Limb inequality refers to single or multiple bone shortening or overgrowth resulting in bilateral limb disparity. There are many causes of limb inequality, some congenital and some arising gradually during the growth process after birth. Limb inequality in the upper extremities is usually not easily detected, while in the lower extremities it is easily detected due to the possibility of abnormal gait and functional scoliosis. The physician will determine if the limbs are the same length by taking a history and physical examination, using tools such as a dipstick to measure the length of the limb or a board of known thickness to determine if the limbs are the same length, and then X-rays to accurately determine the length of the limb and the cause of the limb inequality. The common causes of limb inequality are mainly congenital and acquired: 1, congenital musculoskeletal developmental abnormalities This part of the patient’s symptoms vary in severity, most of them are related to the child’s own genetic mutations, mild patients only show limb length and thickness, but the function of the limb is not affected, the representative disease is hemiplegia or hemiplegic dysplasia. In patients with severe symptoms, in addition to limb shortening, there is also significant limb dysplasia, thin lower limbs, poor muscle strength, and abnormal toe development. The skeletal deformities may be evident when x-ray films are taken. These symptoms may also be local manifestations of the generalized syndrome. 2, congenital hip dislocation is one of the most common congenital diseases in children’s orthopedics, the main symptom of which is both lower limbs are not equal in length, the joint dislocation of one limb shortening, due to limb shortening children walking will appear limp, however, this limb can not grow is a functional, lower limb shortening is caused by joint dislocation. 3. Acquired limb inequality Fractures Fractures may cause limb overgrowth resulting in limb lengthening on the fracture side, while fractures may also cause limb shortening due to abnormal healing or damage to bone growth cells resulting in bone growth restriction. In tumor and inflammatory lesions, the bones on the affected side may slow down due to tumor or inflammation, while individual patients may also experience overgrowth due to stimulation of the bones by tumor or inflammatory cells. Neuromuscular disorders, which can produce disuse limb atrophy and slowed skeletal growth eventually leading to limb shortening. Epiphyseal lesions, the growth center or growth plate of the bones in children, is a unique structure for children and can be affected by various diseases including tumors, inflammation, and fractures involving the epiphysis, such as osteomyelitis. Aseptic necrosis of the femoral head is a typical epiphyseal lesion that affects the growth of the proximal femoral segment due to necrosis of the femoral epiphysis, which eventually results in a degree of limb inequality. Tumors growing near the epiphysis also tend to cause abnormal limb growth, such as endogenous chondroma and osteochondroma. 1.Treatment of upper limb unequal length The impact of upper limb unequal length on patients is relatively small. Generally, the upper limb length is obviously shortened, with a difference of more than 6 cm; or it has obvious impact on patients’ daily life or produces obvious appearance deformity, then only treatment is needed. 2.Treatment of unequal length of lower limbs The doctor will decide whether treatment is needed according to your child’s symptoms, cause and age after examination. First of all, if the lower limb is unequal due to congenital hip dislocation, surgery is needed for the original cause, i.e. hip dislocation. If the unequal length of the lower extremity is more than 2.5 cm, intervention is needed because the unequal length of the lower extremity may lead to functional scoliosis and lesions of the hip, knee and ankle joints. 3.What treatments are available? The goal of treatment for limb inequality is limb equivalence. Your doctor will make a reasonable treatment plan based on the cause of your child’s condition, the severity of symptoms, as well as the cost and duration of treatment and your and your child’s acceptance of treatment. Because children are in a growth phase, the goal of treatment is not only to compensate for differences now, but to correct differences that may occur later. Since everyone grows at a different rate, it may not be urgent to treat your child in order to be able to more correctly estimate the eventual limb discrepancy, but rather to observe your child for one to two years and finalize a treatment plan depending on the growth rate of your child’s bones. Conservative treatment For limb discrepancies present at birth, some orthopedic surgery is required if the skeleton is abnormal. If there is no skeletal abnormality, simple limb inequality does not require special treatment in infancy because the child is not yet walking, and can be treated in early childhood with the use of supplementary height shoes. Some congenital limb inequalities can be treated with special calculations to estimate the difference in final limb length that may occur as the child’s skeleton matures. For patients with milder symptoms with limb inequalities of about 2 cm, they can also be treated with supplemental height inserts or orthopedic shoes. Surgical treatment Inequality caused by neurological disorders can be treated by tendon lengthening or other soft tissue surgery. Other causes of limb inequality can be evaluated by a physician who will determine whether to treat the limb with surgery. The surgical treatment of limb inequality due to abnormal limb growth consists of two main approaches: 1) shortening of the long limb and 2) lengthening of the short limb. The former can be achieved by permanent epiphyseal block or temporary epiphyseal block to stop or retard the growth of the long-side limb. The latter limb lengthening is mainly performed by external fixation brace. Permanent epiphyseal block: early fusion of the epiphysis of the long-side limb so that it no longer grows. It is more suitable for children with limb hypertrophy. Its main complication is underestimation leading to poor results. Temporary epiphyseal block: A metal internal fixation (plate or riding staple) fixed on both sides of the epiphysis is used to limit the growth of the epiphysis and achieve a delay in bone growth. The fixation can be removed when the limb is of equal length. Since the growth of the epiphysis is not destroyed, a certain degree of recurrence may occur after the fixation is removed, but since the operation is less invasive, multiple operations can be performed on the same site. Partial osteotomy: mainly suitable for adolescents whose bone growth has stopped, if the difference in limb length is not significant, the bone on the long side can be partially removed to achieve equal limb length. Limb lengthening: The shortened limb is gradually lengthened mainly by external fixation instruments, and the surgical effect of limb equal length is not achieved immediately after surgery. Generally lengthening 1 mm a day, lengthening 1 cm external fixation stent need about 40 days to remove. The operation is relatively complex, the treatment time is long, the complications are high, and there are high requirements for parents to cooperate with the treatment.