Ulnar nerve palsy results in significant loss of sensation and profound weakness, leading to a dysfunctional hand. Typical clinical findings include loss of key pinch, clawing, loss of normal flexion sequence of the digits, loss of the metacarpal arch, and abduction of the small finger. Further deficits in hand/wrist function are seen in high-level ulnar nerve palsy, including loss of ring- and small-finger distal interphalangeal flexion, decreased wrist flexion, and loss of dorsal sensory innervation. This article reviews the clinical findings seen in low and high ulnar nerve palsies, and reviews surgical options for correcting certain motor and sensory deficits.
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Ulnar nerve palsy results in significant loss of sensation and profound weakness, leading to a dysfunctional hand.
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A sound understanding of the anatomy of the different muscles and biomechanics of the potential transfers will ensure optimal results in treatment.
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This article reviews the clinical findings seen in both low and high ulnar nerve palsies, and reviews the surgical options for correcting certain motor and sensory deficits.
Introduction
Loss of ulnar nerve function leads to reduced dexterity and altered aesthetic appearance of the hand. Whereas the predominant cause of ulnar nerve palsy is traumatic in the Western world, systemic neurologic conditions such as leprosy still predominate in developing countries. A sound understanding of the anatomy of the different muscles and biomechanics of the potential transfers will ensure optimal results in treatment. The aims of this article are to: (1) briefly review the pertinent anatomy; (2) describe the functional deficits associated with both high and low ulnar nerve palsy; (3) discuss various reconstructive procedures for restoration of function, sensibility, and aesthetics to the hand.
Anatomy
The ulnar nerve is the terminal branch of the medial cord. It largely consists of nerve fibers from C8 and T1 nerve roots, but may have contributions from C7 or higher. In the upper arm, the ulnar nerve lies medial or posterior to the brachial artery and pierces the medial intermuscular septum at the mid portion of the arm at the arcade of Struthers. It lies anterior to the medial head of the triceps muscle and travels through the cubital tunnel at the level of the elbow to pass between the 2 heads of the flexor carpi ulnaris (FCU) (which it innervates). The FCU is usually the first muscle innervated by the ulnar nerve. As it continues distally, it lays on the volar surface of the flexor digitorum profundus (FDP) and sends branches to the FDP of the small and ring fingers. The next main branch off the ulnar nerve is the dorsal sensory branch, which originates approximately 7 cm proximal to the radial styloid and provides sensation to the ulnar aspect of the hand. At the level of the wrist, the nerve enters into Guyon canal with the ulnar artery. Here the nerve divides into deep and superficial branches. The superficial branch provides sensation to the small finger and ulnar half of the ring finger. The deep motor branch innervates the hypothenar muscles, the 2 medial lumbricals, all interossei, the adductor pollicis, and the deep head of the flexor pollicis brevis. The most distal motor branch innervates the first dorsal interosseous muscle.
Anomalous ulnar nerve anatomy and innervation patterns have been described. The location where the anomalous pattern occurs defines the type of innervation pattern ( Table 1 ). A forearm ulnar-median communication pattern is known as the Martin-Gruber connection. When the anomalous communication occurs in the palm, it is termed the Riche-Cannieu connection. The motor branch of the ulnar nerve and the recurrent motor branch of the median nerve are connected with ulnar to median innervation. By knowing both the normal and variant anatomy, one can explain the functional deficits seen in patients with ulnar nerve lesions.
| Martin-Gruber Anastomosis (Forearm Ulnar-Median Communication) | |||
|---|---|---|---|
| Type | Occurrence (%) | Description | Innervated Muscles |
| I | 60 | Motor branches from median nerve to ulnar nerve | Median muscles |
| II | 35 | Motor branches from median nerve to ulnar nerve | Ulnar muscles |
| III | 3 | Motor fibers from ulnar nerve travel with median nerve | Median muscles |
| IV | 1 | motor fibers from Ulnar nerve travel with median nerve | Ulnar muscles |
| Riche-Cannieu (palmar communications) | Anomalous connection between motor branch ulnar nerve and recurrent branch median nerve | ||
Anatomy
The ulnar nerve is the terminal branch of the medial cord. It largely consists of nerve fibers from C8 and T1 nerve roots, but may have contributions from C7 or higher. In the upper arm, the ulnar nerve lies medial or posterior to the brachial artery and pierces the medial intermuscular septum at the mid portion of the arm at the arcade of Struthers. It lies anterior to the medial head of the triceps muscle and travels through the cubital tunnel at the level of the elbow to pass between the 2 heads of the flexor carpi ulnaris (FCU) (which it innervates). The FCU is usually the first muscle innervated by the ulnar nerve. As it continues distally, it lays on the volar surface of the flexor digitorum profundus (FDP) and sends branches to the FDP of the small and ring fingers. The next main branch off the ulnar nerve is the dorsal sensory branch, which originates approximately 7 cm proximal to the radial styloid and provides sensation to the ulnar aspect of the hand. At the level of the wrist, the nerve enters into Guyon canal with the ulnar artery. Here the nerve divides into deep and superficial branches. The superficial branch provides sensation to the small finger and ulnar half of the ring finger. The deep motor branch innervates the hypothenar muscles, the 2 medial lumbricals, all interossei, the adductor pollicis, and the deep head of the flexor pollicis brevis. The most distal motor branch innervates the first dorsal interosseous muscle.
Anomalous ulnar nerve anatomy and innervation patterns have been described. The location where the anomalous pattern occurs defines the type of innervation pattern ( Table 1 ). A forearm ulnar-median communication pattern is known as the Martin-Gruber connection. When the anomalous communication occurs in the palm, it is termed the Riche-Cannieu connection. The motor branch of the ulnar nerve and the recurrent motor branch of the median nerve are connected with ulnar to median innervation. By knowing both the normal and variant anatomy, one can explain the functional deficits seen in patients with ulnar nerve lesions.
| Martin-Gruber Anastomosis (Forearm Ulnar-Median Communication) | |||
|---|---|---|---|
| Type | Occurrence (%) | Description | Innervated Muscles |
| I | 60 | Motor branches from median nerve to ulnar nerve | Median muscles |
| II | 35 | Motor branches from median nerve to ulnar nerve | Ulnar muscles |
| III | 3 | Motor fibers from ulnar nerve travel with median nerve | Median muscles |
| IV | 1 | motor fibers from Ulnar nerve travel with median nerve | Ulnar muscles |
| Riche-Cannieu (palmar communications) | Anomalous connection between motor branch ulnar nerve and recurrent branch median nerve | ||
Assessment
Before any treatment options are discussed, a thorough clinical evaluation of the patient is necessary. The characteristic clinical signs that reflect the motor loss, sensory loss, and level of injury in ulnar nerve palsy have been well described ( Table 2 ). Palsy of the ulnar nerve leads to multiple complex deficiencies, and the clinical significance of these vary according to age, relative joint laxity, soft-tissue and skin elasticity, and individual functional demands.
| Clinical Sign | Description |
|---|---|
| Duchenne sign | Clawing deformity of fingers |
| Jeanne sign | Hyperextension of the thumb MCP joint during pinch |
| Froment sign | Thumb IP joint hyperflexion with pinch |
| Masse sign | Flattened metacarpal arch and hypothenar atrophy |
| Andre-Thomas sign | Worsening of claw deformity when patient attempts to extend fingers by flexing the wrist (tenodesis effect) |
| Pollock sign | High ulnar nerve palsy, inability to flex DIP joint of ring and small fingers secondary to loss of flexor digitorum profundus to the respective digits |
| Pitres-Testut sign | Inability to abduct the middle finger radially and ulnarly |
| Wartenberg sign | Abducted small finger (inability to adduct extended small finger) |
| Earle-Valstou sign | Inability to cross the index and middle fingers |
The incident that led to the ulnar nerve palsy should be fully evaluated. The level of injury and mechanism can affect the prognosis and treatment of these patients. Ulnar nerve palsies are classified into high and low levels, where the nerve is affected above or below the elbow, respectively. The deficit and presentation varies between the 2 types of lesions and is discussed later.
Additional assessment includes evaluating the skin and soft tissues for any trophic ulcers occurring from sensory loss. A checklist of functioning and nonfunctioning muscles is created to better define the injury and availability of tendon transfers, especially for patients in whom the median nerve may be also be involved. In keeping with general principles of tendon transfers, all joints should be supple and deformities passively correctable.
The complex interaction between the intrinsic and extrinsic muscles becomes uncoupled as a result of intrinsic muscle paralysis, leading to clawing of the fingers. The unopposed pull of the long extensors leads to the metacarpophalangeal (MCP) joint assuming a position of hyperextension with the interphalangeal joints assuming a flexed position resulting from normal tension in the long flexor muscles, the so-called claw hand. As median innervated intrinsics are intact, the clawing is restricted to the ulnar 2 digits. Ironically, with a high ulnar palsy (and more muscle loss) the lack of flexor tone in the ulnar FDP results in a less severe claw, referred to as the “ulnar paradox.” Over time, the deformity worsens as the MCP volar plate stretches along with attenuation of the central slip of the extensor apparatus, and the proximal interphalangeal (PIP) capsuloligamentous complex contracts, leading to fixed claw deformity. To assess the integrity of the extensor apparatus at the PIP joint, the Bouvier maneuver ( Fig. 1 ) is performed. This maneuver involves passively stabilizing the MCP joint in flexion and asking the patient to actively extend the PIP joint. A positive maneuver is the demonstration of active extension of the PIP, which indicates an intact and functioning central slip. Any stiffness at the PIP joint requires a period of stretching and serial splinting through therapy and fitting of an orthotic device ( Fig. 2 ).
Deficits and treatment
There are various functional deficits and various treatment options available to address them.
Aesthetic
With time, muscle atrophy leads not only to functional deficits but also changes the appearance of the hand. Muscle wasting is noticeable in the interosseous spaces and is most apparent in the first web space, and can be disconcerting to some patients. Although not routinely required, injection of dermal fillers such as fat autograft obtained by liposuction may be considered to fill subdermal defects in the interosseous spaces on the dorsum of the hand.
Sensory
Sensation is lost in ulnar nerve palsy over the palmar side of the small finger and the ulnar half of the ring finger. In high ulnar nerve palsy, additional sensory loss over the dorsoulnar aspect of the hand is also observed. Loss of protective sensation along the ulnar border of the hand can be problematic in some patients who may be prone to injuring or burning their hands as a result of their occupation or hobbies. In addition, the absence of sensation on the tip of the small finger can lead to skin breakdown and infections from minor repetitive trauma that is neglected. Most patients can cope with the diminished sensibility by compensating with visual feedback, but if some patients develop recurrent injuries owing to the sensory loss, surgical intervention with sensory nerve transfer can be considered. Bertelli has described using cutaneous branches of the median nerve to the palm as well as the palmar cutaneous branch of the median nerve. The cutaneous nerves are transferred to the ulnar proper digital nerve of the small finger. Another option is to transfer the radial digital nerve of the middle finger (branch of the median nerve) ( Fig. 3 ) or radial digital nerve of the ring finger to the ulnar proper digital nerve of the small finger.
Motor
Muscles and subsequent movements that are affected in ulnar nerve palsy are listed in Box 1 .
Low Ulnar Nerve Palsy (Below-Elbow Injury)
Loss of:
Sensation small finger and ulnar half of ring finger
Palmaris brevis
Hypothenar musculature
Abductor digiti minimi
Flexor digiti minimi brevis
Opponens digiti mini
Ulnar 2 lumbricals
Dorsal and volar interossei
Adductor pollicis
Deep head of flexor pollicis brevis
Clawing more pronounced because flexor digitorum profundus still innervated further proximally
High Ulnar Nerve Palsy (Above-Elbow Injury)
Includes low ulnar nerve palsy deficits plus:
Loss of ring- and small-finger flexor digitorum profundus
Loss of flexor carpi ulnaris
Loss of sensation dorsoulnar portion of hand
Clawing less pronounced because ring and small finger flexor digitorum profundus not functioning, hence no DIP joint flexion
Abbreviation: DIP, distal interphalangeal.
Low palsy
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All interossei and ulnar 2 lumbricals resulting in loss of dexterity, weakness of grip, and clawing of ulnar 2 digits.
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Adductor pollicis leading to weakness in key pinch.
High palsy
In lesions of the ulnar nerve above the elbow, in addition to aforementioned muscles, the following muscles and movements are also involved:
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FCU, with weaker flexion and ulnar deviation of the wrist
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FDP to the ring and small fingers, with loss of ring-finger and small distal interphalangeal (DIP) joint flexion.
Partial Loss of Wrist Flexion
Contraction of the FCU along with its counterpart on the extensor aspect of the wrist helps to stabilize the hand in power grip. Patients with loss of FCU activity do not observe any notable deficit with wrist motion, and reconstruction is not required. In special circumstances where ulnar deviation of the wrist is considered essential, the flexor carpi radialis innervated by the median nerve can be transferred to the FCU tendon.
Loss of Ring-Finger and Small DIP Joint Flexion (Weakness of Grasp)
In high ulnar nerve palsy, grasp is weakened approximately 60% to 80% secondary to loss of contraction in the ulnar half of the flexor profundus in addition to the loss of intrinsic function. Lack of ability to close the ulnar side of the palm in forceful grip leads to difficulty with firmly holding on to objects. Restoration of flexion at the DIP joints of the ring and small fingers can be most easily achieved by adjacent suturing of the FDP tendons to the median innervated middle FDP tendon at the level of the distal forearm ( Fig. 4 ). The index-finger FDP tendon is not included, to preserve its independent function. As mentioned earlier, once flexor tone is restored to the ulnar 2 digits, the patient may note increased apparent clawing of the digits and should be forewarned about this paradox.
Clawing
Clawing is a result of a combination of lack of MCP flexion and PIP extension, both essentially served by the intrinsics in the hand. In simple clawing with positive Bouvier maneuver, maintaining the MCP joint in flexion with a passive tenodesis or active tendon transfer will suffice to correct the clawing. The various options for claw correction are summarized in Table 3 and include bony procedures, soft-tissue tightening, and tendon transfers.
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