September 2013 Small animal case

Dog Boxer 3 Years of age Male intact Presented 2 day after being hit by car. Painful on the left front limb in the region of the shoulder and carpal instability. Radiographs of the left shoulder were taken.

Radiographic examination

Mediolateral view (on the left ) and caudocranial view (on the right) of the left shoulder.

Radiographic findings

  • The mediolateral view of the shoulder is within normal limits.
  • On the caudocranial view, there is a radiolucent line running accross the lesser tubercle of the humerus with mild step formation and fragment separation (arrow).
  • The diagnosis was fracture of the lesser tubercle of the left humerus with mild dislocation.

Radiographic diagnosis

Close up of the caudocranial view of the left shoulder

The dog underwent surgical fixation

Post OP mediolateral view (on the left ) and caudocranial view (on the right) of the left shoulder.

Comments

  • The left carpus was also stabilised in the same surgical session (not shown).
  • The lesser tubercle is the point of insertion for the subscapularis muscle.
  • Humeral fracture are quite common, with a reported incidence of 4.4% in cat and from 5.4% to 7.7% in dogs.
  • The most common causes are automobile accident, falls and gunshot.
  • Three classic patterns for humeral fractures have been described:
  • Approximately 20% of humeral fractures are physeal fractures in immature dogs.
  • Approximately 50% are diaphyseal fractures resulting from major trauma.
  • Approximately 20% are condylar fractures in adult dogs, secondary to incomplete ossification of the humeral condyle.
  • The fractures in the area of the lesser tubercle are more rare, one have been reported in association with a shoulder luxation (Huck et al, Vet Comp Orthop Traumatol 2011).
  • The present case also stresses the importance of taking two orthogonal radiographic views of the region of interest.