A 14-yr-old, right-handed, male baseball pitcher presented for evaluation of 1 mo of low-back pain. The pain was primarily right sided and was exacerbated by the cocking phase of pitching and the follow-through phase of batting. He rested from pitching for several weeks, but the back pain recurred when he resumed baseball. He denied acute injury, trauma, or neurologic symptoms. On physical examination, the patient had normal posture and spinal alignment and was nontender. He had full range of motion of the spine, but pain at the extreme of lumbar extension, particularly with addition of right rotation. Musculoskeletal and neurologic examinations were normal, as were lumbar spine x-rays. Lumbar spine magnetic resonance imaging (MRI) with short tau inversion recovery sequences (Fig. 1) showed bony edema in the L3 pedicles bilaterally, extending into the lamina, without fracture. The predominance of symptoms on the right side was likely attributable to increased spinal extension loading during the wind-up phase of right-handed pitching. The patient was advised to avoid baseball playing and any other pain-exacerbating activities for 1 mo. When he returned to clinic for follow-up, he was pain free and had a normal examination. He was given a prescription for physical therapy to address core strengthening, and he was advised to gradually return to his previous level of activity.
The MRI confirmed the clinically suspected diagnosis of bony stress reaction. The timing of advanced imaging in this case was critical. Early diagnosis guided treatment recommendations and helped avoid progression to fracture. The patient was advised to not “play through the pain” but to strictly avoid any exacerbating activities until he had pain-free full range of motion. Sports involving repetitive spinal extension (e.g., pitching, football, and gymnastics) predispose to stress reaction of the posterior elements of the spine, most commonly the pars interarticularis, but also the pedicle. If an athlete remains undiagnosed and continues with activities that load the spine in extension, stress reaction may lead to fracture with resultant pain, instability, and inability to return to sport.
When evaluating adolescent athletes with low-back pain, physicians need to have a high index of suspicion for bony stress reaction and spondylolysis, and they should know which specific imaging studies to order. On MRI, high signal intensity (indicating edema) may be seen on T2 sequences with fat suppression and on short tau inversion recovery images. Abnormalities may not be appreciated on T1 sequences or if images slices are not lateral enough to include the pedicle, pars, and lamina. Increased signal uptake can also be appreciated on bone scan with single photon emission computed tomography. Both MRI and bone scan with single photon emission computed tomography may reveal abnormalities before development of fracture. Spondylolysis is better evaluated on T1 sequences of MRI or on computed tomography scan. MRI has the advantages of evaluating for other sources of pain or pathology (e.g., intervertebral disc) and avoiding ionizing radiation. However, some experts recommend bone scan with single photon emission computed tomography plus computed tomography as the imaging study of choice.
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