Virtual Modeling of Postoperative Alignment Following Adult Spinal Deformity (ASD) Surgery Helps Predict associations between Compensatory Spinopelvic Alignment Changes, Overcorrection and Proximal Junctional Kyphosis (PJK)

Renaud Lafage, Shay Bess, Steve Glassman, Christopher Ames, Doug Burton, Robert Hart, Han Jo Kim, Eric Klineberg, Jensen Henry, Breton Line, Justin Scheer, Themistocles Protopsaltis, Frank Schwab, Virginie Lafage

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

STUDY DESIGN.: Retrospective review of a prospective multicenter database. OBJECTIVE.: To develop a method to analyze sagittal alignment, free of PJKʼs influence, and then compare PJK to non-PJK patients using this method. SUMMARY OF BACKGROUND DATA.: Proximal Junctional Kyphosis (PJK) following Adult Spinal Deformity (ASD) surgery remains problematic as it alters sagittal alignment. This 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 post-operative follow-up. The virtual post-op alignment (VIRTUAL) was created from the post-op alignment of the instrumented segments and the pre-op alignment of the unfused segments. VIRTUAL was validated by comparisons to actual 2-year post-op alignment (REAL) in NOPJK patients. Patients were then divided into two groups: PJK and NOPJK based on the presence/absence of PJK at 2 years post-op. PJK and NOPJK patients were compared using VIRTUAL and REAL. RESULTS.: 458 patients (78F, mean 57.9y) were analyzed. The validation of VIRTUAL versus REAL demonstrated correlation coefficients above 0.7 for all measures except SVA (r?=?0.604). At 2-years, REAL alignment in PJK patients demonstrated a smaller PI-LL and a larger thoracic kyphosis than NOPJK patients, but similar SVA, TPA, and PT. An analysis of VIRTUAL demonstrated that PJK patients had a smaller PI-LL, PT, SVA, and TPA than NOPJK 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 over-correction of sagittal deformities. Future research will evaluate the appropriate thresholds for deformity correction according to age and ASD severity.Level of Evidence: 3

Original languageEnglish (US)
JournalSpine
DOIs
StateAccepted/In press - Feb 9 2017

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology

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    Lafage, R., Bess, S., Glassman, S., Ames, C., Burton, D., Hart, R., Kim, H. J., Klineberg, E., Henry, J., Line, B., Scheer, J., Protopsaltis, T., Schwab, F., & Lafage, V. (Accepted/In press). Virtual Modeling of Postoperative Alignment Following Adult Spinal Deformity (ASD) Surgery Helps Predict associations between Compensatory Spinopelvic Alignment Changes, Overcorrection and Proximal Junctional Kyphosis (PJK). Spine. https://doi.org/10.1097/BRS.0000000000002116