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8/3/2019 Wrist Acadimya 1.4
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Dr Youssef Masharawi1
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Dr Youssef Masharawi2
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Dr Youssef Masharawi3
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Dr Youssef Masharawi4
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Dr Youssef Masharawi5
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Dr Youssef Masharawi6
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Dr Youssef Masharawi7
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Dr Youssef Masharawi8
Palmar flexion Begins at midcarpal joint with tightening of
dorsal extrinsic ligaments Triquetrum moves proximally and dorsaly on
hamate
Lunate shifts dorsally with triquetrum
palmar rotation of the lunate
Via the SLL the scaphoid also palmar rotates
Dorsal ligaments lock the triquetrum on hamateand TFC
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Dr Youssef Masharawi9
Dorsal flexion
Begins at midcarpal joint, initiated by wristextensors
Triquetrum moves proximally and dorsallyon hamate - RLTL tightens
Capitate and lunate remain coaxial
With RCL tightening, dorsiflexes scaphoidand capitate. This sling across scaphoid
prevents palmar flexion of the lunate whichwould occur due to elevation of triquetrumon hamate. Movement occurs primarily at
the radiocarpal joint
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Radial deviation
Proximal carpal row flexes and moves ulnarly.Distal row is displaced radially
Scaphoid rotates into palmar flexion, clears theradial styloid process and allows greatermovement - drops into gap
Triquetrum moves proximally and distally onhamate
Lunate shifts dorsally with triquetrum, makingthe lunate axis now dorsal to the capitate axis
and any force though capitate now causespalmar rotation of the lunate Via the SLL, the scaphoid also forced into further
palmar flexion/rotation
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Dr Youssef Masharawi11
Ulnar deviation Proximal row slides radially, whilst distal row
moves ulnarly Triquetrum moves distally and palmarly on
hamate
Lunate shifts palmarly with triquetrum, makingthe lunate axis now palmar to the capitate axisand any force though capitate now causesdorsal rotation of the lunate
Via the SLL, the scaphoid also forced into furtherdorsal flexion/rotation creating a lengthenedappearance of scaphoid
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Dr Youssef Masharawi12
KINEMATICS OF WRIST
FUNCTION
Several columnar theories eg : Weber
(1984 Three columns:
1. Force bearing column2. Control column
3. Thumb axis column
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Dr Youssef Masharawi14
2. Control column
distal ulna
ulnar carpal complex: TFC, triquetrum,
hamate, base of 4th and 5th MC * Function: longitudinal force
transmission deflected to force-bearing
column via hamate-capitate articulation,
which allows rotational control of proximal
carpal row
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Dr Youssef Masharawi15
3. Thumb axis column
distal third of scaphoid
trapeziotrapezoid joint
base of first metacarpal * Function: supports base of the thumb,
allowing its independent function
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POINTS TO NOTE: no direct motor control of wrist as all motor
units controlling wrist arise from forearmand insert distal to wrist (except FCU).
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Dr Youssef Masharawi17
POINTS TO NOTE: Wrist accomplishes functions of stability
and mobility by making use of a dualarticular system.
Motion in stable range of one joint(proximal/radiocarpal) is amplified at
second joint (distal/midcarpal) without loss
of stability.
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Dr Youssef Masharawi18
POINTS TO NOTE: Most important volar intrinsic ligaments for
stability are scapholunate andlunotriquetral.
Biomechanically extrinsic ligaments are
stiffer while intrinsic ligaments capable of
greater elongation before permanentdeformation occurs.
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Loose packed position
slight extension and ulnar deviation Closed packed position
RD and extension combined
Capsular patternflexion = extension in restriction
Innervations
-abundant, note close proximity to numerousnerve
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CLASSIFICATION OF CARPAL
INSTABILITY
Intracarpal instability generally classifiedin one of three ways:
anatomically - radial or ulnar
ability to be radiographicallydemonstrated - static or dynamic
orientation of the lunate - VISI or DISI
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Dr Youssef Masharawi21
CLASSIFICATION OF CARPAL
INSTABILITY Wrist instability results from either an
incompetent ligamentous support system or achange in the joint contact surface configurationor both
Ligament incompetence may be result ofcongenital laxity, stretching or traumatic rupture(partial/complete)
Changes in joint contact surface configurationusually secondary result of fracture
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Four major types of carpal
instabilities
dorsiflexion instability (most common) palmar flexion instability
ulnar translocation dorsal subluxation
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Dorsal intercalated segement
instability (DISI)
Often associated with radial instabilitiesinvolving scaphoid and lunate
Capitate displaces dorsal to long axis of
radius producing Zig-Zag radius-lunate-
capitate alignment
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Dr Youssef Masharawi24
Volar intercalated segment
instability (VISI)
often associated with ulnar instabilitiesinvolving lunotriquetral or midcarpal joints
lunate palmar flexes
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Ulnar translocation occurs if carpus has shifted in an ulnar
direction
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Dorsal subluxation Carpus subluxed dorsally in its normal
relationship to radius.
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Mechanism of injury:Carpal injuries represent a spectrum of bony and
ligamentous damage.
Final injury determined by:
- type of 3 dimensional loading
- magnitude and duration of forcesinvolved
- position of hand at time of impact - biomechanical properities of bones and
ligaments
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Also remember radiocapitate ligament maximally taut in
maximum extension and ulnar deviation radioscaphoid ligament is maximally taut
in maximum extension
proximal carpal row stabilized to distalforearm by five ligaments, whereas distalrow by only one ligament (radiocapitate)
weakest ligaments are on radial side(radial collateral and radiocapitate)
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most susceptible position of wrist is maximal
extension where dorsal articular surfaces areunder marked compression and volar ligamentstructures are under marked tensile stress
most wrist injuries occur via a fall on theoutstretched hand and with the impact on thethenar aspect of the wrist wrist extension,
ulnar deviation and intercarpal supination,causing reproducible pattern of ligament failure
Recommended