Cubital tunnel syndrome is a condition in which the ulnar nerve is trapped in the elbow, a condition first reported by Osborne in 1957 and called delayed ulnar neuritis, and then by Feined and Stratford in 1958. The ulnar canal is located behind the ulnar aspect of the elbow joint and the ulnar nerve passes through this canal. When the elbow is fractured, dislocated, a small piece of avulsion, congenital or acquired elbow valgus, or a tumor occurs in the elbow canal, the ulnar nerve can be compressed and a series of symptoms can result. Elbow canal syndrome When the ulnar nerve is compressed, there is numbness, pain, and decreased or absent sensation in the little finger, ring finger, and ulnar side of the back of the hand. The small muscles of the hand innervated by the ulnar nerve are atrophied, resulting in “claw-shaped hand” (the little finger and ring finger cannot be straightened), the thumb cannot be placed against the palm, the thumb and index finger are weak against each other, and the fingers cannot be separated and brought together, etc. As a result, writing, embroidery, knitting, and playing the piano are all hindered. For the first occurrence and mild symptoms, neurotrophic drugs (such as vitamin B1, etc.), intra-elbow injection of hydrocortisone acetate or confirmatory pneumonia canal can be used first. If symptoms are severe and non-surgical treatment is ineffective, surgical treatment can be considered: elbow canal dissection and ulnar nerve decompression, or ulnar nerve anterior surgery. The term “elbow canal syndrome” was first introduced by Feindel and Stratford and is also known in the literature as “traumatic ulnar neuritis of the elbow”, “delayed nerve palsy of the elbow”, and “chronic nerve palsy of the elbow”. “chronic ulnar nerve injury of the elbow”, etc. It refers to the symptoms of nerve injury caused by compression of the ulnar nerve at the ulnar nerve groove of the elbow. Any factor that disrupts the structure of the elbow canal and compresses, strains or rubs the nerve can cause it. Causes Any factors that reduce the volume of the elbow canal absolutely or relatively can cause the ulnar nerve compression, the common causes are: 1, chronic injury Fractures of the internal and external humeral condyles and supracondylar fractures and fractures of the radial head can produce elbow valgus or other deformities due to deformity healing, so that the carrying angle increases and the ulnar nerve is relatively shortened, so that the ulnar nerve is pulled, compressed and rubbed. Rheumatic or rheumatoid arthritis of the elbow joint Rheumatic or rheumatoid lesions invade the synovial membrane of the elbow joint, making it hypertrophic and thickening, causing deformation of the elbow joint and hyperplasia of the bone in the late stage, which can also cause a decrease in the volume of the elbow canal. 3, masses such as tendon sheath cysts lipoma, but less common. 4.Congenital factors such as congenital elbow valgus, repeated dislocation of ulnar nerve due to shallow ulnar nerve sulcus, Struthers bowing tissue, etc. 5.Other long-term work with elbow flexion, medical factors caused by the jamming. Sleep palsy” caused by occipital elbow sleep. Pathology The elbow canal is a bony fibrous canal through which the ulnar nerve with the ulnar collateral artery passes from the back of the humerus to the flexor side of the forearm. The base of the elbow canal is the medial elbow ligament, and the deep surface of the medial elbow ligament is the medial lip of the talus and the ulnar nerve groove below the medial epicondyle of the humerus; the top is the triangular arch ligament that connects the medial epicondyle of the humerus to the medial side of the hawk, and thus the arch ligament bridges between the humeral head of the ulnar carpal flexor and the ulnar head. The size of the elbow canal varies with the flexion and extension of the elbow joint: when the elbow is extended, the arch ligament is relaxed and the volume of the elbow canal becomes larger; when the elbow is flexed to 90°, the arch ligament is tense, and the distance between the medial humeral epicondyle and the ulnar eminence widens by 0.5 cm at every 45° of flexion; in addition, when the elbow is flexed under a widened state of 0.5 cm, the medial elbow ligament bulges to reduce the volume of the elbow canal, thus making the ulnar nerve vulnerable to compression. It has been measured that the pressure in the elbow canal is 0,93kPa when the elbow is straight and 1,5-3,2kPa when the elbow is flexed to 90°. The ulnar nerve sends 2-3 fine branches to the elbow joint when it passes through the elbow joint; within 4cm far from the medial epicondyle of the humerus, the ulnar nerve sends out motor branches innervating the ulnar carpal flexors, which generally have 2 branches, and they enter from the deep side of the muscle. The branches that innervate the deep flexors of the ring and little finger are slightly distal to the ulnar carpal flexor branch, entering from the front of the muscle and innervating these two muscles. Symptoms Clinical manifestations: Most commonly seen in middle-aged adults, especially in elbow flexors such as keyboard operators, instrumentalists, throwers, and occipital elbow sleepers. Patients with elbow canal syndrome may present with pain and a range of symptoms of impaired ulnar nerve function, depending on the severity and duration of ulnar nerve entrapment. The pain is located on the medial side of the elbow and may also radiate to the ring finger and little finger or to the medial side of the upper arm, and is sore or tingling in nature. Sensory symptoms first include tingling and burning sensation in the ring finger and little finger, followed by hyperalgesia and eventually loss of sensation. Motor symptoms include inflexible hand movements and weakness in grasping, atrophy of the intrinsic hand muscles and the lesser interphalangeal muscles, forming claw-shaped hands. On examination, pressure pain can be seen in the medial epicondyle of the humerus or behind it, and the Tinel’s sign at the ulnar nerve sulcus is positive, which is manifested by pain radiating to the ring finger and little finger by gently tapping the ulnar nerve 2 cm above and below the elbow canal. In some patients, anterior subluxation of the ulnar nerve can be felt when the elbow is flexed, but not all patients with anterior subluxation of the ulnar nerve have symptoms. Diminished or absent distance discrimination between the two points is usually the earliest manifestation. As the disease progresses, grasping and pinching weakness, reduced paper clamping force, atrophy of the interosseous and interosseous muscles, and claw-shaped hands may develop. Complications: Late onset ulnar neuritis can be complicated. Diagnosis: Based on the history, clinical signs and symptoms, positive Tinel’s sign, electromyography and radiographs, the diagnosis can be established. Differential diagnosis: There are many diseases that need to be differentiated from elbow canal syndrome, including ulnar nerve entrapment in other areas, systemic diseases and granuloma-like diseases, such as cervical spondylosis (nerve root type), thoracic outlet syndrome, diabetes mellitus, leprosy and elbow tuberculosis, etc. 1, cervical spondylosis (nerve root type): low cervical nerve root entrapment is very easy to be confused with this disease, but the pain and numbness of cervical spondylosis are mainly in the back of the neck and shoulder, and the pain radiates to the inner side of the upper arm and forearm, and the intervertebral foramen squeeze test can mostly induce pain. In addition, changes such as narrowing of the corresponding intervertebral space and osteophytes can be seen on cervical spine X-ray and CT film. 2.Guyon’s canal syndrome: It is caused by the compression of the palmar branch of the ulnar nerve in the Guyon’s canal at the wrist, which is manifested by the atrophy of the interosseous muscle and interosseous muscle and claw-shaped hand, but the muscle branch of the short extensor muscle of the little finger is mostly issued in the proximal side of Guyon’s canal, so the function is mostly normal, and the superficial branch of the palmar branch of the ulnar nerve is not involved in some patients without hand sensory disorder. 3, thoracic outlet syndrome has been described before. 4, leprosy The ulnar nerve is mostly involved, the ulnar nerve is abnormally thick, and there is no sweating in the hand sensory disorder area. Examination 1, electromyography: electromyography is helpful for patients whose specific site of ulnar nerve entrapment is not determined or the diagnosis is unclear, and it can be shown that the conduction velocity of the ulnar nerve is slowed down and the latency is prolonged, and the muscles innervated by the ulnar nerve have the appearance of spontaneous potentials of loss of nerve. 2.X-ray: Bony changes around the elbow joint can be found. It should be routinely applied to patients with suspected or diagnosed elbow canal syndrome.