- Work Up for Scaphoid Frx: (w/ discussion)
-
clinical differential diagnosis:
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distal radius frx
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transscaphoid perilunate dislocation:
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scaphoid impaction syndrome
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radiographs and determination of stability (CT scan)
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non diagnostic radiograph (
bone scan)
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tubercle frx
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transverse waist frx
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proximal pole frx
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treatment:
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non-displaced fractures
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casting of scaphoid frx
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percutaneous scaphoid fixation
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surgical treatment of displaced frx (
herbert screw fixation of scaphoid fractures):
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complications:
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nonunion of scaphoid (
3.5 mm cannulated screw fixation)
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non union of proximal pole
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bone grafting technique
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avascular necrosis of the scaphoid
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SLAC or SNAC wrist
- degenerative disease of the STT joint:
- Degenerative changes at the STT joint following Herbert screw insertion: A radiographic study comparing patients w/ scaphoid frx and primary hand arthritis.
J. E. Nicholl et al. J. Hand Surg. (Br) p 422-426, 25B, No 5, Oct 2000
- Discussion:
- surface of scapoid is largely covered by articular cartilage, & only narrow area of its neck, & even smaller
distal portion, are accessible to blood vessels;
- frxs across scaphoid may destroy
blood supply to its proximal part;
- scaphoid represents floor of
anatomic snuff box;
- scaphoid spans both carpal rows and therefore has less mobility than other carpals;
- scaphoid is principal bony block to dorsiflexion of hand & wrist & is suscepible to frx during fall on outstretched hand;
- scaphoid (navicular): the most frequently fractured carpal bone (frx occurs in
tubercle,
waist, or
proximal 1/3);
- biomechanics and scaphoid movement:
- scaphoid exerts flexion extension control over lunate and distal carpal row;
- ulnar side of the wrist exerts rotational control and stability;
- as wrist rotates from neutral to ulnar deviation, proxomal row dorsiflexes & x-ray profile of the scaphoid appears longer;
- in radial deviation, proximal carpal row volar flexes & scaphoid appears foreshortened;
- hence,
ulnar deviation AP is necessary for visualization of scaphoid;
- becuase scaphoid crosses both proximal & distal carpal rows, excessive dorsiflexion causes it
to be pinned between dorsal lip of radius & palmar sling of the
radial capitate ligament;
- scaphoid flexes with wrist flexion & extends with wrist extension, but it also flexes during radial deviation & extends w/ ulnar deviation;
- these factors make immobilization of scaphoid fractures difficult;
- w/ scaphoid frx, distal scaphoid tends to flex, & proximal scaphoid extends with the proxmal carpal row;
- because of this, angulation occurs at frx site, which gaps open dorsally & gradually assumes a humpback deformity;
- Mechanism of Frx:
- most injuries to wrist are sustained by a fall on outstretched hand;
- frx occurs w/ wrist is dorsiflexed & radially deviated;
- in this position, proximal pole of schaphoid is held by radius & radioscaphocapitate ligament, while distal pole
of bone is carried dorsally by trapeziocapitate complex;
- radioscaphoid ligament is relaxed by & radial deviation & cannot alleviate tensile stresses accumulating
on radiovolar aspect of the scaphoid:
-
radioscaphoid ligament:
- inserts onto tuberosity of scphoid & is radial expansion of radiocapitate ligament which courses over palmar concavity of
scaphoid proximal to tuberosity before inserting on palmar aspect of capitate;
- forms a fulcrum over which scaphoid rotates;
- References for Scaphoid Frx
