Updated: 10/4/2016

SNAC (Scaphoid Nonunion Advanced Collapse)

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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 corpectomy
      • 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 (2)

(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? Review Topic

QID: 739
FIGURES:
1

Radial styloid osteophyte

6%

(187/2952)

2

Radioscaphoid arthritis

9%

(266/2952)

3

Midcarpal arthritis

10%

(294/2952)

4

Scaphocapitate arthritis

17%

(506/2952)

5

Radiolunate arthritis

57%

(1683/2952)

ML 3

Select Answer to see Preferred Response

PREFERRED RESPONSE 5
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