Congenital hypoplasia of the first ray of the hand: causes, symptoms, diagnosis, treatment

Congenital hypoplasia of the first ray of the hand is a developmental defect characterized by underdevelopment of the tendon-muscle and bone-articular apparatus of the finger of varying degrees of severity with progression of the defect in the teratological series of defects from the proximal end of the ray to the distal.

ICD-10 code

• Q71.8 Congenital hypoplasia of first ray of hand.

Classification of congenital hypoplasia of the first ray of the hand

The most common classification in the world is considered to be the Blauth classification of congenital hypoplasia of the first ray of the hand. Depending on the degree of expression of the defect, five degrees of this anomaly are distinguished.

• Grade I - slight decrease in the size of the first finger, hypoplasia of the abductor pollicis brevis and opponens pollicis.
• Grade II - the thumb is represented by all bone structures, but their sizes are reduced compared to the norm; narrowing of the first interdigital space, hypoplasia or aplasia of the superficial thenar muscles, instability of the metacarpophalangeal joint are noted.
• Grade III - the first interdigital space is narrowed, there is an anomaly in the development of the thenar muscles, as well as the long muscles of the thumb, the first metacarpal bone is hypoplastic up to the rudiment of the head in the distal part.
• Grade IV - "dangling finger".
• Grade V – aplasia of the first finger.

Indications for surgical treatment of congenital hypoplasia of the first ray of the hand include grade II-V deformities. In case of grade II hypoplasia, an operation to abduct and oppose the first finger is performed in combination with stabilization of the metacarpophalangeal joint of the thumb (capsuloplasty, arthrodesis). Limitation of bilateral grip of the hand after the intervention requires performing opposing plasty as a second stage. In cases where severe hypoplasia of the thenar muscles is detected intraoperatively, and in some cases also of the extensors of the first finger, the operation to abduct and oppose the thumb is combined with Blauth-Thompson tendon plasty. There are two methods for restoring the thumb in case of grade III-IV hypoplasia: pollicization operation and first ray reconstruction. In case of aplasia of the first ray of the hand, pollicization operation is performed.

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