Congenital Hand Anomalies

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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 Swanson Classification of Congenital Hand Anomalies

⭐ 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. Classification of Congenital Hand Anomalies

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.

Practice Questions: Congenital Hand Anomalies

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