Congenital absence of the ulna

　　The cause of the disease is due to the inhibition of the growth of the second, third, and fourth rays in addition to the main trunk of the limb bud in the embryo. Complete absence of the ulna is very rare, while partial absence is more common. Women are affected by estrogen and progesterone during pregnancy, plus the influence of environmental, dietary, and mental factors, which may lead to incomplete development of the fetus and cause maldevelopment or absence of the ulna in children.

　　Due to the absence of the ulna, the weight of the upper limb is only supported by the radius, which increases the pressure on the radius and is prone to fractures. There is obvious swelling and tenderness in the wrist, and the movement of the hand and wrist is limited. It may cause median nerve injury: delayed rupture of the extensor pollicis longus tendon; non-union of fractures, etc. Infection may also occur, mainly related to the long exposure time of the wound after injury, incomplete debridement, and severe soft tissue injury.

　　This condition is usually unilateral, with the right side being more common. Male patients are more than female patients. The children have the thumb and index finger, with good activity function, but the ulnar side is absent. The affected forearm is thin, short, and inclined towards the ulnar side, with the radial head dislocation, limited rotation function of the forearm, but the wrist and elbow joints function well. The patients may also have the absence of wrist bones, commonly the navicular bone, hamate bone, trapezium bone, and capitate bone. Sometimes the fourth and fifth metacarpal bones may also be absent. The radius bows outward, becoming more obvious with the growth of the child. About 20% of the children have syndactyly. Other associated deformities include the absence of the fibula, clubfoot, and spina bifida, etc.

　　1. Pay attention to daily living habits, early detection and early treatment, eat more fresh fruits and vegetables, such as figs, lichee, walnuts, loofah, olives, almonds, etc.
　　2. During pregnancy, the mother should pay attention to her own nutritional status, strengthen nutrition, and do prenatal examinations on time to detect early.
　　3. Maintain a cheerful spirit, avoid depression or excessive tension and fatigue, and adhere to eating low-fat foods in daily life, such as lean meat and low-fat dairy products.

　　On the X-ray film, the ulna is only a thin, long cartilaginous fibrous shadow, shorter than the radius, radial head dislocation, normal curvature of the radius is increased, bulging outward, the wrist掌尺侧列骨 may disappear or fuse into one.

　　1. Foods that are good for congenital ulnar hypoplasia: eat more fresh fruits and vegetables, such as figs, lichee, walnuts, loofah, Portulaca oleracea, soy sauce, olives, almonds, luffa, etc.

　　2. It is best not to eat certain foods for congenital ulnar hypoplasia: drink less alcohol and coffee, tea and other beverages, avoid passive smoking, eat less milk, goat milk and other dairy products and peanuts, chocolate, millet, cheese, sugar and other foods containing tyrosine, phenylalanine and tryptophan, as they can produce prostaglandins, leukotrienes, tyrosine kinase autoantibodies, and anti-milk IgE antibodies that can cause allergic reactions and exacerbate, recur, or worsen arthritis.

　　If the forearm is stable and has pronation and supination functions, surgical treatment may not be necessary; otherwise, surgical treatment should be performed. The surgical method is the 'forearm monobone surgery' to fuse the distal end of the radius with the superior end of the ulna to maintain the carpal and humeroulnar joints. In this way, the ulna and radius become one, the bones can still grow, the muscles of the forearm are stronger, the thumb movement is not affected, but the rotation function of the forearm is lost. Therefore, the forearm should be placed in the median position (right side) or 15° supination position (left side) during the operation to maximize the function of the hand. Attention should be paid during the operation that the periosteum should be removed together with the proximal end of the radius, otherwise a new radial proximal bone structure will be formed.