Osteomalacia major is an endemic deforming osteoarthropathy with cartilage necrosis as the main change. It is also called dwarf disease and abacus disease in China, and now the international common name of this disease is Caschin-Beck disease. The disease is mainly distributed abroad in eastern Siberia and northern Korea, and has a large distribution in China, mainly occurring in farmers who feed on locally produced corn and wheat in the disease area, especially poor farmers.
The disease mainly affects growing children and adolescents, and new cases among adults are rare. Children generally start to develop the disease at the age of 7 to 8 years, and the onset can be earlier in heavily affected areas. There is no significant difference in the incidence between males and females. Chinese, Manchu, Hui, Mongolian, Korean, Tibetan, and Daur ethnic groups, as well as Russians and Japanese living in the disease area can be affected, and no racial susceptibility can be observed. More than two patients are common in the same family living in the disease area for a long time. This may be due to equal exposure to the causative factors under the same living conditions and does not prove the involvement of genetic factors.
The cause of the disease is unknown, and there are three main etiological theories.
① Biogeochemical theory: It is believed that the disease is caused by an excess, deficiency or imbalance of one or several elements. In the early stage, it was thought to be related to low calcium and high strontium and barium in water and soil. Later, it was found that the disease may be caused by excessive phosphorus and manganese in the water and soil and in the main and secondary food. At present, it is mostly believed that low selenium is only a condition factor for the onset of the disease.
②Fungal toxin theory: It is believed that the cereals in the disease area are contaminated with some kind of Fusarium and form heat-resistant toxic substances, and the residents get sick from eating food containing this kind of toxin.
③ organic poisoning: it is believed that the disease is caused by the contamination of drinking water with humus in the disease area. In recent years, some scholars believe that low selenium, fungal toxins and organic matter in drinking water may be intrinsically linked to the development of the disease. That is, the common result of grain contaminated by fungi and drinking water contaminated by organic matter.
The disease mainly affects children and adolescents during the period of skeletal growth and development, manifesting as symmetrical pain, deformation, thickening of the joints of the limbs, limitation of flexion and extension activities and muscle atrophy of the limbs. The disease progresses slowly without inflammatory reaction. Those with severe disorders of skeletal development may develop short and thick hands and feet, short stature, and difficulty in joint movement, resulting in disability.
1.Clinical manifestations and diagnosis
(1) Early manifestations Before the joints become obviously large and short fingers (toes) deformity appears, the early symptoms and signs are mostly lacking in characteristics. According to a large number of surveys and follow-up observations, the following manifestations deserve attention.
Joint pain: It is often multiple and symmetrical, often appearing first in the finger joints with high activity and the knee and ankle joints with high weight-bearing. Patients feel swelling, soreness, or “crepitus” pain.
Flexion of the uncinate finger: The final knuckle of the 2nd, 3rd and 4th finger is bent toward the palm, often greater than 15º. This is the earliest sign of the disease and has some significance for early diagnosis in the disease area. However, a small number of children in non-diseased areas may also have a lesser degree (less than 15º) of end-joint bending; the disease may also occur in adolescents without end-joint bending in diseased areas. The curvature of the terminal phalanges often coexists with the crookedness of the fingers. Crookedness is more common in the index finger, followed by the middle finger and ring finger.
Bowed fingers: The fingers are bowed and flexed to the palm side.
Condensed knuckle thickening: usually occurs in the middle knuckle.
(2) Manifestations after progression of the disease After the progression of the disease, in addition to early manifestations such as joint pain that continue to worsen, the following signs and symptoms mainly appear.
Thickening of the joints: The most common is multiple, symmetrical thickening of the interphalangeal joints, often appearing first in the first interphalangeal joint of the second, third and fourth fingers. The thickening of the right finger joints is generally more pronounced than that of the left hand, and the thickening is more severe in joints that have been mechanically injured or in women with thimbles.
Impaired joint movement: In the hand, it is characterized by stiffness of the fist in the morning, tightness of the fist, inability of the fingertips to touch the transverse palm line, and inability to extend the clenched fist quickly. Elbow joint flexion and extension are limited, showing flexion and contracture. When the shoulder joint is involved, the patient cannot feel the opposite ear from the back of the head with his hand, or even cannot wash his forehead with his face. The knee joint is inwardly or outwardly rotated, and the knee joint is in the shape of a leg with scissors.
Due to the deformation of the knee and hip joints, the patient has difficulty squatting, compensatory anterior convexity of the lumbar spine, posterior convexity of the hips, small stride length, swaying or limping, “duck walking gait”, and impaired plantar flexion and dorsiflexion of the ankle joint. Patients’ pain and mobility disorders are often worse after rest or in the morning, and lessened with some activity. Many patients need to “walk” on the edge of the bed after waking up in the morning before they can take a step.
Joint rubbing sounds: from small twanging sounds to rough rubbing sounds. It is caused by unsmooth joint surfaces and the proliferation and loss of synovial hairs in the joint capsule.
Articular free bodies: They can originate from either exfoliated articular cartilage fragments or from the shedding of proliferating synovial villi, the latter being mostly tiny rice-grain bodies. The free bodies may get stuck in the joint cavity and cause severe pain due to joint locking; the pain is relieved by loosening the free bodies with joint movement.
Skeletal muscle atrophy: Atrophy of the muscles of the extremities, especially the flexor muscles of the lower legs and forearms, is common in this disease, sometimes even before there are significant changes in the joints. The atrophy is more severe in the later stages of the disease due to pain and restricted joint movement, with more disuse factors involved.
Short finger (toe) deformity: the development of the knuckles is shorter than normal, and the hands are small and square. Or because the development of each finger (toe) different degree of disorder, its length lost the normal proportional relationship between each other.
Short limb deformity and short stature: The degree of developmental disorders of each tubular bone is often unequal. In some patients, the growth of radius stops at an early stage, the ulna is relatively long, the ulnar styloid process is displaced downward to the main dorsal side, and the hand is tilted to the radial side, resulting in Badrone deformity. The patient’s limbs are disproportionate to the head and trunk, generally the upper arm is significantly shorter than the forearm, the lower leg is significantly shorter than the thigh, and the trunk is close to normal.
2.Auxiliary examination
(1)X-ray typing
A epiphyseal type: The epiphysis is mainly changed, including thinning, blurring, interruption and disappearance of the temporary calcification zone, depression and sclerosis of the skeletal end. The epiphyseal type occurs in preschool and school-age children, reflecting secondary changes after cartilage necrosis of the epiphyseal plate, representing earlier damage in large osteoarthrosis, and clinical symptoms are mostly negative or very mild. The x-ray changes of the epiphyseal type can be seen in children in non-diseased areas, except for very pronounced sclerosis, which is less common in children in non-diseased areas. Therefore, it is not advisable to diagnose the disease on the basis of certain points of epiphyseal X-ray changes alone if no typical case of degree I or higher is found in the same area.
B epiphyseal type: In addition to the above changes in the epiphysis, there are also changes in the epiphysis, such as the epiphysis is often cone-shaped or otherwise deformed and embedded in a depressed epiphysis. This type occurs mostly in school age and adolescence, reflecting total necrosis of a part of the epiphyseal plate cartilage, with simultaneous growth disturbance and bone quality changes on the epiphyseal and epiphyseal nuclei sides, and localized early penetration of the epiphyseal plate into the bone. This is a further development of the epiphyseal type.
C-epiphyseal type: The bone ends are mainly changed, including vague irregularity, thinning, interruption, depression and deformation, sclerosis, and even fragmentation of the bony articular surface. It mostly occurs in school-age children to post-adolescent age group, reflecting the bone changes secondary to deep necrosis of articular cartilage. The changes in the bony end develop slowly and are more often combined with other joint damage. The diagnostic significance of the changes in the bone ends is more important and specific than the changes in the epiphysis.
D osteoarticular type: seen after epiphyseal closure and loss of epiphyseal plate cartilage, including severe destruction of the osteoarticular surface, concavity, hyperplasia and sclerosis, bone spur formation, bone fragmentation, cystic changes, and coarse deformity of the bone ends. Multiple joints are often involved, and the x-ray findings resemble degenerative (proliferative) arthropathy, which is an advanced manifestation of the disease.
(2) Laboratory tests related to bone and cartilage
A Plasma alkaline phosphatase (ALP) activity is elevated, especially in children with large osteoarthrosis who have typical changes on X-ray compared to both diseased healthy controls and non-diseased healthy controls. In the absence of significant liver and kidney damage, ALP was predominantly skeletal in origin, reflecting active myogenic cell function.
Hydroxylysine was significantly higher in B urine and rose with the aggravation of the disease as reflected by X-rays. Hydroxyproline, which is also a collagen breakdown product, changes less regularly. Sometimes there is a tendency for urinary hydroxyproline to increase in areas of active severe disease, while others report the opposite.
The excretion of chondroitin sulfate (Chs) in C urine is elevated, reflecting increased breakdown of the cartilage matrix. the degree of sulfation of Chs is reduced, and the electrophoretic mobility of Chs in the patient’s urine is significantly larger as detected by cellulose acetate film electrophoresis, indicating that the molecular weight of Chs has become smaller.
3.Treatment
The focus of treatment for this disease is prevention, and its incidence can be reduced by improving water quality, adjusting diet, and supplementing inorganic salts. Strengthening the storage and handling of grain in infected areas, or changing the grain in infected areas to be brought in from outside, can significantly reduce the disease.
For early stage patients, the application of sodium selenite, vitamin E, chondroitin sulfate and other drugs have the effect of stopping the progress of the lesions. At the same time acupuncture physiotherapy and application of corresponding allopathic drugs also have a certain effect.
For patients with severe joint deformity, joint contracture or sometimes joint interlocking, orthopedic surgery can be performed to remove the joint free body, clean up the inside of the joint and correct the deformity. Good results can often be obtained.