Based on the history of trauma, clinical symptoms and examination, determine the site, nature and extent of nerve injury. Clinical examination 1.Wound examination Check the presence of wounds, and if there are wounds, check their extent and depth, soft tissue injury and the presence of infection. Identify the path of gunshot or shrapnel wounds, whether there are vascular injuries, fractures or dislocations, etc. If the wound has healed, observe the scar situation and the presence of aneurysm or arteriovenous fistula formation, etc. 2.Limb posture Observe whether there is deformity of the limb. Radial nerve injury has wrist prolapse; ulnar nerve injury has claw-like hand, that is, the 4th and 5th finger metacarpophalangeal joint hyperextension, interphalangeal joint flexion; median nerve injury has ape hand; common peroneal nerve injury has foot prolapse, etc. If the time is too long, due to the loss of balance of the antagonistic muscles, joint contracture and other changes may occur. 3, the examination of motor function according to muscle paralysis to determine the nerve injury and its degree, using the six-level method to distinguish muscle strength. Level 0 – no muscle contraction; Level 1 – slight muscle contraction; Level 2 – not against the direction of gravity, can achieve full joint mobility; Level 3 — against the direction of gravity, can achieve full joint motion, but can not add any resistance; Level 4 — against the direction of gravity and add some resistance, can achieve full joint motion; Level 5 — normal. -normal. Peripheral nerve injury causes muscle weakness, loss of tone, and progressive muscle atrophy. Depending on the degree of nerve damage, muscle strength has the above-mentioned differences, in the process of nerve recovery, muscle atrophy gradually disappears, such as adhere to the exercise can have continuous progress. 4.Sensory function examination Check the pain, touch, temperature, two points of distinction and its change range to determine the degree of nerve damage. Generally, the pain and touch sensation can be checked. Note that the sensory supply area is a single nerve or other nerve supply overlap, can be compared with the healthy side of the skin. Physical sensation and shallow touch are fine sensations, while pain and deep touch are coarse sensations. After nerve repair, coarse sensation is restored earlier and better. The degree of sensory dysfunction can also be distinguished by a six-level method: level 0 – no sensation at all; level 1 – deep nociception exists; level 2 – nociception and partial tactile sensation; level 3 –Level 4 – complete pain and tactile sensation, and two points of distinction, but at a greater distance; Level 5 – completely normal sensation. 5, nutritional changes After nerve injury, the skin of the innervated area is cold, sweatless, smooth and atrophied. Sciatic nerve injuries often occur with plantar pressure sores and frostbite on the foot. No sweat or little sweat area generally conforms to the range of sensory loss. Sweat test can be made, the commonly used methods are (1) iodine-starch test: apply 2% iodine solution on the palm side of the finger, dry and apply a layer of starch, then bake with a lamp, or drink hot water after appropriate exercise to make the patient sweat, sweating becomes orchid. (2) ninhydrin (Ninhydrin) fingerprint test; the affected finger or toe on clean paper and press a fingerprint (also in hot drinks after sweating and then press). Use a pencil to draw the finger toe range, and then put into 1% ninhydrin solution. If there is sweat, the fingerprints will appear in the fingerprint dot. Soak with nitric acid solution to fix, can be stored for a long time. Because the sweat contains a variety of amino acids, after meeting ninhydrin turns purple. The nerve recovery can be observed through multiple checks and comparisons. 6.Reflex Depending on the muscle paralysis, the tendon reflex disappears or is diminished. 7.Pseudoneuroma at the proximal end of the nerve break, often with severe pain and tenderness, and tenderness dispersion to the innervation area of that nerve. 8.Nerve stem percussion test (Tinel’s sign) When the nerve is damaged or after repair of the damaged nerve, the nerve is tapped in the plane of injury or at the site reached by the nerve growth, that is, radioactive numbness occurs in the distribution area of that nerve, which is called positive Tinel’s sign.