The most common physeal fracture in horses is a Salter–Harris type II [175]. These have been reported in the third metacarpal and metatarsal distal physes, distal femoral physis and proximal tibial physis [175–177]. Physeal fractures of the proximal tibia have a typical pattern of type II with a lateral metaphyseal corner [179]. Type IV injuries tend to be unstable and many require internal fixation [180]. Bridging of the physis during internal fixation of physeal fractures should be avoided if possible as it may result in premature closure and subsequent development of angular limb deformity [180]. Type V injuries are rare, and are often not initially radiographically detectable, but manifest as a progressive angular limb deformity [176].
Table 3.2 Features and qualifiers of features applicable to fracture description.
Source: Stover [170]. Reproduced with permission of Sage Publication.
| Feature | Qualifier | Description |
|---|---|---|
| Location | Epiphysis | Fracture involves the end of a long bone |
| Physis | Fracture involves an open physisa | |
| Metaphysis | Fracture involves a region of the bone adjacent to the physis on the side closest to the diaphysis | |
| Diaphysis | Fracture involves the central region of a long bone | |
| Direction | For example, proximodorsal to distopalmar | Direction(s) of the fracture line(s) is (are) described from proximal to distal unless the direction of propagation is known (e.g. MCIII/MTIII condylar fractures progress from distal to proximal) |
| Plane | For example, transverse, oblique, longitudinal, sagittal and dorsal | Orientation of the predominant fracture line |
| Configuration | Transverse | Fracture courses perpendicular to the longitudinal axis of the bone |
| Longitudinal | Fracture courses parallel to the longitudinal axis of the bone | |
| Oblique | Fracture courses along a flat plane obliquely through the bone (i.e. not parallel to a transverse or longitudinal plane) | |
| Spiral | Fracture has a spiral component | |
| Butterfly | Fracture has transverse and oblique components | |
| Extent | Complete | Fracture courses completely through the bone, dividing it into two or more separate fragments |
| Incomplete | Fracture does not course completely through the bone | |
| Displacement | Nondisplaced | Fracture fragments remain in anatomic apposition |
| Displaced | Fracture fragments separated, angulated or overriding, and no longer in anatomic apposition | |
| Complexity | Simple | One fracture line dividing the bone into two separate fragmentsb |
| Intermediate | May have one or two sizeable bony fragments (e.g. complete mid‐diaphyseal metacarpal/metatarsal fracture with a butterfly component) | |
| Complex | Multiple fracture lines and ≥3 bony fragments or greater comminution | |
| Joint involvement | Non‐articular | The fracture does not extend through an articular surface |
| Articular | The fracture courses through an articular surface | |
| Contamination | Closed | The skin overlying the fractured bone is intact and not penetrated by the injury |
| Open | The skin has a wound over the fracture that introduces contamination and increases the risk of infectionc | |
| Other | Avulsion | A fracture fragment that distracted from the parent bone by tension through a soft tissue (tendon and ligament) attachment |
| Slab | A biarticular fracture with the fracture plane perpendicular to the articular surfaces of the parent bone | |
| Condylar | Fracture involves a condyle |
a Physeal fractures are further described according to the Salter–Harris classification scheme.
b One or two minor bone chips do not change the definition of a fracture as simple.
c Open fractures are further classified according to [171].
Completeness
A complete fracture occurs when a bone is separated into two or more parts. Complete fractures may divide a bone into individual segments, or a fragment of bone can be completely separated from the parent bone. An incomplete fracture typically involves only one cortical or subchondral compacta without propagating to another cortical or articular surface. Additional subcategories of incomplete fractures include fissure fractures, where a crack extends into but not through one cortex (seen commonly in the tibia and radius), and greenstick fractures, where the cortex loaded in tension fractures and the opposing cortex bends, such as those occasionally seen in the middle of the metacarpal/metatarsal diaphysis in foals [181].
Complexity
Fracture complexity must be considered