Definition: This deformity was first reported by Dr. Kirner in Germany in 1927, hence the name Kirner’sdeformity. There is no common name for it in Chinese, so the name is forced to be: hunchbacked finger deformity. Kirner’s deformity is characterized by progressive palmar and radial curvature of the distal phalanges of the fingers, with the deformity occurring in both palmar flexion and radial deviation (toward the thumb side), with palmar flexion predominating and the terminal finger showing the signature hooked hunchback deformity. The prevalence of Kirner’s deformity ranges from 0.15% to 0.25%, usually involving only the little finger and is twice as common in women as in men. With autosomal dominant inheritance and incomplete ectopic rates, purets can express the malformation in multiple fingers of both hands. Kirner’s malformation is sometimes only one of many symptoms of syndromes such as Silver, Turner and Down’s syndrome. Early-onset or congenital Kirner malformation is present at birth, has a family history, and the malformation does not progress with growth. Late onset Kirner’s deformity begins in late childhood or adolescence, with no family history. The deformity begins with swelling and discomfort on the dorsal Zhengzhou side of the distal phalanges of the little finger, and as the deformity progresses, the phalanges eventually set, with the distal phalanges of the fingers bending to the palmar and radial sides to form a stable pestle or beak-like appearance. The distal interphalangeal joint still has normal mobility. The etiology of Kirner deformity is unknown. It is generally thought to be related to an abnormality of the epiphyseal growth plate of the distal phalanx, but this abnormality is not due to trauma; asymmetrical growth of the epiphyseal plate or pulling of the injured epiphyseal plate by the flexor tendon leads to the final deformity, and it is also theorized that the abnormal position of the stop of the flexor tendon leads to excessive pulling of the developing phalanx. Vascular anomalies have also been proposed to be the cause of the deformity.