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 Small joint arthroplasty of the metatarsophalangeal
and proximal interphalangeal joints can be challenging and is often limited to
the low demand patient population. The vascularized joint can in selected
cases of trauma or congenital absence offer joint replacement that is permanent
and functional. Additionally, because an open epiphysis continues to
develop after transplantation, reconstruction in children has the potential for
growth. Stiffness can be problematic, but less so in the younger patient
population. Both the pip joint of the second toe and the mp joint of the
second toe have been used for small joint reconstruction.
Preoperative Assessment
Any traumatic injury or congenital absence requires
a thorough preoperative evaluation by the microsurgeon. The hand is thoroughly
assessed to determine the anatomy of the loss and the potential requirements for
reconstruction. If a vascularized joint transplant is felt to be the
reconstruction of choice, the surgeon must evaluate the lower extremity
completely. This includes a history of previous injury or surgery, and a
complete skeletal, vascular and sensorimotor examination. Particular attention
should be paid to the pedal pulses. If arterial inflow is thought to be
questionable whether by history or physical examination, then an angiographic
study of the lower extremity is performed. We however do not routinely perform
angiography of the lower extremity because we have found the vessel spasm of the
foot to be particularly problematic in angiography, and this often leads to
results that are of no value in determining toe vascular anatomy. In healthy
individuals with no clear indication for angioraphy, the study does not help the
surgeon either plan or execute the surgical procedure.
Anatomy
The joints of the second toe are used. Either
the metatarsophalangeal joint or the proximal interphalangleal joint. The
mp joints of the foot are primarily extension joints with significantly more
range of motion in extension. The opposite is true for the pip joint.
When the mp joint is used for reconstruction therefore, it is typically placed
with its extensor surface volarly and the flexor surface dorsally, thus
maximizing finger flexion at the joint.
The vascular supply to the second toe is via the
first dorsal metatarsal artery, a continuation of the dorsalis pedis artery. The
first dorsal metatarsal can remain entirely dorsal, or in greater than 50% of
cases, dives deep between the first and second metatarsal, to provide a plantar
dominant inflow to the second toe. In the first web space, the termination of
the plantar or dorsal dominant system can always be found sending branches to
the second toe and great toe.
Plantar to these branches are the digital
nerves to the great and second toe and the transverse metatarsal ligament. The
second toe has both long and short extensors, with the long tendon used to power
the toe in the hand. The flap is typically disarticulated at the metatarsophalangeal joint, but it can also be taken distal to this level. More
distally, great caution must be taken not to injure the small digital vessel
supplying arterial inflow.
Operative Procedure
The second toe is dissected in the manner describe
in the second toe transplantation
section.
When the second toe is isolated, before or after the arterial inflow and
draining vein are divided, the toe is trimmed of tissue that is not required.
If the pip joint is being used, as in the figure below, osteotomies are made on
the middle and proximal phalanx, leaving behind the vascular supply and
drainage, as well as any tendons that will be used. A small cuff of soft
tissue is left subcutaneously while a skin paddle remains for monitoring.
If the mp joint is to be used, the distal metatarsal is harvested with the toe.
The distal osteotomy is performed on the proximal phalanx after distal soft
tissue is removed.
Left behind are a skin paddly and inflow and outflow vessels. Nerve supply
and tendon supply is optional depending on the reconstruction.
Post-Operative Care
The foot is kept elevated for the first week and
then introduced to a progressive dangling regimen. An ace wrap can provide
gentle compression during dangling. Weight bearing is not begun until the
donor site is well healed, often not until four to six weeks. During this
time crutch use can be difficult because use of the reconstructed hand is
limited. In bilateral toe transplants crutches are not used. In
these cases special shoes that keep the feet in exaggerated dorsiflexion can be
used to limit plantar weight and transfer weight to the heels.
Significant wound complications are rare in the
healthy patient. If a vascular complication in the transplanted toe
requires systemic patient heparinization, then hemorrhage into the second
metatarsal space can cause ecchymosis, flap necrosis and delayed healing.
This is treated according to the severity of any wound development.
Rehabilitation with dangling and subsequent ambulation are delayed.
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