Risk factors analysis of coronal imbalance after posterior correction of congenital lumbosacral deformity with long segmental fixation

English Keywords:Lumbosacral deformity  Congenital  Long segmental fixation  Coronal imbalance

English Abstract:

  【Abstract】 Objectives: To analyze the clinical feature, risk factors and preventions of coronal imbalance after posterior correction of congenital lumbosacral deformity with long segmental fixation. Methods: 23 patients with congenital lumbosacral deformity received osteotomy and long segmental pedicle screw fixation and correction via posterior approach alone between May 2007 to May 2017 in our hospital were analyzed. There were 6 males and 17 females with an average age 13.2±2.8 years old, and the average follow-up was 38.2±8.4 months. Deformity segments, type, fusion segments, the simplified Chinese version of SRS-22 questionnaire, imaging parameters of AP film of standing full spine X ray, bending X ray and lower extremity weight-bearing full-length X ray were collected. The main Cobb angle, cranial curve Cobb angle, bending Cobb angle, sacral obliquity, clavicle angle, coronal balance distance, double total length lower extremities were measured. All patients were categorized into coronal balance group and imbalance group according to the diagnosis criteria of coronal imbalance which was defined as the distance from C7PL to CSVL more than 2cm. Results: The average fusion segments were 7.4±2.3. The average pre-operative main curve Cobb angle was 40.25°±10.6° and corrected to 12.4°±5.2° at final follow-up. The correction rate was (69.1±8.7)%. The average pre-operative compensatory cranial curve Cobb angle was 35.5°±8.5° before surgery and corrected to 13.1°±5.0° at final follow-up, the correction rate was (63.1±7.9)%. 5 cases including 2 boys and 3 girls occurred postoperative coronal imbalance(21.7%) during follow-up. The pathological classification included L5 hemivertebra in 2 cases, S1 hemivertebra in 1 case, L5 wedge vertebra in 1 case and L5 hypertrophy transverse in 1 case, respectively. In imbalance group, 2 cases had pedicle screw breakages at S1, 1 of the 2 cases received revision operation, the other accepted brace therapy. There were significant differences between the two groups in cranial curve FSC, pre-operative trunk shift, UIV position, LIV position, final follow-up CBD(1.0±0.8cm vs 3.0±0.7cm), post-operative clavicle angle(3.5°±3.2° vs 15.2°±14.2°), final follow-up clavicle angle(3.6°±3.6° vs 15.0°±13.3°), and final follow-up self-image domain(3.9±0.6 vs 3.7±0.7), final follow-up treatment satisfaction domain(4.5±0.2 vs 2.6±0.6), final follow-up mental domain(4.1±0.4 vs 3.2±0.5), total score(15.1±2.8 vs 17.8±2.2) in SRS-22. There were no significance differences between two groups in gender(4/14 vs 2/3), average age(12.6±3.8 vs 14.2±2.6), fusion segments(8.3±3.7 vs 6.8±1.9), pre-operative main Cobb angle(35.2°±17.1° vs 37.6°±4.6°), post-operative main Cobb angle(12.6°±5.6° vs 16.6°±5.9°), final follow-up Cobb angle(12.0°±6.2° vs 16.4°±5.9°), pre-operative cranial curve Cobb angle(37.3°±10.7° vs 38.4°±5.4°), post-operative cranial curve Cobb angle(15.5°±4.6° vs 12.0°±7.5°), final follow-up cranial curve Cobb angle(14.1°±5.0° vs 12.6°±7.5°), pre-operative CBD(2.1±2.7 vs 2.9±1.9), post-operative CBD(0.9±1.2 vs 1.7±1.1), pre-operative clavicle angle(2.0±0.9 vs 1.2±1.1), post-operative clavicle angle(1.5±1.2 vs 2.6±2.4), pre-operative sacral obliquity angle(1.1±1.0 vs 4.0±2.5), and pre-operative fuction domain(4.1±0.5 vs 3.9±0.6), pre-operative pain domain(3.4±0.4 vs 3.8±0.4), pre-operative self-image domain(3.4±0.7 vs 3.2±0.7), pre-operative mental(3.5±0.3 vs 3.6±0.7), final follow-up fuction domain(3.9±0.5 vs 3.8±0.5), final follow-up pain domain(3.9±0.4 vs 3.7±0.9) in SRS-22 between the two groups in univariable test(P>0.05). Conclusions: Patients with congenital lumbosacral deformity receiving long segmental fixation has optimistic deformity correction. Coronal imbalance after sugery can negatively affect life quality. The risk factors could be incomplete osteotomy, improper orthopedic strategy and inappropriate segments selection.