Compensatory thoracic curve correction in lumbar anterior vertebral body tether (VBT) versus lumbar posterior spinal fusion (PSF)

Purpose: Anterior vertebral body tethering (VBT) is a non-fusion surgical option for skeletally immature patients with idiopathic scoliosis. Prior studies demonstrated compensatory correction of the thoracic curve after lumbar posterior spinal fusion (PSF); however, no studies have examined thoracic curve correction after lumbar VBT.

Methods: Patients with Lenke 5 + 6 lumbar scoliosis who underwent VBT and at least 2 years' follow-up were compared to matched lumbar PSF patients. Groups were compared for major lumbar (L) and compensatory thoracic (T) curve correction, coronal/sagittal balance, and complications.

Results: 24 AVBT and 24 PSF patients were matched 1:1 for skeletal maturity and curve flexibility. There were no significant differences between VBT and PSF for average pre-operative or 2 year post-operative major L or compensatory T curves. Average final L curve correction was 50% VBT and 60% PSF (p = 0.08); average T curve correction was 17% VBT and 20% PSF (p = 0.18). Compared to pre-operative flexibility radiographs, the final post-op thoracic curves were 6° (VBT) and 5° (PSF) larger. PSF had better coronal balance by average of 17 mm (p < 0.0001). There were seven (24%) reoperations in the VBT group: two overcorrections relaxed, two T adding-on (extended to T by PSF-1, VBT-1), one broken tether converted to PSF. There was one (4%) reoperation in the PSF group (10-year post-op extension).

Conclusion: Compensatory thoracic correction was achieved to a similar degree for lumbar VBT and PSF patients. There was little change in thoracic curve magnitude over time, and, on average, the correction did not reach the pre-operative flexibility curve measurement. There was better coronal balance by PSF, and a higher rate of re-operation in VBT patients.

Level of evidence: III.