Wrist Planes of Motion Joints involved radiocarpal intercarpal Three axes of motion flexion-extension radial-ulnar deviation prono-supination Normal and function motion flexion (65 normal, 10 functional) 40% radiocarpal, 60% midcarpal extension (55 normal, 35 functional) 66% radiocarpal, 33% midcarpal radial deviation (15 normal, 10 functional) 90% midcarpal ulnar deviation (35 normal, 15 functional) 50% radiocarpal, 50% midcarpal Wrist Biomechanics Three biomechanic concepts have been proposed: Link concept three links in a chain composed of radius, lunate and capitate head of capitate acts as center of rotation proximal row (lunate) acts as a unit and is an intercalated segment with no direct tendon attachments distal row functions as unit advantage efficient motion (less motion at each link) strong volar ligaments enhance stability disadvantage more links increases instability of the chain scaphoid bridges both carpal rows resting forces/radial deviation push the scaphoid into flexion and push the triquetrum into extension ulnar deviation pushes the scaphoid into extension Column concept lateral (mobile) column comprises scaphoid, trapezoid and trapezium scaphoid is center of motion and function is mobile central (flexion-extension) column comprises lunate, capitate and hamate luno-capitate articulation is center of motion motion is flexion/extension medial (rotation) column comprises triquetrum and distal carpal row motion is rotation Rows concept comprises proximal and distal rows scaphoid is a bridge between rows motion occurs within and between rows Carpal Relationships Carpal collapse normal ratio of carpal height to 3rd metacarpal height is 0.54 Ulnar translation normal ratio of ulna-to-capitate length to 3rd metacarpal height is 0.30 Load transfer distal radius bears 80% of load distal ulna bears 20% of load ulna load bearing increases with ulnar lengthening ulna load bearing decreases with ulnar shortening Wrist Ligaments The ligaments of the wrist include extrinsic ligaments bridge carpal bones to the radius or metacarpals include volar and dorsal ligaments intrinsic ligaments originate and insert on carpal bones the most important intrinsic ligaments are the scapholunate interosseous ligament and lunotriquetral interosseous ligament Characteristics volar ligaments are secondary stabilizers of the scaphoid volar ligaments are stronger than dorsal ligaments dorsal ligaments converge on the triquetrum Space of Poirier center of a double "V" shape convergence of ligaments central weak area of the wrist in the floor of the carpal tunnel at the level of the proximal capitate between the volar radioscaphocapitate ligament and volar long radiolunate ligament (radiolunotriquetral ligament) wrist palmar flexion area of weakness disappears wrist dorsiflexion area of weakness increases in perilunate dislocations, this space allows the distal carpal row to separate from the lunate in lunate dislocations, the lunate escapes into this space Extrinsic Ligaments Volar radiocarpal ligaments radial collateral radioscaphocapitate at risk for injury with excessively large radial styloid from radial styloid to capitate, creating a sling to support the waist of the scaphoid preserve when doing proximal row carpectomy acts as primary stabilizer of the wrist after PRC and prevents ulnar drift long radiolunate also called radiolunotriquetral or volar radiolunate ligament counteracts ulnar-distal translocation of the lunate abnormal in Madelung's deformity radioscapholunate Ligament of Testut and Kuentz only functions as neurovascular conduit not a true ligament does not add mechanical strength short radiolunate stabilizes lunate Volar ulnocarpal ligaments ulnotriquetral ulnolunate ulnocapitate Dorsal ligaments radiotriquetral must also be disrupted for VISI deformity to form (in combination with rupture of lunotriquetral interosseous ligament rupture) dorsal intercarpal (DIC) radiolunate radioscaphoid Intrinsic (Interosseous) ligaments Proximal row scapholunate ligament primary stabilizer of scapholunate joint composed of 3 components dorsal portion thickest and strongest prevents translation volar portion prevents rotation proximal portion no significant strength disruption leads to lunate extension when the scaphoid flexes creating DISI deformity lunotriquetral ligament composed of 3 components dorsal volar proximal disruption leads to lunate flexion when the scaphoid is normally aligned creating VISI deformity (in combination with rupture of dorsal radiotriquetral rupture) Distal row trapeziotrapezoid ligament trapeziocapitate ligament capitohamate ligament Palmar midcarpal scaphotrapeziotrapezoid scaphocapitate triquetralcapitate triquetralhamate
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Login to View Community Videos Login to View Community Videos Frontiers in Upper Extremity Surgery Case Presentation #1 (Frontiers #8, 2016) Hand - Wrist Ligaments & Biomechanics 2/20/2017 299 views
Transcaphoid perilunate luxation (C1744) Hand - Wrist Ligaments & Biomechanics HPI - Patient fell down the stairs, no other complaints apart from the painfull left wrist. How would you treat? 1/4/2014 643 1 10