Principles of Toe Transplantation

Preoperative Evaluation

Like any medical condition a thorough history and physical examination is obligatory before developing the most appropriate treatment regimen.  The following are critical elements:

• Evaluation of hand function, sensation and surrounding tissue - lack of flexor tendons, adjacent nerve or a bone platform may require additional planning or staged reconstruction, and in some cases may preclude toe transplantation.  Any requirement for bone in addition to the distal and proximal phalanx may affect the choice of the donor site and concurrent flap reconstruction or bone grafting.

• Skeletal examination - x-ray evaluation will help define the bone platform and define reasonable expectations of function. 

• Vascular assessment - the presence of injury to the vascular inflow of the hand may require the use of vein grafts or additional toe pedicle length.  Preoperative aniography is often necessary for surgical planning.

• Donor foot assessment - a history of injury, surgery or peripheral vascular disease may alter the ability to use a toe for reconstruction.  Preoperative aniography may be necessary.

• Clay models - impressions of the great and second toe can be made with clay models and placed on the hand to simulate the possible appearance of the transplant and to plan positioning of the toes.  The modes can give an indication of potential surgical outcome.

The surgical technique is outlined in the great toe transplantation link.

Post-operative Monitoring

Monitoring is done clinically and with a continuous venous Doppler and fluorescein angiography.  Occasionally, flow in a toe transplant can be both low in quantity and velocity, precluding accurate monitoring with an implantable Doppler probe.  Fluorimetry has proven valuable and accurate in assessing post-operative circulatory disturbances. 

If circulatory embarrassment is detected, arterial or venous anastomotic compromise is possible.  Other factors, such as a constrictive dressing, poor limb positioning, or hematoma are ruled out.  On occasion, simple repositioning of  an elbow or arm can restore circulation to the affected digit.  If extrinsic causes are ruled out, treatment with pharmacologic or operative intervention may be required. 

• Venous compromise may necessitate surgical exploration and anastomotic revision or vein grafting.  Medicinal leeches can be used to decompress venous hypertension and sluggish flow.

• Arterial anastomotic clots might require operative revision or vein grafting.  Thrombolytics can be used to aid distal perfusion and blood flow.

• Systemic anticoagulation is often indicated if clotting has compromised blood flow to a transplanted digit.  Patients with vascular complications in the transplanted toe requiring heparin tend to have more difficulty with delayed healing in the foot. Hemorrhage into the donor wound with resultant edema and ecchymosis is generally greater, requiring longer term foot elevation and delayed rehabilitation.

Physical Therapy and Splinting

Even a perfectly executed toe transplant without post-operative complication can still end with poor function and disappointing results if physical therapy and splinting are not addressed.  Therapy is essential to avoiding joint contracture and maximizing tendon glide and hand function.  Patients that maximize their effort in post-operative rehabilitation are much more likely to have a rewarding outcome.

Complications

• Flap Loss - the failure rate for great and second toe transplants is less than 5%. 
  Poor anatomic position - positioning of the second toe transplant when reconstructing the index through small fingers is less complex than thumb reconstruction. One need only consider flexion and extension of the metacarophalangeal and interphalangeal joints, rather than the variable positioning of the thumb saddle joint and need for opposition. Nevertheless, poor anatomic position is easy to achieve and requires great care to avoid. Similar to hand fractures, angulation or rotation of the bone can be magnified markedly when flexion is achieved. The transplanted toe is checked in flexion and extension to ensure normal anatomic position, and only after adequate fixation is achieved, are tendons repaired, followed finally by microsurgical repair.  A small amount of angulation is frequent however.

• Non-union - although non-union is frequent in replantation it is rare in toe transplants.  Bone fixation can be achieved with k-wires, screws or plates. Four-cortical screw fixation is more difficult to achieve in a second toe transplant and we favor k-wires and plating. The IP joints are often pinned in extension to minimize tension on the tendon repairs and to prevent flexion contracture. If the extensor tendons are not balanced appropriately an extensor lag of the IP joints can result. After checking the position in flexion and extension and using fluorscopy to ensure adequate bone alignment and hardware placement, tendon and vessel repair can proceed with all the considerations noted for great toe transplants.

• Tendon rupture, poor joint motion and poor sensory recovery - tend to occur in the minority of patient and are treated if encountered.

• Donor site complications  - the most common difficulty is delay in healing over the first metatarsal head. This is usually caused by taking too much skin with the toe transplant, or trying to preserve the entire first metatarsal head (figure 5). Since most of the weight is transferred to the lateral four metatarsal heads after removal of the large toe, the first metatarsal head can be shaved down considerably in its dorsal and tibial sides to reduce bulk and permit closure without tension.  Wound complications from the second toe harvest site are fewer in number since skin flaps created in the donor dissection are smaller. Adequate proximal resection of the 2nd metatarsal must be performed to minimize wound tension at closure. Much of the remaining tension can be removed by approximating the deep transverse metatarsal ligament with the heads of the 1st and 3rd metatarsals. When there is little tension, complications are minimized in the routine post-operative patient.

• Neuromas - pain on the plantar surface of the donor area can also occur. This usually results when the plantar nerves are not transected far enough back from the metatarsal heads and the neuroma of healing becomes trapped in the weight bearing area. Treatment consists of secondary mobilization and proximal transposition of the excised neuroma stump. Painful neuromas of the terminal branches of the superficial peroneal nerve can also be a problem, and are treated in a similar fashion.

• Hypertrophic and unstable scars can also develop, particularly after prolonged secondary healing. These are usually revised with scar excision and skin grafts and, in rare instances, with a second microvascular skin flap or muscle flap.

• Failure to use the transplant - one of the rarest unfavorable results occurs when a patient fails to use the transplant, in spite of a good anatomic position and acceptable function of the tendons, joints and nerves. This may occur because of poor patient compliance, lack of patient understanding of the overall goals of the operation, or other personal gain factors that the patient is not consciously aware of or perhaps does not reveal. Self-mutilation and Munchausen's disease are the ultimate unfavorable results after toe transplantation procedures.