Where is the defect in spondylolysis located?

Where is the defect in spondylolysis located?

• A. Between the superior and inferior articular processes
• B. In the pars interarticularis
• C. In the pedicle
• D. In the lamina

Answer: (B)

Spondylolysis is a defect caused by a stress fracture through the pars interarticularis of a vertebra. The pars interarticularis is the narrow part of the vertebral arch that lies between the superior and inferior articular processes. This location is especially vulnerable to repetitive extension and rotational stresses, which is why athletes—especially kids and adolescents—can develop a fracture here. That makes the pars interarticularis the correct site to identify for spondylolysis. While saying it lies “between the superior and inferior articular processes” points to the same region, the precise anatomical term used is pars interarticularis, which is why it is the best answer. The pedicle and lamina are other parts of the posterior vertebra but are not the usual sites of this defect. On imaging, pars defects are classically looked for on oblique views, sometimes described with the “Scottie dog” sign where the defect appears as a collar on the dog.

Spondylolysis is a defect caused by a stress fracture through the pars interarticularis of a vertebra. The pars interarticularis is the narrow part of the vertebral arch that lies between the superior and inferior articular processes. This location is especially vulnerable to repetitive extension and rotational stresses, which is why athletes—especially kids and adolescents—can develop a fracture here.

That makes the pars interarticularis the correct site to identify for spondylolysis. While saying it lies “between the superior and inferior articular processes” points to the same region, the precise anatomical term used is pars interarticularis, which is why it is the best answer. The pedicle and lamina are other parts of the posterior vertebra but are not the usual sites of this defect. On imaging, pars defects are classically looked for on oblique views, sometimes described with the “Scottie dog” sign where the defect appears as a collar on the dog.