Congenital ball-socket anomaly

In medicine, a prosthesis (plural: prostheses; from Ancient Greek prosthesis, "addition, application, attachment") or prosthetic implant is an artificial device that replaces a missing body part, which may be lost through trauma, disease, or a condition present at birth (congenital disorder). Prostheses are intended to restore the normal functions of the missing body part. [Source: Wikipedia ]

May Cause
Tarsal fusion