Treatment of the Fractional Curve with Circumferential Minimally Invasive (cMIS) Interbody versus Open Surgery without Interbody Fusion: An Analysis of Surgical Outcomes

Presented at SMISS Annual Forum 2016
By Dean Chou MD
With Behrooz Akbarnia MD, Juan Uribe MD, FACS, Neel Anand MD, Vedat Deviren MD, Robert Eastlack MD, Michael Wang MD, Praveen Mummaneni MD, David O Okonkwo , Paul Park MD, International Group , Gregory Mundis MD, Joseph Zavatsky MD, Pierce Nunley MD, Stacie Nguyen MPH,

Disclosures: Dean Chou MD None Behrooz Akbarnia MD A; Depuy Synthes Spine. B; NuVasive, K2M, Ellipse, Kspine. D; Alphatec Spine, NuVasive, Ellipse, Kspine, Nocimed., Juan Uribe MD, FACS A; Nuvasive. B; Nuvasive. C; Nuvasive. D; Nuvasive. F; Nuvasive, Neel Anand MD None, Vedat Deviren MD A; AOSpine, Globus, Nuvasive. B; Nuvasive. F; Nuvasive., Robert Eastlack MD None, Michael Wang MD None, Praveen Mummaneni MD B; Globus, David O Okonkwo None, Paul Park MD B; Biomet, Globus, Medtronic, Nuvasive. F; Globus, International Group A; Biomet, Depuy, Innovasis, K2M, Medtronic, Nuvasive, Stryker., Gregory Mundis MD A; ISSGF, Nuvasive. B; K2M, Medicrea, Misonix, Nuvasive. C; K2M, Nuvasive. F; Nuvasive., Joseph Zavatsky MD B; Amendia, Biomet, Depuy, Stryker. D; Innovative Surgical Solutions, Safe Wire, Vivex. F; Biomet., Pierce Nunley MD None, Stacie Nguyen MPH None,

University of California, San Francisco, San Francisco, CA1; Louisiana Spine Institute, Shreveport, LA2; Spine & Scoliosis Specialist, Tampa, FL3; Scripps Clinic, La Jolla, CA4; University of Pittsburgh Medical Center, Pittsburgh, PA5; University of Miami, Miami, FL6; University of Michigan, Ann Arbor, MI7; University of South Florida, Tampa, FL8; Cedars Sinai, Los Angeles, CA9; San Diego Spine Foundation, San Diego, CA10; San Diego Center for Spinal Disorders, La Jolla, CA11; San Diego Spine Foundation & Scripps Clinic, San DIego, CA12; and International Spine Study Group Foundation, Brighton, CO13


The fractional curve of adult spinal deformity (ASD) can be difficult to treat. We sought to evaluate the outcomes of patients whose fractional curves were treated with either cMIS or open techniques without interbody (IB). 


To determine if there is a difference in surgical outcomes in treating the fractional curve with cMIS or open techniques.


Retrospective review of 2 multicenter ASD databases (Open- prospective; MIS- retrospective), with the following inclusion criteria: age>18 years with fractional curves >10, ≥ 3 levels of instrumentation, and one of the following: coronal Cobb angle (CCA)>20, PI-LL>10, PT>20, SVA >5cm. Fractional curve was measured from S1 and the last vertebrae of the lower Cobb. Only fractional curves of 10 degrees or greater were evaluated. In the OPEN cohort, only patients without IB were included. 


888 patients met inclusion criteria for the database, of which 508 had complete 2- year data. 118 patients had their fractional curves treated, and after propensity matching for levels treated, 40 patients were eligible with either cMIS (20) or with open (20) surgery. Preop fractional curve was 18 in both groups and corrected to 6.9 in cMIS and 8.5 in open (p>0.05). cMIS patients had a smaller postop coronal Cobb (12.5 vs 24.3;p=0.02) and lower EBL (809cc vs 2299cc;p=0.002). Open patients had a higher SVA change (-1.96 vs +1.32 cm; p=0.036), more pelvic fixation (55% vs 15%;p=0.008), Both groups had similar pre and postop VAS leg pain with no difference between groups at 2 years (change VAS Leg -4.4 vs -2.2;p=0.06). There was no significant difference in change of Cobb angle, ODI, PI-LL, LL, or VAS Back. 


Treating fractional curves with cMIS surgery improved leg pain and comparable correction to the open group, and when matched for levels treated, the outcomes remained similar.