CLINODACTYLY

SHORT MIDDLE PHALANX OF FIFTH DIGIT

Clinodactyly is the curvature of a digit (medially or laterally) in a radio-ulnar plane. It is most commonly seen in the small finger followed in frequency by the triphalangeal thumb. The curvature of the tip of the digit towards the midline of the hand is due to a deformity of the middle phalanx. It is caused by shifting in the alignment of the articular surfaces of the proximal or distal interphalangeal joint away from its normal position (perpendicular to the long axis of the digit).
The two articular surfaces of the phalanx are not parallel.

ETIOLOGY

• Sporadic in normal fetuses.
• Dominant trait with variable expressivities.
• Associated with syndromes.

ULTRASOUND

• Minor angulation with normal length (very common).

• Minor angulation with short phalanx.
• 25% of Down syndrome.
• 3% of normal infants.
• Marked angulation - delta phalanx (this results from an abnormal epiphysis which extends from one end of the normal proximal epiphysis around and along the short side. A "J-shaped" epiphysis" sometimes continuing to form an abnormal distal epiphysis to the bone creating a "C-shaped epiphysis" or "longitudinally bracketed epiphysis".

Clinodactyly in Down syndrome
Down syndrome – clinodactyly + shortened middle phalanx (MP) of the 5^th digit

ASSOCIATED ANOMALIES AND SYNDROMES

• Trisomy 18 and Trisomy 21.
• Holt-Oram syndrome.
• Smith-Lemli-Opitz syndrome type II.
• Russell-Silver syndrome.
• Larsen's syndrome.
• Cornelia De Lange Syndrome.
• Orodigito-Facial syndrome.