Canine Forelimb Musculoskeletal Summer 24 - SA Forelimb Exam

Canine Forelimb Dr Sanet Kotzé Contains: Lecture slides Case study example Practice photos LO: 12-31 (Module 1 guidelines) Resources listed in Course Guide/Ch. 1 guidelines 60% of the weight of the animal is transferred to the thoracic limbs when standing. Front limb for support, hindlimb for propul...

Canine Forelimb Dr Sanet Kotzé Contains: Lecture slides Case study example Practice photos LO: 12-31 (Module 1 guidelines) Resources listed in Course Guide/Ch. 1 guidelines 60% of the weight of the animal is transferred to the thoracic limbs when standing. Front limb for support, hindlimb for propulsion The weight of the head, neck, and trunk transfers to the forelimb The forelimb is attached to the trunk via extrinsic muscles (synsarcosis). The weight of the head, neck, and trunk transfers to the forelimb via the serratus ventralis and pectoral mm. Imagine the two thoracic limbs as posts between which the trunk is suspended by the two serratus ventralis as a “sling muscles”. Pictured: scapula (1), humerus (2), radius (3), sternum (4), deep pectoral m. (5), serratus ventralis m. (6), trapezius m. (7), rhomboideus m. (8) TL = thoracic limb = forelimb Cranial view of TLs and thorax Extrinsic Muscles of the Thoracic Limb (TL) Originate on the head, neck, and/or trunk Insert on the Limb Movement occurs in both directions (red arrows): – If no body weight is placed on limb, the limb will move towards head/neck/trunk. – If limb is weight-bearing, then head/neck/trunk will move relative to the limb (which will stay fixed to the ground). Pictured: brachiocephalicus m (2, 2’); omotransversarius m. (3); trapezius m. (5, 5’); latissimus dorsi m. (7); deep pectoral m. (9) Example: deep pectoral m. action (dog digging vs. walking) 2. Muscle propels trunk forward 1. Forelimb moves Limb fixed (weight bearing) Limb lifted (non weight bearing) Shoulder (glenohumeral) joint Ball and socket joint; no collateral ligaments so muscle stabilization needed (Supra-, infraspinatus and subscapularis muscles). Range of movements: primary - extension/flexion; also allows some abduction/adduction, lateral and medial rotation Head of humerus Lateral view Joint capsule (cut open) Cranio-medial view Radiographs: shoulder joint Remember you will see osteology as radiographs in the clinical setting! TVA p. 468 FIG. 16.3 Lateral (A, C and C’) and craniocaudal (B and D) radiographic views of the canine (A and B) and feline (C, C’, and D) shoulder joints; C and D were taken from specimens. 1, Scapular spine; 1’, acromion; 2, supraglenoid tubercle; 3, greater tubercle of humerus; 4, head of humerus; 5, vestigial clavicle. Mm. of Scapula and Shoulder: Deltoideus Lateral views of TL 4 muscles Deltoideus Medial view of TL 3 muscles Subtendinous bursa of Infraspinatus m. Muscles working together: which will assist in weight bearing of the glenohumeral (shoulder) joint? Note: this is an exercise of applying individual m. action beyond basics, you don’t have to “memorize & recite” the slide 1. 2. 3. Supraspinatus m. – Yes (extends, prevents MR) Deltoideus – No (flexes) Infraspinatus m. – Yes (helps extension, prevents 4. Teres minor m. – Only stabilizes (flexes, prevents 5. 6. Subscapularis m. – Yes (extends, prevents Rotation) Teres major m. – Only stabilizes (flexes, prevents 7. Coracobrachialis m. – Yes (extends) MR) Rotation) Rotation) The combined overall effect of the above muscles is extension of this joint, and stabilization Downward force of body mass presses on shoulder Elbow (humeroradioulnar) joint Hinge joint One synovial cavity Strong collateral ligaments Very stable joint, congruent Allows flexion & extension only Anconeal process (#) fits into the olecranon fossa during extension C=capitulum articulates only with head of radius T=trochlea articulates with both radius and ulna Lateral view # C Cranial view: right humerus T Elbow (humeroradioulnar) joint (TVA, p 472) FIG. 16.8 Lateral (A) and craniocaudal (B) radiographic views of the elbow joint of a young dog (A and B) and of a cat (C, C’, and D). The (feline) supracondylar foramen is depicted in Fig. 16.7. 1, Humerus; 1′, medial epicondyle; 1″, supratrochlear foramen; 2, radius; 2′, proximal epiphyseal cartilage; 3, ulna; 3′, olecranon; 3″, apophysis of tuber olecrani; 4, anconeal process; 5, medial coronoid process; Med., medial. Caudal (Cd.) mm. of Brachium: Elbow extension Triceps brachii m. 1. 2. 3. 4. Long head (6) – acts on shoulder and elbow! Lateral head (6’) – elbow only Medial head (6’’) – elbow only (not visible) Accesory head (not visible) – elbow only Tensor fasciae antebrachii m. (not pictured) Anconeus (red arrows) m. Lateral views of left TL The triceps mm. is essential to bearing weight on the forelimb, by keeping the humeroradioulnar joint extended. Cranial (Cr.) mm. of Brachium: Elbow Flexors Biceps brachii m.– acts on shoulder and elbow! Brachialis m. Lateral view of left TL Medial view of left TL Cranial (Cr.) mm. of Brachium: Biceps brachii m. – acts on shoulder and elbow! Transverse humeral retinaculum Biceps brachii & brachialis mm. flex the elbow joint together Origin of Biceps brachii m. Brachialis m. Biceps brachii m. Med. Lat. Common insertion Cranial view of right TL Transverse humeral retinaculum Cranio-medial view Synergistic/antagonistic mm. concept Muscles crossing the same side of a joint will work together (synergistic mm.) e.g. brachialis & biceps brachii Brachialis m. Biceps brachii m. Medial view of right TL Cr. Med. Lat. Cranial view of right TL Muscles crossing opposite sides of a joint will work against each other (antagonistic mm.) e.g. triceps brachii vs. biceps brachii Triceps (long head) Cd. Pronation vs supination of antebrachium More developed in cats Pronator teres & pronator quadratus mm. Supinator m. Med Med Lat. Cranial views of left TL Lat. Ext. carpi radialis m. reflected Carpus Joints of the canine manus All allow flexion & extension primarily, caused by 2 main muscle groups antagonistic to each other. acc Radiographs Manus (TVA) p 474 FIG. 16.10 (A to D) Dorsopalmar and lateral radiographic views of the canine (A and B) and feline (C and D) forepaws. (E) and (F) Oblique and dorsopalmar views of feline digits, respectively; note how the distal phalanges slide next to the middle phalanges when the claws are retracted. 1, Radius; 2, ulna; 3, intermedioradial carpal; 4, ulnar carpal; 5, accessory carpal; 6 and 6′, third and fourth metacarpals, respectively; 7, metacarpal pad; 7′, distal border of metacarpal pad, 8, digital pad; Med., medial. Carpus joint complex All carpal joints have collateral lig. R – radius, U – ulna, i-r – intermedioradial carpal bone, u – ulnar carpal bone, acc – accessory carpal bone, 2-4 – distal carpal bones, I-V – metacarpal bones Diagram of carpus joint a) b) c) 3 joints make-up the carpus: Antebrachiocarpal joint Middle carpal joint Carpometacarpal joint a) provides the greatest range of motions, has a separate synovial cavity/compartment b) + c) less motion, their synovial cavities communicate a) 1 U R u i-r b) 2 c) I 3 4 II III IV V acc Carpal joints: Clinical relevance: Greatest range of movement upon carpal flexion is seen in Antebrachiocarpal joint used here for arthrocenthesis https://www.cliniciansbrief.com/article/arthrocentesis-dogs (Possible pathology in distal radius) Carpal canal Boundaries: Dorsal border: palmar carpal ligament – opposes hyperextension of carpal joint Lateral border: accessory carpal bone Palmar border: flexor retinaculum Role: makes a tunnel for and protects the tendons of: Superficial digital flexor m. Deep digital flexor m. Flexor carpi radialis m. 2 1 Transverse cut through carpus 1 R U i-r 2 Palmar aspect of manus; (1) flexor retinaculum cut and reflected; (2) palmar carpal ligament acc Palmar aspect of carpus Craniolateral Muscles of the Antebrachium Extensors of the carpus and digits originate from the lateral supracondylar crest and lateral epicondyle of the humerus. Beginning on the cranial aspect of the antebrachium and moving laterally, a clue is ECLU: 1. Extensor carpi radialis 2. Common digital extensor 3. Lateral digital extensor 4. Ulnaris lateralis (the “traitor”) 1 2 1 2 4 34 23 Craniolateral views of left TL 3 Caudomedial Muscles of the Antebrachium Flexors of the carpus and digits originate mostly from the medial epicondyle of the humerus: 1. Flexor carpi ulnaris 2 heads (ulnar + humeral) 2. Superficial digital flexor (SFD) 3. Deep digital flexor (DDF) 3 heads (humeral, radial, ulnar) 4. Flexor carpi radialis 1 3 2 1 3 2 Caudal views of left TL Joints of the canine manus: digits Proximal sesamoids acc Metacarpophalangeal Proximal interphalangeal Distal interphalangeal Palmar aspect of digit skeleton Muscle(s) of the Digits Bifurcated insertion tendon attaches to the corresponding proximal sesamoid bones. Role: flexor, supports metacarpophalangeal joint Extensor branch fusing with common digital ext. tendon Flexor Manica “Sleeve” (red) of the SDF tendon that envelopes the DDF tendon, palmar to the metacarpophalangeal joint. Allows the tendons to cross. SDF DDF SDF DDF Medial palmar view of left TL Annular Ligaments of the Digits 1. Palmar annular ligament – holds down flexor manica and DDF tendon 2. Proximal digital annular ligament – holds down SDF & DDF tendons 3. Distal digital annular ligament – hold down DDF tendon. 1 SDF 2 3 Palmar view of left TL Dorsal ligament Attaches middle phalanx to distal phalanx. In cats, the dorsal (elastic) ligaments (3, 12) are important for claw retraction. Cat: Canine: A Cat: A: Claw - the dorsal elastic ligament passively maintains the extended rest position of the distal interphalangeal joint B: Claw drawn for action - contraction of the deep digital flexor (6) protracts the claw Pads of the Manus: - carpal pad - metacarpal pad - digital pads Case study of muscle pathology (optional): History: Female pointer is presented to you because of visible right TL lameness that appeared after a hunting trip, a few weeks ago, and hasn’t subsided. The dog has a minimal physical exercise regimen. No bone or join issues are detected during the examination. Observing gait: https://www.youtube.com/watch?v=I9xEKR8JwXw Is this dog’s gait abnormal? Why? KEY on next slide Is this dog’s gait abnormal? YES Why? The brachium is abnormally rotated laterally and abducted at all times, compared with left limb. Watch again how the “arm” “sticks out to the side” when the patient walks. Clinical examination: https://www.youtube.com/watch?v=k5NRDDR3WQw What is abnormal? KEY on next slide What is abnormal? On affected side, the shoulder joint presents limited mobility: humerus (and distal limb) cannot be medially rotated in relation to the scapula. Watch again how the DVM tests both sides and note the differences! There is significant atrophy of the muscles on the lateral side of the right scapula; indicating lack of full use. So, what is happening here? Reasoning 1. We know the bones and joints are normal 2. The affected muscle is: Located on the lateral aspect of the scapula Keeping the humerus (arm) laterally rotated and abducted, at the shoulder joint Which muscle best corresponds functionally and topographically to this description? Diagnosis: contracture (“shortening”) of the infraspinatus m. Probable cause: due to lack of training and of proper warm up, the muscle suffered tears that induced scar tissue to form, shortening its length and permanently impairing the mobility of the shoulder joint as a result. Practice photos Scapula Cr. Lat. view Cd. Cd. Cr. Med. view Scapula Cr. Cd. Med.-vtr. view Cr. Cd. Vtr. view Humerus Cr. Lat. view Cd. Cd. Cr. Med. view Humerus Cr. Cd. Cr. Cd. Cd. Med. view Lat. view Caudo-Lat. view Cr. Lat. Radius & Ulna Cd. view Cr. view Med. Cr. Med. Med. Cd. Lat. Lat. Lat. Cr. view Cd. Cd. view Med. view Med. Lat. view Cr. Radius & Ulna Cr. view Cr. Cd. Lat. Med. Lat. Med. Cr. view Med. view Manus bones Med. Lat. Lat. Ds. Dorsal view Lat. view Med. Palm. Palmar view Med. Ds. Palm. Lat. Lat. Med. Med. Lat. view Cd./Palmar view Dorsal view Lat. Cr./Ds. view Lateral view Cd Plastinated piece Cr Cr Medial view Cd Prosection pictures Rump Dorsal Head Ventral Dorsal Hindlimb Ventral Ventral side of mandible Ventral Head (Cranial) Cd. Cr. Lat. view Cr. Cd. Med. view Cr. Lat. view Cd. Cr. Lat. view Cd. Left to right: Lateral view progressing to cranial view Cd. Cr. Palm. Ds. Lat. Lat. Lat. Med. Med. Lat. Med. Med. Cd. view Med. Lat. Cr. Med. Cd. view Cr. Cd. Ds. Palm. Cd. Lat. Med. view Med. view Palm. Lat. Ds. Med. Med. Palm. view Palm.-Med. view Lat. Ds.-Lat. view Cranio-medial view of the proximal forelimb Lateral Medial Medial view of the shoulder joint