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

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

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

De Quervian Tenosynovitis

• Entrapment of the first extensor tendon compartment containing

  • First extensor tendon

  • Abductor pollicis longus tendon

  • Extensor pollicis brevis tendon

• Entrapment is typically at the radial styloid by extensor retinaculum

• Positive finklestein test

• F>M (pick up babies, typing etc.)

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

Ulnar nerve hypertrophy

• Seen in bicycle riders

• Nerve should normally taper as it moves toward wrist

• In this it will gradually get larger