title: Clinical and radiographic parameters associated with best versus worst clinical outcomes in minimally invasive spinal deformity surgery.
abstract: OBJECTIVE Minimally invasive surgery (MIS) techniques are increasingly used to treat adult spinal deformity. However, standard minimally invasive spinal deformity techniques have a more limited ability to restore sagittal balance and match the pelvic incidence-lumbar lordosis (PI-LL) than traditional open surgery. This study sought to compare "best" versus "worst" outcomes of MIS to identify variables that may predispose patients to postoperative success. METHODS A retrospective review of minimally invasive spinal deformity surgery cases was performed to identify parameters in the 20% of patients who had the greatest improvement in Oswestry Disability Index (ODI) scores versus those in the 20% of patients who had the least improvement in ODI scores at 2 years' follow-up. RESULTS One hundred four patients met the inclusion criteria, and the top 20% of patients in terms of ODI improvement at 2 years (best group, 22 patients) were compared with the bottom 20% (worst group, 21 patients). There were no statistically significant differences in age, body mass index, pre- and postoperative Cobb angles, pelvic tilt, pelvic incidence, levels fused, operating room time, and blood loss between the best and worst groups. However, the mean preoperative ODI score was significantly higher (worse disability) at baseline in the group that had the greatest improvement in ODI score (58.2 vs 39.7, p < 0.001). There was no difference in preoperative PI-LL mismatch (12.8° best vs 19.5° worst, p = 0.298). The best group had significantly less postoperative sagittal vertical axis (SVA; 3.4 vs 6.9 cm, p = 0.043) and postoperative PI-LL mismatch (10.4° vs 19.4°, p = 0.027) than the worst group. The best group also had better postoperative visual analog scale back and leg pain scores (p = 0.001 and p = 0.046, respectively). CONCLUSIONS The authors recommend that spinal deformity surgeons using MIS techniques focus on correcting a patient's PI-LL mismatch to within 10° and restoring SVA to < 5 cm. Restoration of these parameters seems to impact which patients will attain the greatest degree of improvement in ODI outcomes, while the spines of patients who do the worst are not appropriately corrected and may be fused into a fixed sagittal plane deformity.
authors.affiliation: Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon;
authors.forename: Khoi D
authors.initials: KD
authors.lastname: Than
authors.affiliation: Department of Neurological Surgery, University of Michigan, Ann Arbor, Michigan;
authors.forename: Paul
authors.initials: P
authors.lastname: Park
authors.affiliation: Weill Cornell Brain and Spine Center, New York, New York;
authors.forename: Kai-Ming
authors.initials: KM
authors.lastname: Fu
authors.affiliation: San Diego Center for Spinal Disorders, La Jolla, California;
authors.forename: Stacie
authors.initials: S
authors.lastname: Nguyen
authors.affiliation: University of Miami Spine Institute, Miami, Florida;
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Wang
authors.affiliation: Department of Neurological Surgery and.
authors.forename: Dean
authors.initials: D
authors.lastname: Chou
authors.affiliation: Spine Institute of Louisiana, Shreveport, Louisiana;
authors.forename: Pierce D
authors.initials: PD
authors.lastname: Nunley
authors.affiliation: Orthopedic Spine Surgery, Cedars-Sinai, Los Angeles, California;
authors.forename: Neel
authors.initials: N
authors.lastname: Anand
authors.affiliation: Department of Neurological Surgery, Rush University Medical Center, Chicago, Illinois;
authors.forename: Richard G
authors.initials: RG
authors.lastname: Fessler
authors.affiliation: Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia;
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.affiliation: Rocky Mountain Scoliosis & Spine, Denver, Colorado;
authors.forename: Shay
authors.initials: S
authors.lastname: Bess
authors.affiliation: San Diego Center for Spinal Disorders, La Jolla, California;
authors.forename: Behrooz A
authors.initials: BA
authors.lastname: Akbarnia
authors.affiliation: Spine Center, UCSF Medical Center, San Francisco, California;
authors.forename: Vedat
authors.initials: V
authors.lastname: Deviren
authors.affiliation: Department of Neurosurgery and Brain Repair, University of South Florida, Tampa, Florida; and.
authors.forename: Juan S
authors.initials: JS
authors.lastname: Uribe
authors.affiliation: Department of Neurological Surgery, University of Michigan, Ann Arbor, Michigan;
authors.forename: Frank
authors.initials: F
authors.lastname: La Marca
authors.affiliation: Department of Neurosurgery, University of Pittsburgh, Pennsylvania.
authors.forename: Adam S
authors.initials: AS
authors.lastname: Kanter
authors.affiliation: Department of Neurosurgery, University of Pittsburgh, Pennsylvania.
authors.forename: David O
authors.initials: DO
authors.lastname: Okonkwo
authors.affiliation: San Diego Center for Spinal Disorders, La Jolla, California;
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Mundis
authors.affiliation: Department of Neurological Surgery and.
authors.forename: Praveen V
authors.initials: PV
authors.lastname: Mummaneni
mesh_terms: D004185:Disability Evaluation; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods* / Q000706:statistics & numerical data; D019637:Orthopedic Procedures / Q000379:methods* / Q000706:statistics & numerical data; D011379:Prognosis; D012189:Retrospective Studies; D013121:Spinal Curvatures / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000503:physiopathology / Q000601:surgery*; D013131:Spine / Q000000981:diagnostic imaging / Q000601:surgery; D016896:Treatment Outcome
keywords: ASD = adult spinal deformity; BMI = body mass index; EBL = estimated blood loss; LL = lumbar lordosis; LLIF = lateral lumbar interbody fusion; MI-TLIF = minimally invasive transforaminal lumbar interbody fusion; MIS = minimally invasive surgery; MISDEF = minimally invasive spinal deformity; ODI = Oswestry Disability Index; OR = operating room; PI = pelvic incidence; PI-LL = pelvic incidence–lumbar lordosis; PT = pelvic tilt; SRS = Scoliosis Research Society; SVA = sagittal vertical axis; TK = thoracic kyphosis; VAS = visual analog scale; deformity; minimally invasive surgery; outcome; spine