Virtual Modeling of Postoperative Alignment after Adult Spinal Deformity Surgery Helps Predict Associations between Compensatory Spinopelvic Alignment Changes, Overcorrection, and Proximal Junctional Kyphosis

International Spine Study Group

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Study Design. Retrospective review of a prospective multicenter database. Objective. To develop a method to analyze sagittal alignment, free of the influence of proximal junctional kyphosis (PJK), and then compare PJK to non-PJK patients using this method. Summary of Background Data. PJK after adult spinal deformity (ASD) surgery remains problematic as it alters sagittal alignment. The present study proposes a novel virtual modeling technique that attempts to eliminate the confounding effects of PJK on postoperative spinal alignment. Methods. A virtual spinal modeling technique was developed on a retrospective ASD cohort of patients with multilevel spinal fusions to the pelvis with at least 2-year postoperative follow-up. The virtual postoperative alignment (VIRTUAL) was created from the postoperative alignment of the instrumented segments and the preoperative alignment of the unfused segments. VIRTUAL was validated by comparisons to actual 2-year postoperative alignment (REAL) in non-PJK patients. Patients were then divided into two groups: PJK and non-PJK based on the presence/absence of PJK at 2 years postoperatively. PJK and non-PJK patients were compared using VIRTUAL and REAL. Results. A total of 458 patients (78F, mean 57.9 yr) were analyzed. The validation of VIRTUAL versus REAL demonstrated correlation coefficients greater than 0.7 for all measures except sagittal vertical axis (SVA; r = 0.604). At 2 years, REAL alignment in PJK patients demonstrated a smaller pelvic incidence minus lumbar lordosis and a larger thoracic kyphosis than non-PJK patients, but similar SVA, T1 pelvic angle, and pelvic tilt. An analysis of VIRTUAL demonstrated that patients with PJK had a smaller pelvic incidence minus lumbar lordosis, pelvic tilt, SVA, and T1 pelvic angle than non-PJK patients (P < 0.05). Conclusion. This technique demonstrated strong correlations with actual postoperative alignment. Comparisons between REAL and VIRTUAL alignments revealed that postoperative PJK may develop partially as a compensatory mechanism to the overcorrection of sagittal deformities. Future research will evaluate the appropriate thresholds for deformity correction according to age and ASD severity.

Original languageEnglish (US)
Pages (from-to)E1119-E1125
JournalSpine
Volume42
Issue number19
DOIs
StatePublished - Oct 1 2017

Keywords

  • ASD
  • PJK
  • adult spinal deformity
  • compensatory mechanism
  • pelvic fixation
  • proximal junctional kyphosis
  • sagittal alignment
  • simulation
  • spine surgery
  • virtual alignment

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology

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