Читать книгу Fractures in the Horse - Группа авторов - Страница 135

The principal limitations in equine fracture detection are lesion location, acquisition time, motion artefact and low SNRs associated with STIR sequences in sMRI. The low signal intensity of normal compact bone complicates the detection of subtle non‐displaced cortical fractures [145]. This is particularly important if secondary signs of fracture such as intra‐osseous fluid accumulation are not identified. In addition, the low signal intensity of compact bone, tendon and ligament can make avulsed bone fragments difficult to identify [146]. In general, identification of any small osseous or osteochondral fragment can be difficult if the fragment is near to compact bone or intact collagen. The requirement for multiple coil placement for the evaluation of long fractures in sMRI has both time and sedation implications [145].

Figure 5.12 Four‐year‐old Thoroughbred racehorse with acute onset right forelimb lameness and pain on palpation of the dorsoproximal aspect of the proximal phalanx. (a) Dorsopalmar radiograph on day one: no abnormalities evident. Same day T1W GRE (b) and STIR FSE (c) dorsal plane sMRI depicting sagittal area of T1W hypointensity and intense STIR hyperintensity in the proximal third of the bone (arrows) compatible with a short incomplete proximal phalangeal fracture. Dorsopalmar (d) and lateromedial (e) radiographs taken six weeks post‐operatively. A sharp radiolucent line can be seen in the subchondral bone of the proximal phalanx (arrow), and periosteal new bone is evident dorsally (arrows).

Lack of pathological correlation in many areas of equine MRI means that interpretation is frequently subjective. This is particularly relevant to the parasagittal grooves of the metacarpal and metatarsal condyles. Fissures have been described which may represent normal variation in condylar groove morphology or a genuine fissure fracture. The presence of intra‐osseous fluid accumulation surrounding the hyperintense area provides further evidence of significance.