Multidigit injuries are common. An amputated finger that is not replantable becomes a privileged donor site for harvesting tissue for the reconstruction of neighboring fingers. This is a unique opportunity that must be seized at the time of the emergent procedure. The morbidity of the harvested finger is zero, and all innovative techniques are indicated to allow the salvageable neighboring fingers to benefit from this tissue bank principle.
Possible Uses of the Tissue Bank
All types of tissues can be used according to this principle. Depending on the clinical scenarios, a tissue unit can be used as a conventional nonvascularized graft or as a flap with its own blood supply.
In the latter case, it may be an island flap or a free flap with microsurgical anastomoses.
Skin and Tissue Bank
This is the simplest illustration of this principle. All types of skin grafts can be harvested from a finger destined for amputation. Where possible, we choose skin with texture and thickness adapted to the recipient site. Note that the palmar skin of the fingers is a poor donor site because of its thickness. Despite thorough defatting, full-thickness skin grafts from the palmar surface of the fingers are difficult to apply.
A finger can be filleted from its skin covering before being amputated. The skin flap thus obtained is used to cover a neighboring finger, the back of the hand, the first commissure and any neighboring area. The skin available will, however, only remain vascularized if the incisions respect the rules of flap harvesting, which depending on the case, will be an axial-pattern or random-pattern flap.
All island flaps described in Chapter 9 , whether dorsal or palmar islands, can be dissected on a finger destined for amputation.
Similarly it is possible to dissect a free skin flap on a digital vascular pedicle. Most often they are free pulp flaps, but nothing prohibits use of the palmar skin of P1 or P2 or the dorsal skin of P2 as appropriate. To have a vein of sufficient size, we dissect the dorsal aspect of the finger. This requires inclusion of a dorsal skin paddle in the palmar flap, continuous with the vein.
Nail and Tissue Bank
An amputated finger is the ideal site for a nail bed graft. We can harvest thin or thick nail bed grafts here but also total matrix grafts. Finally, even if it is an opportunity we have never encountered in practice, we can consider harvesting a vascularized nail graft on an amputated finger.
Bone and Tissue Bank
Part of a phalanx may be harvested to reconstruct a segmental defect on an adjacent finger. Such a graft must necessarily be inserted between two vascularized bone ends for optimal revascularization and avoidance of resorption. Given the long delays in consolidation observed in these circumstances, the osteosynthesis should be solid.
Vascularized Bone Grafts
It is possible to remove a phalangeal bone graft in continuity with a palmar vascular pedicle. The vascularized graft should then also include the soft tissues and the dorsal skin to include a dorsal vein for venous return. Such a graft would undoubtedly consolidate and integrate faster than a conventional graft. In fact, placed in a favorable tissue environment, small-sized conventional bone grafting used on the hand can be integrated without difficulty. The need for a vascular graft arises, especially with joints.
Joints and Tissue Bank
“Partial” Osteochondral Grafts
Despite numerous experimental studies, no synthetic substitute for cartilage has emerged in practice. When confronted in an emergency with a joint fracture containing an osteochondral defect, it may be tempting, if we have a nonreplantable amputated finger, to remove a bony and cartilaginous fragment of corresponding size.
The composite graft should reproduce the curvature of the recipient site in the three planes as closely as possible. Fixation of these small-sized composite grafts is tricky. When their size allows it, a microscrew in a nonarticular area or simple Kirchner wires may be used. For fragments of even smaller size, we sometimes use a simple adherent (Tissucol). In these circumstances the sole aim of the glue is to position the fragment; this is not osteosynthesis, and immobilization of the joint is necessary.
Nonvascularized Hemiarticular and Articular Grafts
The observations reported in the literature usually concern joint transfers harvested from the foot. Eades reported a case using a proximal interphalangeal (PIP) joint from a middle finger to reconstruct the metacarpophalangeal (MCP) joint of the ring finger. Whether they are harvested from the foot or the amputated finger, the behavior of these nonvascularized grafts is the same. The bone undergoes a phase of necrosis followed by revascularization. At the same time, the hyaline cartilage is replaced by fibrocartilage.
Despite the systematic histologic alteration of the cartilage, occasional successes have been reported, with preservation of a joint space on radiography and clinically useful mobility. These clinical successes are mostly reported for reconstructions of the MCP joints, with rotation arcs sometimes reaching 70 degrees. The functional results are usually more modest for PIP joints. It is likely that the small size of these articular or hemiarticular grafts, and therefore their rapid revascularization, differentiates them from larger joint grafts and partly explains these few good results. Nevertheless, applying this tissue bank principle, the use of a nonvascularized joint graft is only one salvage solution for an MCP or a PIP joint, to be deliberated upon with a prosthetic solution.
Vascularized Osteoarticular Transfers
Vascularized joint transfers are only indicated for MCP or PIP joints; the distal interphalangeal (DIP) joint can always be arthrodesed. The superiority of vascularized joint transfers relative to conventional grafts has been well established.
The hyaline cartilage of the joint surfaces remains unaltered, bone healing is faster and the possibility of growth persists when the graft contains a fertile epiphysis. Under the tissue bank principle, the transfer of these joints can be in the form of free or pedicled transplants:
The DIP joint of a long finger can be used for reconstruction of the PIP joint of another finger. Its use to rebuild the DIP joint is theoretically possible and might seem logical. It is rare indeed that the functional imperative and the practical possibility of such a reconstruction can coexist.
The PIP joint of a long finger can be used for reconstruction of another PIP joint or an MCP joint.
As regards the MCP joint itself, the few opportunities that arise most often consist of translocations of a joint island toward the adjacent finger.
Whether pedicled or free flaps, these transfers always include at least one dorsal skin island, allowing for venous drainage and monitoring through the vascularity of the flap.
Tendons and Tissue Bank
In practice, these are almost exclusively nonvascularized conventional tendon grafts. A tendon graft can be harvested from the extensor apparatus of a finger destined for amputation and serve as an intercalary graft for reconstructing the extensor tendons of a neighboring finger. In the palm and dorsum of the hand, it is also possible to divert an extrinsic tendon (flexor or extensor) to reconstruct an adjacent finger.
Nerves and Tissue Bank
An amputated finger can provide a nerve graft perfectly adapted to reconstructing a digital nerve. The absence of morbidity justifies performing this grafting in emergency situations. The use of nerve-artery composite grafts is also possible when there is loss of a palmar neurovascular pedicle. In these circumstances the nerve graft will benefit from multiple vascular connections between the collateral artery and the nerve. It is hoped that this type of nerve graft will behave as a vascularized graft.
Vessels and Tissue Bank
Venous grafting is frequently necessary when one has to revascularize one or more severely mutilated fingers. When a nonreplantable finger is available, it can be used as a donor site for the harvest of arterial grafts from a digital or palmar artery. This option makes it possible to avoid harvesting a vein graft. One may also combine skin coverage and revascularization by performing an arterial flow-through or venous flow-through flap.