scheme [174–176] (Figure 3.20). Physeal fractures are typically caused by a combination of compressive, shear and bending forces [176]. The proximal ulnar physis is not involved in the formation of a joint and is therefore termed an apophysis. The Salter–Harris classification system is therefore not completely applicable to fractures of the proximal ulnar physis, and a specific type 1–5 scheme is applied [178].
Table 3.1 Predictable sites of stress fractures and stress remodelling.
| Bone/joint | Anatomical region | References |
|---|---|---|
| Scapula | Distal aspect of the spine | [140] [145] |
| Humerus | Caudoproximal Craniodistal Medial diaphyseal Caudodistal | [146] [144, 147] [148, 149] |
| Carpus | Dorsomedial third carpal bone Radial carpal bone Intermediate carpal bone | [150] [151] [89] |
| Third metacarpal | Mid‐diaphyseal and supracondylar Parasagittal groove Proximal palmar Dorsal cortex Distal condyle | [152] [60] [153] [154] [69] [155] |
| Proximal sesamoid | Palmar flexor region Medial sesamoid abaxial mid‐body subchondral bone | [38] [156] |
| Proximal phalanx | Sagittal groove | [157] [158] |
| Pelvis | Ilial wing Pubis | [159] [137] [160] [161] [162] |
| Tibia | Distomedial Caudoproximal Caudal diaphyseal Proximolateral under the head of the fibula | [163] [164] [148] |
| Tarsus | Dorsolateral third tarsal bone | [165] [166] |
| Lumbar spine | L5–L6 vertebral junction | [136] |
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 |
|
