The

Donald Sammut Hand Surgeon

Kings Anatomy plus lecture notes

GENERAL'PANORAMA'OF'THE'HAND'

Two'hills'and'a'valley:' • Hills:'Thenar'and'hypothenar'eminences'

• Valley:'palmar''beneath'which'enter'most'neurovascular' structures'and'the'flexor'tendons'and'lumbricals.'The'interossei'lie'in'the' depths'of'this'valley,'level'with'the'metacarpals'

• The'carpal'tunnel'is'the'main'portal'into'the'hand'

• Dissection'and'removal'of'the'palmar'aponeurosis'(the'flattened'end' tendon'of'Palmaris'longus)'reveals'the'neurovascular'plane.'

• The'tendons'emerge'through'the'carpal'tunnel'(which'forms'an' important'mechanical'pulley)'and'fan'out'to'the'digits'

The'Hand'Skeleton' • The'metacarpals'articulate'proximally'with'the'carpal'bones'and'distally' with'the'phalanges.'

• The'basal'joints'of'the'metacarpals'vary'in'their'mobility' • The'1st'Metacarpal'(the'thumb)'is'the'most'mobile'and'is'effectively'able' to'circumduct,'i.e.'the'thumb'column'can'rotate'about'the'base'through' 360°'

• The'5th'(little'finger)'and'4th'(ring'finger)'metacarpals,'also'have'mobile' basal'joints'with'the'5th'more'mobile'than'the'4th.''

• The'2nd'(index)'and'3rd'(middle)'metacarpals'are'firmly'attached'to'the' carpus'and'to'each'other'and'have'practically'no'movement'at'the'base'

• The'carpal'bones'are'curved'so'that,'as'a'group,''they'are'concave'in'the' palmar'aspect'and'convex'in''the'dorsal'aspect.'

• This'curvature'is'reflected'in'the'metacarpal'heads.'The'metacarpals'flare' out'from'the'carpus'and'describe'a'gentle'curve,'concave'towards'the' palmar'aspect.'

• The''metacarpal'bases'are'secured'to'the'carpus'and'the'heads'(distally)' are'secured'to'each'other'by'the'Deep'Transverse'Intermetacarpal' ligament.''

• This'ligament'is'immensely'strong'–'the'metacarpals'will'fracture'before' the'ligament'gives'way.'An'individual’s'entire'weight'can'hang'from'this' ligament'without'it'rupturing.'

• It'holds'the'heads'of'the'metacarpals'bound'together'and'is'in'continuity' with'the'volar'plate'of'the'MCP'joints' The'Deep'Transverse'Intermetacarpal'Ligament'

Phalanges'

Metacarpals' • The'Deep'Transverse'metacarpal'ligament'receives'fibres'from'all'related' musculoskeletal'structures'which'pass'by:'Lumbricals,'interossei,'volar' plate,'collateral'ligaments,'flexor'tendon'sheath'–'all'contribute'to'a'mesh' of'collagen'fibres'which'is'called'the'ZANCOLLI'COMPLEX.''

• This'is'an'important'landmark'point'in'the'hand,'at'the'distal'border'of' the'palm'and'the'proximal'border'of'the'digit.' Extensors'

Meta'

Flexors'

Zancolli'Complex' *' *'

• Virtually'all'activity'of'the'hand'involves'an'increase'in'the'palmar' curvature'of'the'metacarpals.''

• Grip,'making'a'fist'and'most'manipulation'curves'the'hand'around'an' object'

• The'gentle'curve'of'metacarpal'heads'is'increased.'

• The'Intrinsic'muscles'in'the'hand'also'tend'to'curve'in'a'palmar'direction.'

• Both'the'thenar'and'hypothenar'muscles'tend'to'oppose'their'respective' digits'so'as'to'curl'around'a'held'object.'

• The'Thumb'skeleton:'two'phalanges'and'a'metacarpal.'

• Developmentally,'all'three'bones'are'phalanges,'with'a'growth'centre'in' the'proximal'end'(as'all'phalanges).'‘True’'metacarpals'(index,'middle,' ring'and'little)'have'a'growth'plate'at'their'distal'end.'

• The'embryonic'thumb'metacarpal'develops'into'the'trapezium'with'its' specialized'basal'joint'to'the'metacarpal.' DISTAL'PHALANX'

PROXIMAL'PHALANX' Interphalangeal+Joint+

METACARPAL' Metacarpo1Phalangeal+ Joint+

Carpo1Metacarpal+ Joint+

TRAPEZIUM' MOVEMENT'PLANES'OF'THE'THUMB' Pure'movements:' • Abduction/Adduction:'Movement'away'and'towards'the'palm,'at'90°'to'the' palm' • Extension/Flexion:'Movement'away'and'towards'the'palm,'in'the'plane'of'the' palm' • Retropulsion:'With'hand'flat'on'a'surface,'palm'down,'the'thumb'can'lift'off' the'surface' Composite'Movements:' • Circumduction:'a'cascade'of'sequential'activity'of'flexion/extension/ abduction/adduction' • Opposition:'Similar'sequence'of'pure'movements'which'result'in'the'thumb' pulp'‘opposing’'the'digit'pulps.' Adduction' Abduction' Retropulsion'

Composite'actions' Circumduction'and'Opposition'

Circumduction' Opposition' • Basal'Joint'of'the'thumb'(1st'Carpoimetacarapal'joint)'

• ‘Sellar’'or'‘Saddle’'joint'

• Kapandji'stated'that'‘If'the'basal'joint'of'the'thumb'were'a'true'saddle,'it' would'be'a'saddle'for'a'scoliotic'horse’.'

+(Scoliosis+is+the+abnormal+curvature+of+the+spine,+side+to+side)+

• The'saddle'is'asymmetric' Kapandji: Biomechanics of the Thumb, Vol 1, Philadelphia, 1981. WB Saunders Kucynski: Carpometacarpal joint of the Thumb, J Anat, 1974

• The'radial'condyles'on'both'the'trapezium'and'the'head'of'the' metacarpals,'are'relatively'larger'than'the'ulnar'condyles' ulnar radial

Meta

Trapz • This'asymmetry'means'that'when'the'thumb'is'abducted,'the'whole' thumb'skeleton'tends'to'turn'into'pronation'

• This'tendency'is'purely'skeletal'and'not'mediated'by'muscle'movement' • The'skeleton'thus'tends'to'curve'the'thumb'naturally'towards'the'long' digits.'

• The'strong'ligament'on'the'ulnar'side'of'the'basal'joint''i'the'beak' ligament'(see'wrist'lecture),'acts'as'a'fulcrum,'a'pivot,'around'which'this' pronation'rotates.'

PRONATION'OF'THE' THUMB'COLUMN' WITH'ABDUCTION.'

INDEPENDENT+OF++ MUSCLE+ACTION+ • The'MP'joints'(Metacarpophalangeal)'and'IP'joints'(Interphalangeal,' proximal'and'distal)'are'hinge'joints.'

• The'metacarpal'heads'are'oval,'camishaped.'The'‘hinge’'is'not'pure'since' flexion'of'the'phalanx'also'means'a'migration'in'a'palmar'direction,'so' that'the'movement'is'actually'a'gentle'spiral.'

• For'clinical'purposes'the'MP'and'PIP,'and'DIP'joints'are'hinge,'or'uniiaxial,' joints' The'Metacarpo'phalangeal'and'Interphalangeal'Joints' ' Uniaxial'(Hinge)'Joints:'' PIPJ'and'DIPJ'='True'Hinge;'' MCPJ'='Spiral'

• The'cam'shaped'head'of'the'metacarpal'means'that:''

• In'extension,'the'collateral'ligament'is'slack.'' • In'flexion,'the'collateral'ligaments'are'taut' The'MetacarpoiPhalangeal'Joint' (all'digits'and'thumb)'

Collateral'ligament'slack'in'extension'

Collateral'ligament'tense'in'flexion' • The'PIP'joint'describes'a'pure'arc'of'a'circle'in'flexion'and'extension.'The' collateral'ligaments'are'taut'in'flexion'and'in'extension.'

On'the'palmar'surface'is'the'VOLAR'PLATE'which'is'in'two'parts:'

• The'distal,'rigid,'fibrocartilaginous'part'

• The'proximal,'ligamentous,'flexible'part' The'PIP'Joint'

Flexible'Part'of'Volar'Plate'' Rigid'Part'of'Volar'Plate'' (Ligamentous)' (Fibrocartilage)' • In'flexion,'the'flexible'part'rucks'up,'concertinas,'so'that'the'middle' phalanx'can'flex'

• If'a'PIP'joint'is'allowed'to'stay'in'flexion'for'any'significant'time'(such'as' after'hand'injury,'when'movement'is'painful),'the'flexible,'rucked'part'of' the'volar'ligament,'soon'shrinks'and'contracts'into'scar.'

• This'is'a'problem'that'is'easy'to'prevent'and'difficult'to'cure,'once' established' Fixed'Flexion'' Contracture' • The'safe'position'to'splint'any'joint'is'the'‘Close'Packed’'position'when' most'of'its'ligaments'are'on'full'stretch'(and'thus'unable'to'contract'and' scar'rigid).''

• In'the'hand:'

• The'MPjoint'must'be'splinted'flexed'(with'all'collateral'ligaments'on'the' stretch)'

• The'PIP'and'DIP'joints'must'be'splinted'extended'(with'the'volar'plate'at' full'stretch).' The'Safe'Position'of'the'Hand' ' ' All'Joints'in'‘CloseiPacked'Position’' Collateral'Ligament'tears' • Tear'of'the'ulnar'collateral'ligament'of'the'MP'joint.'

• The'Skier’s'injury.'Also'known'as'the'Gamekeeper'thumb.' • This'is'a'debilitating'injury,'since'the'integrity'of'grip'requires'that'the' thumb'MP'joint'does'not'give'way'when'an'object'is'grasped.'The'ulnar' collateral'ligament'is'a'strong'ligament'resisting'distraction'of'the'MP' joint'in'a'radial'direction'(the'joint'gives'way).' Skier’s'Thumb' Torn'Ulnar'Collateral'Ligament'

Stener'Lesion'

Littler’s'‘Armchair’'arrangement'' of'stabilizing'ligaments'of'PIPJ' • The'PIP'joint'has'a'system'of'ligaments'which'give'it'great'stability,' considering'its'size.'

1. The'collateral'ligaments'either'side' 2. The'Volar'plate/ligament'

The'triple'arrangement'surrounds'the'proximal'phalanx'head'on'three'sides.' Littler'has''called'this'the'‘armchair’'arrangement'of'stability'of'the'PIP'joint.' Littler’s'‘Armchair’'arrangement'' of'stabilizing'ligaments'of'PIPJ'

THE'INTRINSIC'MUSCLES:'def:+all'muscles'distal'to'the'wrist'crease' ' ' THENAR'MUSCLES:' 'FLEXOR'POLLICIS'BRECVIS' X3 ' ''ABDUCTOR'POLLICIS'BREVIS' '''OPPONENS'POLLICIS' ' X1 ' ''ADDUCTOR'POLLICIS' ' HYPOTHENAR'MUSCLES 'FLEXOR'DIGITI'MINIMI' X3 ' ''ABDUCTOR'DIGITI'MINIMI' '''OPPONENS'DIGIT'MINIMI' ' LUMBRICALS' X4' ' INTEROSSEI ' '3'DORSAL'INTEROSSEI' X7 ' ''4'PALMAR'INTEROSSEI' iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii' TOTAL:'18'MUSCLES' ' ' ' The'Thenar'muscles' Thenar'muscles:'

Flexor'Pollicis'Brevis:'' Origin:'Flexor'retinaculum'and'adjacent'trapezium' Insertion:'Radial'sesamoid'of'the'thumb'and'on'to'the'radial'border'of'the'proximal'phalanx' ' ' Abductor'Pollicis'Brevis:' Origin:'Flexor'Retinaculum'and'tubercle'of'the'scaphoid' Insertion:'Tendon'of'Extensor'Pollicis'longus'(Dorsal'expansion)' ' Opponens'Pollicis'(in'the'depths'of'the'thenar'eminence'and'only'visible'by'distracting'FPB'or' AdPB)' Origin:'Flexor'retinaculum'and'adjacent'trapezium' Insertion:'The'whole'of'the'radial'border'of'the'thumb'metacarpal.' ' '

Flexor'Pollicis'Brevis'

Abductor'Pollicis'Brevis' APB' Abductor'Pollicis'Brevis' ABDUCTION' • The'true'opposer'of'the'Abductor'Pollicis'Brevis'is'not'the'Adductor' Pollicis'

• It'is'the'Extensor'Pollicis'Longus'' • The'opposite'of'Adduction'in'the'thumb'is'retropulsion'and'this'is' produced'by'Extensor'Pollicis'Longus.' Abductor'Pollicis'Brevis' 'is'opposed'by'' Extensor'Pollicis'Longus' ' ' (Retropulsion'is'the'' true'opposite'of'Abduction)' EPL'

APB' • The'most'important'function'of'the'FPB'and'AdPB'is'stabilisation'of'the' MP'joint'of'the'thumb,'preventing'it'buckling'backwards'when'stressed.' Flexor Pollicis Brevis Abductor Pollicis Brevis

Stabilisation of the MPJ Median+n+'

FPB

AbdPB Opponens'Pollicis' • The'opponens'Pollicis'has'a'range'of'fibre'lengths'(unlike'the'Pronator' Quadratus).''

• This'ensures'that'there'is'always'some'part'of'it'that'is'active'in'all'points' of'the'opposition'curve.' Opponens Pollicis

PQ'

36'mm'

15'mm' The'Adductor'Pollicis'

• The'Adductor'Pollicis'is'a'powerful,'fanishaped'muscle'(in'proportion,'it' would'rival'the'Quadriceps'in'the'thigh).'

• Part'of'it'is'visible'on'the'dorsum'of'the'hand'

• It'lies'deep'in'the'palm'(only'the'interossei'and'metacarpals'are'more'dorsal).' • Most'of'it'is'visible'from'the'palmar'aspect.'

• Origin'in'2'heads:'

• Transverse'head:'the'entire'palmar'aspect'of'the'third'metacarpal' • Oblique'head:'bases'of'2nd'and'3rd'metacarpals'and'adjoining'carpal'bones.'

• Insertion:'via'the'ulnar'sesamoid'into'the'tendon'of'Extensor'Pollicis'longus' (Dorsal'Expansion)'

Stabilisation'of'The'MCPJ'

Adductor'Pollicis'

Flexor'Pollicis'Brevis'' and'' Abductor'Pollicis'Brevis' P1

M1 FPL AbdPB

FlexPB

Moment''at'MPJ' AddP • The'main'function'of'the'sesamoids'is'to'increase'the'mechanical' advantage'of'the'inserting'muscle.'There'are'many'such'examples'in'the' upper'and'lower'limbs.'

• Around'the'MP'joint'of'the'thumb.'' • The'radial'sesamoid'increases'the'moment''of'the'Flexor'Pollicis' Brevis'and'Adductor'Pollicis,'to'give'them'a'better'mechanical'advantage' in'stabilisiing'the'MP'joint.' The'same'applies'to'the'ulnar'sesamoid'which'increases'the'moment'arm' of'the'Adductor'Pollicis'

• Paralysis'of'these'muscular'stabilising'factors'allows'the'MP'joint'to' buckle'into'hyperextension'instability.'

• This'is'precisely'analogous'to'the'‘Claw'Hand’'instability'on'the'long'digits' (see'later)'

• Patients'with'intrinsic'paralysis'will'avoid'grasping'an'object'between'the' tips'of'digit'and'thumb'since'this'leaves'the'unstable'MP'joint' unsupported.''

• They'will'tend'to'use'the'grasped'object'as'the'stabilising'force'.'

• Why'is'the'Adductor'Pollicis'attached/originating'from,'the'third' metacarpal'?'

• If'it'were'attached'to'the'index'this'would'give'it'a'limited'sphere'of' actioon'

• The'third'metacarpal'is'the'central'axis'of'the'hand'and'this'gives'the' adductor'pollicis'a'range'and'power'to'face'all'digits'equally'

• The'‘reach’'of'the'Adductor'pollicis'is'made'more'effective'by'the'fact'that' both'the'little'and'(less)'the'ring,'are'able'to'oppose'to'some'degree,'and' approach'the'thumb.'

• A'loss'of'opposition.'

• This'paralysed'hand'is'attempting'to'oppose'but'the'thenar'muscles'are' atrophied.'Abduction'is'absent'and'the'patient'succeeds'merely'in'flexing' the'thumb'across'the'palm'

• This'patient'is'unable'to'oppose'his'left'thumb.''

• Note'the'plane'of'the'nail'which'is'always'revealing'of'the'amount'of' opposition'possible.'In'full'opposition,'the'nail'pronates'so'that'the'thumb' nail'and'the'digit'nail'are'parallel.'

The'Hypothenar'Muscles'

The'Hypothenar'muscles' • Precisely'the'same'arrangement'as'the'thenar:' Flexor'digiti'Minimi:'' • Origin:'Flexor'Retinaculum' • Insertion:'base'of'proximal'phalanx'

Abductor'Digit'Minimi:' • Origin:'Pisiform'bone'and'flexor'retinaculum' • Insertion:'ulnar'side'of'base'of'the'proximal'phalanx'and'the'dorsal'digital'expension'

Opponens'digiti'minimi:' • Origin:'Flexor'retinaculum'and'hook'of'hamate' • Insertion:'ulnar'border'of'the'shaft'of'the'fifth'metacarpal.'

In'addition:'

The'Palmaris'Brevis.'Part'of'the'‘Panniculus'Carnosus’'layer'of'muscle'(eg:' the'platysma'in'the'neck,'and'the'muscles'of'facial'expression)'

• Main'function'to'ruck'up'the'ulnar'skin'of'the'palm.'

• May'have'a'function'in'producing'a'watertight'seal,'as'for'instance'when' one'carries'water'in'both'cupped'.'

Flex.'Dig.'Minimi' Abd.'Dig.'Minimi' Opp.'Dig.'Minimi'

• As'a'group,'the'hypothenar'muscles'produce'significant'opposition'of'the' little'finger,'help'surround'a'grasped'object'and'approach'the'thumb.'

The'Lumbricals'and'Interossei'

• Some'Terminology'

• The'intrinsic'Muscles'in'the'hand'='all'muscles'in'the'hand'beyond'the' wrist'crease.'Includes'all'interossei,'lumbricals,'thenar'and'hypothenar' muscles'

• The'Lumbricals':'Muscles'arising'from'the'Flexor'profundus'tendons'and' inserting'into'the'long'extensor'mechanism'

• The'interossei:'literally'‘between'the'bones’'lie'between'the'metacarpals' and'insert'into'the'Dorsal'expansion'and'the'long'extensor'mechanism.' Lumbricals'and'interoseei:'

• Precision'agents'in'the'hand.' • Power'resides'in'the','precision'in'the'hand.'

• The'lumbricals'are'responsible'for'synchronsing'the'various'precision' actions'of'the'digits'and'for'optimising'digit'posture'and'position'so'as'to' get'the'best'advantage'for'the'powerful'flexors'and'extensors.'

PRECISION/COORDINATION' • The'Intrinsic'muscles'are'also'responsible'for'the'bulk,'shape'and'resting' posture'of'the'hand' SHAPE/MUSCLE'BULK' • The'intrinsics'are'also'essential'for'stability'of'hand'joints,'especially'the' MP'joints.' STABILITY' The'Lumbricals' • The'Lumbricals'

• Arise,'uniquely,'from'tendon'and'insert'into'tendon'

• Origin:'the'Flexor'digitorum'profundus'tendons'in'the'palm'

• Travel'on'the'radial'side'of'each'digit'

• Insert'into'the'long'extensors''

Lumbrical+=+Worm+like+

THE'INTEROSSEI'' 2'groups,'Palmar'and'dorsal' Palmar'interossei:'small'and'arise'from'one'metacarpal'bone'(their'own)' Dorsal'Interossei:'Larger'and'arise'from'the'adjacent'metacarpal'bones'of'the'space'in' which'the'lie.' ' ACTIONS:' PAD:'Palmar'interossei'ADDuct' DAB:'Dorsal'interossei'ABDuct' ' The'axis'of'the'hand'is'the'middle'finger'(adduction'and'abduction'is'towards'or'away'from' the'middle'finger|).' Thus:'The'middle'finger'has'no'Palmar'interossei'(it'cannot'be'adducted'towards'itself)'but' has'two'dorsal'interossei,'since'it'can'abduct'to'either'side.' The'Interossei' • The'largest,'strongest'interosseus'is'the'1st'Dorsal'interosseous'

• It'arises'from'Thumb'and'index'metacarpals' • It'provides'strong'adduction'of'the'thumb,'as'in'strong'key'grip'

• It'also'abducts'the'index'(in'old'nomenclature'it'was'known'as'Abductor+ Indicis).' The'1st'Dorsal'Interosseous'

Dorsal Palmar • The'long'extensors'down'the'dorsum'of'the'digit'receive'the'insertions'of' Palmar'and'dorsal'interossei'and','on'the'radial'side,'the'lumbrical.'

• The'interossei'also'insert'into'the'base'of'the'proximal'phalanx' • The'lumbrical'does'not'insert'into'bone.' Ulnar' Radial' Dorsal Volar • The'group'of'fibres'formed'by'the'long'extensors,'the'interossei'and'the' lumbricals,'flow'distally'and'divide'into'a'complex'arrangement:'

1.'The'central'slip:'this'inserts'into'the'base'of'the'middle'phalanx' 2.'The'lateral'bands,'which'peel'away'from'the'centre,'then'converge'again' to'insert'into'the'base'of'the'distal'phalanx.'

• This'arrangement'has'an'important'biomechanical'basis.'It'ensures'that' when'fingers'are'extended'from'the'position'of'full'flexion,'the' interphalangeal'joints'open'in'synchrony'i.e.'all'joints'in'the'digit'open' into'extension'simultaneosly.' Central'Slip' Lateral'Bands' • The'interossei'either'side'of'the'long'digits'contribute'the'dorsal'extensor' expansion,'the'hood'over'the'metacarpals'whose'main'function'is'to'keep' the'long'extensor'aligned'on'the'back'of'the'MP'joint.'

• 'The'interossei'are'like'guy'ropes'either'side,'stabilising'the'extensor' tendon.' INSERTION'OF'INTEROSSEUS'AND'LUMBRICAL'INTO'EXTENSOR'MECHANISM' • Wasting'of'the'interossei'produces'the'‘empty’'hand.'Note'the'guttering' between'the'metacarpals'

PAD:'Palmar'Adduct' ' DAB:'Dorsal'Abduct'

ABDUCTION'' AND'ADDUCTION' Function'of'the'Interossei' and'Lumbricals'

1. Stabilisation'of'the'MP'joints' • Functionally,'the'most'important'role'of'the'Interossei'and'lumbricals'is' the'stabilisation'of'the'MP'joint.''

• Without'their'palmar,'flexing,'force,'the'MP'joint'buckles'into'unstable' hyperextension'(similar'to'the'thumb'MP'joint'seen'earlier).'

• The'long'extensors'use'up'their'excursion'on'the'MP'joint'

• The'IP'joints'remain'flexed'–'this'is'the'basis'of'the'Claw'Hand'

Function'of'the'Interossei' and'Lumbricals'

1. Stabilisation'of'the'MP'joints'

2. Coordination'of'flexor'and'extensor'forces' (lumbricals)' • The'lumbricals'uniquely'connect'the'flexor'apparatus'to'the'extensor' apparatus.'

• Action'of'the'flexor'profundus'produces'strong'flexion'but'also,'by'pulling' on'the'contracting'lumbrical,'produces'opposing'extension'forces'on'the' PIP'and'DIP'joints.'

• Flexion'wins'of'course,'but'this'restraining'action'on'the'IP'joints'ensures' that'flexion'at'all'three'joints'occurs'simultaneously'(If'the'hand'is'flexed' into'a'fist'from'the'fully'extended'position,'all'digit'joints'close' simultaneously'and'smoothly'from'full'extension'to'full'flexion).'

Function'of'the'Interossei' and'Lumbricals'

1. Stabilisation'of'the'MP'joints'

2. Coordination'of'flexor'and'extensor'forces' (lumbricals)'

3. Abduction'and'Adduction'of'the'long'digits' (interossei)'

• The'interossei'also'ABduct'and'ADduct.'

• When'one'reaches'for'an'object'the'MP'joint'has'lax,'side'to'side'play.'This' enables'the'interossei'to'abduct'the'digits'to'be'able'to'conform'to,'and' grasp,'the'object.'

• When'the'digits'flex'around'the'object'the'MP'joint'is'stable'(the' collateral'ligaments'are'taut'–'see'above'–'and'the'finger'is'thus'stabilized' around'the'object'during'grip.'

• The'Interossei'and'Lumbricals'flex'the'MP'joints'and'extend'the' Interphalangeal'joints' MPJ

PIPJ

Overaction/Scarring'' of'the'Intrinsics:'Intrinsic'Tightness'

DIPJ • Excessive'action,'or'scarring'produces'stiff'flexion'of'the'MP'and'stiff' extension'of'the'IP'joints.'This'is'known'as'INTRINSIC'PLUS'

• Paralysis'and'loss'of'Interossei'and'Lumbrical'activity'produces' hyperextension'instability'of'the'MP'joints'and'there'is'no'opposition'to' flexion'of'the'IP'joints.'This'is'the'Claw'Hand'also'known'as'INTRINSIC' MINUS' +

Intrinsic Plus (tightness) Intrinsic Minus (paralysis) INTRINSIC'MINUS' ' The'Claw'Hand' PIPJ

MPJ DIPJ

The'Intrinsic'Minus'(claw)'hand'is'still'able'to'roll'up'all'digits'and'make'a'fist,' i'so'why'does'it'matter?'

• The'crucial'feature'is'a'loss'of'synchrony'of'closure'of'the'digits'and'the' instability'of'the'MP'joint.'

• As'a'result,'an'attempt'at'surrounding'and'grasping'an'object'produces' contact'between'the'fingertips'and'the'metacarpal'heads'in'the'palm.' This'is'very'inefficient'and,'in'insensate'hands,'produces'high'pressure'on' these'points'of'contact'and'possible'ulceration.'

PREiOP' POSTi'OP' The'Flexor'Tendons' • Nine'flexor'tendons'are'packed'into'the'carpal'tunnel'along'with'the' median'nerve'

• Two'flexors'to'each'digit'(FDS'and'FDP)'and'the'Flexor'pollicis'longus'

• The'tendons'are'surrounded'by'synovial'sheaths.'These'are'variable'in' distribution'and'in'communication'between'digit'and'forearm'

• Their'clinical'significance:'

1.'Thickening'of'the'synovial'sheath'can'produce'Carpal'tunnel'syndrome'

2.'Infection'in'the'finger'can'track'into'the'carpal'tunnel'and'the'distal' forearm'through'this'readyimade'compartment.'

• From'the'narrow'constraints'of'the'carpal'tunnel'the'flexors'fan'out' towards'the'thumb'and'digits,'lying'beneath'the'Neurovascular'structures' and'beneath'the'Palmar'aponeurosis.'

• The'Flexor'Digitorum'superficialis'separates'into'individual'tendons.'

• This'enables'the'digits'to'act'independently'of'each'other' Flexor'Digitorum'Superficialis' • The'tendons'of'Flexor'Digitorum'Profundus'are'usually'matted'together' with'a'variable'independence'of'the'tendon'to'the'index'as'in'this'case.''

• This'means'that'Flexor'Digitorum'profundus'usually'flexes'in'‘Mass'action’' i.e.'individual'digits'cannot'flex'without'flexing'their'neighbours'as'well.' Flexor'Digitorum'Profundus' • Both'flexor'tendons'enter'the'tight'flexor'tendon'sheath,'a'fibrous'tunnel' which'holds'and'directs'the'flexor'tendons'on'the'palmar'aspect'of'the' digit' The'Flexor'Tendon'Sheath' • The'fibrous'flexor'tendon'sheath'is'reinforced'in'parts.''

• These'thickened'areas'of'the'wall'of'the'flexor'sheath'are'known'as' pulleys'

• They'are'strongest'and'best'developed'over'the'shafts'of'the'bones'(the' phalanges)'and'weakest'over'the'joints.'

• They'are'numbered'–''

• ‘A’'pulleys'are'over'the'shafts;'‘C’'pulleys'are'over'the'joints'

• the'strongest'are'the'A2'and'A4'pulleys.' 'A1''''''''''''''''''''A2''''''''''''A3''''''''''A4''''''''A5' '''''''''''''''''''''''''''''''''''''''C1'''''''C2''''''''''''C3'

''''''''''''''' • In'the'fully'flexed'position'the'weaker'parts'(over'the'joints)'concertina' together'so'that'at'full'flexion,'there'is'one'continuous'strong'restraining' tunnel.'

• There'are'many'variations'to'the'pulleys'and'tunnel'consistency'but'the' general'principle,'common'to'all,'is'that'the'pulleys'are'strongest'over'the' shafts'of'the'phalanges.'

• Loss'of'a'pulley'causes'the'tendon'to'bowstring'and'this'diminishes'power'

• The'Thumb'has'a'similar,'though'shorter,'system'of'pulleys' A2' ' ' Y' ' A1' • Percentages'of'movement'at'each'joint' 10%' 45%' 45%'

dipj' pipj' mcpj' • THREE'LAYERS'OF'FLEXORS'

• Palmaris'Longus'(weak'Flexor'inserting'at'the'base'of'the'proximal' Phalanx'via'the'palmar'aponeurosis)'

• Flexor'digitorum'superficialis'(strong'flexor'inserting'into'middle'phalanx)'

• Flexor'digitorum'profundus'(strong'flexor'inserting'into'the'base'of'the' distal'phalanx'

• This'system'requires'a'series'of'Chiasmata'which'permit'each'deeper' tendon'to'emerge'through'the'one'above'it'

Def:+Chiasma:+a+crossing+or+intersection+

• The'Palmar'Aponeurosis'divides'at'the'level'of'the'MP'joint'to'let'the'FDS' and'FDP'through.'

• The'FDS'divides'inside'the'flexor'tunnel,'to'permit'the'FDP'through,'on'its' way'to'its''more'distal'insertion'

• The'two'slips'of'the'FDS'divide'and'spiral'around'the'FDP,'then'rejoin' before'inserting'into'the'entire'length'of'the'middle'Phalanx'

• Over'a'short'stretch,'the'FDS'tendon'virtually'forms'a'tunnel'through' which'passes'the'FDP'tendon'

• The'flexor'tunnel'is'only'two'thirds'fibrous.'The'dorsal'aspect'consists'of' bare'bone'

• Any'disruption,'however'minor'of'this'well'fitting'structure,'will'impair' function.'

• Adhesions'of'tendon'to'tunnel'wall'are'a'common'cause'of'impair' function'

The'Vasculature' • The'main'arterial'trunks'beyond'the'cubital'fossa'are'the'Ulnar'artery'and' the'radial'artery'

• They'are'the'terminal'branches'of'the'Brachial'artery'in'the'cubital'fossa.' • The'ulnar'artery'is'virtually'always'dominant,'thicker'and'wider'calibre' than'the'radial.'

• In'the'forearm'two'other'major'arteries'are'given'off'high'in'the'cubital' fossa:'The'anterior'and'posterior'interosseous.'These'run'anterior'and' posterior'to'the'interosseous'membrane'with'the'eponymous'nerves' RADIAL' ARTERY'

ULNAR'' ARTERY' • The'radial'artery'is'palpable'and'superficial'throughout'its'course'in'the' forearm.'

• It'enters'the'hand'by'passing'dorsal'to'the'wrist'crossing'the'anatomical' snuff'box' Brachial'Artery'

The'Radial'Artery' • The'ulnar'artery'travels'deep'to'Flexor'Carpi'Ulnaris'and'does'not'emerge' until'the'distal'forearm'before'entering'the'hand'through'Guyon’s'canal' Brachial'Artery'

The'Ulnar'Artery' • The'radial'artery'leaves'the'forearm'and'crosses'the'anatomical'snuff'box' to'enter'the'hand'through'the'1st'Dorsal'interosseous'muscle'

• The'ulnar'artery'leaves'the'forearm'by'emerging'from'beneath'FCU'and' passing'superficial'to'the'flexor'retinaculum,'through'Guyon’s'canal' Ulnar'Artery'' and'' Radial'Artery' Ulnar'Nerve' The'radial'artery'leaving'the'forearm'beneath'APL/EPB'' and'giving'a'major'branch'to'the'carpus' • The'radial'artery'passes'beneath'APL'andEPB'to'enter'the'snuff'box,' which'it'crosses.'

• It'then'goes'deep'between'the'two'heads'of'the'1st'Dorsal'Interosseous'

• Once'through'the'1st'Dorsal'interosseous,'the'radial'artery'lies'in'a'space' between'the'1st'DI'and'the'adductor'pollicis'

• While'in'this'space'it'gives'off'the'arteria'radialis'indicis'(radial+artery+to+ the+index)'and'the'arteria'princeps'pollicis'(main+artery+to+the+thumb)+

• It'then'enters'the'hand'by'passing'between'the'two'heads'of'the'adductor' pollicis' The'Secret' Compartment' 1stDI' 1stDI

PI' PI'

APB' AP' Add'P' THE'DEEP'PALMAR'ARCH'

• In'the'depths'of'the'hand'(over'the'bases'of'the'metacarpals)''the'radial' artery'forms'the'deep'palmar'arch'

• This'arch'runs'with'the'motor'branch'of'the'Ulnar'nerve' • This'latter'nerve'is'the'main'supply'to'most'of'the'intrinsic'muscles'of'the' hand.'

• The'general'plan'of'the'vasculature'in'the'hand'is'of'arches'running' transversely'and'fed'from'both'radial'and'ulnar'arteries'eg'Carpal'arches,' palmar'arches'

• These'give'off'longitudinal'vessels'running'into'the'digits'eg'metacarpal' and'common'digital'arteries' Carpal' Arches'

Deep' Palmar' Arch' Metacarpal+arteries+

Superficial' Palmar' Arch' Common+Digital+ arteries+ • The'common'digital'arteries'come'off'the'superficial'palmar'arch'

• This'is'the'end'branch'of'the'ulnar'artery'and'is'frequently'incomplete,' ending'at'the'index.'

Superficial'palmar'arch''''''''''''''Common'Digital'Arteries' • There'is'a'similar'plan'in'the'digits,'with'transverse'arches'at'the'level'of' the'joints'and'longitudinal'vessels'which'travel'along'either'side'of'the' digit'

• The'tendon'is'supplied'with'blood'via'the'vicula.'

• These'are'short'or'long'(Vincula'brevia'and'Vincula'lunga)' • In'essence,'they'are'a'mesentery'with'blood'supply'to'the'flexor'which' permits'supply'even'as'the'tendon'glides'back'and'forth'

• As'the'tendon'moves,'the'vincula'sweep'backwards'and'forwards'like' windscreen'wipers' The'Flexor'Tendon'Vincula' • All'of'the'named'arteries'are'simply'the'main'highways'

• The'hand,'like'most'parts'of'the'body'is'one'continuous'mesh'of'vessels,' some'of'which'are'large'and'dominant.'

• The'analogy'is'of'the'mesh'of'roads,'major'and'minor,'in'a'country,'and' the'named'vessels'are'only'the'motorways.' Gunther'van'Hagen' 2005'

Guillermo' Loda'' 1991' • The'venous'drainage'is'low'pressure'and'mainly'lies'on'the'dorsum'of'the' hand'

• This'protects'it'from'compression'during'strong'grip'which'would' otherwise'impede'flow.'

• There'are'no'significant'digital'veins'running'with'the'digital'arteries' Venous'Drainage,'mostly'Dorsal' Zancolli'1984' John'Hunter' 1728i1793' ' Surgeon,' Anatomist'