Humerus X-Ray Positioning: AP, Lateral & Transthoracic Views
The humerus is the long bone of the upper arm, extending from the shoulder to the elbow. Injuries may involve the proximal humerus, shaft, or distal humerus; age and mechanism strongly affect the fracture pattern. A humerus examination must not substitute for dedicated shoulder or elbow views when clinical findings localize to either joint.
As a radiologic technologist, you need to understand the standard humerus series and its trauma modifications. Humerus positioning falls within the broader radiographic-procedure knowledge used in education and certification preparation, but ARRT does not publish a guaranteed humerus-specific question count.
This guide covers the AP, lateral, and transthoracic lateral (Lawrence method) views, plus a trauma modification for patients with limited mobility.
Anatomy of the Humerus
Before positioning, make sure you can identify these key landmarks — they're all ARRT exam material:
| Structure | Clinical Notes |
|---|---|
| Head | Articulates with the glenoid cavity of the scapula |
| Anatomic neck | Just below the head; fracture here is less common |
| Surgical neck | Common site of proximal-humerus fracture; distal to the tubercles |
| Greater tubercle | Lateral aspect; insertion for supraspinatus, infraspinatus, teres minor |
| Lesser tubercle | Medial/anterior aspect; insertion for subscapularis |
| Shaft (diaphysis) | Long body; midpoint is the centering point for AP and conventional lateral whole-humerus projections |
| Medial and lateral epicondyles | Distal landmarks used to assess rotation on AP and lateral views |
| Trochlea | Medial distal articulation at the elbow |
| Capitulum | Lateral distal articulation at the elbow |
| Olecranon fossa | Posterior depression that receives the olecranon during elbow extension |
💡 ARRT Exam Tip
The surgical neck is a common site of proximal-humerus fracture and lies distal to the tubercles. Avoid the inaccurate claim that it is the single most common site of every humeral fracture; patterns differ by age and mechanism.
AP Humerus
The AP projection is one component of the usual two-projection humerus examination. At least two projections as close to orthogonal as the patient's condition safely permits are needed to assess displacement.
Patient Positioning
- Position: Upright preferred (standing or seated) with the patient's back against the upright Bucky. Supine is acceptable if the patient cannot stand.
- Arm (nontrauma): Abduct only enough to clear the torso. Supinate the hand and externally rotate the arm until the epicondyles are parallel to the IR.
- Trauma: Support the arm in the position found. Do not abduct, supinate, or rotate a painful, deformed, or immobilized limb solely to create textbook anatomy; align the IR and beam to the limb and document the modification.
- IR: A 35 × 43 cm (14 × 17 inch) IR lengthwise is common. Include both the shoulder and elbow joints. For a long arm, use overlapping exposures under the local protocol rather than excluding a joint.
Technical Factors
| Parameter | AP Humerus |
|---|---|
| Projection | Anteroposterior (AP) |
| CR | Perpendicular to mid-humerus shaft |
| Centering point | Midway between shoulder and elbow |
| SID | 100–102 cm (40 inches) |
| IR size | 35 × 43 cm (14 × 17"), portrait |
| Exposure | Manual technique from the validated local chart; patient size, detector and use of a grid determine kVp/mAs |
| Grid/AEC | Usually nongrid for a thin extremity; use a grid only when part thickness/scatter warrants it. AEC is generally unsuitable for the narrow, variably positioned shaft unless a validated institutional protocol specifies it. |
| Respiration | Suspend |
Evaluation Criteria
- Coverage: Entire humerus, including the glenohumeral and elbow joints
- Rotation: On a nontrauma true AP, epicondyles are parallel to the IR and the greater tubercle is in profile laterally; the lesser tubercle is largely superimposed by the humeral head
- Motion: Sharp bony margins and trabecular detail — no motion blur
- Technique: Uniform brightness from proximal to distal humerus; adequate penetration through both joints
⚠️ Clinical Pearl
Collimate to the long axis and soft-tissue margins of the humerus while retaining both joints. Do not open the field merely to match the entire IR; tight, anatomy-based collimation reduces scatter and patient dose.
Lateral Humerus
The conventional lateral is usually a lateromedial projection, with the lateral surface of the arm next to the IR. Obtain it only when movement is safe; trauma modifications may be less than perfectly orthogonal.
Patient Positioning
- Position: Upright or recumbent, with the affected arm's lateral surface nearest the IR; turn the torso as needed without forcing the limb.
- Arm (nontrauma): Flex the elbow as tolerated and internally rotate the arm, commonly by placing the hand on the hip or abdomen, until the epicondyles are perpendicular to the IR.
- Trauma: Do not force elbow flexion, internal rotation, or contact with the detector. Use a horizontal-beam or transthoracic modification appropriate to the level of injury.
- Result: The epicondyles are now perpendicular to the IR, producing a true lateral projection.
Technical Factors
| Parameter | Lateral Humerus |
|---|---|
| Projection | Lateral, usually lateromedial |
| CR | Perpendicular to mid-humerus shaft |
| Centering point | Midway between shoulder and elbow |
| SID | 100–102 cm (40 inches) |
| IR size | 35 × 43 cm (14 × 17"), portrait |
| Exposure | Manual technique from the validated local chart; do not assume AP and lateral require identical factors |
| Grid/AEC | Usually nongrid for a thin extremity; grid use is based on thickness/scatter. AEC only if specifically validated locally. |
| Respiration | Suspend |
Evaluation Criteria
- Coverage: Entire humerus including both shoulder and elbow joints
- Rotation: Epicondyles superimposed; lesser tubercle seen in profile medially; greater tubercle superimposed over the humeral head
- Motion: Sharp humeral outline and trabecular pattern
- Technique: Exposure sufficient to show cortex and trabecular detail from proximal through distal humerus
💡 ARRT Exam Tip
For a cooperative, nontrauma patient, elbow flexion and a hand-on-hip position help internally rotate the humerus so the epicondyles are perpendicular to the IR. These are positioning goals, not a reason to manipulate a suspected fracture.
Transthoracic Lateral Humerus (Lawrence Method)
When a patient has a suspected proximal-humerus fracture or immobilization that prevents rotation, the transthoracic lateral (Lawrence method) can provide a lateral view of the proximal humerus and glenohumeral region through the thorax without rotating the injured arm. It is not a lateral view of the entire humeral shaft.
When to Use
- Suspected proximal-humerus fracture with deformity
- Patient cannot abduct or rotate the arm
- Post-surgical or casted arm that cannot be manipulated
- Non-ambulatory trauma patients when a safe horizontal-beam setup is available
Patient Positioning
- Erect method: Place the patient lateral with the affected shoulder against the upright IR. Leave the injured arm supported in the position found. Raise the unaffected arm and shoulder above the head if the patient can do so safely.
- Recumbent method: Keep the patient supine or semierect; place the IR vertically against the affected shoulder and use a horizontal beam through the thorax. Do not roll the patient onto the injured side merely to obtain this view.
- Safety: Adjust the patient's torso, IR, and tube—not the suspected fracture—to reduce superimposition. Do not ask the patient to move the affected arm anteriorly.
Technical Factors
| Parameter | Transthoracic Lateral |
|---|---|
| Projection | Transthoracic lateral |
| CR | Horizontal and perpendicular through the thorax to the surgical neck. If the unaffected shoulder cannot be elevated clear of the region, some protocols use a 10–15° cephalad angle; this is a specific modification, not a default angle. |
| Centering point | Surgical neck of humerus |
| SID | 100–102 cm (40 inches) is common; follow the validated local protocol |
| IR size | Large enough for the proximal humerus and shoulder region; size/orientation is protocol- and patient-dependent |
| Exposure | Thorax-appropriate technique from the local chart; greater penetration than an isolated thin extremity is usually required |
| Grid/AEC | A grid is commonly appropriate because the beam traverses the thorax. Use AEC only with a specifically validated chamber selection and positioning protocol. |
| Respiration | Protocol-dependent: suspended respiration with a short exposure, or a deliberate gentle-breathing technique |
The Breathing Technique
A gentle-breathing technique can blur overlying ribs and lung markings, but it is not mandatory or universally used. If the department uses it, follow its validated mA/time technique and coach the patient to breathe gently. A short exposure with suspended respiration is a legitimate alternative and may better limit motion in pain or trauma. Do not prescribe an arbitrary 3–5-second exposure independently of the equipment and local technique chart.
Evaluation Criteria
- Coverage: Proximal humerus and glenohumeral region visible through the thorax
- Rotation: Humeral head and proximal humerus shown in lateral relationship; the distal epicondyles generally are not included and cannot be used as the rotation check
- Motion: Humeral cortex is acceptably sharp; overlying ribs may be blurred only when a breathing technique was intentionally used
- Technique: Adequate penetration through the thorax; soft tissue and bone detail visible
⚠️ Clinical Pearl
Maintain immobilization and support the limb. If the patient is already seated or recumbent, adapt the detector and use a horizontal beam rather than transferring or rotating the patient solely for a textbook projection.
Horizontal Beam Lateral (Trauma Modification)
For shaft trauma, a horizontal-beam projection can provide an additional view without rotating the injured arm. Whether it is truly orthogonal depends on the limb position and beam/IR geometry; the transthoracic view is useful mainly for the proximal humerus and must not be represented as a complete shaft lateral.
Technique
- Keep the patient supine or semierect and maintain splinting/support.
- Place a protected IR vertically beside the arm, parallel to the humeral long axis, without wedging it into the axilla or levering the limb.
- Direct a horizontal beam perpendicular to the IR and centered at mid-humerus; collimate to include both joints when geometry permits.
Tailor the setup to the injury and obtain the closest safe orthogonal relationship to the AP. If both joints or the region of interest cannot be demonstrated, obtain additional overlapping or dedicated views after radiologist/departmental review.
Positioning Summary Table
| View | Patient Position | CR Centering | Key Rotation Check | Best For |
|---|---|---|---|---|
| AP Humerus | Back to IR; external rotation only when safe | Mid-humerus shaft | Nontrauma: epicondyles parallel; greater tubercle lateral | Whole humerus; one of at least two views |
| Lateral Humerus | Lateral arm nearest IR; hand on hip/abdomen only when safe | Mid-humerus shaft | Epicondyles superimposed; lesser tubercle medial | Conventional orthogonal view |
| Transthoracic Lateral | Affected shoulder at IR; unaffected arm elevated if able | Surgical neck | Assess proximal humerus—not distal epicondyles; rib blur only if breathing technique used | Immobile proximal-humerus injury |
| Horizontal Beam Modification | Supine/semierect; vertical IR beside supported arm | Mid-humerus shaft | Closest safe orthogonal geometry | Shaft trauma; immobile arm |
Common Positioning Errors
Insufficient Joint Coverage
Both the shoulder and elbow joints should be demonstrated on whole-humerus images. A 35 × 43 cm IR is common but not "mandatory" for every patient or system. If one exposure cannot include both joints with diagnostic detail, use overlapping images under local protocol; do not repeat automatically before checking whether the existing image plus an additional limited image will complete the examination.
Rotation on AP
On a nontrauma AP, epicondyles should be parallel to the IR and the greater tubercle should be in profile laterally. If these criteria are absent, first consider whether pain, deformity, or immobilization appropriately required a modified AP; never repeat by forcibly rotating a suspected fracture.
Rotation on Lateral
If the epicondyles are not superimposed, the conventional lateral is oblique. In a nontrauma patient, adjust internal rotation as tolerated. Exact 90° elbow flexion and a hand-on-hip position are aids, not absolute requirements and not safe goals for every injury.
Poor Transthoracic Technique
Common issues include inadequate thoracic penetration, proximal humerus obscured by the spine, and motion. Rib sharpness alone is not an error when suspended respiration was intentionally used. Correct geometry by changing the torso, IR, or tube; do not move a suspected fracture anteriorly.
💡 ARRT Exam Tip
Transthoracic respiration is an institutional protocol difference. Gentle breathing with a validated long-time/low-mA technique can blur ribs; suspended respiration with a short exposure is also accepted. Patient condition and the local technique chart govern the choice.
ARRT High-Yield Facts
| Fact | Details |
|---|---|
| Fracture location | Surgical neck is a common proximal-humerus site; do not generalize it to every age/mechanism |
| IR/coverage | 35 × 43 cm is common; include both joints or use overlapping exposures |
| AP rotation check | Epicondyles parallel to IR; greater tubercle lateral |
| Lateral rotation check | Epicondyles superimposed; lesser tubercle medial |
| Lateral arm position | Internal rotation to superimpose epicondyles, only when safe |
| Transthoracic indication | Immobile proximal-humerus/shoulder injury; not a whole-shaft lateral |
| Transthoracic respiration | Gentle breathing or suspended respiration according to validated local protocol |
| AP arm position | Nontrauma: external rotation for epicondyles parallel; trauma: do not force |
Radiation Protection and Technique Selection
- Justify and optimize: Verify the order and side, collimate to the anatomy, use the department's size- and detector-specific chart, and avoid repeats by reviewing all available images first.
- Contact shielding: Routine gonadal or fetal contact shielding is not recommended by the AAPM because it offers little or no protection from internal scatter and may obscure anatomy or interfere with AEC. Follow current law and institutional policy; explain the rationale and accommodate a patient request when shielding can remain outside the field and cannot affect the examination.
- Pregnancy: Follow the facility's pregnancy-screening policy. A medically indicated extremity radiograph should not be withheld solely because of pregnancy; keep the abdomen outside the primary beam and optimize the examination.
When Additional Imaging Is Needed
A whole-humerus series shows that the adjacent joints are included, but it is not a complete dedicated shoulder or elbow examination. Obtain dedicated joint projections when symptoms, examination findings, or the initial images localize injury to the shoulder or elbow. If radiographs are negative or indeterminate despite persistent focal suspicion, follow the radiologist and applicable ACR pathway: CT or MRI may be appropriate for occult fracture, while the choice depends on the joint and suspected soft-tissue injury. Neurovascular compromise, open injury, or worsening pain requires urgent clinical escalation—not extra positioning attempts.
Sources and Scope
This educational guide is grounded in standard radiographic positioning instruction and the following professional guidance. Exact exposure factors, grid thresholds, detector size, AEC use, respiration, and allowed trauma modifications are institutional protocol differences; the validated local technique chart and radiologist-approved protocol take priority.
- Lampignano & Kendrick, Bontrager's Textbook of Radiographic Positioning and Related Anatomy, 10th ed. (Elsevier) — standard AP, lateral, trauma and transthoracic positioning principles.
- ACR Appropriateness Criteria: Acute Shoulder Pain — initial and follow-up imaging pathways.
- ACR Appropriateness Criteria: Acute Elbow and Forearm Pain — initial and follow-up imaging pathways.
- AAPM Position Statement PP 32-A: Patient Gonadal and Fetal Shielding — shielding, internal scatter, obscured anatomy and AEC concerns.
- U.S. FDA: Medical X-ray Imaging — justification, optimization and dose-reduction principles.
- IAEA Radiation Protection of Patients: Radiography — optimization and radiation-protection resources.
Related Articles
- Shoulder X-Ray Positioning Guide — AP, Grashey, Y-view, and axillary shoulder projections with centering points
- Elbow X-Ray Positioning Guide — AP, lateral, oblique, and Coyle method for radial head fractures
- Upper Extremity Positioning Guide — Hand, wrist, and elbow projections
- Trauma Radiography Principles — Modified techniques for non-ambulatory and trauma patients
- X-Ray Modality Page — Complete list of radiographic procedures