BIOMECHANICAL STABILITY OF ABDUCTOR POLLICIS LONGUS MUSCLES WITH VARIABLE NUMBERS OF TENDINOUS INSERTIONS

Background: In the course of a study of different variants of the tend on of the abductor pollicis longus (APL) muscle, the unusual finding o f a tendon with six subdivisions was observed in the first compartment , Using this preparation and others with various numbers of tendons (2 , 3, 4, and 6), we intended to establish whether the multitendoned mus cles increased the strength of the thumb. Methods: Fifty-two upper ext remities were examined with attention to the tendons of the APL muscle , The strain on each tendon was biomechanically determined using a mic rocomputer and potentiometer. The stress was measured continously and plotted against strain. Results: Following treatment with elastase, it is seen that the significance of changes in stability and Young's mod ulus is inversely proportional to the number of tendons arising from t he APL. Conclusions: Division of the tendon into several parts leads t o better mechanical distribution of stress and extension on thumb abdu ction, In addition, palmar-flexion in the wrist may be supported. (C) 1998 Wiley-Liss, Inc.