interpretation of appendicular skeleton (veterinary)
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RADIOGRAPHIC ANATOMY & INTERPRETATION OF APENDICULAR SKELETON
Interpretation of Appendicular SkeletonBY: Girjesh UpmanyuPositioning of PatientIn the appendicular skeleton, patient should consist of a minimum of two orthogonal projections, a lateral view and a craniocaudal (dorsopalmar, dorsoplantar) view.
If a bone lesion is suspected, it is important that the field of view include the joint proximal and distal to the bone of interest.Cranioproximal-craniodistal view of canine proximalhumerus for evaluation of bicipital groove for changesassociated with biceps or supraspinatus tendinopathy
Flexed dorsoplantar view of canine tarsus forevaluation of trochlea of talus for changes associated with osteochondrosis, without superimposition of calcaneus.
Dorsal acetabular rim view of canine pelvis forevaluation of lateral aspect of acetabulum forRemodeling.
OBLIQUE PROJECTIONSOblique views are intended to project different edges of a joint or region.
Oblique views maximize the chances of projecting an edge lesion tangentially in a complex joint.
Aggressive versus nonaggressivebone lesionsAggressive process: such as a tumor or infection.
Nonaggressive process: such as a bone cyst.
The aggressiveness of a bone lesion is related to three criteria: -(1) whether or not there is destruction of the cortex.(2) the character of any periosteal reaction, and (3) the distinctness of the boundary between the bone lesion and the normal bone, called the transition zone.
Destruction of the CortexMany aggressive bone diseases are characterized by destruction of the cortex. e.g, malignant bone tumors are often associated with destruction of the cortex, through mechanisms such as increased matrix metalloproteinase activity or increased osteoclast activity.
Bone infections also can result in destruction of cortical bone, e.g. by an alteration in the inflammatory response that disrupts the homeostatic balance of bone matrix deposition and resorption, thereby mediating bone destruction.
For cortex destruction to be apparent radiographically, the region of destruction must be hit tangentially by the primary x-ray beam.
Classification of bone destruction
Periosteal ReactionAn active periosteal reaction is one where the margin of the periosteal reaction is irregular and not smooth.
periosteal irregularity is the basic change that dictates the lesion is aggressive.
a nonaggressive periosteal reaction is characterized by a smooth edge to the periosteal new bone growth.
Transition ZoneThe character of the junction of the bone lesion with the adjacent normal bone is termed the transition zone.
The transition zone is typically evaluated in the medullary cavity of the bone, and its character is a clue as to the aggressiveness of the lesion.