MEDIAN NERVE PALSY AND TENDON TRANSFERDR.N. BENTHUNGO TUNGOEPG. M.S(ORTHOPEDICS)CENTRAL INSTITUTE OF ORTHOPEDICSNEW DELHI

Median nerve introduction The median nerve is derived from both the lateral and medial cords

of the brachial plexus, with the lateral cord providing mostly sensory axons from C6 and C7, and the medial cord providing motor axons from C8 and T1.

Also called labourer’s nerve.

Motor Functions The median nerve innervates the majority of the muscles in the anterior

forearm, and some intrinsic hand muscles. The Anterior Forearm

In the forearm, the median nerve directly innervates muscles in the superficial and intermediate layers:

Superficial layer: Pronator teres, flexor carpi radialis and palmaris longus. Intermediate layer: Flexor digitorm superficialis. The median nerve also gives rise to the anterior interosseous nerve, which

supplies the deep flexors: Deep layer: Flexor pollicis longus, pronator quadratus, and the lateral half

of the flexor digitorum profundus (the medial half of the muscle is innervated by the ulnar nerve).

In general these muscles perform pronation of the forearm, flexion of the wrist and flexion of the digits of the hand.

Cont:HAND: The median nerve innervates some of the muscles in the hand via two branches. The recurrent branch of the median nerve innervates the thenar

muscles – muscles associated with movements of the thumb. The palmar digital branch innervates the lateral twolumbricals –

these muscles perform flexion at the metacarpophalangeal joints of the index and middle fingers

Innervation

•Motor• superficial volar forearm group

•  Pronator teres•  Flexor carpi radialis•  Palmaris longus

• intermediate group•  Flexor digitorum superficialis

• deep group•  Flexor digitorum profundus (lateral)•  Flexor pollicis longus•  Pronator quadratus

• hand•  1st and 2nd lumbricals•  Opponens pollicis•  Abductor pollicis brevis•  Flexor pollicis brevis

Sensory innervation: The median nerve is responsible for the cutaneous

innervation of part of the hand. This is achieved via two branches:

Palmar cutaneous branch – Arises in the forearm and travels into the hand. It innervates the lateral aspect of the palm. This nerve does not pass through the carpal tunnel, and is spared in carpal tunnel syndrome.

Palmar digital cutaneous branch – Arises in the hand. Innervates the palmar surface and fingertips of the lateral three and half digits.

Course of median nerve Anterior compartment of arm

anterior compartment (anteromedial to humerus) runs with brachial artery (lateral in upper arm / medial at elbow) no branches in the arm

Forearm enters the forearm between the pronator teres and biceps tendon travels between flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) then emerges between the FDS and flexor pollicis longus (FPL)

Hand the nerve then enters the hand via the carpal tunnel, along with the tendons of the FDS, FDP and FPL

Terminal branches anterior interosseous branch (AIN)

innervates the deep volar compartment of forearm except the ulnar half of the FDP palmar cutaneous branch 

supplies sensory innervation to lateral palm recurrent branch (to thenar compartment) digital cutaneous branches

supply the radial 3 1/2 digits (palmar) can also supply the index, long, and ring fingers dorsally

Clinical findings:1. Injury at the Elbow:  Supracondylar fracture of the humerus.

Motor functions: The flexors and pronators in the forearm are paralysed, with the exception of the flexor carpi ulnaris and medial half of flexor digitorum profundus. The forearm constantly supinated, and flexion is weak (often accompanied by adduction, because of the pull of the flexor carpi ulnaris). Flexion at the thumb is also prevented, as both the longus and brevis muscles are paralysed.

The lateral two lumbrical muscles are paralysed, and the patient will not be able to flex at the MCP joints or extend at IP joints of the index and middle fingers.

Sensory functions: Lack of sensation over the areas that the median nerve innervates. Characteristic signs: The thenar eminence is wasted, due to atrophy of the thenar

muscles. If patient tries to make a fist, only the little and ring fingers can flex completely. This results in a characteristic shape of the hand, known as hand of benediction.

2. Injury at the Wrist: How it commonly occurs: Lacerations just proximal to the flexor reticaculum. Motor functions: Thenar muscles paralysed, as are the lateral two lumbricals. This

affects opposition of the thumb and flexion of the index and middle fingers. Sensory functions: Same as an injury at the elbow.

Median nerve clinical assessment:1. Pronator teres (C6, C7) assessment: The patient’s forearm is extended and fully pronated. The patient is then instructed to resist supination of the forearm by the examiner.

2. Flexor carpi radialis (C6, C7) assessment: The patient flexes the wrist along the trajectory of the forearm.

3. Flexor digitorum superficialis (C8, T1) assessment: To test proximal interphalangeal joint flexion, the supinated forearm and hand are placed straight. Each finger is tested separately. Placing your fingers between the single finger to be tested and the remaining fingers that are immobilized isolates this movement. This maneuver places the finger to be testedin mild flexion at the metacarpal–phalangeal (knuckle) joint, and stabilizes the remaining fingers in extension, a position that allows isolation of the flexor digitorum superficialis.

The flexor digitorum superficialis (also known as the sublimis muscle, C8, T1) is also innervated by the median nerve and mediates flexion of the second to fifth digits (all except the thumb) at their proximal interphalangeal joints.

4. Flexor digitorum profundus (C8, T1) assessment: To assess the median innervation of the flexor digitorum profundus one should concentrate on the index finger. To do so, hold the metacarpal-phalangeal and proximal interphalangeal joints immobile, and have the patient flex the distal phalanx against your resistance.

Ochsner’s clasping test: flexor digitorum superficialis and profundus( lateral half)

The Thenar Group5. Flexor pollicis longus (C8, T1) assessment: Immobilize the thumb, except the interphalangeal joint, and then ask the patient to flex the distal phalanx against resistance.

6. Okay” or “circle” sign with anterior interosseous nerve weakness. A quick way to assess the flexor digitorum

profundus and flexor pollicis longus innervation from the anterior interosseous nerve is to ask the patient to make an okay sign by touching the tips of the thumb and index finger together.

With weakness in these muscles, the distal phalanges cannot flex, and instead of the fingertips touching, the volar surfaces of each distal phalanx make contact.

7.Pronator quadratus (C7, C8) assessment

: Have the patient resist supination of a fully flexed and pronated forearm. With full forearm flexion, pronation by the usually dominant pronator teres is minimized.

8. Abductor pollicis brevis (C8, T1) assessment: Resist movement of the thumbaway from the plane of the palm (palmar abduction), while stabilizing the metacarpals of theremaining fingers.

9. Flexor pollicis brevis (C8, T1) assessment The patient flexes the thumb at the

metacarpal-phalangeal joint against resistance placed over both the proximal and distal phalanges.

Make certain the distal interphalangeal joint does not flex because in allowing this, substitution by the flexor pollicis longus occurs.

Use your other hand to immobilize the first metacarpal to reduce substitution by the opponens pollicis.

Because of its dual innervation, even with complete thenar motor branch palsies some thumb flexion still occurs.

10: Opponens pollicis (C8, T1) assessment:

Have the patient forcibly maintain contact between the volar pads of the distal thumb and fifth digit, while you try to pull the distal first metacarpal away from the fifth digit. Although thumb opposition is only innervated by the median nerve, a combination of thumb adduction (adductor pollicis, ulnar nerve) and thumb flexion (flexor pollicis brevis, deep head, ulnar nerve) may mimic thumb opposition even when there is complete median nerve palsy present.

11. Lumbrical of second digit (C8, T1) assessment:

Stabilize the patient’s index finger in a hyper-extended position at the metacarpal-phalangeal joint and then provide resistance as the patient extends the finger at the proximal interphalangeal joint.

Tendon transfer in median nerve injuries Median nerve palsy is perhaps the most devastating single nerve injury of the upper extremity. Not only is there a loss of fine motor control and opposition, but sensibility is lost over the area of the hand used for precision movements and prehensile functioning.

Tendon transfer procedures to restore movement may be ineffective if sensibility cannot be restored. High median nerve palsy is defined as an injury proximal to the innervation of the forearm muscles.

Although PT and FCR functions are lost, forearm pronation and wrist flexion are compensated for by other muscles, and do not need to be restored.

Although the FDS to all four fingers is lost, flexion is maintained in the ring and small fingers by the functioning ulnar-innervated FDP muscle bellies. However, even though ring and small finger flexion is preserved, grip strength is diminished.

More importantly, there is a loss of thumb IPJ flexion and index and middle finger DIPJ flexion due to loss of the AIN innervated muscles. This results in a lack of fine motor control of the hand, which is normally provided by precise movements of the IPJ of the thumb and the IPJ’s of the index and middle fingers.

In addition to these deficits, crucial thumb opposition is lost. Low median nerve palsy, on the other hand, results in loss of thumb opposition and sensory loss only.

The fact that some degree of sensory reinnervation is likely when a low median nerve injury has been repaired makes this a potentially less devastating injury than high median nerve palsy.

1. Restoring thumb opposition: The most devastating loss of movement following high or low median

nerve injury is the loss of thumb opposition. This can be restored with an opponensplasty, or opposition transfer.

Thumb opposition is a complex movement that involves palmar abduction, pronation, and flexion of the thumb metacarpal and proximal phalanx.

The ideal insertion for an opposition transfer is the APB insertion. Insertion at this point most reliably causes the combination of movements that result in thumb opposition.

The angle of pull should be from the location of the pisiform, because this approximates the normal direction of pull of the APB.

A pulley is often necessary to create the proper line of pull. The transverse carpal ligament, the palmar fascia edge, a loop of the FCU tendon, and the FCU tendon itself have all been used as pulleys

The superficialis opponensplasty described by Royle in 1938, involves dividing the ring inger FDS distally in the finger, retrieving

the FDS proximal to the carpal tunnel, re-directing the tendon distally through the FPL sheath, and inserting it into the thumb.

This transfer was later modified by Thompson by re-directing the tendon subcutaneously to the thumb, instead of through the FPL tendon sheath.

Bunnell recommended rerouting the tendon around a looped strip of FCU to achieve a more effective line of pull.

The main disadvantage of the superficialis opponensplasty is that it can only be used in cases of low median nerve palsy, because the FDS is paralyzed in high median nerve palsy

Superficialis opponensplasty using ring finger FDS for restoration of opposition in low median nerve palsy.

The EIP(extensor indicis propius)opponensplasty: in cases of both low and high median nerve injury, and is the most

commonly employed opposition transfer in high median nerve palsy Although the EIP is a weak motor, it is sufficiently strong to move

the thumb into opposition. The EIP is tunneled around the ulnar aspect of the wrist, routed

across the palm from the level of the pisiform, and inserted on the APB.

It is important to close the extensor hood of the index MCPJ after EIP harvest to prevent postoperative extension lag at the index MCPJ.

Functional loss with the EIP transfer is minimal, and retraining the EIP to perform thumb opposition is not difficult.

EIP opponensplasty for restoration of opposition in high median nerve palsy.

Camitz procedure: Although the use of the palmaris longus (PL) for restoring thumb opposition was

first described by Bunnell, it was popularized by Camitz. Although the PL transfer effectively restores palmar abduction, the pronation and

flexion components of opposition are not re-established. The primary indication for performing a Camitz transfer is to augment palmar

abduction in patients who have motor loss from severe carpal tunnel syndrome.

The Huber transfer: employs the ulnar nerve-innervated abductor digiti minimi (ADM) to

restore opposition. This transfer is usually used in cases of congenital absence of the

thenar muscles, and in cases where the FDS and EIP are not available. The ADM is released from its insertion, turned over 180 degrees, and

inserted on the APB insertion. Strength and excursion are well matched to the deficit, and the

transfer is synergistic

HUBER PROCEDURE:

Restoring Thumb IPJ flexion and index finger DIPJ flexion In cases of high median nerve injury, thumb IPJ flexion and index

finger DIPJ flexion can be restored with transfer of the BR, the ECRL, or ECU.

The most common transfers are BR to FPL and ECRL to index FDP. However, it should be remembered that reinnervation of the FPL and FDP is common after a high median nerve injury has been repaired.

If a return of function is anticipated, an end-to-side transfer should be performed.

If recovery is not expected, an end-to-end transfer results in a more direct line of pull.

Rehabilitation: First 4 weeks:

splint that should take tension off the tendon transfer(s) performed. For example, if a transfer was performed to improve clawing, the splint should keep the MCPJ’s flexed and the IPJ’s extended.

maintain mobility in the non-immobilized joints of the upper extremity. After 4 weeks:

Mobilization should start with gentle active and assisted range of motion exercises. It is important to mobilize one joint at a time to prevent placing too much tension on the transfer. For example, if an ECRB transfer to treat clawing was performed, the therapist should mobilize the MCPJ’s while keeping the wrist and IPJ’s immobile.

6 weeks: exercises that activate the muscles used in the tendon transfer, and should begin muscle retraining. Electrical stimulation and biofeedback may be used to assist with retraining.

8 weeks: At eight weeks postoperatively, strengthening exercises should be initiated, and the splint can be weaned off over the next four weeks.

Full activity is resumed at twelve weeks.

COMPLICATIONS: Tendon adhesions, transfer rupture, Transfer weakness Infection Neuro vascular injuries