Wrist

Scapholunate ligament

  • Volar part (trapezoidal shaped)

  • Interosseous membranous component (triangular shaped)

    • Common to see signal in it and have asymptomatic tears

  • Dorsal part = strongest (striated-band shaped)

  • SLD & LTV

    • Scapholunate - dorsal is strongest

    • Lunate-triquetral - volar is strongest

Volar rhomboidal shaped

Ulnar Variance

Negative Ulnar Variance

  • Ulnar lower than radius at DRUJ

  • Associated with

    • Lunate osteonecrosis

    • Ulnar impingement

Interosseous Membranous (triangle shaped)

Scaphoid

  • Lots of pathology with this little bone

  • Gets retrograde blood flow (from distal hand to proximal)

    • Therefore the proximal aspect is last to get blood and therefore more likely to get AVN

    • Prieser disease = atraumatic AVN of scaphoid

  • Fractures

    • Most commonly fractured at the waist

    • Displacement >1 mm = likely surgical fixation

    • Associated with perilunate dislocation

    • Humpback deformity

      • Scaphoid waist fracture with angulation of fracture fragments

        • Progresses to collapse and non-union

          • Get abnormal healing that looks like a humpback

            • Associated with DISI

  • Fractrue

Scaphoid Stabilizers

  • Scapho-lunate ligament

  • Scapho-traezial-trapezoid ligament

    • Very thin lines between these bones that is very hard to see

  • SLING ligament (image below)

    • Radio-scapho-capitate ligament

    • Arises from mid radius to attach to capitate with debated attachment or overlying of scaphoid

References:

Dorsal (striated band shaped)

Scapholunate Advanced Collapse (SLAC wrist)

  • Most common cause of degenerative changes of the wrist from injury or degeneration typically from CPPD to the scapho-lunate ligament

  • Note: At baseline the scaphoid always wants to rotate in flexion but is restrained by the SL ligament, if the ligament is injured it will be allow to rotate

  • Scapholunate ligament

    • Volar part

    • Interosseous membranous component

    • Dorsal part = strongest

    • SLD & LTV

      • Scapholunate - dorsal is strongest

      • Lunate-triquetral - volar is strongest

    • If suspected injury on radiograph —> clenched fist view radiograph —> should make it worse

  • High risk of developing DISSI - dorsal intercalated segmental instability

    • Causes

      • Scaphoid fracture = bony DISSI

      • Distal radius fracture = compensatory DISSI

      • Radius malunion = adaptive DISSI

      • Dissociation of scaphoid and lunate = ligamentous DISSI

        • Results in a lunate basically angulated volarly

        • Look at angle below with green curved line

          • Should be less than 60 deg, if >70 deg almost always DISSI

  • Findings

    • Hypertrophy of the radial styloid (scaphoid rubs against it) - stage 1

    • Arthritis (joint space narrowing, degen of scaphoid) at scaphoradial joint - stage 2

    • Narrowing, erosions of capito-lunate articulation - stage 3

    • Generalized degeneration of the intercarpal and carpal-radial articulations - stage 4

DISI

  • Radial side injury

  • Injury to scapho-lunate ligament (i think)

  • Lunate rolls dorsally

  • Angle > 60

General

  • Multiple synovial spaces in wrist

    • The pisiform and radiocarpal joint synovial spaces communicate normall

    • If you see a wrist effusion would expect to see increased fluid around pisiform too

    • Can also use the pisiform space for wrist arthrography

Carpal Dislocations

Peri-lunate dislocation

  • Lunate and radius stay together but the otehr carpal bones move

  • High association with scaphoid fractures

  • Most benign of the dislocations

Lipomatosis of Nerve

  • Basically fatty infiltration of the nerve

  • If occurs in median nerve will result in thenar atrophy similar to carpal tunnel syndrome

  • Has the coaxial cable appearance

  • If you see fat in the lesion it excludes a neurofibroma or schwannoma which are other items in the ddx

VISI

  • Ulnar side injury

  • Injury to luno-triquetral ligament

  • Lunate and scaphoid move volar

  • Scaphoid-lunate angle <30

  • Rare

Ulnar nerve hypertrophy

  • Seen in bicycle riders

  • Nerve should normally taper as it moves toward wrist

  • In this it will gradually get larger

Lunate dislocation

  • Lunate dislocated and other bones normal

  • Associated with dorsal radiolunate ligament injury

  • Most severe of the dislocations

Wartenberg Syndrome

  • Compression of superficial branch of radial nerve in distal forearm

  • Tight watches can cause

  • Pain at rest

  • Positive tinel test

Positive Ulnar Variance

  • Ulnar higher than radius at DRUJ

  • Can get lunate-ulnar impaction syndrome where the distal ulna abuts the lunate and you get degenerative shit/cyst formation, etc.

Mid-Carpal dislocation

  • Capitate and lunate lose alignment with radius

  • Associated with

    • Triquetral fractures

    • Triquetral0lunate interosseous ligament disruption

Wrist Extensor Compartments

  • 6 compartments each with their own sheath

De Quervian Tenosynovitis

  • Inflammation of the tendon sheath of the first extensor (dorsal) tendon compartment of the wrist usually at the radial styloid

  • Extensor retinaculum overlies these tendons

    • With repetitive irritation/trauma the retinaculum will thicken and limit the normal ability of the tendon and sheath to move

      • Results in inflammation, pain and this shit

  • Remember this compartment contains the ABductor pollicis longus and extensor pollicis brevis tendons

Intersection Syndrome

  • Similar to DQT

  • Tendon sheath inflammation involving the first and second wrist extensor compartments where they intersect in the forearm

  • Will occur more proximal in the forearm than DQT

  • The inflammation is typically of the secondary compartment tendon sheath