Clinodactyly refers to the side-to-side curvature of a finger or toe. In most individuals, the degree of curvature is minimal and usually involves the small fingers. There is a hereditary element of finger curvature, especially when it involves the same finger on both hands. The basis for clinodactyly is that the middle bone in the finger is underdeveloped and, instead of being rectangular, it is trapezoidal. The growth plates are not parallel, causing one side to grow more than the other side.
In most cases, clinodactyly is harmless and does not need to be corrected. In a small number of patients, the curvature may be severe enough or worsen over time to interfere with adjacent digits. This is most noticeable when someone tries to flex his or her fingers into a fist. In these patients, surgery involves realigning the growth plates with an opening or closing wedge osteotomy.
Clinodactyly may occur as an isolated finding in a person who is entirely normal or it may be found in association with other congenital malformations and, sometimes, with developmental delay. It is a common component of Down syndrome (trisomy 21) and Klinefelter syndrome (XXY).