The document provides details on the anatomy of the wrist and carpal bones. It can be summarized as: 1. The wrist joint is made up of the distal ends of the radius and ulna articulating with the proximal and distal rows of carpal bones, which then articulate with the metacarpal bones. 2. The carpal bones are arranged in two rows - the proximal row includes the scaphoid, lunate, triquetrum, and pisiform bones. The distal row includes the trapezium, trapezoid, capitate, and hamate bones. 3. The carpal bones are stabilized by intrinsic and extrinsic ligaments including the scapholunate and

1. Anatomy of wrist & carpal
bones

2. Osseous anatomy
• The distal ends of the radius and ulna
articulate with the two carpal rows (proximal
and distal), and these articulate with the bases
of the five metacarpal bones .

4. • The proximal row of carpal bones termed as
intercalated segment because forces acting on
its proximal & distal articulations determine
its position

5. CARPAL BONES
Carpal bones are arranged in two rows
From lateral to medial and when viewed
from anteriorly
• PROXIMAL ROW
1. the boat-shaped scaphoid;
2. the lunate, which has a 'crescent shape';
3. the three-sided triquetrum bone;
4. the pea-shaped pisiform
• DISTAL ROW
1. the irregular four-sided trapezium bone;
2. the four-sided trapezoid;
3. the capitate, which has a head;
4. the hamate, which has a hook

6. General Features of Carpal Bones
• 1. The proximal row is convex proximally, and concave
distally.
2. The distal row is convex proximally and flat distally.
3. Each bone has 6 surfaces:
(i) The palmar and dorsal surfaces are non-articular
except for the triquetral and pisiform.
(ii) The lateral surfaces of the two lateral bones
(scaphoid and trapezium) are nonarticular.
(iii) The medial surfaces of the three medial bones
(triquetral, pisiform and hamate) are nonarticular.
• 4. The dorsal nonarticular surface is always larger than
the palmar nonarticular surface, except for the lunate,
in which the palmar surface is larger than the dorsal

7. Articular Compartmental Anatomy
• The wrist joint is separated into a number of
compartments by the many ligaments that
attach to the carpal bones
• These compartments are of considerable
significance for the interpretation of standard
or MR arthrograms and for identifying various
patterns of arthritic involvement

8. • The compartments are as follows:
• 1. Radiocarpal compartment
• 2. Midcarpal compartment
• 3. Pisiform-triquetral compartment
• 4. Common carpometacarpal compartment
• 5. First carpometacarpal compartment
• 6. Intermetacarpal compartments
• 7. Inferior (distal) radioulnar compartment

10. Ligamentous anatomy
• Two categories - Intrinsic
- Extrinsic

12. • Intrinsic ligaments
- Scapho-lunate interosseous ligament
- Luno-triquetral interosseous ligament

13. • Scapholunate interosseous ligament ( SLIL ) :
• C shaped structure
• 3 parts - dorsal
- proximal
- volar

14. • Dorsal part – 3mm thick, transverse or short
oblique fibers
• located in the depth of the dorsal capsule and
connects the dorsal-distal corners of the
scaphoid and lunate bones.
• Plays a key role in scapholunate stability.

15. • Volar part- has longer, more obliquely
oriented fibers
• allowing substantial sagittal rotation of the
scaphoid relative to the lunate
• playing a lesser role in carpal stability
• Proximal part – thin, fibrocartilagenous
• Follows the arc of the proximal edges of the
two bones from dorsal to palmar
• separating the radiocarpal and midcarpal
jointspaces

17. • Lunate Triquetrum Interosseous Ligaments :
• Three components- palmar, dorsal & proximal
• In contrast to the scapholunate ligaments, the
palmar lunate triquetrum ligament is thicker
and stronger than the dorsal one

19. Extrinsic ligaments
• Subdivided into three major subgroups
- palmar radiocarpal
- palmar ulnocarpal
- dorsal radiocarpal

20. • Palmar radio-carpal ligaments :
• Four palmar ligaments connect the radius to
the carpus:
-radio-scapholunate
-radio-scaphoid-capitate
- long radio-lunate
-short radio-lunate ligaments

22. • The first three ligaments originate from the
lateral third of the palmar margin of the distal
radius and take an oblique course to insert
into the scaphoid tuberosity &
lunate(radioscapholunate), the palmar aspect
of the capitate (radioscaphoid-capitate), and
the lunate (long radiolunate).
• The short radiolunate ligament originates
from the medial anterior rim of the radius and
has a vertical direction until it inserts into the
palmar aspect of the lunate

23. • The radioscaphoid-capitate ligament courses
around the palmar concavity ofthe scaphoid,
forming a hinge over which the scaphoid
rotates.
• Between the two diverging radioscaphoid-
capitate and long radiolunate ligaments, there
is the so-called interligamentous sulcus (space
of Poirier), which represents a weak zone
through which perilunate dislocations
frequently occur

24. Palmar Ulnocarpal Ligaments
• Superficial extrinsic ulnar-capitate
• Ulnar-triquetrum
• Ulnar-lunate
• Volar radioulnar

26. Dorsal Radiocarpal Ligaments
• The only dorsal extrinsic radiocarpal ligament
is the dorsal radial triquetrum ligament, also
known as the dorsal radiocarpal ligament
• this is a wide, fan-shaped ligament that
connects the dorsal edge of the distal articular
surface of the radius to the dorsal rim of the
triquetrum, with some deep fibers inserting
onto the lunate, and rarely onto the scaphoid.

28. Midcarpal Ligaments
• Dorsal – dorsal intercarpal ligament
• Palmar –
• lateral group - scapho-trapezium-trapezoid
- scapho-capitate
- capitate-trapezium
• Medial group - triquetro-capitate
- triquetro-hamate
- palmar scaphotriquetrum
Lateral group are important in maintaining of
normal scaphoid alignment

30. • Dorsal intercarpal ligament-
• arises from the dorsal ridge of the triquetrum
• courses transversely along the distal edge of
the lunate
• fans out to insert on the dorsal rim of the
scaphoid the trapezium, and the trapezoid
bones
• contributes to increase the depth of the
midcarpal socket
• having a stabilizing role to the lunocapitate
joint

31. Vascularity of the Wrist
• The blood supply to the wrist is provided by
an extrinsic and an intrinsic vascular system
• The extrinsic blood supply is developed
through branches of the radial, ulnar, and
anterior interosseous arteries, which form an
arcade of anastomosing branches that
produce three dorsal and three palmar arches

32. • The dorsal and palmar radiocarpal arches
• The dorsal and palmar intercarpal arches
• The dorsal basal metacarpal and the deep
palmar arches

34. • Panagis et al. and Gelberman and Gross classified
the carpal bones into three groups on the basis of
• the number and location of nutrient vessels,
• the presence or absence of intraosseous
anastomoses
• and the dependence of large areas of bone on a
single vessel.
• The clinical significance of the various groups is
based on the risk of posttraumatic avascular
necrosis for the bones in each group

35. • Group I - Includes carpal bones which either
have vessels entering from only one surface or
• large areas of bone that are dependent on a
single vessel.
• This group is the most vulnerable to
posttraumatic avascular necrosis.
• Scaphoid, Capitate, and 8 % or 20 % of the
lunates

36. • Group II - two or more areas of vessel entry
but lack significant anastomoses within the
entire or a major part of the bones.
• Hamate, Trapezoid

37. • Group III - two or more areas of vessel entry
and consistent intraosseous anastomoses.
• Trapezium, triquetrum , pisiform, and 80 % or
92 % of the lunates

38. Innervation of wrist ligaments
• The main innervation to the wrist capsule derives from
• the anterior interosseous nerve,
• lateral antebrachial cutaneous nerve, and
• Posterior interosseous nerve.
• Other minor sources of capsular innervation include:
• The palmar cutaneous branch of the median nerve,
• The deep branch of the ulnar nerve,
• The superficial branch of the radial nerve, and
• The dorsal branch of the ulnar nerve

39. BIOMECHANICS
• The proximal carpal row has no direct tendon
attachments. The moment generated by
muscle contraction results in rotation that is
initiated at the distal carpal row.
• The bones of the proximal row follow
passively, when tension within the midcarpal
capsule reaches a certain level

40. • In kinematic terms, the distal carpal row can
be thought of as one rigid functional unit.
• The bones of the proximal carpal row seem to
be less tightly bound to one another than the
bones of the distal carpal row

41. • When the wrist is constrained along the sagittal
plane, the scaphoid has a larger amount of
rotation (average 90% of the total arc of motion)
than the lunate (50%) and the triquetrum (65%).
• The average scapholunate angle is 76 degrees in
full wrist flexion and 35 degrees in full extension.
• During radioulnar deviation of the wrist, the
three proximal carpal bones move synergistically
from a flexed position in radial deviation to an
extended position in ulnar deviation

42. • During unconstrained flexion of the wrist, the
distal row synchronously rotates into flexion,
but also into some degree of ulnar deviation.
• In contrast, during wrist extension, the
tendency of all distal carpal bones is to rotate
into extension and a slight radial deviation.

45. • It is widely accepted that the ligamentous
restraints stabilizing the scaphoid are
classified into primary and secondary

46. • Primary stabilizers – scapho-lunate
interosseous ligament
• Secondary stabilizers- STT, RSC, SC, and the
unique V-arrangement of the DIC and DRC
ligaments

47. • Primary rupture secondary intact -Such cases
manifest with SL dissociation without rotary
subluxation of the scaphoid (RSS) (widening of
the SL space, rupture of the dorsal SL
ligament, and normal SL angle)
• Primary intact secondary rupture - Such cases
manifest with RSS without SL dissociation
(foreshortened scaphoid on posteroanterior
radiographs with a positive ring sign,
increased SL angle, and the dorsal SL ligament
macroscopically intact)

48. • Biomechanic concepts that have been proposed for
better understanding of functioning,movements and
various types of forces acting.some of them are:
1. LINK CONCEPT
2. NAVARRO THREE COLUMN CONCEPT
3. ROWS CONCEPT
4. TALEISNIK’S CONCEPT
5. LICHTMAN’S RING CONCEPT
6. WEBER’S TWO COLUMN CONCEPT

49. LINK CONCEPT
• three links in a chain
composed of radius,
lunate and capitate
– head of capitate acts as
center of rotation
– proximal row (lunate)
acts as a unit and is an
intercalated segment
with no direct tendon
attachments
– distal row functions as
unit

50. 3 COLUMN CONCEPT (Navarro 1935)
• lateral (mobile) column
– comprises scaphoid, trapezoid and trapezium
– scaphoid is center of motion and function is
mobile
• central (flexion-extension) column
– comprises lunate, capitate and hamate
– luno-capitate articulation is center of motion
– motion is flexion/extension
• medial (rotation) column
– comprises triquetrum and pisiform
– motion is rotation

51. ROWS CONCEPT (Johnston 1907)
• comprises proximal and
distal rows
– scaphoid is a bridge
between rows
• motion occurs within
and between rows

52. TALEISNIK’S CONCEPT
• Modification of the
columnar theory
• The pisiform does not
function as a carpal
bone, so it is excluded
from the model.
• Trapezium and
trapezoid are part of
the central column

53. WEBER’S TWO COLUMN CONCEPT
• Weber (1980): Two columns are the load-
bearing column (capitate, trapezoid, scaphoid,
and lunate) and
• the control column (triquetrum and hamate).

54. LICHTMAN’S RING CONCEPT
• proximal and distal rows are semirigid posts
stabilized by interosseous ligaments;
• Normal controlled mobility occurs at
scaphotrapezial and triquetrohamate joints.
• Any break in ring, either bony or ligamentous
(arrows), can produce dorsal intercalated
segmental instability or volar intercalated
segmental instability deformity.

56. Craigen and Stanley (1995)
• There are two patterns of motion during
radioulnar deviation:
• the proximal row rotates mostly along the
frontal plane (row pattern) or mostly along
the sagittal plane (column pattern).

57. Stabilizing Mechanism of the Distal
Row
• Tendons included in the carpal tunnel have divergent
directions when they emerge in the palm.
• If their corresponding muscles contract, the flexor
tendons of the little finger generate a compressive
force to the hook of the hamate toward the ulnar side.
• This force would be opposite in direction to the force
that is generated when the flexor pollicis longus
contracts against the inner surface of the trapezium.
• Such opposite forces would tend to open the palmar
carpal concavity (the trapezium toward the radial side,
the hamate toward the ulnar side).

58. Stabilizing Mechanism of the
Midcarpal Joint
• Under axial load, the distal carpal row exerts an axial
compressive force onto the proximal row.
• Because of its oblique orientation relative to the long
axis of the forearm, the loaded scaphoid tends to
rotate into flexion and pronation.
• If the scapholunate and lunate triquetrum interosseous
• ligaments are intact, the flexion moment generated by
the scaphoid is transmitted to the lunate and the
triquetrum.
• Consequently, the unconstrained proximal row would
rotate into flexion

59. • Especially important midcarpal stabilizers are the
STT and scaphoid capitate ligaments laterally
andtriquetrum-hamate-capitate ligament (the so-
called ulnar leg of the arcuate ligament) medially.
• Failure of these ligaments results in a typical
carpal collapse characterized by abnormal flexion
of the unconstrained proximal row, a fairly typical
pattern of carpal malalignment, known as volar
intercalated segment instability (VISI)

60. Stabilizing Mechanism of the Proximal
Row
• When axially loaded, the three proximal bones are not
equally constrained by the palmar-crossing midcarpal
ligaments.
• Because of the peculiar arrangement of the STT and
scaphoid capitate ligaments, the scaphoid is allowed larger
rotation into flexion and pronation than the lunate,
whereas the triquetrum is tightly constrained by its
attachments to the distal row.
• If palmar and dorsal scapholunate and lunate
• triquetrum ligaments are intact, such differences in angular
rotation are likely to generate increasing torque and
intercarpal coaptation of the scapholunate and lunate
triquetrum joints, contributing further to their stability

61. • . If the scapholunate ligaments are completely
torn, the scaphoid no longer is constrained by the
rest of the proximal row and tends to collapse
into an abnormally flexed and pronated posture
(the so-called rotatory subluxation of the
scaphoid)
• whereas the lunate and triquetrum are pushed by
the distal row into an abnormal extension, known
as a dorsal intercalated segment instability (DISI

62. • If, instead of the scapholunate, the lunate
triquetrum ligaments fail, the scaphoid
• and lunate tend to adopt an abnormal flexed
posture (VISI), whereas the triquetrum
remains solidly linked to the distal row