General Session: MIS-1
Presented by: P. Nunley - View Audio/Video Presentation (Members Only)
K. Than(1), P. Park(2), K-M. Fu(3), S. Nguyen(4), M. Wang(5), C. Shaffrey(6), S. Bess(7), B. Akbarnia(4), V. Deviren(1), J. Uribe(8), D. Okonkwo(9), G. Mundis(4,10), P. Mummaneni(1), P. Nunley(1), International Spine Study Group
(1) University of California, San Francisco, San Francisco, CA, United States
(2) University of Michigan, Ann Arbor, MI, United States
(3) Weill Cornell, New York, NY, United States
(4) San Diego Center for Spinal Disorders, San Diego, CA, United States
(5) University of Miami, Miami, FL, United States
(6) University of Virginia, Charlottesville, VA, United States
(7) Rocky Mountain Orthopaedics, Denver, CO, United States
(8) University of South Florida, Tampa, FL, United States
(9) University of Pittsburgh Medical Center, Pittsburgh, PA, United States
(10) Scripps Clinic, La Jolla, CA, United States
Hypothesis: Patients with the best clinical outcomes after circumferential MIS (cMIS) deformity surgery have postoperative SVA < 5 cm and PI-LL matched within 10°, whereas those who do the worst have continued PI-LL mismatch and sagittal imbalance regardless of decompression of their stenosis. Design: Multi-center retrospective review of MIS deformity cases.
Introduction: MIS deformity techniques have limited ability to restore sagittal balance and match the PI-LL. However, MIS techniques are effective for decompression and limit tissue disruption. This study compares best vs. worst outcomes after MIS surgery to identify variables that predispose postoperative success.
Methods: Retrospective study of a multi-center database with adult spinal deformity (Cobb>20°, SVA>5cm, PT>20, PI-LL>10, or Thoracic Kyphosis >60°) patients treated with cMIS. Radiographic and clinical outcomes were compared between “Best” and “Worst” patients. Best was defined as the top 20% improvement in ODI at 2 years from baseline, and Worst was defined as bottom 20%.
Results: 426 patients were identified, 104 patients were included with 2 year data.. There were no significant differences in age, BMI, pre- and postop Cobb angle, PT, PI, levels fused, O.R. time, and blood loss between the Best and Worst Groups. However, the preop ODI was significantly worse at baseline in the group that had the greatest change in ODI. There was no difference in preop PI-LL mismatch (12.8° Best vs. 19.5° Worst, p=0.298). Compared to patients who did Worst, patients who did Best after MIS fusion had lower postop SVA (3.4 cm Best vs. 6.9 cm Worst, p=0.043) and had matched PI-LL (10° Best vs. 19° Worst, p=0.027). The Best Group also had better postop VAS back and leg pain scores (p< 0.05).
Conclusions: MIS deformity surgeons should focus on correcting a patient's PI-LL mismatch to within 10° and restoring SVA < 5cm. Restoration of these parameters seems to impact which patients will achieve the greatest degree of improvement in ODI outcomes, while patients who do worst are not appropriately corrected (fused into a fixed deformity), and were significantly worse clinically at postop.