General Session: Adult Spinal Deformity - Hall F
Presented by: P. Passias
P. Passias(1), D. Vasquez-Montes(1), G. Poorman(1), T. Protopsaltis(1), S. Horn(1), B. Diebo(2), C. Bortz(1), F. Segreto(1), D. Ge(1), C. Varlotta(1), C. Ames(3), J. Smith(4), V. Lafage(5), R. Lafage(5), E. Klineberg(6), C. Shaffrey(4), S. Bess(7), F. Schwab(5), International Spine Study Group
(1) New York University Langone Orthopedic Hospital, Division of Spinal Surgery, New York, NY, United States
(2) SUNY Downstate Medical Center, Department of Orthopaedic Surgery, Brooklyn, NY, United States
(3) University of California San Francisco, Department of Neurological Surgery, San Francisco, CA, United States
(4) University of Virginia, Department of Neurosurgery, Charlottesville, VA, United States
(5) Hospital for Special Surgery, Department of Orthopaedic Surgery, New York, NY, United States
(6) University of California Davis, Department of Orthopaedic Surgery, Sacramento, CA, United States
(7) Rocky Mountain Scoliosis and Spine, Denver, CO, United States
Introduction: Distal Junctional Kyphosis (DJK) is a primary concern of surgeons correcting cervical deformity. Identifying patients and procedures at higher risk for developing this condition is paramount in improving patient selection and care. The aim of this study was to develop a risk index for DJK development in the first year after surgery.
Methods: Retrospective review of a prospective multicenter cervical deformity database. Patients over the age of 18 meeting one of the following deformity cervical kyphosis (C2-7 Cobb angle >10°), cervical scoliosis (coronal Cobb angle >10°), positive cervical sagittal imbalance (C2-C7 sagittal vertical axis >4cm or T1-C6 >10 o), or horizontal gaze impairment (chin-brow vertical angle >25o). DJK was defined by both clinical diagnosis (by enrolling surgeon) and post-hoc identification of development of an angle < -10 degrees from the end of fusion construct to the 2nd distal vertebra, as well as a change in this angle by < -10 from baseline. Conditional Inference Decision Trees were used to identify factors predictive of DJK incidence and the cut-off points at which they have an effect. A conditional Variable-Importance table was constructed based on a non-replacement sampling set of 2000 Conditional Inference Trees. 12 influencing factors were found, binary logistic regression for each variable at significant cut-offs indicated their effect size.
Results: Statistical analysis included 101 surgical patients (average age: 60.1 years, 58.3% female, BMI: 30.2) undergoing long cervical deformity correction (mean levels fused: 7.1, osteotomy used: 49.5%, Approach: 46.5% Posterior, 17.8% Anterior, 35.7% Combined). In two years after surgery 6% of patients were diagnosed with clinical DJK, however 23.8% of patients met radiographic definition for DJK. Patients with neurologic symptoms were at risk for DJK (OR:3.71 CI:0.11-0.63). However, no significant relationship was found between osteoporosis, age, or ambulatory status with DJK incidence. Baseline radiographic malalignments were more the most numerous and strong predictors for DJK:  C2-T1 Tilt >5.33 (OR:6.94 CI:2.99-16.14),  Kyphosis < -50.6⁰ (OR:5.89 CI:0.07-0.43),  C2-C7 lordosis < -12⁰ (OR:5.7 CI:0.08-0.41),  T1 Slope minus Cervical Lordosis>36.4 (OR:5.6 CI:2.28-13.57),  C2-C7 SVA >56.3⁰ (OR:5.4 CI:2.20-13.23), and  C4_Tilt >56.7 (OR:5.0 CI:1.90-13.1).Clinically, combined approaches (OR:2.67 CI:1.21-5.89) and usage of Smith Petersen osteotomy (OR:2.55 CI:1.02-6.34) were the most important predictors for DJK.
Conclusions: In a surgical cohort of cervical deformity patients, we found a 23.8% incidence of DJK. Different procedures and patient malalignment predicted incidence of DJK up to 1-year. Preoperative TS-CL, Cervical Kyphosis, SVA, and Cervical Lordosis all strongly predicted DJK at specific cut-off points. Knowledge of these factors will potentially help direct future study and strategy aimed at minimizing this potentially dramatic occurrence.