Equine Lameness Examination 1 & 2 2017 PDF

Musculoskeletal System Equine Lameness Exam 1 Chris Byron, DVM, MS, DACVS Associate Professor Large Animal Surgery Goals of a Lameness Exam Is the horse lame? Which limbs are involved? What is site / sites causing the problem? What is the specific cause of the problem? What is the most appropriate t...

Musculoskeletal System Equine Lameness Exam 1 Chris Byron, DVM, MS, DACVS Associate Professor Large Animal Surgery Goals of a Lameness Exam Is the horse lame? Which limbs are involved? What is site / sites causing the problem? What is the specific cause of the problem? What is the most appropriate treatment? What is the prognosis for recovery? Components History Thorough physical exam Baseline motion exam – Establish lameness grade Manipulations – Hoof testers – Flexions – Diagnostic analgesia Diagnostic Imaging History Signalment Acute vs. insidious onset – Duration Use of the animal – Race horse vs. lawnmower Management – Shoeing intervals – Exercise routines Physical Exam Visual Exam – Obvious asymmetries? – Obvious swellings? Effusion vs. edema – Wounds – Conformation Conformation Evaluation: Limbs Standing square Firm, level ground Reposition if conformational abnormality is noted Plumb line concept Dynamic evaluation R&D Figure 4-10 Physical Exam Physical Exam Palpate each individual structure – Joints – effusion, heat – Tendons / ligaments – thickening, sensitivity Many changes can be subtle Be systematic! Palpation Adams 5th edn. Palpation Fetlock Joint Adams 3.30-3.31 Digital Sheath Palpation Examples of severe femoropatellar and tibiotarsal joint effusion Palpating Tendons & Ligaments Superficial Digital Flexor Tendon Deep Digital Flexor Tendon Suspensory Ligament (origin, body, medial & lateral branches) Hoof Testers Many lameness issues involve the foot Be thorough – Multiple sites – Repeatability – Usually check all 4 feet Motion Exam Straight-line – Establish lameness grade – Horse going away & towards you Should also watch horse go past you (from side) – Performed at trot Circles On a lunge line or in-hand Performed at trot Accentuates weight bearing of inside limbs What Can We Watch For? Forelimbs Head bob – “down on the sound”** Arc of flight of foot Altered flight path of foot Length of stride Angles of joint flexion Audible differences between limbs Hindlimbs Pelvic hike or drop – up/ down on the lame limb Arc of flight of foot Altered flight path of foot Length of stride Angles of joint flexion Drifting away from lame limb Lameness Grades: AAEP Scale Grade 1 - difficult to observe, inconsistent Grade 2 - difficult to observe at walk/trot going straight; consistent in circle, incline, hard surface Grade 3 - consistently observable at trot Grade 4 - obvious at walk; marked nodding/hitching/short stride Grade 5 - minimal weight bearing, inability to move Fetlock Drop Alterations in Cranial/Caudal Phases Adams 3.1 Other Considerations Weight Distribution: Natural Forelimb: 60% Hindlimb: 40% R&D Figure 2-1 Weight Distribution: Rider Forelimb: 70% Hindlimb: 30% R&D Figure 2-2 The Natural Gaits: The Walk 4-beat gait LH LF RH RF www.wikipedia.org The Natural Gaits: The Trot 2-beat diagonal gait RF + LH LF + RH www.wikipedia.org Forelimb Lameness Head drops when sound limb is weight bearing “Down on Sound” Recognizing Hindlimb Lameness – The lame limb will exhibit greater gluteal excursion (distance from highest to lowest point) – Increased pelvic hike and drop in lame limb Hindlimb Lameness Flexion Tests: What are they, how do they work? Not sensitive or specific (false positives and negatives possible) Not a replacement for diagnostic analgesia Be aware of all structures being stressed Control: direction, force, duration of the stress Flexion Tests Sources of pain: Tension on soft tissues (extension side) Compression on soft tissues (flexion side) Compression of articular surface (SC bone) ↑ Intra-articular pressure Vascular constriction Stretching of nerves Adams 3.33 Manipulations - Flexion Tests Ross and Dyson 2003 Digit Adams 3.34 Digit Flexion Carpus Adams 3.44 Hind Limb Digit Flexion Test R&D 8-7 Reciprocal mechanism/apparatus! Hock/Stifle Manipulation Test R&D 8-8 Other Manipulation Tests Adams 3.75 Lameness Exam 2 Chris Byron, DVM, MS, DACVS Associate Professor Large Animal Surgery Purpose of Exam Localize – Palpation – Motion – Diagnostic analgesia Identify – Imaging Treat Prognosis Purpose of Exam Is the horse lame? – Owner’s history / referral information – Baseline motion exam Which leg(s) are abnormal? – Motion exam – Flexions Where in the limb is the source of pain? – Diagnostic analgesia Golden Rule Ideally Block Out All Lameness Start Distally and Work Proximally The most thorough way May be time consuming! When to break the rule: – Targeted intra-synovial anesthesia (based on effusion, pain, etc.) – Difficult horses Local Anesthesia: Advantages The gold standard for localizing pain to a region in the horse Immediate results Inexpensive Educational for the owner Flexible technique Local Anesthesia Considerations* Diagnostic imaging FIRST if: – Severe lameness AAEP grade 4/5 or 5/5 – Suspect stress fracture/incomplete fractures Onset and Duration Lidocaine: – Rapid onset – 1.5-3 hour duration Mepivacaine* – Rapid onset – 2-3 hour duration Bupivacaine – Intermediate onset – 3-6 hour duration Degree and duration of effect decreased in severely lame horses Diagnostic vs. therapeutic local anesthesia Influence of tissue pH Judging Improvement Usually expressed as a % improvement over baseline: this is VERY SUBJECTIVE Make use of manipulation tests, circles Aim for 100% improvement; baseline lameness may switch to the other side Should achieve ≥ 70% improvement – Lesser improvements require further blockade – Serial improvements difficult to judge What May Not Block Out Severe lameness Some articular lesions (subchondral bone) – Perineural blockade is more consistent than intraarticular blocks for subchondral bone pain Deep bone pain Laminitis Mechanical gait abnormalities Patient Preparation Perineural: – Clean – PI/alcohol scrub protocol: usually brief; be thorough near synovial structures – Never touch the shaft or end of the needle Use the HUB only Intrasynovial: – Clipping? ASK THE OWNER FIRST! – 5 minute sterile preparation – Wear sterile gloves Avoid areas of damaged skin/ dermatitis X OK X Choice of Needle & Syringe Restraint Use physical restraint ONLY (if possible) Chemical restraint: – α2-agonists and opiates are analgesic; may also cause ataxia – Avoid with subtle lameness – Useful in fractious horses with moderate-severe hind limb lameness that require blockade – May allow sedation to wear off or reverse prior to evaluation Residual gait abnormality may remain Perineural Analgesia: Forelimb Palmar Digital Nerve Block Palmar / Plantar digital nerves 1cm proximal to collateral cartilages 1.5-2mL Wait 5-7 minutes Palmar Digital Nerve Block Structures blocked: – Sole – Digital cushion – Navicular bone – Navicular bursa – Navicular suspensory apparatus – Insertion of DDFT on P3 Palmar Digital Medial and lateral nerves Blocks 70-80% of foot and DIP joint; may diffuse proximal Direct needle distal Palmar Digital Block: Common Lameness Navicular disease / syndrome P3 wing fractures Solar injuries – Bruises, abscesses, penetrations Abaxial/BasiSesamoid Block Palmar / Plantar nerves Mid-body/base of the proximal sesamoid bones 1.5-2mL Adams 3.92; R&D 10-5 Wait 5-7 minutes Abaxial Sesamoid Block Structures blocked: – Dorsal hoof wall – Coronary band – Coffin joint – Pastern joint – Sesamoidean ligaments Basisesamoid/ Abaxial Sesamoid Palmar Digital nerves blocked proximal to dorsal branching MCP joint blockade possible Abaxial Sesamoid Block: Common Lameness Laminitis* Low ringbone – OA of coffin joint High ringbone – OA of pastern joint Low Palmar/ Low 4-Point Medial and lateral palmar nerves: (subcutaneous) – Flexor tendons (palmar) – Suspensory ligament (dorsal) Medial and lateral palmar metacarpal nerves: (deep/axial) – Button of splint (proximal) – MCIII (dorsal) – May add dorsal ring block via same needle site Caution! – Fetlock joint – Digital flexor tendon sheath Low 4-Point Block Additional structures blocked: – Fetlock joint – Sesamoid bones – Insertion of suspensory ligament on the sesamoid bones Low 4-point: Common Lameness Fetlock OA Sesamoid bone fractures* Desmitis of branches of suspensory ligament High Palmar/ High 4-Point Medial and lateral palmar and palmar metacarpal nerves Structures desensitized may be variable High 4-Point Block Additional structures blocked: – Cannon bone – Splint bones – Suspensory ligament High 4-point: Common Lameness Suspensory origin desmitis Splint bone exostosis Dorsal cortical fractures of cannon bone Wheat Block Alternative to high 4-point Blocks the lateral palmar nerve Intended to block the suspensory ligament Perineural Analgesia: Hindlimb Hindlimb: Common Lameness Osteoarthritis: – Distal intertarsal joint – Tarsometatarsal joint What block? Hindlimb Distal Perineural Blocks Palmar digital, abaxial sesamoid identical to forelimb Action of the reciprocal apparatus makes flexed blocks more difficult Low 6-Point Similar to the low 4 Don’t forget the dorsal metatarsal nerves Blocking pattern is similar to the low 4 High Plantar Medial and lateral plantar and plantar metatarsal nerves Dorsal ring block may be added to abolish dorsal MTIII pain Perform with limb off ground; 18 g needle 2 injection sites 5-10 ml per site Most used to dx. PSD May block TMT joint or tarsal canal inadvertently References