Acute Scaphoid Fractures
JBJS AAOS Instructional Lecture 2008, AAOS 2000 (Jupiter), JBJS Br 2011 (Dias)
Anatomy
- Mostly covered in articular cartilage
- Spans both carpal rows
- Has a tubercle distally
- Blood supply (radial artery) enters from:
- Distal tubercle
- Dorsal ridge (non-articular) – main blood supply
- Enters just distal to the waist
- Blood supply is therefore retrograde
- Scapholunate interosseous ligament attaches to the proximal pole
- Fracture of waist may result in extension of the proximal pole:
- Due to lunate extension
- Relative flexion of the distal pole (humpback)
- Fracture of waist may result in extension of the proximal pole:
Epidemiology
- Young men, participating in sports
Mechanism
- Sudden dorsiflexion or fall onto hand
Classification
Fracture Pattern - Russe
- Horizontal oblique
- Transverse
- Vertical oblique (most unstable due to shear)
Stability – Herbert
- Stable:
- Incomplete fractures
- Tuberosity fractures
- <1mm displacement/gap in any plane
- Unstable:
- All complete fractures
- more than 1mm displacement/gap
- more than degrees SL angle
- more than degrees radiolunate angulation
- more than degrees CL angle
- Angular deformity of scaphoid – difficult to assess on XR
- Comminution
- Delayed Union
- Non-Union
Location
- Tubercle
- Distal pole
- Waist
- Proximal pole
Diagnosis
Examination
- Snuff box pain; pain on volar aspect (better); pain on axial compression
Imaging
- XR and delayed XR (30% non-diagnostic):
- PA, Lateral, Oblique & scaphoid view
- Scaphoid view:
- 30-degree tube angulation with wrist in 20-degree ulnar deviation
- Effectively elongates and extends the scaphoid into view
- CT Scan – fine cut (1mm slices) in the long axis of the scaphoid:
- Useful to diagnose fracture; assess union and quantify deformity
- Highly sensitive but specificity 75%
- MRI – useful for undisplaced fractures:
- MRI is the gold standard investigation for diagnosis
- High signal representing bone edema on T2
- Highly sensitive & specific
Management
Why Operate?
- Correct deformity (severe deformity is uncommon)
- Deformity leads to carpal instability patterns (DISI usually)
- Prevent non-union & malunion
- Prevent SNAC development
- Expedite return to function (soft indication)
Non-union Risk Factors
- Smoking
- Delayed presentation and treatment >4 weeks after injury (45%)
- more than 1mm displacement at waist
- Angular deformity
- Proximal pole (AVN) (up to 80% non-union rate)
- Vertical oblique fractures:
- Almost all distal pole and tubercle fractures heal without deformity
- No indication for surgery
Waist Fractures
- more than 90% union rate if undisplaced
- Rarely indicated to treat surgically
- 10% non-union rate
In an Undisplaced Waist Fracture:
- Surgery (JBJS AM 2010 meta-analysis – Dutch study including David Ring):
- Reduced time to union
- Quicker return to sports and work
- Higher early satisfaction
- Better early functional scores
- Better early grip strength
- Higher complication rate
- BUT, No difference in:
- Union rate
- Malunion rate
- Cost
- Pain
- Long-term functional scores or grip strength
Complications
- Non-union
- Malunion
- Scaphotrapezial OA
- Infection
- Impingement of screw
Therefore, reasonable to offer percutaneous surgery but at risk of complications
In Displaced Waist Fractures (Dias JBJS BR Review 2011)
- Higher chance of non-union, but only 14%
- Main issue is malunion:
- Carpal instability
- Premature arthritis
- Reduced wrist extension
- More complex surgery to revise
Proximal Pole
- Higher risk of AVN
- Non-union (up to 80%)
- SNAC
- These risks have not actually been well quantified
- Generally accepted that we should fix all proximal pole fractures
Treatment Options for All Fractures
Cast Immobilization
- Above elbow not shown to be better than below
- No difference with thumb spica or not
- Neutral position
- Maintain plaster for a minimum of 8/52
- Can take up to 12/52 for proximal pole to heal
- Therefore, back into plaster if pain at 8 weeks
- Remove plaster regardless at 12 weeks
Surgery
Percutaneous
- II guidance
- Extend over rolled crepe and ulnar-deviate wrist to reduce fracture
- Only proceed if fracture can be reduced
- Can use wide-bore cannula to move trapezium
- Aim down center of scaphoid on AP & Lateral
- On lateral, should be aiming for the center of the lunate
- Take XR dynamic screening & obliques to ensure central placement
- Measure then pass wire distal to prevent backout
- Take 4mm off measurement for screw length
Volar Approach
- Workhorse approach for waist fractures
- Preserves dorsal blood supply; allows correction of deformity and grafting
- Technique:
- Landmarks are tubercle and FCR
- Hand is extended over a crepe roll
- Longitudinal incision just radial to FCR
- FCR retracted ulnarward
- Curve incision radially in distal part over tubercle
- Longitudinal incision made in the volar wrist capsule
- Care taken to preserve radioscaphocapitate ligament
- The non-articular portion of the proximal part of the trapezium may need to be resected
- Capsule may be incised horizontally to gain access to the scaphotrapezial joint
- The fracture is reduced with use of a dental pick or Kirschner wire (“joysticks”)
- Anatomic reduction should be achieved prior to fixation
- Screw should be as long and central as possible
- Subtract 2-4mm to allow for compression
Dorsal Approach
- Better for proximal pole fractures
- Technique:
- Flex wrist over crepe roll to deliver proximal pole
- Longitudinal incision centered over Lister’s tubercle
- The extensor retinaculum is longitudinally incised
- Retract the tendons of the second & third dorsal compartments
- May be between 3rd & 4th compartments
- XR to confirm position
- The wrist capsule is incised transversely over proximal pole
- Without injuring the deeper scapholunate ligament
- Care must be taken not to disturb the dorsal ridge:
- Main blood supply to the scaphoid is found
- Excellent visualization of the proximal portion of the scaphoid, especially with the wrist in maximum flexion
- Entry point of guide wire is just radial to the scapholunate ligament origin