Fig. 1From: Factors associated with non-fusion after direct pars repair of lumbar spondylolysis with pedicle screw and lamina hook: a clinical and CT-assessed studyThe width of the defect (segment a) is measured on reconstructed sagittal CT image in the middle of the pars interarticularis (A). The distance of the defect to the vertebral body is calculated on axial CT image by the following formula: distance = (c + c’)/2b (B). Angle of the defect (angle d) is the angle between the line of the posterior margin of the vertebral body and the line of the defect on the axial CT image (C)Back to article page