Reconstruction of single finger amputations

Unlike the loss of the thumb, which causes a 40% to 50% loss of global hand function, single finger amputations produce insignificant functional impairment for most patients [15]. Single finger reconstruction with toe transplantation has therefore not gained wide acceptance. In select patients, however, particularly those with distal amputations and higher manual functional or esthetic demands because of their occupations or hobbies, single finger reconstruction can usually offer satisfactory results even if performed solely for cosmetic reasons [12,16-18]. The livelihood of some individuals depends on a full set of accurately positioned functional finger pulps and nails, particularly musicians.

The flexor digitorum superficialis tendon insertion into the middle phalanx defines the level that distinguishes between distal and proximal finger amputation [17,19]. Distal finger reconstructions, especially of the radial two digits, using composite flaps from the toes often provide particularly valuable functional and esthetic results [17-19]. A transplanted composite toe flap can import close versions of a distal finger's fingerprinted pulp and the nail complex, which enhances pulp sensibility and fine-tip pinch [20,21]. Only replantation can provide a superior match for these specialized structures.

Reconstructive options for distal amputations, depending on the defect, include vascularized nail, pulp, hemipulp (Fig. 1), onychocutaneous, and wraparound flaps from a lesser toe [17-19,22-26].

Table 1

Principles and key points for the preservation of tissues when debriding the injured hand that may subsequently benefit from toe-to-hand transfer

Structure

General principle

Key points

Bones

Joints

Flexor tendon

Extensor tendon

Pulleys Nerves

Vessels Skin

5 mm of bone is enough for stable fixation of the transplanted toe

Preserve functioning joint surfaces, capsules, and collateral ligaments

Preserve all tendon insertions and maximal length

Preserve the extensor system

Preserve especially the A2 and A4 pulleys Preserve viable sensory nerves

Preserve healthy vessels Preserve all clearly viable skin

Preserve native finger joints by never sacrificing their immediately distal viable bone Normal finger length can be restored if the amputation stump is not shortened beyond the middle of the proximal phalanx

Proximal joint surface in the transplanted toe can articulate with a preserved distal joint surface in the finger to restore range of motion as well as length Flexor digitorum profundus provides stability in power pinch Flexor digitorum superficialis insertion represents the functional length of a finger

Extensor apparatus and intrinsic muscle insertions maintain balance in extension for the transplanted toe Important to prevent bowstringing of the native or transplanted flexor tendons Sensory reinnervation of the transplanted toe is expedited if viable nerve length is not sacrificed proximally Good size match for donor toe vessels is more likely to be available for the microsurgeon if vessel lengths are preserved in the finger Although a pedicle groin flap can import fresh uninjured skin, viable native skin is usually of superior quality

Amputations through or proximal to the distal in-terphalangeal joint are best reconstructed by including the corresponding joint in the harvested toe, together with its tendons intact [19]. The inclusion of both interphalangeal joints in second or third total toe transplants can often restore adequate digital length and cascade for stumps as proximal as the middle of the proximal phalanx [27]. Patients undergoing more proximal reconstructions may need to accept a slightly shorter resultant finger.

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