Elbow

Kinematics of the elbow

  • Flexion range
    • 150o
  • Rotation range
    • Pronation 80o
    • Supination 85o
  • Carrying angle
    • Male 7o
    • Female 13
    • Cubitus valgus = > 15o
    • Cubitus varus = < 5 – 10o
  • Kinetics
    • inefficient because of short lever arms of muscle insertions
    • In maximal extension & pronation = up to 3x TBW through elbow in lifting
    • 60% radial, 40% ulna

Radial head is important for acute + long term stability & to prevent pathologic proximal migration.

  • Valgus Stability
  • Radial head is secondary stabiliser resisting valgus load
  • Radial head excision ↓lever arm to medial ligament & therefore ↑MCL tension for same valgus force
  • Longitudinal Stability
  • Radius vs. ulna load sharing at the elbow varies according to pronation/supination (as central portion interosseous ligament changes alignment) & flexion/extension
  • But Halls + Travill quoted → ulna = 60% + radius = 40%
  • Radial head preservation paramount when interosseous ligament torn
  • In proximal radial migration, deformity is at wrist = distal ulna dorsal + distal to carpus = supination + extension block
  • Limited results from ulna shortening, Sauve-Kapandji, Darrach, in established proximal radial migration
  • Salvage = one bone forearm (radioulnar synostosis) to maintain elbow flexion/extension & wrist function albeit fixed in rotation
  • Radial head replacement