Anatomy of the ulnar nerve: It originates from the medial bundle of the brachial plexus, begins to be located on the medial side of the brachial artery, and then gradually moves to the ulnar side, enters the forearm through the ulnar nerve sulcus at the elbow, and enters the palm with the ulnar artery in the middle of the forearm. In the hand, it innervates all the interosseous muscles, the piriformis muscle, the two ulnar earthworm muscles, the bunion and the deep head of the short flexor of the thumb. The sensory branch distributes one and a half fingers on the ulnar side. After ulnar nerve injury, paralysis of interosseous muscle, bunion muscle, ulnar side two earth muscles and small fissure muscle occurred, manifested as hyperextension of metacarpophalangeal joint, flexion of interphalangeal joints, with the ring and little finger being significant, presenting the deformity of “claw-like hand”. The fingers cannot be close to each other, and the paper clip test is positive. The skin sensation of one and a half fingers on the ulnar side is lost. Clinical features: ① “claw-like hand” ② atrophy of the small fissure ③ positive paper clip test ④ loss of sensation in one and a half fingers on the ulnar side Anatomy of the radial nerve: it originates from the posterior bundle of the brachial plexus, obliquely descending outward from the posterior part of the axillary artery to the posterior part of the humerus, and then following the radial nerve sulcus to the external anterior humerus, and then enters into the forearm anterior to the external epicondyle of the humerus, and divides into two branches, the superficial and the deep. It innervates the triceps brachii muscle in the upper part of the upper arm, and the brachioradialis and radial extensor carpi radialis longus above the elbow joint. The superficial branch innervates the short extensor carpi radialis brevis. The deep branch innervates the posterior rotator, ulnar extensor carpi radialis brevis, extensor digitorum, extensor digitorum longus, extensor hallucis longus, extensor digitorum longus, and extensor hallucis longus. The sensory branch originates from the superficial branch, which is distributed in the skin of two and a half fingers on the back of the radial side of the wrist and hand. Characteristics after injury 1, can not extend the elbow (in the upper arm above the central high injury, triceps paralysis can not extend the elbow) 2, typical wrist ptosis (in the central humerus injury, the forearm extensor group paralysis wrist can not dorsal extension) 3, atypical wrist ptosis (in the elbow joint below or deep branch injury, the function of the wrist extensor muscle is still present, there is no wrist ptosis) 4, sensory loss of the area of Median Nerve Anatomy: originated from the brachial plexus medial tract and the lateral tract, in the upper arm with the brachial artery, and the brachial nerve, and the brachial nerve. In the upper arm, it runs parallel to the brachial artery, enters the forearm and is located in the deep layer of the superficial flexor digitorum superficialis muscle, and then passes through the carpal tunnel to the metacarpal area. There is no branch in the upper arm. ② In the forearm, it innervates all the muscles of the flexor side of the forearm except the ulnar flexor carpi ulnaris and the two deep flexor digitorum superficialis muscles on the ulnar side. ③ In the palm, it innervates the adductor hallucis longus, flexor hallucis longus, contralateral hallucis longus, and the first and second earthworm muscles ④ Sensation is distributed in the skin of the three and a half fingers on the radial side ① In the case of an injury above the elbow, paralysis of all the muscles of the forearm except for the ulnar flexor carpi radialis muscle and ulnar flexor digitorum profundus muscle, and dysfunction of flexion of the thumb, the thumb, and the demonstrative and middle fingers. ② In wrist injury, paralysis of the piriformis muscle and the earthworm muscle. (iii) Loss of skin sensation in the three and a half fingers on the radial side of the palm and the dorsal ends of the thumb, index and middle fingers. Clinical features of median nerve injury: A. Thumb and forefinger can not be flexed (can not make “O” shape); B. Thumb can not be palm to palm; C. “Ape hand”; D. Atrophy of the greater piriformis; Sciatic nerve injury: Posterior dislocation of the hip joint, supracondylar fracture of the femur and dislocation of the knee; Fibular head or fibula. Fracture of the fibular head or neck of the fibula, compression injury, etc. Anatomy: The sciatic nerve leaves the pelvis at the inferior foramen of the pectus excavatum to the buttocks, where it lies in the deep part of the gluteus maximus muscle (between the sciatic tuberosity and the greater trochanter) and travels down between the biceps femoris muscle and the semitendinosus and semimembranosus muscles and innervates these three muscles. It divides into the tibial nerve and common peroneal nerve in the lower 1/3 of the thigh. The tibial nerve travels with the N artery in the N fossa and then follows the posterior tibial artery to the lower back of the ankle to the plantar aspect of the foot. During this time, it sends out a muscular branch to innervate the superficial and deep muscles of the posterior calf and the plantar muscles, and a cutaneous branch to innervate plantar sensation. The common peroneal nerve travels down the medial side of the biceps femoris muscle in the lateral side of the N fossa, bypasses the neck of the fibula and enters the anterolateral side of the calf and descends to the dorsum of the foot, and its deep branch innervates the anterior tibialis muscle group and the extensor digitorum brevis muscle, and its superficial branch innervates the peroneus longus and shortus muscles. Clinical manifestations of sciatic nerve injury ① motor: N cord muscle, calf and all muscles of the foot are paralyzed ② sensory: below the knee (except for the medial calf and the inner ankle saphenous nerve innervation area) sensation are lost. ③ Nutrition: severe nutritional changes, often with deep ulcers on the soles of the feet ④ In high sciatic nerve injury, the ankle muscles are completely paralyzed, and the walking posture is like a farmer’s threshing position, which is known as “crop foot” ⑤ Low sciatic nerve injury is divided into two types: tibial nerve injury and common peroneal nerve injury. Tibial nerve ①movement: Achilles tendon and flexor muscles of the toes are paralyzed, toes are tilted up, showing “claw-like foot” deformity. Sensation: loss of sensation at the back of the calf, lateral edge of the foot, lateral part of the heel and sole of the foot. Common peroneal nerve ①motor: complete paralysis of tibialis anterior and extensor muscles, “foot drop” deformity and cross-threshold gait. Sensation: loss of skin sensation in the lower leg and lateral dorsum of the foot.