Normative data on extensor pollicis longus force, lift-off height, and tendon gliding amplitude

BACKGROUND: The extensor pollicis longus is the principal extensor of the thumb and is typically evaluated in clinical examination with the hand placed flat on a surface. As the hand is commonly immobilized or functions in 20-30 degrees of wrist extension (the functional position), it is important to understand extensor pollicis longus function in both positions. PURPOSE: To establish normative reference values for extensor pollicis longus extension force measured with the hand in flat and functional positions and assess normative values for lift-off height and extensor pollicis longus tendon gliding amplitude. STUDY DESIGN: Cross-sectional study. METHODS: Two hundred healthy individuals (100 males, 100 females; aged 18-85 years, median age 46 years) were included. A custom-made device capable of measuring isolated finger force and recording electromyographic activity was used. Lift-off test height and extensor pollicis longus tendon gliding amplitude were documented. RESULTS: Extensor pollicis longus force peaked in the third decade of life and declined thereafter. In the flat position, the median extension force was 9.3 N (range: 1.1-18.8 N) for females and 15.8 N (range: 6.4-33.0 N) for males. In the functional position, the median values were 14.0 N (range: 3.8-35.2 N) for females and 21.2 N (range: 6.4-50.6 N) for males. Lift-off height was comparable between the sexes, with median values from 46 to 48 mm (range: 10-75 mm). Likewise, gliding amplitude exhibited no differences between the sexes, with a median of 30 mm (range: 5-50 mm). CONCLUSIONS: Reference values for extensor pollicis longus extension force, lift-off height, and tendon gliding amplitude were established. Maximal force occurs at 30 degrees wrist extension, peaks in the third decade, and declines after the fourth. On average, force values in females were approximately 60% of those observed in males.