Ulnar dimelia

Ulnar dimelia, showing clenched position

X-ray of 2-month-old female child with ulnar dimelia

Ulnar dimelia or mirror hand syndrome is a rare congenital disorder characterized by the duplication of the ulna bone in the forearm, leading to the absence of the radius bone, and the presence of extra fingers in a mirror image arrangement. This condition results in significant abnormalities in the forearm and hand, affecting the functionality and appearance of the affected limb. Ulnar dimelia is a type of polydactyly, which refers to the condition of having more than the usual number of fingers or toes.

Etiology

The exact cause of ulnar dimelia is not well understood, but it is believed to occur due to genetic mutations or environmental factors that affect limb development during the early stages of embryogenesis. The disruption in the normal signaling pathways that dictate limb patterning and growth can lead to the duplication of the ulna and the anomalies associated with ulnar dimelia.

Clinical Features

Individuals with ulnar dimelia typically present with a range of physical manifestations including:

• Duplication of the ulna bone
• Absence of the radius bone
• Seven or eight fingers on the affected hand, often in a mirror image formation
• Limited or absent thumb
• Possible fusion of some fingers (syndactyly)
• Reduced mobility and functionality of the affected forearm and hand

Diagnosis

Diagnosis of ulnar dimelia is primarily based on physical examination and imaging studies. X-rays of the affected limb can reveal the characteristic bone abnormalities, including the duplication of the ulna and absence of the radius. In some cases, advanced imaging techniques such as MRI (Magnetic Resonance Imaging) may be utilized to assess the extent of the condition and plan for surgical intervention.

Treatment

The treatment of ulnar dimelia focuses on improving the functionality and appearance of the affected limb. Surgical intervention is often required and may include procedures to remove extra fingers, reconstruct the thumb, and correct any other deformities. Physical therapy is also an important component of treatment, aiming to enhance limb mobility and strength.

Prognosis

The prognosis for individuals with ulnar dimelia varies depending on the severity of the condition and the success of surgical interventions. With appropriate treatment, most individuals can achieve improved hand function and appearance. However, some degree of limitation in the affected limb may persist.

See Also

• Polydactyly
• Syndactyly
• Congenital limb deformities