Ultrasound detection of heel enthesitis: A comparison with magnetic resonance imaging

Objective. Seronegative arthropathies are associated with inflammatory enthesopathy. The involvement of Achilles tendon and plantar aponeurosis is common, with strong tendency toward fibrosis and calcification. This study tests the diagnostic efficacy of ultrasound (US) in depicting enthesitis, and compares sonographic images with magnetic resonance images (MRI). Methods. We studied 32 patients with a diagnosis of seronegative arthropathies, 22 men, 10 women, mean age 29 years. They had heel enthesopathy without typical conventional radiographic evidence. T1 and T2 weighted and short-tau inversion recovery (STIR) MRI sequences were obtained in axial and sagittal planes. An HDI 3000 ATL US device equipped with 12 MHz linear transducer was used to examine the enthesis. Three independent observers assessed the reliability of sonographic images by using video recording of the US examinations. Results. US images of enthesitis. showed loss of normal fibrillar echotexture of tendon (100%), lacking the homogeneous pattern, with blurring of tendon margins (56.2%) and irregular fusiform thickening (84.3%). The affected tendons showed intratendinous lesions with ill defined focal tendon defects filled with a mixture of fluid, fat, and/or granulation tissue, with loss of their tightly packed echogenic dots. MRI showed tendon enlargement (62.5%) With loss of the normal flattened hypointense appearance, focal thickening and rounded configuration at the insertion site (31.2%), intermediate T1 and high T2 signals, and diminished signals within the pre-Achilles fat pad due to inflammatory edema. Among all patients, 40.6% developed osteitis. Conclusion. MRI was not sensitive compared to US in detecting early changes of enthesopathy. Fatty degeneration appeared late in MRI, while it was detected earlier using US. MRI was not able to detect any calcification process at the insertion site, while US images clearly showed the very early signs of the calcification process. We recommend use of US for early diagnosis and in treatment and followup of patients with tendon enthesopathy, to accurately identify and diagnose different pathologic and biomechanical changes.