Despite a Multifactorial Etiology, Rates of Distal Junctional Kyphosis After Adult Cervical Deformity Surgery Can Be Dramatically Diminished by Optimizing Age Specific Radiographic Improvement

Introduction: Distal Junctional Kyphosis (DJK) is one of the most common complications in adult cervical deformity (ACD) correction. The utility of radiographic alignment alone in predicting and minimizing DJK occurrence warrants further study.

Methods: ACD patients (≥18 yrs) with complete baseline (BL) and two-year(2Y) radiographic data were included. DJF was defined as DJK greater than 15 (Passias et al.), or DJK with reop. Multivariable logistic regression (MVA) identified 3 month predictors of DJK. Conditional inference tree (CIT) machine learning analysis determined threshold cutoffs. Radiographic predictors were combined in a model to determine predictive value using area under the curve (AUC) methodology. “Match” refers to ideal age-adjusted alignment.

Results: 140 cervical deformity patients met inclusion criteria (61.3yrs, 67%F, BMI: 29kg/m2, CCI: 0.96±1.3). Surgically, 51.3% had osteotomies, 47.1% had a posterior approach, 34.5% combined approach, 18.5% anterior approach, with an average 7.6± 3.8 levels fused and EBL of 824 mL. Overall, 33 patients (23.6%) developed DJK, and 11 patients (9%) developed DJF. MVA controlling for age, and baseline deformity, followed by CIT found 3M cSVA < 3.7cm (OR: .2, 95% CI:.06-.6), and TK T4-T12 < 50 (OR:.17, 95% CI:.05-.5, both p < .05) were significant predictors of a lower likelihood of DJK. Receiver operator curve AUC using age, T1S match, TS-CL match, LL-TK match, cSVA < 3.7cm, and T4-T12 < 50 predicted DJK with an AUC of .91 for DJK by 2Y, and .88 for DJF by 2Y.

Conclusion : These findings suggest post-operative radiographic alignment is strongly associated with distal junctional kyphosis. When utilizing age-adjusted realignment in addition to newly developed thresholds, a suggested post-operative cSVA target of 3.7cm and thoracic kyphosis less than 50, it is possible to substantially reduce the occurrence of distal junctional kyphosis and distal junctional failure.