Thumb Hypoplasia - Flashcards

Study Notes

Thumb Hypoplasia - Overview

Thumb hypoplasia is a congenital condition involving the underdevelopment (hypoplasia) or absence (aplasia) of the thumb.
It is classified under the spectrum of radial clubhand but regarded as a distinct condition.
Characterized by a short, hypoplastic thumb which is critical for grip and hand function.
Treatment typically involves reconstruction or pollicisation to create a functional thumb from an existing finger.

Associations with Other Conditions

Associated with several syndromes similar to radial clubhand:
- VACTERL: A constellation of vertebral, anal, cardiac, tracheo-oesophageal, renal, and limb anomalies.
- Holt-Oram Syndrome: Includes congenital heart defects like atrial and ventricular septal defects.
- Fanconi Anemia: Aplastic anemia with normal blood counts at birth that decrease in early childhood; requires bone marrow transplantation.
- TAR syndrome: Characterized by thrombocytopenia and absence of the radius, with platelet counts normalizing over time.

Clinical Features

Presents with a short, hypoplastic, or adducted thumb; less commonly an abducted thumb.
Associated with first web space contracture and stiffness in the interphalangeal joint (IPJ).
Metacarpo-phalangeal joint (MCPJ) instability due to absent collateral ligaments may occur.
Potential absence of thenar musculature.

Classification

Blauth classification provides guidance for management and treatment strategies.

Management Strategies

Focuses on creating a functional thumb through reconstruction or pollicisation.
Type 1 (functional thumb) is treated non-operatively.
Types 2 and 3A are eligible for thumb reconstruction.
For Types 3B, 4, and 5, pollicisation is indicated, especially with CMCJ instability.
CMCJ insufficiency may necessitate amputation and subsequent pollicisation.

Thumb Reconstruction Techniques

Nick Smith Technique:
- Includes deepening of the first web space and MCPJ stabilization.
- Utilizes opponensplasty using either ADM or FDS through a subcutaneous tunnel.
- Techniques aim to prevent complications, using specific sutures and tendon transfers.

Huber Opponensplasty

Reserved for cases of high median nerve palsy or congenital deficiencies.
ADM musculature provides cosmetic fullness but limited strength compared to normal abductor pollicis brevis (APB).
Possible combination with flexor digitorum superficialis (FDS) transfer for enhanced function.

Tonkin Thumb Reconstruction

Involves a ulnar-sided incision over the hypothenar region.
Careful harvesting of ADM, ensuring preservation of other muscles such as the flexor digiti minimi.
Technique includes creating a subcutaneous tunnel and may involve separate incisions for stability.

Pollicisation Procedure

Transforms the index finger into a thumb post amputation of the remaining thumb.
Involves bony reduction to recreate metacarpal and phalanges.
Local skin flaps used to reconstruct the first web space, with preservation of nerve bundles and tendon transfers for thumb function.
Specific tendon transfers include EDC to APL, EIP to EPL, and interosseous muscles to improve thumb function.

Description

Explore key concepts of Thumb Hypoplasia through this flashcard quiz. Learn about its definition, characteristics, and treatment options. Ideal for students and healthcare professionals interested in congenital hand conditions.