Effects of forearm muscles on carpal stability

Abstract

Thirty cadaveric forearms were tested using a wrist testing apparatus specifically designed to investigate the mechanisms of muscle stabilization of the wrist. The specimens were set in a jig allowing the distal row to migrate proximally and to rotate around the pronosupination forearm axis. Five wrist motor tendons (FCR, FCU, ECU, ECRL and APL) were loaded with specific weights. Reactive rotations of the scaphoid, triquetrum and capitate were measured by an electromagnetic motion tracking device. When all five tendons were loaded simultaneously, the capitate supinated and the proximal row predominantly supinated and flexed. By contrast, when the ECU was loaded in isolation, it caused pronation to both proximal and distal rows. The FCR exhibited a mixed effect pronating the capitate and triquetrum, whilst supinating the scaphoid. Based on this, a hypothesis is proposed linking wrist stability to the balance of wrist pronators (ECU and FCR) and supinators (FCU, ECRL and APL).

Orthotic intervention incorporating the dart-thrower's motion as part of conservative management guidelines for treatment of scapholunate injury

“…They were all fitted with a custom-made DTM orthosis and then followed a program that was based on biomechanical studies and proposed rehabilitation guidelines. [20][21][22]26,37 This program successfully resolved symptoms in all patients. The DTO was able to isolate active movement to a path that protected the SLIL, 21 while providing stability by activating the secondary stabilizers.…”

Understanding Wrist Mechanics: A Long and Winding Road

“…So we decided to do our own testing. With one of my doctoral fellows, Guillem Salvá, 28,29 we completed a cadaver study in which we loaded the FCR tendon while holding the hand in neutral position. Scaphoid displacements were monitored using a highly accurate electromagnetic motion-tracking system.…”

In-vivoconfirmation of the use of the dart thrower’s motion during activities of daily living

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