Laminitis

Laminitis is inflammation and failure of the interdigital lamellae that suspend the distal phalanx (P3) within the hoof capsule. When lamellae fail, P3 rotates or sinks, causing severe pain and permanent structural damage.

Types by etiology:

• Endocrinopathic (metabolic): Most common (~90% of cases). Associated with PPID (pituitary pars intermedia dysfunction) and EMS (equine metabolic syndrome/insulin dysregulation). Hyperinsulinemia directly damages lamellae.
• Inflammatory / septic: Systemic inflammation (SIRS), endotoxemia from colic/colitis, retained placenta, severe infection, carbohydrate overload (grain founder)
• Mechanical (supporting-limb): Contralateral to severe lameness (e.g., non-weight-bearing on one limb → overload on opposite)
• Corticosteroid-associated: Controversial; prednisolone may trigger in susceptible horses

Clinical signs: Acute — bounding digital pulses, heat in hooves, reluctance to move, classic 'sawhorse' stance (front feet extended), shifting weight. Chronic — divergent growth rings (wider at heel than toe), flat sole, recurrent abscesses, altered hoof shape.

Clinical diagnosis: Digital pulse palpation, hoof tester response, gait assessment, stance evaluation.

Radiographs (essential):

• Lateral view: Assess P3 rotation relative to hoof wall (normal coronet-to-extensor process distance ~10–14 mm), sole depth, evidence of sinking
• Dorsopalmar view: Assess P3 position within hoof capsule, evidence of medial/lateral rotation or asymmetry
• Founder lines: Radiolucent lines parallel to coronary band seen on chronic cases

Endocrinopathic workup:

• Baseline ACTH: Screen for PPID (seasonal reference ranges apply)
• Insulin: Fasting or dynamic testing (OST — oral sugar test) for insulin dysregulation/EMS
• Leptin: Adipokine marker for EMS

Differentiate from: Subsolar abscess, navicular syndrome, pedal osteitis, white line disease

Acute phase:

• Cryotherapy: Ice boots or ice water slurry on distal limbs for 48–72h (anti-inflammatory, vasoconstrictive; especially important in septic/endotoxic cases)
• Analgesia: NSAIDs (phenylbutazone, flunixin meglumine, firocoxib); opioids if severe
• Deep bedding / support: Sand bedding, supportive pads, frog support (e.g., lily pads, commercial boots)
• Restrict movement: Stall rest; controlled hand-walking once stabilized

Address underlying cause:

• Endocrinopathic: Manage insulin — low NSC diet, weight loss, pergolide for PPID, metformin (controversial but used)
• Septic/endotoxic: Treat primary disease (colic, colitis, retained placenta, infection)
• Mechanical: Address primary lameness; support contralateral limb

Chronic management:

• Corrective/farriery: Radiograph-guided trimming, heel elevation if rotated, therapeutic shoeing (heart bar, clogs, rail shoes)
• Diet: < 10% NSC (non-structural carbohydrates), no pasture access during high-sugar times (spring/fall, morning)
• Exercise: Gradual increase once controlled
• Monitor ACTH/insulin regularly in PPID/EMS horses