283. The position of the L1 vertebra relative to the gravity line does not appear to correlate with proximal junctional kyphosis following adult spinal deformity surgery with two year follow up

Abstract

BACKGROUND CONTEXT It is known that upper instrumented vertebrae (UIV) position relative to sagittal vertical axis (SVA) is associated with PJK. Over correction of the lumbar spine, resulting in posterior displacement of L1 relative to the GL, may be associated with PJK. PURPOSE Patients who are over corrected with hyper-lordotic spines may develop junctional problems because of forward compensatory leaning of the thoracic spine. Because L1 represents the thoracolumbar junction, its position relative to the gravity line (GL) may correlate with proximal junctional kyphosis (PJK). We investigated if the sagittal position of L1 relative to the GL correlates with PJK. STUDY DESIGN/SETTING Retrospective study. PATIENT SAMPLE Patients who undergoing ASD correction ≥6 levels from the lower thoracic (LT) spine to S1 with a minimum 2-year follow-up were reviewed. OUTCOME MEASURES Demographic data and radiographic spinopelvic parameters included: pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), PI–LL, sacral slope (SS), T1 pelvic angle (TPA), L1 pelvic angle (L1PA), T5-T12 thoracic kyphosis (TK), sagittal vertical axis (SVA) and L1-GL (cm). METHODS Patients who undergoing ASD correction ≥6 levels from the LT spine to S1 with a minimum 2-year follow-up were reviewed. Demographic data and radiographic spinopelvic parameters included: PI, PT, LL, PI–LL, SS, TPA, L1PA, TK, SVA and L1-GL (cm). GL is defined as the plumb line from external auditory canal. L1-GL is the distance from the center of L1 to GL. RESULTS A total of 76 patients met inclusion criteria including 36 patients with PJK and 40 patients without PJK, with a minimum 2-year follow up. There was no difference in age, gender, and follow-up time in the two groups. There was no statistical difference between groups with regard to PI, SS, PT, LL and TPA (P > 0.05). Preoperative L1PA was 16.00 ± 9.97°for PJK group and 15.75 ± 8.89° for non- PJK group (P =0.914). Preoperative L1-GL was 8.94 ± 6.45 cm for PJK group and 7.09 ± 5.43 cm for non-PJK group (P =0.178). Postoperative L1PA was 13.95 ± 6.76° for PJK group and 14.17 ± 9.35° for non-PJK group (P =0.908). Preoperative L1-GL was 6.00 ± 4.02 cm for PJK group and 7.6 ± 5.38 cm for non-PJK group (P =0.994). CONCLUSIONS The position of L1 vertebra relative to the gravity line does not appear to correlate with PJK after ASD surgery. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. It is known that upper instrumented vertebrae (UIV) position relative to sagittal vertical axis (SVA) is associated with PJK. Over correction of the lumbar spine, resulting in posterior displacement of L1 relative to the GL, may be associated with PJK. Patients who are over corrected with hyper-lordotic spines may develop junctional problems because of forward compensatory leaning of the thoracic spine. Because L1 represents the thoracolumbar junction, its position relative to the gravity line (GL) may correlate with proximal junctional kyphosis (PJK). We investigated if the sagittal position of L1 relative to the GL correlates with PJK. Retrospective study. Patients who undergoing ASD correction ≥6 levels from the lower thoracic (LT) spine to S1 with a minimum 2-year follow-up were reviewed. Demographic data and radiographic spinopelvic parameters included: pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), PI–LL, sacral slope (SS), T1 pelvic angle (TPA), L1 pelvic angle (L1PA), T5-T12 thoracic kyphosis (TK), sagittal vertical axis (SVA) and L1-GL (cm). Patients who undergoing ASD correction ≥6 levels from the LT spine to S1 with a minimum 2-year follow-up were reviewed. Demographic data and radiographic spinopelvic parameters included: PI, PT, LL, PI–LL, SS, TPA, L1PA, TK, SVA and L1-GL (cm). GL is defined as the plumb line from external auditory canal. L1-GL is the distance from the center of L1 to GL. A total of 76 patients met inclusion criteria including 36 patients with PJK and 40 patients without PJK, with a minimum 2-year follow up. There was no difference in age, gender, and follow-up time in the two groups. There was no statistical difference between groups with regard to PI, SS, PT, LL and TPA (P > 0.05). Preoperative L1PA was 16.00 ± 9.97°for PJK group and 15.75 ± 8.89° for non- PJK group (P =0.914). Preoperative L1-GL was 8.94 ± 6.45 cm for PJK group and 7.09 ± 5.43 cm for non-PJK group (P =0.178). Postoperative L1PA was 13.95 ± 6.76° for PJK group and 14.17 ± 9.35° for non-PJK group (P =0.908). Preoperative L1-GL was 6.00 ± 4.02 cm for PJK group and 7.6 ± 5.38 cm for non-PJK group (P =0.994). The position of L1 vertebra relative to the gravity line does not appear to correlate with PJK after ASD surgery.