Level 1 studies evaluating the feasibility of PCO in the surgical treatment of AIS.

Aims and hypothesis To compare postoperative scoliosis, kyphosis, rib hump, hemoglobin and hematocrit decrease, length of hospital stay and complications in patients having PCO or not having PCO during posterior spinal fusion for AIS. The investigators hypothesize that patients with PCO have better correction of scoliosis with similar blood loss and complications.

Methods Study design - A randomized, clinical trial according to CONSORT criteria (9).

Patients - 60 adolescents undergoing posterior spinal fusion with pedicle screw instrumentation for idiopathic scoliosis will be randomized after exposure of the spine for PCO. PCO will be conducted at three adjacent levels at the apex of the curve.