Tendon Injuries

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Tendon Anatomy & Healing - Cable Care 101

  • Anatomy:
    • Composition: Primarily Type I collagen (~95%), tenocytes (specialized fibroblasts), elastin, proteoglycans.
    • Structure: Fibrils → Fibers → Fascicles → Tendon. Covered by Epitenon (outer, vascular layer) & Endotenon (inner, surrounds fascicles).
    • Blood Supply:
      • Intrinsic: Myotendinous & osteotendinous junctions.
      • Extrinsic: Vincula (long & short for flexors), paratenon/mesotenon (for extensors). Tendon anatomy and collagen hierarchy
  • Healing Phases (Approximate):
      1. Inflammatory (0-5 days): Hematoma formation, migration of inflammatory cells (neutrophils, macrophages). Weakest phase; defect filled by clot.
      1. Proliferative/Reparative (5 days - 3 weeks): Fibroblasts proliferate, synthesize Type III collagen. ↑ vascularity & cellularity.
      1. Remodeling/Maturation (3 weeks - 1 year+): Type III collagen gradually converts to Type I. ↑ tensile strength, collagen cross-linking & reorientation along stress lines.
  • Key Factors Influencing Healing: Age, smoking, diabetes, nutrition, vascularity, type of injury, gap size, infection, controlled early mobilization (crucial!).

⭐ Sutured tendons typically regain ~50-60% of their original strength by 6 weeks; achieving near-normal strength can take up to 1 year or more, and it may never reach 100% pre-injury levels.

Flexor Tendon Injuries - Flexor Fails & Fixes

Flexor tendon zones of hand

  • Anatomy & Function:
    • FDS (Flexor Digitorum Superficialis): Flexes PIP joint.
    • FDP (Flexor Digitorum Profundus): Flexes DIP joint.
    • Vincula: Segmental blood supply to tendons.
  • Verdan's Zones: Critical for management & prognosis.
    • Zone I: FDP only (distal to FDS insertion). Common:

Extensor Tendon Injuries - Extensor Wrecks & Repairs

  • Extensor tendons: flatter, less robust than flexors; lie superficially, prone to injury. Less retraction due to juncturae tendinum. Poorer blood supply.
  • Repair often challenging due to thinness and risk of adhesions. Early motion protocols crucial.

Extensor tendon zones of hand

  • Common Injuries & Deformities:
    • Mallet Finger (Zone I/II): Injury to terminal extensor tendon insertion on distal phalanx.
      • Cause: Forced flexion of extended DIP.
      • Presentation: DIP joint rests in flexion (~45°); inability to actively extend DIP.
      • Treatment: Uninterrupted splinting of DIP in full extension for 6-8 weeks. Surgical pinning if large fracture fragment or subluxation.
    • Boutonniere Deformity (Zone III/IV): Injury to central slip insertion on middle phalanx.
      • Pathophysiology: Central slip disruption → lateral bands displace volarly → PIP flexion & DIP hyperextension.
      • Treatment: PIP joint splinted in full extension for 4-6 weeks, allowing DIP motion.

⭐ Elson's test is used to diagnose a central slip rupture (potential Boutonniere): PIP flexed to 90° over edge of table, patient attempts to extend middle phalanx. Weakness/absence of extension with fixed DIP indicates rupture.

High‑Yield Points - ⚡ Biggest Takeaways

  • Zone II flexor injuries ("No Man's Land") have poorest prognosis due to adhesion risk.
  • Mallet finger: Terminal extensor tendon disruption (Zone I), causing DIP droop.
  • Boutonnière deformity: Central slip injury (Zone III), causing PIP flexion, DIP hyperextension.
  • Jersey finger: FDP avulsion (Zone I flexor), often ring finger, unable to flex DIP.
  • Early active motion is key post-flexor repair to prevent adhesions.
  • Primary repair is ideal for acute tendon injuries.

Practice Questions: Tendon Injuries

Test your understanding with these related questions

Which type of collagen is predominantly present in the skin?

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Flashcards: Tendon Injuries

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The _____ (bone) is typically injured due to a fall on an outstretched hand.

TAP TO REVEAL ANSWER

The _____ (bone) is typically injured due to a fall on an outstretched hand.

scaphoid

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Tendon Injuries - Free Indian Medical PG Review