imaging anatomy of the wrist
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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
OSSEOUS STRUCTURES - JOINTS
• 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
OSSEOUS STRUCTURES - JOINTS
• 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
RADIOGRAPHIC MEASUREMENTS
Lunate overhang:
At least 50% of the lunate articular surface should articulate with the radial articular surface
RADIOGRAPHIC MEASUREMENTS
• 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
NEUROVASCULAR STRUCTURES
NEUROVASCULAR STRUCTURES
Dorsal
NEUROVASCULAR STRUCTURES
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
NEUROVASCULAR STRUCTURES
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
NEUROVASCULAR STRUCTURES
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
NEUROVASCULAR STRUCTURES
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
A FEW ANATOMICAL VARIANTS
Accessory abductor digiti minimi
A FEW ANATOMICAL VARIANTS
A FEW ANATOMICAL VARIANTS
A FEW ANATOMICAL VARIANTS
Extensor digitorum brevis manus
A FEW ANATOMICAL VARIANTS
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
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