title: Wrist kinetics after luno-triquetral dissociation: the changes in moment arms of the flexor carpi ulnaris tendon.
abstract: Wrist biomechanics after luno-triquetral (LT) dissociation is important for understanding the clinical sequelae of the disease and for determining its treatment options. The LT interosseous ligament plays an important role in stabilizing the joint and damage to the ligament would be expected to significantly increase moment arms of tendon of the flexor carpi ulnaris (FCU), the principal ulnar wrist flexor. We investigated the changes in moment arms of FCU tendon after various amounts of sectioning of the ligaments proven to be associated with LT dissociation. In six fresh frozen cadaveric upper extremities, excursions of the FCU tendon were recorded simultaneously with wrist joint angulation during wrist flexion-extension and radioulnar deviation. Tendon excursions were measured in intact wrists, in wrists with sectioning of the dorsal portion of the LT interosseous ligament, in wrists with sectioning of the entire LT interosseous ligament, and finally in wrists with further sectioning of the dorsal radiotriquetral and intercarpal ligaments. Moment arms of the tendon were calculated from tendon excursions and joint motion angulations and expressed as percentage changes from those in the intact wrist. During wrist flexion-extension, moment arms of the FCU tendon after sectioning of the entire LT interosseous ligament and after sectioning of the two capsular ligaments were 112 +/- 7% and 114 +/- 8%, respectively; these values were significantly greater than those in the intact wrist. During radioulnar deviation, the moment arms were 114 +/- 11% after sectioning of the dorsal portion of the LT interosseous ligament, 134 +/- 15% after sectioning of the entire ligament, and 153 +/- 18% after sectioning of the capsular ligaments, again being significantly greater than the normal wrist. Increase in moment arms of the FCU tendon after loss of integrity of the LT interosseous ligament and dorsal capsular ligaments may contribute to clinical sequelae of LT dissociation and difficulty in treating this disorder.
authors.affiliation: Hand Surgery Research Center and Biomechanics Laboratory, Department of Orthopaedics, Affiliated Hospital of Nantong Medical College, 20 West Temple Road, Nantong 226001, Jiangsu, China. hrsc@pub.nt.jsinfo.net
authors.forename: Jin Bo
authors.initials: JB
authors.lastname: Tang
authors.forename: Ren Gou
authors.initials: RG
authors.lastname: Xie
authors.forename: Xiao Wei
authors.initials: XW
authors.lastname: Yu
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002348:Carpal Bones / Q000293:injuries* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007700:Kinetics; D008022:Ligaments / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D013710:Tendons / Q000503:physiopathology*; D014955:Wrist Joint / Q000503:physiopathology*