Is Circumferential Minimally Invasive Surgery Effective in the Treatment of Moderate Adult Idiopathic Scoliosis?

BACKGROUND Outcomes for minimally invasive scoliosis correction surgery have been reported for mild adult scoliosis. Larger curves historically have been treated with open surgical procedures including facet resections or posterior column osteotomies, which have been associated with high-volume blood loss. Further, minimally invasive techniques have been largely reported in the setting of degenerative scoliosis. QUESTIONS/PURPOSES We describe the effects of circumferential minimally invasive surgery (cMIS) for moderate to severe scoliosis in terms of (1) operative time and blood loss, (2) overall health and disease-specific patient-reported outcomes, (3) deformity correction and fusion rate, and (4) frequency and types of complications. METHODS Between January 2007 and January 2012, we performed 50 cMIS adult idiopathic scoliosis corrections in patients with a Cobb angle of greater than 30° but less than 75° who did not have prior thoracolumbar fusion surgery; this series represented all patients we treated surgically during that time meeting those indications. Our general indications for this approach during that period were increasing back pain unresponsive to nonoperative therapy with cosmetic and radiographic worsening of curves. Surgical times and estimated blood loss were recorded. Functional clinical outcomes including VAS pain score, Oswestry Disability Index (ODI), and SF-36 were recorded preoperatively and postoperatively. Patients' deformity correction was assessed on pre- and postoperative 36-inch (91-cm) standing films and fusion was assessed on CT scan. Minimum followup was 24 months (mean, 48 months; range, 24-77 months). RESULTS Mean blood loss was 613 mL for one-stage surgery and 763 mL for two-stage surgery. Mean operative time was 351 minutes for one-stage surgery and 482 minutes for two-stage surgery. At last followup, mean VAS and ODI scores decreased from 5.7 and 44 preoperatively to 2.9 and 22 (p < 0.001 and 0.03, respectively) and mean SF-36 score increased from 48 preoperatively to 74 (p = 0.026). Mean Cobb angle and sagittal vertical axis decreased from 42° and 51 mm preoperatively to 16° and 27 mm postoperatively (both p < 0.001). An 88% fusion rate was confirmed on CT scan. Perioperative complications occurred in 11 of the 50 patients (22%), with delayed complications needing further surgery in 10 more patients at last followup. CONCLUSIONS cMIS provides for good clinical and radiographic outcomes for moderate (30°-75°) adult idiopathic scoliosis. Patients undergoing cMIS should be carefully selected to avoid fixed, rigid deformities and a preoperative sagittal vertical axis of greater than 10 cm; surgeons should consider alternative techniques in those patients. LEVEL OF EVIDENCE Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.