Limb Radiography

Views of the Limbs
The most common are the lateral view and the craniocaudal or dorsopalmar/ plantar. The different views silhouette different aspects of the bones.

Lateral view of limb bones and joints: In small animals, the limb to be radiographed is placed on the cassette. Pull the affected limb forward and retract the other limb. The lateral view silhouettes the cranial and caudal surfaces of the bones. Craniocaudal or dorsopalmar views silhouette the medial and lateral structures of the limb.

Structures  silhouetted - thoracic limb

Lateral view
a) cranial structures

b) caudal structures Cranocaudal or dorsopalmar view
a) lateral structures b) medial structures

Thoracic Limb
Shoulder Joint or scapulohumeral joint: The lateral and caudocranial views are standard for the shoulder. Take the lateral view by placing the dog in lateral recumbency with the affected leg on the cassette. Push the affected limb dorsally (forwards) and draw the unaffected limb caudally to separate the limbs. To take a caudocranial view of the shoulder place the dog in sternal recumbency, extend the leg cranially and rotate the limb medially to pull the scapula away from the thorax.
When viewing shoulder films the joint space should be of equal width all around the head of the humerus. The head of the humerus should be smooth and round, with no flattened areas. Check for fractures of the spine of the scapula in the craniocaudal view. Do not confuse the accessory ossification centre of the caudal aspect of the scapula with OCD (osteochondrosis dissecans) which occurs on the caudal aspect of the head of the humerus. The entire radiograph should be examined, including structures other than the shoulder joint - neck, cervical vertebrae, ribs, air-filled trachea and lung fields.

Elbow Joint:  The flexed medio-lateral elbow is often taken as it pulls the anconeal process out of the olecranon fossa of the humerus.
Craniocaudal and mediolateral views are routinely taken.
Three important radiographic structures are listed:

Pelvic Limb
Hip dysplasia view: Place the dog in dorsal recumbency with the limbs pulled caudally and rotated slightly medially to place the femurs parallel to each other, the patellas centred in the trochlea of the femur.  Superimpose the femur and the ischiatic tuberosity similarly on both sides.  The film should include views from below the stifle to just cranial to the iliac crests. The pelvis must be level (no rotation). Rotation will make one acetabulum look very deep and one very shallow; therefore one joint will appear better. Any degree of rotation can be checked by looking at the symmetry of the obturator foramen. Rotation will cause the “up” foramen to appear larger and rounder, and the “down” side smaller and more elliptical. Rotation also causes the wings of the ilium to appear of different widths.

Stifle/Hock/Phalanges: Mediolateral and dorsoplantar views should be taken.

Evaluating radiographs of the hind limbs:
Recognise different anatomical variations for the bones. A German Shepherd humerus looks different than that of a chondrodystrophic dog (Dachshund). Follow the cortex and see if it thins or thickens or if there are breaks in it. Know the locations of the nutrient foramina so they are not mistaken for lytic areas (dissolved areas).

Positioning terms & techniques