ELBOW : AP PROJECTION

X-ray of the Elbow AP

AP projection is the routine position of the forearm, unlike PA view the bones of in forearm (radius and ulna) crosses over, resulting in an oblique view of the elbow. Lateral epicondyle, Capitulum, Radial head, Radial neck, Radial tuberosity, Medial epicondyle, Trachlea and Proximal ulna are demonstrated on the radiograph. Bone fracture, dislocation and some pathology like, osteomyelitis and arthritis are also demonstrated if present.


Film Size : 10 x 12 inches or 11 x 14 for tall and large patients.

• Crosswise - can be divided in half for two projections
• Table Top
• Detailed Screen

Digital IR : Use lead masking

kVp : 60
mAs : 2
SID : 48 inches
CR : Perpendicular to elbow joint, 2cm distal to the middle line between epicondyles.
Collimation : Four sides of the elbow joint

 

Patient and Part Position : AP Elbow

• Patient is seated at the end of the table high enough to put shoulder joint, humerus and elbow joint on the same level.
• Patient is leaning laterally to bring humeral epicondyles and long axis of the elbow parallel with IR.
• Palpating humeral epicondyles help ensure, IR and epicondyles of humerus are parallel.
• Lead shielding is placed over the pelvic area.
• Elbow is extended, Supinate Hand and image receptor is center to the elbow joint.

Note: Supinated hand will prevent rotation of the bone of the forearm and result in a true AP view of the elbow joint. Pronated hands also result in an oblique view of the elbow.

• Long axis of the elbow is parallel to image receptor.

Trauma Patients Unable to Fully Extend Elbow

When Patient is in trauma with possible elbow fracture a lateral projection can be easily to do, however a two AP projection should be obtained to prevent a distorted images of the part elevated from image receptor. 

Forearm is Parallel to Image Receptor

This projection will best demonstrate the proximal forearm without magnification and a foreshortened image of the distal humerus. It is also known as AP Proximal Forearm : Partial Flexion. 

Patient and Part Position : Proximal Forearm Partial Flexion

Dorsal Surface of the forearm is resting on the cassette, this could be easier for them by providing a seat high enough to permit this position. Another way is by elevating the limb with a support, put forearm in a lateral position and place the IR vertically behind the upper end of the forearm and direct central ray horizontally.

Humerus is parallel to IR 

In this position the humerus is parallel to image receptor and show the distal humeral bone when patient cannot fully extend the elbow. It is also known as AP Projection : Distal Humerus in Partial Flexion. Radiographic Criteria are as follows:

• No rotation or distortion of the distal humerus.
• Superimposed proximal radius over ulna
• Closed elbow joints
• Greatly foreshortened proximal forearm
• Trabecular markings on the distal humerus.

Patient and Part Position : Distal Humerus Partial Flexion

• Provide the patient with a seat low enough to place the entire humerus resting on cassette, and provide support for the elevated forearm.
• Supinate hand if possible, and place IR below the elbow  and center to condyloid area of the humerus.
• Angle central ray distally into the joint depending on the degree of flexion.
• Central Ray is perpendicular to the humerus, traversing to the elbow joint.

Holly Method : Radial Head

Holly describe a method of obtaining an AP projection of the radial head. In this method the patient position is just similar to the distal humerus but the elbow is extended as much as possible as the forearm is supported. Supinate hand enough as possible to place the horizontal plane of the wrist at an angle of 30° from horizontal.

Radiographic Criteria: Elbow AP Projection

• Distal humerus, elbow joint space, and proximal radius and ulna are visible.
• Radial head, neck and tuberosity are slightly superimposed to the proximal ulna.
• An open elbow joint space and centered on radiograph.
• No rotation of humeral epicondyles and entire elbow joint.

Evidenced of No Rotation are the following:

• Appearance of bilateral epicondyles seen in profile
• Radial head, neck and tubercles separated or only slightly superimposed by ulna.
• The olecranon process should be seated in the olecranon fossa with fully extended arm
• Elbow joint space appear open with fully extended arm and proper CR centering.

• Collimation should be visible on four sides to area of affected elbow
• Central ray and center of collimation field should be to the mid elbow joint.
• Optimal density and contrast with no motion should visualize soft tissue detail and sharp, bony cortical margins and clear, bony trabecular markings.