In life, we often encounter such a situation, numbness and discomfort in the little finger, often thought to have cervical spondylosis, to the hospital, but also often misdiagnosed as cervical spondylosis, by manipulation massage, traction, physical therapy and other treatments, no improvement, hand muscle atrophy continues to worsen, and the emergence of claw-shaped hand deformity. This is often the result of the ulnar nerve is often subject to compression.
A, the ulnar nerve is prone to jamming, which is related to its anatomical structure.
The ulnar nerve travels the ulnar nerve is composed of the cervical and thoracic 1 nerves, which is sent from the medial bundle of the arm, then descends along the medial biceps groove with the brachial artery, turns posteriorly down the middle of the arm, passes behind the medial epicondyle of the humerus into the ulnar nerve groove, and then enters the forearm. The ulnar nerve descends with the ulnar artery on the deep surface of the ulnar flexor carpi radialis muscle of the forearm to about 5 cm above the radial carpal joint and gives off the dorsal carpal branch of the ulnar nerve, then the nerve trunk descends, and this segment of the nerve is called the palmar branch of the ulnar nerve. The nerve divides into two superficial and deep branches through the radial side of the pisiform bone into the palm of the hand.
1.Anatomical structure of the elbow canal
The elbow canal is a bony fibrous canal formed on the basis of the ulnar nerve groove, its anterior, posterior and lateral walls are bony, the medial wall is the arcuate ligament, there are ulnar nerve and ulnar superior collateral vessels inside, when flexing the elbow the distance between the hawk and the medial epicondyle widens, the fascial tissue especially the arcuate ligament is strained after the elbow canal, at the same time the lateral ulnar collateral ligament projects medially, the volume of the elbow canal becomes smaller, the ulnar superior collateral artery is compressed, the ulnar nerve undergoes chronic ischemia.
When flexing the elbow, the ulnar nerve is stretched and the pressure in the elbow canal is increased, which affects the microcirculation and leads to the impairment of nerve conduction and affects the blood supply to the ulnar nerve, causing hypoxia and ischemia to the ulnar nerve or direct mechanical injury to the ulnar nerve and friction to the ulnar nerve. Although most of the ulnar nerve impingement occurs in the elbow canal, some parts of the distal and proximal ends of the elbow canal can also experience ulnar nerve impingement, such as the Struthers arch located at the level of 8 cm proximal to the medial epicondyle of the humerus, a thickened fascial band starting at the medial head of the triceps and ending at the medial septum, which can sometimes compress the ulnar nerve passing underneath, as well as the medial septum of the upper arm, the deep flexor of the forearm Tendon membrane, medial head of triceps brachii and other structures can cause inlay pressure on the ulnar nerve.
2.Anatomical structure of carpal ulnar canal
The carpal ulnar canal, also known as Guyon’s canal, is located on the ulnar side of the anterior carpal region and is composed of the transverse carpal ligament and the distal part of the lateral carpal ligament, with the ulnar artery, ulnar vein and ulnar nerve inside the canal, which is divided into deep and superficial branches. The upper mouth of the ulnar canal is enclosed by the proximal edge of the pea drum, the lateral carpal palmar collateral ligament and the transverse carpal ligament, and the lower mouth is enclosed by the lateral carpal collateral ligament, the short palmar muscle and its tendon membrane, the bean hook ligament, the tendon of the ulnar flexor muscle, and the tendon of the medial hand muscle group.
3.The muscles and sensory branches innervated by the ulnar nerve
The ulnar nerve sends out muscle branches in the forearm to innervate the ulnar flexor carpi radialis and the ulnar flap of the finger extensor flexor muscles. The deep branch of the ulnar nerve innervates the lesser interosseous muscle, the thumb muscle, all the interosseous muscles and the 3rd and 4th earthworm muscles. The superficial branch of the ulnar nerve (metacarpal branch) is located in the palm of the hand and is distributed over the skin of the lesser interosseous. The dorsal cutaneous branch is located on the dorsum of the hand and is distributed on the skin of the ulnar side of the hand and the ulnar half of the back of the ring finger, and the terminal superficial cutaneous branch is distributed on the distal skin of the ulnar side of the palm and the skin of the palmar surface of the ulnar side of the little finger and ring finger.
If the ulnar nerve is injured in the arm, the main manifestations are
1.Motor impairment: the flexion force of wrist is weakened, the thumb cannot be inwardly retracted, other fingers cannot be inwardly retracted and abducted, the ring finger and the end of the little finger cannot be flexed.
2.Sensory impairment: dull sensation in the ulnar nerve distribution area, and loss of sensation in the small fissure and little finger.
3.Muscle atrophy: the small pisiform interval is flat, due to the atrophy of interosseous and earthworm muscles, deep grooves appear in the metacarpal space, each metacarpophalangeal joint is excessively posteriorly extended, and the interphalangeal joint of the 4th and 5th fingers is flexed, manifesting as “claw-shaped hand”.
II. Clinical manifestations
Early mild nerve entrapment is almost asymptomatic and needs to cause local nerve ischemia to induce symptoms. In moderate injury, the patient has pain, numbness and abnormal sensation in the nerve sensory area, and Tinel’s sign at the jamming part is positive. The symptoms and signs are sometimes heavy and sometimes light, but with the gradual reduction of motor and sensory fibers, muscle atrophy and sensory impairment and abnormal two-point discrimination sensation appear. In late stages, nerve regeneration stops and Tinel’s sign may become negative.
Diagnosis
If the anatomical course of the ulnar nerve is known, combined with the history and symptoms, and the changes of symptoms, through careful physical examination, in most cases, the correct diagnosis can be made without electrophysiological examination.
1.History
Peripheral nerve injury has a clear history of trauma, the patient can point out the exact site of injury, and the time of injury. However, the early stage of peripheral nerve impingement may only be uncomfortable, a little pain, numbness, limb weakness, fear of cold, and also sometimes good and bad, the patient may not be able to recall the exact time of onset, because the symptoms are vague, most patients can not clearly point out the site of pain and discomfort. The onset of limb pain caused by peripheral nerve impingement generally has two characteristics, one is wavy, that is, good for a while and bad for a while, sometimes it can be several months without symptoms.
There is also a resting pain that improves after activity. Most of the patients have a history of being woken up by numbness at night, and after waking up from numbness, they can shake their hands or get up and move around. Ulnar nerve entrapment is also related to occupation and lifestyle habits: computer keyboard operators, assembly workers in production lines, large truck drivers, blacksmiths, habitual resting or sleeping with the elbow flexed, etc.
2.Check the body
Injury to the ulnar nerve, mainly manifested as claw-shaped hand deformity, ulnar side hemi-numbness of the little finger and ring finger, inability to separate and join fingers, positive paper-clip test, etc. If the jamming occurs at the elbow, the tinel sign at the elbow ulnar canal is positive, and if at the wrist, the tinel sign at the wrist ulnar canal is positive.
3.Special examination
(1) Tinel’s sign
Tinel’s sign is a very important test for peripheral nerve injury, which is performed by tapping in the direction of the nerve trunk, usually from distal to proximal, until the skin innervated by the nerve has pain or radiating pain, which indicates that the nerve regenerates here. The Tinel sign of nerve impingement is even more important, but generally the most obvious location of the Tinel sign is examined, so repeated tapping along the suspected impingement and the nerve trunk of the impinged nerve from distal to proximal, and then from proximal to distal, so that the most obvious location of the Tinel sign is obtained, which is basically the site of nerve impingement.
(2) Elbow flexion test
Numbness, pain and abnormal sensation on the ulnar side of the hand with maximum flexion of the elbow joint, forearm and hand are considered positive, suggesting that the ulnar nerve is embedded in the elbow.
(3) Froment’s sign
When the thumb and index finger are squeezed by force, the interphalangeal joint of the thumb is overflexed or the metacarpophalangeal joint is dorsally extended, which indicates the damage of the ulnar nerve.
(4) Wartenberg’s sign
If the little finger is outstretched and cannot be retracted, it indicates ulnar nerve injury to interosseous muscle paralysis.
(5) Fowler test
Press the proximal phalanges of the claw-shaped hand on the dorsal side of the hand to prevent the metacarpophalangeal joint from hyperextending, then make the patient extend the fingers and the claw-shaped hand disappears, suggesting that the deformity originates from interosseous muscle paralysis.
Differential diagnosis
Combined with the medical history and physical examination, it is basically possible to make a clearer diagnosis. However, the ulnar nerve impingement at the elbow should be differentiated from the following diseases.
1, cervical spondylosis: cervical spondylosis will also appear changes in hand and forearm sensation, but then the muscle strength of the interosseous muscles is all reduced, and there is often discomfort in the neck, and the nerve root pull test is positive.
2. Brachial plexus vascular compression syndrome (thoracic outlet syndrome): thoracic outlet syndrome with altered sensation in the hand and forearm and decreased muscle strength in the hand, positive for Tinel above and below the clavicle.
3, Guyon’s canal ulnar nerve compression: the identification at this point mainly depends on the sensation of the back of the hand, if the sensation of the back of the hand is normal and the flexor carpi radialis test is positive, it is likely that the nerve of the carpal ulnar canal is compressed.
4.Double card pressure: When there is inlay pressure in both elbow and wrist joints, electrophysiological examination should be done.
5.Motor neuron disease, etc.
V. Treatment
In case of early mild ulnar nerve compression, non-surgical treatment can be taken, including elbow joint braking, oral non-steroidal paroxysmal anti-inflammatory drugs, local closure, etc. If conservative treatment is ineffective, and the symptoms are progressively aggravated and muscle atrophy exists, surgical treatment can be performed. Elbow canal dissection and decompression, ulnar nerve epicondylar release, and ulnar nerve anterior displacement are performed.
It should be noted that the ulnar collateral artery is the main blood supply vessel of the ulnar nerve in the elbow segment, so it should be protected as much as possible during surgery; the ulnar nerve emits one to two articular branches and two thicker muscular branches in the elbow canal, which are the main nerves innervating the ulnar carpal flexors and the ulnar half of the deep finger flexors respectively, so care should be taken to protect them during surgery; special attention should be paid to whether the channel is wide and smooth after the anterior transposition, so that no new compression occurs. Complete hemostasis was performed to prevent re-embedding of the nerve and adhesions.