Imaging assessment of pars interarticularis injury in young athletes with back pain: current concepts and imaging methods

Injury of the pars interarticularis is a common cause of low back pain, particularly in adolescent athletes. It is a spectrum of disease where repetitive bone stress and micro-trauma create an unstable fracture of the pars interarticularis (spondylolysis) that can ultimately lead to slippage of one vertebral body on another (spondylolisthesis). Radiographs are typically the initial study performed to evaluate patients with low back pain from suspected pars interarticularis injury and may identify structural abnormalities as well as the extent of vertebral body slippage. MRI may be helpful in certain cases since it is sensitive for soft tissue disease and can exclude other causes of back pain such as degenerative disk disease, infection or malignancy, although these are rare in young athletes. Skeletal scintigraphy is helpful in the evaluation of pars interarticularis injury since bone stress is the earliest form of disease and may be present before structural changes have occurred or are detected by anatomic imaging. Furthermore, patients with bone stress who have not yet developed structural abnormalities can receive early intervention with high probability of a good outcome. Skeletal scintigraphy should include planar images as well as single photon emission computed tomography (SPECT) of the spine. SPECT of the spine has greater contrast and sensitivity than planar skeletal scintigraphy and provides better anatomic localization of bone stress. Spine CT is helpful for the evaluation of patients with suspected pars interar ticularis injury since it provides high-resolution anatomic detail, confirms the diagnosis, identifies spondylolysis and evaluates the extent of ver tebral body slippage.