Does Symmetric Thoracic Fusion Make a Difference in Lenke 1 A/B AIS Patients?

Abstract

Study Design. A retrospective study. Objective. The aim of this study was to compare the long-term outcomes of correction surgery for Lenke 1 A/B scoliosis among those with symmetric fusion (SF), upper-dominant fusion (UF), and lower-dominant fusion (LF) in adolescent idiopathic scoliosis (AIS). Summary of Background Data. Symmetric fusion, defined as equal number of vertebral levels included in instrumented fusion above and below the apical vertebra or disc of the primary curve, was a new concept raised in AIS selective fusion. Previous study showed that similar correction the effect on clinical outcomes of this fusion style. Methods. Preoperative, postoperative, and last follow-up radiographs of 117 consecutive patients with Lenke type 1A/B curves who underwent posterior selective thoracic instrumentation surgery were analyzed. Patients were divided into two groups (SF and nonsymmetric fusion [NSF]). Patients in NSF was further divided into two groups UF (more vertebrate was fused above the apex) and LF (more vertebrate was fused below the apex). Clinical outcomes and coronal decompensation including adding-on and trunk shift were analyzed and compared among three groups. Results. There was no significant difference between SF and NSF in magnitude of preoperative main thoracic curve (P = 0.69) and correction rate (P = 0.50). Distal adding-on was observed in 21 patients (17.9%), and coronal decompensation was observed in eight patients (6.8%) in all at final follow up. No significant differences were found between the two groups regarding adding-on phenomenon (P = 0.64) and coronal imbalance (P = 0.72). Significantly higher rates of adding-on were found in UF compared with SF and LF (P < 0.001). In a subgroup analysis between UF and LF in NSF patients, significant differences were found between two subgroups in the rate of trunk shift (P = 0.038). No significant differences in SRS-22 scores were observed among the three groups. Conclusion. In Lenke 1A/B AIS with posterior selective fusion, SF provides no significant differences from NSF. However, in NSF, UF was found to be high risky of adding-on phenomenon. Level of Evidence: 3

Can We Stop Distally at LSTV-1 for Adolescent Idiopathic Scoliosis With Lenke 1A/2A Curves?

“…Our previous study compared the long-term outcome of correction surgery for Lenke 1 A/B AIS among those with symmetric fusion (SF), upper-dominant fusion (UF: more vertebrae was fused above the apex), and lower dominant fusion (LF: more vertebrae was fused below the apex). 16 Significant higher incidence of adding-on was found in UF compared to SF and LF. Our current finding was consistent with previous study.…”

“…Hence, long thoracic curve with low apex location was a risk factor for distal adding-on when stopping distally at LSTV-1. Our previous study compared the long-term outcome of correction surgery for Lenke 1 A/B AIS among those with symmetric fusion (SF), upper-dominant fusion (UF: more vertebrae was fused above the apex), and lower dominant fusion (LF: more vertebrae was fused below the apex) 16 . Significant higher incidence of adding-on was found in UF compared to SF and LF.…”

“…Trunk shift was measured by the distance between vertical trunk reference line (VTRL) and CSVL 15 . We evaluated the symmetric thoracic fusion by calculating the relative positions of distances between LIV and apical vertebrae (LIV-AV) and distances between upper instrumented vertebra and apical vertebrae (UIV-AV), UIV indicated the upper instrumented vertebra 16 . The LSTV was defined as the most distal thoracic or lumbar vertebra within the main curve in which the CSVL touched the lateral border of the pedicle outline or was medial to the pedicle.…”

Coronal imbalance after growing rod treatment in early-onset scoliosis: a minimum of 5 years’ follow-up

“…The current study defined 2 cm as the threshold value of CI, which was based on the work of Zhao et al 26 and Hwang et al 27 The incidence of postoperative CI among patients with EOS (18%) was similar to that of young adolescent patients (range 9.1%-20.8%), [7][8][9][10] but slightly lower than those of patients with degenerative lumbar scoliosis (range 25.6%-31.6%). [3][4][5][6] Concerning the effect of definitive spinal fusion on CI during distraction periods, the current study noted that patients with CI showed only a small improvement in coronal balance and continued to be diagnosed with this complication at the latest follow-up.…”