Comparison of 3-Dimensional Correction and Clinical Outcomes of Lenke 1A Curves with the Stable Vertebra (SV) or SV-1 Selected as the Lowest Instrumented Vertebra.

Backgroud: Lowest instrumented vertebra (LIV) selection is controversial in Lenke 1A curves. Alignment of the LIV in coronal, sagittal, and transverse planes is important for correction of overall scoliosis, as well as the alignment of uninstrumented lumbar curve. In this study, we aimed to evaluate the 3-dimensional correction and clinical outcomes of Lenke 1A curves, corrected with rod derotation (RD) maneuver, according to the LIV level.

Methods: Prospectively collected data of 46 consecutive idiopathic scoliosis surgery patients with Lenke 1A scoliosis who had been treated with posterior instrumentation and fusion were retrospectively evaluated. Patients were divided into 2 groups according to the LIV level: stable vertebra (SV) group (25 patients) and 1 level proximal to SV (SV-1) group (21 patients). Patients were compared pre- and postoperatively according to radiographic and clinical outcomes. Measured parameters in coronal plane were Cobb angle of thoracic curve, shoulder balance, coronal balance, LIV translation, and LIV tilt; in sagittal plane, thoracic kyphosis, lumbar lordosis, sagittal balance, and distal junctional angle. Transverse plane analysis included rotational measurement of apical vertebra (AV), LIV, and LIV+1 with computerized tomography. Clinical outcomes were evaluated with Scoliosis Research Society (SRS)-22 questionnaire. Surgical times were noted.

Results: There were no statistically significant differences between the 2 groups in terms of preoperative radiographic values. In both groups, Cobb angle of thoracic curve, shoulder balance, LIV translation, and LIV tilt improved significantly after the surgery. Postoperatively, AV rotation decreased in both groups significantly. No significant change was observed in rotations of LIV and LIV+1 after the surgery. Clinical outcomes and surgical times were similar between the groups.

Conclusions: Selection of the LIV as SV or SV-1 in Lenke 1A patients led to similar results in terms of coronal and sagittal plane reconstruction, as well as AV and LIV rotation. With RD maneuver, an acceptable amount of rotation could be achieved at LIV and LIV+1. Radiologic and functional outcomes were satisfactory in both LIV levels. To save 1 more mobile segment, it seems reasonable to select SV-1 as the LIV if possible in order to obtain a well-aligned LIV in all 3 planes.