Can a Minimal Clinically Important Difference Be Achieved in Elderly Patients with Adult Spinal Deformity Who Undergo Minimally Invasive Spinal Surgery?

BACKGROUND: Older age has been considered a relative contraindication to complex spinal procedures. Minimally invasive surgery (MIS) techniques to treat patients with adult spinal deformity (ASD) have emerged with the potential benefit of decreased approach-related morbidity. OBJECTIVE: To determine whether a minimal clinically important difference (MCID) could be achieved in patients ages >= 65 years with ASD who underwent MIS. METHODS: Multicenter database of patients who underwent MIS for ASD was queried. Outcome metrics assessed were Oswestry Disability Index (ODI) and visual analog scale (VAS) scores for back and leg pain. On the basis of published reports, MCID was defined as a positive change of 12.8 ODI, 1.2 VAS back pain, and 1.6 VAS leg pain. RESULTS: Forty-two patients were identified. Mean age was 70.3 years; 31 (73.8%) were women. Preoperatively, mean coronal curve, pelvic tilt, pelvic incidence to lumbar lordosis mismatch, and sagittal vertical axis were 35 degrees, 24.6 degrees, 14.2 degrees, and 4.7 cm, respectively. Postoperatively, mean coronal curve, pelvic tilt, pelvic incidence to lumbar lordosis, and sagittal vertical axis were 18 degrees, 25.4 degrees, 11.9 degrees, and 4.9 cm, respectively. A mean of 5.0 levels was treated posteriorly, and a mean of 4.0 interbody fusions was performed. Mean ODI improved from 47.1 to 25.1. Mean VAS back and leg pain scores improved from 6.8 and 5.9 to 2.7 and 2.7, respectively. Mean follow-up was 32.1 months. For ODI, 64.3% of patients achieved MCID. For VAS back and leg pain, 82.9% and 72.2%, respectively, reached MCID. CONCLUSIONS: MCID represents the threshold at which patients feel a meaningful clinical improvement has occurred. Our study results suggest that the majority of elderly patients with modest ASD can achieve MCID with MIS.