High-resolution MR imaging of the asymptomatic Achilles tendon: New observations

OBJECTIVE. Our aim was to describe the normal appearance of the Achilles te ndon and peritendinous tissues in asymptomatic active volunteers using high -resolution MR imaging. MATERIALS AND METHODS. One hundred clinically asymptomatic Achilles tendons were imaged at 1.5 T with axial high-resolution T1-weighted gradient-echo (fast low-angle shot [FLASH]) and short inversion time inversion recovery ( STIR) sequences, The tendons, peritendinous tissues, tendon insertions, and musculotendinous junctions were separately evaluated by two observers. RESULTS. The average anteroposterior diameter (+/-SD) of the asymptomatic A chilles tendons was 5.2 +/- 0.73 mm, The anterior margin was flat or concav e in all, except for 10 tendons that showed mild convexity. A wavelike bulg e, which shifted from lateral to medial in the craniocaudal direction, was detected in the anterior margin of 56 tendons. The signal intensity was het erogeneous in 45 tendons. In these tendons, distal stripes or punctate foci were seen. A small (3 mm) intermediate intensity intratendinous region tho ught to represent tendon degeneration was detected in four cases on FLASH i mages. The retrocalcaneal bursae contained a prominent fluid collection in 15 cases. The paratenon was visualized in all cases on both FLASH and STIR images. CONCLUSION. High-resolution MR imaging depicts the Achilles tendon and peri tendinous soft tissues in great detail. The normal anatomy of the asymptoma tic Achilles tendon is variable. We postulate that the variability may be a potential source of diagnostic misinterpretation.