Application of cone-beam CT mosaic imaging combined with I-shaped measurement instrument in assessing the coronal balance during corrective surgery for adolescent idiopathic scoliosis

English Keywords:Adolescent idiopathic scoliosis  Posterior orthopedic  Coronal balance  Cone-beam CT  Mosaic full-spine X-ray

English Abstract:

  【Abstract】 Objectives: To investigate the values of cone-beam CT(CBCT) mosaic imaging combined with I-shaped measurement instrument in assessing coronal balance during the correction surgery for patients with adolescent idiopathic scoliosis(AIS). Methods: Clinical data of 48 AIS patients treated with posterior spinal correction surgery and assessed for coronal balance by CBCT mosaic imaging an I-shaped measurement instrument in the General Hospital of Northern Theater Command from January 2019 to January 2021 were retrospectively analyzed. The patients aged 14.9±1.8(12-18) years and were followed up for 1.8±0.2(1-2) years. They were classified based on the conditions of coronal balance as follows: Type A, coronal balance distance(CBD)<20mm; Type B, CBD≥20mm and C7 plumb line(C7PL) shifted to the concave side of the main curve; Type C, CBD≥20mm and C7PL shifted to the convex side of the main curve. CBD≥20mm was defined as coronal imbalance. The main curve Cobb angle, CBD and pelvic coronal obliquity angle(PCOA) before and during surgery, at 1 week after the surgery and the last follow-up visit were recorded. In addition, visual analogue scale(VAS) scores and Oswestry disability index(ODI) before operation and at the last follow-up were recorded. Parameters reflecting the coronal balance and clinical orthopedic effect at each time point were compared. Results: The main curve Cobb angles of 48 AIS patients before operation, during operation, at 1 week after operation and the last follow-up were 58.45°±12.81°, 14.13°±5.86°, 14.48°±5.98° and 14.39°±5.74°, respectively, which were significantly reduced during operation and at 1 week after operation compared with that before surgery(P<0.05), and which were not significantly different between postoperative 1 week and the last follow-up(P>0.05). The PCOAs before operation, during operation, at 1 week after surgery and the last follow-up were 3.72°±2.75°, 1.25°±0.97°, 1.25°±0.96° and 1.28°±0.96°, respectively. A significant difference was detected in intraoperative PCOA and postoperative PCOA(P<0.05); While no significant difference was detected between the PCOA at 1 week after surgery and the last follow-up visit(P>0.05). The coronal imbalance rate was 47.91%(23/48) before operation and 10.42%(5/48) at final follow-up. The CBDs of the type A 25 patients before surgery, during surgery, at 1 week after surgery and the last follow-up were 12.53±4.46mm, 8.06±3.15mm, 8.37±3.13mm and 8.66±3.77mm, respectively. The intraoperative and postoperative 1 week CBDs were significantly reduced compared with before surgery(P<0.05), and no significant difference was found between those of postoperative 1 week and the last follow-up(P>0.05). The CBDs of type B 15 patients before surgery, during surgery, at 1 week after surgery and the last follow-up were 24.57±4.60mm, 14.91±4.62mm, 14.95±4.49mm and 15.06±3.98mm, which in type C 8 patients were 26.46±6.78mm, 16.58±4.00mm, 16.94±4.12mm and 16.58±3.97mm, respectively. CBDs during surgery and at 1 week after surgery in both type B and C patients were significantly reduced compared with those before the surgery(P<0.05), and no significant difference was detected between those at 1 week after surgery and the last follow-up(P>0.05). VAS score(3.98±0.57 vs. 7.68±0.64) and ODI[(21.82±3.12)% vs. (46.51±4.79)%] at the last follow-up were significantly improved than preoperative ones(P<0.05). Conclusions: The CBCT mosaic imaging combined with I-shaped measurement instrument can be an effective and powerful tool to assess the coronal balance intraoperatively, which can assist spinal surgeons to assess the coronal balance conditions during the corrective surgery for scoliosis in AIS patients, and to timely adjust the correction degree and therefore effectively reduce the incidence of postoperative coronal imbalance.