Diseases of equine foot_lecture_1-HH copy.pdf

DISEASES OF THE EQUINE FOOT 1 Henre Honnas, DVM Large Animal Surgery, Resident III Outline Lecture 1 Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries – heel bulb lacerations Keratomas Canker Lecture 2 (2...

DISEASES OF THE EQUINE FOOT 1 Henre Honnas, DVM Large Animal Surgery, Resident III Outline Lecture 1 Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries – heel bulb lacerations Keratomas Canker Lecture 2 (2/12/24) Disorders of the hoof capsule – cont’d Subsolar abscess Pedal osteitis Traumatic injuries – penetrating wounds to the hoof Navicular disease Fractures within the hoof Disorders of the collateral cartilages Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Anatomy of the foot Bones * Distal phalanx (P3) * Middle phalanx (P2) * Proximal phalanx (P1) * Distal sesamoid bone (navicular bone) Synovial structures Distal interphalangeal (coffin) joint Proximal interphalangeal (pastern) joint Metacarpophalangeal (fetlock) joint Digital flexor tendon sheath Navicular bursa Tendon and ligaments # Deep digital flexor tendon (DDFT) Sesamoidean ligaments # Impar ligament * * * #* # Ashdown, Atlas of Veterinary Anatomy The equine hoof The equine hoof Anatomy of the hoof Limbic (perioplic) Epidermis Coronary Parietal Heels Dermis (corium) Sole Denoix, The Equine Distal Limb Anatomy of the hoof - Epidermis Stratum Externum (P) Glossy waterproofing film Stratum Medium (SM) Tubular and intertubular horn Stratum Internum (SI) Primary epidermal lamellae (PEL) 550 – 600 vertically arranged Secondary epidermal lamellae (SEL) From each PEL 150 – 200 Gerad, Anatomy and Physiology of the Equine Foot Anatomy of the hoof - Dermis Perioplic, coronary, sole, and heel Dermal papilla Various shape and size Parietal region Primary dermal lamellae (PDL) 550 - 600 Secondary dermal lamellae (SDL) Connecting PEL/SEL to PDL/SDL Critical connection between hoof wall and P3 Gerad, Anatomy and Physiology of the Equine Foot Anatomy of the hoof - Dermis Gerad, Anatomy and Physiology of the Equine Foot Anatomy of the hoof – Vasculature Digital arteries (medial and lateral) Extensive microvascular network Dermal lamellae Interconnecting arteriovenous anastomoses (AVAs) Dermal vasculature supply epidermis Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratomas Canker Examination Methodological approach Inspection Conformation Symmetry Defects, cracks, bruises, bumps Palpation Hoof testers Diagnostic analgesia Diagnostic imaging Examination – Conformation Shape Distal Limb Hoof Examination – Conformation Balance Dorsopalmar/plantar Hoof – pastern axis Mediolateral Types of balance Static (geometric) Dynamic (functional) Radiographic guidance Ross and Dyson, Lameness in the Horse Conformation – Dorsopalmar/plantar balance Broken back HPA Broken forward HPA Conformation – Mediolateral balance Examination – Hoof testers Mandatory Systematic approach Test across toe, frog, medial and lateral heel, across both heels Comparison Contralateral hoof Repeat test Diagnostic analgesia Nerve blocks Palmar/plantar digital nerve block Pastern semi ring block Abaxial sesamoid block Intra-synovial anesthesia Distal interphalangeal joint Navicular bursa Ross and Dyson, Lameness in the Horse Diagnostic imaging Digital Radiology Ultrasonography Nuclear imaging Scintigraphy PET Computed Tomography Magnetic Resonance Imaging Gallastegui, Imaging of the Equine Foot Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Laminitis - Definitions Inflammation/compromise of the laminae of the hoof wall Lamellar degeneration and necrosis of P3 suspensory apparatus Founder Layman term for chronic laminitis Displacement of P3 Prevalence: Wylie et al. 2011: 1.5 – 34 % Wylie et al. 2014: 1 of 200 veterinary visits Laminitis – Etiology Complex and multifactorial Secondary response to primary triggers Classification 1) Endocrinopathic disorders 2) Systemic inflammatory disorders 3) Excessive mechanical overload or trauma Support limb laminitis Trauma (”Road founder”) Laminitis – Pathophysiology Not fully elucidated Theories Digital hemodynamic events Enzymatic events Inflammatory events Endocrinopathic events Mechanical/traumatic events Outcome → displacement of P3 Laminitis - Pathophysiology Major forces acting on P3 (1) Bony column (weightbearing) Downward load (2) Distal phalangeal support Sole and frog support (3) Deep digital flexor tendon (DDFT) Proximo-palmar force (4) Lamellar attachment Between P3 and hoof wall (5) Common digital extensor tendon Pulling force Morrison, Mechanical Principal of the Equine Foot Laminitis – Endocrinopathic disorders Equine Metabolic Disease Insulin dysregulation or resistance Pituitary Pars Intermedia Dysfunction (PPID, Cushing) Hormone imbalance - ↑ACTH, cortisone, and insulin Pathophysiology - Insulin-mediated laminitis Proliferation and stretching of lamellar cells Loss of lamellar integrity Minimal inflammation +/- alterations in local blood flow and metabolism Laminitis – Systemic inflammatory disorders Sepsis/SIRS/MODS/Endotoxemia Gastrointestinal disease (colitis) Pneumonia Metritis – Retained placenta Grain overload Black walnut ingestion Exogeneous steroids (?) Laminitis – Systemic inflammatory disorders Sepsis/SIRS/MODS/Endotoxemia Gastrointestinal disease (colitis) Pneumonia Metritis – Retained placenta Grain overload Black walnut ingestion Exogeneous steroids (?) Laminitis – Support limb laminitis Altered weight bearing due to pain/dysfunction ↓ Perfusion Ischemia Disruption of lamellar adhesions and loss of lamellar structural integrity Ischemia – unique, key mechanical event Once clinical – lesions usually well advanced Lesions not confined to contralateral limb Laminitis – Clinical signs Clinical signs – Acute laminitis Acute onset lameness (one or more feet) Variable severity (Obel grade) Shifting weight Short, stabbing stride Unwilling to move Forelimbs > hindlimbs Bounding digital pulses Feet hyperthermic Pain to hoof testers in toe region Depression at coronary band Tachycardia, anxiety, sweating, tremors Clinical signs – Chronic laminitis +/-Lameness Heel-to-toe placement Distorted hoof shape and growth Diverging growth lines Broad white line +/- sensitive to hoof testers Recurrent, acute episodes Acute lameness Digital pulses Rotation of P3 Laminitis Laminitis – Diagnosis History and clinical signs Diagnostic analgesia Abaxial sesamoid Radiographic evaluation Venographic evaluation Differential diagnosis Colic Rhabdomyolysis Pleuritis Tetanus Laminitis – Radiographic evaluation Standard technique Latero-medial/dorsopalmar(plantar) Block/Radiopaque marker Routine measurements Coronary band to extensor process distance (CE) Sole depth (SD) Horn:Lamellar distance (HL) Palmar/plantar angle (PA) Serial monitoring Orsini, Equine Emergencies Laminitis – Radiographic evaluation Day 0 (initial signs) Day 3 (initial signs) Laminitis – Venograms Radiopaque contrast injected into the palmar digital vein Aid diagnosis Detail change within foot early Venous compression causes filling defects of contrast material Aid response to treatment Morrison, Mechanical Principal of the Equine Foot Laminitis – Treatment Principles 1) Remove initiating cause(s) 2) Control inflammation and pain Systemic Local (lamellar) 3) Prevent further lamellar damage Laminitis – Endocrinopathic disorders Identify EMS or PPID Treatment options Thyroxine and metformin Improve insulin sensitivity Exercise Contraindicated if current/recent flare up Diet Improve insulin sensitivity Promote weight loss Treat PPID Prascend® (Pergolide) Laminitis – Systemic disease **PREVENTION ** Address specific disease Control of pain and inflammation Grain overload – lavage stomach Non-steroidal (NSAIDs) Flunixin meglumine, phenylbutazone GI strangulation – surgical correction and resection of ischemic bowel Antibiotics if known bacterial infection Potomac Horse Fever – Oxytetracycline Maintain normal cardiovascular function Fluid resuscitation Polymyxin B Pentoxifylline DMSO Antithrombotic (clopidogrel, aspirin, and heparin) Continuous rate infusions Lidocaine Ketamine Laminitis – Cryotherapy Standard of care Prevention and treatment Hypothermia Vasoconstriction Analgesia Anti-inflammatory effect Hypometabolism Maintain < 10oC 24 – 48 hrs after resolution thehorse.com Laminitis – Mechanical treatment Prevention of further lamellar damage Limit exercise/deep bedding Emergency mechanical treatment Neutralize forces on digit Reestablish vascular perfusion Basis principles Palmar/plantar wedge (20o) Solar support Shorten toe (eases breakover) Foot cast (?) Morrison, Mechanical Principal of the Equine Foot Laminitis – Surgical management Deep Digital Flexor Tenotomy Indications Clinically unresponsive acute case Chronic refractory laminitis Goal → change hoof growth pattern Reduce DDFT effect on dorsal lamellar perfusion Decompress sensitive solar lamellar Post-tenotomy shoeing/trimming essential! Morrison, Mechanical Principal of the Equine Foot Laminitis – Prognosis Determining factors Severity of lamellar lesions Underlying disease Guarded – poor ”Fatal sinker syndrome” P3 infection and rotation Rapid progression of disease Prevention important Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Thrush Infection of the frog If deeper tissue layers (pododermatitis) Etiology – poor hygiene Manure and urine accumulation Conformation Clinical signs Moist sulci, foul odor Black, thick discharge +/- lameness Thrush – Treatment Debridement of frog Removal of damaged horn ↓colonization of bacteria and fungi Meticulous hoof care Good stall hygiene Local topical medication Numerous products Protection of exposed sensitive laminae Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker White line disease – “Seedy toe” Colonization of bacteria and fungi in the white line Predisposing factor Poor-quality horn Poor hoof and stall hygiene Deterioration of the white line → Loss of attachment between the wall and sole → Inflammation in sensitive laminae → Lameness White line disease – Treatment Two main components Debridement of necrotic horn Meticulous stall hygiene +/- Hoof wall resection Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Hoof wall cracks Longitudinal disruption of the hoof wall Horizontal = hoof crevice Classification Toe/quarter/heel Distal/Proximal/Complete Superficial/perforating Clinical signs +/- sensitivity to hoof testers If perforating → Lameness Hoof wall cracks – Treatment Remove inciting cause Improve horn quality Good quality trimming and shoeing Minor hoof cracks Appropriate trimming Horizontal groove proximal +/- bar shoe Hoof wall cracks – Treatment Large unstable cracks Debride unattached and necrotic horn Hoof wall resection Stabilization Bar shoe Acrylic patch Wire suture Plate/screw and wire Foot cast Topical treatment Biotine and methionine Hoof wall cracks – Prognosis Depends on: Location Depth Guarded – Good Recurrence if predisposing factors not addressed Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Traumatic injuries – Heel bulb lacerations Trauma to coronary band or heel bulb Over-reach injuries Diagnosis Visual inspection Painful in acute phase +/- Severe lameness “Chronic” Infection of hoof capsule Permanent damage to horn-producing cells Abnormal hoof growth (cracks, ridges) Heel bulb lacerations – Treatment Surgical debridement Removal of damaged horn Wound Primary closure when possible Immobilization – Foot cast Systemic antibiotics/anti-inflammatory medication Adjacent synovial structures Distal interphalangeal joint Navicular bursa Digital flexor tendon sheath Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Keratoma ”Tumor” of keratin producing cells Columnar or spherical shape Consist of poor-quality horn Decay early Allow bacteria and fungi to access inside of hoof wall Space occupying lesion +/-pressure necrosis of P3 Keratoma - Etiology Idiopathic Theory: Localized inflammation and trauma between horn producing layer and hoof wall → Formation of scar tissue → Scar tissue grow distad as new horn produced Hoof abscessation Keratoma – Diagnosis Hx – Chronic recurrent hoof abscess Clinical signs Abnormal configuration of the white line Displace white line towards sole Lameness Radiographs Circular lytic area of P3 Sclerotic border delineates lytic area Advanced imaging (CT/MRI) Keratoma – Treatment Surgical removal – Two main principles Complete removal of keratoma Complete hoof wall support Timing of surgery Treatment of inflammation medically first (?) Based on pain level Support limb laminitis! Procedure: Standing (tourniquet + local anesthesia) Hoof wall resection Local excision of keratoma Keratoma – Postoperative management Antiseptic pressure bandage Routine bandage changes Stall rest 4 – 6 weeks Shoeing +/- filling of hoof wall defect Hand walking 2 – 3 months Prognosis 83 % surgical vs 43 % conservative Partial hoof wall resection preferable Outline Anatomy of the foot Examination of the foot Laminitis Disorders of the hoof capsule Thrush White line disease Hoof wall cracks Traumatic injuries (heel bulb trauma) Keratoma Canker Canker Abnormal horn proliferation Most often frog region Can spread to sole and hoof wall Chronic inflammatory reaction Massive parakeratosis Hypertrophy of sensitive and superficial horn Corium degeneration Painful, slowly progressive disease Cause unknown Hind limbs more often affected Canker – Clinical signs Rubber-like consistency of horn Friable horn Cauliflower-like growth Non-cornified Greasy, grey-white material Foul odor Painful to pressure Lameness Hemorrhage (profuse) Ddx – Thrush Canker – Treatment Difficult and time consuming 75 – 86 % acceptable long-term outcome Recurrence > 50 % Step 1: Surgery Debridement of damaged tissue Repeat with recurrence Canker – Treatment Step 2: Medical management Local treatment with disinfectant, drying, and hardening of horn Step 3: Farrier When healing observed → Medical plate shoe Defect covered with iodine/zinc oxide/tannic acid/metronidazole Local/systemic antibiotics may be necessary Questions ? Lecture 2 – February 9th, 2023 Disorders of the hoof capsule – cont’d Subsolar abscess Pedal osteitis Traumatic injuries – penetrating wounds to the hoof Navicular disease Fractures within the hoof Disorders of the collateral cartilages