An anatomic study of the effect of proximal interphalangeal joint motion on the tension of the extensor tendon in zone I and II

Abstract

Objective To investigate the effect of proximal interphalangeal joint (PIPJ) motion on the tension of the extensor tendon in zone Ⅰ and Ⅱ. Methods The maximum passive flexion angles of the distal interphalangeal joint (DIPJ) of the index, middle, ring and little fingers were measured in 10 fresh cadaver hands with the PIPJ flexed at 0, 45° and 90°. An incision was made over the dorsum of the DIPJ to expose the extensor tendon in zone Ⅰ and Ⅱ. A mallet finger was created by incising the extensor tendon transversely at the level of the DIPJ while the DIPJ was fixed in extension position. A Kirschner wire was inserted through and perpendicular to the middle phalangeal neck as a landmark. Parallel to this land mark, extensor tendon in zone Ⅰ and Ⅱ was marked and its relative distance to the landmark was measured as the gliding distance of the extensor. The broadest gap between the tendon edges and the tendon gliding distance were recorded while the PIPJ was in extension and 90° flexion position, respectively. Results The maximum passive flexion angle of the DIPJ increased when the PIPJ flexed from 0° to 90°. The gap between the extensor tendon edges in zone Ⅰ and Ⅱ was (0.43±0.07) mm while the PIPJ was in extension position. The proximal extensor tendon slid distally when the PIPJ flexed to 90° with an average gliding distance of (0.76±0.07) mm. Conclusion Extensor tendon in zone Ⅰ and Ⅱ has the maximum tension when the PIPJ is in extension position. Flexing PIPJ can decrease the tension. Key words: Anatomy; Biomechanics; Interphalangeal joint; Mallet finger