14. Despite a multifactorial etiology, rates of distal junctional kyphosis after adult cervical deformity corrective surgery can be dramatically diminished by optimizing age-specific radiographic improvement

Abstract

<h3>BACKGROUND CONTEXT</h3> 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. <h3>PURPOSE</h3> To investigate the impact of postoperative radiographic alignment on development of DJK in ACD patients. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study of a multicenter prospective ACD database. <h3>PATIENT SAMPLE</h3> A total of 450 ACD patients. <h3>OUTCOME MEASURES</h3> DJK after cervical deformity surgery. <h3>METHODS</h3> ACD patients (18 yrs) with complete baseline (BL) and two-year (2Y) radiographic data were included. DJF was defined as DJK greater than 15 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. <h3>RESULTS</h3> A total of 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 <3.7 cm (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 <3.7 cm, and T4-T12 <50 predicted DJK with an AUC of .91 for DJK by 2 years, and .88 for DJF by 2 years. <h3>CONCLUSIONS</h3> These findings suggest postoperative radiographic alignment is strongly associated with distal junctional kyphosis. When utilizing age-adjusted realignment in addition to newly developed thresholds, a suggested postoperative cSVA target of 3.7 cm and thoracic kyphosis less than 50, it is possible to substantially reduce the occurrence of distal junctional kyphosis and distal junctional failure. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.