Scaphoid Fracture - Hand

Summary
- Scaphoid Fractures are the most common carpal bone fracture, often occurring after a fall onto an outstretched hand.
- Diagnosis can generally be made by dedicated radiographs but CT or MRI may be needed for confirmation.
- Treatment may require a prolonged period of cast immobilization, percutaneous surgical fixation, or open reduction and internal fixation.

Epidemiology
- Incidence
  - 15% of acute wrist injuries
  - 60% of all carpal fracture
  - 8 per 100,000 females, 38 per 100,000 males
- Demographics
  - 2 :1 male : female
  - most common in third decade of life
- Anatomic location
  - percentage of fractures by scaphoid anatomic location
    
    waist -65%
    
    proximal third - 25%
    
    distal third - 10%
    
    Historically the distal pole is most common location in pediatrics due to ossification sequence, however more recently waist fractures have become most common

Etiology
- Pathophysiology
  - pathoanatomy
    
    most common mechanism of injury is axial load across a hyper-dorsiflexed, pronated and ulnarly-deviated wrist
    
    common in contact sports
    
    transverse fracture patterns are considered more stable than vertically or obliquely oriented fractures
- Associated conditions
  - SNAC (Scaphoid Nonunion Advanced Collapse)

Anatomy
- Osteology
  - complex 3-dimensional structure described as resembling a boat, skiff, and twisted peanut
  - oriented obliquely from extremity's long-axis (implications for advanced imaging techniques)
  - largest bone in proximal carpal row
  - > 75% of scaphoid bone is covered by articular cartilage
  - articulates with radius, lunate, trapezium, trapezoid, and capitate
- 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
  - creates vascular watershed and poor fracture healing environment
- Biomechanics
  - link between proximal and distal carpal row
  - both intrinsic and extrinsic ligaments attach and surround the scaphoid
  - the scaphoid flexes with wrist flexion and radial deviation and extends during wrist extension and ulnar deviation (same as proximal row)
- See Wrist Ligaments and Biomechanics for more detail

                        Classification
                    
                                            Herbert and Fisher Classification (based on fracture stability)
                                        
                                            Type A
                                        
                                            Stable, acute fractures
                                        
                                            Type B
                                        
                                            Unstable, acute fractures (distal oblique, complete waist, proximal pole, trans-scaphoid and perilunate associated fractures)
                                        
                                            Type C
                                        
                                            Delayed union characterized by cyst formation and fracture widening
                                        
                                            Type D
                                        
                                            Nonunion
                                        
                                            Mayo classification (based on location of fracture line)
                                        
                                            Type I
                                        
                                            Distal tubercle fracture
                                        
                                            Type II
                                        
                                            Distal articular surface fracture
                                        
                                            Type III
                                        
                                            Distal third fracture
                                        
                                            Type IV
                                        
                                            Middle third fracture
                                        
                                            Type V
                                        
                                            Proximal third fracture
                                        
                                            Russe Classification (based on fracture pattern)
                                        
                                            Type I 
                                        
                                            Horizontal oblique fracture line
                                        
                                            Type II 
                                        
                                            Transverse fracture line
                                        
                                            Type III
                                        
                                            Vertical oblique fracture line

Presentation
- History
  - high or low energy fall onto outstretched hand
- Symptoms
  - variable level of pain over wrist
- Physical exam
  - inspection
    
    wrist swelling
    
    rarely any ecchymosis, hematoma, or gross deformity
  - motion
    
    worsened wrist pain with circumduction
  - pain with resisted pronation
  - provocative tests
    
    anatomic snuffbox tenderness dorsally
    
    scaphoid tubercle tenderness volarly
    
    scaphoid compression test
    
    positive test when pain reproduced with axial load applied through thumb metacarpal
    
    87-100% sensitivity and 74% specificity when all three tests positive within 24 hours of injury

Imaging
- Radiographs
  - recommended views
    
    neutral rotation PA
    
    lateral
    
    semi-pronated (45°) oblique
    
    scaphoid
    
    30 degree wrist extension, 20 degree ulnar deviation
    
    waist fractures seen best
  - findings
    
    if radiographs are negative (27%) and there is a high clinical suspicion
    
    repeat radiographs in 14-21 days
- Bone scan
  - indications
    
    occult fractures in acute setting
  - sensitivity and specificity
    
    specificity of 98%, and sensitivity of 100%, PPV 85% to 93% when done at 72 hours
- MRI
  - indications
    
    most sensitive for diagnosis occult fractures < 24 hours
    
    immediate identification of fractures / ligamentous injuries
    
    assessment of vascular status of bone (vascularity of proximal pole)
    
    proximal pole AVN best determined on T1 sequences
  - sensitivity and specificity
    
    approach 100% for occult fractures
- CT scan with 1mm cuts along scaphoid axis
  - indications
    
    best modality to evaluate fracture location, angulation, displacement, fragment size, extent of collapse, and progression of nonunion or union after surgery
  - sensitivity and specificity
    
    62% sensitivity and 87% specific for determining stability and fracture
    
    less effective than bone scan and MRI to diagnose occult fracture

Treatment
- Nonoperative
  - cast immobilization
    
    indications
    
    stable nondisplaced fracture (majority of fractures)
    
    if patient has normal radiographs but there is a high level of suspicion can immobilize in thumb spica and reevaluate in 12 to 21 days
    
    outcomes
    
    scaphoid fractures with <1mm displacement have union rate of 90%
- Operative
  - percutaneous screw fixation
    
    indications
    
    unstable fractures as shown by
    
    proximal pole fractures
    
    displacement > 1 mm without significant angulation or deformity
    
    non-displaced waist fractures
    
    to allow decreased time to union, faster return to work/sport, similar total costs compared to casting
    
    outcomes
    
    union rates of 90-95% with operative treatment of scaphoid fractures
    
    CT scan is helpful for evaluation of union
  - open reduction internal fixation
    
    indications
    
    significantly displaced fracture patterns
    
    15° scaphoid humpback deformity
    
    radiolunate angle > 15° (DISI)
    
    intrascaphoid angle of > 35°
    
    scaphoid fractures associated with perilunate dislocation
    
    comminuted fractures
    
    unstable vertical or oblique fractures
    
    outcomes
    
    accuracy of reduction correlated with rate of union

Technique
- Cast immobilization
  - technique
    
    start immobilization early
    
    nonunion rates increase with delayed immobilization of > 4 weeks after injury
    
    long arm spica vs short arm casting is controversial
    
    no consensus
    
    duration of casting depends on location of fracture and risk of nonunion
    
    immobilization maintained until radiographic fracture healing demonstrated, usually no sooner than 8 weeks
    
    may be required for up to 12-14 weeks for high-risk fracture patterns/patients
    
    athletes should not return to play until imaging shows a healed fracture
    
    may opt to augment with pulsed electromagnetic field (studies show beneficial in delayed union)
    
    formal therapy following immobilization to regain range of motion
- Percutaneous screw fixation
  - approach
    
    dorsal approach
    
    best for proximal pole fractures
    
    care must be taken to avoid EPL tendon and to preserve the blood supply when entering the dorsal ridge
    
    limit exposure to the proximal half of the scaphoid
    
    percutaneous has higher risk of unrecognized screw penetration of subchondral bone
    
    volar approach
    
    indicated in waist and distal pole fractures
    
    fractures with humpback flexion deformities
    
    allows exposure of the entire scaphoid
    
    avoids jeopardizing scaphoid blood supply
    
    uses the interval between the FCR and the radial artery
    
    careful capsule management to allow closure and restoration of RSC ligament
    
    arthroscopic assisted approach
    
    has also been described to aid in anatomic reduction
  - technique
    
    precise wire placement in central axis to guide cannulated screw
    
    do not violate scaphotrapeziotrapezoidal joint cartilage
    
    rigidity is optimized by long screw placed down the central axis of the scaphoid
    
    oblique fluoroscopic images to confirm placement and appropriate screw length
- Open reduction internal fixation
  - approach
    
    dorsal and volar approaches as above
  - technique
    
    allows direct visualization and reduction at fracture site
    
    screw placement as above

Complications
- Scaphoid Nonunion
  - incidence
    
    5-10% following immobilization, higher rates for proximal pole fractures
  - risk factors
    
    vertical oblique fracture pattern, displacement >1mm, advancing age, nicotine use
  - treatment
    
    vascularized or nonvascularid bone grafting procedures
- Osteonecrosis
  - incidence
    
    13-50% of all scaphoid fractures
    
    many studies showing 100% in proximal fifth fractures with immobilization
- Malunion
  - flexion of distal fragment and extension of proximal fragment due to pull of scapholunate interosseous ligament creating shortened bone with humpback deformity
  - treatment
    
    no clear indications supporting operative versus non-operative treatment
- Subchondral bone penetration with arthrosis due to prominent hardware
  - incidence
    
    seen following mini-open fixation techniques
    
    incidence has decreased with use of fluoroscopy
  - treatment
    
    revision surgical fixation versus implant removal following union
- SNAC wrist (scaphoid nonunion advanced collapse)

Prognosis
- Incidence of AVN (without treatment) is directly correlated with proximity of fracture to proximal pole
  - proximal 5th AVN rate of 100%
  - proximal 3rd AVN rate of 33%

Herbert and Fisher Classification (based on fracture stability)
Type A	Stable, acute fractures
Type B	Unstable, acute fractures (distal oblique, complete waist, proximal pole, trans-scaphoid and perilunate associated fractures)
Type C	Delayed union characterized by cyst formation and fracture widening
Type D	Nonunion

Mayo classification (based on location of fracture line)
Type I	Distal tubercle fracture
Type II	Distal articular surface fracture
Type III	Distal third fracture
Type IV	Middle third fracture
Type V	Proximal third fracture

Russe Classification (based on fracture pattern)
Type I	Horizontal oblique fracture line
Type II	Transverse fracture line
Type III	Vertical oblique fracture line