Cubital Tunnel Syndrome

　　1. Etiology

　　Any factor that reduces the volume of the cubital tunnel absolutely or relatively can cause compression of the ulnar nerve, common causes include:

　　1. Chronic injury, such as fractures of the proximal and distal humeral epicondyles and supracondylar fractures, as well as radial head fractures, can cause radial deviation or other deformities due to malunion, increasing the carrying angle and shortening the ulnar nerve relatively, thereby causing traction, compression, and friction on the ulnar nerve.

　　2. Rheumatoid arthritis or rheumatoid arthritis affecting the synovium of the elbow joint due to rheumatoid or rheumatoid lesions, causing it to proliferate and thicken, leading to elbow deformity and osteophyte proliferation in the late stage, thereby also causing a decrease in the volume of the cubital tunnel.

　　3. Masses such as ganglia and lipomas, but they are less common.

　　4. Congenital factors such as congenital radial deviation of the elbow, shallow ulnar groove leading to recurrent dislocation of the ulnar nerve, and Struthers弓形组织, etc.

　　5. Other long-term flexion of the elbow, compression caused by iatrogenic factors. 'Sleep palsy' caused by sleeping with the elbow in a pillow.

　　Secondly, pathogenesis

　　The cubital tunnel is a bony fibrous canal, through which the ulnar nerve and the ulnar collateral artery pass from the posterior aspect of the humerus to the flexor aspect of the forearm. The bottom of the cubital tunnel is the medial collateral ligament of the elbow, and the deep surface of the medial collateral ligament is the medial lip of the trochlea and the ulnar groove located posterior and below the medial epicondyle of the humerus. The top is the triangular arched ligament connecting the medial epicondyle of the humerus and the medial aspect of the olecranon, thus forming a bridge between the humeral head and the ulnar head of the ulnar flexor muscle. The size of the cubital tunnel varies with the flexion and extension of the elbow joint: when the elbow is extended, the arched ligament is relaxed, and the volume of the cubital tunnel increases. When the elbow is flexed to 90°, the arched ligament is tense, and the distance between the medial epicondyle of the humerus and the olecranon increases by 0.5cm for every 45° of flexion. Additionally, when the elbow is flexed with the 0.5cm widening, the prominence of the medial collateral ligament also reduces the volume of the cubital tunnel, making the ulnar nerve prone to compression. Some measurements show that the pressure inside the cubital tunnel when the elbow is straight is 0.93kPa, and when the elbow is flexed to 90°, it is 1.5 to 3.2kPa.

　　The ulnar nerve emits 2 to 3 fine branches to the elbow joint when passing through the elbow joint, within 4cm beyond the medial epicondyle of the humerus. The ulnar nerve emits a motor branch that innervates the ulnar flexor muscle of the wrist beyond the medial epicondyle of the humerus, usually with 2 branches, entering the deep surface of the muscle. The branch that innervates the deep flexor muscles of the ring and little fingers is slightly distal to the ulnar flexor muscle branch, entering the front of the muscle and innervating these two muscles.

　　It may be complicated with delayed onset ulnar neuritis. Delayed onset ulnar neuritis causes symptoms of ulnar nerve palsy, with a slow onset, initially manifested as numbness and pain in the ulnar side of the hand. In patients with a long course, complete sensory loss may occur, with weakened muscle strength of the muscles innervated by the ulnar nerve. Late stages may present with claw-like hand deformity, atrophy of the hypothenar muscle and interosseous muscles. A thickened ulnar nerve in the elbow may be palpable, and Tinel sign is positive.

　　1. Sensory abnormalities on the ulnar side of the back of the hand, hypothenar eminence, and the ulnar side of the ring finger occur first, usually manifested as numbness or tingling.

　　2. Secondary sensory abnormalities may appear after a certain period of time, with weakness of the little finger adduction and poor finger flexion and extension.

　　3. Examination reveals atrophy of the hypothenar muscle and interosseous muscles of the hand, as well as digital and ring fingers with claw-like deformities. The skin in the aforementioned area has reduced pain sensation, positive paper pinch test, and positive Tinel sign at the ulnar groove.

　　4. Electrophysiological examination shows a slowing of ulnar nerve conduction velocity below the elbow, and abnormal electromyography of the hypothenar muscle and interosseous muscles.

　　5. Basic disease manifestations include elbow varus, thickening and blackening with nodules at the ulnar groove. X-ray films show local displacement of bone fragments or abnormal ossification.

　　This disease is caused by direct trauma leading to compression of the ulnar nerve. Therefore, attention should be paid to lifestyle habits, and high-risk workers, such as construction workers and miners, are prone to injury, and they should protect themselves during work. Pay attention to rest and avoid fatigue, do not work in one position for a long time. Stay calm when facing things, and avoid emotional excitement leading to conflict and causing this disease. Secondly, early detection and early diagnosis are important.

　　1. Electromyography examination:Electromyography is helpful for patients with unclear location or diagnosis of ulnar nerve entrapment, which can manifest as a decrease in the conduction velocity of the ulnar nerve, an extension of the latency, and the appearance of spontaneous electrical potentials of the muscles innervated by the ulnar nerve.

　　2. X-ray film:It can be found that there are bony changes around the elbow joint, and it should be routinely applied to patients suspected or diagnosed with cubital tunnel syndrome.

　　3. Intervertebral foramen compression test.

　　4. Autonomic nerve function examination.

　　1. You can eat more vitamin B1-rich foods to supplement: milk and its products, animal liver and kidney, egg yolk, eel, carrot, mushroom, seaweed, celery, orange, tangerine, orange, etc.

　　2. Choose light, easy to digest, and nutritious food.

　　3. Eat more fresh fruits and vegetables, cold vegetables and fruits: such as winter melon, pear, banana, watermelon, you can appropriately increase animal liver, milk, egg yolk.

　　I. Treatment

　　1. Conservative treatment is suitable for patients in the early stage of the disease with mild symptoms. It can adjust the posture of the arm, prevent the elbow joint from being over-flexed for a long time, avoid pillow elbow sleep, and wear elbow guards. Non-steroidal anti-inflammatory analgesics can occasionally relieve pain and numbness, but it is not recommended to use corticosteroid hormones in the cubital tunnel.

　　2. Surgical treatment is suitable for patients who have been treated conservatively for 4-6 weeks without effect or have atrophy of the intrinsic muscles of the hand. The methods of surgery can be divided into two major categories: local decompression and nerve anterior implantation. Local decompression includes in-situ incision and decompression of the cubital tunnel and excision of the medial epicondyle, due to the disadvantages of anterior dislocation of the ulnar nerve, postoperative recurrence, and instability of the elbow joint, it is now rarely used. Ulnar nerve anterior implantation includes subcutaneous, intermuscular, and submuscular anterior implantation. Intermuscular anterior implantation is the most widely used due to fewer postoperative complications.

　　II. Prognosis

　　The treatment is effective after surgical treatment.