Updated: 5/20/2021

Scaphoid Nonunion Advanced Collapse (SNAC)

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  • Summary
    • Scaphoid Nonunion Advanced Collapse (SNAC) describes the specific pattern of progressive arthritis of the wrist that results from a chronic scaphoid nonunion.
    • Diagnosis is made clinically with progressive wrist pain and wrist instability with radiographs showing scaphoid fracture nonunion with advanced arthritis of the radioscaphoid joint.
    • Treatment involves observation in early stages of disease. A variety of operative procedures may be indicated depending on severity of disease and patient's symptoms.
  • Etiology
    • Pathophysiology
      • pathoanatomy
        • natural history of degenerative changes first occurs at the radioscaphoid area followed by pancarpal / midcarpal arthritis
  • Anatomy
    • Scaphoid anatomy
      • blood supply
        • major blood supply is dorsal carpal branch (branch of the radial artery)
          • enters scaphoid in a nonarticular ridge on the dorsal surface and supplies proximal 80% of scaphoid via retrograde blood flow
        • minor blood supply from superficial palmar arch (branch of volar radial artery)
          • enters distal tubercle and supplies distal 20% of scaphoid
      • motion
        • both intrinsic and extrinsic ligaments attach and surround the scaphoid
        • the scaphoid flexes with wrist flexion and radial deviation and it extends during wrist extension and ulnar deviation (same as proximal row)
      • also see Wrist Ligaments and Biomechanics for more detail
  • Classification
    • Radiographic Classification
      Stage I
      Arthrosis localized to the radial side of the scaphoid and radial styloid
      Stage II
      Scaphocapitate arthrosis in addition to Stage 1
      Stage III
      Periscaphoid arthrosis (proximal lunate and capitate may be maintained)
  • Presentation
    • Symptoms
      • weakness
        • reduced grip and pinch strength
      • stiffness
        • stiffness with extension and radial deviation
    • Physical exam
      • palpation
        • localized tenderness of the radioscaphoid articulation
      • motion
        • decreased wrist motion on extension and radial deviation
  • Imaging
    • Radiographs
      • recommended view
        • ap and lateral of wrist
      • findings
        • see radiographic classification above
  • Differential
    • SLAC wrist 
    • Scaphoid fracture nonunion 
  • Treatment
    • Nonoperative
      • observation alone
        • indications
          • medically frail and low functioning patients only
    • Operative
      • radial styloidectomy plus scapholunate reduction and stabilization
        • indications
          • stage I
      • proximal row carpectomy
        • indications
          • stage II and III
        • outcomes
          • disadvantages
            • reduction of wrist motion and grip strength
            • procedure should be avoided if there are capitate head degenerative changes
      • four-corner fusion
        • indications
          • stage II and III
        • outcomes
          • retains 60% of wrist motion and 80% of grip strength
      • wrist arthrodesis
        • indications
          • stage II and III
  • Prognosis
    • Patients with scaphoid nonunions of > 5 years duration or proximal pole necrosis have less favorable outcomes
    • Punctate bleeding of bone during surgery is a good prognostic indicator of union
      • 92% union with obvious bleeding, 71% with questionable bleeding, 0% with no bleeding
      • results show decreased rate of arthritis (down to 40-50%)
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(SBQ17SE.11) A 67-year-old woman presents with chronic insidiously progressive right wrist pain. Her history is only significant for a remote fall onto her wrist 25 years prior. A radiograph of her affected wrist is shown in Figure A. After extensive discussion, she elects to undergo a salvage motion-sparing procedure that relies on the intact cartilage of the capitate head. During the dissection, the most volar-radial ligament is excised. What is her anticipated outcome?

QID: 211226
FIGURES:
1

Improved pain and increased range of motion by 3 months

15%

(241/1597)

2

Ulnar translocation of the carpus

70%

(1114/1597)

3

Capitate avascular necrosis

3%

(42/1597)

4

Distal radio-ulnar joint instability

4%

(66/1597)

5

Progression of radio-styloid arthritis

8%

(124/1597)

L 3 A

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(OBQ07.78) A 30-year-old female reports 5 months of wrist pain after a fall onto her wrist. A radiograph is shown in Figure A. If untreated, which of the following is least likely to occur during the natural progression of the disease process?

QID: 739
FIGURES:
1

Radial styloid osteophyte

6%

(262/4193)

2

Radioscaphoid arthritis

10%

(436/4193)

3

Midcarpal arthritis

11%

(471/4193)

4

Scaphocapitate arthritis

14%

(592/4193)

5

Radiolunate arthritis

57%

(2402/4193)

L 3 D

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