Position Upper Extremity Imaging — Apply positioning principles for upper extremity imaging procedures.

The story of upper extremity radiographic positioning begins with the very first medical radiograph ever produced. On November 8, 1895, Wilhelm Conrad Röntgen discovered X-rays while experimenting with cathode ray tubes in his laboratory at the University of Würzburg. Within weeks, he captured the iconic image of his wife Bertha's hand—complete with her wedding ring—demonstrating the extraordinary diagnostic potential of this new form of radiation. That seminal image of a hand established upper extremity imaging as the foundational application of radiography, and the discipline has evolved through more than a century of refinement in positioning techniques, equipment design, and image quality standards.

Early radiographers quickly discovered that the angle at which X-rays passed through anatomical structures profoundly affected the diagnostic value of the resulting image. Overlapping bones, foreshortened projections, and poor joint-space visualization plagued images produced without standardized positioning methods. As the medical community recognized that reproducible, high-quality radiographs required systematic approaches, pioneers in the field began codifying specific body positions, tube angles, and central ray placements for each anatomical region. The upper extremity, with its complex arrangement of small bones, multiple joints, and overlapping soft tissue structures, became a testing ground for these emerging positioning principles.

The central question that positioning science addresses is deceptively simple: How do we orient the patient's anatomy relative to the X-ray beam and image receptor so that each bone and joint is displayed without distortion, overlap, or foreshortening? Answering this question for the more than two dozen bones and numerous joints of the upper extremity requires a command of surface anatomy, joint mechanics, central ray alignment, and image evaluation criteria—all topics that will be explored systematically in the sections that follow.

Successful upper extremity radiography depends on a handful of interrelated principles that, once internalized, can be applied across every projection from the fingertips to the shoulder girdle. Before examining specific positions, it is essential to understand the vocabulary and core concepts that underpin them. The ARRT expects radiography graduates to demonstrate fluency in these principles both on the certification examination and in clinical practice.

Several additional terms are critical for the ARRT examination. A projection describes the path of the central ray from its entry point to its exit point through the patient (e.g., PA means the CR enters posteriorly and exits anteriorly). A position describes how the patient's body is placed, such as prone, supine, or oblique. A view refers to how the image is displayed—the radiograph is named by the surface of the body closest to the image receptor. Understanding these distinctions avoids the common error of conflating projection with position, a topic frequently tested on the ARRT certification exam.

A thorough understanding of upper extremity positioning requires a mental map of the skeletal anatomy from the phalanges distally to the proximal humerus and shoulder girdle. The diagram below illustrates the major bones and joints of the upper extremity in an anterior (palmar) view, with annotations identifying the key anatomical landmarks that serve as positioning references and central ray centering points.

As illustrated in the diagram, the upper extremity comprises distinct anatomical regions, each requiring specific positioning considerations. The phalanges (14 bones in each hand) articulate at the interphalangeal (IP) and metacarpophalangeal (MCP) joints. The eight carpal bones form the wrist in two rows—the proximal row (scaphoid, lunate, triquetrum, pisiform) and the distal row (trapezium, trapezoid, capitate, hamate). The forearm contains the radius laterally and the ulna medially, which cross over each other during pronation—a fact with critical implications for forearm positioning. The elbow joint, where three bones articulate, requires careful attention to flexion angle and rotation. The humerus extends proximally to the shoulder, where the humeral head articulates with the glenoid fossa of the scapula.

While upper extremity positioning is not calculation-heavy, it is governed by geometric principles relating the X-ray tube, the body part, and the image receptor. Understanding these relationships helps radiographers predict how malpositioning affects image quality and apply corrective measures systematically.

Magnification Factor

Shape Distortion Principles

Shape distortion occurs whenever the body part, central ray, and image receptor are not properly aligned. Foreshortening results when the long axis of the bone is angled relative to the IR, making it appear shorter than its true length. Elongation occurs when the CR is angled along the long axis of the part rather than perpendicular to it. For most upper extremity projections, the CR should be directed perpendicular to the part and the IR to minimize both forms of distortion. Exceptions include specific projections—such as the tangential carpal tunnel view—where intentional CR angulation is used to project structures free of superimposition.

The ARRT examination requires competence in numerous standard and special projections for each region of the upper extremity. The following table summarizes the most frequently tested projections, including patient position, central ray direction, and primary evaluation criteria. Mastery of this information is essential for both the registry examination and clinical practice.

Several clinical pearls relate directly to the projections shown. For the PA hand, having the patient slightly flex the fingers at the MCP joints helps flatten the palm against the IR, preventing the metacarpal heads from lifting off the cassette and creating an oblique rather than true PA projection. For the oblique, a 45° foam step sponge beneath the fingers maintains consistent rotation across patients. For the lateral hand, the fan lateral (fingers extended and separated in a fan-like pattern) is preferred for demonstrating foreign bodies, while the standard lateral (fingers superimposed) better demonstrates anterior or posterior displacement of fracture fragments.

A critical skill for radiographers is the ability to evaluate a completed radiograph, identify positioning errors, and determine the corrective action needed. The following worked example walks through a systematic image critique of an AP elbow radiograph that demonstrates common positioning errors.

Radiographic positioning of the upper extremity is highly effective for demonstrating osseous anatomy, joint alignment, and many soft tissue abnormalities. However, it does have inherent limitations, and certain common errors can compromise diagnostic quality. Understanding both aspects is essential for clinical competence and ARRT exam readiness.

Frequent Positioning Errors

• Forearm pronation on AP projections: When the forearm is pronated for an AP view, the radius crosses over the ulna, causing overlap of the proximal shafts and obscuring the radial tuberosity. Always confirm full supination by palpating the epicondyles.
• Wrist not flat for PA projection: If the fingers are extended stiffly, the wrist arches off the IR, creating OID and distorting carpal anatomy. Instructing the patient to make a gentle fist or slightly flex the fingers brings the wrist flat.
• Elbow flexion >90° on lateral: Hyperflexion beyond 90° displaces the olecranon, disrupting the normal three-concentric-arc appearance used to verify a true lateral position.
• Shoulder rotation errors: Failing to externally rotate the arm for an AP shoulder in external rotation results in the greater tubercle being projected medially, simulating a Hill-Sachs defect or obscuring the lateral humeral cortex.

Standard upper extremity projections provide the diagnostic foundation, but special projections and advanced imaging modalities extend the radiographer's ability to demonstrate specific pathologies. The ARRT examination includes questions on several special projections as well as the radiographer's role in guiding patients toward appropriate advanced studies when plain radiography is insufficient.

Looking forward in your radiography career, understanding these foundational positioning principles will inform your work in cross-sectional imaging. CT technologists, for example, must understand the relationship between patient positioning and the scan plane to produce optimal multiplanar reconstructions of upper extremity fractures. Fluoroscopic procedures such as arthrography demand real-time positioning adjustments. Even interventional radiology procedures on the upper extremity (e.g., embolization of arteriovenous malformations) require the technologist to position the C-arm using the same perpendicular-to-part and minimize-OID principles learned in plain radiography. Mastery of these fundamentals establishes the cognitive framework for all subsequent imaging modalities.