Kirner deformity

Kirner's Deformity is a congenital upper limb anomaly affecting the distal phalanx of the little finger. There is a progressive volar and radial angulation with time. This is different to the deviation of clinodactyly which only occurs in one radioulnar plane. Typically affecting young females in a bilateral distribution, most cases are sporadic but it can be inherited in an autosomal dominant manner with incomplete penetrance. It has been associated with Cornelia de Lange, Turner's and Down's syndromes.

The pathogenesis may be related to:

• abnormal growth of the physis of the distal phalanx
• a vascular growth abnormality
• abnormal flexor tendon pull on the distal phalanx

Clinically, there may be early swelling along the dorsum of the distal phalanx followed by mild discomfort. With growth, progressive angulation at the DIPJ ensues with a normal range of motion. Nail beaking may be apparent. There may be little loss of function and most patients are only concerned about appearance.

Radiography shows widening of the physeal growth plate and angulation of the distal phalanx.

Treatment is symptomatic and surgery is rarely indicated. Options include:

• early serial splintage may prevent progression
• obliteration of the physis to prevent progression eg by removing the dorsal part of the growth plate
• wedge osteotomies on the skeletal mature distal phalanx; several transverse opening volar osteotomies can be employed
• distraction lengthening