Preoperative standard lateral radiograph in a patient who underwent a C5-C6 anterior cervical discectomy and fusion. The Cobb angle between the C2 and C7 vertebrae is determined by measuring the angle formed by the lines between the lower endplates of the C2 and C7 vertebrae. The angle of the functional segmental unit (C5-C6) is determined by measuring angle between the lines of the upper endplate of the C5 vertebra and the lower endplate of the C6 vertebra.