Diagnosis of digital flexor tendon annular pulley disruption: comparison of high frequency ultrasound and MRI.

PURPOSE: The objective of this study is to assess accuracy of ultrasound (US) and MRI to diagnose completely disrupted annular pulley ligaments (APL) of the flexor tendons of the fingers.

PATIENTS AND METHODS: In a prospective study 32 patients (all males 18-42 years, mean age 25 years) with clinically suspected annular pulley disruption were studied with US and MRI. As a control group we investigated 40 fingers of 10 healthy volunteers and a non-injured finger of the patients with US. A 10 MHz linear array was used for US examinations and a 1.5 Tesla unit for MRI. Imaging was performed between the accident and surgical repair within 6 weeks. Examinations were performed in an extended and forced flexed finger position.

RESULTS: Complete disruption of the APL was diagnosed by US and MRI in 14 cases confirmed by surgery. The typical sign of disruption was a marked volar displacement of the flexor tendon in the area of the torn annular pulley during forced flexion. A distance between tendon and bone at the area of the ruptured pulley of 3 mm during extension and a distance of 5 mm at flexion was typical for complete disruption.

CONCLUSION: Both diagnostic modalities, US and MRI are valuable techniques in diagnosing complete disrupted annular pulleys of the flexor tendons.