Updated: 2/12/2021

Scaphoid Nonunion Advanced Collapse (SNAC)

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Introduction
  • A condition characterized by advanced collapse and progressive arthritis of the wrist that results from a chronic scaphoid nonunion
    • see scaphoid fracture 
  • Pathophysiology
    • pathoanatomy 
      • natural history of degenerative changes first occurs at the radioscaphoid area followed by pancarpal / midcarpal arthritis 
  • 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%)
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
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

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Questions (3)

(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%

(228/1471)

2

Ulnar translocation of the carpus

69%

(1022/1471)

3

Capitate avascular necrosis

2%

(36/1471)

4

Distal radio-ulnar joint instability

4%

(60/1471)

5

Progression of radio-styloid arthritis

8%

(115/1471)

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%

(260/4138)

2

Radioscaphoid arthritis

10%

(434/4138)

3

Midcarpal arthritis

11%

(463/4138)

4

Scaphocapitate arthritis

14%

(590/4138)

5

Radiolunate arthritis

57%

(2361/4138)

L 3 D

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