Upper extremity

Upper extremity

Exam category: Procedures → Extremity
Why it matters: The upper limb carries more testable detail than any other region — ten separate anatomic areas, each with a routine series, a part position, a centering point, and an evaluation criterion. On top of that sit the named/eponym views (Stecher, Gaynor-Hart, Coyle, Grashey, Lawrence, Neer), which are the highest-yield trap material here: each exists to solve a specific clinical problem, and the registry tests why that view is chosen, not just its name.

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The big picture (plain English)

Work distal to proximal: fingers → hand → wrist → forearm → elbow → humerus → shoulder → clavicle/AC joints. Routine series for most joints follow the same pattern (AP or PA, lateral, oblique), and the eponym views exist specifically for the cases routine views can't handle — a bone that superimposes on itself, a joint that can't flex enough for a standard oblique, or a specific pathology that needs a specific angle to show.

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1. Hand, wrist, and the scaphoid problem

The eight carpals

The names are easiest to learn as two transverse rows of four. Starting on the lateral (thumb) side each time:

• Proximal row: scaphoid, lunate, triquetrum, pisiform.
• Distal row: trapezium, trapezoid, capitate, hamate.

The scaphoid is the largest bone of the proximal row, articulates with the radius, and is the most frequently fractured carpal — which is why it gets its own projections. The capitate is the largest carpal overall, and the pisiform the smallest. The hamate carries the hooklike hamulus on its palmar surface.

Deviation opens the far side

Bending the wrist toward one side pulls apart the carpals on the opposite side. That single rule covers both deviation projections:

• Ulnar deviation (hand moved toward the little-finger side) opens the carpals on the radial (thumb) side, and best demonstrates the scaphoid there without the foreshortening and overlapping seen on a plain PA. This is the dedicated scaphoid projection, often with the CR angled 10–15° proximally along the forearm.
• Radial deviation (hand moved toward the thumb side) opens and best demonstrates the carpals on the ulnar side — hamate, pisiform, triquetrum, and lunate.

The scaphoid and carpal-canal projections

Routine wrist: PA, lateral, PA oblique. The special views:

• PA axial scaphoid (modified Stecher method) — hand elevated ~20° (or CR angled) to project the scaphoid without foreshortening, since it normally sits at an angle to the IR.
• Carpal canal / tangential (Gaynor-Hart method) — patient hyperextends (dorsiflexes) the wrist, CR angled 25–30° proximally to the long axis of the hand, and the whole hand and wrist rotated about 10° internally so the pisiform and hamate don't superimpose. Used to rule out carpal tunnel syndrome (calcification/bony changes impinging the median nerve) and hamulus/pisiform/trapezium fractures. Never attempt this before a routine wrist series has ruled out fracture — the hyperextension required could displace a fracture. If pain limits how far the wrist can be hyperextended, the total CR angle to the IR must be increased to keep the same relationship between the beam and the carpal sulcus. Less wrist, more angle.

2. Forearm and elbow

Routine: AP, lateral.

Why the forearm is supinated

The forearm is not radiographed pronated. Pronating the hand pivots the radius so it crosses over the ulna in the upper forearm, superimposing the two bones. Radiographing AP with the hand supinated (palm up, anatomic position) keeps the radius and ulna parallel and side by side, which is the whole point of the projection.

What rotation does at the elbow

The same pivot governs the elbow obliques, and the direction decides the outcome:

• AP, no rotation — the proximal radius is superimposed only slightly by the ulna.
• Lateral (external) rotation, 40–45° — separates the radius and ulna. It best visualizes the radial head, neck and tuberosity free of the ulna, with the lateral epicondyle and capitulum elongated and in profile.
• Medial (internal) rotation, 45° (pronated hand) — superimposes them almost completely. It best visualizes the coronoid process of the ulna in profile, with the radial head and neck superimposed over and centered on the proximal ulna.

The fat pads — and the 90° rule that makes them mean anything

The elbow's three fat pads and stripes are visible only on the lateral projection; on the AP they are superimposed over bone.

• Anterior fat pad — a teardrop-shaped lucency just anterior to the distal humerus. Trauma or infection elevates it and distorts its shape.
• Posterior fat pad — lies deep inside the olecranon fossa and is normally not visible on a negative elbow. Joint effusion pushes it out of the fossa, so seeing it on a 90° flexed lateral indicates that something inside the joint has displaced it — a sign of joint pathology. It is considered the more reliable of the two.
• Supinator fat stripe — a long thin stripe just anterior to the proximal radius; displacement can be the only clue to a radial head or neck fracture.

The elbow's special case

• Trauma axial laterals (Coyle method) — used specifically when a patient cannot fully extend the elbow for a standard oblique (common in trauma). Two part positions: radial head (elbow flexed 90°, CR 45° toward the shoulder) and coronoid process (flexed 80°, same CR angle). Solves the same clinical problem two different ways depending on which structure needs to be shown.

3. Humerus and shoulder

The three AP shoulder rotations

Routine shoulder: AP internal/external rotation (non-trauma) or AP neutral (trauma, no rotation attempted). Rotating the arm swings the two tubercles of the proximal humerus around, and each rotation profiles a different one:

The AP humerus uses the same external-rotation logic: abduct the arm slightly and gently supinate the hand so the epicondyles are parallel and equidistant from the IR, with the CR to the midpoint of the humerus.

The eponym views

Three eponym views, each solving a different problem:

4. Clavicle and AC joints

Clavicle: AP or PA, plus an axial projection to project it off the ribs/lung fields.

• AP clavicle — CR perpendicular to the midclavicle.
• AP axial clavicle — CR 15–30° cephalad to the midclavicle. The angle is what lifts most of the clavicle above the scapula and ribs. The angle is chosen by body habitus, not fixed: a thin (asthenic) patient, with little tissue depth to project through, needs the steeper 25–30°; a patient with thick shoulders and a deep chest (hypersthenic) needs only 15–20°.
• PA axial clavicle — the same idea from the front, so the angle reverses to 15–30° caudad.

AC joints: AP bilateral, taken with and without weights — weighted views stress the joint to reveal subtle separations that don't show on an unweighted image. A shoulder or clavicle series should clear a fracture first.

A note on technique for AC joints. Grids generally are not used for body parts measuring 10 cm or less, and AC joints usually measure under 10 cm. So they are commonly done nongrid at a lower kVp (about 70–75) — a thin part throws little scatter, and less kVp gives adequate penetration with better contrast. (Departments vary; a grid raises dose because the exposure factors have to go up with it.)

5. Scapula

The scapula sits behind the ribs, so both routine views are built to get it out from behind them:

• AP scapula — abduct the arm 90° (hand supinated) to draw the scapula laterally, off the posterior ribs. Because the medial scapula still overlaps the thorax, a breathing technique (quiet breathing through a long exposure) blurs the ribs and lung markings so that part shows through.
• Lateral scapula — an anterior oblique that puts the scapula in profile — the same scapular Y body position as the Neer view above. The arm is placed according to the scapular area of interest (the body vs. the acromion and coracoid processes), and the view is used for scapular fractures.

How far to rotate for the scapular Y

Rotate the patient into an anterior oblique until an imaginary line between the superior angle of the scapula and the AC joint is perpendicular to the IR — putting the thin scapular body on end. Because patients differ, the amount of body obliquity ranges from about 45° to 60° from the frontal position. Abduct the arm slightly so the proximal humerus doesn't superimpose the ribs, but do not rotate the arm.

Reading a scapular Y

The acromion and coracoid processes form the two upper limbs of the Y, the scapular body the leg, and the glenoid cavity sits at the junction where they converge.

• Not dislocated — the humeral head is superimposed over the base of the Y (the glenoid).
• Anterior dislocation (much the more common) — the head is thrown forward and down, beneath the coracoid process.
• Posterior dislocation — the head sits beneath the acromion process.

6. The routine series — how the part is placed, where to center, and how you know it's right

Everything above is the exception list. This is what the exceptions are exceptions to: the routine series for each part, how the part physically goes down on the receptor, the centering point the beam goes to, and the evaluation criteria — the specific finding on the finished image that proves you positioned it correctly. The registry tests all four directly.

How the part is placed

Where to center

Two patterns make the centering column memorable instead of seven separate facts. For the digits and hand, the CR goes to a joint named by the part — PIP for a finger, first MCP for the thumb, third MCP for the whole hand. For the long bones, it goes to the middle of the bone — mid-forearm, mid-humerus. The wrist and elbow are the two that need their own answer: midcarpal area, and the mid-elbow joint 2 cm distal to the interepicondylar midpoint.

How you know it's right

7. The injury names you're expected to know

The registry tests upper-limb pathology and terminology alongside positioning, because the requisition often names the injury rather than the projection. These are the named ones, sorted by where they happen:

8. Bone age

A bone age study asks how mature a child's skeleton is — for growth potential, and because malnutrition and endocrine and non-endocrine disorders can delay bone growth. The most common image evaluated is a single PA of the left hand and wrist, because the hand and wrist ossify on a fairly consistent schedule with many centers to read at once.

Two methods for turning that image into an age:

• Greulich-Pyle (GP) — compares the overall radiographic appearance of the hand and wrist against standard images in a reference atlas (the Radiographic Atlas of Skeletal Development of the Hand and Wrist), and takes the closest match. This is the most common method radiologists use.
• Tanner-Whitehouse (TW) — assigns a numeric value to specific areas of the hand and sums them into an overall score, which converts to an age. More accurate, but it takes considerably longer, so it is not the predominant method.

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Registry must-know facts

• Routine CR centering: finger → PIP joint; thumb → first MCP; hand → third MCP; wrist → midcarpal area; forearm → mid-forearm; elbow → mid-elbow joint (¾ inch/2 cm distal to the interepicondylar midpoint); humerus → midpoint of the humerus.
• Evaluation criteria: PA hand/wrist → equal concavity of the proximal metacarpal shafts; PA oblique hand at 45° → metacarpal midshafts not overlapping (excess overlap = over-rotation, excess separation = under-rotation); lateral wrist → ulnar head superimposed over the distal radius; AP forearm and AP elbow → epicondyles in profile; lateral elbow at 90° → three concentric arcs (trochlear sulcus, outer ridges of capitulum and trochlea, trochlear notch of the ulna).
• Hand and wrist obliques rotate laterally (toward the thumb) 45°, not medially.
• A complete forearm (and humerus) image must include both adjacent joints.
• Scaphoid: modified Stecher method for the PA axial view; carpal canal (Gaynor-Hart) for tunnel syndrome — always after a fracture-clearing series, never before.
• Coyle method exists specifically for elbows that can't extend enough for a standard oblique — two part positions, radial head vs. coronoid process.
• Grashey opens the glenohumeral joint (35-45° rotation toward affected side); Lawrence needs arm abduction (contraindicated if fracture suspected). The scapular Y and Neer are the trauma-safe alternatives — same anterior-oblique body position, no arm rotation; Neer adds a 10–15° caudal CR and is the one that demonstrates the coracoacromial arch for impingement.
• On a scapular Y, the humeral head sits over the base of the Y when there's no dislocation — beneath the coracoid on an anterior dislocation, beneath the acromion on a posterior one. Body obliquity for the Y runs about 45–60°.
• AC joints are imaged bilaterally, with and without weights, specifically to stress-test for separation. They usually measure under 10 cm, so they are commonly done nongrid at 70–75 kVp — grids generally aren't used for parts of 10 cm or less.
• The AP axial clavicle angles 15–30° cephalad, and the amount depends on habitus: asthenic 25–30°, hypersthenic 15–20°. The PA axial reverses it to caudad.
• Part positions to have cold: PA finger = palmar surface down; lateral finger = thumb side up, unaffected digits flexed away, ulnar surface down (lateromedial) — but the index finger reverses, so its radial surface touches the IR (mediolateral); AP thumb = hand rotated internally until the dorsal thumb is on the IR; PA hand = pronated, fingers slightly spread; fan lateral = digits spread and parallel, the preferred lateral when the phalanges matter; lateral hand in extension = the alternative for foreign-body localization; lateral wrist = elbow flexed 90°, ulnar side down, thumb up; AP forearm and AP humerus = supinated with the epicondyles parallel to the IR.
• Carpals = two rows of four: proximal (scaphoid, lunate, triquetrum, pisiform), distal (trapezium, trapezoid, capitate, hamate). Deviation opens the opposite side — ulnar deviation for the scaphoid, radial deviation for the hamate, pisiform, triquetrum and lunate.
• On the carpal canal, less hyperextension means MORE CR angle, not less.
• A PA wrist is neutral (no deviation) when the long axes of the third metacarpal and midforearm are aligned.
• The forearm is imaged supinated because pronation makes the radius cross over the ulna. At the elbow, the same pivot means lateral (external) rotation separates the radius and ulna and medial (internal) rotation superimposes them.
• The posterior fat pad is normally hidden in the olecranon fossa; seeing it on a 90°-flexed lateral suggests joint pathology. Extend past 90° and the olecranon elevates it by itself — the sign then means nothing.
• AP shoulder rotations: external → greater tubercle in profile laterally (epicondyles parallel, the AP of the proximal humerus); internal → lesser tubercle in profile medially (epicondyles perpendicular, the lateral); neutral → both tubercles superimposed, the trauma projection where no rotation is attempted.
• Injury names: skier's thumb = ulnar collateral ligament at the first MCP; Bennett = base of the first metacarpal into the CMC joint; boxer = neck of the fifth metacarpal; mallet/baseball = distal phalanx, avulsion at its posterior base; Colles = distal radius displaced posteriorly, Smith the reverse (anteriorly); Barton = posterior lip of the distal radius with dislocation; Hutchinson/chauffeur = radial styloid; Monteggia = proximal ulna plus radial head dislocation.
• Bone age: a PA of the left hand and wrist. Greulich-Pyle matches the image to an atlas (most common); Tanner-Whitehouse scores individual bones and sums them.
• Scapula: AP with the arm abducted 90° (draws it laterally off the ribs) plus a breathing technique to blur the ribs over the medial scapula; lateral scapula = an anterior oblique in the scapular Y position (like Neer), arm placed per the area of interest, for scapular fractures.

Common trap

Questions test why an eponym view is chosen, not just its name — e.g. picking Lawrence for a suspected shoulder dislocation would be actively contraindicated (it requires abduction), when Neer is the trauma-safe choice for exactly that scenario.

A second family of traps runs on direction, where both options are real and only one is right for the question asked: ulnar vs. radial deviation, external vs. internal shoulder rotation, cephalad vs. caudad on the clavicle, Colles vs. Smith, coracoid vs. acromion on a scapular Y, and "more angle" vs. "less angle" when a patient can't hyperextend for the carpal canal. In each pair, work from the underlying reason rather than trying to memorize which is which — deviation opens the far side, the rotation profiles the tubercle it swings outward, and lost patient motion is made up with added central-ray angle.

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Source: Bontrager, Textbook of Radiographic Positioning and Related Anatomy, 10th ed., Ch. 4-5, with the fracture terminology from Ch. 15 and the bone age methods from Ch. 16; McQuillen Martensen, Radiographic Image Analysis, 6th ed., Ch. 4-5 for the lateral-wrist part position, the third-metacarpal/midforearm neutrality criterion, and the coracoid/acromion reading of a scapular Y dislocation. Named views cross-checked against the current ARRT spec's Attachment A view list — all confirmed present. Part positions, routine CR centering points and evaluation criteria (section 6) are taken from the per-projection "Part Position", "CR" and "Evaluation Criteria" entries rather than summarized from memory.