Median Nerve Injury

　　Median nerve injury occurs more frequently, and the injured site is mostly at the wrist or forearm, and the injury at the upper arm or axilla is less common.

　　1. Stretch injury:The most common. Most of them are caused by the arm being pulled into the machine.

　　2. Crush injury:Mainly due to forearm fracture or scar contracture, often accompanied by severe extensive soft tissue injury.

　　3. Cutting injury:Glass cuts in daily life or work, or accidental injury during the operation of the forearm.

　　4. Gunshot or drug misinjection into the nerve trunk causing injury:Compared with the above injuries, these two types of injury cases are less common.

　　5. Ischemic contracture is often associated with median nerve injury.

　　The median nerve has no branches above the elbow, and its injury can be divided into high-level injury (above the elbow) and low-level injury (wrist). When injured at the wrist, the paralysis of the thenar muscles and the lumbrical muscles it支配 and the sensory disturbances of the hand it支配 are manifested mainly as dysfunction of thumb opposition and sensory disturbances in the radial half of the hand, especially the disappearance of the distal phalanx sensation of the index and middle fingers. In cases of injury above the elbow, the muscles of the forearm it支配 are also paralyzed, in addition to the above symptoms, there are also dysfunction of thumb and index and middle finger flexion. If not treated in time, it can lead to excessive adhesion of nerves and tendons, muscle atrophy, and joint stiffness.

　　1. Median Nerve Injury at the Wrist

　　1. Exercise:The three thenar muscles, namely the abductor pollicis brevis, the flexor pollicis brevis, and the superficial head of the flexor pollicis brevis, are paralyzed, so the thumb cannot be opposed, cannot form a 90° angle with the palm plane, and cannot contact other fingertips with the palm, resulting in atrophy of the large thenar muscle, thumb adduction, and the formation of an ape-like hand deformity. Sometimes the flexor pollicis brevis is supplied abnormally by the ulnar nerve.

　　2, Sensation:Loss of hand sensation is most affected by median nerve injury. After injury, the radial side of the palm and the distal phalanx of the thumb, index, middle, and ring fingers lose sensation, severely affecting hand function, making it easy to drop objects, lack of实物感, and prone to external trauma and burns.

　　3. Nutritional changes:The skin and nails of the fingers have significant nutritional changes, the phalanges atrophy, and the fingertips become smaller and pointed.

　　Second, elbow median nerve injury

　　1. Exercise:In addition to the above, there is also paralysis of the pronator teres, the radial flexor muscle of the wrist, the pronator quadratus, the palmaris longus, the superficial flexor muscle of the finger, the deep flexor muscle of the finger (radial half), and the flexor pollicis longus. Therefore, the thumb and index finger cannot be flexed, and these two fingers remain straight when making a fist. Some middle fingers can be partially flexed, and the metacarpophalangeal joints of the index and middle fingers can be partially flexed, but the interphalangeal joints remain straight.

　　2. Sensory and nutritional changes are the same as before. It is common to have burning neuralgia in conjunction with median nerve injury.

　　Attention should be paid to the use of splints to keep the affected joints in functional positions. After the median nerve injury, not only does it affect the flexion of the thumb and fingers and the opposition function, but the loss of somatosensation also has a significant impact on the function of the hand. Therefore, restoring somatosensory function is an important task. For decreased sensation, let the patient touch various objects of different shapes, sizes, and textures, such as plush, coins, keys, and daily necessities. Practice them first under direct vision, and then in the dark. Gradually, the patient can recognize different objects. For hyperesthesia, desensitization treatment is needed, which means educating the patient to use the sensitive area more, self-massage the sensitive area, and stimulate the sensitive area with items of different materials. Educate the patient to protect the area with sensory impairment and not to touch dangerous objects with the affected hand to prevent burns, injuries, and pressure ulcers. When the finger muscle strength recovers to grade 3, guide the patient to do more fine motor exercises and ADL exercises.

　　There is no related laboratory examination for the diagnosis of this disease, which is mainly based on its clinical manifestations and medical history. Auxiliary examinations are rarely used, mainly some routine physical examinations, such as electromyography, which helps to judge whether there is nerve injury and its degree.

　　1. The thumb abduction and opposition are normal.

　　2. After the median nerve injury at the elbow, the thumb cannot be opposed, and the thumb, index, and middle fingers cannot be flexed.

　　3. Areas with decreased or absent sensation.

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　　First, treatment

　　1. For open injuries, it is necessary to strive for primary repair.For patients with uneven nerve ends, severe contusions, or severe wound contamination, delayed primary repair can be performed. For closed nerve injuries, those with mild degrees should be observed for 1 to 3 months. If there is recovery, surgery is not necessary. If not, surgery should be performed immediately.

　　(1) General treatment is selected for the following situations: ① The median nerve injury is mild, and the muscle and sensory disorders are mainly减退, without major motor dysfunction. ② The nerve injury is within 3 months, and there are signs of functional recovery.

　　(2) Surgical Treatment

　　① Indications for Surgery: A. Conservative treatment for closed nerve injury after 3 months still shows no recovery. B. Open nerve injury.

　　② Surgical Method: Median Nerve Surgery Exposure:

　　A. The incision for exposing the median nerve in the upper arm is along the anterior margin of the axilla and the medial edge of the biceps tendon to the elbow joint, and then turns outward to the elbow fossa along the transverse crease on the palmar side of the elbow. Then, it turns forward to the middle line of the forearm. Cut the fascia of the arm, and expose the brachial nerve and vascular bundle. The median nerve is located on the lateral side of the brachial artery in the upper segment of the upper arm, gradually moving from the anterior side of the brachial artery to the medial side, and then descending along the inner edge of the biceps brachii to the front of the elbow joint.

　　B. The incision for exposing the median nerve in the forearm is from the median line in front of the elbow downward to the middle of the forearm, and then to the wrist. The muscular branches that the median nerve divides near the pronator teres all come from the ulnar side of the nerve trunk, so it is safer to separate from the radial side of the median nerve. Before the median nerve enters the pronator teres, it first divides into two thicker branches to the muscle, then passes through the deep and superficial heads of the muscle, and then branches to other flexor muscles.

　　C. When exposing the median nerve at the wrist, incise along the transverse crease of the wrist and the palmar crease, and it is necessary to incise the transverse ligament of the wrist and the palmar fascia. Separate from the ulnar side of the median nerve to avoid injury to the lateral branch that支配支配the thenar muscles. Choose the corresponding nerve surgery according to the nature of the injury.

　　When the nerve defect is less than 2cm, it can be overcome by flexing the wrist joint and freeing the proximal and distal nerve trunks. However, the maximum flexion angle should be 20°, and the free range should be 2-3cm.Excessive free grafting can affect the blood supply to the nerve ends. Nerve transplantation should be performed when the nerve defect is greater than 4cm. If there is no confidence, the tourniquet can be relaxed, and if the blood supply to the nerve ends recovers slowly, nerve transplantation should be performed.

　　It is not advisable to force suture when there is a soft tissue defect.If the condition of soft tissue is good, skin grafting or flap transfer can be performed. For patients who need flap transfer, if there is a large nerve defect, flap repair should be performed first, and nerve transplantation will be performed in the second stage.

　　II. Prognosis

　　General prognosis is poor.