In avulsion amputations of the arm, the biceps and brachialis muscles often avulse proximally and hang on the distal tendon. The muscle in such instances does not get revascularized after replantation and likely is removed with the debridement. In other cases, the musculocutaneous nerve may be avulsed. In either case, elbow flexion needs to be restored. In contrast, the triceps muscle rarely needs reconstruction, because proximal innervation of the triceps typically allows preservation of function following repair. In the very rare instance that both biceps and triceps are lost, preference is given to the reconstruction of the flexors of the elbow.

The most common procedure performed for elbow function is the transfer of the latissimus dorsi or the pectoralis major muscles. Both transfers can result in a good outcome. These muscles have also been transferred at the time of replantation both to restore flexion and to provide soft tissue cover for the blood vessels and nerves [11]. In upper third arm replantations or when vein grafts for vessel reconstruction have been used near the axilla, routing of the latissimus dorsi muscle may be difficult. In these cases, a pectoralis major muscle transfer is a reasonable option. It has the advantage of obviating the need for position change for flap harvest, albeit the expense of an unsightly scar in front of the chest. In lower arm replants, we prefer the latissimus dorsi transfer, which seems to generate more powerful flexion of the elbow than the pectoralis major. The line of the brachial artery is marked with the Doppler before marking the skin incision, and the vessels are protected while insetting the flaps. Bipolar technique of transfer of these muscles yields better results, by allowing for a direct line of pull [12]. The detached insertion of the latissimus dorsi or the pectoralis major is attached to the coracoid process and the other end is woven into the biceps tendon. A few centimeters of rectus sheath is harvested along with the pectoralis muscle to provide a more secure attachment to the biceps tendon. If the humerus has been shortened considerably during replantation, there may be a slack in the muscle. The upper attachment of the muscle in such circumstances is moved more proximally onto the clavicle. Establishing correct tension of the muscle while insetting the transfer is important. To accomplish this, we focus on reestablishing resting tension that was present prior to muscle harvest. After dissecting the entire muscle and before detaching the origin and insertion, marks are placed at 4 cm apart on the muscle with the arm abducted to 90°. The distance between the marks must be measured with the shoulder fully adducted and abducted. During transfer, the tension is adjusted such that the distance between marks during flexion and extension of the elbow nearly matches that observed during shoulder adduction/abduction prior to harvest. Elbow is immobilised in 100° flexion for 4 weeks, and then a detachable splint is used to maintain the position for a further period of 4 weeks when gradual loading and strengthening exercises are started.

Proximal third forearm-level replantations need more secondary surgery than distal forearm replants or lower third arm-level replants [13]. In traction or crush amputations, there may be segmental loss of muscle secondary to either injury or debridement. If the loss involves the motor nerves to the muscles or the neuromuscular junction, then all function is lost. Chuang et al. retrospectively studied 27 patients who had replantation after crush or traction avulsion amputation and recommended immediate free tissue transfer for soft tissue coverage and delayed free functional muscle transfer for the patients whose injuries resulted in denervation. Delayed free functional muscle transfer is performed after the patient’s condition has stabilized, and the limb is no longer swollen, which can be as early as 3–6 months after replantation. In two-stage reconstruction of both flexor and extensor motor units, the extensor reconstruction should precede the flexor reconstruction by 4–6 months [13].

Sabapathy and Elliot have classified the long flexor loss in complex injuries into three zones for the purpose of reconstruction (Fig. 14.4) [14]. Direct reconstruction of flexor loss in zone A may not be possible and free functioning muscle transfers are recommended. The procedure is usually performed 3 months after replantation. The gracilis musculocutaneous flap is our preferred free flap. The skin island not only serves for flap monitoring in the immediate postoperative period but also allows for a tension-free skin closure. Most replantations at this level are not able to accommodate the volume of the free muscle flap, and the skin island obviates the need for skin graft and permits easy skin closure.

The free flap can receive its blood and nerve supply from the forearm or the arm, depending on the extent of the injury. The anterior interosseous nerve or the motor branches from the median nerve to the flexor muscles have been recommended as the donor nerve, with the radial or ulnar artery supplying the blood flow. In our experience, we have found it difficult to identify a good motor nerve in the scarred forearm, particularly after proximal third replants. We often anastomose the free flap end to side to the brachial artery and isolate a suitable fascicle of the median nerve at the level of the elbow and use it to innervate the free muscle transfer. The principle of this is akin to the ulnar nerve to biceps transfer procedure advocated by Oberlin to obtain elbow flexion in upper trunk brachial plexus palsy [15]. Proximally, the muscle is attached to the lower end of the humerus and distally to the flexor digitorum profundus (FDP) tendons proximal to the carpal tunnel. Ideally, a separate free muscle transfer should be used to restore thumb flexion. We have not been satisfied with the functional outcome when using the same muscle to power the flexors of both the fingers and the thumb. In spite of obtaining good range of movement of the fingers and the thumb, adjusting tension to synchronize the movement of the thumb and the fingers for pinch is difficult. Because a separate free muscle transfer for thumb flexion may be impractical or impossible, we prefer using a free functional muscle transfer to restore finger flexion coupled with selective arthrodesis of thumb joints in a functional position.

In our series, 70 % of forearm replant patients have good intrinsic recovery. This is attributed to the shortening of the bones during the primary procedure that allows for a proper and tension-free nerve repair and a shorter distance for the axons to travel to their final destination. In lower third forearm- and wrist-level replants (zone B), direct tendon repair is possible resulting in substantially better functional results. Tenolysis may be required at this level secondarily.

In transmetacarpal-level amputations, after the repair of the flexor tendons, it can be sometimes impossible to repair the extensor tendons. While many patients will be functionally competent without extensors [16], we prefer to reconstruct the extensor tendons when possible. In such instances, extensor reconstruction is carried out secondarily. Tendon grafts are frequently required, and fascia lata is a good source for tendon grafts. Tension in the grafts during extensor reconstruction must be adjusted in such a way that flexion is not compromised. The authors maintain the interphalangeal joints in flexion, with both the metacarpophalangeal joints and the wrist in neutral position while suturing in the tendon grafts. In this way, the flexion of the fingers will not be compromised. In crush amputations, the skin on the dorsum of the hand may not be adequate and a flap for soft tissue coverage may be needed prior to tendon reconstruction.