Value of Transducer Positions in the Measurement of Finger Flexor Tendon Thickness by Sonography

OBJECTIVE: To assess the value of 2 transducer positions for measurement of finger flexor tendon thickness by sonography. METHODS: Flexor tendon thickness of the third finger was measured sonographically by 2 independent investigators in 20 healthy volunteers (n = 40 fingers) and in 4 cadaveric specimens (n = 4 fingers). Flexor tendon thickness was measured at histologic examination in the cadaveric specimens. We defined the area of the A1 annular pulley as position I and the area of the A2 annular pulley as position II. Sonographic measurements were performed in transverse (dorsovolar and radioulnar) and longitudinal planes. Interobserver and intraobserver variabilities were evaluated by each investigator performing 3 measurements at each position. RESULTS: In position I, volunteers had flexor tendon thickness of 2.7 to 4.0 mm (mean +/- SD, 3.28 +/- 0.26 mm) longitudinally; transversally the thickness was 2.5 to 4.0 mm (mean, 3.34 +/- 0.29 mm) dorsovolar and 5.5 to 8.9 mm (mean, 7.34 +/- 0.71) radioulnar in position I. Position II revealed thickness of 3.2 to 4.2 mm (mean, 3.6 +/- 0.23 mm) longitudinally; transversally the thickness was 2.7 to 4.1 mm (mean, 3.4 +/- 0.27) dorsovolar and 4.3 to 6.8 mm (mean, 5.27 +/- 0.65) radioulnar. Interobserver and intraobserver variability for position I was better than for position II (P < .01 versus P < .05). Sonographic findings correlated excellently with histologic findings (r2 = 0.94). CONCLUSIONS: Standardized transducer positions for sonographic measurements of finger flexor tendon thickness showed good interobserver and intraobserver variability. Position I was found to be more reliable than position II.