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Procedures · Extremities3 min read5-question check

Clavicle, AC Joints, SC Joints and Scapula

Angle cephalad for an AP axial clavicle, hang equal weights from the wrists for AC joints, and the SC joint closest to the IR is the one shown.

Clavicle

The clavicle is shown with an AP or PA projection and an axial. For the AP, the patient is supine or erect, CR perpendicular to the midshaft, 40 inches, exposed at the end of inspiration. The AP axial angles the CR 15 to 30 degrees cephalad to project the clavicle above the scapula and ribs. Thin, asthenic patients need more angle, closer to 30 degrees, and broad, hypersthenic patients need less, closer to 15. A PA axial reverses this with a caudad angle, which brings the clavicle closer to the IR for less magnification.

AC joints

The AC joints are taken erect, AP, both sides, with and without weights, to look for separation. Use 72 inches to reduce magnification and fit both joints, centering about 1 inch above the jugular notch. Take the non-weight-bearing images first. Then hang equal weights, often 5 to 8 pounds each, from both wrists. The patient should not grip them, because gripping tightens the shoulder muscles and can mask a separation. Rule out a clavicle fracture before adding weights.

SC joints

The sternoclavicular joints are shown with a PA, CR to the level of T2 to T3, about 3 inches below the vertebra prominens, with breathing suspended on expiration. For the obliques, rotate the patient 10 to 15 degrees in an RAO or LAO. The joint closest to the IR is the one demonstrated: an RAO shows the right SC joint. Only slight rotation is used, because the joints sit close to the midline.

Scapula

For the AP scapula, abduct the arm 90 degrees and supinate the hand. This draws the scapula laterally off the rib cage. Center 2 inches below the coracoid process at 40 inches; a slow breathing technique can blur the ribs and lung markings. The lateral scapula is an anterior oblique, RAO or LAO, with the affected side toward the IR, rotated 45 to 60 degrees until the scapular body is perpendicular to the IR. Move the arm across the chest or behind the back so the humerus does not overlap the body. A correct lateral shows a thin scapular body free of the ribs.

Clinical Example

A cyclist fell onto his shoulder and has a tender bump over the right AC joint. After the non-weight-bearing image shows no clavicle fracture, the radiographer straps 7-pound weights to each wrist and repeats the bilateral AP at 72 inches. The right AC joint widens under load, confirming a separation.

Common Mistakes

  • Letting the patient grip the weights, which can hide an AC separation.
  • Using the same axial angle for every body type on the clavicle.
  • Picking the wrong side for an SC joint oblique; the joint nearest the IR is shown.
  • Leaving the arm at the side for an AP scapula, so the scapula overlaps the ribs.

Why It Matters

Clavicle, SC joints, scapula, and AC joints with and without weights are all on the 2027 standard projection list. Questions often ask which side is shown, which way to angle, or why a detail of the setup matters.

Key Relationships

  • AP axial clavicle → 15 to 30 degrees cephalad; thinner patient, more angle
  • AC joints → 72 inches, equal weights hung from wrists, not gripped
  • SC joint oblique → 10 to 15 degrees; joint closest to IR shown
  • AP scapula → arm abducted 90 degrees, hand supinated
  • Lateral scapula → 45 to 60 degree anterior oblique, body perpendicular to IR

Check yourself

5 questions

  1. 1

    For AC joint images with weights, why should the weights be attached to the wrists rather than held in the hands?

  2. 2

    Which SID is recommended for bilateral AC joint images?

  3. 3

    An RAO oblique of the sternoclavicular joints best shows:

  4. 4

    For an AP axial clavicle on a thin, asthenic patient, the CR should be angled:

  5. 5

    For the AP scapula, why is the arm abducted 90 degrees?

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