Effect of age-adjusted alignment goals and distal inclination angle on the fate of distal junctional kyphosis in cervical deformity surgery
Peter Gust Passias1, Samantha R Horn1, Virginie Lafage2, Renaud Lafage2, Justin S Smith3, Breton G Line4, Themistocles S Protopsaltis1, Alex Soroceanu5, Cole Bortz1, Frank A Segreto1, Waleed Ahmad1, Sara Naessig1, Katherine E Pierce1, Avery E Brown1, Haddy Alas1, Han Jo Kim2, Alan H Daniels6, Eric O Klineberg7, Douglas C Burton8, Robert A Hart9, Frank J Schwab2, Shay Bess4, Christopher I Shaffrey3, Christopher P Ames10
1 Department of Orthopaedics, NYU Medical Center-Orthopaedic Hospital, New York City, NY, USA
2 Department of Orthopaedic Surgery, Hospital for Special Surgery, New York City, NY, USA
3 Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, VA, USA
4 Department of Spine Surgery, Denver International Spine Clinic, Denver, Colorado, USA
5 Department of Orthopaedic Surgery, University of Calgary, Calgary, Canada
6 Department of Orthopaedic Surgery, Warren Alpert School of Medicine, Brown University, Providence, RI, USA
7 Department of Orthopaedic Surgery, University of California, Davis, USA
8 Department of Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, Kansas, USA
9 Department of Orthopaedic Surgery, Swedish Neuroscience Institute, Seattle, WA, USA
10 Department of Neurological Surgery, University of California, San Francisco, CA, USA
Peter Gust Passias
Department of Orthopaedic and Neurological Surgery, NYU Medical Center-Orthopaedic Hospital, New York Spine Institute, 301 East 17th Street, New York, NY 10003
Source of Support: None, Conflict of Interest: None
Background: Age-adjusted alignment targets in the context of distal junctional kyphosis (DJK) development have yet to be investigated. Our aim was to assess age-adjusted alignment targets, reciprocal changes, and role of lowest instrumented level orientation in DJK development in cervical deformity (CD) patients.
Methods: CD patients were evaluated based on lowest fused level: cervical (C7 or above), upper thoracic (UT: T1–T6), and lower thoracic (LT: T7–T12). Age-adjusted alignment targets were calculated using published formulas for sagittal vertical axis (SVA), pelvic incidence-lumbar lordosis (PI-LL), pelvic tilt (PT), T1 pelvic angle (TPA), and LL-thoracic kyphosis (TK). Outcome measures were cervical and global alignment parameters: Cervical SVA (cSVA), cervical lordosis, C2 slope, C2–T3 angle, C2–T3 SVA, TS-CL, PI-LL, PT, and SVA. Subanalysis matched baseline PI to assess age-adjusted alignment between DJK and non-DJK.
Results: Seventy-six CD patients included. By 1Y, 20 patients developed DJK. Non-DJK patients had 27% cervical lowest instrumented vertebra (LIV), 68% UT, and 5% LT. DJK patients had 25% cervical, 50% UT, and 25% LT. There were no baseline or 1Y differences for PI, PI-LL, SVA, TPA, or PT for actual and age-adjusted targets. DJK patients had worse baseline cSVA and more severe 1Y cSVA, C2–T3 SVA, and C2 slope (P < 0.05). The distribution of over/under corrected patients and the offset between actual and ideal alignment for SVA, PT, TPA, PI-LL, and LL-TK were similar between DJK and non-DJK patients. DJK patients requiring reoperation had worse postoperative changes in all cervical parameters and trended toward larger offsets for global parameters.
Conclusion: CD patients with severe baseline malalignment went on to develop postoperative DJK. Age-adjusted alignment targets did not capture differences in these populations, suggesting the need for cervical-specific goals.