Spondylolysis is a congenital or acquired defect in the pars interarticularis. It may or may not have the associated slippage of the involved vertebral bodies upon one another (spondylolisthesis). Although many are clinically silent, with the absence of pain some suffer low back pain, gait abnormalities and neurologic deficits. The fifth vertebral body is the most commonly affected. Unfortunately as of yet, it is difficult to determine which patients will develop spondylolisthesis and which will not. To further complicate matters many will be asymptomatic.
Bone scintigraphy aids in the evaluation of the lesions to determine the if the lesion is recently acquired (w/ accumulation of radiotracer on the same side of the lesion) versus which lesions are chronic and producing reactive sclerosis of the contralateral side that may not yet be radiographically evident.