Congenital Hand Anomalies

Intro & Classification - Hand's First Drafts

• Embryology: Hand development spans 4th-8th weeks.
  • Limb bud appears (4th wk).
  • Apical Ectodermal Ridge (AER) for proximo-distal growth.
  • Zone of Polarizing Activity (ZPA) for radio-ulnar axis.
  • Hand plate forms (5th wk); digital rays separate via apoptosis (6th-8th wk).
• Classification (Modified Swanson/IFSSH):
  • I: Failure of Formation (Arrest; e.g., transverse, longitudinal - radial/ulnar clubhand)
  • II: Failure of Differentiation (Separation; e.g., syndactyly, camptodactyly, clinodactyly)
  • III: Duplication (Polydactyly; preaxial, postaxial, central)
  • IV: Overgrowth (Macrodactyly)
  • V: Undergrowth (Hypoplasia; e.g., brachydactyly)
  • VI: Congenital Constriction Band Syndrome (Amniotic band syndrome)
  • VII: Generalized Skeletal Abnormalities/Syndromes

⭐ Syndactyly is the most common congenital hand anomaly, most frequently involving the 3rd web space (middle-ring finger).

Formation Failures - Building Blocks Gone Astray

• Arrest in limb development; parts are absent or deficient.
• Transverse Arrests (Congenital Amputations):
  • Complete arrest of development beyond a point.
  • E.g., Acheiria (hand), Adactyly (digits).
  • Often unilateral; resembles amputation stump.
  • Cause: Vascular events, teratogens.

  ⭐ Most common congenital upper limb deficiency: Transverse arrest (below elbow).

• Longitudinal Arrests: Segmental absence along the longitudinal axis.
  • Radial Deficiency (Radial Clubhand):
    • Partial/complete absence of radius; hand deviates radially.
    • Thumb hypoplasia/aplasia frequent.
    • Syndromes: VACTERL, Holt-Oram, TAR.
  • Ulnar Deficiency (Ulnar Clubhand):
    • Partial/complete absence of ulna; ulnar deviation.
    • Rarer than radial deficiency.
  • Central Deficiency (Cleft Hand/Ectrodactyly):
    • Typical 'lobster claw' appearance; absent 3rd ray common.
    • Often AD inheritance.

Separation & Shape Issues - Fingers Fused & Funky

• Syndactyly: Most common hand anomaly; failure of interdigital apoptosis.

  • Types: Simple (skin), Complex (bone/nail), Complicated (e.g., Apert). 3rd web (Middle-Ring Finger) most common.
  • Surgery: Border digits (thumb/index, ring/little) at 6 months; others 18-24 months. Z-plasty, Full-Thickness Skin Grafts (FTSG). ⭐ > Apert syndrome: often complex syndactyly ("mitten hand").

• Clinodactyly: Radioulnar finger curve, usually 5th finger (radial deviation). Cause: Delta phalanx.

  • Assoc: Down syndrome.
  • Rx: Observation; osteotomy if >30° & functional issues.

• Camptodactyly: PIP joint flexion contracture, usually 5th finger.

  • Types: Infantile (often bilateral), Adolescent.
  • Rx: Splinting, stretching. Surgery (Flexor Digitorum Superficialis release) if refractory.

• Kirner's Deformity: Palmar/radial curve of 5th finger's distal phalanx.

  • Onset ~12 years, often bilateral.
  • Rx: Usually none; corrective osteotomy if symptomatic/severe progressive deformity.

Extra Parts & Odd Sizes - More or Mighty Digits

• Polydactyly (Extra Digits)
  • Presence of supernumerary digits.
  • Classification:
    • Preaxial (Radial/Thumb): Wassel Classification (Types I-VII) guides treatment. Most common is Type IV.
    • Central (Index, Middle, Ring fingers): Rarest form.
    • Postaxial (Ulnar/Little Finger): Most common overall. Simple excision for Type B (pedunculated).
  • Surgical timing: Typically 6-18 months.

![Postaxial polydactyly Type B in newborn hand and foot](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Orthopaedics_Hand_Surgery_Congenital_Hand_Anomalies/4f9b86d7-677b-4c95-a722-9ef0f8cddd34.png)

• Macrodactyly (Mighty Digits)
  • Non-hereditary congenital gigantism of digit(s); often unilateral.
  • Types: Static (proportional growth) vs. Progressive (disproportionate, rapid growth).
  • Often involves nerve territory (e.g., median nerve in macrodystrophia lipomatosa).
  • Treatment: Challenging; includes debulking, epiphysiodesis, ray amputation.
• Constriction Ring Syndrome (Amniotic Band Syndrome)
  • Cause: Intrauterine amniotic bands.
  • Features: Circumferential grooves, distal lymphedema/necrosis, acrosyndactyly (fusion of distal digits), intrauterine amputations. Patterson classification used.
  • Treatment: Surgical release of constricting bands (e.g., Z-plasty).

⭐ Wassel Type IV is the most common type of preaxial (thumb) polydactyly, representing a duplicated proximal phalanx with a common metacarpal head or a bifid metacarpal head for the two thumbs.

High‑Yield Points - ⚡ Biggest Takeaways

• Syndactyly is the most common congenital hand anomaly; surgical separation indicated.
• Polydactyly is second most common; postaxial (ulnar) more frequent than preaxial.
• Thumb hypoplasia often linked to Holt-Oram syndrome (cardiac) & VACTERL.
• Madelung deformity: Volar carpal subluxation from distal radial tilt.
• Kirner deformity: Palmar/radial bowing of little finger's distal phalanx.
• Camptodactyly: PIP joint flexion contracture, typically little finger.
• Clinodactyly: Coronal plane deviation of digit, often little finger.