Scoliosis is a 3‑dimensional change to the spine in the coronal, sagittal and axial planes. It causes the bones of the spine to twist or rotate so that the spine curves sideways. Scoliosis curves most commonly occur in the thoracic spine, but can also occur in the lumbar spine. Occasionally, they occur in both the thoracic and lumbar spine.
Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis in children and young people. It is progressive and the exact cause is unknown. Mild to moderate spinal curvature does not cause any health problems but can cause cosmetic concerns. Severe spinal curvature with secondary rib changes can also cause significant pain and lung problems.
Treatment of AIS depends on several factors, including skeletal maturity, location of the spinal curve, speed of curve progression and size of the curve. Conservative treatments for mild to moderate AIS include routine surveillance (spinal imaging to monitor progression) and physical therapy. For severe AIS, interventions include casting or bracing (for curves of more than 25 degrees) or spinal fusion surgery (for curves of more than 40 degrees) with various instrumented metallic fixation techniques and grafting to fuse vertebrae. Minimally invasive growth modulating and fusionless surgical techniques to correct idiopathic scoliosis include vertebral body stapling, vertebral body tethering, magnetically controlled growing rods and sublaminar polyester bands. These are also used for AIS in some people. The aim is to correct the scoliosis, prevent progression, restore balance, and reduce pain and morbidity.
Minimally invasive fusionless posterior-approach surgery to correct idiopathic scoliosis is intended to treat AIS in selected people aged 8 years to 17 years whose bones have not fully matured. It is mainly used to correct flexible single curves (a thoracic major curve, or a thoracolumbar or lumbar major curve) with a Cobb angle of up to 60 degrees that reduces to 30 degrees or less on lateral side-bending radiographs, and thoracic kyphosis of less than 55 degrees (as measured from T5 to T12).
The procedure is done under general anaesthesia and fluoroscopic guidance using a posterior unilateral approach. The concave side of the spinal curve is exposed through an incision around the apex of the curve. Two pedicle screws are inserted into the vertebral bodies through the pedicle above and below the apex of the spinal curvature to serve as anchor points. A ratchet rod with an extender and 2 polyaxial joints (that allow a degree of spinal motion) is then fixed to the spine with pedicle screws that are implanted around the apex of the curve. Distraction during surgery is applied with a manual instrument to expand the rod and to straighten the spine. After the procedure, people are allowed to weight bear during everyday activities.
About 2 to 3 weeks after surgery, people are advised to exercise daily. This is to allow the rod additional unilateral elongation so there may be further gradual straightening of the spine while the person continues to grow. Because the procedure does not involve any spinal fusion, spinal motion is preserved. This minimises length of hospital stay and recovery time.