A preliminary assessment of intervertebral disc health and pathoanatomy changes observed two years following anterior vertebral body tethering.

Abstract

Vertebral body tethering (VBT) has been reported as a safe and effective non-fusion surgical technique for the treatment of adolescent idiopathic scoliosis, but the postoperative health of the bone and soft tissues of the spine following instrumentation remains unknown. We aimed to evaluate pathoanatomy and degenerative changes of the spine in adolescent idiopathic scoliosis patients both prior to and two years following VBT. We prospectively enrolled nine patients who underwent VBT for the treatment of progressive adolescent idiopathic scoliosis. All patients received preoperative and two-year postoperative magnetic resonance imaging of their spine; images were assessed for pathoanatomy (e.g. nucleus pulposus positioning and muscle atrophy) and degenerative changes (e.g. Schmorl nodes, endplate oedema, disc degeneration, and osteoarthritis) at each vertebral level between T1 and S1. Four patients (44%) exhibited a shift of the nucleus pulposus from an eccentric position at baseline towards midline at three or more levels, most of which were in the tethered region. Tethering did not affect preexisting fatty atrophy of multifidus. No patients exhibited postoperative Schmorl nodes, endplate oedema, or disc degeneration in either the tethered or untethered regions. Four patients (44%) presented with mild facet osteoarthritis in the lower lumbar spine, which did not change postoperatively. One patient developed moderate facet osteoarthritis at L5-S1. These preliminary data indicate that VBT may not result in significant degenerative changes in either the intervertebral discs or the posterior facets two years following instrumentation.