Four-dimensional CT can be used to evaluate dynamic wrist instabilities. It allows visualization of carpal kinematics during various wrist motions like flexion-extension and dart throwing. This helps characterize patterns of non-dissociative carpal clunking and differentiate partial from complete tears of the scapholunate ligament, improving diagnosis of wrist instability types.

1. Four-Dimensional Computed Tomography
Imaging of the Wrist
A Novel Technique to Evaluate Dynamic
Instabilities
Marc Garcia-Elias MD Josep Monill MD ; Xavier Alomar MD
Institut Kaplan, Barcelona, Spain Creu Blanca, Barcelona, Spain

2. Technical parameters in 320-MDCT
arpal Aquilion One, Toshiba Medical Systems
kinematics
0.5 mm detectors- 16 cm of z-axis volume
Gantry rotation time: 350 milliseconds
FLEXION - EXTENSION
Minimum temporal resolution: 175 milliseconds
RADIAL INCLINATION - ULNAR INCLINATION
 100 kVp-80 mA
ULNAR FLEXION - RADIAL EXTENSION
(DART-THROWING)
14 image series obtained for 14 seconds
RADIAL FLEXION – ULNAR EXTENSION
DLP 240mGy. cm

3. Y’
RADIAL
CUBITAL INCL.
X X’
FLEXION-
EXTENSION
Y

4. Carpal kinematics ECRL
ULNAR FLEXION –
RADIAL EXTENSIÓN
DART-THROWING
FLEXION - EXTENSION
RADIAL INCLINATION - ULNAR INCLINATION
ULNAR FLEXION - RADIAL EXTENSION
RADIAL FLEXION - ULNAR EXTENSION
FCU

5. The proximal row hasn´t
tendinous attachments
The movement always
begins in the distal row
The fibers of midcarpal
Flexion
ligaments increase in Neutral Extension
tension
The forces of compression
generated on the bone
force it to move
In the central movements the
radiocarpal joint is slightly active

6. RADIAL INCLINATION ULNAR INCLINATION
Carpal kinematics
FLEXION EXTENSION
FLEXION - EXTENSION
RADIAL INCLINATION - ULNAR INCLINATION
ULNAR FLEXION - RADIAL EXTENSION
RADIAL FLEXION - ULNAR EXTENSION

7. The proximal row, from a flexed position in radial
deviation becomes extended in ulnar deviation
RADIAL INCLINATION-ULNAR INCLINATION

8. VIDEO (Please wait)

9. In radial deviation the In ulnar deviation it‘s the
trapezium is pushing the triquetral-hamate joint the
scaphoid towards flexion curve from
Smooth one forcing the proximal
and ulnar translation. row towards extension
flexion to extension
and radial translation.
25º
RADIOLUNATE ANGLE
0º
-25º
Radial dev Neutral Ulnar dev

10. Which structures ensure a smooth progression
from flexion to extension?
 The most important ligament inducing progressive
extension of the proximal row in ulnar deviation is the
palmar triquetrum-capitate-hamate ligament that
increase in tension. The triquetrum is pulled by this
ligament against the proximal pole of the hamate with
which the triquetrum extends.
 The scaphotrapezial ligament causes extension and
1 Scaphoid-Trapezium scaphoid.
pronation to the 2 Dorsal Intercarpal 3 Triquetrum-Capitate
 If the proximal row extends too much the capitate
would sublux dorsally. This is prevented by the
portion of the dorsal intercarpal ligament.

11. 1
2
3

12. The contraction of the flexor carpi ulnaris generates a
dorsal directed vector on the triquetrum that helps
extending the proximal row in ulnar deviation.
VIDEO (Please wait)

13. “Dart-throwing” motion
Carpal kinematics
FLEXION - EXTENSION
RADIAL INCLINATION - ULNAR INCLINATION
flexion-ulnar inclination extension-radial inclination
ULNAR FLEXION - RADIAL EXTENSION
(DART-THROWING)
RADIAL FLEXION - ULNAR EXTENSION

14. “Dart-throwing” motion
 In the dart-throwing motion the wrist rotates from an
extended radial deviation position to a flexed ulnar
deviated position.
 This oblique plane of motion is the one most
commonly used in activities of daily living.
 The contribution of the radiocarpal joint to dart-
throwing motion is minimal, most rotation occurring
at the midcarpal level.
 In the dart-throwing plane the proximal row does not
rotate.
NEUTRAL RADIAL RADIAL INCL.
INCLINATION + EXTENSION

15. ERD FUD
NEUTRAL ULNAR ULNAR INCL.+
“Dart-throwing motion” INCLINATION radiocarpal joint rotation
Minimal EXTENSION

16. Midcarpal rotation VIDEO (Please wait)
DART-THROWING MOTION

17. ERD FUD Moritomo et al,2004
VIDEO (Please wait)
“Dart-throwing motion” Minimal radiocarpal joint
rotation

18. Non-dissociative Instability- Pathomechanics
Non-dissociative Instability
 The wrist exhibits a radiocarpal and/or a midcarpal
subluxation of the entire proximal row during non-
resisted wrist Pathomechanics
motion without injury of the interosseous
ligaments of the proximal row.
Clinical forms
 This result in a clunking wrist. Clunking is a low-pitched
dull sound produced by sudden subluxation and/or
reduction of a partially or totally dislocated carpal bone.
 In the clunking non-dissociative wrist the proximal row
remains flexed until the wrist is ulnarly deviated at
which point it suddenly jumps into extension.

19. Non-dissociative Instability- Clinical forms
Non-dissociative Instability- Clinical forms
 There are two major types of non-dissociated carpal
clunking: extrinsec and intrinsec.
Extrinsic Clunking
 The extrinsec clunking results from injury or bone
alteration outside the carpal area (dorsal malunited
radial fractures). Intrinsic Clunking
 The intrinsec clunking derives from insufficiency or
injury of one, or several, carpal ligaments:
scaphotrapezoid, triquetrum-capitate-hamate, dorsal
Anterior Dorsal Radiocarpal-
scaphotriquetral, palmar radiolunate ormidcarpal
midcarpal midcarpal
ulnolunate.
 There are three major patterns of intrinsic carpal
clunking: anterior midcarpal, dorsal midcarpal and
combined radiocarpal-midcarpal.

20. Anterior midcarpal clunking
 The ligaments mostly involved in the palmar midcarpal
instability are the scaphotrapezial ligament, and the
triquetrum-capitate-hamate ligament.
 The proximal row remains tilted palmarly until near the
end of ulnar deviation, where it suddenly rotates into
25º
extension, sometimes with a palpable thud (catch-up
RADIOLUNATE ANGLE
clunk).
 In most cases there is a combination of medial and lateral
ligament insufficiency.
0º Clunk !
 There are cases where the dysfunction clearly derives
from a predominant injury at the scaphotrapezial ligament
(anterolateral midcarpal instability) or from a
predominant injury ot the triquetrum-capitate-hamate
-25º
ligament (anteromedial midcarpal instability). Stress
views are recommended to assess the location of the
Radial dev Neutral Ulnar dev
predominant injury.

21. CLUNK

22. VIDEO
(Please wait)
Anterior midcarpal clunking

23. Anteromedial midcarpal instability
H C
1
2
Tq 1: Triquetrum - Hamate
2: Triquetrum -
Capitate
Anterior midcarpal clunking after
injury ot the triquetrum-capitate-
hamate ligament
Palmar triqutetrum-capitate-hamate ligament

24. Anterolateral midcarpal instability
Anterolateral midcarpal instability
Anterior
“drawer” test
STT subluxation
(“open mouth” sign)
Scaphoid-Trapezium ligament (STT)

26. Dorsal midcarpal clunking
 The ligaments mostly involved in the dorsal midcarpal
instability are the radioscaphocapitate ligament, and
the dorsal scaphotriquetral ligament.
 As the wrist rotates toward ulnardevation the capitate
subluxes over the edge of the scapholunate socket
inducing hyperextension of the proximal row.
 Once the capitate is subluxed dorsally there is a
reactive contraction of wrist extensors and the distal
row tends to return abruptly to its normal alignment
Dorsal Intercarpal
often with an audible clunk.
Ligament

27. Dorsal midcarpal instability
Dorsal midcarpal instability

28. Radiocarpal- midcarpal clunking
 The pattern of clunking is similar to the anterior
midcarpal instability but adding an increased mobility at
the RC joint implying an abnormally flexed and ulnarly
translocated proximal row in radial deviation.
 This form of clunking is frequent among teenagers with
hyperlax radio-ulno-carpal ligaments.
 In the radiocarpal (or proximal) type of clunking, the
ligaments mostly involved are the palmar long and
short radiolunate and the dorsal radiotriquetral.
Palmar-dorsal radiocarpal ligaments

29. CLUNK
CLUNK
Combined radiocarpal-midcarpal instability
Combined radiocarpal-midcarpal instability

30. Dissociative Instability
Scapholunate instability
Lunotriqueteal instability
Combined radiocarpal-midcarpal instability

31. Dissociative Instability- Pathomechanics
Scapholunate instability
 This instability is secondary to rupture of the linkage
between the bones of the proximal row.
 In the scapholunate instability the scaphoid has lost its
ligament connections and exhibits dorsoradial
subluxation over the edge of the radius ligament
Scapholunate inteosseous during radial
deviation. (SLIL)
 It is important to distinguish between partial and
complete scapholunate interosseous ligament (SLIL)
tears. Partial tears are benign, often asymptomatic.
Complete disruptions evolve intocomplete from
Can we differentiate progressive carpal
collapse and joint degeneration.
partial rupture?
 The dart-throwing plane of motion allows easy
discrimination between partial and total SLIL injury.

32. “Dart-throwing” motion
Complete
SLIL Complete
rupture
SLIL rupture
 Scaphoid and distal row rotated as one single
functional unit.
 Reduced position of scaphoid in radial extesion.
 Dorsolateral subluxation of scaphoid in ulnar flexion.
 Wide gap between the scaphoid and lunate in ulnar
flexion.
 Trapezium does not rotate about the distal scaphoid.
 No scaphocapitate motion.

33. “Dart-throwing” motion
Partial SLIL
rupture
 Increased rotation of scaphoid relative to normal
wrist.
 The lunate rotate and translate laterally but less than
the scaphoid.
 Subtle gapping of the scapholunate joint in ulnar
flexion.
 Reduced trapezium rotation about the distal scaphoid.
 Scaphocapitate motion slightly reduced.

34. “Dart-throwing” motion
Complete Partial SLIL
SLIL rupture rupture
VIDEO (Please wait)

35. “Dart-throwing” motion
Summary
. Partial SLIL
rupture
Clunking of the wrist is the result of a radiocarpal and
midcarpal ligament insufficiency.
There are three major patterns of intrinsic non-
dissociative carpal clunking: anterior midcarpal, dorsal
midcarpal and combined radiocarpal-midcarpal.
The four-dimensional Computed Tomography allows to
detect subtle motion abnormalities to characterize the
different types of non-dissociative wrist instability.
In the dissociative instability four-dimensional Computed
Tomography provide diagnostic criteria that help
differentiating between partial and complete tears of
scapholunate ligament.