• A condition of progressive instability causing advanced arthritis of radiocarpal and midcarpal joints
    • describes the specific pattern of degenerative arthritis seen in chronic dissociation between the scaphoid and lunate
  • Pathoanatomy
    • chronic SL ligament injury creates a DISI deformity
      • scaphoid is flexed and lunate is extended as scapholunate ligament no longer restrains this articulation
        • scapholunate angle > 70 degrees
        • lunate extended > 10 degrees past neutral
    • resultant scaphoid flexion and lunate extension creates
      • abnormal distribution of forces across midcarpal and radiocarpal joints
      • malalignment of concentric joint surfaces
    • initially affects the radioscaphoid joint and progresses to capitolunate joint
  • Watson classification 
    • describes predictable progression of degenerative changes from the radial styloid to the entire scaphoid facet and finally to the unstable capitolunate joint, as the capitate subluxates dorsally on the lunate
    • key finding is that the radiolunate joint is spared, unlike other forms of wrist arthritis, since there remains a concentric articulation between the lunate and the spheroid lunate fossa of the distal radius
Watson Stages
Stage I Arthritis between scaphoid and radial styloid 
Stage II Arthritis between scaphoid and entire scaphoid facet of the radius 
Stage III  Arthritis between capitate and lunate 
note: radiolunate joint spared 
  • While original Watson classification describes preservation of radiolunate joint in all stages of SLAC wrist, subsequent description by other surgeons of "stage IV" pancarpal arthritis observed in rare cases where radiolunate joint is affected
    • validity of "stage IV" changes in SLAC wrist remains controversial and presence pancarpal arthritis should alert the clinician of a different etiology of wrist arthritis


  • Symptoms
    • difficulty bearing weight across wrist
    • patients localize pain in region of scapholunate interval
    • progressive weakness of affected hand
    • wrist stiffness
  • Physical exam
    • tenderness directly over scapholunate ligament dorsally
    • decreased wrist ROM
    • weakness of grip strength
    • Watson scaphoid shift test post
      • patients may have positive Watson scaphoid shift test early in the process,
      • will not be positive in more advanced cases as arthritic changes stabilize the scaphoid
      • technique
        • with firm pressure over the palmar tuberosity of the scaphoid, wrist is moved from ulnar to radial deviation
        • positive test seen in patients with scapholunate ligament injury or patients with ligamentous laxity, where the scaphoid is no longer constrained proximally and subluxates out of the scaphoid fossa resulting in pain
        • when pressure removed from the scaphoid, the scaphoid relocates back into the scaphoid fossa, and typical snapping or clicking occurs
        • must compare to contralateral side
  • Radiographs
    • obtain standard PA and lateral radiographs
      • PA radiograph will reveal greater than 3mm diastasis between the scaphoid and lunate
        • Stage I SLAC wrist  
          • PA radiograph shows radial styloid beaking, sclerosis and joint space narrowing between scaphoid and radial styloid
        • Stage II SLAC wrist
          • PA radiograph shows sclerosis and joint space narrowing between scaphoid and the entire scaphoid fossa of distal radius
        • Stage III SLAC wrist
          • PA radiograph shows sclerosis and joint space narrowing between the lunate and capitate, and the capitate will eventually migrate proximally into the space created by the scapholunate dissociation
      • lateral radiograph
        •  will reveal DISI deformity and subluxation of capitate dorsally onto lunate
    • stress radiographs unnecessary
  • MRI
    • unnecessary for staging, but will show
      • thinning of articular surfaces of the proximal scaphoid
      • scaphoid facet of distal radius and capitatolunate joint with synovitis in radiocarpal and midcarpal joints
  • Nonoperative
    • NSAIDs, wrist splinting, and possible corticosteroid injections
      • indications
        • mild disease 
  • Operative
    • radial styloidectomy and scaphoid stabilization
      • indications
        • Stage I
      • technique
        • prevents impingement between proximal scaphoid and radial styloid
        • may be performed open or arthroscopically via 1,2 portal for instrumentation
    • PIN and AIN denervation
      • indications
        • Stage I
      • technique
        • since posterior and anterior interosseous nerve only provide proprioception and sensation to wrist capsule at their most distal branches, they can be safely dennervated to provide pain relief
        • can be used in combination with below procedures for Stage II or III
    • proximal row carpectomy
      • indications
        • Stage II
        • contraindicated if there is an incompetent radioscaphocapitate ligament
        • contraindicated with caputolunate arthritis (Stage III) because capitate articulates with lunate fossa of the distal radius
      • technique
        • excising entire proximal row of carpal bones (scaphoid, lunate and triquetrum) while preserving radioscaphocapitate ligament (to prevent ulnar subluxation after proximal row carpectomy)
      • outcomes
        • provides relative preservation of strength and motion
    • scaphoid excision and four corner fusion
      • indications
        • Stage II or III
      • technique
        • also provides relative preservation of strength and motion
        • wrist motion occurs through the preserved articulation between lunate and distal radius (lunate fossa)
      • outcomes
        • similar long term clinical results between
        • scaphoid excision/ four corner fusion and
        • proximal row carpectomy
    • wrist fusion
      • indications
        •  Stage III 
        • any form of pancarpal arthritis
      • outcomes
        • wrist fusion gives best pain relief and good grip strength at the cost of wrist motion

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Questions (2)

(OBQ12.163) A 65-year-old man fell and injured his right wrist. Radiographs taken in the emergency room are seen in Figure A. He was treated as a sprain and no further follow-up was planned. He sustained 2 minor falls over the next 6 years and his wrist pain recurred. Recent radiographs are seen in Figure B. Surgical treatment that will best address his symptoms and preserve wrist motion consists of Review Topic


Anterior and posterior interosseous neurectomy




Scaphotrapezialtrapezoidal (STT) fusion




Complete wrist arthrodesis




Proximal row carpectomy




Four-corner fusion with scaphoidectomy



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Four-corner fusion with scaphoidectomy is indicated for Stage III SLAC wrist.

Surgical treatment of SLAC wrist is stage dependent. Stage I disease (scaphoid-radial styloid arthritis) is treated with AIN/PIN neurectomy. This procedure can also be done in addition to other bony procedures for Stages II-III disease. Stage II (scaphoid-entire scaphoid facet) is treated with PRC or scaphoid excision with 4-corner fusion (4CF). Stage III (capitolunate arthritis with proximal migration of the capitate into the scapholunate interval) is treated with either scaphoidectomy with 4CF or total wrist fusion.

Some other conditions exist: If capitolunate arthritis exists, PRC is contraindicated and 4CF is performed. If radiolunate arthritis exists, both PRC and 4CF are contraindicated and total wrist fusion is performed. If both radiolunate and capitolunate surfaces are preserved, then either PRC or a 4CF may be performed.

Cohen et al. compare PRC with 4-corner fusion plus scaphoid excision. PRC is technically easier, but leads to shortening of the carpus with weakness and incongruity exists between the capitate and lunate fossa of the distal radius. Scaphoid excision and four-corner fusion maintains carpal height and preserves the radiolunate relationship, but is more technically demanding, there is risk of nonunion, and it requires longer postop immobilization. Pain relief is more reliable following 4-corner fusion.

Figure A shows scapholunate ligament disruption. Figure B shows late stage SLAC wrist. There is capitolunate arthritis but no radiolunate arthritis. Illustration A shows an example of PRC. Illustration B shows an example of 4CF and scaphoidectomy.

Incorrect Answers
Answer 1. Neurectomy of AIN and PIN is performed for Stage I disease and can also be done in addition to other bony procedures for Stages II-III.
Answer 2. STT fusion is indicated for chronic scapholunate instability, STT arthritis and Kienbock's disease. It is not appropriate for Stage III SLAC wrist as it does not address capitolunate arthritis.
Answer 3. Complete wrist arthrodesis is indicated for pancarpal arthritis in a young patient. It is less appropriate for this 71-year-old patient. It sacrifices wrist motion. Wrist arthrodesis would be performed if BOTH capitolunate and radiolunate arthritis were present
Answer 4. Proximal row carpectomy is indicated for Stage II disease. It is contraindicated where capitolunate arthritis is present (Stage III).


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(OBQ04.38) A 45-year-old male sustained a fall onto his right wrist 2 weeks ago. A radiograph is shown in figure A. What joint is first affected if left untreated with subsequent development of a SLAC (scapholunate advanced collapse) wrist? Review Topic


Capitolunate joint
















STT (scaphotrapezotrapezoidal)



Select Answer to see Preferred Response


The clinical presentation is consistent with a SLAC wrist. The radioscaphoid joint is the first to be affected in this process.

The radiographs of the right wrist demonstrate a scapholunate dissociation, as evidenced by an increased scapholunate joint space, referred to as scapholunate diastasis (abnormal when the gap is greater than 2 mm and increased from the opposite extremity and other intercarpal spaces).

If left untreated, the wrist may progress to a "SLAC" wrist, as originally described by Watson and Ballet in 1984, which is the most common form of wrist arthritis. The repetitive sequence of degenerative changes is based on and caused by articular alignment problems between the scaphoid, the lunate and the radius.

Kuo et al. review the stages of SLAC wrist. They report stage I SLAC wrist involves changes limited to an area of abnormal contact between the abnormally rotated scaphoid and the radial styloid. In stage II the remaining radioscaphoid joint is affected, as persistent abnormal load transfer and shear across the cartilaginous surfaces leads to degeneration of the proximal scaphoid facet. In stage III, the dorsally translated capitate migrates proximally into the widened scapholunate interval, and degenerative changes occur at the capitolunate joint. The relative congruency of the radiolunate joint in all positions of lunate rotation due to the spherical shape of the lunate facet preserves this articulation, and at all stages of SLAC wrist the radiolunate joint is not involved. The lunate is congruently loaded in every position and, thus, highly resistant to degenerative changes.

Illustration A below shows the stages of involvement in the SLAC wrist.


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