Posterior tibialis tendon tears: comparison of the diagnostic efficacy of magnetic resonance imaging and ultrasonography for the detection of surgically created longitudinal tears in cadavers.

RATIONALE AND OBJECTIVES: The optimal advanced imaging method for detection and characterization of posterior tibialis tendon (PTT) tears is unclear. The purpose of this study was to investigate the utility of ultrasonography (US) and MR imaging in the detection of surgically created PTT tears in cadavers. MATERIALS AND METHODS: This was a prospective blinded study in which 16 fresh cadaveric foot and ankle specimens (3 men, 13 women; average age at death 83.9 years; age range 71-96 years) were scanned with both US and MR imaging before and after the surgical creation of 64 variable length longitudinal tears of the PTT. Ultrasonography was performed with a 12 MHz linear transducer with independent interpretations of static and dynamic studies separately by two blinded and experienced musculoskeletal radiologists. MR imaging was performed at 1.5 T with a standard transmit-receive extremity coil using axial, sagittal, coronal T1-weighted (TR 600, TE 20), and axial fast spin echo proton density and T2-weighted (TR 3000, TE 161/20, ETL 12) images. MR images were reviewed independently by two experienced musculoskeletal radiologists who were blinded to the status of the PTT. RESULTS: Sensitivity, specificity, and accuracy of MR imaging in the diagnosis of PTT tears were 73%, 69%, and 72%, respectively. Dynamic US interpretation yielded values of 69% sensitivity, 81% specificity, and 72% accuracy. Static US interpretation was less reliable than dynamic interpretation, and the only significance of static imaging was a high specificity (94%) for detection of longitudinal tears. The positive predictive value (PPV) for MR imaging and US was 88% and 92% respectively, and the negative predictive value (NPV) was 46% for both MR imaging and US. CONCLUSION: Our results suggest that US and MR imaging perform at the same level for the detection of surgically created longitudinal PTT tears in a cadaveric model. US has a higher specificity compared with MR imaging.

Visualization of ankle tendons and ligaments with MR imaging: influence of passive positioning.

PURPOSE: To determine if passive positioning of the ankle influences the MR imaging appearance of ankle tendons and ligaments. METHODS: A positioning device was used during imaging of 10 volunteers. Axial and coronal T1-weighted images were acquired in six positions of the ankle, and the appearance of the tendons and lateral ligaments was subjectively evaluated. RESULTS: The peroneus longus (PL), peroneus brevis (PB), anterior tibialis (AT), extensor digitorum longus (EDL), and extensor hallucis longus (EHL) tendons were best visualized in 20 degrees of plantarflexion and 20 degrees of inversion (p < 0.0001). The anterior talofibular (ATF) and calcaneofibular (CF) ligaments were best seen in 20 degrees of plantarflexion (p < 0.0001). Ten degrees of dorsiflexion was the least useful imaging plane for all of the aforementioned structures. CONCLUSION: When there is clinical concern regarding pathology of a specific structure about the ankle, passive positioning may allow optimal evaluation.