P105. When does the construct need to extend to the thoracic spine in patients undergoing correction for cervical deformity?

Abstract

<h3>BACKGROUND CONTEXT</h3> Thoracolumbar malalignment is often seen in patients presenting with cervical deformities. For operative cervical deformity (CD) patients, it is unknown when the thoracic spine should be included in the construct. <h3>PURPOSE</h3> To investigate the CD patients in whom fusion to the thoracic spine was warranted. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> A total of 72 CD patients. <h3>OUTCOME MEASURES</h3> Radiographic parameters; complications, distal junctional kyphosis [DJK], reoperation; Health-Related Quality-of-Life [HRQLs]: NDI, NRS-neck, mJOA. <h3>METHODS</h3> Included: operative CD patients (C2-C7 lordosis < -15°, TS-CL >35°, segmental cervical kyphosis >15° across any 3 vertebra between C2-T1, C2-C7 SVA >4cm, McGregor's slope >20°, or CBVA > 25°) with baseline (BL) and up to 2-year (2Y) data. Patients with UIV at or above C4 and LIV extending beyond C7 into the thoracic spine were isolated (CT fusions). CT fusion patients were further stratified to upper and lower thoracic LIVs: T1-T4 [Short Fusion], beyond T4 [Long Fusion]. CT fusion patients were identified as having an optimal outcome at 2-year postop if they 1) did not have DJF and 2) had Virk et al. good clinical outcome [≥2 of the following: NDI <20 or meeting MCID, mild myelopathy (mJOA ≥14), NRS-Neck ≤5 or improved by ≥2 points from baseline]. Univariate analysis compared patients with long fusion and optimal outcome (L/Success) vs patients with short fusion and treatment failure (S/Fail). Multivariate analysis and ROC curve assessed demographic, surgical, and radiographic predictors of S/ Fail and L/S Success status. Conditional inference tree (CIT) determined cut-off values for the continuous predictors. <h3>RESULTS</h3> Seventy-two cervical deformity patients with CT fusion included (60.3±9.0years, 60% F, 29.4±7.6 kg/m2, levels fused: 7.8±3.2). By approach, 61% posterior-only and 39% combined. Fifty-nine patients (82%) had CT fusions with LIV of T4 or above, while 13 patients (18%) had fusions extending below T4. Thirty-two patients (44.4%) met the optimal outcome criteria, with no difference by fusion length (p=0.171). Eight patients qualified as long fusions with treatment success, while 35 patients were classified as short fusions with treatment failure. Regression analysis identified the predictors of treatment success in patients with fusion construct extending beyond T4: baseline sacral slope ≤33.5° (OR: 15.0), not undergoing high grade (PSO or VCR) osteotomy (OR: 15.0) and being Ames descriptor type C (OR: 13.5); all p<0.05). ROC curve accounting for these factors resulted in an AUC of 82.0%. Regression analysis identified predictors of treatment failure in patients with short fusion construct: levels fused >6 (OR: 4.3), Ames descriptor type CT (OR: 11.5), Ames cSVA modifier grade 1 or 2 at BL (OR: 4.56), and Flatneck Lafage morphotype (OR: 4.5); all p<0.05. Multivariate regression and ROC curve accounting for these factors resulted in an AUC of 84.3%. <h3>CONCLUSIONS</h3> Treatment success in patients with fusion constructs extending into the thoracic spine vs treatment failure in patients with short fusions may be reliably predicted by the location of the deformity apex, measures of surgical invasiveness, and preoperative deformity severity. Specifically, treatment success in longer fusions is related to deformity apex in the cervical spine and having deformity where adequate correction does not necessitate high grade osteotomy. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.