Thoracic Adolescent Idiopathic Scoliosis Curves Between 70 and 100 Degrees: Is Anterior Release Necessary?

• a, d, e - Medtronic Sofamor Danek

Introduction: Surgical treatment of thoracic adolescent idiopathic scoliosis (AIS) curves between 70 and 100º often consists of anterior and posterior fusion to improve coronal correction and fusion rate with the anterior release and fusion performed through either an open thoracotomy or by video-assisted thoracoscopy (VAT).

Purpose: T urpose: o compare the radiographic and clinical outcome of two surgical treatments: anterior/posterior spinal fusion (APSF) vs. posterior spinal fusion (PSF) alone in patients with large 70 to 100º thoracic AIS curves.

Methods: All patients (n=84) with main thoracic AIS curves between 70 and 100º who underwent spinal fusion (APSF or PSF) at one center between 1987 and 2001 were included for analysis. Minimum follow-up was 2 years postoperatively (mean, 4.5 years; range, 2.0 to 10.2). Mean age of patients was 13.8 years (range, 10.7 to 18.2), with 66 females and 18 males. Multiple radiographic measures were assessed. When available, pulmonary function tests (PFTs), specifically FVC and FEV1 were analyzed. The primary and secondary statistical analyses performed were nonparametric analyses, utilizing the Wilcoxon-Mann-Whitney tests for the primary analysis of APSF and PSF groups. The PSF group analysis was performed with the Kruskal-Wallis test.

Results: There were 22 patients in the APSF (open ASF in 18, and VAT in 4) group and 62 patients in the PSF group. There were no statistically significant differences between the groups for gender, age, number levels fused, data, Cobb measurement of preoperative sagittal or coronal thoracic curve magnitude, or coronal curve flexibility (See Table). The APSF group had greater intraoperative correction of the coronal curve (48.3º vs. 38.7º, p = 0.0087) as well as final overall correction (47.2º vs. 34.2º, p = 0.0008). The APSF group induced less lordosis intraoperatively from T5-T12 (PSF -11.6º vs. APSF -5.4º, p = 0.0265), however at last followup there was no difference in the amount of change in the sagittal alignment from T5-T12 (p = 0.3150). There were no significant differences seen in the PFT data, or the SRS outcomes data between the APSF and PSF only groups (See table). Subanalysis of the PSF only group identified three distinct groups based on implants: hook-only constructs (n = 36), hybrid constructs of hooks and lumbar pedicle screws (n=15), and pedicle screw-only constructs (n=11). Pedicle screw only constructs corrected the coronal Cobb measurements more than the other two groups (47.5 degrees vs. hooks 32.6º vs. hybrid 34.4º, p=0.0110) and when compared to the APSF group there was no statistically significant difference in coronal correction (PSF, 47.5º; APSF 48.3º, p=0.9014), nor any other parameter except for sagittal T5-T12 changes. There were no re-operations for implant failure/pseudarthroses in any of the patients.

Conclusion: APSF of large thoracic curves allows greater coronal correction of thoracic curves between 70 and 100º, when compared to PSF alone utilizing thoracic hook constructs, but not with the use of thoracic pedicle screw constructs. Scoliosis surgeons not using pedicle screw constructs need to decide if the modest improvement in coronal correction with a combined approach justifies its routine use in this patient population.

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