Cobb-1 versus cobb-to-cobb anterior fusion for adolescent idiopathic scoliosis Lenke 5C curves: a radiological comparative study

Anterior fusion is a well-established procedure for the treatment of Lenke 5C adolescent idiopathic scoliosis (AIS). This retrospective study aimed to assess preoperative and postoperative radiographic differences between the conventional anterior fusion and anterior short fusions (ASF) in Lenke 5C AIS.

Radiographic data of 42 consecutive cases of Lenke 5C AIS, which were surgically treated through anterior segmental fusion, were analyzed retrospectively. Patients have been divided into two groups: C group (n = 19) treated by the conventional fusion from the proximal end vertebra to the distal end vertebra of the main curve and C-1 group (n = 23) treated by ASF, sparing the lowest end vertebra of the main curve. Cobb angles of main curve, apical vertebra tilt, C7 coronal tilt, lowest instrumented vertebra angle (LIV angle), LIV adjacent level disc angulation (LIVDA), and the first uninstrumented vertebra angle (FUV angle) were measured on anteroposterior radiographs of the entire spine. LIVDA, FUV wedging, and rotation were measured on stretch films. C7 sagittal tilt, lumbar lordosis, thoracic kyphosis, and proximal kyphosis junction were measured on lateral radiographs of the entire spine. Repeated-measures analysis of variance and fisher test were used for the statistical analysis.

The preoperative main curve was 39.9 ± 9.1° in the C group vs. (versus) 42.8 ± 11.8° in the C-1 group. At a mean follow-up of 26.2 months (range 10.5–66.3 months), postoperative main curve improved of 75.8 ± 21.2 % (10.4 ± 9.2°, p < 0.001) in the C group and of 52.7 ± 18.7 % (20.1 ± 8.1°, p < 0.001) in the C-1 group. All parameters improved except the LIVDA, which was slightly impaired, especially in the C-1 group with 5.6 ± 4.2° vs. 4.4 ± 2.2° in the C group. On stretch films, FUV rotation was the only parameter to differ; it was graded at 1 ± 0.7 in the C-1 group vs. 0.6 ± 0.5 in the C group (p = 0.04). No disk obliquity just under the future instrumentation and equivalent FUV wedging were found in any of the two groups.

The conventional anterior fusion and ASF give equivalent correction in Lenke 5C AIS, but ASF seems to induce adding-on of the disk below the LIV. FUV rotation on stretch films does not seem to be a predictive factor of postoperative radiological outcome.