Xray Rounds:

Carpal Instabilities

Heather PattersonPGY 2

September 7, 2006

Objectives • Anatomy

– Bones– Ligaments

• Exam– Bones– Ligaments

• Mayfield Classification of Carpal Injuries

• Cases

Anatomy: Bones • PA:

– 3 smooth arcs– Proximal and distal surfaces

of the scapoid, lunate, triquetrum

– Proximal articular surface of the capitate and hamate

NOTE: improper positioning can cause overlap patterns

Anatomy: Bones • Lateral:

– 4 C’s– Axis of the radius, lunate

and capitate is collinear

• Extrinsic:– Volar:

• 2 arcades• V shaped• Proximal & distal• Space of Poirier

– Dorsal:• Less strong than volar groups

• Space of Poirer:• Between radiocapitate and

radiotriquetral ligaments

Anatomy: Liagments

Anatomy: Liagments • Intrinsic:

– Attach carpals– 2 key ligaments:

• Scapholunate• Lunotriquetral

Anatomy: Bones • Lateral:

– Scapholunate angle• 30-60 degrees

• If <30 indicates lunotriquetral ligamentous injury

• >60 indicates scapholunate ligamentous injury

Anatomy: Bones • Lateral:

– Capitolunate angle• 10-20 degrees• Requires a true lateral

to be acurate

• ↑ angle– Consider carpal

ligamentous injury

Clinical • Scaphoid• Lister’s Tubercle• Scapholunate joint• Lunate and capitate• Triquetrum and TFCC• Scaphotrapezium joint• Pisiform• Hook of Hamate

Clinical • Scaphoid

– snuffbox

• Lister’s Tubercle– Prominence on radius, EPL

wraps around this

• Scapholunate joint– Immediately distal to Lister’s

tubercle

• Lunate and capitate– Immediately ulnar to

scapholunate joint

• Triquetrum and TFCC– Immediately distal to ulnar

styloid

• Scaphotrapezium joint– Base of thenar eminence

• Pisiform– Base of hypothenar

eminence

• Hook of Hamate– Soft tissue distal and radial

to pisiform

Clinical: Watson Shift Test • Place thumb on volar

aspect of scaphoid tuberosity and apply pressure while bringing wrist from ulnar to radial deviation

• Sensitivity: ~60-67%’• Specificity: poor

– Wolfe et al (1997) demontrated a 36% false positive rate with 25 healthy volunteers

• Kleinman shear test

• Reagan shuck test

Clinical: Lunotriquetral instability

Linscheid compression test

Mayfield Classification

Stage I: Scapholunate Dissociation

• Disruption of scapholunate ligament– Isolated scaphoid subluxation

+/- rotation– Xray:

• >3mm space between scaphoid and lunate

“Terry Thomas” sign• +/- signet ring sign• Scapholunate angle >60

degrees

Stage II: Capitate Dislocation

• Disruption of radiocapitate ligament and opening of Space of Poirier– May be associated with

scaphoid fracture – Xray:

• PA: overlap of carpal rows• Lateral:

– volar tilt of lunate but maintains articulation with radius

– dorsal dislocation of capitate

Stage III: Lunotriquetral Dissociation

• Failure of radiotriquetral ligament– Perilunate dislocation with

triquetral dislocation– May be associated with volar

triquetral fracture

– Xray:• Perilunate dislocation• PA – overlap of triquetrum on

lunate or hamate

• Disruption of dorsal radiocarpal ligament – Disruption of all intercarpal

joints and most major carpal ligaments

– Associated #:– Xray:

• PA: Lunate appears triangular, “piece of pie”

• Lateral:– “Spilled teacup” sign– Capitate and all carpals

lie posterior to lunate on lateral

Stage IV: Lunate Dislocation

Cases

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