FRACTURE OF
SCAPHOID
The
scaphoid acts as a link between the proximal and distal rows of the carpus and
thus is quite susceptible to injury. Most fractures of the scaphoid waist
result from an extension force applied to the distal pole, with the proximal
pole stabilized by the strong radiocapitate and radioscaphoid ligaments. This
mechanism of injury, for example, a fall on the outstretched hand, produces the
most common fracture pattern a break through the waist of the scaphoid.
Other patterns include fractures of the distal tuberosity and proximal pole and
vertical shear fractures of the scaphoid body.
The blood supply to the bone plays
an important role in the healing process, and sometimes osteonecrosis is a
complication of scaphoid fractures. The major blood supply enters the junction
of the waist and distal pole on the dorsal aspect, leaving the proximal pole
with a relatively poor vascular supply. Fractures through the waist of the
scaphoid disrupt most of the blood supply to the proximal pole, often leading
to osteonecrosis.
Fractures of the scaphoid are the
most commonly missed fractures of the upper limb; yet, early diagnosis is
essential for successful treatment. The initial signs are tenderness and pain
over the anatomic snuffbox, with some swelling and loss of the normal concavity
of the dorsoradial region of the wrist. Also present is significant discomfort
when the thumb is moved or the metacarpal of the thumb is compressed against
the proximal carpal row.
Initial radiographs may not
accurately demonstrate a fracture of the scaphoid waist. Special views are
needed of the hand forming a fist and of the fist in ulnar deviation, positions
that bring the scaphoid into extension. An occult fracture of the scaphoid can
often be visualized by aiming the x-ray beam parallel to the suspected fracture
line rather than at an acute angle to it. However, even with these special
views of the wrist, some acute scaphoid fractures are not clearly seen.
If symptoms are present, even if
radiographs are normal, the wrist should be immobilized in a thumb spica
cast for 2 to 3 weeks. Follow-up radiographs after the plaster cast is removed
often reveal a previously occult fracture. If pain persists, the cast is
reapplied. Magnetic resonance imaging is another useful tool in evaluating the
wrist with a suspected occult scaphoid fracture. Immediate magnetic resonance
imaging has been shown to have high sensitivity and specificity for diagnosis
of occult scaphoid fractures, as well as a favorable cost-benefit
analysis compared with immobilization and repeat plain radiographs.
Most nondisplaced fractures of the
scaphoid can be successfully treated by placing the limb in a thumb spica cast
with the hand and wrist rigidly immobilized and the thumb in abduction. Some
physicians recommend the use of an above-elbow cast, at least for the first 6
weeks of treatment, on the premise that above-elbow casting
of scaphoid fractures may enhance union. Prompt recognition, secure
immobilization, and careful follow-up remain the essentials of closed
treatment. The rate of union in fractures that are immobilized initially is
close to 95%. In fractures that are not immobilized initially, the nonunion
rate is significantly higher. There is growing support for immediate percutaneous
screw fixation of nondisplaced scaphoid fractures. Percutaneous techniques
utilizing either volar or dorsal approaches have been shown to diminish the
time required for immobilization with a faster return to work and sports.
However, the overall union rates between cast immobilization and surgical screw
fixation are equivalent. Contemporary management of nondisplaced scaphoid
fractures takes into account the location of the fracture (proximal, waist,
distal) and individualizes treatment based on the patient’s athletic,
recreational, and vocational demands.
Any degree of displacement of a
scaphoid fracture may be an indication of wrist instability. Displaced scaphoid
fractures are often associated with ligament injuries that ultimately result in
persistent wrist instability after the fracture heals. Displaced fractures
should be treated with ORIF. Nonunion is much more common after displaced
fractures. Therefore, a scaphoid fracture with a displacement greater than 1 mm
requires ORIF to ensure union and wrist function.
OPERATIVE TREATMENT
Indications for immediate operative
fixation of scaphoid fractures include displaced fractures, fractures
associated with carpal instability, and nonunions. Relative indications for
operative fixations include delay in diagnosis (greater than 4 weeks from
injury), proximal pole fractures, and malunions.
The cannulated, headless screw,
with threads of different pitches at either end, is a very effective device for
stabilizing and compressing a scaphoid fracture. There are numerous implants on
the market, all with the same goal of compression across the fracture.
Acute Nondisplaced Fractures
Operative fixation of acute,
nondisplaced scaphoid fractures is increasing in popularity with the
introduction of less invasive surgical techniques and
advances in intraoperative imaging and instrumentation. Currently, acute
scaphoid fractures can be repaired by means of open volar or dorsal approaches,
percutaneous techniques, or arthroscopically assisted procedures. Common to all
techniques is the use of biplanar imaging to confirm fracture reduction and
central guide wire placement as well as the use of specially designed headless
compression screws. Compromising accurate reduction
and central screw placement, for the sake of a percutaneous approach, must be
avoided. Immediate operative fixation of acute, nondisplaced scaphoid waist
fractures has entered clinical practice and is quickly becoming the standard of
care. Compared with prolonged cast immobilization, the number of healed
fractures is equivalent, but times to fracture healing are significantly
reduced. Taras and colleagues reported return to participation in sports
averaged 5.4 weeks, with successful fracture union achieved in all patients
undergoing percutaneous scaphoid fixation. We counsel our athletes about the
risks and benefits of all treatment regimens and advocate percutaneous fixation
for all athletes requesting a rapid return to competition. Although both volar
and dorsal approaches have been described, we typically employ a dorsal
approach to percutaneous internal fixation.
Acute Displaced Fractures
In acute, displaced scaphoid waist
fractures, a volar approach to the scaphoid is used to preserve the dorsal
blood supply. The fracture is reduced, with careful restoration of length and
correction of the “humpback” deformity, and the cannulated, headless
compression screw is applied volarly from distal to proximal. The critical step
is to ensure appropriate screw position (centered throughout the bone on
multiple oblique views).
Acute proximal pole scaphoid
fractures should be approached through a dorsal approach. Reduction is
confirmed, and a cannulated, headless compression screw is placed with accurate
screw placement evaluated and confirmed on multiple radiographic/fluoroscopic
images.
Scaphoid Nonunion
The management of the united
scaphoid fracture is challenging. Initial diagnosis must be followed by a thorough
history regarding the timing of injury and further studies to (1) evaluate for
carpal collapse and arthritic destruction, (2) determine the vascularity of the
proximal pole of the scaphoid, and (3) define the geometry of the fracture
nonunion. All scaphoid non-unions require debridement of the nonunion site and
bone grafting. Scaphoid waist nonunions with a viable proximal pole can be
managed with a volar approach to the scaphoid, debridement of the nonunion,
reduction, and use of autograft bone. Proximal pole
nonunions or waist nonunions with avascular change to the proximal fragment
require debridement and vascularized bone grafting either from the distal
radius, thumb, or a distant site (e.g., medial femoral condyle). Any scaphoid
nonunion with advanced degenerative changes is best managed with some type of
salvage procedure (proximal row carpectomy, limited arthrodesis, or total wrist arthrodesis).
