Partial rupture of the proximal Achilles tendon: a differential diagnostic problem in ultrasound imaging.

OBJECTIVES The aim of this study was to determine whether ultrasound can correctly visualise partial ruptures of the proximal Achilles tendon. METHOD This was a prospective study in which all chronic Achilles tendon injury patients seen at three centres in Germany from 1998 to 2003 were screened. All patients with clinical and/or sonographic signs of abnormalities in the region of the proximal third of the Achilles tendon and tendomuscular junction were included in the analysis. Each of these cases was evaluated by ultrasound following an assessment protocol. Patients with ambiguous ultrasound findings and/or clinical signs were additionally assessed by magnetic resonance imaging (MRI). RESULTS Sonomorphologic changes suggestive of an abnormality in the proximal third of the Achilles tendon were detected in 13 out of 320 patients (4.2%) with recurring Achilles tendon complaints. Thirteen patients had clinical signs but no sonographic changes in the tendon. The sonographic diagnosis was correct in 19 cases. In six of the 26 cases studied, MRI was needed to establish the correct diagnosis of partial intratendinous rupture of the proximal Achilles tendon. Sensitivity was 0.5, specificity was 0.81, and the overall agreement of the ultrasound examination was 61.5%. All patients were asymptomatic at follow up at a mean of 14 months (range 12-17 months) after surgery. CONCLUSIONS Ultrasound is a useful tool for evaluation of proximal Achilles tendon complaints. However, ultrasound is not sufficiently reliable for diagnosis of all pathologies, especially partial ruptures of the Achilles tendon. Thus, the definitive diagnosis must be established by MRI.