Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P90. Touched vertebra (TV) on standing XR is a good predictor for LIV. TV on prone XR is better

Abstract

BACKGROUND CONTEXT Minimizing the fusion levels in PSF for AIS is important. Previous studies have shown good results utilizing touched vertebra (TV) as the lowest instrumented vertebra (LIV). TV is the vertebra ‘touched; by central sacral vertical line on standing AP XRs (TVS). In our experience, we find that TV moves proximally on supine or prone XRs. Thus utilizing TV on prone XRs (TVP) in LIV decision making may allow even shorter fusion. PURPOSE To determine if using TVP to determine LIV saves fusion levels with good correction and coronal balance. STUDY DESIGN/SETTING Ambispective cohort study. PATIENT SAMPLE A total of 260: 132 nonoperative scoliosis patients, 128 who underwent pedicle screw fixation. OUTCOME MEASURES Cobb, coronal balance, disc wedging, LIV tilt, levels saved, decompensation. METHODS There were three groups. Group I: patients where TVP was used to determine LIV. Group II: patients where TVS was used to determine LIV. Group III: nonoperative AIS (Risser 4/5, Cobb RESULTS The control group had 100 patients with a median Cobb angle of 20°, age of 15.3years, coronal balance 1.2 cm (0.5–1.8), disc wedging of 4° (3–6), and LIV tilt of 9° (6–11.5). In group I (n=83), median pre-op Cobb was 53.75° (47.55°–61.9°), kyphosis was 32.2° (25.3°–38.9°), and coronal balance was 1.6 cm (1.0–3.0 cm). Post op median Cobb was 12.9° (7.0°–19.7°), kyphosis was 37° (24.6°–39.7°) and coronal balance was 1.4 cm (0.3–2.45 cm). Compared to controls, group I patients had similar coronal balance (0.9vs. 1.2, p=.18), but significantly lower disc wedging (1.2° vs. 4, p>.001), and LIV tilt (4.3° vs. 9 p CONCLUSIONS In AIS, using TVP to determine LIV allows shorter fusion saving than TVS. Despite shorter fusion, coronal balance and correction is maintained, at final follow up with no adding on. LIV tilt and disc wedging is also within ‘acceptable’ levels determined on controls.