Study design: Experimental laboratory design.
Objectives: To measure the strain at the proximal origin of the extensor carpi radialis brevis (ECRB), and to determine the influence of a forearm support band.
Background: A forearm support band is often used with the intent to decrease stresses around the origin of the wrist extensors. However, the influence of the location of the band has not been studied.
Methods and measures: The forearm support band was applied on 8 cadaver arms (mean +/- SD age, 78.4 +/- 10.3 years) and 2 experimental conditions were performed. First, strain measurements were made without applying tension to the distal ECRB tendon, then strain measurements were made with a traction force of 21.5 N being applied to the distal ECRB tendon. Strain of the proximal origin of the ECRB, 1.0 cm distal from the lateral epicondyle, was recorded using a strain gauge. The band was mounted on the forearm at distances equal to 80%, 70%, 60%, 50%, 40%, 30%, and 20% of the forearm length as measured from the wrist. Testing order was randomized. Tension applied to the band was 19.6 N.
Results: When no tension was applied to the ECRB, there was no statistically significant difference (P>.05) in strain values at the ECRB origin by mounting the band at any of the forearm positions. In the tension condition, the average (SD) strain with no band was 2.40% (1.40%). The average strain value of 0.85% (0.65%), when the band was mounted 80% of the forearm length proximal to the wrist, was statistically smaller than that obtained without the band (P<.05).
Conclusions: The strain on the ECRB origin was less when the forearm support band was applied 80% proximal from the wrist joint.
Level of evidence: Therapy, level 5.