1. Imaging Anatomy of the Wrist
25 May 2012
Dept. of Diagnostic Radiology UFS
M. Pieters
Imaging Anatomy of the Wrist

2. The wrist Osseous structures Ligaments Tendons
Neurovascular structures
Anatomical variants

3. Osseous structures Trapezoid Hook of Hamate Trapezium Hamate Capitate
Pisiform
Triquetrum
Scaphoid
Lunate
Radius
Ulna

4. Osseous structures

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

8. Carpal bone ossification
The capitate ossifies first and the pisiform last
But 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:
Capitate
Hamate
Triquetral at 3 years
Lunate bone at 5 years
Scaphoid, trapezium and trapezoid at 6 years
The pisiform ossifies at 11 years of age
at 4 months

9. Supernumery bones
Be sure not to confuse the lanula with a styloid process fracture

11. Compartments
Important because these compartments can point to pathology on arthrography if the ligaments are disrupted. For example: contrast can be injected into the Radiocarpal compartmentand if it spreads into the midcarpal compartment, it can point to fractures etc.

13. Compartments, joints and ligaments
The midcarpal and radiocarpal joint are seperated by interosseous ligaments No communication Complex palmar and dorsal ligaments provide support Arthrogaphy – ideally conducted in 3 stages

14. Ligaments - dorsal

15. Ligaments - volar

16. 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

17. 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 of
proximal & distal carpal rows
ROM: Some extension, abduction, minimal rotation

18. Osseous structures - joints
• Intercarpal:
Gliding joints created by interface of individual carpal bones
ROM: Complex
• Carpometacarpal
- First CMC (thumb base): Saddle joint, highly
mobile; ROM: Flexion, extension, abduction,
adduction, circumduction, rotation, opposition
- Intermetacarpals 2nd-5th: Gliding joints; ROM:
Limited mobility of 2nd & 3rd CMC, increasing
mobility of 4th & 5th CMC

19. 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 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 ( mg I/ml);
Volumes: Midcarpal, 4-5 cc; radiocarpal, 2-3 cc; DRU, 1-2 cc; pisotriquetral, 1-2 cc

20. Arthrograms

21. 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.

22. Arthrograms

23. Radiographic measurements
Radial tilt The normal distal radius angulation Normal = 16-28’ Abn = fracture likely

24. Radiographic measurements
Lunate overhang: At least 50% of the lunate articular surface should articulate with the radial articular surface

25. 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

26. tendons
Talk about infection that can tack from the thumb along the flexor retinaculum.

27. Tendons - volar

28. Tendons - dorsal

29. Tendon sheaths - dorsal
Separate tendon sheaths enclose the extensor tendons in compartment 1 - 6

30. Tendon sheaths - volar
Volar bursae: Ulnar and radial sheaths Common flexor tendon sheath encases – index, middle, ring and little finger tendons Flexor pollics longs has a separate sheath

33. Tendons - Carpal tunnel
Most important: Talk about what’s inside and what’s outside the carpal tunnel. ALSO adda few MRI Pics

34. Carpal tunnel - 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

35. Tendons - Carpal tunnel

36. Guyon canal

37. Guyon canal
Margins: Ventral margin = Superficial flexor retinaculum Median margin = Pisiform and Flexor carpi ulnaris Dorsolateral margin = Deep flexor retinaculum Contents: Ulnar artery & vein, Ulnar nerve

38. Tendons – anatomical snuff box

39. 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

40. 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.

41. 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

42. 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.

43. 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.

44. 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.

45. TFCC – vertical tfcc tear

46. 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.

47. Neurovascular structures

48. Neurovascular structures

49. Neurovascular structures
Dorsal

50. 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

51. Neurovascular structures
Radial artery
Branches:
Palmar carpal branch
Superficial palmar branch
Main radial artery
Dorsal carpal branch
Deep palmar arch
Small dorsal branch
radiocarpal artery

52. 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

53. 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

54. Neurovascular structures
Radial nerve
Origin: Brachial plexus-posterior cord
Course 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 ulnar
thumb, index, middle & radial ring fingers
• Deep branch enters supinator volarly; exits
distally & posteriorly as posterior interosseous
nerve; supplies ECRB, supinator, ED, EDM, ECU,
EPL, APL & El

55. 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

56. Avascular necrosis

57. 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%).

58. 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).

59. Osteonecrosis of the lunate Negative ulnar variance Kienbock

60. Lateral – lunate osteonecrosis

61. 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

62. A few anatomical variants
Accessory abductor digiti minimi

63. A few anatomical variants

64. A few anatomical variants

65. A few anatomical variants
Extensor digitorum brevis manus

66. A few anatomical variants

67. Bibliography
Diagnostic and Surgical Imaging Anatomy – Muskuloskeletal – Manaster
Applied Radiological Anatomy - Butler
Anatomy for Diagnostic Imaging 3rd ed – Ryan
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
Accessory Muscles: Anatomy, Symptoms, and Radiologic Evaluation – Sookur et al - RadioGraphics 2008; 28:481–499