title: Cranial Center of Mass Compared to C7 Plumb Line Alignment in Adult Spinal Deformity.
abstract: OBJECTIVE
  To report the cranial center of mass (CCOM) progression in surgically treated patients for adult spinal deformity (ASD). The C7 plumb line/sagittal vertical axis (SVA) has important relationships with patient-reported outcomes; however, this has not yet been defined for CCOM.
  
  
  METHODS
  Patients with consecutive ASD who were undergoing surgery greater than 5 levels of fusion between 2007 and 2012 and had radiographic, clinical, and outcomes data spanning ≥2 years were analyzed, retrospectively. Radiographic parameters were obtained preoperatively and at 6 weeks, 1 year, and 2 years postoperatively. Statistical analysis included descriptives (measures of central tendency, dispersion, frequencies), independent Student t tests, χ(2) square, Pearson correlation, and Kaplan-Meyer curve.
  
  
  RESULTS
  Fifty-eight patients (10 male, 48 female) with a mean age of 60.5 years (range, 27-81 years) were reviewed. The mean preoperative SVA was 7.40 cm (SD = 5.51; 37/58 [63.8%] malalignment), and mean CCOM was 10.0 cm (SD = 6.58; 47/58 [81%] malalignment). Six-week postoperative SVA and CCOM was -0.17 cm (SD = 3.3) and 2.5 cm (SD = 4.11), respectively. SVA malalignment was 12.7% and CCOM malalignment was 38.2% at 6 weeks postop. Six week (absolute), 6-week change, and patient number at 6 weeks who were CCOM malaligned was significant compared with SVA (P = 0.003, P < 0.001, P < 0.001, respectively). SRS appearance worsened as preoperative SVA and CCOM increased (P < 0.05), and 2-year SRS appearance and mental health was worsened as 2-year SVA and CCOM increased (P < 0.05). SVA malalignment was 8 and 10 at 1 and 2 years, respectively, and CCOM malalignment was 24 and 32, respectively. Kaplan-Meier curve demonstrates persistent malalignment of CCOM at 6 weeks if not corrected.
  
  
  CONCLUSIONS
  CCOM alignment restoration is an important parameter in ASD, and malalignment is consistent over time.
authors.affiliation: Department of Pediatric Neurosurgery, Phoenix Children's Hospital, Phoenix, Arizona, USA. Electronic address: jmcclendon@phoenixchildrens.com.
authors.forename: Jamal
authors.initials: J
authors.lastname: McClendon
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Northwestern Feinberg School of Medicine, Chicago, Illinois, USA.
authors.forename: Randall B
authors.initials: RB
authors.lastname: Graham
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Northwestern Feinberg School of Medicine, Chicago, Illinois, USA.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Sugrue
authors.affiliation: Department of Neurological Surgery, Brigham and Women's Hospital, Harvard School of Medicine, Boston, Massachusetts, USA.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Smith
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Northwestern Feinberg School of Medicine, Chicago, Illinois, USA.
authors.forename: Sara E
authors.initials: SE
authors.lastname: Thompson
authors.affiliation: Department of Neurological Surgery, Northwestern Memorial Hospital, Northwestern Feinberg School of Medicine, Chicago, Illinois, USA.
authors.forename: Tyler R
authors.initials: TR
authors.lastname: Koski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000071066:Patient Reported Outcome Measures; D012189:Retrospective Studies; D012886:Skull / Q000000981:diagnostic imaging*; D013121:Spinal Curvatures / Q000000981:diagnostic imaging* / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*
keywords: Adult spinal deformity; Cranial center of mass; Patient-reported outcomes; Sagittal vertical axis; Scoliosis Research Society