Upper Limb 3 The Wrist Donald Sammut Hand Surgeon Kings Upper Limb Anatomy plus lecture notes • Unlike'many'other'joints,'the'wrist'surface'anatomy'gives'away'little'of' the'bony'structures'beneath'the'surface.' • Still'less'does'it'suggest'the'complex'ligament'structures' Carpus' Radius' Ulna' • The'wrist'is'surrounded'by'vital'structures,'tendons,'nerves,'arteries.'' • Pathology'in'these'structures'can'give'symptoms'mistaken'for'problems' with'the'wrist'joint' • 8'wrist'bones'form'the'carpus.' • Proximally'these'articulate'with'the'radius' • Distally'they'articulate'with'the'metacarpals.' • The'carpal'bones'articulate'with'each'other'in'a'particular'configuration'of' bony'shapes'and'ligaments'which'dictate'the'complex'function.' Trapezoid' Capitate' Trapezium' Hamate' Scaphoid' Pisiform' Lunate' Triquetral' • Proximally'the'carpus'articulates'with'the'distal'radius'and'with'the' triangular'fibrocartilage.' • The'TFC'separates'the'carpus'from'the'ulna' • The'distal'ulna'does'not'participate'in'the'articulation'with'the'carpus' • View'of'the'distal'radius.'Proximal'aspect'of'the'RadioKcarpal'joint' • Note'' 'the'Scaphoid'fossa' 'the'Lunate'fossa' 'the'triangular'fibrocartilage' PROXIMAL)ARTICULAR)SURFACE)OF)THE)WRIST:)RADIUS'AND'TRIANGULAR'CARTILAGE' ' THE'ULNA'IS'EXCLUDED.' • Distal'aspect'of'the'RadioKcarpal'joint' The'radius'and'triangular'fibrocartilage'articulate'with'the'scaphoid,'lunate' and'triquetral' DISTAL)ARTICULAR)SURFACE)OF)THE)WRIST:)SCAPHOID,'LUNATE','TRIQUETRAL' ' • The'bony'shapes'of'the'radiocarpal'joint'make'for'an'unstable'arrangement' • There'are'no'bony'confines'(as'in'the'hip)'to'give'the'joint'stability' • Much'stability'is'conferred'by'the'surrounding'ligaments'and'tendons' Note' • For$any$joint,$stability$is$in$inverse$proportion$to$mobility.$The$more$mobile$the$ joint,$the$less$stable$it$is$and$the$more$it$relies$on$soft$tissue$for$stability.$ • Compare$Shoulder$and$hip.$The$shoulder$has$a$wide$arc$of$movement,$the$hip$ less.$The$shoulder$is$regularly$dislocated$in$contact$sports,$the$hip$is$rarely$ dislocated.$The$shoulder$requires$the$support$of$the$rotator$cuff$for$its$stability$ • On'the'ulnar'side,'ligaments'front'and'back'produce'a'cup'shape,'overall'' • The'triangular'fibrocartilage'forms'the'base'of'this'cup' • The'whole'arrangement'is'called'the'TFCC:'Triangular'Fibrocartilaginous' Complex' • This'complex'cups'the'ulnar'part'of'the'carpus' TFCC' Triangular' FibroKCartilaginous' Complex' MOVEMENTS'OF'THE'WRIST:' • Flexion'and'Extension' • Radial'Abduction' • Ulnar'Abduction' • Pronation'and'supination'enormously'increases'the'versatility'of'the' wrist.'This'movement'occurs'at'the'Distal'and'Proximal'radioKUlnar'joints' and'not'at'the'wrist.' Wrist'Flexion' Wrist'Extension' 85°' 85°' Plus' Pronation'and'Supination'' at'DRUJ' Radial'Abduction'''''''''''''''Ulnar'Abduction' • The'commonest'composite'movement'of'the'wrist:' • DorsoKRadial'to'PalmarKUlnar' '(The'DartKThrowing'movement)' Ulnar'Deviation'' and' Flexion' Radial'Deviation'' and'' Extension' The'SCAPHOID' • Largest'bone'in'the'proximal'carpus' • At'an'angle'to'the'axis'of'the'radius'(average'73°)' • The'obliquity'may'explain'its'vulnerability'to'injury' • 80%'covered'in'articular'cartilage' • A'palpable'bony'prominence'on'the'palmar'surface'is'called'the'Tubercle' of'the'Scaphoid.'The'Flexor'Carpi'Radialis'curves'over'it'into'the'palm' • THE'SCAPHOID'' • Commonest'carpal'bone'to'fracture' • Vulnerable'in'landing'on'the'outstretched'hand' • Notoriously'difficult'to'diagnose.'The'fracture'is'often'not'visible'on'first' Xray' • 80%'of'its'blood'supply'comes'through'the'arrowed'middle'segment,'the' waist.'' • This'may'deprive'the'proximal'part'of'the''bone'of'blood'when'the'waist'is' fractured.'This'may'lead'to'AVASCULAR'NECROSIS'of'the'proximal'pole' Scaphoid:'Gr.$skaphos$='boat' 80% surface - articular cartilage 80% blood supply – waist of scaphoid Proximal pole fracture Avascular necrosis of proximal pole The'LUNATE' • So'named'because'of'its'half'moon'shape'on'lateral'Xray' • The'Keystone'of'the'carpus' • Important'ligamentous'links'to'scaphoid'and'triquetral' Palmar' Dorsal' Lunate' The'TRIQUETRAL' • Completes'the'proximal'carpal'row'' • Articulates'with'the'triangular'fibrocartilage' • Carries'the'Pisiform'on'the'palmar'surface' Palmar' Dorsal' Triquetral' The'PISIFORM' • Not'a'true'Carpal'bone'–'a'sesamoid'for'distal'insertion'of'Flexor'Carpi' Ulnaris' • The'PisoKhamate'and'PisoKmetacarpal'ligaments'give'the'FCU'strong' insertion'into'the'entire'ulnar'half'of'the'carpus.' Palmar' Dorsal' Pisiform' Insertion'of'Flexor'Carpi'Ulnaris' PisoKHamate' PisoKMetacarpal' Ligament' Ligament' The'TRAPEZIUM' • The'most'mobile'of'the'distal'carpal'row' • Distal'surface'the'saddle'shaped'CarpoKmetacarpal'joint'with'the'thumb' metacarpal' • On'the'palmar'surface'has'a'ridge'(the'Trapezial'ridge)'beneath'which'the' Flexor'carpi'radialis'courses'on'its'way'to'insertion'into'the'bases'of' Metacarpal'2'and'3.' Palmar' Dorsal' Trapezium' The'TRAPEZOID' • Smallest'bone'of'the'distal'carpal'row' • Trapezoidal'in'shape'and'wedged'in'between'Trapezium''and'Capitate' wider'on'the'dorsum'and'narrower'on'the'palmar'surface.' Palmar' Dorsal' Trapezoid' The'CAPITATE' • Largest'bone'of'the'carpus' • Important'insertion'point'for'a'number'of'stabilising'ligaments.' • The'proximal'part'is'called'the'Head'of'the'Capitate'and'articulates'with'a' deep'concavity'formed'by'scaphoid'and'lunate,'in'the'midcarpal'joint.' Palmar' Dorsal' Capitate' The'HAMATE' • So'called'because'of'the'prominent'Hamulus'(hook)'on'the'palmar'aspect' • This'hamulus'receives'insertion'of'the'flexor'retinaculum'and'the'pisoK hamate'ligament' • The'flexor'tendons'to'the'little'finger'change'angle'around'the'Hook'of' the'hamate' Palmar' Dorsal' Hamate' Three'levels'of'joints'in'the'wrist' • CarpoKMetacarpal'Joints:'Between'carpus'and'metacarpals' • MidKcarpal'joint:'between'proximal'and'distal'carpal'rows' • RadioKCarpal'Joint:'between'Radius'and'proximal'carpal'row' CarpoKMetacarpal' 'Joints' MidKCarpal'Joint' RadioKCarpal'Joint' The'8'Carpal'bones'are'organised'in'two'rows:' • PROXIMAL'CARPAL'ROW:'Sacphoid,'Lunate,'Triquetral'(+pisiform)' • DISTAL'CARPAL'ROW:'Trapezium,'Trapezoid,'Capitate,'Hamate' Proximal Carpal Row Distal Carpal row Mid Carpal Joint Radio Carpal Joint • The'carpus'is'more'proximal'than'the'surface'anatomy'might'suggest' • There'are'two'creases'on'the'palmar'surface'of'the'wrist.' • The'proximal'crease'coincides'with'the'Radio'Carpal'Joint' Proximal'' Wrist'' crease' • The'(palpable)'four'bony'landmarks'of'attachment'of'the'flexor' retinaculum' Radial:' ' 'The'ridge'of'trapezium' ''The'tubercle'of'the'scaphoid'' Ulnar: ' 'The'hook'of'the'hamate' ''The'Pisiform' ' ' ' The'Pisiform' Ridge of Hook of trapezium Hamate Pisiform Tubercle of scaphoid • The'strong'Flexor'Retinaculum'holds'the'columns'of'the'concave'carpus' • Division'of'the'Flexor'Retinaculum,'as'in'carpal'tunnel'release,'causes' surprisingly'little'functional'impairment'(the'Flexor'retinaculum'rapidly' reforms)' ' ' ' • The'carpal'bones'are,'as'a'group,'concave'on'the'palmar'aspect.' • The'rest'of'the'hand'reflects'this'concavity' • Most'hand'function'involves'the'palm'and'the'digits'curving'around'an' object'and'this'concavity'forms'the'basis'of'function.' ' ' ' • Cross'section'of'the'palm'also'shows'this'palmar'concavity'and'dorsal' convexity' • This'means'that'the'extensors'are'spread'over'a'wide'area'on'the'back'of' the'carpus'and'need'to'be'held'in'separate'compartments'to'maintain' alignment' • The'flexors'are'bunched'up'inside'the'carpal'tunnel'and'need'no'such' separation' ' ' ' IV III V II VI I • The'flexor'retinaculum'is'much'shorter'than'the'Extensor'retinaculum'as'a' result'of'the'carpal'concavity'towards'the'palm' ' ' ' Dorsal Palmar Xrays'of'the'wrist' • Xrays'of'the'wrist'present,'on'superficial'examination,'complex'bony' shapes'superimposed'on'each'other' • It'is'not'difficult'to'follow'each'bony'outline'and'analyse'the'Xray' appearance.' • The'distal'Carpal'row'and'the'proximal'Carpal'rows'are'easy'to'make'out' ' ' ' Distal'Carpal'Row' Proximal'Carpal'Row' • Gilula’s'Lines'are'a'useful'quick'check'of'alignment'or'loss'of'normal' relations' • These'radiological'arcs'most'be'followed'to'detect'any'step'or' interruption' ' ' ' Gilula’s'Lines'(Radiological'Arcs'of'the'wrist)' • The'ulnar'tilt'of'the'radius'can'be'checked'on'the'PA'view' ' ' ' Ulnar'Tilt' 20-25° • The'true'lateral'of'the'wrist'shows'the'tip'of'the'radial'styloid' superimposed'on'the'centre'of'the'lunate' this'view'also'shows'the'volar'tilt'of'the'radius' ' ' ' Volar'Tilt' 10 - 15° • The'axis'of'the'scaphoid'is'drawn'bisecting'the'scaphoid' • The'axis'of'the'lunate'is'obtained'by'joining'the'tips'of'the'two'peaks'of' the'lunate'on'lateral'view'and'drawing'a'line'at'90°'to'this.' • The'angle'between'Lunate'and'scaphoid'is'a'good'guide'to'the'integrity' of'the'scaphoKlunate'ligament'(see'later)' ' ' ' Axis'of'' Scaphoid' Axis'of'' Lunate' Scapho'Lunate' Angle:'avge'47°' (30'K60)' • The'ligaments'that'clothe'the'carpus'are'not'immediately'visible'even'on' removal'of'the'covering'tendons.'' • They'are'covered'by'a'thin'fibrofatty'film'which'must'be'removed'before' the'orientation'of'ligament'fibres'is'seen' ' ' ' Intrinsic'Ligaments' ' Carpal'bone'to'Carpal'bone' Carpal'bone'to'Metacarpal' ' ' ' ' Extrinsic'Ligaments' ' Radius/Ulna'to'Carpus'' Intrinsic ligaments Extrinsic Ligaments • The'extrinsic'Ligaments''(from'radius'and'Ulna'to'Carpus)'seem' bewildering'and'complex'but'there'is'a'logic'to'their'orientation' • The'key'is'the'Ulnar'tilt'of'the'radius.'