Horizontalization of UIV as a factor predicting the progression of distal coronal S-type scoliosis after upper thoracic hemivertebra resection and short fusion

English Keywords:Hemivertebra  Upper thoracic  Coronal caudal curve progression

English Abstract:

  【Abstract】 Objectives: To analyze the incidence, characteristics and risk factorsof postoperative coronal S-type scoliosis progression after upper thoracic hemivertebra resection and short fusion. Methods: Retrospective analysis was made on the clinical and imaging data of 68 patients with upper thoracic hemivertebra treated by posterior hemivertebra resection combined with internal pedicle screw fixation in our hospital from January 2005 to January 2015. There were 42 males and 26 females with a mean age of 4.4±1.1 years (3-6 years). All patients had 5 years follow-up at least. All patients had complete preoperative and postoperative follow-up clinical and imaging data. The patients were divided into two groups: progressive group(PG) and non-progressive group(NPG) according to whether there was S-type scoliosis (≥20°) at the final follow-up and the progression of either caudal thoracic curve(CTC) or caudal lumbar curve(CLC) was ≥20° compared with that of 2 weeks after surgery. Clinical data including gender, age, Risser sign, location of hemivertebra, number of fusion segments, Nash-Moe classification, and mean follow-up time, as well as imaging data such as preoperative and postoperative follow-up visits of local scoliosis cobb angle, distal thoracic curvature cobb angle, distal lumbar curvature cobb angle, trunk shift(TS), upper instrumented vertebra tilt(UIV tilt), lower instrumented vertebra tilt(LIV tilt), LIV/LIV+1 disc angle, T1 tilt, head shift, neck tilt, and radiographic shoulder height(RSH) were compared between the two groups to analyze the influence of UIV leveling on the progression of distal coronal plane deformity after upper thoracic hemivertebra resection and short fusion. Results: Of all the patients, the average postoperative correction rate was (74.3±15.3)%, the average loss rate at the end of follow-up was (4.3±2.2)%, and the incidence rate of coronal plane decompensation after surgery was 8.8%(6 casesof S-type scoliosis progression). There were no statistical differences in gender, age, Risser sign, location of hemivertebra, number of fusion segments, presence of apical vertebral rotation, and average follow-up time between the two groups in the first operation(P>0.05). The preoperative coronal imaging parameters such as local scoliosis cobb angle, coronal plane balance, caudal thoracic curve, caudal lumbar curve, T1 tilt, head shift, neck tilt and shoulder height had no statistical differences between the two groups(P>0.05). There were significant differences of the postoperative parameters at each follow-up between the two groups, including: local curve, UIV tilt, and T1 tilt(P<0.05). In the progressive group, UIV and T1 tilt increased gradually from postoperative to the final follow-up, and the differences between two weeks after surgery and five years and the final follow-up were of statistical significance(P<0.05). The curve of the lumbar segment of the patients in the progressive group increased gradually in the six months after surgery and in the follow-up visits, and it′s with statistical difference in comparison of that of the non-progressive group(P<0.05). There were significant differences of CTC between the two groups from 1 year postoperatively to the final follow-up(P<0.05), and CTC was increased from 1 year postoperatively to the final follow-up in progressive group. There were significant differences between the two groups of neck tilt at 5 years postoperatively and the final follow-up(P<0.05), and the neck tilt was increased from 5 years postoperatively to the final follow-up in progressive group. There was no significant difference between the two groups of postoperative TS, LIV tilt, LIV disc angle, head shift and RSH(P>0.05). Conclusions: Insufficient horizontalization of UIV according to incomplete upper thoracic hemivertebra resection could be a predicting factor of postoperative caudal coronal S curve progression.