Ulna/elbow classification

Bayne classified ulnar dysplasia according to the morphology of the ulna and elbow:

• I - hypoplasia:
  • ulna hypoplastic with presence of distal and proximal ulnar epiphyses
  • frequently minimal deformity or shortening
  • slight ulnar deviation of hand
  • minimal bowing of radius
• II - partial aplasia:
  • absent distal or middle third of ulna
  • fibrous anlage distally that may cause progressive ulnar deviation
  • progressive radial bowing
  • stable elbow
• III - complete aplasia:
  • total agenesis of ulna with often a fibrous anlage in its place
  • radius often straight
  • unstable elbow
  • severe deficiencies of hand and carpus
• IV - synostosis:
  • entire limb is shortened
  • fusion of radius to humerus produces a stable elbow
  • progressive ulnar deviation due to a distal ulnar anlage

Type II is the most common abnormality.

Ref: Bayne LG (1985); Hand Clin 1(3): 457-465.