PRINCIPLES OF TENDON TRANSFER

DR. DIBYENDUNARAYAN BID [PT]DR. DIBYENDUNARAYAN BID [PT]

GENERAL PRINCIPLES OF TENDON TRANSFERS

Three important principles should be emphasized :

• First, the transfer should not significantly decrease the remaining function of the hand.

• Second, the transfer should not create a deformity if significant return of function occurs following a nerve repair.

• Third, the transfer should be phasic or capable of phase conservation.

Fundamental principles of muscle-tendon units include the following:

• Correction of contracture

– In any patient with peripheral nerve palsy, all joints must be kept supple because soft tissue contracture is far easier to prevent than to correct.

– Maximum passive motion of all joints must be present before a tendon transfer because no tendon transfer can move a stiff joint.

• Adequate strength

– The tendon chosen as a donor for transfer must be strong enough to perform its new function in its altered position. Selecting an appropriate motor is important because a muscle will lose one grade of strength following transfer.

– Do not transfer muscle that has been reinnervated or muscle that was paralyzed and has returned to function.

• Amplitude of motion – Consider the amplitude of tendon excursion for

each muscle. A wrist flexor with an excursion of 33 mm cannot substitute fully for a finger extensor with an amplitude of 50 mm.

– Although the true amplitude of a tendon cannot be increased, its effective amplitude can be augmented 2 ways.

• First, the natural tenodesis effect can be used by converting a muscle from monoarticular to biarticular or multiarticular.

• Second, extensively dissecting a muscle from its surrounding fascial attachments can increase amplitude.

• Straight line of pull

– In the most effective transfer, the muscle passes in a direct line from its origin to the insertion of the tendon being substituted.

– Although not always possible, this configuration is desirable.

• One tendon, one function

– A single tendon cannot be expected to simultaneously perform diametrically opposing actions, eg, flex and extend the same joint.

– If a muscle is inserted into 2 tendons with separate functions, the force of amplitude of the donor tendon is dissipated and less effective than that of a muscle motored by a single tendon.

• Synergism – The use of synergistic muscles, eg, finger

flexors acting in concert with wrist extensors and finger extensors with wrist flexors, has been advocated for transfer.

– Muscle function is easier to retain after synergistic muscle transfer.

• Expendable donor

– The removal of a tendon for transfer must not result in an unacceptable loss of function.

– Sufficient muscle must remain to substitute for the donor muscle.

• Timing of tendon transfer – No transfer should be performed until the local

tissues are in optimal condition. – The term often used to describe this is tissue

equilibrium. – Tissue is in equilibrium when soft tissue induration

has resolved, when any reaction in the wound is absent, when joints are supple, and when the scars are as soft as they are likely to become.

– Tendon transfers function best when passed between subcutaneous fat and the deep fascial layer; they are not likely to be functional if placed in the pathway of a scar.

RADIAL NERVE PALSY

Although an infinite number of possible combinations for transfer of the radial nerve are available, currently, 3 sets of transfers are considered most reasonable.

Standard flexor carpi ulnaris transfer

• In standard flexor carpi ulnaris (FCU) tendon transfer (see Image 1), the first incision (incision 1) is directed longitudinally over the FCU in the distal half of the forearm. Its distal end is J-shaped with a transverse extension long enough to reach the palmaris longus (PL) tendon. The FCU tendon is transected from the pisiform and detached as far proximally as the incision allows.

• The second incision (incision 2) begins 2 inches below the medial epicondyle and angles across the dorsum of the proximal forearm, moving directly toward the Lister tubercle. The remainder of the fascial attachments to the muscle are incised.

• The third incision (incision 3) begins on the volar-radial aspect of the mid forearm, passes dorsally around the radial border of the forearm in the region of insertion of the pronator teres (PT) muscle, and angles back on the dorsum of the distal forearm towards the Lister tubercle.

• The PT muscle and tendon are passed subcutaneously around the radial border of the forearm, to be inserted into the extensor carpi radialis brevis muscle just distal to its musculotendinous junction.

• The FCU muscle is pulled into the dorsal wound. The line of pull must be as straight as possible from the medial epicondyle to the extensor digitorum communis tendon just proximal to the dorsal retinaculum (see Image 2).

• The extensor pollicis longus (EPL) muscle is divided and rerouted toward the volar aspect. The PL tendon is transected at the wrist and detached proximally to allow a straight line of pull between the PL and EPL tendons (see Image 3).

• The PT tendon is then sutured to the extensor carpi radialis brevis tendon. The FCU transfer is then sutured. The PL muscle is rerouted to the EPL tendon.

• Picture 1. Incisions used in the standard (flexor carpi ulnaris) combination of transfers.

• Picture 2. Pronator teres (PT) to extensor carpi radialis brevis (ECRB) transfer. Also pictured are the extensor carpi radialis longus (ECRL) and brachioradialis (BR).

• Picture 3. Palmaris longus (PL) to rerouted extensor pollicis longus (EPL) transfer.

Superficialis transfer

• To perform a transfer of the flexor digitorum superficialis (FDS), a long incision is made on the volar side of the radial aspect of the mid forearm, and the tendons of the PT, extensor carpi radialis longus, and extensor carpi radialis brevis are exposed.

• The PT tendon is sutured to the extensor carpi radialis brevis tendon. The FDS (also called sublimis) tendons of the long (FDS 3) and ring (FDS 4) fingers are exposed, divided, and delivered into the forearm wound.

• Then, 1- to 2-cm openings are made in the interosseous membrane, and the flexor tendons are passed to the dorsum through the openings in the interosseous membrane.

• The FDS 3 is rerouted to the radial side of the profundus mass, and the FDS 4 is rerouted to the ulnar side of the profundus mass.

• Kinking of the median nerve must be carefully avoided as the muscles are passed into the opening. The FDS 4 is interwoven into the tendons of the extensor indicis proprius and the EPL, and the FDS 3 is interwoven into the extensor digitorum communis tendon.

• Then, the flexor carpi radialis tendon at the base of the thumb is divided and detached. The flexor carpi radialis is passed through the substance of the abductor pollicis longus and extensor pollicis brevis tendons and sutured in place.

Flexor carpi radialis transfer

• First, the PT to the extensor carpi radialis brevis transfer is performed. The flexor carpi radialis tendon is exposed through a longitudinal incision on the volar-radial aspect of the forearm.

• The tendon is divided at the wrist and redirected around the radial border of the forearm to the wrist dorsally via a subcutaneous tunnel.

• The finger extensor tendons are tested for extension of the metacarpophalangeal (MP) joint and then divided. They are then withdrawn distally and sutured to the flexor carpi radialis. After that, reroute the PL to the EPL (see Image 4).

• Picture 4. Flexor carpi radialis (FCR) to extensor digitorum communis (EDC) transfer. Also pictured are the extensor pollicis longus (EPL), extensor carpi radialis brevis (ECRB), and pronator teres (PT).

ULNAR NERVE PALSY

• Ulnar nerve palsy results in an awkward hand with significant sensory loss and profound weakness. Signs and symptoms of ulnar nerve palsy include motor loss and sensory loss.

• Motor loss – Loss of flexion of the proximal phalanges of the fingers occurs due

to paralysis of the interossei and other intrinsic muscles. – Loss of integration of MP and interphalangeal joint flexion occurs

due to paralysis of the lumbrical muscles to the little and ring fingers.

– Loss of lateral or key pinch of the thumb occurs due to paralysis of the adductor pollicis.

– Flattened metacarpal arch (palmar arch) and loss of hypothenar elevation occur due to paralysis of the opponens digiti quinti and the decreased range of flexion of the little finger MP joint.

– Loss of extrinsic power to the ulnar-innervated portion of the flexor digitorum profundus is present with an inability to flex the distal phalanges of the ring and little fingers.

– Partial loss of wrist flexion occurs due to paralysis of the FCU. – Precision grip is impaired. – Loss of distal stability and rotation for a tip pinch between the

thumb and the index finger occurs due to paralysis of the first and second palmar interossei and the adductor pollicis.

• Sensory loss – Sensibility function is lost in ulnar nerve palsy

over the volar side of the little finger and the ulnar aspect of the volar side of the ring finger.

– In high ulnar nerve palsy, sensibility loss occurs over the dorsoulnar aspect of the palm and the dorsal side of the little finger.

Low ulnar nerve palsy • An isolated tendon transfer cannot restore all of the power

requirements lost in a low ulnar nerve palsy. A single FDS tendon transfer can improve integration of the MP joint and interphalangeal joint flexion, key pinch of the thumb, and the flattened metacarpal arch.

• In this procedure, the superficialis tendon of the ring finger is exposed. The radial slip of insertion is released proximal to the proximal interphalangeal joint and tenodesed to prevent hyperextension of the joint after the transfer is completed. The ulnar slip is released at its terminal insertion and split into 2 slips.

• These 2 slips are directed volarly to the deep transverse metacarpal ligament and then dorsally to be sutured at the insertion of the central slip of the dorsal apparatus on the middle phalanx of the ring and little fingers.

• Traction on the transferred slips should flex the MP joint and extend the proximal interphalangeal joint.

• When increased power of grip is desirable, a different insertion is preferred. In this circumstance, the superficialis slips are passed distally through the flexor sheaths and around the distal edge of the second annular pulley and sutured into place. With this insertion, the tendon does not extend the proximal interphalangeal joint, and the result is similar to dynamic transfers for proximal phalanx flexion.

• Pass the radial half of the tendon volar to the adductor pollicis muscle and dorsal to the flexor digitorum profundus tendons into the insertion of the abductor pollicis brevis (APB).

• Traction on the transferred tendon should adduct and pronate the first metacarpal. The MP joints of the claw fingers are placed in 45° flexion, and the proximal interphalangeal joints are placed in 0° extension. The first metacarpal is adducted so that it is parallel to the plane of the second metacarpal. This position is maintained in plaster immobilization for 4 weeks.

• Distal stability for tip pinch between the thumb and the index finger is improved by arthrodesis of the MP joint, and this procedure is indicated when the patient develops the Jeanne sign following transfer of the FDS (see Image 5).

• The transfer of a single FDS tendon and arthrodesis of the thumb MP joint improves 4 of the 6 lost motor functions in a person with low distal ulnar nerve palsy.

• Picture 5. Flexor digitorum superficialis (FDS) transfer used as an "internal splint" for low ulnar nerve palsy. Also pictured are the flexor digitorum profundi (FDP), the adductor pollicis, and the abductor pollicis brevis (APB).

Methods for managing other motor losses associated with ulnar nerve palsy include the following:

• Capsulodesis of the MP joint to control claw deformity:

In capsulodesis of the MP joint, a transverse incision is made in the distal palmar crease, and a triangle is cut into the deep transverse metacarpal ligament on each side of the volar plate flap (see Image 6). The volar plate flap is then advanced, inserted into the metacarpal neck, and immobilized for 6 weeks.

• Picture 6. Capsulodesis of the metacarpophalangeal (MP) joint to control claw deformity.

Dorsal tenodesis to control claw deformity: To perform dorsal tenodesis, the extensor carpi

radialis longus and extensor carpi ulnaris muscles are exposed. Each tendon is cut at the junction of the middle and distal thirds of the muscle. The freed half of the tendon is cut distally but left attached to its insertion on the metacarpal.

Each half tendon is then split once longitudinally to obtain 4 slips. Each slip is routed through the interosseous space and passed to the radial side of each finger. The slip passes volar to the deep transverse metacarpal ligament and inserts into the lateral band of the dorsal apparatus (see Image 7).

• Picture 7. Dorsal tenodesis to control claw deformity.

Transfer of FDS to control claw deformity: In FDS transfer for claw deformity, the

FDS tendon is divided into 4 slips and passed through the lumbrical canals and volar to the deep transverse metacarpal ligament.

Each slip may be inserted into the lateral band of the dorsal apparatus or into the second annular pulley of the flexor sheath (see Image 8).

• Picture 8. Transfer of a flexor digitorum superficialis (FDS) to control claw deformity.

Method to increase power grip: The best available method to increase

power for grip requires adding an extra muscle-tendon unit to the power train for flexion of the proximal phalanx.

Gross grip power is improved by transferring a wrist extensor or the brachioradialis to flex the MP joint.

Transfer to combine proximal phalanx power and integrate finger flexion:

After the extensor carpi radialis longus is passed around the radial side of the forearm, it is extended by a free graft in 2-4 slips.

It is then passed through the carpal tunnel and volar to the deep transverse metacarpal ligament and into the lateral band of the dorsal apparatus (see Image 9). This transfer adds power to finger flexion.

• Picture 9. Transfer of the extensor carpi radialis longus (ECRL) to control claw deformity.

Transfer to improve key pinch and flat metacarpal arch:

Transfer the brachioradialis, extended with a free tendon graft, through the interspace between the third and fourth metacarpals, to insert on the abductor tubercle of the thumb (see Image 10).

This transfer adds power to the key pinch.

• Picture 10. Transfer of flexor digitorum superficialis (FDS), through a facial pulley, to the abductor tubercle of the thumb.

Metacarpal arch restoration: The extensor digiti minimi tendon is step-cut at its

insertion, leaving a strip to be sutured to the extensor digitorum communis. The muscle-tendon unit is withdrawn to the wrist and passed through the forearm between the abductor pollicis longus and the flexor carpi radialis.

The extensor digiti minimi tendon is then passed subcutaneously in a diagonal course so that it can be sutured to the periosteum of the neck of the fifth metacarpal.

Method to improve tip pinch:

A slip of the abductor pollicis longus is elongated with a free tendon graft from the PL or plantaris and inserted into the tendon of the first dorsal interosseous (see Image 11).

• Picture 11. Tip pinch. A slip of the abductor pollicis longus (APL) is elongated with a free tendon graft from the palmaris longus (PL) or plantaris and inserted into the tendon of the first dorsal interosseous.

Tendon transfer for little finger abduction:

The ulnar half of the extensor digiti minimi is directed volar to the deep transverse metacarpal ligament and sutured to the phalangeal attachment of the radial collateral ligament of the MP joint of the little finger.

If the little finger is clawed and abducted, the tendon is inserted through the second annular pulley of the flexor sheath (see Image 12).

• Picture 12. Transfer of the ulnar half of the extensor digiti minimi (EDM) to correct persistent abduction of the little finger.

Side-to-side tenodesis for finger and wrist flexion:

Side-to-side tenodesis of the profundus tendons of the ring and little fingers to the profundus of the long finger in the forearm increases the power for gross grip (see Image 13).

• Picture 13. Finger and wrist flexion. Side-to-side tenodesis of the profundus tendons of the ring and the little fingers to the profundus of the long finger in the forearm increases the power for gross grip.

MEDIAN NERVE PALSY

• Median nerve palsy is caused by penetrating or perforating wounds of the forearm or wrist area. The motor deficit primarily involves loss of opposition of the thumb in injuries at the level of the wrist or distal forearm or, in more proximal injuries, loss of opposition of the thumb and severe weakness of the extrinsic flexors of the hand.

• Opposition is a composite of 2 motions. • The first is rotation of the thumb into pronation so that

the pulp fingers of the thumb and index fingers face one another.

• The second is abduction or lifting of the thumb away from the palm of the hand (palmar abduction).

• In the case of high median nerve palsy or low median nerve paralysis associated with tendon injury at the level of the wrist, a proprius tendon transfer is usually the first choice.

• However, in case of a low injury at the level of the wrist with a median nerve repair, often, no opponens transfer is indicated.

• These patients usually regain the function of the APB in 6 months and, in the case of sharp lacerations, have good return of function in one year.

Royle-Thompson opponensplasty • The most frequently used motor for opponensplasty of the

thumb is the FDS of the ring or middle finger. In the Royle technique, the motor is passed up the sheath of the flexor pollicis longus and the split superficialis tendon is attached to the superficial head of the flexor pollicis brevis and the opponens pollicis.

• The Thompson modification of this procedure uses a pulley and a more superficial location for this transfer. The distal end of the transverse carpal ligament and the ulnar border of the palmar fascia act as the pulley, and the route of the transferred digitorum superficialis is subcutaneous.

• A dual attachment is made. The first slip of the superficialis is attached through a hole drilled in the neck of the first metacarpal, while the other is drawn over the MP joint and sutured into the hood mechanism of the proximal phalanx.

Typical Bunnell opponensplasty • In a typical Bunnell opponensplasty, the superficialis

tendon of the ring finger is removed. Another incision is made proximal to the wrist over the ulnar artery and nerve area. The FCU tendon is identified. The FCU is exposed proximal to the pisiform and divided in half, with both halves remaining attached distally to the pisiform.

• A subcutaneous tunnel is created across the palm from the thumb to the pisiform area. The FDS of the ring finger is then delivered into the wrist incision and passed subcutaneously from the pisiform to the thumb incision.

• The distal tip of the FCU is then sutured to the pisiform to create a fixed loop through which the FDS can easily pass.

Methods of distal attachment

• Both the Bunnell and the Royle-Thompson opponensplasties use bony attachments (see Image 14). This can complicate the procedure of opposition transfer. If opposition transfer can duplicate the function of the APB, satisfactory function can result.

• Therefore, the transferred tendon is simply interwoven into the tendon of the APB. The Riordan attachment uses the interweaving of the transfer into the APB tendon, but continues it distally into the hood of the thumb MP joint and to the EPL tendon over the proximal phalanx.

• This larger attachment markedly increases the power of extension of the interphalangeal joint of the thumb. However, without a flexor pollicis longus, a hyperextension deformity can result.

• Picture 14. Techniques of distal attachment as described by Brand, Littler, Riordan, and Royle and Thompson.

• Brand's method of distal attachment interweaves one slip of the superficialis through the tendon of the APB and continues it on to the EPL.

However, the other slip comes across the extensor mechanism subcutaneously and is attached to the area of the adductor pollicis (see Image 14). This method creates considerable stability in the MP joint.

Proprius extensor tendon opponensplasties • Recently, proprius tendon transfers have become

popular. Both the extensor indicis proprius and the extensor digiti minimi have been described for restoration of opposition.

• A short incision is made over the MP joint of the index or the small finger. Another incision is made over the base of the fifth metacarpal. The extensor digiti minimi is brought into the more proximal incision, and a subcutaneous tunnel is created around the ulnar border of forearm across the palm to the area of the thumb MP joint. The pulley for this transfer is the ulnar aspect of the forearm.

• When the extensor indicis proprius is used, the tendon is removed along with a small portion of the tendon hood. The defect in the hood is repaired.

• A larger dorsal ulnar incision is made in the distal forearm. This incision allows the surgeon to displace the tendon into the forearm on its ulnar aspect.

• An additional incision is made in the area of the pisiform and the thumb MP joint. The tendon is then passed through the ulnar aspect of the wrist across to the MP joint. The attachment is made using Riordan's method, and, again, the pulley is the ulnar aspect of the forearm (see Image 15).

• Picture 15. Extensor indicis proprius (EIP) opponensplasty.

Extrinsic replacement in median nerve paralysis

• In high median nerve paralysis, a lack of function occurs in the forearm and wrist pronator-flexor group, with the exception of the FCU. Absent muscles include all of the FDS, the 2 radial profundi, and the flexor pollicis longus.

• When considering extrinsic replacement, the functions that need to be replaced must be determined.

• The flexor power in the long and index fingers, range of motion in the index finger, and range of motion and power in the interphalangeal joint of the thumb are desired.

• Only 2 or 3 muscle-tendon units are truly available for transfer. In high median nerve palsy, the brachioradialis and the extensor carpi radialis longus are available.

• An alternative to direct transfer for restoration of the extrinsic function is side-to-side suturing of the flexor digitorum profundi of the ring and small fingers, which are ulnarly innervated, to the denervated portions on the radial side.

• The use of suturing the extensor carpi radialis longus to the FDP of the index and long fingers is reserved for those patients who need radial side power and are unlikely to obtain significant reinnervation following neurorrhaphy (see Image 16).

• In order to perform a tendon transfer of new motors to the index finger or to the index and long fingers and thumb, the wrist must have a full range of motion.

• Similarly, the use of the brachioradialis to the flexor pollicis longus requires a full range of wrist motion.

• Picture 16. Extrinsic replacement using the brachioradialis to the flexor pollicis longus (A) and the extensor carpi radialis longus to the profundi of the index and long fingers (B).

• In both situations, the transfers as shown are end-to-end. If the patient has any chance of extrinsic return following grafting, the transfer should be end-to-side. The end-to-end technique shown here is used in patients with no chance of extrinsic return.

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