Mayfield classification
Classification for carpal bone instability (peri-lunate injuries)
Mechanism of injury:
- Fall on out-stretched hand (FOOSH)
- Injuries always start from Radial side to Ulnar side, therefore Type 1 -> 4 = injuries progressively from Radial to Ulnar side
- A combination of 3 pressure load (listed below), causes rotatory force around the waist of capitate.
- Carpus extension (the principal load)
- Wrist ulnar deviation
- Intercarpal supination
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Important ligaments in perilunate injuries
Purple: Radio-scapho-capitate ligament
Blue: Radio-triquetral ligament
Yellow: Ulno-triquetral ligament |
Imaging:
Radiographs are insensitive except for frank perilunate dislocation / lunate dislocation
Clues:
- Scapho-lunate dissociation
- Scapho-lunate interval 2-4mm: Suspicious ; >4mm: Definite on AP view
- Scapho-lunate angle >63 degree on Lateral view
- Scaphoid bone fracture
- Radial styloid fracture
- Luno-triquetral dissociation
- Scaphoid angle <30 degree:="" identify="" li="" means="" no="" on="" only.="" other="" radiograph="" suspicious="" to="">30>
- Triquetrum fracture
- Capitate fracture
- Gilula's arch disruption / step deformity
- "Piece of pie" sign for perilunate dislocation / lunate dislocation
- "Spilt tea-cup" sign for lunate dislocation
CT better at depicting avulsion injury, step deformity
MRI / MR Arthrography better at depicting bone marrow oedema (trabecula fracture in instance of trauma), ligamentous integrity
Type 1:
*Area of disruption: Scapho-lunate articulation
- Extension + Ulnar deviation => Radio-scapho-capitate ligament tear/avulsion
- Further force causes => Scaphoid fracture / Scapho-lunate ligament tear
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Mayfield type 1: Scapho-lunate articulation disruption |
Type 2:
*Area of disruption: Scapho-lunate + Capito-lunate articulations
- Type 1 injuries plus:
- Capito-lunate ligament tear/avulsion OR Capitate fracture
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Mayfield type 2: Scapholunate & Capitolunate articulation disruptions |
Type 3:
*Area of disruption: Scapho-lunate + Capito-lunate + Luno-triquetral articulations
- Type 1 + Type2 plus:
- Lunotriquetral ligament tear/avulsion OR Triquetrum fracture
- Resulting in peri-lunate dissociation ie Dissociation of lunate from (1) Scaphoid (radial side) ; (2) Capitate (distal articulation) ; (3) Triquetrum (Ulnar side).
- +/- Peri-lunate dislocation ensues ie Lunate is still articulating normally with radius, whereas the rest of the carpal bones are dislocated dorsally.
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Mayfield type 3: Scapholunate, Capitolunate & Lunotriquetral articulation disruptions |
Type 4:
*Area of disruption: Scapho-lunate + Capito-lunate + Luno-triquetral + Radio-lunate articulations
- Radio-lunate ligament tear AND
- Relocation of the carpal bones (except Lunate) back to normal position AND
- Lunate is tilted and displaced to volar aspect, through the space of Poirier.
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Mayfield type 4: All 4 articulations of the lunate bone disrupted |
Reference: https://doi.org/10.1016/j.crad.2019.10.0160009-9260/