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HAND AND MICROSURGERY > SCAPHOID FRACTURES AND NONUNIONS > Flashcards

SCAPHOID FRACTURES AND NONUNIONS Flashcards

1
Q

Blood supply to scaphoid

A

Major supply = dorsal carpal branch (branch of radial artery)
- enters dorsal surface via non-articular ridge
- supplies proximal 80% of scaphoid via retrograde flow
Minor supply = superficial palmar branch of radial artery
- enters scaphoid tubercle
- supplies distal 20% of scaphoid

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2
Q

Pathoanatomy of humpback deformity with scaphoid fractures

A

Humpback deformity = apex dorsal deformity
Proximal fragment extends with lunate via SL ligament
Distal fragment flexes with trapezium and trapezoid

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3
Q

Classification of scaphoid fractures

A

Based on anatomic location
Waist (middle 1/3) = most common (70%)
Distal pole (distal 1/3) = 10-20%
Proximal pole (proximal 1/3) = 10-20%

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4
Q

Differentials for radial-sided wrist pain

A 
Bony vs. soft-tissue
Bony causes
1. Distal radius fracture
2. Scaphoid fracture
3. Perilunate/ lunate dislocation
4. Base of thumb fracture
5. Radiocarpal arthritis
6. SLAC/ SNAC wrist
7. Base of thumb arthritis
8. STT arthritis
Soft-tissue causes
1. SL ligament injury
2. FCR tendonitis
3. DeQuervain's tenosynovitis
4. Intersection syndrome
5. SRN neuroma
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5
Q

4 views in a scaphoid series

A
  1. PA
  2. PA with ulnar deviation
  3. Lateral
  4. Semi-pronated oblique view
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6
Q

7 radiographic signs of scaphoid fracture instability

A
  1. Displacement > 1mm
  2. Comminution
  3. Vertical or oblique vs. transverse fracture pattern
  4. Humpback deformity = intrascaphoid angle > 35deg (normal = 25deg)
  5. Scaphoid collapse = scaphoid height:length ratio > 0.65 (normal < 0.65)
  6. SL angle > 70deg (normal = 30-60deg)
  7. RL angle > 15deg dorsal (normal 0 +/- 10deg)
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7
Q

Indications for bone scan with suspected scaphoid fractures

A

Bone scans have 100% sensitivity and specificity for occult scaphoid fractures AFTER 72HRS

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8
Q

Indications for CT scan with scaphoid fractures

A

Best imaging modality for
1. Assessment of deformity = sagittal CT best for measurement of intrascaphoid angle
2. Assessment of nonunions
CT with 1mm slices along axis of scaphoid best

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9
Q

Indications for MRI with scaphoid fractures

A

Best imaging modality for

  1. Occult fractures = 100% sensitivity and specificity within 24hrs
  2. Associated ligamentous injury
  3. Vascularity of proximal fragment
    - contrast enhanced MRI or non-enhanced T1 weighted images (low signal = avascular) are best
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10
Q

Management options for patients with normal xrays but high clinical suspicion for scaphoid fracture

A
  1. MRI if < 72hrs
  2. Bone scan if > 72hrs
  3. Immobilise in thumb spica cast, reassess clinically and radiologically in 14-21 days
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11
Q

Percutaneous fixation (compared to casting) of undisplaced scaphoid waist fractures

A
  1. Faster time to union

2. Faster return to work

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12
Q

Factor affecting time to union and union rate of scaphoid fractures

A

Depends on location

  1. Distal pole and scaphoid tubercle fractures
    - average time to union 6wks
    - union rate almost 100%
  2. Undisplaced waist fractures
    - average time to union 8wks
    - union rate almost 90-95%
  3. Undisplaced proximal pole fractures
    - average time to union 12wks
    - union rate < 50%
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13
Q

Assessment of scaphoid union

A

Clinical and radiological

  1. Clinical = based on snuffbox tenderness
  2. Radiological = based on trabeculations across fracture site
    - CT is best to assess union
    - no callus with scaphoid fracture healing = most of scaphoid is covered by cartilage
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14
Q

10 surgical indications for scaphoid fractures

A
  1. Displacement > 1mm
  2. Comminution
  3. Vertical or oblique vs. transverse fracture pattern
  4. Proximal pole fractures
  5. Humpback deformity = intrascaphoid angle > 35deg (normal = 25deg)
  6. Scaphoid collapse = scaphoid height:length ratio > 0.65 (normal < 0.65)
  7. SL angle > 70deg (normal = 30-60deg)
  8. RL angle > 15deg dorsal (normal 0 +/- 10deg)
  9. Scaphoid nonunions with or without AVN
  10. Scaphoid fractures associated with perilunate injuries
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15
Q 
Volar approach to scaphoid:
Advantages
Disadvantages
Indications
Contraindications
Technique
A
  1. Advantages
    - lower risk of injury to blood supply of scaphoid
    - allows exposure of entire scaphoid
    - allows correction of humpback deformity
  2. Disadvantages
  3. Indications
    - waist and distal pole fractures
  4. Contraindications
    - proximal pole fractures
  5. Technique
    - interval is between FCR and radial artery
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16
Q 
Dorsal approach to scaphoid:
Advantages
Disadvantages
Indications
Contraindications
Technique
A
  1. Advantages
    - better screw placement and more threads across fracture site with proximal pole fractures
  2. Disadvantages
    - higher risk of injury to blood supply of scaphoid
    - poor visualisation of waist and distal pole
    - difficult to correct humpback deformity
  3. Indications
    - proximal pole fractures
  4. Contraindications
    - waist and distal pole fractures
  5. Technique
    - preserve blood supply by limiting exposure to proximal 1/2 of scaphoid
17
Q

Scaphoid nonunion definition

A

Failure to unite at 6mo

FDA and AO definition of nonunion = failure to unite at 9mo with no progression of healing over 3mo

18
Q

Natural history of scaphoid nonunions

A

Progressive collapse, carpal instability and arthritis

19
Q

Radiographic signs of scaphoid nonunion

A
  1. Resorption and widening of fracture gap
  2. Sclerosis
  3. Cysts
  4. Progressive collapse = scaphoid height:length ratio > 0.65 (normal < 0.65)
  5. Humpback deformity = intrascaphoid angle > 35deg (normal = 25deg)
  6. DISI deformity
    - SL angle > 70deg (normal = 30-60deg)
    - RL angle > 15deg dorsal (normal 0 +/- 10deg)
  7. SNAC wrist
20
Q

Assessment of vascular status of proximal fragment with scaphoid fractures

A

Preoperative vs. intraoperative

  1. Preoperative = contrast-enhanced MRI or non-enhanced T1 weighted images (low signal = avascular)
  2. Intraoperative = punctate bleeding (more important)
21
Q

3 factors to consider with surgical management of scaphoid nonunions

A
  1. Deformity
  2. Vascularity
  3. Arthritis
22
Q

3 principles of surgical management of scaphoid nonunions

A
  1. Debridement of necrotic bone
  2. Correction of deformity = volar opening wedge
  3. Rigid internal fixation = headless compression screw along central 1/3 of axis of scaphoid
23
Q

2 indications of vascularised bone graft

A
  1. Failure of previous grafting

2. AVN of proximal fragment = higher union rate with VBG compared to NVBG (80 vs. 40%)

24
Q

2 main vascularised local bone graft options

A
  1. Volar approach = PG pedicle

2. Dorsal approach = 1,2 intercompartmental supraretinacular pedicle

HAND AND MICROSURGERY (63 decks)

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