Thickness of extensor tendons at the proximal intersection: sonographic measurements in asymptomatic volunteers

OBJECTIVES:
An important sign of proximal intersection syndrome is thickening of the tendons at the area where the first extensor compartment tendons cross over the second compartment. Normal values for the thickness of the tendons have not been reported. Our purpose was to measure the thickness of the tendons with sonography at the level of the intersection in healthy volunteers and assess differences between men and women, dominant and nondominant sides, and different tendons.
METHODS:
Forty-one asymptomatic volunteers (25 women and 16 men) were examined by 2 radiologists experienced in musculoskeletal sonography. The thickness of the tendons in the first and second compartments was measured at their intersection at standardized proximal and distal levels. Descriptive statistics were obtained. Differences between men and women, dominant and nondominant sides, and different tendons were evaluated by a Student t test.
RESULTS:
The 95% confidence intervals for measurements of superimposed tendon groups varied between 0.30 and 0.40 cm in women and between 0.36 and 0.48 cm in men. There were no statistically significant differences in comparisons of the different tendon groups (P > .05). There were statistically significant differences (P <.05) between tendon thickness in men and women except for the right extensor carpi radialis longus + abductor pollicis longus (proximal measurement) and extensor carpi radialis brevis + extensor pollicis brevis (distal measurement). On comparison of dominant and nondominant sides, there were no statistically significant differences.
CONCLUSIONS:
Normal tendon thickness should be between 0.30 and 0.40 cm in women and 0.36 and 0.48 cm in men. A comparison between asymptomatic and symptomatic sides and proximal and distal measurements is recommended.