INTRODUCTION: A recent study reported that high signal change (HSC) on T2‐MRI in the pedicle adjacent to the pars interarticularis could be an indicator of early spondylolysis. In addition, the HSC‐positive pars defects showed significant better bony healing than the HSC‐negative pars defects. However, there has been no report on the time course and the duration of HSC. In this study, we prospectively investigated the time course of signal changes in the adjacent pedicle in acute pediatric lumbar spondylolysis.
METHODS: We investigated 10 boys and 5 girls with acute lumbar spondylolysis showing HSC in the adjacent pedicle. Their mean age was 15.1 years, ranging from 10 to 17 years. Two patients had multi‐level unilateral spondylolysis. Among 15 patients, HSC was found in 22 (12 unilateral, 5 bilateral) pedicles. At the first presentation, the diagnosis of spondylolysis was made based on plain X‐ray findings, multi‐detector CT, and MRI. Every month from the first presentation, follow‐up MRIs were taken. When HSC disappeared, multi‐detector CT was taken to confirm bony healing of the pars defect.
RESULTS and DISCUSSION: Bony healing of the pars was obtained in 21 out of 22 defects. The bony healing rate was 95.6%. In 19 pedicles of 12 patients, HSC gradually diminished by every month until it disappeared 3 months later, and radiological osseous healing was confirmed by CT in all but one patient. In the 3 remaining pedicles of 3 patients who did not comply with treatment, HSC took more than 4 months to disappear. These results led us to hypothesize that MRI at the third month during follow up can indicate whether the conservative treatment is being successful or not.