Xray Rounds: Carpal Instabilities Heather Patterson PGY 2 September 7, 2006

1. Xray Rounds: Carpal Instabilities Heather Patterson PGY 2 September 7, 2006

3. Objectives • Anatomy • Bones • Ligaments • Exam • Bones • Ligaments • Mayfield Classification of Carpal Injuries • Cases

4. 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

5. Anatomy: Bones • Lateral: • 4 C’s • Axis of the radius, lunate and capitate is collinear

6. Anatomy: Liagments • 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

7. Anatomy: Liagments • Intrinsic: • Attach carpals • 2 key ligaments: • Scapholunate • Lunotriquetral

8. Anatomy: Bones • Lateral: • Scapholunate angle • 30-60 degrees • If <30 indicates lunotriquetral ligamentous injury • >60 indicates scapholunate ligamentous injury

9. Anatomy: Bones • Lateral: • Capitolunate angle • 10-20 degrees • Requires a true lateral to be acurate • ↑ angle • Consider carpal ligamentous injury

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

11. 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

12. 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

13. Clinical: Lunotriquetral instability • Kleinman shear test • Reagan shuck test Linscheid compression test

14. Mayfield Classification

15. 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

16. 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

17. 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

18. Stage IV: Lunate Dislocation • 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

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