Middle phalanx: Biaxial eminence fractures

Biaxial eminence fractures affect only the palmar or plantar aspect of the pastern joint. Their most distal extent may approach the navicular apparatus. They result in substantial palmar/plantar instability. The medial and lateral eminences are often separated by a sagittal or parasagittal fracture.
The horses present as acute onset, and severe lameness, accompanied by instability of the digit. Localizing signs include mild to moderate soft-tissue swelling in conjunction with pain and instability of the pastern region.
All breeds can be affected, but horses engaged in Western performance activities may be overrepresented.

Degenerative disease of the proximal interphalangeal joint as well as fractures of the middle phalanx are seen in most breeds of horses. However horses engaged in western performance activities seem predisposed to injuries involving the proximal interphalangeal joint, especially fractures of the middle phalanx, likely due to the bending and torsional forces generated during abrupt stops and changes in direction.
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Complete radiographic evaluation of the pastern region reveals biaxial eminence fracture fragments affecting the proximal palmar / plantar aspect of the middle phalanx. In addition, there may be varying degrees of malalignment and distal displacement of the proximal phalanx.