Quantitative Assessment of Bone Marrow Edema in Adolescent Athletes with Lumbar Spondylolysis Using Contrast Ratio on Magnetic Resonance Imaging

STUDY DESIGN: Prospective cohort study. PURPOSE: To quantitatively evaluate bone marrow edema (BME) in the pedicle on magnetic resonance imaging (MRI) for adolescent athlete patients with spondylolysis. OVERVIEW OF LITERATURE: Spondylolysis, a stress fracture of the pars interarticularis, is a common occurrence in adolescent athletes with low back pain. T2-weighed fat-saturated MRI is reportedly useful for the detection of BME in the pedicle in the early stage of spondylolysis; however, to our knowledge, the quantitative assessment of BME in spondylolysis has not been reported. METHODS: Adolescent athletes with spondylolysis, including those with symptoms of low back pain, were enrolled. The sporting activity of the patients was restricted, and a hard brace was attached to the spine. The BME range of interest was taken on T2-weighed fat-saturated MRI, and the signal intensity (SI) of the BME (SI(edema)) was measured. The contrast ratio (CR) between the SI of the BME and SI of the spinal cord (SI(cord)) was calculated per the following formulae: CR(edema)=(SI(edema)−SI(cord))/(SI(edema)+SI(cord)). The CR of the normal pedicle was measured as a control per the following formulae: CR(control)=(SI(control)−SI(cord))/(SI(control)+SI(cord)). RESULTS: The study enrolled 32 men and one woman; the mean patient age was 15.2 years (range, 12–18 years). The average CR of the edema and normal pedicle at the first visit was 0.506 (range, 0.097–0.804) and 0.137 (range, −0.741 to 0.572), respectively. The CR of the edema was significantly higher as compared to that of the normal pedicle (p<0.01). MRI that was performed 1 month after the first visit showed that the CR of the edema had decreased to 0.204 (range, −0.152 to 0.517). The CR of the edema 1 month thereafter was significantly lower than that at the first visit (p<0.01). CONCLUSIONS: Quantitative assessment of BME using CR on MRI is useful in the evaluation of the healing process of spondylolysis.