Interpretation of

Appendicular Skeleton

BY: Girjesh Upmanyu

Positioning of Patient

In 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 proximal

humerus for evaluation of bicipital groove for changes

associated with biceps or supraspinatus tendinopathy

Flexed dorsoplantar view of

canine tarsus for

evaluation of trochlea of talus

for changes associated with

osteochondrosis, without

superimposition of calcaneus.

Dorsal acetabular rim view of canine pelvis for

evaluation of lateral aspect of acetabulum for

Remodeling.

OBLIQUE PROJECTIONS

Oblique 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 nonaggressive

bone lesions

Aggressive 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 Cortex

Many 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

• Geographic bone lysis is a large, relatively well-defined region of bone loss

Geographical

• Moth-eaten bone lysis gets its name from the appearance of moth damage in cloth

• It is characterized radiographically as multiple small regions of lysis

Moth-eaten

• Permeative lysis is the least well-defined lytic pattern, where the bone lysis is confluent and not demarcated clearly from adjacent normal bone.

• Permeative lysis is the most common pattern of bone lysis that accompanies an aggressive bone lesion

Permeative

Periosteal Reaction

An 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 Zone

The 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.

Thank You