Pinched the ulnar nerve

When the ulnar nerve is pinched - one of the three main nerves of the hand, then its compression lesion develops in the form of mononeuropathy of the upper limb; its code for ICD-10 is G56.2. Compressive neuropathy is one of the most interesting, but at the same time the most difficult aspects of hand surgery. Compression or capture neuropathy occurs as a result of compression or pinching of a nerve at some point during its course in the upper limb. This can lead to a change in function and, if untreated, leads to a significant limitation of the function of the hand. Therefore, it is necessary to diagnose and treat these conditions at an early stage. [1] 

Epidemiology

Pinched the ulnar nerve in the elbow joint is the second most common compression neuropathy in the arm. A disease can seriously interfere with daily life and work. However, risk-based epidemiological studies are rare. [2]

The exact statistics of cases of pinched ulnar nerve is unknown, however, as clinical experience shows, its compression in the elbow joint is the second most frequent cause of  neuropathy of the upper extremities . However, Mondelli conducted a retrospective study based on electromyography and estimated the standardized annual frequency of ulnar compression in the elbow joint at 20.9 per 100,000. The  [3] prevalence of ulnar compression is estimated to be 1% in the United States. [4]

Experts note that among peripheral mononeuropathies in the first place in terms of prevalence is carpal or carpal tunnel syndrome, which occurs when the median nerve of the hand is pinched; on the second - cubital tunnel syndrome when the ulnar nerve is pinched in the elbow joint.

Causes of the pinched ulnar nerve

Highlighting the main causes of squeezing of the ulnar nerve (nervus ulnaris), neuropathologists emphasize, for the most part, its traumatic origin due to damage at the level of the forearm (code S54.0 according to ICD-10), which is attributed to  injuries of the peripheral nerves . Pinching may also result from an injury to the shoulder girdle; fracture of the condyle or epicondyle of the humerus; severe bruise of the elbow (especially a direct blow to its inside); dislocation or fracture of the elbow joint; wrist injuries.

Often after injuries local scars form, due to improper fusion of the fracture, bone structures are deformed, post-traumatic soft tissue contractures occur along the nerve.

Common causes of compression are prolonged bent position of the elbow joint and excessive mechanical stress - multiple bending of the elbow or wrist (intense repetitive movements); reliance on the elbow (pressure on the ulnar bone) for a long time.

If a nerve pinches in the elbow joint - in the tunnel behind the inner part of the elbow, it is diagnosed  with cubital canal syndrome . [5]

Specialists take into account the presence of congenital and acquired deformations of the elbow joint - the valgus or varus elbow, predisposing to pinching of the ulnar nerve. Cubitus valgus is a deformation in which the forearm elongated along the body deviates from it (by 5-29 °). Congenital hallux valgus is observed in Turner or Noonan syndrome, and acquired can be a complication of fracture of the lateral condyle of the humerus. The deformation of cubitus varus is expressed in the deviation of part of the elongated forearm to the midline of the body.

In chronic pinching of the ulnar nerve, when it passes through the wrist, the ulnar tunnel syndrome, Guillon canal syndrome or ulnar wrist syndrome develops  .

By the way, both syndromes can be idiopathic. Read more:

• Types of neuropathy of the ulnar nerve
• Tunnel syndromes

Risk factors

Some risk factors for squeezing the ulnar nerve include:

• rheumatoid arthritis;
• ulnar arthritis, osteoarthritis or deforming arthrosis;
• swelling of the elbow joint;
• tendon inflammation (tendonitis);
• synovial chondromatosis;
• synovial cyst (hygroma or ganglion) in the wrist;
• the presence of supracondylar osteophytes;
• osteoma, cortical hyperostosis, lipoma and other malformations;
• the presence of muscle abnormalities of the upper extremities, for example, 12-15% of people have an extra short muscle anconeus epitrochlearis passing over the ulnar nerve, crossing the ulnar nerve posterior to the ulnar tunnel.
• male sex and fracture of the elbow joint predispose to the development of compression of the ulnar nerve in the elbow joint. [6], [7]
• smoking was found to be a risk factor for ulnar compression. [8]

Pathogenesis

The anatomical and topographic features of the  ulnar nerve , which is one of the five terminal branches of the brachial plexus (brachial plexus) - the middle bundle of the subclavian part, largely explain the pathogenesis of its pinching, as there are places of potential compression along the nerve.

From the starting point, the path nervus ulnaris lies down along the medial surface of the humerus (humerus); in the middle of the shoulder, the nerve passes through the medial intermuscular septum (called the Struthers Arcade) and follows inside the triceps brachii (musculus triceps brachii). Occasionally, a squeezing of the ulnar nerve can occur here, since in the lower part of the shoulder it is fixed by triceps.

In the area of the elbow joint, the nerve can be pinched when passing through the supracondylar sulcus (sulcus nervi ulnaris). And very often, pinching occurs in the ulnar canal (canalis ulnaris) or cubital tunnel: in Latin, ulna is the ulna, and cubitus is the elbow.

This tunnel is located between the middle epicondyle (medial epicondyle) of the shoulder and the process of the ulna (olecranon) and has an elastic "roof" of the tendon arch - myofascial trilaminar ligament (fascia of the ulnar canal or Osborne ligament). When bending the arm at the elbow, the shape of the canal changes, and it narrows by half, which leads to dynamic compression of the ulnar nerve.

Going down the forearm through the flexor muscles of the hand and pronators of the forearm, nervus ulnaris enters the hand through the fibro-bone tunnel of the wrist up to 4 cm long - the Guillon canal, and this is also a typical localization of squeezing the ulnar nerve. Pinching in this channel is the result of its excessive squeezing from the outside with a bent wrist. However, the mechanism of pinched the ulnar nerve in the wrist is different in the presence of an aberrant long muscle of the palm (musculus aberrant palmaris longus).

Symptoms of the pinched ulnar nerve

The ulnar nerve provides the innervation of the little finger, half of the ring finger and sensory innervation of the skin in the hypotenar region - muscle elevation in the palm of the hand (down from the little finger) and the dorsal region of the hand. It also controls most of the small muscles of the hand (involved in flexion and extension of the medial and distal phalanges of the fingers) and two large muscles of the front of the forearm, which flex and extend the arm in the wrist and support the exciting efforts of the upper limbs.

Therefore, as a result of its pinching, motor, sensory or mixed - motor-sensory symptoms occur. In this case, the very first signs are sensory, which are manifested in loss of sensitivity of the ring finger and little finger and paresthesia, that is, numbness or tingling (especially pronounced when the elbow is bent).

Motor symptoms are expressed in muscle weakness (weakening of the grip) and difficulties in coordinating the fingers innervated by the ulnar nerve. When it is pinched in the elbow joint, a neuralgic pain  in the elbow region of varying intensity and duration occurs , often extending to the shoulder. Compression inside the Guyon canal leads to muscle weakness and loss of sensitivity of the outer side and back of the hand.

Categories of Nervous Dysfunction (McGowan [9]and Dellon [10])

• Mild nervous dysfunction involves periodic paresthesia and subjective weakness.
• Moderate dysfunction is accompanied by intermittent paresthesias and measurable weakness.
• Severe dysfunction is characterized by persistent paresthesias and measurable weakness.

More information in the material:  Symptoms of damage to the ulnar nerve and its branches .

Complications and consequences

Regardless of the location of the pinched ulnar nerve, the consequences can be in the form of partial closed damage to the fibers of its trunk (axonotmesis) or more serious open damage to the entire trunk, perineuria and epineuria (neurotmesis). Depending on this, complications such as:

• ulnar neuropathy ;
• ischemia and fibrosis of the ulnar nerve;
• damage to the myelin sheath of axons, leading to the cessation of transmission of nerve impulses.

Late ulnar paralysis (and limb paralysis) and irreversible muscle wasting are also possible - muscle wasting  (amyotrophy) of the hand .

Diagnostics of the pinched ulnar nerve

The diagnosis of this damage begins with an anamnesis, a physical examination of the patient and an analysis of the symptoms. A number of special neurodynamic tests are used to assess the degree of impaired mobility of various parts of the limb and the level of sensory deficiency.

Provocative tests: [11]

• Tinel test along the ulnar nerve
• Elbow flexion test.
• A provocative pressure test (where direct pressure is applied to the elbow tunnel for 60 s) and
• Combined elbow pressure bend test.

The positive Tinel test is only 70% sensitive, while the elbow flexion test is 75% sensitive after 60 seconds. However, after 60 seconds, the pressure test is 89% sensitive, and the combined elbow and pressure bend test is 98% sensitive. These test results can be used in combination to better diagnose cubital channel syndrome.

Predisposing reasons:

• Children's supracondylar fracture (late ulnar paralysis)
• Chronic Hallux Valgus
• Fractures of the elbow joint that are treated without transplantation of the ulnar nerve (fractures of the ulnar process, fractures of the distal part of the humerus, medial supracondylar fractures).

Instrumental diagnostics are carried out: an x-ray of the elbow or wrist (to detect abnormalities of bone structures); Ultrasound of the nerves ; electromyography (study of nerve conduction). [12]

Differential diagnosis

Differential diagnosis should take into account the presence of similar neurological symptoms in: carpal tunnel syndrome associated with compression of the median nerve of the hand; pinching of the radial nerve (with the development of arch support syndrome or Froze syndrome); Kilo-Nevin syndrome; medial epicondylalgia (golfer's elbow); radiculopathy and spondylosis of the cervical spine; brachial plexopathy; peripheral polyneuropathy; chest exit syndrome (scalene syndrome); amyotrophic lateral sclerosis; Pancost-Tobias syndrome in lung cancer, primary bone tumors.

Treatment of the pinched ulnar nerve

Mild cubital canal syndrome can often be treated conservatively. There is a tendency to spontaneous recovery in patients with mild and / or intermittent symptoms, if you can avoid provocative causes and use adequate rest.

According to the Cochrane Database Syst Review (2016), the treatment of ulnar nerve pinches, first of all, requires the removal of physical exertion from the affected limb and its immobilization using an orthosis. Restriction of professional activity may be required if, during work, the symptoms of tunnel syndromes intensify. [13]

Medications for squeezing the ulnar nerve are used to relieve pain and swelling, and are usually non-steroidal anti-inflammatory drugs. All details in the materials:

• Neuralgia Pills
• Treatment of upper limb neuropathy
• Neuropathic pain treatment

Although corticosteroids are very effective, their injections are generally not used due to the high risk of nerve damage.

Massage when the ulnar nerve is pinched is aimed at decompressing it and is effective to relieve symptoms. In particular, it helps to relieve nerve compression by massage of tense and shortened muscles with subsequent stretching to lengthen them.

Prevention of stiffness in the elbow and wrist is therapeutic gymnastics when the ulnar nerve is pinched, that is, special exercises to maintain muscle tone and expand the range of movements that patients undergo physical therapy. To restore motor function and gradually build up lost muscle strength, the whole complex of physiotherapy is important. In more detail in the publication -  Physiotherapy for neuritis and peripheral nerve neuralgia .

In severe cases - as a last resort - they resort to surgical intervention (expansion of the cubital tunnel, decompression with transposition of the nerve, epicondiectomy, etc.). [14]

Alternative treatments include applying ice to the elbow or wrist (for pain and swelling), as well as ingestion of water infusions or alcohol extracts from plants with antioxidant and neuroprotective activity such as Ginkgo biloba, Salvia officinalis and basil (Ocimum basilīicum).

Prevention

Prevention of squeezing of the ulnar nerve can be considered the exclusion of long loads on the elbow joints and wrists, the periodic interruption of monotonous movements with the participation of these anatomical structures (straightening the arms), sleep with straight elbows, adequate physical exertion (to increase muscle strength) and timely medical attention - in the event of the appearance of at least one of the symptoms listed above.

Forecast

The dependence of the prognosis on the degree of compression effects on the nerve and a timely visit to a neuropathologist is unconditional. So, if the symptoms of pinching are mild, then almost 90% of patients started conservative therapy on time leads to their removal and restoration of all functions of the ulnar nerve. With more severe symptoms and delay in seeking medical help, treatment brings a positive result in only 38% of cases.