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Scaphoid Non-union
The scaphoid bone is one of the eight small bones that comprise the wrist
joint. The two rows of small wrist bones act together to allow the
wide variety of wrist positions and motions that we take for granted.
The scaphoid bone spans or links these two rows together and, therefore
has a special role in wrist stability and coordinating wrist motion
(see Figure 1).
The scaphoid bone is vulnerable to fracture because of
its position within the wrist and its role in wrist function. When the
scaphoid bone is broken, it may not heal properly because it has a very
fragile blood supply. Scaphoid fractures that do not heal are referred
to as a scaphoid non-union. Ultimately, scaphoid non-unions can lead
to loss of wrist motion and eventual wrist arthritis.
Patients with a scaphoid non-union usually present with a history of
previous wrist injury, especially a fall onto an outstretched wrist.
They will typically have pain along the thumb side of the wrist and
may also have diminished wrist mobility, particularly wrist extension.
Scaphoid fractures and non-unions are usually confirmed by x-rays of
the wrist (see Figure 2A and 2B). In many cases, special x-ray tests
are also used to decide the best treatment approach. A CT scan is helpful
to check for collapse of the scaphoid on itself, resulting in a bend
in the bone, which is called a “humpback” deformity (see
Figure 3).
Scaphoid non-unions may also develop a problem called avascular
necrosis. Avascular necrosis occurs when part of the scaphoid bone dies
because of the loss of blood flow. This can eventually result in fragmentation
and the collapse of the bone. Its presence also makes repair of the scaphoid
much more difficult. An MRI scan can be helpful to check for avascular
necrosis (see Figure 4).
Treatment of a scaphoid non-union is dependent upon a variety of factors.
Once a scaphoid fracture has failed to heal, a relatively predictable
pattern of degeneration within the wrist generally occurs, although
the time frame is variable. In most cases, the scaphoid eventually
collapses, which results in a change in wrist mechanics that leads
to motion loss and arthritis. Depending upon the stage of this process
at which the non-union is recognized, various treatment alternatives
exist. In cases without significant arthritis, surgery to restore scaphoid
alignment and heal the bone is preferred. This usually requires placement
of a bone graft and some type of internal bone fixation, such as pins
or a screw (see Figure 5).
Scaphoid non-unions with avascular necrosis present special challenges
to healing since part of the bone is dead. Recent techniques using bone
grafts with an attached vessel to maintain blood supply (vascularized
bone grafts) have improved our ability to heal these difficult conditions
(see Figure 6).
Finally, in cases with established arthritis or failed reconstructive
efforts, surgery to heal the scaphoid is often no longer an option. In
these cases, surgery is tailored towards pain improvement along with
maintaining a functional wrist. Depending on the degree of arthritis,
surgery may include techniques that spare motion, such as radial styloidectomy
(removal of a local piece of arthritic bone), partial fusion of the wrist
bones, or proximal row carpectomy (removal of the proximal row of wrist
bones). If the arthritis is more widespread in the wrist, complete wrist
fusion may be needed.
Wrist bone anatomy
X-ray of scaphoid fracture
non-union
X-ray of normal scaphoid
Diagram of normal and
collapsed scaphoid
MRI of scaphoid fracture
non-union with avascular proximal fragment
Scaphoid repaired with
a screw
Vascularized bone graft
for scaphoid
© 2007 American Society for Surgery of the Hand
Developed by the ASSH Public Education Committee
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