285. Choosing touched vertebrae with grade 0/1 rotation on lying down X-rays saves fusion levels, decreases risk of adding on, and prevents translation

Abstract

BACKGROUND CONTEXT TV is the ‘touched’ vertebra determined by CSVL on standing AP XRs. Fusion proximal to TV leads to suboptimal results but fusing to TV on standing XRs can lead to longer fusions. The TV, however, moves proximally and its rotation also decreases on lying down. PURPOSE The purpose of this study is to determine a radiographic measurement to that may aid in determining lowest instrumented vertebra (LIV). STUDY DESIGN/SETTING Retrospective control-cohort. PATIENT SAMPLE AIS patients undergoing spinal deformity correction, excluding those that exclusively had thoracic fusion, at one institution. Patients were separated based on LIV. OUTCOME MEASURES Cobb angle, Cobb correction, fusion levels, LIV tilt, disc wedging, and LIV translation were on analyzed pre-, post- and final XRs. Disc wedging >5° was used to determine risk of ‘adding-on.’ Sub-analysis was carried out for Lenke 1 and Lenke 3 patients. METHODS Touched vertebra (TV): TV with minimal rotation (Gd 0/1) chosen as LIV. Non-TV (NTV): LIV proximal to TV or TV with >Gd 1 rotation. Cobb, fusion levels, LIV tilt, disc wedging, and LIV translation were analyzed pre-, post- and final. Part II: Pts LIV on standing XRs (TVS) vs prone X-rays (TVP) to determine levels saved. RESULTS TV and NTV group had similar Cobb and LIV tilt (p>0.05). Disc wedging was significantly larger for NTV patients (p<0.001). LIV translation was significantly larger in NTV (p<0.001). Greater disc wedging and LIV translation were seen in Lenke 3 NTV pts. For Lenke 1, significantly larger percentage of NTV were at risk of adding-on (p=0.04). In part II, average of 11.7 levels were fused in TVP. 12.6 levels would have been fused if LIV was determined on standing XRs. Thus, utilizing prone XRs saved average 1.2 levels. In TVS, LIV was the TV on standing XR and an average of 12 levels were fused. However, determining LIV on prone XR showed an average of 10.8 levels. Thus, utilizing prone XRs would have saved 1.2 levels. CONCLUSIONS In AIS, fusing proximal to minimally rotated (Gd 0/1) TV or fusing to TV with > Gd1 rotation leads to an increased disc wedging and translation. Choosing minimally rotated (Gd 0/1) TV on prone XR saves levels without sacrificing outcomes. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. TV is the ‘touched’ vertebra determined by CSVL on standing AP XRs. Fusion proximal to TV leads to suboptimal results but fusing to TV on standing XRs can lead to longer fusions. The TV, however, moves proximally and its rotation also decreases on lying down. The purpose of this study is to determine a radiographic measurement to that may aid in determining lowest instrumented vertebra (LIV). Retrospective control-cohort. AIS patients undergoing spinal deformity correction, excluding those that exclusively had thoracic fusion, at one institution. Patients were separated based on LIV. Cobb angle, Cobb correction, fusion levels, LIV tilt, disc wedging, and LIV translation were on analyzed pre-, post- and final XRs. Disc wedging >5° was used to determine risk of ‘adding-on.’ Sub-analysis was carried out for Lenke 1 and Lenke 3 patients. Touched vertebra (TV): TV with minimal rotation (Gd 0/1) chosen as LIV. Non-TV (NTV): LIV proximal to TV or TV with >Gd 1 rotation. Cobb, fusion levels, LIV tilt, disc wedging, and LIV translation were analyzed pre-, post- and final. Part II: Pts LIV on standing XRs (TVS) vs prone X-rays (TVP) to determine levels saved. TV and NTV group had similar Cobb and LIV tilt (p>0.05). Disc wedging was significantly larger for NTV patients (p<0.001). LIV translation was significantly larger in NTV (p<0.001). Greater disc wedging and LIV translation were seen in Lenke 3 NTV pts. For Lenke 1, significantly larger percentage of NTV were at risk of adding-on (p=0.04). In part II, average of 11.7 levels were fused in TVP. 12.6 levels would have been fused if LIV was determined on standing XRs. Thus, utilizing prone XRs saved average 1.2 levels. In TVS, LIV was the TV on standing XR and an average of 12 levels were fused. However, determining LIV on prone XR showed an average of 10.8 levels. Thus, utilizing prone XRs would have saved 1.2 levels. In AIS, fusing proximal to minimally rotated (Gd 0/1) TV or fusing to TV with > Gd1 rotation leads to an increased disc wedging and translation. Choosing minimally rotated (Gd 0/1) TV on prone XR saves levels without sacrificing outcomes.