Sarcomere length varies with wrist ulnar deviation but not forearm pronation in the extensor carpi radialis brevis muscle

Extensor carpi radialis brevis (ECRB) sarcomere length was measured in seve n patients using intraoperative laser diffraction. Sarcomere length was mea sured with the forearm in one of four positions: wrist in neutral with rega rd to radial-ulnar deviation and forearm in neutral rotation, wrist in ulna r deviation and forearm in neutral rotation, wrist in neutral and forearm i n pronation, and wrist in ulnar deviation and forearm in pronation. Two-way ANOVA comparing sarcomere length between the four positions revealed a sig nificant effect of ulnar deviation (p < 0.05), no significant effect of pro nation (p > 0.7) and no significant interaction (p > 0.9). These results de monstrate that the sixes of forearm rotation and wrist radial-ulnar deviati on act independently, at least with regard to the ECRB and have implication s regarding the etiology of tennis elbow. (C) 1999 Elsevier Science Ltd. Al l rights reserved.