19: Tendon Transfers for Ulnar Nerve Palsy

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Procedure 19 Tendon Transfers for Ulnar Nerve Palsy

Sandeep J. Sebastin, Kevin C. Chung

See Video 15: Tendon Transfers for High Median and Ulnar Nerve Palsy

Indications

Delayed presentation (>1 year) of an ulnar nerve laceration

Failed motor recovery after repair/reconstruction of the ulnar nerve

Failed motor recovery after release of ulnar nerve compression at Guyon canal or cubital tunnel

Persistent motor weakness after completion of drug therapy in Hansen disease (leprosy)

Neurologic disorders (for example, Charcot-Marie-Tooth disease, syringomyelia)

Examination/Imaging

Clinical Examination

Functional deficit: The loss of function in ulnar nerve palsy results from the claw deformity, which causes an abnormal pattern of finger flexion, weak thumb key pinch, small finger abduction deformity, and loss of ring and small finger distal interphalangeal (DIP) joint flexion (Fig. 19-1). However, these problems may not be functionally disabling in all patients, and some may require correction of only one aspect. It is important to determine this and then to set a sequence for the appropriate corrective procedures. It is better to correct the lack of DIP joint flexion first, followed by transfers for restoring thumb key pinch, and finally correction of the claw deformity because it is difficult to establish appropriate intrinsic plus posture of the hand.

• Claw deformity (Duchenne sign): This is the characteristic resting posture of the ring and small fingers with hyperextension of the metacarpophalangeal (MCP) joints and flexion of the interphalangeal (IP) joint. It results from the unopposed action of the radial nerve–innervated long extensors at the MCP joint (hyperextension) and median nerve–innervated flexor digitorum superficialis at the proximal interphalangeal (PIP) joint (flexion) in the presence of paralyzed ulnar nerve–innervated interosseous muscles and the third and fourth lumbricals that normally flex the MCP joint and extend the PIP joint. The MCP joint hyperextension deformity may not appear immediately after an ulnar nerve injury and depends on the laxity of the MCP joint volar plate. The deformity is more pronounced in patients with a lax volar plate and develops over time in patients with a taut volar plate.

♦ In a high ulnar palsy, the deformity appears less severe because the flexor digitorum profundus to the ring and small fingers (innervated by the ulnar nerve) is paralyzed and the patient has no claw at the DIP joint (ulnar nerve paradox). Therefore, the increase in severity of a claw deformity after repair of a high ulnar nerve injury is a good prognostic sign and indicates reinnervation of the ring and small finger flexor digitorum profundus (FDP) (Fig. 19-2).

♦ A claw deformity results in an abnormal pattern of finger flexion because the IP joint flexes before the MCP joint. In a normal hand trying to grasp an object, the MCP joint flexes first (intrinsic action), followed by the long flexors (IP joint) to wrap the hand around the object. In ulnar nerve paralysis, the IP joint flexes before the MCP joint, which pushes the object out of the hand (Fig. 19-3).

♦ In an ulnar nerve palsy, the claw deformity usually involves only the ring and small fingers because the median nerve–innervated first and second lumbricals retain their function. In Hansen disease (leprosy) and lacerated wounds involving both nerves, the patient may have clawing of all four fingers.

• Weak thumb key pinch: This results from paralysis of the ulnar nerve–innervated adductor pollicis and first dorsal interosseous. In addition to the obvious muscle wasting in the first web space, a positive Froment sign demonstrates the muscle deficit. The patient is asked to pinch sheets of paper between the thumb and index finger of both hands. A positive Froment sign is indicated by marked thumb IP joint flexion in the affected hand as a result of the patient using the median nerve–innervated flexor pollicis longus to hold the sheet of paper, rather than using the adductor pollicis (Fig. 19-4).

• Small finger abduction deformity (Wartenberg sign): The small finger is abducted at rest, and putting the hand into a pocket can become difficult. This deformity results from unopposed action of the radial nerve–innervated extensor digitorum minimi (EDM) in the presence of the paralyzed ulnar nerve–innervated third palmar interosseous muscle that normally adducts the small finger. EDM causes abduction of the small finger in addition to extension because it has an insertion on the ulnar aspect of the base of the proximal phalanx (Fig. 19-5).

• Loss of small and ring finger DIP joint flexion (Pollock sign): This is seen in high ulnar nerve palsy with loss of innervation to the FDP of the ring and small fingers. The flexor digitorum superficialis (FDS) and the FDP of the index and long fingers are innervated by the median nerve (Fig. 19-6).

Sensation: It is important to document the level of sensation in the thumb and the fingers preoperatively. Loss of sensation on the dorsoulnar aspect of the hand, which is innervated by the dorsal branch of ulnar nerve, can help differentiate a high ulnar nerve lesion (e.g., cubital tunnel compression) from a low ulnar nerve lesion (e.g., Guyon canal compression), which should have preserved sensation over the dorsal-ulnar hand (Fig. 19-7).

Joints: To achieve a good result from the tendon transfer, patients must have good passive range of motion at the IP and the MCP joints. The most important aspect of assessment of an ulnar nerve palsy is determining whether the patient can extend the PIP joint with the examiner correcting the MCP joint hyperextension (Bouvier maneuver) (Fig. 19-8).

• Full active PIP joint extension: This indicates that the extensor mechanism is competent (Fig. 19-8A). This patient only needs correction of the MCP joint hyperextension and can use the intact extensor mechanism to obtain PIP joint extension. A static or a dynamic procedure will suffice for this patient. A static procedure is preferred because it is simpler.

• Incomplete active PIP joint extension with full passive extension: This indicates that the PIP joint is competent but that the extensor mechanism is incompetent (Fig. 19-8B and C). This patient will need a dynamic transfer, which is described later, to extend the PIP joint through the lateral band.

• Incomplete active and passive PIP joint extension: This indicates that there is a flexion contracture of the PIP joint (e.g., palmar skin shortage, stiff PIP joint) that needs to be addressed before any tendon transfers are considered (Fig. 19-8D).

Selection of motor: We use a static procedure (MCP joint volar plate advancement) for correction of the claw deformity in patients who are able to achieve full active extension of the PIP joint. In patients unable to achieve full PIP joint extension, we use a dynamic transfer and prefer the long or ring finger FDS as a motor. We prefer to use the ring finger FDS in low ulnar nerve palsy because the FDS is important for chuck grip, which is predominantly a function of the thumb and index and long fingers. In patients with high ulnar nerve palsy with a weak or absent FDP to the ring finger, the FDS remains the only flexor of the ring finger, and it is prudent to use the long finger FDS. Other motors that have been described include the extensor indicis proprius (EIP) and EDM (both have insufficient length, resulting in excessive tension of the extensor apparatus), wrist flexors (flexor carpi radialis [FCR], palmaris longus [PL]), and wrist extensors (extensor carpi radialis longus [ECRL], extensor carpi radialis brevis [ECRB]). (All need a tendon graft.) We use the ECRB lengthened with a PL tendon graft as the motor for restoring thumb pinch. Other motors that have been described include the brachioradialis, ECRL, extensor carpi ulnaris (ECU), EIP, and FDS.

FIGURE 19-1

FIGURE 19-2

FIGURE 19-3

FIGURE 19-4

FIGURE 19-5

FIGURE 19-6

FIGURE 19-7

FIGURE 19-8

Imaging

X-ray of the hand to examine the MCP and PIP joints

X-ray of the elbow (Fig. 19-9)

Nerve conduction studies

FIGURE 19-9

Surgical Anatomy

The muscles affected after low ulnar nerve palsy are the four hypothenar muscles (abductor digitorum minimus [ADM], flexor digitorum minimus [FDM], opponens digitorum minimus [ODM], and palmaris brevis [PB]), seven interossei muscles (four dorsal and three palmar), third and fourth lumbricals, and two thenar muscles (adductor pollicis [AP] and the deep head of the flexor pollicis brevis [FPB]). All these muscles are innervated by the deep motor branch of the ulnar nerve (Fig. 19-10).

In high ulnar nerve palsy, the flexor carpi ulnaris (FCU) and the ulnar half of the FDP (ring and small fingers) are affected in addition to the muscles listed earlier.

FIGURE 19-10

Positioning

The procedure is performed under tourniquet control.

The patient is positioned supine with the affected extremity on a hand table.

Procedure 1—Static Correction of Claw Deformity with an MCP Joint Volar Plate Advancement

Procedure

Step 1

The A1 pulley of each finger is completely divided and the flexor tendons retracted to expose the volar plate of the MCP joint (Fig. 19-13).

FIGURE 19-13

Step 1 Pitfalls

Take care not to extend the pulley division to the A2 pulley.

Step 2

The neck of the metacarpal (immediately proximal to the volar plate) is cleared of soft tissue, including periosteum.

Step 3

A distally based flap of the volar plate is created by making two parallel longitudinal incisions and releasing the proximal attachment over the head of the metacarpal (Fig. 19-14A and B).

FIGURE 19-14

Step 5

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