title: Analysis of an unexplored group of sagittal deformity patients: low pelvic tilt despite positive sagittal malalignment.
abstract: In adult spinal deformity (ASD), patients increase pelvic tilt (PT) to maintain standing alignment. Previously, ASD patients with low PT and high disability were described. This study investigates this unusual population in terms of demographic, radiographic, and clinical features after three-column osteotomy (3CO).
  
  
  
  In this multicenter retrospective study, ASD patients underwent single lumbar 3CO. Since PT is proportional to pelvic incidence (PI), the low PT group (LowPT) was defined as having a baseline (BL) PT/PI <25th percentile. HRQOL and full spine x-rays were analyzed at BL and 1 year. LowPT patients were compared to those with high PT/PI (HighPT) in a matched range of T1 pelvic angle.
  
  
  
  LowPT group had PT/PI <0.4 (n = 31). High disability was reported at baseline for both groups with significant improvement postoperatively, but without difference between groups. LowPT had significantly smaller lack lumbar lordosis but larger SVA, T1 spinopelvic inclination. Postoperatively, there were improvements in all sagittal modifiers except PT in LowPT. 33 % of LowPT had an increase in PT (>5°) postoperatively. This subset had more deformity at baseline, achieving good T1SPi postoperative correction but without achieving the SRS-Schwab target SVA at 1 year.
  
  
  
  LowPT group had high levels of disability. After 3CO surgery, low PT patients experience only partial improvements in sagittal vertical axis (SVA) and 33 % of the group increased their PT. Further work is necessary to determine optimal realignment approaches for this unusual set of patients. It is unclear if neuromuscular pathology plays a role in the setting of high SVA without pelvic retroversion.
authors.affiliation: Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 east 15th street, New York, NY, 10003, USA. emmanuelle.ferrero@gmail.com.|Orthopedic Surgery Department, Hopital Européen Georges Pompidou, APHP, Paris V University, 20 rue Leblanc, 75015, Paris, France. emmanuelle.ferrero@gmail.com.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Ferrero
authors.affiliation: Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 east 15th street, New York, NY, 10003, USA.
authors.forename: Shaleen
authors.initials: S
authors.lastname: Vira
authors.affiliation: Neurosurgery, San Francisco Medical Center, University of California, San Francisco, CA, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Ames
authors.affiliation: Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Khaled
authors.initials: K
authors.lastname: Kebaish
authors.affiliation: Spine Surgery, Hopital Pellegrin, Bordeaux, France.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Obeid
authors.affiliation: Orthopaedic Surgery, Baylor Scoliosis Center, Plano, TX, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: O'Brien
authors.affiliation: Orthopaedic Surgery, University of California, Davis, Sacramento, CA, USA.
authors.forename: Munish C
authors.initials: MC
authors.lastname: Gupta
authors.affiliation: Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA.
authors.forename: Oheneba
authors.initials: O
authors.lastname: Boachie-Adjei
authors.affiliation: Neurosurgery, University of Virginia Medical Center, Charlottesville, VA, USA.
authors.forename: Justin S
authors.initials: JS
authors.lastname: Smith
authors.affiliation: San Diego Center for Spinal Disorders, La Jolla, CA, USA.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Mundis
authors.affiliation: Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 east 15th street, New York, NY, 10003, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: Challier
authors.affiliation: Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 east 15th street, New York, NY, 10003, USA.
authors.forename: Themistocles S
authors.initials: TS
authors.lastname: Protopsaltis
authors.affiliation: Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 east 15th street, New York, NY, 10003, USA.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Schwab
authors.affiliation: Orthopaedic Surgery, NYU Hospital for Joint Diseases, 306 east 15th street, New York, NY, 10003, USA.
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000503:physiopathology*; D011187:Posture / Q000502:physiology*; D011859:Radiography; D012189:Retrospective Studies; D013121:Spinal Curvatures / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000503:physiopathology / Q000601:surgery
keywords: 3 column osteotomy; Clinical outcomes; Compensatory mechanism; Pelvic tilt; Sagittal alignment