Segmental range-of-motion by vertebral level in fused and unfused patients with adolescent idiopathic scoliosis: a systematic review of the literature.

Purpose: This study aims to understand global and segmental spinal ROM in surgical and nonsurgical AIS patients.

Methods: This systematic review examined segmental vertebral ROM in AIS patients using PubMed, SPORTDiscus, MEDLINE, and Web of Science until October 8th, 2023. Inclusion criteria were articles on segmental motion in AIS patients, both operative and non-operative, under 18 years old.

Results: Seventeen articles met eligibility criteria from 2511 initially retrieved. All patients (n = 996) had AIS (549 non-operative; 447 were operative), with a frequency-weighted mean age of 15.1 ± 1.6 years and a baseline Cobb angle of 51.4 ± 13.3 degrees. Studies showed heterogenous segmental flexibility in the unfused spine, with the apical curve and upper thoracic segments being more rigid and lower segments more flexible at -5 disk segments from the apex. Most studies showed a predictable loss of motion in fused spinal regions postoperatively and a variable loss of global motion depending on the LIV and number of fused segments. A 7° global loss of total trunk flexion per level was observed with increasingly caudal LIV, starting at L1. Anterior vertebral body tethering (AVBT) preserved motion post-surgery but reduced coronal plane motion. AVBT saw less motion loss compared to posterior spinal fusion (PSF) but had higher revision and complication rates.

Conclusion: Preservation of spinal segments correlated with improved motion postoperatively. Increasing caudal LIV in PSF showed sagittal flexion loss. AVBT preserved more sagittal ROM than PSF but increased coronal motion loss, complications, and revision rates, with the largest benefit at LIV L4. Data on segmental motion are limited and further research on postoperative segmental ROM is required.