Great Toe Transplantation

Abstract

Despite being relatively uncommon in the general population, thumb amputations cause severe disability. More than 3,300 thumb amputations occurred in the United States. The thumb makes up around 40% of the function of the hand. Therefore, losing it would result in significant medical, hospital, and societal costs. Thumb reconstruction surgery's primary goal is to restore grip strength, including the range of motion, fine and tripod pinch, power grasp, strength, and sensibility, while secondary goals include restoring hand aesthetics. In cases of thumb replantation, like-for-like replacement is possible; however, when thumb replantation is not possible, great toe-to-hand transplantation is the best available reconstruction. When compared with other reconstructive options such as osteoplastic thumb reconstruction, pollicization, second toe transplantation, and the use of a thumb prosthesis, great toe transplantation provides superior function and aesthetics. For restoring pinch, sensitivity, strength, and aesthetics of the hand with well-tolerated donor site morbidity, toe to thumb transplantation is regarded as the gold standard.

Thumb amputations, while relatively rare in the general population, are the source of significant disability, particularly in those who use their hands extensively for vocation and avocation. The Global Burden of Disease study published in 2017 reported 2 million thumb amputations worldwide with an incidence of 4.1 individuals per 100,000. ¹ Thumb amputation carries the most significant disability weight, 10.5 (5.0–19.7) compared with nonthumb digit amputations at 9.4 (3.5–19.9) years lived with disability per 100,000. ¹

In the United States, over 3,300 thumb amputations were registered in the National Trauma Database. ² Since approximately 40% of hand function depends on the thumb, its amputation is associated with substantial patient, hospital, and social costs. ³ Therefore, the substantial decrease in quality of life and productivity, surgical treatment for thumb loss should be considered a priority. ^{4 5}

The primary goal of thumb reconstruction surgery is the restoration of hand function, including the range of motion, fine and tripod pinch, power grasp, strength, and sensibility, while secondarily restoring the aesthetics of the hand. ⁶ Like-for-like replacement can be accomplished in cases of thumb replantation; however, when thumb replantation is not feasible, great toe-to-hand transplantation represents the best available reconstruction. Great toe transplantation offers superior function and aesthetics compared with other reconstructive options including: osteoplastic thumb reconstruction, pollicization, second toe transplantation, and the use of a thumb prosthesis. ^{7 8}

Successful and reliable thumb reconstruction using a composite tissue transplant from the toe to the hand has been described since the 1970s, ^{9 10} and since then, it has become a well-established procedure for reconstructing a single or multiple digits of the hand. ^{11 12 13 14 15} Innovations in surgical microsurgical instrumentation and technological advances in the microsurgical field have contributed to the consistent improvement in the reliability of toe transplantation. ¹⁶ This article aims to describe the key aspects of the great toe-to-thumb transplantation technique in an effort to foster reproducibility, consistency, and efficiency.

History

Great toe transplantation is based on the concept described by Nicoladoni in 1897, who performed two-stage toe-to-hand transplantation. Harry Buncke published success results in one-stage hallux-to-hand transplantation, or a “single stage Nicoladoni procedure,” in Rhesus monkeys in 1966. ¹⁷ The first great toe to the thumb transplantation in a human was accomplished by Cobbett in 1969. ⁹ Cobbett had spent the preceding months in Harry Buncke's microsurgical laboratory working on the procedure. The first great toe-to-thumb transplantation in the United States was performed by Buncke et al ¹⁰ in 1973, leading to a new era in microsurgical reconstruction of the hand. Since then, advances in all levels of microsurgery have allowed surgeons to overcome the issues reported by Dr. Buncke's team, making it possible to refine and improve upon the reliability of the technique. Currently, great toe-to-thumb transplantation is the gold standard for thumb reconstruction in well-defined cases with, more than 96% rate of success. ^{18 19}

Indications

The primary indication for surgery is absence of the thumb with resultant critical loss in hand function and the level of amputation will inherently dictate the transplant to be performed. Amputation at or proximal to the metacarpophalangeal joint (MCPJ) of the thumb will require provision for additional soft tissue prior to toe transplantation. Additional soft tissue provision may be accomplished prior to or simultaneous with toe transplantation. Ideally, a third of the proximal interphalangeal bone must be present to guarantee an appropriate thumb length. Thus, the carpometacarpal joint (CMCJ) and the MCPJ maintain their functionality, while the distal portion of the new thumb is restored using the distal interphalangeal joint (IPJ) of the toe. ¹⁹ When the amputation is located more proximal, the switching-two-toe transfer technique, a modification of the original method that combines the bony component of the second toe, described by Piñal, ^{20 21} is a viable option. This technique is selected to avoid harvesting the first metatarsal along with the great toe, which theoretically increases the donor site morbidity. Rather than complicating the operations, we generally prefer to fuse the MCPJ, placing to toe in a functional and stable position in cases where the native MCPJ is not preserved. When the length of the proximal phalanx of the toe is desired to be increased, osteogenic distraction or web space deepening are excellent options. However, the selection of the surgical treatment will ultimately be case-dependent ( Fig. 1 ). ^{18 22 23}

Fig. 1.

Great toe transplant, artist rendering.

Patient education and consent is necessary prior to thumb reconstruction. Patients should understand the fundamentals of the chosen technique and be willing to transfer the deformity of the hand to the foot, where it will be less obvious and better tolerated. In some circumstances, the patient is unwilling to accept the resulting foot deformity and the surgeon must be accepting of this decision. In these circumstances, other types of reconstruction may be considered. Psychiatric consultation may also be of value in allowing the patient to understand their injury, its impact on their lives, and to better accept reconstructive options.

Toe transplantation can be performed either in a delayed or an acute setting. Buncke et al ¹⁹ suggest an acute reconstruction within 2 weeks after the injury in patients with significant soft tissue loss and bone exposure. Additionally, Lam and Wei ⁷ reported an increase in one-stage total reconstruction in 2011, possibly associated with improvement in the microsurgical technique and experience in free tissue transfer. A reduction in the number of operations, a shortened rehabilitation period, and earlier return of function are noted benefits of acute reconstruction. Conversely, in the presence of avulsion or wound contamination, the best option is delayed reconstruction. Therefore, waiting 6 to 8 weeks after injury allows the tissue to heal and the patient to psychologically prepare for the surgery. ¹⁹

While we occasionally perform acute toe transplantations, we generally favor a delayed reconstructive sequence. We have found this more pragmatic approach to be the most reliable and predictable route to functional and aesthetic reconstruction. If additional soft tissue is necessary, provision for coverage is performed in the acute period and the toe transplant is undertaken 3 to 4 months later once the soft tissue envelope at the amputation site is amenable ( Fig. 2 ).

Fig. 2.

( A ) Complex thumb amputation. ( B ) Thumb amputation status post-stabilization. ( C ) Lateral arm flap design, in situ. ( D ) Lateral arm flap. ( E ) Lateral arm flap inset for soft tissue reconstruction.

Preoperative Considerations

Primary preoperative considerations focus on the overall health of the patient, the anatomy of the amputation site, and the vascular beds of the donor and recipient sites.

Patients undergoing toe to thumb transplantation should generally be in good health, qualifying as an American Society of Anesthesiologists (ASA) I or II based on the ASA physical status classification. Recipient site considerations revolve around the available soft tissue envelope, the level of amputation, musculotendinous units to power the transplant, as well as the recipient vasculature for arterial inflow and venous outflow. The level of amputation correlates directly with the soft tissue needs of the hand as well as the skeletal structure available for osteosynthesis. A viable thumb CMCJ is generally considered a necessity for toe transplantation; however, even this circumstance can be addressed. Metacarpal reconstruction may be necessary and can be accomplished using the great toe metatarsal, a metacarpal transfer within the hand, or a free fibula bone flap. The MCPJ, while advantageous, is not necessary for attaining good thumb function and MCP arthrodesis is well tolerated and frequently employed.

The vascular status of the donor and recipient sites is assessed preoperatively with Doppler ultrasound and arteriogram. These tests complement one another providing anatomical information about vessels' location, quality, and caliber. However, considering that the vascularity is more predictable at the donor site, Doppler ultrasound is usually the first study performed. Of note, the arteriogram is a suitable option in case of inconclusive Doppler ultrasound results due to its high correlation with both the Doppler ultrasound and intraoperative anatomical findings. ²⁴

Preoperative assessment of the donor site vascular pattern is useful in facilitating the operative dissection and can aid in planning the recipient vessel choice. Identification of the dominant vascular system can be done by placing the Doppler probe at the first metatarsal space and moving it down to the first web space. An intense signal throughout this area suggests that the first dorsal metatarsal artery (FDMA) is superficially located, which defines a dominant dorsal system. On the other hand, a loss of Doppler signal at the proximal portion of the first web space implies that the prevailing system comes from the plantar system. Doppler findings may be relied upon by the experienced surgeon in lieu of an arteriogram. An arteriogram can further define the vascular pattern within the foot. The transverse metatarsal ligament is a helpful anatomic landmark that facilitates the identification of the dominant system through the arteriogram. The orientation of the vessel with respect to this ligament defines the dominant vascular system as plantar or dorsal.

At the recipient level, both methods are highly recommended. The goal is to locate the inflow and outflow vessels for the toe to be transplanted. The dorsal radial artery (DRA) is the preferred inflow, while the cephalic vein, or a branch thereof, is the preferred outflow. In the absence of the DRA, the inflow alternatives are the palmar radial or palmar ulnar digital arteries, or use of a vein graft to provide an end-to-side anastomosis to the radial artery within the distal forearm.

All skin incisions must be designed preoperatively. A coronal incision, oriented slightly radial on the thumb, is usually preferred. In the foot, a V-shaped incision is performed in the dorsal aspect of the toe.

Intraoperative Considerations

Ergonomics

The proper position of the surgeon influences their precision, improves the movements, and stabilizes the large groups of muscles involved in this procedure. Therefore, holding the chair lower than usual to keep the surgeon's elbows below the level of the hand table maintains them relaxed in flexion, which will mitigate the use of the arm while stabilizing musculature that is active during elbow extension. The movement of the surgical instruments has to be driven by finger motions. Additional sterile towels can be placed to ensure that the hypothenar musculature of the hand is supported. Finally, the surgeon should sit straight up with their shoulders in comfortable position.

Loupes and Microscope

The ideal work distance should be 17 inches using a high magnification loupe, over 4 × , differently than 20 inches used by other specialties on 2.5× magnification. A closer working distance allows the surgeon to visualize the field with their elbows in slight flexion while relaxing the triceps and bicep muscles and allowing the wrists to be in a neutral position.

The microscope must be positioned to fit the surgeon's posture and not the reverse. A good focus must be reached by setting the microscope height at 20× magnification. This ensures that the focus of the surgeon and assistant will be synchronized irrespective of the magnification level used. Because visual enhancement comes in exchange for the visual field, the amount of magnification selected for specific procedures can also increase efficiency, so time is not wasted changing the magnification during surgical maneuvers.

Surgical Technique

Donor Site Dissection

Two teams should prepare the donor and recipient sites simultaneously with the patient in a supine position. The dissections should be done under tourniquet control with 3.5 to 6 power loupe magnification. One surgeon and a scrub nurse per team is the minimum of people required. Excellent illumination of the field is crucial; therefore, two overhead lights should be assigned to each group.

The great toe dissection starts with a V-shaped incision in the first web space with the vertex at the base of the great toe. The incision goes from the medial side of the first web space to the level of the metatarsophalangeal joint over the long extensor tendon (LET) point. At this point, a straight line up in the dorsum of the foot is extended proximally to facilitate identification of the pedicle, starting with identification of the saphenous vein. This vein is located in front of the medial malleolus.

Antegrade dissection through the subcutaneous tissue must be done to identify the major dorsal venous system, medially located to the LET. Laterally, the dorsalis pedis artery (DPA) is easily found. It must be dissected distally through the base of the first metatarsal area, where a communicating penetrating branch to the deep plantar system is visualized. In 60% of the cases, the DPA continues beyond this penetrating branch as a dominant superficial first metatarsal artery.

Once the dorsal vein, DPA, and LET are identified, the FDMA, a branch of the DPA, and the deep peroneal nerve must be dissected. The FDMA is usually located medially in the first web space, and the nerve will be close to the artery. This nerve must be carefully harvested because it will be coapted to the sensory branch of the radial nerve, increasing the quality of sensation in the dorsum of the hand. Additionally, proximal segments of this nerve can be harvested from the proximal side to be used as nerve grafts at hand.

An important anatomical landmark in the artery pedicle dissection is the short extensor muscle of the great toe. This muscle crosses the first metatarsal space, covering the DPA and its accompanying veins. Therefore, it has to be transected to facilitate artery identification. An extended incision of the muscle is recommended, considering that it will join the short extensor muscle of the hand, strengthening the opposition force of the transplanted toe.

In cases of absence of FDMA or deeper localization of this artery, a plantar V-shaped incision can be done to reach the first plantar metatarsal artery, which will be used as the central flap pedicle. Once the plantar incision is performed, identifying the lateral digital nerve of the great toe will expedite the detection of the lateral plantar digital artery, which will be located dorsally to the nerve. Following this artery in a proximal direction into the first web space, a bifurcation formed by the medial plantar digital artery of the second toe is found. At this point, the connection between the dorsal and plantar systems is identified as an H-shape connection. Both systems must be dissected, and the larger has to be chosen as the central pedicle of the flap. Sometimes, we can start the dissection on the second toe by isolating the medial digital nerve and tracing it proximally until the common plantar digital nerve to the great toe.

The plantar dissection of the foot continues with the elevation of a thin subcutaneous tissue skin flap proximal to the metatarsophalangeal joint. At this level, the flexor tendon sheath is open, and the flexor tendon is dissected proximally. In the medial aspect of the great toe, identification of the medial plantar digital nerve is critical because it lies in the capsule of the metatarsophalangeal joint, which will be incised circumferentially after the flexor tendon is transected. Special attention must be taken to avoid pedicle and extensor tendon damage located dorsally to the joint capsule. These structures are the last to be transected. In addition to this, an extensive plantar dissection should be avoided. Thus, vein grafts are the best option to consider when a longer vascular pedicle is needed ( Figs. 3 and 4 ).

Fig. 3.

( A ) Thumb amputation with healed lateral arm flap in preparation for toe transplantation, lateral. ( B ) Thumb amputation with healed lateral arm flap in preparation for toe transplantation, volar. ( C ) Great toe markings, dorsal foot. ( D ) Great toe markings, plantar foot. ( E ) Great toe, in situ harvest. ( F ) Great toe postharvest. ( G ) Great toe inset, volar. ( H ) Great toe inset, lateral.

Fig. 4.

Structural reassignment in great toe transplantation.

Notably, the team working on the hand must determine the length of the tendons, nerves, arteries, and veins necessary for the primary reconstruction. These measurements at the donor and recipient sides must be recorded. Afterward, the surgeon at the foot can proceed with the transection of the flexor tendon. Following disarticulation of the great toe, proof of the blood supply is performed by releasing the tourniquet with a vascular clamp in either the dorsal or the plantar system. Pink discoloration of the toe will be noticed. Warm saline or papaverine solution irrigation can be used to reverse vascular spasms. The tourniquet time recommended for the donor and recipient dissections should not be longer than an hour. Therefore, the pedicle transection is performed once optimal blood supply is confirmed, followed by the transection of the extensor tendon of the foot.

Usually, two-thirds of the metatarsal head is left with the sesamoid bones attached to the weight-bearing surface with a through and through stitch. After adequate hemostasis, closing of the skin layer is done, and a suction drain is put on the surgical site. It is recommended to leave more skin at the donor site to facilitate the closure and avoid wound complications. Immobilization of the foot by splitting is kept for approximately a week; after 3 weeks, the patient can start weight bearing. ¹⁹

Recipient Site Dissection

At hand, the cephalic vein, DRA extensor and flexor tendon systems, and digital nerves of the thumb must be dissected. The most frequent veins used for anastomosis to the venous pedicle of the foot are the cephalic vein or the dorsal venous arch. However, the previous injury could occasionally destroy the whole superficial venous system. In that scenario, using an accompanying vein with the radial artery is always a great option to drain the toe's venous system.

By placing the skin incision along the axis of the neurovascular bundle, efficient dissection of the neurovascular bundle can be performed using a Four Spread technique. A curved small tenotomy scissor is required for this part of the procedure. With the tips pointing up to prevent injury to the neurovascular bundle, the scissors are placed 70 degrees to the skin surface, and one large spread is performed perpendicular to the axis of the incision. Ample soft tissue separation is achieved, and the neurovascular bundle is identified. With the tips pointing away from the neurovascular bundle, a second large spread is conducted between the bundle and the tendon. Any small branches are identified and clipped with microclips. Branches that may hinder axial mobilization should be ligated and divided. A large third spread is then executed between the neurovascular bundle and the lateral skin. The injured/cut portion of the bundle is then held, and a fourth large spread is completed to separate the bundle from the dorsal skin.

The workflow consists of bone fixation by osteosynthesis, extensor tendon repair, flexor tendon repair, and artery, veins, and nerve coaptation.

Osteosynthesis

The approach to bone stabilization must be planned preoperatively. The ideal reconstructive scenario involves the presence of the proximal phalanx of the thumb, which will be used as a plug to insert the proximal phalanx of the toe into the medullary cavity. Thus, an oscillating saw is used to take off the articular surface and 2 to 3 mm of the proximal phalanx of the toe. Afterward, a high-speed burr is inserted into the medullary canal to model the place where the proximal phalanx of the thumb will be implanted with an overlap of 3 to 4 mm. Finally, using a fluoroscope will facilitate the fixation of the bones by using Kirschner wires (K-wires) placed in a longitudinal direction driven retrograde on the toe and antegrade into the thumb. Both K-wires are placed in parallel at the center of the bone union. One pin is advanced first to hold the reduction. Attention is then directed to the proper rotation of the digit using clinical inspection of the digit in relation to the hand cascade. The nail is a good landmark. If the rotation is satisfactory, the second pin is advanced. Intraoperative fluoroscopy is then used to confirm K-wire placement and anatomic reduction.

There are two ways to manage a short proximal phalanx of the thumb. First, the metacarpal head of the thumb, in conjunction with the articular surface of the proximal phalanx of the toe, creates a new MCPJ, which is fixed using nonabsorbable sutures joining the collateral ligaments, dorsal capsule, and volar plate. K-wires crossing the joint are maintained for approximately 2 to 3 weeks. The second method involves the use of longitudinal K-wires for osteosynthesis.

In creating a new MCPJ, the minimal remnant of the proximal phalanx of the thumb must be fixed to the articular surface of the proximal phalanx of the toe, pacing a K-wire across the joint and maintaining it for 2 to 3 weeks. At least four to five strong braided nonabsorbable sutures must be placed in the collateral ligaments, volar plate, and dorsal capsule to guarantee good fixation.

Tendon Repair

Following the bone fixation, the tendons are sutured using multiple weaves to guarantee a secure junction. The toe's LET is connected to the finger extensor tendon in a full extension position using a nonresorbable suture applying the Pulvertaft weave technique. The second to be sutured is the volar aspect of the toe to repair the flexor system. To avoid tendon adhesion, the flexor tendon must be repaired as far as possible from the level of the A1 pulley and away from the level of transplantation proximal to the flexion crease. Ideally, the length of the toe tendon should be enough to be able to perform this maneuver. In the absence of tendon or short tendons that cause tension in the anastomosis, the index proprius tendon for the extension side and the palmaris longus or the flexor carpi radialis on the flexor side can be used for tendon transfer to avoid suturing scarred and shortened tendons. Four-strand repair with epitendinous suture is recommended. ¹⁹

Considering that the IPJ of the toe is predominantly in a flexed position once transplanted to the thumb, some maneuvers can be performed to decrease the degree of flexion. These maneuvers include joint immobilization in extension for about 2 weeks or carrying out a secondary tenolysis.

Vessel Anastomosis

Subsequently, the arteries are joined through an end-to-end or end-to-side anastomosis under microscope magnification. The goal is to mobilize the ends together to allow a tension-free anastomosis. To achieve this, Serafin micro-clamps are placed as proximal and distal as possible to prevent the artery from retracting. The clamps are parallel to the skin, and the springs should be opposite the anastomosis location. Afterward, the arterial ends are cleaned, dilated, irrigated with heparinized saline, and papaverine topical is applied to both ends. Thus, the FDMA artery is anastomosed to the Dorsal Radial Artery (DRA). However, when the main pedicle is based on the medial plantar digital artery of the great toe, the ulnar digital artery of the thumb can be selected at the hand level, or even the DRA extended by a vein graft. The use of a 10–0 nylon suture is recommended for small vessels with a customarily six sutures to prevent leaks. However, extremely small vessels, such as in pediatric cases, could require using 11–0 or 12–0 sutures.

Technically, Jeweler's forceps are used to triangulate the artery placing the first suture in the posterior wall. The assistant should hold both arteries' ends while the surgeon ties them. Leaving one tail long of the first stitch to facilitate the artery rotation, the second stitch is placed 180 degrees opposite. To continue with the rest of the sutures, the assistant must take the tail of the back wall stitch and pull it toward themselves to rotate toward the surgeon. With the surgeon holding the front wall stitch toward themselves, the third suture is closer to the assistant, followed by a four-stitch placed closer to the surgeon, and so on until completing six stitches.

With exception of the first stitch, all the sutures are thrown by the surgeon and tied by the assistant. Special care must be taken during manipulating the arteries, which must be done by holding the adventitia. Excessive vessel tail retraction must also be avoided to prevent the artery wall from collapsing, which increases the risk of suturing the back of the artery wall. Two methods to reduce back wall sutures include first pulling on the suture at 180 degrees to the stitch placed to pull away from the back wall and second filling the vessel with the heparinized saline to tubularize the vessels prior to placing the stitch. Normal capillary refill must be evidenced.

Nerve Repair

The recipient's hand must be carefully evaluated, looking for neuromas to localize the nerve end. Identifying the digital nerves and dorsal radial nerve of the amputated thumb in the affected hand is crucial. However, these nerves can be avulsed far away from the amputation stump in some situations. Thus, dissecting more proximal until median nerve exposure in the forearm will help with the localization of the proximal neuromas.

The nerve ends can be mobilized using a similar technique to the one described for arteries. Once nerve ends are easy to mobilize, an end-to-end nerve coaptation free of tension can be achieved between the digital nerves of the thumb and the toe. In the absence of digital nerves in the amputated stump, the dorsal radial sensory nerve is an excellent choice to accomplish a more functional sensation. However, when a gap greater than 2 cm is present, a nerve graft should be used to fill the gap. Even though a nerve autograft can provide a satisfactory result, a cadaveric nerve allograft is preferably used to avoid the donor site morbidities and reduce operative time.

Skin

While hand surgeons generally prefer a meticulous, loose closure, too many skin sutures will strangle your replanted part because of the inevitable postoperative swelling. After all the structures are restored, the skin of the hand is closed with minimal sutures leaving open spaces between them to permit flow of excess fluids, thus preventing tissue pressure elevation and avoiding compromise of the vascular pedicle. In the presence of a raw surface that the skin flap from the transplanted toe does not cover, using split-thickness skin grafts is the best option. Meticulous closure is both time consuming and can be the cause of the loss of many otherwise well-performed toe transfer.

Carrying additional skin flaps with the toe transplanted can produce donor site closure inconvenience that will end in more scar tissue and donor site limitations. Therefore, bringing less tissue from the foot and covering the hand defect with split-thickness skin grafts is safer. Areas that serve as a donor site are the hypothenar eminence, volar wrist crease or proximal forearm, or the groin area. A spica splint is placed to immobilize the thumb.

Postoperative Considerations

The complete success of any surgical procedure depends on a good case selection, a flawless surgical technique, and an exhaustive and systematic postoperative follow-up. Therefore, the postsurgical care of all patients undergoing a great toe-to-thumb transplantation includes bed rest in a monitored unit for the first 48 hours with hand elevation and a heating pad applied to the surgical site. Strict finger checks every hour for 24 hours followed by every 2 hours for a day and every 4 hours on day 3 postsurgery. Antibiotic prophylaxis, low molecular weight dextran or low dose heparin at 500 units per hour, and 325 mg daily of acetylsalicylic acid are utilized.

Ischemic signs in the transplanted tissue must be urgently reported. A salvage rate of 90% has been reported when ischemic signs occur during the first 6 hours following the surgical procedure. ²⁵ In addition to physical examination (color, temperature, capillary refill, and skin turgor), several methods have been used for vascular monitorization that have shown to be trustworthy. ²⁶ One of them is quantitative fluorimetry, which has been used by Buncke et al ¹⁹ for over three decades. In the early postoperative stage, intravenous fluorescein injection is performed, and repeat fluorometer readings are obtained 10 and 60 minutes later. The absence of fluorescence rise at 10 minutes indicates arterial occlusion and a failure to fall the fluorescence at 60 minutes represents venous obstruction.

Another frequently used method for monitoring vascular pedicle flow is the Doppler ultrasound. Assessing pulse presence in an area previously marked corresponding to the pedicle allows for confirmation of vascular permeability. Additionally, some devices can sense heat conduction produced by blood flow. Considering that active blood flow maintains a constant temperature, rapid dissipation of heat suggests circulatory problems. ²⁷

The patient is usually discharged on day 5 or 7 postsurgery. Individualizing the postoperative plan is encouraged, but overall, every patient will have physical and occupational therapy, home health care, office follow-up, and psychotherapy.

Hand Rehabilitation

The success in the functional outcomes of a toe to thumb transplantation largely depends on hand therapy. For this reason, the Buncke protocol for hand rehabilitation is followed. ²⁸ The first dressing change is completed by the surgeon on the fourth day after surgery, and subsequent changes are performed by the therapist. At this time, a protective positioning splint is fabricated and placed in a dorsal or volar site depending on the location of the pedicle, with the wrist at a neutral position. Starting on day 4 and until day 10, gentle passive movements of the CMCJ active and passive wrist flexion, and the rest of the finger passive movements are recommended. Special attention must be paid to the presence of any signs of vascular compromise of the transferred thumb. For example, if the vascular pedicle is close to a joint, its passive motion is delayed until week 3.

Passive motion in the MCPJ and IPJ can start between days 10 and 14 with the wrist kept in a neutral position. Afterward, the active range of motion of MCPJ and IPJ is initiated. Lateralization of the MCPJ must be avoided in cases of collateral ligament reconstruction. The dynamic and passive movement of the transplanted thumb can start 5 weeks postsurgery, using a blocking splint to enhance isolated joint motion. Around week 8 postsurgery, the protective splint is changed to a Jobst glove. At this point, the progressive initiation of resistive and strengthening activities is prescribed. Functional electrical stimulation to aid in function recovery after muscle transfer and sensor reeducation program can usually start in weeks 5 and 8, respectively.

Buncke et al ¹⁹ have previously reported improved sensory and motor recovery following this protocol. The authors reported 8 mm of two-point discrimination with a range of 5 mm to protective sensation in a cohort of 73 patients. Additionally, the functional motor recovery was 63% for the MCPJ and 59% for the IPJ compared with the uninjured side, corresponding to 44 and 40 degrees of range of motion, respectively. The percentage of grip and pinch strength recovery was 77 and 67% for each case ( Fig. 5 ).

Fig. 5.

Great toe transplant 6 months postop. ( A ) Volar. ( B ) Dorsal. ( C ) Lateral grip. ( D ) Volar grip. ( E ) Lateral. ( F ) Opposition.

Donor Site Morbidities

The biomechanical alteration of the foot after a toe harvest can lead to functional impairment, sometimes overshadowed by the enhancements in hand function and appearance. Approximately 20.2% of patients who undergo toe harvest surgery will present some grade of donor site complications and functional impartment. ²⁹ There is a higher morbidity rate associated with great toe transfer (21.8%) compared with second toe transfer (14.5%). Despite this, there is lower morbidity associated to great toe transfer than transfer of other toes (23%), such as combined first or second transfer or isolated third toe transfer. Furthermore, free great toe transfer has a lower reintervention rate (4.5%) than second toe transfer (16.6%). These results were published by Sosin et al ²⁹ in 2015, after completing a systematic review and pooled analysis of functional donor site morbidity after a vascularized toe-to-hand transplantation.

In the same study, Sosin et al found that the complication rate was 19.1% for great toe transfers. Among these complications, wound dehiscence represents 7.6% of cases, and no wound infections or skin necrosis were observed. Pain or discomfort and scar or callus formation also represent 4.6 and 6.9% of cases, respectively. Furthermore, some predictable deformities such as sesamoid retractions, a descended first metatarsal head, and increased load over the second through the fifth metatarsal head raise the probability of ulcers or plantar pad erosion under the second and third MTPJ or callus formation.

Lastly, Buncke et al ¹⁹ reported a 5% rate of secondary interventions in the donor site. The authors also reported that, 95% of patients returned to their baseline activity level, with 70% achieving it within a year of the procedure. Regarding patient perspective, Tsai et al ³⁰ demonstrated that patients undergoing toe-hand transplantation had improvement in their health-related quality of life postoperatively using three validated patient-reported outcome measures. Additionally, a better physical and emotional well-being was observed with no significant donor site morbidity ( p  > 0.6524). ³⁰ Therefore, the functions gained in hand far outweigh donor site morbidity. ³¹

Toe Wraparound

Some authors have described technical modifications of the traditional great toe to thumb procedure. In 1980, Morrison et al ³² defined the wraparound technique using a microneurovascular composite flap focused on the lateral aspect of the great toe's skin, including the pulp and nail, to cover the thumb defect.

In cases of thumb degloving injuries that do not require bone and tendon reconstruction, the wraparound technique is an excellent procedure to harvest the soft tissue at the toe. The tissue harvest technique is similar to the full toe harvest ( Fig. 6 ). Once the dissection is completed, an incision on the medial aspect of the toe is performed down to the periosteum. Using a freer elevator, the soft tissue is peeled from the periosteum and the toe wraparound flap is used to wrap the thumb. Afterward, all the bone components of the toe are removed, considering the modest donor site morbidities, to facilitate the closure with local flaps at the donor site ( Figs. 7 and 8 ). Consequently, in cases of amputations proximal to the MCPJ with bone loss, the classic great toe transplant is the first choice for thumb reconstruction.

Fig. 6.

Structural reassignment in great toe wraparound flap.

Fig. 7.

Great toe wraparound flap, artist rendering.

Fig. 8.

Great toe wraparound flap, clinical case. ( A ) Soft tissue amputation of thumb, dorsal. ( B ) Soft tissue amputation of thumb, volar. ( C ) Great toe wraparound markings. ( D ) Great toe wraparound, in site harvest. ( E ) Donor site closure. ( F ) Great toe wraparound inset, dorsal. ( G ) Great toe wraparound inset, lateral.

Conclusion

Toe to thumb transplantation is considered the gold standard for restoring pinch, sensitivity, strength, and aesthetics of the hand with well-tolerated donor site morbidity. Consistent and predictable results can be achieved by applying the aforementioned surgical principles.

Funding Statement

Funding None.