[Comparison of two surgical methods for treatment of idiopathic thoracic scoliosis - anterior versus posterior approaches].

PURPOSE OF THE STUDY: The aim of this retrospective randomised study is a comparison of two surgical approaches (anterior versus posterior) for the treatment of idiopathic thoracic scoliosis by corrective spondylodesis with segmental instrumentation in adolescents aged 13 to 20 years.

MATERIAL AND METHODS: The study included patients with right-sided idiopathic thoracic scoliosis (Cobb's angle, 40°-70°; Lenke type I). The group of patients treated from the posterior approach by fusion and segmental instrumentation, involving the use of a hybrid, tworod system or screws only, comprised 31 girls with an average age of 14.5 years (group 1). In this group three instrumentation systems were used. The patients treated from the anterior approach, which included thoracotomy for disc excision, fusion and segmental instrumentation with a one- or two-rod system, consisted of 25 girls and six boys with an average age of 15.3 years (group 2). In this group four instrumentation systems were employed. In all patients radiographs were evaluated before surgery, immediately after the procedure and then every 12 months. The evaluation also included the operative time, blood loss, length of hospital stay, hospital costs and complications. The random selection was based on casting lots. Some patients indicated for the anterior approach withdrew after receiving detailed information on this procedure and therefore patients operated on from the anterior approach before the study had begun were enrolled. The statistical comparison of the results of anterior and posterior procedures was made using the two-sample t-test or Wilcoxon's test. The Shapiro-Wilk test was used for normality testing and Fisher's F-test for the equality of variances. The paired t-test or non-parametric paired Wilcoxon's test was employed for testing two variables within each group. The level of significance was set at 0.05. RESULTS In group 1, anteroposterior radiographs showed, on the average, 54.3° before surgery, 18.7° immediately after it and 19.1° at one year after surgery. The sagittal profile before surgery was T5 +30.0° T12 -57.7° S1; the surgery resulted in reducing thoracic kyphosis by 9.5° and lumbar lordosis by 14.2°. The average operative time was 245.8 min, intra-operative blood loss was 1095.2 ml and drained blood loss was 636.9 ml. The average hospital stay lasted 10.2 days. In group 2, anteroposterior radiographs had the average values of 53.7° pre-operatively, 23.6° post-operatively and 25.9° at one year after surgery. The pre-operative sagittal profile was T5 +21.5° T12 -54.2° S1 and, post-operatively, thoracic kyphosis increased by 7.0° and lumbar lordosis decreased by 2.2°. The average operative time was 226.8 min, intra-operative and drained blood losses were 1095.2 ml and 636.9 ml, respectively, and length of hospital stay was 15.5 days.. In group 2, the operative time and intra-operative blood loss were lower and post-operative drained blood loss (due to longer duration of chest drainage) was higher than in group 1. All findings were statistically significant. Significant differences between the groups were also found in the costs of implants and hospital stay because, for the posterior approach, they were higher by a total of 68 466 CZK and 52 250 CZK, respectively.

DISCUSSION: In the frontal plane, thoracic kyphosis corrections through either surgical approach are comparable; in the sagittal plane, surgery from the posterior approach results in reducing thoracic kyphosis and that from the anterior approach produces a mild increase in it.

CONCLUSIONS: In terms of surgical treatment selection, the anterior approach is more economical and requires spinal fixation and instrumentation to a lesser extent. However, prolonged chest wound drainage results in a longer hospital stay. The majority of idiopathic scoliosis cases are indicated for a posterior approach. In scoliosis with marked hypo-kyphosis or lordosis, an anterior approach can be considered because it produces an increase in thoracic kyphosis.