Finger hyperphalangy Hyperphalangy of the 2nd finger Hyperphalangy of index finger UMLS:C4072907 An accessory phalanx of the index (second) finger that is arranged linearly with the other phalanges. Hyperphalangy of the index finger results from an accessory ossification center at the metacarpophalangeal joint, resulting in radial deviation of the index finger. Note that this term refers only to this type of hyperphalangy.