Radiography of the equine fetlock
Equine Radiography – the Metacarpo- and Metatarsophalangeal Joints (Fetlocks): ‘Standard Views’
- Investigation of lameness localized to the region of the fetlock joint (as determined by perineural/intra-articular anaesthesia).
- Pre-purchase examinations.
- Investigation of traumatic/penetrating wounds to the fetlock region.
- Assessment of angular limb deformities.
- Monitoring progression of disease.
- Ensure the hair coat is clean to minimize the likelihood of artefacts appearing on the radiograph.
- Particularly nervous horses may need to be sedated, although radiography of this region is usually well-tolerated by most horses.
- The horse should be standing as square as possible, evenly weight-bearing on all four limbs, with the cannon bone of the limb to be radiographed as vertical as possible in both planes.
- Remember that use of markers is very important – LEFT and RIGHT but also FORE LIMB and HIND LIMB (easily added on modern digital systems). By convention the L/R markers are placed either laterally on a DP view, or dorsally on lateral and oblique views.
- Four or five ‘standard’ views:
- dorsolateral-palmaromedial oblique
- dorsomedial-palmarolateral oblique
- (flexed lateromedial)
- Various other ‘specialist’ views for identifying specific lesions or when the ‘standard’ views have found no pathology.
- Note that the techniques are the same for the hind limb as for the fore limb but for the sake of brevity only the fore limb terminology is given below.
- the x-ray beam should be horizontal, and perpendicular to the dorsopalmar axis of the leg at the level of the fetlock joint.
- centre on the joint space.
- beware animals standing with the limb slightly turned out (or in) – a true lateral view is necessary to fully evaluate the sagittal ridge of the cannon bone.
- Dorsopalmar view (DP):
- center on the joint space.
- a horizontal x-ray beam will lead to superimposition of the proximal sesamoid bones on the joint space, but…
- a dorsoproximal-palmarodistal angulation of 10-15o will prevent this from happening.
- Dorsolateral-palmaromedial oblique (DLPMO):
- highlights the dorsomedial and palmarolateral (abaxial) aspects of the joint, as well as the sesamoid bones.
- the x-ray beam should be horizontal, and at a 45o angle to the dorsopalmar axis of the leg, aiming from a dorsolateral position towards a palmaromedial position.
- center on the joint space.
- Dorsomedial-palmarolateral oblique (DMPLO):
- as for the DLPMO but from a dorsomedial position aiming towards a palmarolateral position.
- Flexed lateral:
- highlights the articular surfaces of the proximal sesamoid bones.
- raise the foot either by placing on a wooden block or by holding the toe with a gloved hand (to a height of 20-30cm).
- center on the centre of the condyles of MC III.
- remember to aim to get a true lateral view as with the standard LM view.
- this view may require a lower mAs setting.