The influence of isolated thoracoplasty on the evolution of pulmonary function after treatment of severe thoracic scoliosis

Introduction and purpose Isolated thoracoplasty (iTP) on the convex side is performed long time after scoliosis surgery has been performed. ITP is thought to cause a further decline in pulmonary function (PF); however, the amount of decline is ill defined. The objectives of this study were to examine the influence of iTP on the postoperative evolution of PF and rib hump reduction in patients that previously undergone scoliosis surgery. Methods Over an 11-year period, 75 patients underwent iTP. The authors performed a retrospective case series review. Patients with data from PF tests performed preoperatively and at the last follow-up were included. Minimum follow-up was 12 months. The PF value reported was predicted FVC (FVC%). According to the American Thoracic Society, pulmonary impairment was classified as no impairment (FVC: > 80-100%), mild (FVC: > 65 <= 80%), moderate (FVC: > 50 <= 65), and severe (FVC <= 50%). The outcome was studied using validated measures (SRS-24 score, COMI, and the COPD Assessment Test (CAT)). The CAT is stratified into mild impairment (< 10 pts), moderate impairment (10-20 pts), severe impairment (> 20-30 pts), and disabled (> 30 pts). Results Twenty-six patients fulfilled the inclusion criteria. The patients' average age was 28 years at surgery with iTP, and 22 were females; the average BMI was 23, and the average follow-up was 76 months. Twenty of the patients had AIS, and six had congenital scoliosis. The time between scoliosis correction and iTP averaged 39 months. The mean number of resected rib segments was 7, and the mean blood loss was 834 ml. FVC% was 66% preoperatively and 57% at follow-up, with a significant change of 9% (p < .02). Fourteen patients had a FVC% change between preoperation and follow-up that was >= 5%; this change was not dependent on the preoperative FVC%. PF showed a slight but non-significant improvement with longer follow-up. At the time of iTP, the thoracic curve averaged 67A degrees, and thoracic kyphosis averaged 46A degrees. Rib hump height was 34 mm before iTP and 15 mm at follow-up (p < .03). At follow-up, the SRS-24 score was 81, the COMI score was 4 points, and the CAT score was 8 points. Eight patients had a CAT > 10. Two patients had a major complication. A comparison of patients with pulmonary impairment preoperation vs. follow-up found 4 vs. 1 patients had no PF impairment, 8 vs. 4 patients had mild impairment, 10 vs. 13 patients had moderate impairment, and 4 vs. 8 patients had severe impairment. Conclusions Isolated TP was shown an effective technique for rib hump resection. Six years after iTP, the FVC% declined by an average of 9%. Several patients had long-lasting effects in terms of %FVC decline. iTP should be reserved for patients with significant rib hump deformity.