Approach to Equine Lameness Investigation PDF

APPROACH TO EQUINE LAMENESS I N V E S T I G AT I O N ALISON PRUTTON BVSC SFHEA MRCVS LEARNING OBJECTIVES ❖Understand how to approach a lame horse ❖Describe a lameness evaluation in the horse ❖Understand the use of and describe nerve and joint blocks in the horse...

APPROACH TO EQUINE LAMENESS I N V E S T I G AT I O N ALISON PRUTTON BVSC SFHEA MRCVS LEARNING OBJECTIVES ❖Understand how to approach a lame horse ❖Describe a lameness evaluation in the horse ❖Understand the use of and describe nerve and joint blocks in the horse 2 HISTORY Signalment Use, and level of competition The perceived problem Onset, duration, progression Previous history? Trauma? Any medication Change in management? Farriery? Effect of exercise or surface? https://cdn.britannica.com/87/162987-050-8E836792/Camelot-Joseph-OBrien-French- Fifteen-charges-Two-1970.jpg 3 C L I N I C A L E X A M I N AT I O N Observation Obvious clinical signs Posture “Faulty conformation is not an unsoundness… Conformation it is a warning sign” Symmetry Palpation Heat Pain Swelling Effusion Range of motion, pain on flexion https://www.deviantart.com/dawn- photography5/art/Chestnut-Horse-Shot-from-Behind- 650411259 Hoof tester examination 4 G A I T E VA LUAT I O N 1. Walk in a straight line (away and back) 2. Trot in a straight line (away and back) 3. Lunge in walk and trot (+/- canter) in a circle in both directions Is the lameness increased with lame leg on inside or outside of circle? 4. (Lunge on soft and hard surfaces?) Hard: Bone injuries worse? Foot lameness? Soft: Soft tissue injuries worse? Is the horse lame? 5. Flexion tests 6. +/- Ridden assessment Which leg(s)? What grade? 5 IDENTIFYING LAMENESS At the walk 6 IDENTIFYING LAMENESS At the trot Forelimb Head nod (lifts head when lame limb weight bearing) “Down on the sound” (limb) Hindlimb Asymmetric movement of pelvis Often described as ‘hip hike’ or ‘hip drop’ Increased movement of pelvis (up and down) on lame side Shortened stride length/shortened cranial phase of the stride Fetlock drop Bilateral If both limbs equally affected, stride length may just appear short or choppy Pfau et al 2015 7 IDENTIFYING LAMENESS Lunging Hard versus soft ground Flexion: Forelimbs: Carpal flexion, or distal limb only (fetlock, pastern coffin) Hindlimb: Distal limb only, or full limb Normal for lameness to look slightly worse for a few strides If longer lasting or severe deterioration, this is considered positive Indicates pain associated with the joints/structures surrounding the joints Not specific Ridden assessment? 8 9 10 11 REFERRED LAMENESS Severe hind limb lameness can mimic ipsilateral forelimb lameness in trot. Lame hind leg hits the ground: Horse shifts its weight forward to transfer load away from lame limb Contralateral forelimb bears weight simultaneously with the lame hind limb Head nod coincides Thus mimicking lameness in the forelimb ipsilateral to the lame hindlimb. *Diagnostic analgesia required to confirm suspected referred lameness. 12 13 GRADING LAMENESS European Lameness Grading Scale (0-10) 0 Sound 1-3 Mild 4-6 Moderate 7-10 Severe 14  GRADING LAMENESS AAEP Lameness Grading Scale (0-5) Alternative 5-point lameness scoring system (lameness assessed at trot) 0 Sound 0 Sound Difficult to observe and not 1 consistently apparent regardless of Mild lameness when trotted in a straight line. When lame forelimb strikes, a circumstances 1 subtle head nod is observed; when lame hindlimb strikes, a subtle pelvic hike occurs. Head nod and pelvic hike may be inconsistent. Difficult to observe at a walk or trotting Obvious lameness. Head nod and pelvic hike are seen consistently, 2 in a straight line but consistently 2 excursion is several centimetres. apparent under certain circumstances Pronounced head nod and pelvic hike of several centimetres. With Consistently observable at a trot under 3 unilateral hindlimb lameness, head and neck nod is seen when the diagonal 3 all circumstances forelimb strikes the ground (mimicking ipsilateral forelimb lameness). Obvious lameness with marked head Severe lameness with extreme head nod and pelvic hike. Can still be 4 4 nod, hip hike or shortened stride trotted. Minimal weightbearing in motion or at Does not bear weight. If trotted, carries the limb. (Horses that are non- 5 5 weight bearing at the walk or while standing should not be trotted). rest and inability to move 15 INERTIAL MEASUREMENT UNITS Measure head and pelvic vertical displacements to quantify the extent of lameness Increasingly used in practice, but do not replace the expert examiner https://equinosis.com/veterinarians/ 16 1. R I G H T R E I N , S O F T S U R FAC E 17 2. L E F T R E I N , S O F T S U R FAC E 18 P R I N C I P L E S O F A L A M E N E S S I N V E S T I G AT I O N Consistent Diagnostic Diagnostic lameness analgesia Imaging Diagnosis Treatment 19 DIAGNOSTIC ANALGESIA Encompasses perineural analgesia and intra-synovial analgesia Local anaesthetic inhibits nociceptive nerve conduction If injected perineurally; desensitizes structures distal to block Ideally begin investigation distally and work proximally Identify region that is the source of the pain > guide imaging Anatomy knowledge essential! (Review!) Local Anaesthetic Onset Duration Comments Lidocaine Fast onset 30-45 minutes Can be irritant to skin Mepivicaine Fast onset 1.5-2 hours Least irritant Bupivicaine Slower onset 4-6 hours Not useful for DA, used therapeutically for pain relief 20 INTERPRETING DIAGNOSTIC ANALGESIA Check if block has worked Skin sensation – pen Assess whether block is positive or negative (Repeat gait evaluation) Positive: ≥50% improvement in lameness Partial: 50-75% Negative: < 50% improvement in lameness Switching legs? > Indicates bilateral lameness Specific duration of time recommended for re-examination following block Generally ~10 minutes (depends on block) Too short: block won’t have had enough time to work Too long: diffusion of local anaesthetic will make block less specific In some cases, pain may then be further localised: Allow block to wear off Local anaesthetic injected into synovial structures within the localised area 21 P R E PA R AT I O N F O R D I A G N O S T I C A N A LG E S I A Perineural analgesia = Clean Restraint & operator safety May clip hair if coat long Capable handler Hard hat Clean with antiseptic soaked swabs Bribery? Rinse with alcohol Twitch? Clean technique Stocks? Short acting sedation? Xylazine Intra-synovial analgesia = sterile Clipping recommended Sterile preparation Scrub with antiseptic for at least 5 minutes Rinse with alcohol Sterile gloves and aseptic technique 22 C O M P L I C AT I O N S A N D C O N T R A I N D I C AT I O N S Complications: Soft tissue swelling Haematoma/bruising Infection Skin Joint or other synovial structure (*emergency*) Synovitis (aseptic flare) Cardiovascular effects if intravascular injection of LA? Contraindications: Suspected fracture Skin infection/dermatitis of injection site Moderate – severe soft tissue injury (Typically signs are obvious enough that DA is not warranted) 23 PERINEURAL ANALGESIA Forelimb perineural analgesia Hindlimb perineural analgesia Palmar digital nerve block Plantar digital nerve block Pastern ring block Pastern ring block Abaxial sesamoid nerve block Abaxial sesamoid nerve block Low 4 point nerve block Low 6 point nerve block High 4 point nerve block High 6 point nerve block Variations: Subcarpal or lateral palmar nerve block Variations: Subtarsal nerve block or deep branch of the lateral plantar nerve Median/Ulner nerve block Tibial/Peroneal nerve block 24  INTRA-SYNOVIAL DIAGNOSTIC ANALGESIA Distal limb (forelimb and hindlimb) Distal interphalangeal joint (DIPJ) Navicular bursa Proximal interphalangeal joint (PIPJ) Metacarpophalangeal (MCPJ)/Metatarsophalangeal (MCTJ) joint Digital flexor tendon sheath Upper forelimb Upper hindlimb Carpus: Middle carpal and radiocarpal joints Tarsus: Tarsometatarsal (TMTJ), distal intertarsal (DITJ) and Carpal sheath tarsocrural (TCJ) joints Elbow Tarsal sheath Bicipital bursa Stifle: Medial and lateral femorotibial joints and femoropatellar joint Scapulohumeral joint Coxofemoral Sacroiliac region 25 PA L M A R / P L A N TA R D I G I TA L N E R V E B LO C K Site: Just proximal to collateral cartilage, abaxial to edge of tendon, medial and lateral aspects Technique: limb non-weight bearing, palpate neurovascular bundle, place needle subcutaneously, directed distally Vein Artery Nerve (from abaxial to axial) Care: Ensure not too axial - need to avoid Deep digital flexor tendon (DDFT) & Digital flexor tendon sheath (DFTS) in palmar pastern region Needle: 25 gauge, 5/8” Volume: 1.5-2 ml medially and laterally Recheck: 10 minutes Test block: Skin sensation of heel region 26 PA L M A R / P L A N TA R D I G I TA L N E R V E B LO C K Nerves blocked: medial and lateral palmar/plantar nerves Structures desensitised: Palmar/plantar ~two thirds of foot Navicular apparatus Soft tissues of the heel Digital portion of DDFT DIP joint Entire sole +/- PIP joint depending on diffusion and volume of LA Moyer, 2011 27 ABAXIAL SESAMOID NERVE BLOCK Site: immediately palmar to neurovascular bundle at abaxial surface of proximal sesamoid bones, medial and lateral aspects Technique: limb non-weight bearing, palpate neurovascular bundle, insert needle subcutaneously and parallel to bundle, directed distally Vein Artery Nerve (from abaxial to axial) Needle: 25 gauge 5/8” Volume: 1.5-2ml medially and laterally Recheck:10 minutes Test block: skin sensation dorsal pastern 28 ABAXIAL SESAMOID NERVE BLOCK Nerves blocked: medial and lateral palmar/plantar nerves (+ dorsal branches) Structures desensitised are as for PDNB, plus: Entire Foot Middle Phalanx Proximal Phalanx- distopalmar aspects PIPJ Soft tissue distal to fetlock Distal deep digital flexor tendon Distal Superficial digital flexor tendon Distal sesamoidean ligaments Collateral ligaments of DIP joint and PIP joint May partially desensitise fetlock joint if placed too high Moyer, 2011 29 LOW 4-POINT NERVE BLOCK Sites: Palmar metacarpal nerves: just distal to button of the splint bone Palmar nerves: between suspensory ligament and DDFT, 3-5 cm proximal to button of splint (Medial and lateral aspects) Technique: weightbearing or non-weight bearing, palpate landmarks (nerve not palpable), needle placed subcutaneously Care: Can be close to proximal pouch of DFTS so consider sterile prep/take care with positioning Needle : 25 gauge 5/8” x 4 Volume: 1.5-2ml for each nerve Test block: skin sensation of digit and fetlock joint HL: additional 2 sites dorsally (not always included) 30 LOW 4-POINT NERVE BLOCK Nerves blocked: Medial and lateral palmar/plantar nerves and palmar/plantar metacarpal/metatarsal nerves Structures desensitised: Fetlock joint Proximal sesamoid bones Distal medial and lateral branches of suspensory ligament Flexor tendons distal to block Digital Flexor Tendon Sheath Entire distal limb Moyer, 2011 31 D I S TA L L I M B P E R I N E U R A L A N A LG E S I A S U M M A R Y Low 4 Point Nerve Block Abaxial Sesamoid Nerve Block Palmar digital Nerve Block (Barker, 2016) 32 D I S TA L I N T E R P H A L A N G E A L ( C O F F I N ) J O I N T B LO C K Several approaches described (Dorsal parallel approach described here) Technique: limb weight-bearing, on dorsal midline, insert needle immediately proximal to coronary band, parallel to the weightbearing surface Needle: 20 gauge 1” Volume: 5ml Structures desensitised DIP joint ~Collateral Ligaments if the DIP joint Navicular Bone/Bursa Toe region of the sole Diffusion of local anaesthetic between DIP joint and navicular bursa after 15 minutes Re-examine after 5 and 20 minutes May also desensitise palmar digital nerves(!) 33 NAVICULAR BURSA BLOCK Radiography to confirm needle positioned correctly Spinal needle 34 MCP/MTP (FETLOCK) JOINT BLOCK Several approaches described: *Dorsal approach *Palmar/Plantar Pouch *Collateral sesamoidean ligament approach 35 FETLOCK JOINT BLOCK: C O L L AT E R A L S E S A M O I D E A N L I G A M E N T APPROACH Site: Anatomical boundaries: Proximal palmar process of P1 Dorsal aspect of the proximal sesamoid bone Palmar condyle of MCIII Technique: Needle is inserted into the depression just proximal to the palmar process of P1 and through the lateral collateral sesamoidean ligament. Needle inserted parallel to the ground in a dorsomedial direction until fluid is obtained Needle: 20 gauge 1” Volume: 10 ml local anaesthetic 36 TA R S O M E TA R S A L ( T M T ) J O I N T B LO C K Commonly performed in practice Diagnosis of OA of the small tarsal joints (‘Bone Spavin’) Communication with DITJ in some (some clinicians do also block the DITJ) 37 D I G I TA L F L E XO R T E N D O N S H E AT H B LO C K Different approaches described: Proximal pouch Palmar axial sesamoidean approach Basilar approach Distal pouch (Barker, 2016) 38 D E E P B R A N C H O F T H E L AT E R A L P L A N TA R N E R V E Lateral approach Needle inserted between lateral splint bone and lateral border of superficial digital flexor tendon 23G 25mm needle, inserted to the hub, 15mm distal to the head of the lateral splint bone. 3ml For diagnosis of proximal suspensory ligament desmitis Test: No resentment to firm digital palpation of the suspensory ligament. (Barker, 2016) Moyer, 2011 39 STIFLE Diffusion of local between the 3 joint compartments (medial femorotibial, lateral femorotibial and femoropatellar) is variable: All 3 should be blocked Image = Femoropatellar injection 40 USEFUL RESOURCES AND FURTHER READING Barker, W. (2016). Equine distal limb diagnostic anaesthesia: (1) Basic principles and perineural techniques. In Practice, 38(2), pp.82-90. Barker, W. (2016). Equine distal limb diagnostic anaesthesia: (2) Intrasynovial anaesthesia. In Practice, 38(3), pp.123-129. Moyer, W., Schumacher, J. and Schumacher, J. (2011). Equine joint injection and regional anesthesia. Chadds Ford, PA: Academic Veterinary Solutions, LLC. Dyson, S. and Ross, M. (2011). Diagnosis and management of lameness in the horse. St. Louis, Mo.: Elsevier/Saunders. RVC Equine Distal Limb Anatomy and Imaging https://www.rvc.ac.uk/static/review/equine-distal-limb/index.html Equine Lameness Trainer https://www.lamenesstrainer.com/ 44