Elbow, Humerus & Shoulder Positioning

Overview

Elbow, Humerus and Shoulder Girdle runs from the elbow joint up to the acromioclavicular joint, and nearly all of it turns on one line: the interepicondylar plane between the humeral epicondyles. Parallel to the receptor gives an AP, perpendicular gives a lateral, and 45 degrees gives an oblique, and the same plane works at both ends of the humerus.

The lateral elbow must be flexed exactly 90 degrees, because extending further seats the olecranon in its fossa and lifts the posterior fat pad on a normal joint, a false positive you caused. A correct lateral shows three concentric arcs and superimposed epicondyles. When the elbow will not extend, the Coyle method pairs two 45 degree tube angles: toward the shoulder with 90 degrees of flexion for the radial head, away from the shoulder at 80 degrees for the coronoid process.

At the shoulder, external rotation is the true AP and puts the greater tubercle in profile laterally, while internal rotation is the true lateral and profiles the lesser tubercle medially. The Grashey method rotates the body 35 to 45 degrees to open the glenoid cavity, the scapular Y uses a 45 to 60 degree anterior oblique to read dislocation direction, and 95 percent of shoulder dislocations are anterior.

AC joint studies are stress comparisons: two identical bilateral exposures, without and then with equal weights strapped to each wrist (8 to 10 pounds minimum on a large adult, 5 to 8 on a smaller one), never held, and only after fracture has been ruled out. Add the clavicle's 15 to 30 degree cephalad axial, split by habitus, and the trauma rule that you never rotate the arm on a suspected fracture, and you have the numbers this chapter is tested on.