Scaphoid Fractures

Scaphoid Fractures The scaphoid is the most frequently fractured carpal bone, accounting for 71% of all carpal bone fractures. Scaphoid fractures often occur in young and middle-aged adults, typically those aged 15-60 years. About 5-12% of scaphoid fractures are associated with other fractures 70-80% occur at the waist or mid-portion 10-20% proximal pole

Anatomy The scaphoid lies at the radial border of the proximal carpal row, but its elongated shape and position allow bridging between the 2 carpal rows because it acts as a stabilizing rod. The scaphoid has 5 articulating surfaces: with the radius, lunate, capitate, trapezoid, and trapezium. As a result, nearly the entire surface is covered by hyaline cartilage.

Blood Supply Vessels may enter only at the sites of ligamentous attachment: the flexor retinaculum at the tubercle, the volar ligaments along the palmar surface, and the dorsal radiocarpal and radial collateral ligaments along the dorsal ridge.

Blood Supply Classically described as 3 principal arterial groups, but in more recent investigations by Gelberman and Menon described 2: Entering dorsally Volar side limited to tubercle

Blood Supply The primary blood supply comes from the dorsal branch of the radial artery, which divides into 2-4 branches before entering the waist of the scaphoid along the dorsal ridge. The branches course volar and proximal within the bone, supplying 70-85% of the scaphoid. The volar scaphoid branch also enters the bone as several perforators in the region of the tubercle; these supply the distal 20%-30% of the bone

Blood Supply All studies consistently demonstrated poor supply to the proximal pole The proximal pole is an intra-articular structure completely covered by hyaline cartilage with a single ligamentous attachment Deep radioscapholunate ligament Is dependent on intraosseous blood supply                                                        

Blood Supply Obletz and Halbstein in their study of vascular foramina in dried scaphoids found 13% without vascular perforations and 20% with only a single small foramen proximal to the waist Therefore postulated that atleast 30% of mid-third fracture would expect AVN of proximal pole…greater likelihood the more proximal the fracture

Pathophysiology The primary mechanism of injury to the scaphoid bone is a fall on an outstretched hand. A scaphoid fracture is part of a spectrum of injuries based on 4 factors: (1) the direction of 3-dimensional loading, (2) the magnitude and duration of the force, (3) the position of the hand and wrist at the time of injury, and (4) the biomechanical properties of ligaments and bones. These factors affect the end result of the fall: distal radius fracture, ligamentous injury, scaphoid fracture, or a combination of these.

Pathophysiology Essentially fractures of scaphoid have been explained as a failure of bone cause by compressive or tension load Compression, as explained by Cobey and White, against concave surface by head of capitate Position of radial and ulnar deviation thought to determine where it breaks Fryman subjected cadaver wrists to loading and observed that: extension of 35 degrees of less resulted in distal forearm fractures >90degrees resulted in carpal fractures Combination of radial deviation and wrist extension locks scaphoid within the scaphoid fossa

Diagnosis Suggested by: Imaging patient’s age, mechanism of injury and signs and symptoms Imaging Xray CT Scan MRI Bone Scan

Radiography The 4 essential views (ie, PA, lateral, supinated and pronated obliques) identify majority of fractures. The scaphoid view is a PA radiograph with the wrist extended 30° and deviated ulnarly 20°. This view helps to stretch out the scaphoid and is also used for assessing the degree of scaphoid fracture angulation. A clenched-fist radiograph has also been useful for visualization of the scaphoid waist.

CT Scans CT permits accurate anatomic assessment of the fracture. Bone contusions are not evaluated with CT, but true fractures can be excluded

MRI T1-weighted images obtained in a single plane (coronal) are typically sufficient to determine the presence of a scaphoid fracture. Gaebler prospectively performed MRI on 32 patients, at average of 2.8 days post injury 100% sensitivity and specificity In recent study Dorsay has shown that immediate MRI provides cost benefit when compared to splintage and repeat xray False positives due MRI’s sensitivity to marrow oedema

Nuclear Imaging Radionuclide bone scanning typically is performed 3-7 days after the initial injury if the radiographic findings are normal. Best at 48hours, premature imaging may be obscured by traumatic synovitis Bone scan findings are considered positive for a fracture when intense, focal tracer accumulation is identified. Negative bone scan results virtually exclude scaphoid fracture Teil-van studied cost effectiveness and concluded that initial xray followed by bone scan at 2 weeks if patient is still symptomatic is most effective management option Teil-van also suggested that more sensitive and less expensive than MRI

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Classification Determining optimal treatment depends on accurate diagnosis and fracture classification Herbert devised an alpha-numeric system that combined fracture anatomy, stability and chronicity of injury.

Herbert’s Classification Type A (stable acute fractures) A1: fracture of tubercle A2: incomplete fracture Type B (unstable acute fractures) B1: distal oblique B2: complete fracture through waist B3: proximal pole fracture B4: trans-scaphoid perilunate fracture dislocation of carpus

Herbert’s Classification Type C (delayed union) Type D (established non-union) D1: fibrous union D2: pseudarthrosis

Russe Classification Russe classified scaphoid fractures into 3 type according to the relationship of the fracture line to the long axis of the scaphoid Horizontal Oblique Vertical (unstable)

Classification according to location A: tubercle B: distal pole C: waist D:proximal pole

Management Proximal pole Depends on size and vascularity of fracture Growing sentiment that most should be treated operatively because of high propensity for non-union and increased duration of immobilisation required for non-operative management If large enough to accommodate a screw than every attempt should be made

Management DeMaagd and Engber showed 11 of 12 patients with proximal pole fractures healed with Herbert screw Retting and Raskin had 100% union in 17 cases with Herbert screw If fragment too small then K-wires can be used

                                                                                                      

Management Distal Pole Are infrequent Usually extra-articular with good blood supply Best treated with short arm thumb spica for 3-6 weeks

Management of waist fractures Most common type of fracture High rate of delayed and non-union With delays in treatment adversely affect results Operative vs non-operative Controversial

Management of waist fractures Most stable fractures can be treated with below elbow thumb spica Unstable fractures best treated with compression screw fixation >1mm displacement Fragment angulation Abnormal carpal alignment With advent of percutaneous techniques of cannulated screws under flouroscopic control trend towards operative management

What about the undisplaced waist fractures??? Netherlands study: Average time away from work 4.5 months Saeden in prospective randomised study with 12 year follow-up compared early operative vs cast immobilisation Return to work quicker in operative No significant long term difference in functional outcome between 2 groups Bond has shown return to work 7 weeks earlier and time of union 5 weeks quicker Other papers disagree Some surgeons published union rates of 100% with surgery(Green’s volume 1 page 721)

Complication$$ Malunion Malunion may lead to limited motion about the wrist, decreased grip strength, and pain. The most frequent pattern of malunion is persistent angular deformity, or the humpback deformity. Malunion usually can be treated with osteotomy and bone grafting to correct angular deformity and length. Literature confusing with no comparative studies to document improvement in hand function

Complication$$ Delayed union and non-union Delayed union is incomplete union after 4 months of cast immobilization. Non-union is an unhealed fracture with smooth fibrocartilage covering the fracture site. About 10-15% of all scaphoid fractures do not unite. Some degree of delayed union or non-union occurs in nearly all proximal pole fractures and in 30% of scaphoid waist fractures

Complication$$ Delayed union is anticipated if fracture treatment is delayed for several weeks. The risk of non-union increases after a delay of 4 weeks. These delays may be related to the patient's failure to seek treatment for a presumed sprain, but they more frequently are related to improper or incomplete immobilization or a failure to diagnose and treat the acute fracture

Delayed union treatment If the delayed union is stable and less than 6 months old relative to the time of injury, prolonged cast immobilization with or without electrical stimulation may be used. Treatment of choice for a symptomatic non-union is placement of a bone graft and fixation. Russe corticocancellous iliac graft Fisk-Fernandez volar wedge graft Pronator pedicle graft Braun ‘83 reported 100% union in 8 pts Kawai, Kuhlmann, Papp reported 100% 37 pts Pechlaner reporrted 25 free vascularised iliac grafts with 100% Success rates for the treatment of non-union are as high as 82%.

AVN Osteonecrosis occurs in 15-30% of all scaphoid fractures, and most of these involve the proximal pole. Its incidence increases as the fracture line becomes more proximal; this decreases the probability that the blood supply to the proximal pole is preserved

Salvage procedures Radial styloidectomy Distal scaphoid resection Proximal row carpectomy Partial arthrodesis