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 Although
the anatomy is similar, there are many
unique aspects to second toe transplantation that distinguish it from
reconstruction with the great toe. The second toe is used more commonly for
digital reconstruction of the index, long, ring or small finger, and at least in
North America, it is used rarely for thumb reconstruction. The second toe
appearance is more like that of a finger and less like a thumb: there is a small
nail, narrow phalanges and presence of two interphalangeal joints. In Asia, the
common use of ‘Zori’ type slippers makes second toe transplantation for thumb
reconstruction the preferable procedure in spite of the aesthetic outcome
result. Like great toe transplantation, the second toe flap harvest is
technically challenging, and requires meticulous dissection technique. It is not
a flap for the novice microsurgeon.
Preoperative Assessment
Any traumatic injury or congenital absence requires
a thorough preoperative evaluation by the microsurgeon. The hand is examined to
determine the anatomy of the loss, suppleness of joints and soft tissues and the
potential requirements for reconstruction. Vascular inflow, innervation, bony
structure and the presence of adequate controlling tendons are assessed. The
need for any further soft tissue reconstruction is identified, such as a second
skin or fasciocutaneous transplant or even a local flap . If a second toe
transplant is felt to be the recontsruction 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. This
often leads to results that are of no value, i.e. poor visualization of the
small vessels in the foot and to the toes. In healthy individuals with no clear
indication for angioraphy, the study does not help the surgeon either plan or
perform the surgical procedure.
Anatomy
The second toe is narrow, with a squarish nail, and
small distal phalanx. Toe extension is provided by the extensor digitorum
longus and brevis tendons. Flexion is provided by the flexor digitorum
longus and brevis tendons, with the longus used for digital reconstruction when
attached to the flexor tendons in the hand. The plantar digital nerves provide
sensation, and travel volar to the deep transverse metatarsal ligaments (not
shown below). The digital nerves are short and often require intraneural
dissection from the common digital to gain extra length if required for the
transplant. The flap is typically disarticulated at the metatarsophalangeal
joint, but it can also be taken distal pr proximal to this level. The second
metatarsal can provide support for reconstruction of a defect where metacarpal
is missing.
Venous Anatomy
The large plexus of vein on the dorsum of the foot
can be marked preoperatively with a venous tourniquet about the ankle. The
dorsal venous arch has multiple interconnections and drainage via the greater
and lesser saphenous systems. This system allows a long pedicle for the
venous system that can be easily dissected free.
Vascular Anatomy
Arterial infow to the second toe is supplied by the both the first dorsal
metatarsal artery and the first plantar metatarsal artery, one of which is
usually dominant. In our experience, approximately 60% of patients have a
plantar dominant system. Occasionally, both dorsal and plantar systems are
of similar caliber. A strong Doppler signal extending from the dorsalis
pedis to the first web space ordinarily means a good dorsal inflow will be
present. Both systems communicate via branches that dive between the
metatarsals and send arterial inflow into the toe.
In the figure below, the second metatarsal and second toe are revealed from a
medial perspective, after the great toe and first metatarsal (above in gray)
have been peeled away. Communicating branches between the dorsal and
plantar systems are visible, as are the braches to the second toe, and the
transected branches to the great toe. This anatomy can be quite variable
often with the first dorsal system diving through or deep to the first dorsal
interosseous muscle. The muscle may need to be divided or an intramuscular
dissection may need to be performed to expose the dominant inflow system.
If plantar dominance requires dissection of the vessel proximally on the plantar
aspect, the vessel may be traced to the dorsal pedis if the first dorsal interosseous muscle is divided. Some
authors recommend vein grafting to the distal plantar dominant system and
avoiding the tedious plantar dissection. The disadvantage of vein grafting
include a potential increase in the rate of thrombosis and a smaller caliber
artery that is present distally.
Operative Procedure
A well padded tourniquet is placed on the
ipsilateral thigh and the patient is prepped and draped in the prone position
with the entire foot and lower leg below the knee in the operative field.
The major draining veins of the second toe are usually drawn on the dorsum of the
foot with a marking pen and the incision is outlined as shown below. It extends
from the first web space proximally to a level 2 to 3 centimeters proximal to
the metatarsophalangeal joint and then distally into the third web space, forming
a triangular skin flap proximal to the toe. An incision is usually made
proximal to the apex of this triangle to obtain proximal exposure. A
similar incision is made on the plantar aspect of the foot.
Attention is turned first to the first web space.
The dissection is begun here to identify the arterial branches to the second and
great toes, and then the dominant arterial supply.
If the system is dorsal, the
rest of the dissection proceeds with relative ease dorsally, isolating the first
dorsal metatarsal artery and the second toe extensor and a major draining vein.
If the arterial inflow is plantar dominant, the dorsal dissection can be
continued to isolate the extensor tendon and a dorsal vein. The extensor
tendon is divided with enough length to coapt it to the extensor in the hand.
The plantar
dissection requires isolating the flexor tendon and nerves,
and possibly the artery, depending on the dominance of the inflow. In the plantar fat this can be
tedious, and particularly tedious if the vessel wraps medially around the
plantar sesamoid bone of the great toe. The flexor tendon is divided with
enough length to perform a flexor repair in the hand. The
metatarsophalangeal joint is disarticulated and the toe is isolated on a the
arterial pedicle and a draining vein. The tourniquet is deflated and the
circulation is allowed to return to the toe for the appropriate length of time
with regards to total tourniquet time. When the recipient team is ready,
the artery and vein are ligated and the toe is taken to the field in the hand.
The donor site is closed by transecting the fourth metatarsal at its base and
approximating the transverse metatarsal ligaments of the great and third toes.
A Penrose or suction drain is sometimes used. An ankle splint is
optional.
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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