summary Clinodactyly is a congenital condition of the hand, often associated with Down's syndrome, that is characterized by the abnormal curvature of a digit in the radioulnar plane. Diagnosis is made clinically. Treatment is usually observation in the majority of cases. Epidemiology Prevalence found in 25% of children with Down's syndrome and 3% of general population Etiology Pathoanatomy autosomal dominant inheritance middle phalanx of small finger most commonly affected Anatomy Anatomy of ligaments of the fingers Classification Clinodactyly Classification Type I Minor angulation with normal length (most common) Type II Minor angulation with short length Type III Significant angulation and delta phalanx (c-shaped epiphysis and longitudinal bracketed diaphysis) Presentation Physical exam function rarely significantly compromised daily activities can be affected if deformity reaches 30-40 degrees Imaging Radiographs C-shaped physis can result in a delta phalanx Treatment Nonoperative observation indications favored in most cases splinting is not indicated Operative phalanx opening wedge osteotomy +/- bone excision indications Type III (delta phalanx) when deformity (delta phalanx) encroaches digit space of neighboring short digit technique excision of extra bone