Ligaments of the Wrist


Radial extrinsic ligaments



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Radial extrinsic ligaments

  1. Radioscaphocapitate

    1. arises from the volar lip of the radius and inserts on the waist of the lateral scaphoid, the waist of the capitate, and coalesces ulnarly with the ulnocapitate ligament to form the arcuate or deltoid ligament.

    2. forms a sling over which the scaphoid bows into flexion during radial deviation;

    3. radiocapitate ligament is the primary stabilizer of capitolunate joint, and is the primary stabilizer of the distal carpal row on proximal carpal row.

  2. Long radiolunate (radiolunatotriquetral) ligament lies ulnar to the RSC ligament

    1. arises from the volar lip of the radius and courses across the proximal pole of the scaphoid to attach to the volar lip of the lunate and then terminates on the triquetrum

  3. Radioscapholunate: (ligament of Testut);

    1. orignates from volar aspect of the interfossa ridge between scaphoid & lunate fossae & inserts into scapholunate interosseous ligament

    2. is not a true extrinsic ligament of wrist

    3. vascular structure devoid of any true collagen fibers and lacking structural integrity.

    4. acts as neurovascular supply to scapholunate interosseous membrane and

  4. Short radiolunate (SRL) ligament

    1. arises from the radius adjacent to the lunate fossa and inserts on the volar lip of the lunate, coalescing with the LRL, ulnolunate, and volar lunotriquetral ligaments

    2. believed to be one of the more important stabilizers of the lunate as it is the ligament that maintains the position of the lunate adjacent to the radius after a perilunate dislocation



Ulnar extrinsic ligaments

  1. ulnolunate

  2. ulnocapitate

    1. insert on the waist of the capitate and to join the RSC, forming an inverted V (arcuate ligament)

  3. ulnotriquetral

    1. this is a key ligament along with the TFC;
                          - on occassion, may avulse from its insertion on the lunate, and this injury will allow dye extension both into the distal RU joint and into the mid-carpal joint;
         


Proximal row Intrinsic ligaments

  1. scapholunate interosseous ligament

    1. C-shaped ligament attaching proximally from volar to dorsal

    2. divided into 3 separate components

    3. dorsal portion of this ligament supplies the majority of stabilizing strength to the scapholunate articulation.

    4. central portion of the interosseous ligament is relatively thin and termed the intramembranous portion

  2. lunotriquetral interosseous ligament

    1. secures the articulation of the lunate and the triquetrum.

    2. Like the SLIL, the LTIL is C shape and has 3 components – volar, intramembranous and dorsal

    3. Unlike the SLIL, the volar portion is stronger


Distal row Intrinsic ligaments

  1. capitohamate ligament

    1. composed of dorsal, deep, palmar, and longitudinal components.

  2. The scaphotrapeziotrapezoidal (STT) joints are stabilized by a ligamentous complex that is both intrinsic and extrinsic in nature. These ligaments include the scaphotrapezial ligament, a scaphocapitate capsular ligament, and the dorsal and palmar STT capsular ligaments.



Space of Poirier

  • volar part of capsule of wrist has area of weakness, called space of Poirier;

  • lies between 2 ligamentous arcs

    • proximally – radiolunotriquetral

    • distally by radioscaphocapitate/ulnotriquetral (arcuate ligament) and triquetrohamatocapitate

  • area expands when wrist is dorsiflexed & disappears in palmar flexion;

  • rent develops during dorsal dislocations, & it is thru this defect that lunate displaces into the carpal canal in perilunar dislocations;



Dorsal Wrist Ligaments



  • usually of little significance in trauma as occurs with wrist dorsiflexion

  • importance is dorsal radiocarpal ligament in rheumatoid arthritis




  1. dorsal radiocarpal ligament

    1. originates from the distal radius at Lister's tubercle.

    2. deep fibers attach to the dorsal horn of the lunate and its superficial component courses to attach to the dorsum of the triquetrum.

  2. dorsal intercarpal ligament

    1. originates on the triquetrum

    2. courses radially as it fans out to insert on the dorsal ridge of the scaphoid, the trapezium, and the trapezoid

    3. deep portion of the DIC also augments the scapholunate and lunotriquetral interosseous ligaments.




  • Together, these two ligaments form a V, with the base of the V on the triquetrum. Between the limbs of the V is the less substantial dorsal wrist capsule which is useful for surgical exposures of the radiocarpal joint



Carpal Kinematics
Range of motion

  • 3 axis of motion

    • Flex – Extend  80-70

      • In extension: radiocarpal 66% midcarpal 34%

      • In flexion: radiocarpal 40% midcarpal 60%

      • Axis of rotation is at the proximal part of capitate

    • Radial-Ulnar  20-50

      • Axis of rotation moves between proximal capitate and midscaphoid

    • Pronate-Supinate  90-90

      • 90% occurs at radio-ulnar; 10% at radiocarpal and intercarpal

      • Axis of rotation at the ulnar fovea (base of styloid)

  • Fusion

    • radiocarpal joint  55% loss of wrist motion

    • across carpal row  25% loss of wrist motion

    • within carpal row  10% loss of wrist motion

      • arthrodesis of LT and CH results in the least loss


Kinematics

  • In effect, there are no tendons that attach directly to the carpal bones

  • tendons that primarily move the wrist insert on the base of the metacarpals

  • Distal row moves first. There is little motion between bones of the distal row

  • Motion of the proximal carpal row is dependent on the tautness of the ligamentous attachments and the compressive forces of the distal carpal row

  • Although there is some motion between the bones of the proximal row, it normally moves synergistically.

    • When the wrist is flexed, the proximal carpal row flexes and radially deviates.

    • With the wrist in extension, the proximal carpal row extends and ulnarly deviates.

  • Theories

  1. Row theory

  • Anatomic division between proximal and carpal row

  1. Column theory

  • recognizes some motion between the bones of the proximal row

  • does not explain the coupled motions that occur within the proximal and distal rows, it does help explain the load patterns seen through the wrist

  • Navarro divided the wrist into 3 column:

  1. radial column-scaphoid, trapezium, and trapezoid

  • load bearing

  1. central column-lunate, capitate and hamate

  • flexion, extension

  1. ulnar column- triquetrum and pisiform

  • pronation-supination

  • Taleisnik modification

  1. radial column-scaphoid

  2. central column-lunate, hamate, capitate, trapezium, trapezoid

  3. ulnar column- triquetrum

  1. Oval-ring concept (Lichtman)

  • 4 components

  1. Scaphoid

  2. Lunate

  3. Triquetrum

  4. Distal row


Force Transmission


  • At midcarpus: 60% of load borne by capitate-scaphoid-lunate joint

  • At radiocarpal: 50% through scaphoid fossa of radius, 30% across lunate fossa and 20% through TFCC


Stabilizing Mechanisms of the Wrist


  • Distal carpal row

    • Bones tend to displace in diverging directions

    • Stabilised by intercarpal ligaments

  • Midcarpal joint

    • With axial load, proximal row tends to flex and pronate

    • Stabilised by arcuate ligament

    • Scaphoid acts as a link-joint



  • Proximal carpal row

    • Restrained by the SL and LT interosseous ligament

  • Radiocarpal joint

    • Restrained by

      • Dorsal radiocarpal ligament

      • Radioscaphocapitate and long radiolunate ligaments

      • TFCC



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