The Isthmic Defect in the Lumbar Spine:Evaluation with Computed Tomogrphy(CT)
Zhang Yunting; Ji Shengzhang;Bai Renhui;Wu Enhui.(Tianjin Medical University General Hospital,Tianjin 300052)
To evaluate the CT findings of the isthmic defect in the lumbar spine and to discuss the diagnosis as well as differential diagnosis of this abnormality.Materials and Methods:Twenty-three patients were scanned with axial CT using 4～5mm slice thickness parallel to the intervertebral space. The scan region was from the inferior surface of the vertebral body above the pathological site to the superior surface of the vertebral body below the pathological site. 2mm slice thickness of axial scans were also performed if necessary. Results:The CT scans revealed an irregular band of lower density which represented the isthmic defect located between the ipsilateral articular processes at the level of inferior margin of the pedicle. In 21 cases the defect was bilateral.while in 2 cases it was unilateral.The isthmic defects were found at L5 in l6 cases and at L4 in 7.The combined findings included spondylolisthesis(19),deformity of the spinal canal(19),hypertrophy of the intervertebral joints(17),stenosis of the lateral recess(6),thickening ofthe ligamentum flavum(15),degeneration of adjacent disk(10),spondyloschisis(4),dysplasia of vertebral arch(1)respectively. Conclusion:CT should be considered as the primary choice not only for demonstration of the isthmic defect in the lumbar spine but also for the evaluation of its complicated conditions.