173. Defining symptomatic versus radiographic distal junctional kyphosis after cervical deformity-corrective surgery

Abstract

BACKGROUND CONTEXT Distal junctional kyphosis (DJK) is a relatively new surgical concept often defined in the literature as a change in DJK angle PURPOSE To establish a clinically relevant definition of symptomatic DJK. STUDY DESIGN/SETTING Retrospective review of a prospective CD surgery database. PATIENT SAMPLE One hundred and two patients with cervical deformity. OUTCOME MEASURES Demographics, HRQL metrics. METHODS A prospective database of operative CD patients was analyzed. Inclusion criteria were cervical kyphosis >10˚, cervical scoliosis >10˚, cSVA >4cm or CBVA >25˚. DJK angle (DJKA) was defined >10° change in kyphosis between LIV and LIV-2 in addition to >10° index angle. Pts with DJKA >10° & 1) no reop due to DJK(DJF) & 2) no physician-reported neurological sequelae at any time-point up to 1yr were categorized as “mild DJK.” Those with a DJKA >10° in addition to 1) reop due to DJK(DJF) or 2) >1 new-onset neurological sequelae related to DJK (spinal cord deficit, gait disturbance, hyperreflexia, lower-limb spasticity) were categorized as “Symptomatic DJK.” ANOVA explored differences in PROMs (NDI, mJOA, EQ5D, EQ5DVAS, NRS) at baseline (BL) up to 1yr follow-up. Multivariate logistic regression analyzed predictors of inferior HRQLs associated with DJK groups, specifically scoring beyond one standard deviation (SD) of the mean value of all DJK pts. RESULTS One hundred and two CD patients were analyzed. Sixty-five pts had no DJK, 25 pts had mild DJK and 12 pts had symptomatic DJK. By 1 year, 6/12 pts had DJF, 6/12 pts had >1 DJK-related neurologic sequelae not present before surgery(20% corticospinal tract deficit, 20% spasticity, 20% gait impairment, 20% hyperreflexia) without DJF, and 2 pts had both. Symptomatic DJK pts had higher mean DJKA than mild DJK pts immediately postop (29.8° vs 19.1°, p=0.150). No differences in BL HRQLs were noted between groups, including NDI, mJOA, EQ5D, VAS, and NRS Back (all p>0.05). At 1yr, Symptomatic DJK pts had significantly higher disability (52.3 vs 28.7, p=0.006) and trended lower EQ5D scores (0.75 vs 0.81, p=0.059), higher NRS back pain (5.82 vs 4.06, p=0.119), lower VAS (56.4 vs71.7,p=0.084), and lower mJOA (14.2 vs 15.0,p=0.495) than their mild DJK counterparts. Controlling for age and gender, conditional forward regression analysis revealed symptomatic DJK to a strong predictor of NDI >1 SD of the mean compared to mild DJK pts (OR: 43.4 [2.8 - 668.1], p=0.007); that is, symptoDJK increased the odds of NDI>1SD by at least 2.8x in relation to the mild DJK cohort. CONCLUSIONS DJK associated with reoperation and/or neurologic sequelae was associated with inferior quality of life metrics over long-term follow-up. Our results demonstrate that Symptomatic DJK may not necessarily correlate to a greater measured DJK angle per se (ie, >20°); instead, DJK with concurrent neuro findings or subsequent reop better predicts worsened disability compared to DJK alone. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.