Imaging Anatomy of the Wrist

IMAGING ANATOMY OF THE WRIST

25 May 2012Dept. of Diagnostic Radiology UFSM. Pieters

THE WRIST

Osseous structures

Ligaments

Tendons

Neurovascular structures

Anatomical variants

OSSEOUS STRUCTURES

TrapezoidTrapeziumCapitate

Scaphoid

Radius

Hook of HamateHamatePisiform

Lunate

Ulna

Triquetrum

OSSEOUS STRUCTURES

OSSEOUS STRUCTURES

Lateral radiograph obtained in zero-rotation position. Note theposition of the pisiform overlying the mid waist of the scaphoid indicates a properly positioned lateral

CARPAL BONE OSSIFICATION

The capitate ossifies first and the pisiform lastBut the order and timing of the ossification of the other bones is variable

Excluding the pisiform, they ossify in a clockwise direction from capitate to trapezoid as follows:

CapitateHamate

Triquetral at 3 yearsLunate bone at 5 yearsScaphoid, trapezium and trapezoid at 6 years

The pisiform ossifies at 11 years of age

at 4 months

SUPERNUMERY BONES

COMPARTMENTS

COMPARTMENTS, JOINTS AND LIGAMENTS

The midcarpal and radiocarpal joint are seperated by interosseous ligamentsNo communicationComplex palmar and dorsal ligaments provide supportArthrogaphy – ideally conducted in 3 stages

LIGAMENTS - DORSAL

LIGAMENTS - VOLAR

OSSEOUS STRUCTURES - JOINTS

• Distal (inferior) radioulnar joint:

Pivot joint; ROM: Distal radius rotates around distal ulna

• Radiocarpal joint:

Ellipsoid joint created by proximal carpal row articulating with distal radius & ulna ROM:Flexion, extension, abduction, adduction,circumduction, no rotation


• Pisotriquetral:

Gliding joint created by pisiform and triquetrum; Discretely separate from radiocarpal joint in 10-25%; ROM: Minimal

• Midcarpal:

Gliding joint created by articulation ofproximal & distal carpal rows

ROM: Some extension, abduction, minimal rotation


• Intercarpal:

Gliding joints created by interface of individual carpal bones ROM: Complex

• Carpometacarpal

- First CMC (thumb base): Saddle joint, highlymobile; ROM: Flexion, extension, abduction,adduction, circumduction, rotation, opposition

- Intermetacarpals 2nd-5th: Gliding joints; ROM:Limited mobility of 2nd & 3rd CMC, increasingmobility of 4th & 5th CMC

ARTHROGRAPHY

• Good evaluation for integrity of scapho-lunate, lunotriquetral ligaments & TFC

• Limited value for extrinsic ligaments• Injections spaced to allow contrast resorption• Radiocarpal joint injected first (most likely to document with single

injection);

• If no tear, wait 30-60 minutes & proceed sequentially with distal radio-ulnar and midcarpal injection

• Digital subtraction allows dynamic evaluation of ligament status and sequential compartment injection without delay

• Injectate: Iodinated contrast (180-300 mg I/ml);• Volumes: Midcarpal, 4-5 cc; radiocarpal, 2-3 cc; DRU, 1-2 cc; pisotriquetral,

1-2 cc

ARTHROGRAMS

ARTHROGRAMS

Intact radiocarpal compartment - contrast filling pisotriquetral joint via prestyloid recess. Triangular fibrocartilage distal surface is outlined.

Scapholunate & lunotriquetral ligaments are intact, with no evidence of spill

into midcarpal joint.

ARTHROGRAMS

RADIOGRAPHIC MEASUREMENTS

Radial tilt

The normal distal radius angulation

Normal = 16-28’

Abn = fracture likely


Lunate overhang:

At least 50% of the lunate articular surface should articulate with the radial articular surface


• Ulnar variance refers to length of distal ulna relative to distal radius

• Ulnar minus: Ulna> 2 mm shorter than radius• Ulnar plus: ulna longer than radius

TENDONS

TENDONS - VOLAR

TENDONS - DORSAL

TENDON SHEATHS - DORSAL

TENDON SHEATHS - VOLAR

Volar bursae: Ulnar and radial sheathsCommon flexor tendon sheath encases – index, middle, ring and little finger tendonsFlexor pollics longs has a separate sheath

TENDONS - CARPAL TUNNEL

CARPAL TUNNEL - MARGINS

Margins:

• Dorsal margin = carpals• Volar margin = flexor retinaculum • Medial margin = pisiform & hook of the hamate • Lateral margin scaphoid & trapezium• Proximal margin = radiocarpal joint • Distal margin = MC base

Contents:

• Flexor digitorum superficialis• Flexor digitorum profundus• Median nerve

TENDONS - CARPAL TUNNEL

GUYON CANAL

GUYON CANAL

Margins:

Ventral margin = Superficial flexor retinaculumMedian margin = Pisiform and Flexor carpi ulnarisDorsolateral margin = Deep flexor retinaculum

Contents:

Ulnar artery & vein, Ulnar nerve

TENDONS – ANATOMICAL SNUFF BOX

TENDONS – ANATOMICAL SNUFF BOX

Margins:

• Distal radius (proximal margin)• Extensor pollicus longus (dorsal margin)• Adductor pollicus longus & Extensor pollicus brevis (volar margin)• APL & EPB converge just distal to 1st CMC (distal margin)• scaphoid, trapezium, 1st CMC & radial styloid (deep margin)

Contents:

• Cephalic vein• radial nerve• radial artery

TRIANGULAR FIBRO-CARTILIGINOUS COMPLEX

The term "triangular fibrocartilage complex of the wrist" was first coined by Palmer and Werner in 1981,1

Describes the cartilaginous and ligamentous structures that bridge the distal radius and ulna,

Provides articulation with the adjacent lunate and triquetrum.

Important stabilizer of the distal radioulnar joint

Provides important shock absorption to the carpus.

TFCC

The components of the TFCC include:

The articular disc The dorsal and volar radioulnar ligaments The meniscus homologue The extensor carpi ulnaris tendon sheath The ulnocarpal ligaments

TFCC

It is the articular disc and the radioulnar ligaments that are the most important to evaluate.

Characteristic triangular shape

The articular disc may be only 1-2 millimeters thick within its central portion, but the TFC thickens considerably at its dorsal and volar aspects, as well as at the ulnar attachments.

The thickened dorsal and volar components are what comprise the dorsal and volar radioulnar ligaments.

TFC

A 3D depiction of the TFC (arrow) demonstrates its triangular shape and relatively thin central region.

Viewed from above, the thickened peripheral components that represent the dorsal and volar radioulnar ligaments (arrows) are readily apparent.

NORMAL TFC

A T1-weighted coronal image demonstrates a normal TFC. Normal intermediate signal intensity is evident at the ulnar attachment (arrow). The normal interface with articular cartilage at the radial side is also apparent (arrowhead), and should not be mistaken for a vertical tear.

TFCC – VERTICAL TFCC TEAR

TFCC – MRI

• Injuries to the TFCC are a frequent cause of ulnar sided wrist pain.

• MRI allows accurate pre-treatment evaluation of patients with suspected TFCC pathology

• Provides excellent characterization of TFCC tears and their associated wrist pathology.

• Such information is invaluable for the proper management of patients with TFCC tears.

NEUROVASCULAR STRUCTURES


Dorsal


Radial artery

Origin:

• Terminal branch of brachial artery

Course:

• Superficial to pronator quadratus• Continues dorsally around radial styloid process• Passes deep to APL & EPB• Across anatomic snuffbox & deep to EPL


Radial artery

Branches:

• Palmar carpal branch • Superficial palmar branch• Superficial palmar branch• Main radial artery• Dorsal carpal branch • Deep palmar arch• Small dorsal branch • radiocarpal artery


Ulnar artery:

Course in wrist:

• Superficial to pronator quadratus • Continues between FCU & FDS tendons

Branches:

• Common interosseous • Anterior interosseous • Posterior interosseous artery • Palmar carpal branch• Dorsal carpal branch • Deep palmar branch• Superficial palmar branch


Ulnar nerve:

Origin: Brachial plexus-medial cord

Course in wrist: • Radial to FCU, close to ulnar artery• At proximal pisiform: Nerve proximal to bifurcation; nerve deep to

FCU, ulnar to ulnar artery & veins

• At distal pisiform: Nerve bifurcates into deep (motor) & superficial (sensory) branches

• At hook of hamate: Superficial branches volar to hook of hamate & ADM; nerve ulnar to ulnar artery & veins; deep branches are dorsal & ulnar to hook of hamate, deep to abductor digiti minimi, superficial to pisometacarpal ligament

NEUROVASCULAR STRUCTURESRadial nerve

Origin: Brachial plexus-posterior cordCourse in wrist: Branches into superficial & deep branches in distal forearm

- Branches:• Superficial branch passes under brachioradialis tendon into dorsal wrist; divides into lateral branch (supplies radial wrist & thumb skin) & medial branch (supplies mid & ulnar wrist skin); divides to dorsal digital nerves supplying ulnarthumb, index, middle & radial ring fingers

• Deep branch enters supinator volarly; exitsdistally & posteriorly as posterior interosseousnerve; supplies ECRB, supinator, ED, EDM, ECU,EPL, APL & El

NUTRIENT ARTERIES OF THE SCAPHOID

• In 13% of subjects these enter the scaphoid exclusively in its distal half.

• Fractures across scaphoid midportion - problematic

• The blood supply to the proximal portion is cut off

• Ischaemic necrosis

• Occurs in 50% of patients with displaced scaphoid fractures

AVASCULAR NECROSIS

VASCULAR SUPPLY OF THE LUNATE

The large majority of the lunate is covered with articular cartilage, leaving only small areas accessible to nutrient vessels along the dorsal and volar poles. These "bare areas" correspond to ligamentous insertion sites, and thus trauma may result in avulsion injuries to the entering arteries. Internally, the lunate blood supply forms patterns resembling a Y (59%), an I (31%), or an X (10%).

KIENBOCK’S DISEASE

Diffusely decreased signal intensity is present within the lunate (arrow). Negative ulnar variance with compensatory thickening of the triangular fibrocartilage (arrowhead) is also present.

Diagnosis

Kienbock's Disease (avascular necrosis of the lunate).

Osteonecrosis of the lunateNegative ulnar varianceKienbock

Lateral –lunate osteonecrosis

A FEW ANATOMICAL VARIANTS

Examples from one study:

Hypoplasia of the hook of the hamate bone

Anomalous muscles inside the carpal tunnel

Unusual location and double branching of the median nerve

Aberrant median artery


Accessory abductor digiti minimi


Extensor digitorum brevis manus

BIBLIOGRAPHY

1. Diagnostic and Surgical Imaging Anatomy – Muskuloskeletal – Manaster

2. Applied Radiological Anatomy - Butler

3. Anatomy for Diagnostic Imaging 3rd ed – Ryan

4. Variations of the arterial pattern in the upper limb revisited: a morphological and statistical study, with a review of the literature – Rodrigues et al; J. Anat. (2001) 199, pp. 547±566

5. Accessory Muscles: Anatomy, Symptoms, and Radiologic Evaluation – Sookur et al - RadioGraphics 2008; 28:481–499

6. www.radiopaedia.org

http://www.radiopaedia.org/

Imaging Anatomy of the Wrist

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