Video content accompanies this article at http://www.plasticsurgery.theclinics.com .

Microsurgery had a great impact on upper extremity reconstruction by extending the indications of limb salvage in various conditions. With the standardization of the technical aspects of vessel anastomosis of even submillimetric diameter, levels of success are high. The enhanced skill levels and revisiting anatomy have helped us refine our practice to improve outcomes and enhance patient experience. Every aspect of upper limb surgery has been influenced by microsurgery. The current concepts of microsurgical reconstruction of the upper limb are discussed under various aspects of upper limb surgery.

The accepted indications of replantation differ from high-volume centers to low-volume centers, with a low threshold for replantation in centers receiving huge volumes. While fingertip replants and replantation of digits distal to flexor digitorum superficialis insertion have been accepted for long, currently, even zone 2 amputations are replanted to get as good results as could be obtained with combined zone 2 flexor injury associated with open fracture of the proximal phalanx ( Fig. 1 ). An absolute contraindication for digit replantation that remains is a single-finger or 2 finger amputation with avulsion of flexor and extensor tendons from the musculotendinous level ( Fig. 2 ). Replantation of such fingers will affect the function of the other normal fingers. However, a similar amputation of the thumb with the avulsion of flexor pollicis longus and extensors is an absolute indication for replantation ( Box 1 ).

( A–E ) Total amputation of right index finger in zone 2. Situation at 7 months after replant, full range of movement after tenolysis of extensors and flexors.

Single finger avulsion amputations with avulsion of long flexor and extensor at the musculotendinous level remains a contraindication for replantation.

A great shift has occurred in the indications of major replants. Over a period, guillotine amputations have become rare, with crush and avulsion amputations being commonplace. In amputations distal to the wrist, functional reconstruction is possible with flaps and toe transfers. In forearm or arm-level amputations, no such reconstructive procedures are possible and prosthesis is the usual option. Although hand transplantation is an alternative, it is currently recommended only for bilateral amputees. Most mangled upper extremities are unilateral injuries, and till the effects of immunosuppression are reduced to very acceptable levels, reconstruction of mangled extremities will be the recommendation.

Technical refinements have made replantation of crush avulsion major amputations much safer. Radical debridement, which involves the excision of muscles in the distally avulsed tendons and the shortening of the bones, is a major step. The former reduces the reperfused muscle load, and the latter, in many instances, facilitates a direct repair of good vessels and nerves and obviates soft tissue cover. Higher rates of primary bone union occur by this method due to the excision of bone devoid of periosteum. Direct repair of structures also reduces ischemia and operation times, reducing complications and cost of care. Up to 10 cm of shortening in either the forearm or the arm segment has not affected function. Once the limb survives, the function can be enhanced by secondary procedures. Quick surgery and approximation of good nerves frequently enable intrinsics to recover, greatly facilitating secondary reconstruction ( Fig. 3 ).

( A–G ) Total crush avulsion amputation of the right forearm. Postdebridement picture showing the removal of all the muscles from the distal tendons and the extent of bone shortening. Skeletal fixation by creating a one bone forearm. Replant was successful and ready to undergo a free functional muscle transfer for function.

Has the current microsurgical capability helped develop scoring systems to predict salvage versus amputation of major upper limb injuries? Despite more than half a century of research, a dependable scoring system for salvaging the upper extremity has not come into vogue. The skill levels, attitude, and infrastructure of the surgical team greatly affect decision-making. It is difficult to factor this surgeon element into the overall scoring system. A well-reconstructed upper limb over a period outscores function obtainable through the best available prosthesis.

Major crush injuries can be associated with long-segment loss of bones, nerves, entire compartments of muscles, and extensive soft tissue loss. When they occur together, they can pose a great challenge. Microsurgery helped us cross this hurdle by providing solutions to cover large gaps with a pair of anastomosis.

In the upper limb, sensory innervation is important in the reconstruction of fingertips and the volar aspect of fingers and palms. In these areas, free flap reconstruction with repair of the nerves supplying the flap is important. For pulp and distal finger defects, toe pulp transfers produce excellent functional and esthetic outcomes. Cutaneous perforator flaps with nerves supplying the flaps are the next best option. For example, palm defects treated with an instep flap continue to be the best color match, which, when innervated by a fascicle of the median nerve through the medial plantar nerve, yields adequate sensation.

Though much research has been done on the sensory recovery of the free flaps in the upper limb, most reconstructions are done for soft tissue cover without nerve approximation. The reason is that the nerves often pass through the flap but do not supply the harvested skin territory. Over a period of years, adequate sensation does recover to functional levels. Smaller and thinner flaps achieve good sensory recovery as assessed by sensory cutaneous pressure testing by Semmes Weinstein Monofilament testing.

After free tissue transfer, small-fiber function recovers with a nerve growth in the direction from the flap margins to the center, likely by way of collateral axonal sprouting from the surrounding nerves in the flap. The myelinated fibers recover slowly.

In posttraumatic long-segment bone loss in the forearm or arm, with the free fibula transfer being commonplace, long bone gaps are no longer an indication for amputation. The critical limit of a 5 cm gap is adhered to in most centers while deciding between a free fibula and a nonvascularized bone graft. Gradually, the acceptable distance is becoming shorter. In the upper limb free fibula finds its best use in the management of infective nonunion ( Fig. 5 ). Other donor sites for long bone gaps like iliac crest are not much preferred currently.

( A–F ) Post osteomyelitis nonunion of both bones of the forearm in a 11 year old child. Child had nonvascularized bone graft with failure. Harvested free fibula with a skin island. Fixation with an intramedullary pin creating a one bone forearm. Skin island is essential to facilitate closure, well united bone at 2 years with good functional outcome.

A bone with growth center is essential to prevent deformity when reconstructing children, particularly the joint surfaces. Microsurgery with transfer of the upper end of the fibula is the only way to provide a joint surface coupled with growth potential.

Combining vascularized fibular epiphysis with an allograft yields good results and lower fracture rates. Technical refinements are continually made to reduce the donor site morbidity at the knee and the weakness of the peroneal nerve innervated muscles.

Most of the time, microsurgical free fibula transfer is for salvage, while small-sized vascularized bone grafts facilitate early bone union and enhance function. The most commonly used bone flap is the medial femoral condyle (MFC) bone graft, which is used for varied indications like as fixing the nonunion of the scaphoid to that of the tubular bones of the hand and even recalcitrant nonunion of the clavicle. ^, Currently, the extensive use of MFC bone graft has shifted the indication to cater to small bone defects with bone union rates up to 95%. With a good understanding of anatomy and surgical skills, MFC vascularized bone graft has less donor site morbidities. In addition, a vascularized periosteum-only flap can be used to wrap the fracture sites to enhance the rates of bone union to up to 99%.

Using a combination of tissue from the foot for digital reconstruction can enhance function. Isolating the blood supply of the dorsal skin, split toes, and the interphalangeal joints or a combination of them, has helped us perform good functional reconstructions of fingers. Interphalangeal joints need stability and mobility, and research is being done to improve them through prosthetics and surgical transplants. Proximal interphalangeal joint (PIP) joints of the second toe with a small skin island and extensor tendon repair combined with centralization of lateral bands to improve the extensor lag is now a viable option. An increase in the range of motion of the PIP joint by decreasing the extensor lag to 17.9° makes the outcomes of vascularized joint transfer similar to other existing techniques.

Microsurgery finds a place in reconstructing children’s hands with loss of digits in symbrachydactyly and constriction ring syndrome. ^, In these conditions, the presence of a thumb and a finger makes functional pinch and grasp possible ( Fig. 6 , Videos 1–3 ). If there is redundant soft tissue beyond the bone in the digits, a nonvascularized free phalangeal transfer is recommended before the age of 1 year. Microsurgery, perhaps, can be the only solution in monodactylous and adactylous hands. In such cases, transferring a single second toe greatly adds to function. Technically, vessel repair in children has not been found to be difficult with the increasing sophistication of microscopes and microinstruments. Though replantations have been done even in newborns, second-toe transfers in children are done around 3 years of age. There may be a paucity of good tendons in the forearm. Hence, optimal positioning of the transferred second toe in relation to the existing finger is important to achieve the desired pinch and grasp. Harvest of the second toe in children has almost no long-term morbidity. In our experience, parental acceptance of the procedure and the long-term outcome has been excellent.

( A–E ) Child with constriction ring syndrome with absence of all digits and thumb. Second toe transfer done in the position of the thumb. The transferred toe helps in grip and pinch.

Congenital pseudoarthrosis of the forearm is a rare condition occurring in 2 per 1 million children. Vascularized free fibula transfer has shown to yield 92% to 100% union rates compared to around 70% by nonvascularized bone grafts, so much so that vascularized bone graft has been recommended as the first choice of care and not after complications have set in.