-
Muscle characteristics
- Individual muscle firbres arranged in parallel lines
- collected into bundles
- covered by fibrous tissue (fascia)
- attached to rigid structure
- origin- usually proximal
- insertion- usually distal
-
Attachments of skeletal muscle
- Origin or insertion:
- directly to bone (rough surface, boney tuberocity)
- via tendons (condensation of deep fascia into cords, less bulky across joints, small area of attachment, may have separate centre of ossification)
- via aponeurosis: (condensation of deep fascia into sheets, long area of attachment, muscles in areas w/ limited access to bone)
- ex: superficial fascia, and cervico-thoraco-lumbar fascia
-
Muscle actions:
- Belly contracts and shortens muscle
- pulls points of attachment close togeter
- pivot at joint (decrease angle- flexion, increase angle- extension)
- action depends on which joints crossed and aspect of joint
- *antagonistic pairs of musciles- opposite action
-
Intrinsic muscles
- origin and insertion w/in appendicular skeleton
- movement and extension
-
Extrinsic muscles:
- origin on axial skeleton
- insertion in appendicular skeleton
- movement of limb relative to trunk
- protraction and retraction of limb
-
Pivotal point (PP) of scapula
- No joint present between forelimb and trunk in domestic animals
- muscular attachements only
- scapular glide over thorax
- PP midway down scapula
-
Brachiocehpalic muscle
- Cephalic= head
- brachium= arm
- origin= cervicothoracic fascia
- insertion= humerus (aponeurosis)
- PROTRACTOR (also acts across shoulder)
- (cleidocervicalis/cleidomastoideus/cleidobrachialis)
-
Clavical
- Dog: clavical insertion is a fibrous band
- Cat: has a bony remnant visible on radiographs, cranial to shoulder
-
Latissimus dorsi muscle
- (extrinsic)
- latus= broad
- dorsi= back
- "boradest muscle of the back"
- origin= thoracolumbar fascia
- insertion= humerus (aponeurosis)
- RETRACTOR (also acts across shoulder)
- propulsion
-
Serratus ventralis muscle
- Extrinsic
- Origin: thoracis wall/ribs and cervical vertiebrae/neck
- insertion: proximal scapula/medial aspect (proximal to pp)
- *muscle is located between forelimb and trunk*
- Function: cranial portion= Retractor, Caudal portion= Protractor
-
Abductors vs adductors:
- Abductors: move limb away from midline- muscles located proximal to PP and limb
- Adductors: move limb towards midline- located distal to PP and medial to limb
-
Trapezius Muscle
- Origin= cervicothoracic fascia
- insertion= proximal scapular spine
- 2 parts (cranial and caudal)
- no effect on shoulder
-
Rhomboideus muscle
- lies deep to trapezuius
- origin= cervicothoracic fascia
- insertion= dorsal border of scapula
- abductors of limb
- no effect on shoulder
-
Pectoral Muscles
- Origin= sternum
- insertion= medial humerus
- Deep and superficial groups
- adductor of limb
-
Intrinsic muscles
- origin and insertion w/in appendicular skeleton
- no effect on limb relative to trunk
- move joints w/in limb
- (flexion and extension)
-
Humerus
- Long Bone
- S-shape
- head, body condyle
- brachial/musculospiral groove
- proximal end: head (artivular surface, convex, smooth surface, articulates w/ glenoid cavity of scapula at shoulder joint, greater tubercle, greater tubercle-lateral, lesser tubercle-medial, intertubercular groove- smooth for tendon of otigin of biceps brachii muscle to pass through)
- distal end: condyle (medial half larger than lateral), medial epicondlylle, lateral epicondyle, articular surface w/ elbow joint, trochlea (larger, located medially, central depression, articulates w/ radius and ulna), capitulum (smaller, located laterally, articulates w/ radius), olecranon/ulnar fossa-caudal, radial foss-cranial/proximal to articular surfaces, spratrochlear foramen (nothing passes through, may not be present in short legged dogs (only in dogs)
-
Humerus differences in cats:
- Proximal features and articular surfaces same as dog
- distal end: olcranon fossa, radial fossa, NO supratrochlear foramen~!
- instead they have a supracondyloid foramen (brachial artery, median nerve, vulverable in fractures)
-
Humerus development and palpation
- Centres of ossification: proximal epiphyses, body, condyle (medial epicondyle, medial half, lateral half) 5 total
- Palpation: greater tubercle (shoulder joint), lateral epicondyle and medial epicondyle ( elbow oint
-
Humerus trama
- supratrochlear foramen= weak point
- medial half of condyle larger than lateral half
- fracture most commonly through lateral half
- may involve joint- poorer outcome
- no blood vessels thru
-
Efferent Nerve Supply
Brain to structure (motor fibres eg.. movement)
-
Afferent nerve Supply
- Structure to brain
- sensory fibres eg. pain, temp, pressure, etc
- Proprioception (location of limb in space- automatic)
-
Motor Nerves
carry efferent and afferent fibres to structure
-
Mixed nerves
carry afferent/sensory from the skin surface
-
Spinal reflexes
occur w/o brain being involved eg. patellar reflex
-
Brachial plexus supply
- Latissimus dorse (retractor), serratus ventralis (retractor and protractor), pectorals (adductor)
- supplies ALL intrinsic muscles
(DOES NOT supply Brachiocephalicus, trapezius and rhomboideus)
-
Types of Joints:
- Fibrous
- Carilagenous
- Synovial
-
Fibrous Joints:
Little Movement (eg. skull sutures)
-
Carilagenous Joint
- Synchondrosis/synarthrosis
- Little movement
- Pelvic/mandibular sumphysis
-
Synovial Joint
- Allows large range of motion between bones
- most limb joints
- typical features: Hyaine cartilage (covers articular surfaces, reduce friction, flexible, avascular, no nerves)
- synovial fluid (viscus, nourishes cartilage, lubricates)
- synovial membrane (produces synovial fluid, physical barrier to contain fluid)
- Joint capsule (fibrous layer, incorporates synovial membrane, attaches round osteochondral junction (bone cartilage))
-
Ligaments
- Fibrous materal condenses to form ligaments
- run from bone-bone
- collateral ligaments support joints (medial and lateral ONLY)
-
Joint Movement:
- Flexion: decreased angle, folded limb, non weight bearing position
- Extension: increased andly, streching limb, weight bearing
-
Shoulder Joint components:
- Scapula (glenoid cavity), humerus (head)
- palpable landmarks (acromion process, greater tubercle)
- Typical synovial joint features except: poorly developed collateral ligaments
- Bicipital bursa
- muscle support
-
Bicipital Bursa (shoulder joint)
- Joint capsule extends into intertubercular groove (between greater and lesser tubercles)
- wraps around tendon of origin of biceps brachii (originates on supraglenoid tubercle)
- Held in place by transverse ligament
-
Lateral support of Shoulder joint
- Supraspinatous muscle: supraspinous fossa-> I= Greater tubercle
- Infraspinatous muscle: Infraspinous fossa-> I= Distal to greater tubercle
- Suprascapular nerve- motor fibres ONLY
-
Medial Support of Shoulder Joint
- Subscapularis muscle
- subscapular fossa-> I=lesser tubercle
- subscapular nerve- motor fibres ONLY
-
Shoulder Joint extensors
- Cross cranial to shoulder joint:
- Brachiocephalicus (extrinsic muscle) nerve non from brachial plexus
- Biceps brachii muscle (O= supraglenoid tubercle, I= Proximal radius, intrinsic muscle) Motor nerve supply- musculocutaneous nerve, motor and sensory fibres
- Bicipital bursa (protects tendon of origin, intertubercular groove, transverse ligament)
-
Shoulder joint flexors
- cross caudal to shoulder joint
- Latissimus dorsi (extrinsic muscle) nerve from brachial plexus
- Deltoideus muscle (2 heads) (O1-scapular spine, O2- acromion process, I- lateral aspect humerus)(intrinsic muscle) Axillary nerve, motor and sensory fibres
- Teres Major (O- caudal border of scapula, I- medial humerus) axillary nerve, motor and sensory fibres
- Teres Minor: overlies lateral aspect joint space
- Triceps Muscle: multiple heads, long head: (O- caudal border scapula, I- Olecranon of Ulna) radial nerve motor and sensory fibres
-
Clinical considerations
- Osteochondrosis (OCD): developmental dz, erosion of articular cartilage, subchondral bone may be affected, visible on radiograph, characteristic location, pain causes lameness, leads to DJD/arthritis
- Degenerative Joint Disease (DJD): new bone formation around joint capsule attachment, osteochondral junction, characteristic locations on rads, painful while forming, lameness
- soft tissue conditions: bicipital bursitis- U/S used for Dx
-
Radius and Ulna (breif)
- Long bones
- Paired
- Radius is main weight bearing
- Ulna is longer/ leverage
-
Radius proximal end
- Head
- Fovea capitis, articular surface (elbow joint)
- Neck
- Body
-
Radius Distal end
- Trochlea (articular surface w/ carpus)
- styloid process ("pen") medial, attachment medial collateral ligament or carpus
-
Ulna Proximal end
- Olecranon process
- anconeal process (beak shaped, fits into olecranon/ulnar fossa of humerus)
- trochlear notch (articular surface/elbow joint)
- Lateral coronoid process
- medial coronoid process
- radial notch (articulates w/ radius)
- Proximal articulation (radius/head, radial notch of ulna, held by annular ligament (runs lateral to medial coronoid process, rotation possible)
-
Ulna Distal End
- Styloid process (attachment lateral collateral ligament of carpus)
- Distal articulation (fibrous joint, some rotation possible)
- interosseous space (between bodies, interosseous ligament, fibrous joint)
-
Evolution of Radius and Ulna
- Toes rotated cranially
- elbows rotated caudally
- radius and ulna therefore rotate around eachother
- Proximal: ulna most medial projection
- Distal ulna most lateral projection
-
Radium and ulna CAT
- Square olecranon
- radius and ulna similar diameter
-
Radius and Ulna Palpation and Development
- Palpation:
- Ulna: Olecranon process, lateral styloid process
- Radius: Medial Styloid Process
- Development:
- Radius: proximal epiphyses, body, distal epiphyses (3)
- Ulna: Olecranon process, anconeal process, body, distal epiphyses (4)
-
Radius and Ulna development clinical considerations
- Large contribution to limb length
- must grow together
- growth plates= weak point= susceptible to damage
- Ulna in particular due to shape
- if one stops before other= angular limb deformaties
- Fractures: radius bears most weight= requires fixation
- Primary bone tumors (osteosarcoma)- predilection sites (proximal humerus, distal radius, distal ulna)
-
Elbow Joint
- Humerus w/ radius & ulna
- Humerus: Trochlea, articulates w/ trochlear notch of ulna & fovea capitis of radius. Capitulum: articulates only w/ fovea capitis of radius
- Typical features of synovial joint (joint capsule- osteochondral jnc, incorporates proximal radio-ulnar articulation)
- stability: collateral ligaments (humerus- radius and ulna), Boney structures (anconeal process (ulna) Olecranon/ulnar fossa (humerous))
-
Elbow Joint Movement (Humerus- radius & ulna)
- Between humerus- radius & Ulna
- Limited to flexion and extension
- Ulna acts as lever
- Elbow extensors insert into olecranon (avulsion possible)
-
Elbow joint Movement (radius and ulna)
- Rotation possible
- annular ligament
- interosseous ligament
- fibrous joint distally (pronation= face down, Supination= face up)
- dogs= rotation limited
- cats= large amount rotation eg. climb trees!
-
Elbow Joint Clinical Considerations
- Elbow dysplasia
- OCD
- ununited anconeal process
- fragmented medial coronoid process
- elbow incongruity
- DJD
-
Elbow Joint Muscles Extensors (triceps):
- Triceps Muscle (long head): O- caudal border scapula
- (lateral head): O- Lateral aspect humerus (only part that effects shoulder)
- (Medial head): O- Medial aspect humerus
- (accessory head)
- Radial nerve supply
-
Elbow Joint Muscles Flexors
- Triceps muscle
- Biceps brachii (O- supraglenoid tubercle, I- Proximal radius) Musculocutaneous nerve
- Brachialis muscle (O- caudal aspect humerus, I- proximal radius) follows musculospiral/brachial groove, musculocutaneous never supply
-
Elbow Joint Muscles Rotators
- Supinator Muscle (O- lateral epicondyle) radial nerve
- Pronator teres muscle (O- medial epicondyle) median nerve
- I- proximal radius
-
Elbow Joint Muscle Clinical Considerations
- Dissect between muscles (rather than cutting them)= less damage= faster healing
- Proximal humerus: dissect between brachiocephalicus and deltoideus
- Midshaft: between brachiocehpalicus and brachialis
- distal humerus: between brachialis and triceps
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Forelimb Blood Supply
- Limb naturally in extended position
- blood vessels cross flexor aspects of joints (avoids stretching of vessels)
- arterial supply (oxygenated blood from heart to peripheral tissues, major vessel runs down limb, changes name according to region)
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Forelimb Arterial Supply
- Subclavial artery: runs round 1st rib- axila
- Axillary arter: runs through axilla
- Brachial artery: runs down brachium, branches
- Branches into: Median artery: runs down medial aspect antebrachium, branches- radial artery, terminates in superfical palmar arch, (superficial palmar arch, palmar common digital arteries)
- superficial brachial artery: runs down cranial aspect antebrachium (superficial dorsal supply, dorsal common digital arteries)
- Radial artery: deep palmar arch, palmar metacarpal arteries, ddeep dorsal supply, dorsal metacarpal arteries.
-
Forelimb arterial supply (arterial supply to digit)
- 4 vessels per digit
- palmar supply most important
- axial palmar proper digital A largest
- implications when wmputating toes
-
Forelimb Venous Drainage
- Veins- take deoxygenated blood back to heart
- deep system: follows arterial supply
- superficial system: cephalic vein, drains into jugular vein/vena cava
-
Cephalic vain- clinical considerations
- access to systemic circulation
- pressure to raise vein
- valves allow blood to pool
- reslease pressure before inject
- fluid enter vein not SQ tissues!!
- radial nerve runs alongside it- providing cutaneous sensation to cranial aspect of forelimb
- pain and necrosis...
-
Carpus Terminology Changes
- Composed of Carpal bones
- short bones
- no medullary cavity
- centre= cancellous bone
- Proximal, distal
- dorsal, palmar
-
Carpus Proximal row:
- Radial/Intermediate carpal bone (fused) (RCB)
- Ulnar carpal bone (UCB)
- Accessory Carpal bone (ACB)
-
Carpus Distal Row Bones
- 1st carpal bone
- 2nd carpal bone
- 3rd carpal bone
- 4th carpal bone
-
Carpus development
- single centre of ossification
- except: accessory carpal bone= 2 on all species
- fused radial/intermedial carpal bone=2 due to origin
-
Carpal Joints (3)
- Antebrachio-carpal joint: between antebrachium and carpus (radius- RCB & UCB) (Ulna- (UCB & ACB)
- Middle carpal joint: proximal and distal rows
- Carpo-metacarpal joint: distal row and metacarpal bones
- (Intercarpal joints- vertical)
-
Carpal joints- movement
- Standing= extension
- Large range of flexion: most moevement antebrachio-carpal joint, least carpo-metacarpal joint, some between bones)
- ACB acts as lever for distal limb: insertion of some major carpal flexor, counteracting by palmar ligament
-
Carpal Joint Support
- Typical Synovial joint: single joint capsule extending proximally between radius and ulna, distally between metacarpal bones- poor communication between compartments)
- Collateral ligaments: Lateral- ulna (lateral styloid process) to 5th metacarpal bone, Medial radius (medial styloid process) to 2nd metacarpal bone
- Styloid processes vulnerable
- Intracarpal ligaments
- Palmar aspect: Fibrocartilagenous reinforcement (friction free, passive maintenance of joint extension, prevention of collapse)
- Retinaculum= sleeve of deep fascia
- Dorsal retinaculum: dorsal survace, jumps from bone to bone, allows flexion, forms transverse ligaments to hold tendons
- Palmar/flexor retinaculum: runs down caudal surface, attaches to lateral aspect accessory carpal bone, crosses from ACB to medial aspect carpus, forms carpal canal
-
Carpal Canal
- Dorsal boundary: Fibrocartilagenous reingorcement of palmar aspect of carpal joint capsule
- Lateral Boundary: ACB
- Palmar boundary: Palmar/Flexor retinaculum
Dog: Deep digital flexor tendon through tunnel, blood vessels and nerves, suprficial digital fleor tendon outside
-
Carpus= Palpation
- Accesory carpal bone
- joint spaces (flexion)
- medial stylid process (radius)
- lateral styloid process (ulna)
-
Manus
- Dogs and Cats= digitigrade (bear weight on digits)
- 4 weight bearing and 1 vestigial
- numbered medial to lateral
- Digit: proximal phalanx, middle phalanx, distal phalanx, sesamoids
-
1st digit= dew claw
- Vestigial
- medial aspect
- non-weight bearing
- has 3 elements (debate as to which is missing)
- commonly removed in puppies
-
Metacarpus
- four metacarpal bones
- long bones
- convex dorsal surface
- base=poximal end (forms carpo-metacarpal joint)
- body= midshaft
- head= distal end
- raiesd sagittal ridge- extends to palmar aspect
-
Digit (proximal and middle phalanx)
- Proximal Phalanx (PP): long bone, sagittal groves at both ends
- Middle Phalanx (MP): Long bone, proximal sagittal ridge, distal- sagittal groove
-
Digit (distal phalanx)
- Long bone debate
- ungual process
- ungual crest (round root of claw, very vascular)
- extensor process (extensor tendons)
- palmar process (flexor tendons)
-
Metacarpus Sesamoid Bones
- Metacarpo-phalangeal joint
- 2 x proximal sesamoids: palmar aspect, either side of sagittal ridge, protect flexor tendons
- 1 x dorsal sesamoid: protect extensor tendons
-
Manus Development
- MC(2) body and distal end
- PP (2) Body and Proximal end
- MP (2) Body and proximal end
- DP (1)
-
Joints of Manus
- Metacarpo-phalangeal joint
- Proximal Interphalangeal Joint
- Dipstal interphalangeal joint
- All typical synovial joints
- flexion and extension
- stability: collateral ligaments, sagittal ridge/groove
-
Metacarpo-phalangeal joint
- Resting position= extended
- interosseous muscle and proximal sesamoids
- sling configuration suspends Metacarpo-phalangeal joint
- supported by metacarpal foot pad
-
Distal Inter-Phalangeal Joint
- Deep Digital Flexor Tendon
- Common Digital extensory tendon
- Dorsal elastic ligament (proximal end MP, extensor process DP)
- Dog: forces balanced to maintain tip of claw above horizon problem if DDFT is severed
- Cat: claws not visible- very strong dorsal elastic ligament, DIP joint hyperextended, claw rests in skin fold/sheath- not visible- remain sharp for hunting/climbing (to expose DDFT flexes joint, or manual pressure to digital pad)
-
Muscles of Antebrachium
- Affect joints of carpus and digits
- muscle belly- antebracium
- tendon of insertion- distal to carpus
- extensors of distal limb: originate lateral epicondyle of humerus, run over dorsal aspect carpus, radial nerve
- flexors of distal limb: originate medial epicondyle, run over palmar aspect carpus, median and ulnar nerves
-
Extension of carpus
- origin= lateral epicondyle, radial nerve
- extensor arpi radialis muscle (I= metacarpal bones)
- Abductor pollicus longus/Extrnsor carpi obliquus muscle: crosses at level of carpus- useful land mark, sesamoid in tendon of insertion
- extensor carpi ulnaris/ulnaris lateralis muscle (I= 5th metacarpal bone and Accessory carpal bone
- flexion or extension depending on position of limb
-
Extension of carpus and digits
- origin= lateral epicondyle, radial nerve
- common digital extensor muscle (I= all digits), distal phalanx- extensor process, brances to all digits
- lateral digital extensor muscle (I= 4th and 5th digits) distal phalanx- extensor process (lateral digits only)
-
Flexion of Carpus
- Origin= medial epicondyle, median and Ulnar nerves
- Flexor Carpi Ulnaris muscle (O= olecranon, I= ACB 2 heads)
- Flexor Carpi radialis muscle (I= metacarpal Bones)
-
Flexion of carpus and digits
- origin= medial epicondyle, median and ulnar nerves
- Superficial digital flexor muscles (I= all digits (middle phalanx)) runs outwith carpal canal
- deep digital flexor muscle (O- also radial and ulnar heads, I= All digits) distal phalanx- palmar process, tendon runs through carpal canal passes through SDFT
-
Footpads
- Carpal/stopper pad
- metacarpad pad x 1
- Digital pads x 4
- functions: resistanct to trauma/wear & tear, traction, anti-concussive, protect deep structures, dupport digit
-
Skin (Epidermis/dermis)
- Epidermis: cells constantly produced by germinative later, cells age as move outwards, dead at surfact and slough, constant replacement, no blood supply, no nerve supply, insensitive and no bleeding
- dermis: blood supply, nerve supply, sensitive and bleeds, supports germinative layer- active production of skin celss
-
Footpad modifications
Trauma resistance: increased skin thickness, increased turnover of cells, deposition of keratin, rough surface, sweat glands, variable amounts pigmentation
-
Footpad components
- Skin (epidermis, germinative layer, dermis)
- superficial fascia
- Digital cushion (fibrous tissue, elastic tissue, fat, vascular channels)
- Function= shock absorption
-
Footpad clinical considerations
- Wounds (elastic tissue and vascular channels)
- sweat (bandaging)
- DDFT (stubbed toe)
-
Claw
- No superficial fascia
- dermis (fused directly to periosteum of ungual process of DP)
- germinative layer (active in 2 areas only)
- epiermis (heavily keratinised= horn)
- stratum tectorum (waterproof surface layer, produced by skin in ungual recesses)
-
Germinative areas of Claw
- Area 1: recess between claw and skin, horn grows over dorsal and lateral surfaces of ungual process, horse-shoe shaped in transverse section/short axis
- area 2: palmar surface of ungual process, horn covers palmar surface
-
Normal claw/growth
- Tip touches ground
- position maintained by dorsal elastic ligament, extensor tendons, balanced by DDFT
- continuous growth
- tips wear naturally
- reduced wear (not walking, walking on soft ground, dew claw, DDFT damage)
- Claw grows in circular fashion (can eventually grow into pad)
-
Claw clinical considerations
- Horn= epidermis (insensitive so can cut)
- Dermis= contains blood and nerve supply- don't cut too far!
- Non-pigmented claws (easier to clip)
- Cats:
- Pressure on pad- unsheath claw
-
Lymphatic system/cardiovascular system
Cardiovascular system: continuous system, leaky capillary bed, exchange of material (eg. fluid, protein), net loss, fluid accumulation (edema and swelling in peripheral tissues)
-
Lymphatic system (basics)
- Rocovery/scavenging system
- series of individual vessels
- thin walled
- run from periphery to thoracic duct
- thoracic duct empties into caudal vena cava
- transports lost material back into systemic circulation
-
Lymphatic system (lymph nodes)
- Filters
- located where lymph vessels converge
- prevent contaminants reaching systemic circulation
- remove invading organisms/bacteria
- contain defence cells
- forelimb lymph nodes (prescapular, axullary)
- enlarge in response to infection
- can use to differentiate between localised/generalised dz
- important in large animals for meat inspection
-
Nervous system- brachial plexus
- Supplies:
- Selected extrinsic muscles: pectoral, latissimus dorsi, serratus ventralis
- all intrinsic muscles: subscapular nerve, suprascapular nerve, musculocutaneous nerve, axillary nerve, radial nerve, median and ulnar nerve
-
Subscapular/suprascapuar nerves
- Motor nerves only- no cutaneous sensation
- subscapular nerve: medial shoulder support, subscapularis muscle
- suprascpular nerve: laterl shoulder support, supraspinatous muscle, infraspinatous muscle
-
Musculocutaneous nerve
- Mixed Nerve
- Sensory: cutaneous sensation to: cranial and medial aspect of elbow, medial aspect of antebrachium (see notes)
- motor: elbow flexors (brachialis muscle, bicesps brachii muscle)
- damage (no compensation- loss of elbow flexion)
-
Axillary nerve
- Mixed nerve
- Sensory fibres: cutaneous sensation to: lateral aspects shoulder and brachium
- motor supply: dedicated shoulder flexors (deltoideus muscle, teres major muscle)
- damage: compensation by latissimus dorsi, long head triceps
-
Median and Ulnar Nerves
- Mixed Nerves
- Sensory Fibres, cutaneous sensation to: caudal and palmar aspect limb, dorsal aspect 5th digit
- motor supply: carpal and digital flexors (flexor carpi ulnaris muscle, flexor carpi radialis muscle, superficial digital flexor muscle, deep digital flexor muscle)
- damage- no compensation- loss of distal limb flexion
-
Radial Nerve
- Mixed Nerve
- sensory fibres, cutaneous sensation to: dorsal and cranial aspect limb except dorsal aspect 5th digit
- motor supply: extensors of elbow (triceps muscle), extensors of carpus and digits (extensor carpi radialis, extensor carpi ulnaris, common digital extensor muscle, lateral digital extensor)
-
Radial nerve route
- Starts medial, passes caudal to shoulder, passes through triceps (supplies triceps)
- follows musculospiral grove (and brachialis muscle)
- branch- lateral epicondyle (supplies distal limb extensors)
- branch- cranial/dorsal aspect limb (runs alongside cephalic vein, supplies cutaneous sensation)
- Humeral fx most common cause of damage
- deficits depend on level of damage
-
Radial nerve damage motor losses
- Proximal level:
- all extensor muscles affected
- cannot extend elbow, carpus, or digits
- cannot weight bear
- limb appears longer than opposite one
- Distal Level:
- Extensors of carpus and digits affected
- cannot extend carpus/ digits
- Triceps intact: can extend elbow, can weight bear if limb extended, can learn to swing leg to compensate
-
Radial nerve damage sensory losses
- Cranial and dorsal aspect limb
- trauma to dorsal aspect paw if drags
- self mutilation
- check sensation using forceps
- check pre-op humeral fracture repair so cannot be blamed
-
Brachial plexus damage
- Tear/avulsion= stretching: high imact collision, head/neck one direction- limb the other, variable degrees of damage, regeneration possible with time, mismatching may result in aberrant sensation
- turnover- effects depend on which nerves affected
- effect on limb: can protract/abduct limb
- cannot retract/adduct limb
- cannot extend/flex limb
- cannot weight bear
- no cutaneous sensation on limb or lateral thorax to level of 3rd intercostal space
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