Spontaneous lumbar curve correction in selective anterior instrumentation and fusion of idiopathic thoracic scoliosis of Lenke type C

Abstract

Background: Posterior pedicle screw instrumented correction and fusion have become the gold standard in the surgical treatment of thoracic scoliosis. However, in thoracic Lenke type C curves selective posterior fusion of the thoracic curve may lead to spinal imbalance. The aim of the study was to analyse the radiological results of selective anterior thoracic fusion using a standard open dual rod technique with special respect to spontaneous lumbar curve correction (SLCC).

Methods: Twenty-eight patients (26 patients with Lenke 1C and 2 patients with Lenke 2C curves) with an average age of 15 years were surgically treated with an anterior dual rod system through a standard open double thoracotomy approach. Average clinical and radiological follow-up was 4 years (24-84 months).

Results: Fusion was carried out mostly from end-to-end vertebra. The primary curve was corrected from 61.6° (average correction on reverse bending films 42.9 %) to 27.1° (56.0 % correction) with an average loss of correction of 2.2°. The secondary lumbar curve measured 47.7° preoperatively (40-56°, average correction on reverse bending films 66.2 %) and corrected spontaneously to 30.1° (36 % SLCC) and remained stable without any cases of deterioration or decompensation during follow-up. Lumbar apical vertebral translation increased minimally by an average of 4 mm directly, postoperatively, and returned to an average of preoperative values during follow-up. All but two curves remained as type C lumbar modifier at follow-up. Preoperatively, three patients showed a marked coronal imbalance of more than 3 cm (all left, average 4.0 cm); at follow-up, two patients were still out of balance by more than 3 cm (all to the left, average 3.4 cm). Preoperatively, a marked shoulder imbalance of more than 1.0 cm was found in 11 patients; this was corrected in all patients to <1.0 cm at follow-up. The apical vertebral rotation measured according to Perdriolle was corrected from 23.5° to 15.0° in the thoracic spine (36.2 % correction) with an average clinical reduction of the rib hump of 63.2 %. In the lumbar spine, there was no relevant radiological derotation; however, clinically, the lumbar hump corrected spontaneously by 44.3 %. Thoracic kyphosis measured 28.5° preoperatively and 32.3° at follow-up. All six patients with a preoperative hypokyphosis (<20°) of an average of 9.5° were successfully corrected to an average thoracic kyphosis of 23.8° at follow-up. There were no cases of junctional thoracolumbar kyphosis. There were neither reoperations nor implant failures with pseudarthrosis.

Conclusion: Selective anterior correction and fusion in primary thoracic curves with lumbar modifier type Lenke C resulted in a reliable and satisfactory SLCC. Advantages of anterior versus posterior techniques are the true segmental derotation with excellent rib hump correction and a superior restoration of thoracic kyphosis.

Fig. 1

At time of surgery, 15-year-old girl with Lenke 1 CN scoliosis (patient number 17) and a primary thoracic curve of 51° and a lumbar curve of 40° (a, b). Anterior dual rod instrumentation T6–12 with correction of the thoracic curve to 23° and a spontaneous lumbar curve correction to 25° resulting in a balanced spine with a normal sagittal profile (c, d)

Fig. 2

At time of surgery, 15-year-old girl with Lenke 2 CN scoliosis (patient number 3) and a primary thoracic curve of 60° and secondary lumbar curve of 40° (a, b). Anterior dual rod instrumentation T6–12 with correction of the thoracic curve to 23° and a spontaneous lumbar curve correction to 18° resulting in a balanced spine with balanced shoulders and a normal sagittal profile (c, d)

Fig. 3

Preoperative (a, b) and postoperative (c, d) clinical pictures of patient number 17 (Fig. 1) demonstrating the excellent correction of the rib hump deformity due to instrumented derotation (no costoplasty performed)

Fig. 4

Preoperative (a, b) and 3 years follow-up (c, d) clinical pictures of patient number 14 demonstrating the excellent correction of both the rib hump and lumbar hump deformity due to instrumented thoracic and the spontaneous lumbar derotation (no costoplasty performed)