Representative lordosis and disc height measurements. Regional Cobb angles are based on the superior endplate of L1 and the superior endplate of S1 to measure regional lumbar lordosis. Segmental Cobb angles are based on the superior endplate of the rostral vertebral body and the inferior endplate of the caudal vertebral body (L4 and L5 in this example). Disc heights are calculated using the average between the anterior and posterior disc heights.