Surgical Therapy
The goal of thumb reconstruction is to restore function, as well as to provide the hand with an acceptable appearance and to keep donor-site morbidity to an acceptable level. The level of amputation determines the reconstruction plan. The predicted outcome of surgery generally favors reconstruction when an amputation has occurred distal to the MCP joint and has therefore left the first web space, as well as the thenar muscles (including their insertions), preserved.
Preoperative Details
Thorough discussion with the patient and the patient's family is necessary prior to surgery to set realistic expectations for the restoration of thumb function. Despite a successful reconstruction, the thumb may never return to a pre-injury level of function. The patient and surgeon should be aware of this possibility. Similarly, in the child born with a hypoplastic or absent thumb, the reconstructed thumb will never be the same as the contralateral, nonaffected thumb. Parents must recognize this fact when thumb reconstruction is performed.
Intraoperative Details
Distal-third amputations
Although technically challenging because of the size of vessels that are distal to the IP joint, successful replantation of the thumb tip restores length, glabrous skin, and the nail. These components, combined with the return of sensibility, maximize thumb dexterity and function. [15] In cases in which replantation is unsuccessful or is not desirable, healing by secondary intention, skin grafting, revision amputation, or local flaps are options for wound coverage. [16, 1] Partial or complete thumb amputation distal to the IP joint has been described as "compensated amputation" because functional impairment may be minimal. [17, 18]
Local flap options include the following:
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Moberg flap - The Moberg flap, as shown in the images below, allows advancement of volar skin of up to 1.5 cm in order to provide stable, sensate skin. The flap is raised at the level of the flexor tendon sheath in a distal-to-proximal relation to the MCP flexion crease and includes the 2 volar neurovascular pedicles. [19] Use of this flap may lead to stiffness or flexion contracture at the IP joint.
Moberg flap raised just above the level of the flexor pollicis longus tendon sheath.
Radial view of the markings for a volar advancement flap with modification of the incision at the base to allow closure in V-Y fashion after distal phalanx shortening.
Volar advancement flap with modification of the incision at the base to allow closure in V-Y fashion after distal phalanx shortening.
Radial view of the closure of a thumb defect with a Moberg volar advancement flap.
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Littler neurovascular island flap - Popularized by Littler, this flap, as shown in the images below, supplies sensate, glabrous skin from the ulnar side of the long or ring finger to the volar aspect of the thumb. [20] Problems with cortical reintegration and cold intolerance have been reported and have led to the decreased use of this flap for thumb reconstruction. A study by Wang et al reported success with a modified Littler flap, devised to reduce complications associated with the flap’s more common design. In the modified version, the dorsal branch of the proper digital nerve innervated the flap, as did the proper digital nerve from the middle finger’s ulnar aspect or the ring finger’s radial aspect. (A nerve graft from the proximal section of the ispsilateral dorsal branch of the proper digital nerve was used to repair the proper digital nerve at the donor site.) Postsurgical results showed nearly normal scores for the thumb and donor finger with regard to the static two-point discrimination test and the Semmes-Weinstein monofilament test, with total active motions also being close to normal. [21]
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First dorsal metacarpal artery flap - Also known as the kite flap, this is another reconstructive option that can bring sensate skin to the injured thumb. [22, 23] The flap, as shown in the images below, which uses the first dorsal metacarpal artery for its blood supply, employs skin from the dorsal-radial aspect of the index finger. Pedicle length may limit this flap's use for distal thumb defects. As with the Littler neurovascular island flap, cortical reintegration may be an issue with the first dorsal metacarpal artery flap.
Postoperative appearance of a thumb tip after coverage with a first dorsal metacarpal artery flap.
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A microvascular toe transfer, or wraparound flap, is the most sophisticated reconstructive option for amputation injuries to the thumb, as shown in the images below. Since the technique allows restoration of a near-normal pulp and nail, it also provides the best functional results. [7]
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A study by Gu et al indicated that the use of free toe flaps is a reliable means of reconstructing finger and thumb soft tissue defects. In the study, six thumbs and 15 fingers were reconstructed in adult patients, with flaps taken from the lateral aspect of the great toe (9 patients) or the medial aspect of the second toe (12 patients); the average follow-up period was 18.4 months. The investigators reported that all of the flaps survived, with none of the patients requiring urgent surgical revision for postoperative thrombosis. Patients scored an average of 4.8 mm on the static two-point discrimination test. [24]
Markings for a free tissue transfer of great toe pulp to restore a volar thumb defect.
Postoperative view after a free tissue transfer of great toe pulp to restore a volar defect.
Middle-third amputations
When the level of injury is distal to the MCP joint and proximal to the IP joint, length preservation becomes more of an issue because of the effect that a shorter thumb has on pinch and grip strength. Prior to the era of microsurgery, treatment options included phalangization (ie, deepening of the first web space) and osteoplastic reconstruction. [3, 25]
Additional length for the thumb stump can be obtained using the following methods:
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Placement of a distraction device on the thumb metacarpal after osteotomy, with gradual lengthening [17]
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Four-flap Z-plasty to deepen the first web space [26]
Osteoplastic thumb reconstruction offers a staged approach involving the placement of an iliac crest bone graft within a tubed pedicle flap from the groin or epigastric area and subsequent flap division to provide a stable, reconstructed thumb with some gain in length. [25] A neurovascular island flap may be necessary to bring sensate tissue to the reconstructed thumb at the time of flap division. [29] However, nonmicrovascular techniques have not been widely used because they can result in an unsatisfactory appearance, a lack of sensation, difficulty with cortical reintegration, and bone graft resorption. [30]
Microsurgical techniques for toe-to-hand transfer have revolutionized the treatment of thumb amputations at the middle or third level by restoring stability, mobility, strength, and sensation, as well as by providing good appearance. By allowing the transfer of functioning units that are analogous to the lost structures, microvascular reconstruction generally provides results that are functionally and aesthetically superior to those of other techniques. The first dorsal metatarsal artery in the foot allows transfer of the great toe or second toe on a longer vascular pedicle than does a transfer based on a digital artery. The reconstructive surgeon should be aware of variations in the arterial supply to these toes. [31]
The wraparound flap, introduced by Morrison, offers the advantage of generally better aesthetics than does a classic toe-to-hand transfer. [7] In the wraparound flap, a filleted flap of skin, digital nerves and vessels, and a nail is wrapped around a degloved distal phalanx or an iliac crest bone graft. This technique allows better size match to a normal thumb, although motion at the IP joint is not restored. The trimmed toe flap is a modification of the wraparound flap; described by Wei and colleagues, the trimmed toe flap preserves some IP joint motion by combining a longitudinal osteotomy of the phalanges with a reconstruction of the lateral collateral ligament. [32]
A study by Troisi et al indicated that in thumb or finger reconstruction, the trimmed great toe flap maintains digit length and provides good aesthetic results, with donor site morbidity being comparatively low. In the report, seven thumbs and three fingers were reconstructed using the trimmed flap, with the only complications being two minor ones. Following wound healing, patients had a median overall Michigan Hand Outcomes Questionnaire (MHOQ) score of 95.44. The single case of donor site morbidity consisted of a spontaneously resolving foot hematoma. [33]
Proximal-third amputations
Reconstruction becomes more difficult, but also more important, when a thumb amputation has occurred proximal to the MCP joint. [34] A study by Kovachevich et al found good results with immediate great toe–to-thumb transfers in patients who had undergone amputation of the thumb through the base of the proximal phalanx, the result of locally aggressive benign or malignant tumors. Among the three patients in the study, all of the transferred toes survived, with each patient attaining full thumb opposition and protective sensation. [35]
Reconstructive options to restore thumb function also include the transfer of the second toe to the thumb or pollicization of the index finger. A second-toe transfer can restore more length than a great toe transfer can by including the MCP joint and a segment of the second metatarsal. [36] A second-toe transfer is also indicated when a significant size discrepancy exists between the great toe and the thumb or when a patient does not want to lose the great toe for aesthetic, cultural, or functional reasons. [37] In patients with traumatic amputation of the thumb, other digits in the hand, such as the index or long finger, also may be injured or amputated. These "spare parts" may then be transferred to the thumb stump for reconstruction. [38]
With a more proximal amputation, one resulting in the loss of intrinsic muscles and the destruction of the CMC joint, pollicization of another finger to restore thumb function and opposition may be the only option to offer. [25] The index finger is the most commonly pollicized digit, although the long and ring fingers have been used. [39, 40, 41] The transposed finger provides length, sensation, proper positioning, and motion for grasp and pinch functions, with acceptable donor-site deficits (although retraining may be difficult in an adult patient). [42, 43]
Congenital absence
The deficit from a proximal-third amputation most closely resembles that of a congenitally absent thumb (a Blauth type V thumb). However, the distinction between a normal thumb that has been amputated and congenital aplasia or hypoplasia of the thumb must be recognized. Normal structures were present in the amputated thumb prior to injury, whereas in thumb aplasia or hypoplasia, bone, tendons, nerves, and vessels may be poorly developed or completely absent, as shown in the images below.
For these reasons, pollicization of the index finger is recommended for reconstruction of the congenitally absent thumb, as shown in the images below. [9]
The principles of pollicization are as follows:
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Well-designed skin incisions to reduce scar contracture in the first web space
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Careful dissection of the neurovascular bundles to the index finger
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Shortening of the index metacarpal to achieve the desired thumb length
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Proper positioning of the thumb with hyperextension of the proximal phalanx on the metacarpal head
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Anchoring of the pollicized digit to the distal carpus
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Tendon reconstruction, including transfer of the first palmar and dorsal interosseous muscles to the lateral bands of the index finger to provide abduction and adduction, respectively [9]
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Final stabilization and positioning with appropriate tension of transferred tendons
Complications
Sequelae to finger trauma may include edema, hypertrophic scarring, nail deformity, cold intolerance, abnormal sensitivity, joint stiffness, and generally decreased function. Complications that are directly related to reconstructive surgery include postoperative bleeding, infection, anesthesia-related problems, complex regional pain syndrome, and the loss of a skin flap, a replanted or transferred part, or a pollicized digit.
Outcome and Prognosis
As reported by Buncke and others, toe-to-hand transfer for thumb reconstruction can provide excellent end results and a high degree of patient satisfaction. [2, 44, 45, 46] The survival rate of these transfers has been reported to be as high as 98%, with 2-point discrimination of 8 mm or less in 80% of cases and, following reconstruction of the dominant thumb, a grip strength that is equal to 80% of the noninjured hand's grip strength.
In addition, most patients who have undergone toe-to-thumb transfer return to work and resume previous leisure activities, leading to a high degree of patient satisfaction. These findings are supported by Chung and Wei, who found better hand function in patients with toe-to-thumb transfer than they did in patients with a thumb amputation. [47]
In his review of index finger pollicizations employed to treat the congenital absence of a thumb, Manske found that patients had an average active range of motion of 98º in the pollicized digit (half the range of a normal thumb). He also determined that the average grip strength among these patients was 21% of normal grip strength and that their pinch strength ranged between 22% and 26% of normal pinch strength. Although these values are significantly lower than normal, they still indicate that index finger pollicization provides functional and aesthetic improvements over an absent thumb. [48, 49]
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Diagram of a Moberg volar advancement flap being used for a thumb tip defect.
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Marking for the radial incision of a Moberg flap.
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Moberg flap raised just above the level of the flexor pollicis longus tendon sheath.
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Markings for a volar advancement flap with modification of the incision at the base to allow closure in V-Y fashion after distal phalanx shortening.
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Radial view of the markings for a volar advancement flap with modification of the incision at the base to allow closure in V-Y fashion after distal phalanx shortening.
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Volar advancement flap with modification of the incision at the base to allow closure in V-Y fashion after distal phalanx shortening.
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Thumb tip defect that is amenable to closure with a Moberg volar advancement flap.
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Incision marking for a Moberg flap. The neurovascular bundle should be kept with the volar advancement flap.
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Bridging vessel to the neurovascular bundle on a volar flap.
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Flexion at the interphalangeal joint to allow closure.
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Volar view of the closure of a thumb defect with a Moberg volar advancement flap.
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Radial view of the closure of a thumb defect with a Moberg volar advancement flap.
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Diagram of a Littler neurovascular island flap for the coverage of a thumb tip defect.
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Intraoperative view of a Littler neurovascular island flap.
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Postoperative view of a Littler neurovascular island flap.
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Second postoperative view of a Littler neurovascular island flap.
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Markings for the pedicle of a first dorsal metacarpal artery flap.
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Dissection for a first dorsal metacarpal artery flap.
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Isolation of the pedicle for a first dorsal metacarpal artery flap.
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Postoperative appearance of a thumb tip after coverage with a first dorsal metacarpal artery flap.
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Second view of the postoperative appearance of a thumb after coverage with a first dorsal metacarpal artery flap.
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Free tissue transfer of great toe pulp to restore a volar thumb defect.
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Markings for a free tissue transfer of great toe pulp to restore a volar thumb defect.
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Postoperative view after a free tissue transfer of great toe pulp to restore a volar defect.
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Dorsal view of the clinical appearance of a Blauth type IV pouce flottant thumb.
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Volar view of the clinical appearance of a Blauth type IV pouce flottant thumb.
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Radiograph of a pouce flottant thumb
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Pollicized index finger for thumb reconstruction at 2 weeks after surgery.
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Functional use of a pollicized index finger at 8 weeks after surgery.
