Symbrachydactyly (or, atypical cleft hand) comes from the Greek for “fused small fingers.” It describes a condition that affects the central digits of the hand. The fingers involved may be fused and shortened to varying degrees. Joints may be non-functional or stiff. Various degrees of instability of joints may be present in the remaining fingers. Nails may or may not be present. The entire arm can sometimes be smaller than the normal side.
It is estimated that symbrachydactyly occurs 1 in 30,000 to 40,000 newborns. The majority of cases still have no known cause. Occasionally, it may be associated with other findings, such as in Poland syndrome or Mobius syndrome. As with other hand deformities, symbrachydactyly appears to occur between the fourth and sixth weeks of pregnancy, possibly corresponding to an interruption in blood supply to the hand.
Although the hand may not possess the appearance or functionality of a non-affected hand, the majority of patients possess excellent adaptation and use. Surgery is aimed mainly at correcting joint or tendon instability or to help improve hand strength, grip, and/or pinch. Tendon transfers (borrowing a tendon from another part of the hand or wrist) is recommended to help improve these functions. Joint fusion can stabilize a floppy joint near the tip of a finger. In addition, as the name suggests, symbrachydactyly has an element of syndactyly (or, webbed fingers). Separation of fused digits will also need to be performed similar to syndactyly reconstruction (see “Syndactyly” for further details). Finger bones can also be lengthened during adolescence using a distraction device. This is not recommend for all patients, but may improve appearance and possibly function in some select individuals. Other procedures may be required and are individualized. Depending on the severity of the condition, treatment can begin as early as 6 months of age. Often, as with other hand differences, a therapist will need to guide nonoperative aspects of treatment, including splinting, stretching, and maximizing hand function.