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Four-Dimensional Computed Tomography Imaging of the Wrist

A Novel Technique to Evaluate Dynamic Instabilities

Marc Garcia-Elias MD Josep Monill MD ; Xavier Alomar MDInstitut Kaplan, Barcelona, Spain Creu Blanca, Barcelona, Spain

Aquilion One, Toshiba Medical Systems

0.5 mm detectors- 16 cm of z-axis volume

Gantry rotation time: 350 milliseconds

Minimum temporal resolution: 175 milliseconds

100 kVp-80 mA

14 image series obtained for 14 seconds

DLP 240mGy. cm

Technical parameters in 320-MDCTTechnical parameters in 320-MDCT

Carpal kinematics Carpal kinematics

FLEXION - EXTENSION

RADIAL INCLINATION - ULNAR INCLINATION

ULNAR FLEXION - RADIAL EXTENSION (DART-THROWING)

RADIAL FLEXION – ULNAR EXTENSION

FLEXION-EXTENSION

Y’

Y

X’X

Y’

Y

X’X

RADIAL CUBITAL INCL.

ECRL

FCU

DART-THROWING

ULNAR FLEXION – RADIAL EXTENSIÓN


FLEXION - EXTENSION


ULNAR FLEXION - RADIAL EXTENSION

RADIAL FLEXION - ULNAR EXTENSION

The proximal row hasn´t tendinous attachments

The movement always begins in the distal row

The fibers of midcarpal ligaments increase in tension

The forces of compression generated on the bone force it to move

In the central movements the radiocarpal joint is slightly active

Flexion Neutral Extension


FLEXION - EXTENSION


ULNAR FLEXION - RADIAL EXTENSION


RADIAL INCLINATION ULNAR INCLINATION

FLEXION EXTENSION

The proximal row, from a flexed position in radial deviation becomes extended in ulnar deviation

RADIAL INCLINATION-ULNAR INCLINATION

VIDEO (Please wait)

In radial deviation the trapezium is pushing the scaphoid towards flexion and ulnar translation.

In ulnar deviation it‘s the triquetral-hamate joint the one forcing the proximal row towards extension and radial translation.

Radial dev Neutral Ulnar dev

25º

0º

-25º RA

DIO

LU

NA

TE

AN

GL

E

Smooth curve from flexion to extension

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 pronation to the scaphoid.

If the proximal row extends too much the capitate would sublux dorsally. This is prevented by the portion of the dorsal intercarpal ligament.

1 Scaphoid-Trapezium 2 Dorsal Intercarpal 3 Triquetrum-Capitate

1

2

3

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)


FLEXION - EXTENSION


ULNAR FLEXION - RADIAL EXTENSION (DART-THROWING)


extension-radial inclinationextension-radial inclinationflexion-ulnar inclinationflexion-ulnar inclination

“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 INCLINATION

RADIAL INCL. + EXTENSION

NEUTRAL ULNAR INCLINATION

ULNAR INCL.+ EXTENSION “ “Dart-throwing motion” Minimal radiocarpal joint rotationDart-throwing motion” Minimal radiocarpal joint rotation

ERD FUD

DART-THROWING MOTION

Midcarpal rotation VIDEO (Please wait)

“ “Dart-throwing motion” Minimal radiocarpal joint Dart-throwing motion” Minimal radiocarpal joint rotationrotation

ERD FUD Moritomo et al,2004

VIDEO (Please wait)

Non-dissociative Instability Non-dissociative Instability

Pathomechanics

Clinical forms

Non-dissociative Instability- PathomechanicsNon-dissociative Instability- Pathomechanics

The wrist exhibits a radiocarpal and/or a midcarpal subluxation of the entire proximal row during non-resisted wrist motion without injury of the interosseous ligaments of the proximal row.

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.

Non-dissociative Instability- Clinical formsNon-dissociative Instability- Clinical forms

There are two major types of non-dissociated carpal clunking: extrinsec and intrinsec.

The extrinsec clunking results from injury or bone alteration outside the carpal area (dorsal malunited radial fractures).

The intrinsec clunking derives from insufficiency or injury of one, or several, carpal ligaments: scaphotrapezoid, triquetrum-capitate-hamate, dorsal scaphotriquetral, palmar radiolunate or ulnolunate.

There are three major patterns of intrinsic carpal clunking: anterior midcarpal, dorsal midcarpal and combined radiocarpal-midcarpal.

Anterior midcarpalAnterior

midcarpalDorsal

midcarpalDorsal

midcarpal

Intrinsic Clunking

Extrinsic Clunking

Radiocarpal-midcarpal

Radiocarpal-midcarpal

Non-dissociative Instability- Clinical formsNon-dissociative Instability- Clinical forms

Anterior midcarpal clunkingAnterior 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 extension, sometimes with a palpable thud (catch-up clunk).

In most cases there is a combination of medial and lateral ligament insufficiency.

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 ligament (anteromedial midcarpal instability). Stress views are recommended to assess the location of the predominant injury.

25º

0º

-25º

Clunk !

Radial dev Neutral Ulnar dev

RA

DIO

LU

NA

TE

AN

GL

E

CLUNK

Anterior midcarpal clunking

VIDEO (Please wait)

12

1: Triquetrum - Hamate 2: Triquetrum - Capitate

Tq

CH

Palmar triqutetrum-capitate-hamate ligament

Anteromedial midcarpal instabilityAnteromedial midcarpal instability

Anterior midcarpal clunking after injury ot the triquetrum-capitate-hamate ligament

Anteromedial midcarpal instabilityAnteromedial midcarpal instability

Scaphoid-Trapezium ligament (STT)

Anterolateral midcarpal instabilityAnterolateral midcarpal instability

Anterior “drawer” test

STT subluxation

(“open mouth” sign)

Anterolateral midcarpal instabilityAnterolateral midcarpal instability

Dorsal midcarpal clunkingDorsal 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 often with an audible clunk.Dorsal Intercarpal

Ligament

Dorsal midcarpal instability Dorsal midcarpal instability Dorsal midcarpal instabilityDorsal midcarpal instability

Radiocarpal- midcarpal clunkingRadiocarpal- 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

CLUNK

Combined radiocarpal-midcarpal instabilityCombined radiocarpal-midcarpal instability

CLUNK



Scapholunate instability

Lunotriqueteal instability

Dissociative Instability Dissociative Instability

Dissociative Instability- PathomechanicsDissociative Instability- Pathomechanics

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 during radial deviation.

It is important to distinguish between partial and complete scapholunate interosseous ligament (SLIL) tears. Partial tears are benign, often asymptomatic. Complete disruptions evolve into progressive carpal collapse and joint degeneration.

The dart-throwing plane of motion allows easy discrimination between partial and total SLIL injury.

Scapholunate instability

Scapholunate inteosseous ligament (SLIL)

Can we differentiate complete from partial rupture?


Complete 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.




“Dart-throwing” motion“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.







VIDEO (Please wait)

“Dart-throwing” motion“Dart-throwing” motion



.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.

SummarySummary

Tac 4D de la muñeca

Health & Medicine

ulnar translation

radial translation

waitin radial deviation

flexed ulnar deviated

progressive extension

proximal pole

hamate ligament

neutralneutral dart