Hand Tendon Transfers Treatment & Management

Updated: Oct 31, 2018
  • Author: Steffen Baumeister, MD; Chief Editor: Joseph A Molnar, MD, PhD, FACS  more...
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Medical Therapy

Certain medical therapies may be effective for neurologic diseases and may lead to long-term recovery from the paralysis. In spinal cord injuries, activity-dependent therapies are thought to improve outcomes by improving the level of injury. In all cases, while awaiting stabilization of the injury or recovery of function, maintaining supple joints is necessary. Functional recovery or future reconstructive efforts will not be successful if joints are stiff.

Supple joints can be secured most easily by not letting them stiffen initially. Early on, patients should be referred to a hand therapist, with a specific request to maintain supple joints with active and passive motion programs. Obviously, most of the efforts involve passive methods and most require active patient participation with a home therapy program.

Alternatives to surgical reconstruction consist of modified tools, splints, or prostheses (see below).

Assist devices used in upper limb paralysis. Assist devices used in upper limb paralysis.

A study by Van Heest et al indicated that in children with upper extremity cerebral palsy, tendon transfer provides more functional improvement than does botulinum toxin injection or regular, ongoing therapy. The study involved 39 children with upper extremity cerebral palsy who underwent one of the three treatments, with the surgery group undergoing transfer of the flexor carpi ulnaris to the extensor carpi radialis brevis, along with release of the pronator teres and rerouting of the extensor pollicis longus with adductor pollicis release. At 12-month follow-up, the surgical patients showed greater improvement than the others as measured using the Shriners Hospital for Children Upper Extremity Evaluation dynamic positional analysis score, as well as the Canadian Occupational Performance Measure score for satisfaction and the Pediatric Quality of Life Inventory cerebral palsy module domain of movement score. [11]


Surgical Therapy

Non-nerve-related transfers

These include treatment for rheumatological conditions (eg, gout, pseudogout) and traumatic injury to muscles and tendons.

Tendon transfers for non–nerve-related loss of function tend to be some of the most simple and straightforward. The most frequently encountered of these is replacement of ruptured tendons as treatment for arthritic conditions. Rupture of extensor tendons of fingers or thumb is commonly associated with rheumatoid arthritis. (For more information, visit Medscape’s Rheumatoid Arthritis Resource Center.)

The extensor pollicis longus (EPL) tendon is at risk of rupture as a complication of distal radius fracture. Before planning early transfers for this category of injury, the surgeon should be sure that the loss of function is indeed from disruption of the tendon and not from an isolated nerve palsy such as an anterior or posterior interosseus nerve palsy. Loss of a tenodesis effect usually confirms that the problem resides with the tendon (see below).

Natural tenodesis is demonstrated by flexing and e Natural tenodesis is demonstrated by flexing and extending the wrist with the hand relaxed. The effect shows extension of the fingers when the wrist is flexed and flexion of the fingers when the wrist is extended. If the tendons are not intact, this effect is lost.

Replacement of the EPL function is usually performed with a transfer of the extensor indicis proprius (EIP) (see below). A tendon graft to replace extensor function may be an option and equal results of EIP transfer and intercalated free tendon graft have been demonstrated by Schaller et al. [12] However, if the rupture is of longstanding duration, a transfer is the most reasonable option.

Extensor indicis proprius transfer to the extensor Extensor indicis proprius transfer to the extensor pollicis longus.

While a tendon graft to replace extensor function may be an option if the rupture is not of longstanding duration, these patients often do not seek treatment until months after the rupture. Under these circumstances, a transfer is the most reasonable option.

The EIP has redundant function with the extensor digitorum communis (EDC) and, thus, is expendable. Before transfer of the EIP, especially in a patient with rheumatoid arthritis, the surgeon should be confident that the EDC has not been affected by the disease and is functioning normally.

For finger extensor tendons, a side-by-side transfer to an adjacent extensor tendon may provide adequate function and is simple to perform (see below). The authors' practice is to inspect the functioning tendons throughout their course in the dorsal compartments. This allows recognition and correction of any potential problem that may lead to further rupture of tendons. Correction of bony problems may require work on the carpus, distal ulna, or distal radius.

Tendons ruptured secondary to rheumatoid arthritis Tendons ruptured secondary to rheumatoid arthritis. Repair by transfer of long extensor digitorum communis (EDC) to the ring EDC and the index EDC to the little EDC. The fourth dorsal compartment has been opened to allow inspection of the compartment and repair of any problem causing the ruptures.

While extensor tendons tend to be more commonly involved with spontaneous ruptures, flexor tendons may also suffer a similar fate, although not as frequently. Tendon grafts are often the best solution when trying to reconstruct flexor function. When tendon grafts are impractical or impossible, transfers may be used. Spontaneous rupture of flexor tendons occurs most often in the palm or carpal canal. This precludes the use of wrist extensors for reconstruction unless the transfer is extended with a graft. Fortunately, surgeons can usually sacrifice a superficialis tendon to transfer to an adjacent profundus to restore flexion of the entire digit.

Median nerve paralysis

High median nerve lesions lead to loss of pronation, profundus function of the index finger, superficialis function to all fingers, flexor function of the thumb, and opposition. [13, 14] Profundus function to the ring finger may also be weak. Various muscles may be transferred to restore finger and thumb flexion (see Table 1). [15] The authors prefer the brachioradialis (BR) for thumb flexion.

Table 1. Recommended Transfers for a High Median Nerve Palsy (Open Table in a new window)




Flexor pollicis longus

Extensor carpi radialis longus

Flexor digitorum profundus

EIP opponensplasty

The extensor carpi radialis longus (ECRL) can be used to restore index and long profundus function. Specific restoration of superficialis function is not necessary. An EIP opponensplasty provides excellent and natural opposition (see below). If loss of pronation is a problem, the biceps tendon can be rerouted at its insertion to achieve modest improvement of function. Usually, this is not necessary.

Opponensplasty using the extensor indicis proprius Opponensplasty using the extensor indicis proprius for treatment of low median nerve palsy.

Anterior interosseous palsy leads to loss of thumb flexion, loss of index profundus function, and weakness in long finger profundus function. Opposition and pronation remain intact. An ECRL transfer to the profundus restores index profundus function, and a BR to flexor pollicis longus (FPL) transfer restores thumb flexion (see Table 2).

Table 2. Tendon Transfers for an Anterior Interosseous Nerve Palsy (Open Table in a new window)




Flexor pollicis longus

Extensor carpi radialis longus

Flexor digitorum profundus

In low median nerve lesions, the only motor loss is opposition. As in the high lesion, an EIP opponensplasty adequately restores the lost opposition. [16]

Ulnar nerve paralysis

High ulnar nerve lesions leave deficits in ulnar intrinsic function of the hand, flexor carpi ulnaris (FCU), and profundus function to the little and ring fingers. [13] If the flexor carpi radialis remains functional, the FCU does not need to be restored. Transfer of the BR to the flexor digitorum profundus (FDP) or a side-to-side profundus transfer (see Table 3) can restore profundus function. Loss of the ulnar-innervated intrinsic functions leads to clawing of the little and ring fingers, as shown below.

Ulnar clawing produced by loss of intrinsics to th Ulnar clawing produced by loss of intrinsics to the little and ring fingers, characterized by hyperextension of the metacarpophalangeal joints and flexion of the interphalangeal joints.

Table 3. Tendon Transfers for a High Ulnar Nerve Palsy (Open Table in a new window)




Flexor digitorum profundus

Flexor digitorum superficialis

Adductor pollicis

Flexor digitorum superficialis lasso ring and little

Blocking hyperextension of the metacarpophalangeal (MP) joints of the little and ring fingers can allow the extrinsic extensor to extend the interphalangeal (IP) joints of the little and ring fingers. The preferred transfer is a lasso procedure, which involves tying a slip of the superficialis tendon around the A-1 or A-2 pulley of the flexor tendon sheath, as shown below.

Zancolli-type lasso of A-1 pulley by the superfici Zancolli-type lasso of A-1 pulley by the superficialis.

In lower ulnar nerve lesions, restoration efforts are essentially the same as for high lesions except the profundus does not need attention.

In both high and low lesions, restoring an adductor of the thumb is occasionally necessary or desirable. This is accomplished with a superficialis transfer, usually from the long finger in high lesions and from the ring finger in low lesions, to the distal thumb metacarpal.

Radial nerve paralysis

High radial nerve lesions produce loss of finger, thumb, and wrist extension. [17] Supination may be weak but is usually adequately provided by the biceps function. [13] Of particular note in high lesions is the loss of BR and ECRL function. Loss of the BR eliminates an excellent donor, and loss of the ECRL imposes the need for wrist extension restoration.

Historically, various transfer combinations have been attempted. These may be chosen according to the experience and preference of the surgeon. [18] The authors prefer pronator teres (PT) to extensor carpi radialis brevis (ECRB) transfer for wrist extension, FCU to EDC transfer for finger extension, and a palmaris longus to a rerouted EPL transfer for thumb extension (see Table 4). If the palmaris is absent, then the ring superficialis can be used for the thumb extensor. However, other alternatives are available, and preferences vary from surgeon to surgeon. In 2006, Ropars et al recommended using the FCR instead of the FCU for restoration of finger extension. [19]

Table 4. Tendon Transfers for a High Radial Nerve Palsy (Open Table in a new window)



Pronator teres

Extensor carpi radialis brevis

Flexor carpi ulnaris

Extensor digitorum communis

Palmaris longus

Extensor pollicis longus (rerouted)

For lower lesions involving only the posterior interosseus nerve, ECRL function is usually adequate to provide wrist extension. If wrist extension is accompanied by severe radial deviation, side-to-side connection of the ECRL and ECRB may achieve a more centralized extension. Finger extension is again restored with FCU transfer to the EDC, and thumb extension can be restored with a BR transfer to the EPL (see Table 5). Some surgeons recommend the restoration of thumb abduction by a tenodesis of the abductor pollicis longus to the BR. [19]

Table 5. Tendon Transfers for a Low Radial Nerve Palsy or Posterior Interosseous Nerve Palsy (Open Table in a new window)




Extensor pollicis longus

Flexor carpi ulnaris

Extensor digitorum communis

Mixed peripheral nerve paralysis/brachial plexus paralysis/spinal cord paralysis

With mixed paralysis, such as may occur with multiple nerve involvement or more central lesions such as those involving the brachial plexus [20] or spinal cord, the authors believe drawing a table indicating which functions are present, which are absent, and which are in need of reconstruction is most convenient. The table also lists available muscles along with their function. A glance at the table, once filled out, shows which muscle may be transferred to provide the various functions needed (see Table 6).

Table 6. Muscles Available for Transfer (Open Table in a new window)






Muscles Available

Elbow flexion












Elbow extension




Forearm pronation



Pronator teres




Pronator quadratus

Forearm supination




Wrist flexion



Flexor carpi radialis




Flexor carpi ulnaris




Palmaris longus

Wrist extension



Extensor carpi radialis longus




Extensor carpi radialis brevis




Extensor carpi ulnaris

Finger flexion



Flexor digitorum profundus




Flexor digitorum superficialis

Finger extension



Extensor digitorum communis




Extensor indicis proprius




Abductor digiti minimi

Thumb flexion



Flexor pollicis longus

Thumb extension



Extensor pollicis longus

Thumb opposition



Abductor pollicis brevis

Thumb adduction



Abductor pollicis

Name and other procedures:

Remember that with more extensive loss of function, restoration of all desirable motions with active transfers may not be possible. Under circumstances that allow for minimal active function, the judicious use of tenodeses helps restore some useful function to the limb even though that function may be modest. A good example of this is found in the patient with only BR function below the elbow. In this case, restoration of flexion and extension of the thumb, finger, and wrist is desirable. However, with only one muscle available for transfer, active restoration of all of these functions is not possible.

A reasonable compromise consists of transferring the BR to the ECRB to provide active wrist extension. Then, perform tenodeses of the FPL, FDP, EPL, and EDC. These tenodeses augment a natural tenodesis with wrist extension and flexion. The BR provides active wrist extension, producing a pinching motion of the fingers and thumb. Release is provided by wrist flexion initiated by gravity. The entire reconstruction is performed in 2 procedures. The BR transfer and extensor tenodesis can be performed in one session, and the flexor tenodesis can be performed at another.

With fewer active motors available, those that are retained are called upon to produce more of a mass movement than the isolated individual digit movements that normally occur. For example, the transferred BR should extend the index, long, ring, and little fingers. While such a requirement is not ideal, the dearth of other choices may make it reasonable. In such cases, balancing the extrinsic tendon is necessary to provide optimum motion to each digit. This is performed via a side-to-side connection of the profundus or extensor tendons, as appropriate (see below). Tendons are positioned and connected to produce uniform motion in all digits from a single motor.

Side-by-side adjustments of the profundus or exten Side-by-side adjustments of the profundus or extensor tendons for extrinsic balance.

Also possible is performing one transfer to overpower a present but weak function. This is common with transfers to the FPL in the presence of weak or absent EPL function and paralysis of thumb intrinsics. This produces a hyperflexion of the IP joint of the thumb unless it is stabilized. The IP joint can be stabilized either by arthrodesis or a stabilizing transfer. The authors prefer a stabilizing transfer, in this case a split FPL-to-EPL transfer (see below).

Split flexor pollicis longus transfer for stabiliz Split flexor pollicis longus transfer for stabilization of the interphalangeal joint.

With significant paralysis, one can be tempted to perform a wrist arthrodesis to "free up" wrist flexors and/or extensors for transfer. While this procedure may occasionally be useful, experience has shown that if wrist motion can be preserved and made active, better function is obtained by letting the wrist motion augment active transfer with a tenodesis effect.

When considering transfer of the ECRL, ensure that the ECRB is of adequate strength to provide wrist extension. Clinically verifying that the ECRB is active or estimating its strength is difficult, even when one is sure that it is functioning. The best way to evaluate ECRB function is by performing a diagnostic procedure in the operating room.

Prior to providing a general or regional anesthetic but with the patient under local anesthesia, the ECRB is exposed distally and isolated from the ECRL. A suture is placed in the ECRB and attached to a strain gauge, weight, or elastic. The goal is to ensure the ECRB is capable of lifting 5 kg. The patient is requested to extend the wrist. If the ECRB is able to lift 5 kg, it is assumed to be adequate, allowing the ECRL to be used as a donor.

Reconstructions that require both flexor and extensor transfers must be staged. The first stage can be either flexor or extensor, although some experienced surgeons have recommended performing extensor transfer first because rehabilitation may be easier. However, the most dramatic improvement of function is from flexor transfer, leading some surgeons to start with flexors to maintain patient enthusiasm for the efforts.

A frequent problem in brachial plexus injury is loss of elbow flexion. This is often associated with severe paralysis of the entire upper extremity, resulting in few local donors. If the pectoralis major or latissimus is functioning, one of these may be transferred to the biceps distally to produce elbow flexion. In addition, forearm muscle function may remain intact with loss of proximal muscles. If the wrist and finger flexors remain strong, the patient may be a candidate for a Steindler flexorplasty. In this procedure, the flexor mass is detached at the medial epicondyle and moved proximally to attach to the distal humerus.

When desirable, elbow extension can be reconstructed with a posterior deltoid transfer to the triceps. This is a commonly required transfer in spinal cord injury.


Intraoperative Details

Once the appropriate transfers have been chosen, obtain surgical exposure to allow access to both the donor and recipient sites. Incisions tend to be longitudinal and centered to allow for appropriate exposure.

The donor should be harvested to maximize the length of the tendon, occasionally even extending the tendon with periosteum. The PT is often harvested with a strip of periosteum to allow it to reach its donor without requiring extension with a graft. One exception to this maximizing effort is when harvesting a flexor digitorum superficialis (FDS) tendon. A distal stump is left to help stabilize the proximal IP joint.

The donor muscle should also be completely freed from fascial attachments. This requires an extensive dissection about the muscle. Exercise care when performing this portion of the operation to avoid harming the muscle's nerve and vascular supply. Freeing fascial soft tissue attachments increases the overall excursion that can be obtained. Conversely, if the muscle is inadequately mobilized, poor excursion, thus poor function, is the result of the transfer.

It is vital for the transferred tendon to obtain the adequate tension during inset. [21] The 3 options are as follows:

  • The best method is a neuromuscular stimulator, which is useful to evaluate the excursion after dissection and, ultimately, the function of the transfer. The stimulator should provide a biphasic current of approximately 20 mA at 20 Hz with variable pulse width. Pulse widths of 100-200 milliseconds applied to the neuromuscular junction generally maximize the contraction of the muscle (see below). Active excursions of 5 cm or more are preferred.

    The neuromuscular stimulator is useful for intraop The neuromuscular stimulator is useful for intraoperative evaluation of tendon excursion and transfer function.
  • Most surgeons probably use the clinical assessment and the passive movements of the involved joints to judge the tension.

  • Measurements and markings of passive tension in the transferred muscle (eg, every 5 cm) can be used to find the correct tension after transfer. This method is commonly used in free muscle transfers.

Once the donor tendon is dissected, it is routed to the recipient. Routing is usually performed using the most direct route. When possible, routing the tendon around the forearm, rather than through the interosseus membrane, is better. Routing through the membrane often produces adhesions, minimizing active function. Otherwise, the most direct route should be taken. The authors prefer to use a Pulvertaft weave to connect a donor to a recipient (see below).

Pulvertaft weave used to connect tendon grafts. Pulvertaft weave used to connect tendon grafts.

A neuromuscular stimulator is useful in setting the tension of the transfer. Prior to completing the Pulvertaft weave, a preliminary attachment is made by attaching the donor to the recipient, with the donor in the midpoint of its total excursion and the recipient joint in neutral or the midpoint of its total functional arc. The donor is then maximally stimulated. This demonstrates the postoperative function that can be expected.

Final adjustments of tension are made based on the function observed during this stimulation, as shown below. When using a stimulator, the extremity should be warm and adequately perfused. Avoid too much tension because excessive tension on a muscle reduces its active function. Obviously, tension that is too loose will not produce the desired active motion.

Test excursion and transfer function using a neuro Test excursion and transfer function using a neuromuscular stimulator.

The choice of whether to perform an end-to-end or end-to-side connection should be based on the difference in expected function. If return of functional activity in the recipient is possible, choose an end-to-side connection.

The posterior deltoid does not reach the triceps tendon and is extended with a graft from the tibialis anterior or fascia lata. The authors prefer grafting by disinserting the central third of the triceps from the olecranon and reflecting it proximally to attach to the deltoid. The medial and lateral thirds of the triceps are reconstituted or repaired. The posterior deltoid is elevated with periosteum and split from the middle and anterior deltoid. Care is taken to avoid injury to the traversing nerve supply in the proximal third of the deltoid. The connection between the deltoid and triceps is reinforced with Dacron tape.


Postoperative Details

In general, joints are immobilized in the position of the function that is being reconstructed. Details of the immobilization, such as the degree and length of time, vary. Interestingly, studies are increasingly undertaken to compare early active motion regimens with passive motion regimens or cast immobilization. These studies show promising results. [22] Rath, for example, showed similar outcomes in a reduced recovery time by immediate active mobilization of opposition tendon transfer. [23]

Transfers for flexion

With flexor tendon transfers, the patient is placed in an immobilizing splint appropriate to protect tendon connections. This places the wrist in 20-30° of flexion and MP joints at 60-90° of flexion. IP joints can be allowed to extend. The patient is left in the initial dressing until the first postoperative visit.

Transfers for extension

With extensor tendon transfers, the patient is splinted with the wrist in 30° of extension and the MP joint extended. IP joints are allowed to flex. As with flexor transfers, the initial dressing is left in place until the first postoperative visit, which should be within 1 week.

For split FPL transfers to stabilize the IP joint of the thumb, the IP joint is splinted in extension. If not precluded by other concomitant transfers, splinting the wrist in 20° of flexion following this procedure also may be useful.

When performing a posterior deltoid transfer to the triceps, the elbow is splinted fully extended and the arm is abducted 30°. Abduction is usually maintained with an axillary wedge.

Elbow flexion reconstruction is splinted with the elbow flexed 90-100°.



Follow up with patients within 1 week. The patient is usually referred to a hand therapist at the first postoperative visit. The importance of a good, experienced hand therapist in the ultimate outcome of the procedure cannot be overemphasized.

Extensor transfers are generally managed by simple immobilization with the wrist and MP joints extended for approximately 4 weeks. After 4 weeks, the immobilization is discontinued and active and passive exercises are begun. At this point, the therapist initiates motor reeducation protocols. These include cognitive exercises, biofeedback, and task-oriented activity. Motor reeducation continues from 1-3 months.

The extensor indicis transfer to reconstruct the EPL presents a different scenario because it is performed using a Pulvertaft suturing technique, which is more stable than any other suture technique. An early dynamic motion protocol (reversed Washington regimen) can be applied for 3 weeks, with increasing active flexion (ie, 45°, then 60°, then unlimited flexion for the first, second, and third wk, respectively), which shortens the total rehabilitation time. [24]

Flexor transfer may be treated with a protocol of 4 weeks of immobilization (as with extensor transfers) or with an early motion protocol. Early motion usually consists of passive motion, with active motion efforts delayed until approximately 4 weeks postoperatively. During the fourth postoperative week, efforts at motor reeducation are started.

Posterior deltoid transfers present a special case. These patients are immobilized in extension and abduction for 4 weeks. After the fourth week, the patient is placed in an adjustable Bledsoe splint, and, at weekly intervals, flexion is increased by 15°.



Complications of tendon transfer surgery are typical of any surgery in the upper extremity. These include the relatively small potential for wound infections, blood loss or hematoma, injury to nerves, or injury to tendons. Because a tendon connection has been made, rupture of the tendon connection can occur. Most of the connections are performed with Pulvertaft weaves. Because these are quite strong, ruptured connections are infrequent. However, even a Pulvertaft weave can be pulled apart as a result of improper splinting or overactivity.

Of more concern is the possibility that the transfer does not function as desired because of too-loose or too-tight tension. The use of intraoperative stimulation to evaluate the transfer and tension helps to minimize disappointing postoperative results.

Function may also be reduced by strong tendon adhesions that reduce excursion. Appropriate aggressive therapy reduces the occurrence of clinically important adhesions, but some individuals may not be able to overcome strong adhesion formation. Use of anti-inflammatory drugs in the postoperative period may also reduce adhesion formation. Tenolysis after 3-6 months may be necessary to maximize function. After tenolysis, aggressive use of active and passive motion protocols is necessary.

Undesirable consequences of donor sacrifice are another concern. One example is loss of wrist extension after transfer of the ECRL. Careful planning and appropriate preoperative and intraoperative evaluation reduce unexpected donor consequences.

Despite appropriate planning, execution, and postoperative care, some patients are not able to develop satisfactory motor reeducation. These patients may continue to benefit from a tenodesis effect of the transfers, but they do not achieve its maximum benefit.


Outcome and Prognosis

Depending on the specifics of each transfer, such as the amount and quality of intact function, the choice of available donors, the suppleness of joints, and the presence of intact sensation, outcomes can vary tremendously. When function is lost from ruptured tendons or neuromuscular paralysis, tendon transfers generally provide enough improvement in function to warrant their recommendation (see images below).

Opponensplasty using the extensor indicis proprius Opponensplasty using the extensor indicis proprius for treatment of low median nerve palsy.
Flexor reconstruction in brachial plexus injury us Flexor reconstruction in brachial plexus injury using a brachioradialis to flexor digitorum profundus transfer and a pronator teres to flexor pollicis longus transfer along with extensor tenodesis for release.
Flexor reconstruction in a tetraplegic patient usi Flexor reconstruction in a tetraplegic patient using a extensor carpi radialis longus to flexor digitorum profundus transfer and a pronator teres to flexor pollicis longus transfer along with a split flexor pollicis longus transfer to stabilize the interphalangeal joint.

Continued strengthening and improved motor reeducation may result in functional gains and continued improvement for up to a year after the surgery. However, in most patients, function changes little after 6 months.

Outcomes are substantially influenced by postoperative therapy and by motivation and expectations. Without good therapy and patient motivation, good results are difficult to obtain.


Future and Controversies

Tendon transfers are very useful in restoring function but, at best, are a compromise. Loss of donor function always occurs, and the restored function is rarely as complete or as strong as natural function. Better nerve injury management in some cases may make transfers unnecessary. Better management of joints in the postinjury period may improve restored function, even when transfers must be relied upon.

In patients with spinal cord injuries or in patients with primary upper motor neuron paralysis, an implantable electronic neuroprosthesis restores some hand grasp and pinch function. [25] In tetraplegic patients, this system, which does not primarily rely on tendon transfers, has substantially improved patient quality of life and independence. In some tetraplegic patients in whom no donor is available, it may be the only hope of restoring upper extremity function. When first introduced, the system required insertion through large incisions, which could be changed to a percutaneous electrode placement technique. [26] While the neuroprosthesis in these patients becomes the primary motion system, tendon transfers may still be desirable to maximize function with and without the use of the prosthesis.

In high peripheral nerve lesions, the time necessary for nerve regeneration, even in a perfect nerve repair, may exceed the window of opportunity during which the target muscle is receptive to reinnervation. Current laboratory work suggests stem cells may be used as "baby sitters" during the time of nerve regeneration. In this scheme, motoneuron stem cells are placed in the distal peripheral nerve adjacent to the target muscle. The nerve injury can be repaired using current methods of nerve repair. The stem cells have been shown to innervate the target muscle. If these cells could be engineered by inserting an apoptosis gene to die on command, one could simply wait the appropriate amount of time for the regenerating nerve to reach the vicinity of the muscle, then eliminate the stem cell population. The regenerating nerve may even be able to form a synapse with the stem cell, thus not requiring its elimination. This scheme, used successfully, would eliminate some need for tendon transfer.

The same idea of prolonging the period a muscle remains receptive to reinnervation has prompted the use of direct current stimulation of muscle. Preliminary studies suggest that long-term stimulation of denervated muscle preserves its mass and receptiveness.

Free muscle transfers or island transfers may also be useful in restoring function in the upper extremity. For the last 2-3 decades, reports have described gracilis transfer to restore flexion or extension in the hand. The use of bipolar transfers, such as the latissimus, has also been reported to restore flexion or extension of fingers.