P111. Simulated corrections of cervical deformity using in-construct measures demonstrate that insufficient corrections result in DJK

BACKGROUND CONTEXT Distal junctional kyphosis (DJK) is a major concern following cervical deformity (CD) correction, leading to failed realignment and revision surgery. Undercorrection may be the major factor associated with DJK, however it is difficult to assess because the DJK erodes the correction and worsens traditional measures like cSVA. In-construct measures have been proposed that measure alignment within the fusion separate from the DJK and subjacent compensation. PURPOSE To simulate cervical deformity corrections using surgical planning software to determine if undercorrection results in DJK. STUDY DESIGN/SETTING Retrospective analysis of a prospective, multicenter CD database. PATIENT SAMPLE A total of 69 CD patients. OUTCOME MEASURES Radiographic measures: C2 plumblines, in-construct measures and DJK angle change. METHODS A prospective database of operative CD patients was analyzed for severe DJK (kyphosis change>20° in LIV to LIV-2) and traditional DJK (change>10°). C2LIV-Tilt (angle of a line from the centroid of C2 to the centroid of the lower instrumented vertebra and a line along the posterior vertebral body wall of the LIV) was measured postoperatively and the correction was simulated in the preoperative X-ray to match the C2LIV-Tilt using planning software. Linear regression analysis using C2 pelvic angle (CPA) and Pelvic Tilt (PT) determined the simulated PT to match the virtual CPA. SVA measures were compared in patients with severe and traditional DJK and no DJK. Linear regression analysis was used to determine the C2-T4 and C2-T10 Tilts that correspond to DJK=10° and cSVA=4cm. RESULTS A total of 69 CD patients (mean age 61, 60% female) were included. Severe and traditional DJK occurred in 11 (16%) and 22 (32%) patients; 3 (4%) required DJK revision. Simulated corrections demonstrated that severe and traditional DJK pts had worse alignments compared to no DJK pts: cSVA (42.5 vs 33.0 vs 23.4mm, p .57, p CONCLUSIONS Simulated cervical deformity corrections demonstrated that severe DJK patients have insufficient corrections compared to patients without DJK. In-construct measures assess sagittal alignment within the fusion separate from DJK and subjacent compensation. They can be useful as intraoperative tools to gauge the adequacy of CD correction. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.