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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Palmar foot lameness due to injury of NB and/or NB apparatus (impar ligament, collateral suspensory ligament, distal DDFT, navicular bursa).
  • NB degeneration due to abnormal forces in heel (NB, surrounding ligaments, DDFT).
  • Faulty distal limb conformation, improper hoof balance, and poor shoeing lead to abnormal forces in navicular area.
  • Musculoskeletal system—foot

Signalment!!navigator!!

  • Middle age.
  • Quarter Horses primarily, Thoroughbreds, Warmbloods, mixed breeds.
  • Rare in ponies, donkeys, mules, Arabians, drafts

Signs!!navigator!!

Historical Findings

  • Initially intermittent, slowly progressive lameness.
  • Lameness worse on hard ground.
  • Bilateral forelimb lameness.
  • ±Unilateral forelimb lameness, rare in hindlimbs.
  • Short, choppy stride.
  • Stumbling.
  • Increased lameness right after shoeing.
  • ±Point affected limb.
  • With soft tissue injury, unilateral acute lameness

Physical Examination Findings

  • Long toe–low heel conformation.
  • Heat in hoof capsule.
  • Increased digital pulses.
  • ±Hoof tester pain in frog or heels.
  • Atrophied frog.
  • Lameness, often bilateral, more lame in 1 limb

Causes and Risk Factors!!navigator!!

  • Hoof imbalance.
  • Poor or inadequate shoeing.
  • Poor hoof conformation (long toe–low heel, excessive toe length, underrun heel).
  • Lack of heel support.
  • Quarter Horse breed.
  • Big horse with small feet.
  • Faulty distal limb conformation.
  • Mismatched front feet.
  • Excessive hard ground work

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Laminitis—acute, severe bilateral forelimb lameness. Hoof tester pain in toe.
  • Sheared heels.
  • Bruised feet

Imaging!!navigator!!

Radiography—Navicular Bone

  • Variable sized synovial foramina.
  • Osteolysis or cyst formation.
  • Enthesophyte.
  • Flexor cortex erosion.
  • Medullary sclerosis.
  • DDFT calcification.
  • Distal bone fragments

Ultrasonography—Transcuneal Approach

  • Distal DDFT tendonitis.
  • Impar desmitis.
  • Navicular bursitis

Nuclear Scintigraphy

Increased radiopharmaceutical uptake in palmar foot.

MRI

  • Best imaging for soft tissue injury (distal DDFT, collateral suspensory ligament, impar ligament, distal annular ligament, navicular bursa).
  • NB edema

Other Diagnostic Procedures!!navigator!!

  • Diagnostic analgesia—palmar digital, IA DIP, or navicular bursa.
  • Navicular bursoscopy.
  • Contrast radiography of navicular bursa

Pathologic Findings!!navigator!!

  • NB cartilage erosion.
  • Linear or core DDFT lesions.
  • Adhesion between DDFT and NB

Treatment ⬆ ⬇

TREATMENT

  • Rest.
  • Improve/restore hoof balance, shorten toe, ease foot breakover.
  • Heel support, secondary wedge shoe or pad, eggbar shoe.
  • IA medication (DIP, navicular bursa, or digital tendon sheath).
  • Reduce workload, expectations.
  • Palmar digital neurectomy
  • Biophospate therapy (Osphos IM)

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • NSAIDs—phenylbutazone (2.2 mg/kg every 24 h for 7–10 days).
  • Isoxsuprine hydrochloride (1 mg/kg PO every 12 h for 3 weeks then 1 mg/kg every 24 h PO for 3 weeks, then 1 mg/kg PO every 48 h for 3 weeks).
  • IA corticosteroids—methylprednisolone acetate (20–40 mg) or triamcinolone (3–6 mg).
  • IA sodium hyaluronate (10–20 mg).
  • IA corticosteroids and sodium hyaluronate combination.
  • Systemic chondroprotective drugs—polysulfated glycosaminoglycan (500 mg IM every 4 days for 7 treatments) or sodium hyaluronate (40 mg IV every 7 days for 3 treatments).
  • Oral chondroprotective medications—glucosamine/chondroitin sulfate powder (1 scoop (3.3 g) every 12 h), bisphosphonate (Osphos; clodronate (clodronic acid) injection) (60 mg/mL, 15 mL IM divided into 2 sites; ± repeated >6 months)

Contraindications/Possible Interactions!!navigator!!

  • IA corticosteroids not recommended with previous laminitis.
  • ±Mild abdominal discomfort <30 min after clodronate

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Reassess lameness after medical therapy.
  • ±NSAIDs prior to excessive use.
  • ±IA DIP/navicular bursa medication, 2 or 3 times per year.
  • Therapeutic trim, shoe every 6 weeks

Prevention/Avoidance!!navigator!!

  • Workload reduction, alterative sport.
  • Frequent, proper trimming and shoeing

Possible Complications!!navigator!!

  • Laminitis secondary to IA corticosteroids.
  • Gastric ulceration, right dorsal colitis, or kidney damage secondary to chronic NSAIDs.
  • Neuroma formation, nerve regrowth, DDFT rupture after palmar digital neurectomy

Expected Course and Prognosis!!navigator!!

  • Early mild disease—return to athletic use with medical therapy.
  • Usually progressive—increased lameness, NB degeneration expected.
  • After neurectomy—sound for 2 years. Surgery as last resort owing to postoperative complications.
  • DDFT injury—poor for athletics

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Sheared heels, chronic heel bruising in poorly conformed foot.
  • DIP disease or arthritis

Age-Related Factors!!navigator!!

  • Uncommon <5 years.
  • Palmar digital neurectomy not recommended in younger horses

Synonyms!!navigator!!

  • Caudal heel pain.
  • Navicular disease.
  • Palmar foot pain

Abbreviations!!navigator!!

  • DDFT = deep digital flexor tendon.
  • DIP = distal interphalangeal joint.
  • NB = navicular bone.
  • IA = intra-articular.
  • MRI = magnetic resonance imaging.
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Dabareiner RM, Carter GK. Diagnosis, treatment, and farriery for horses with chronic heel pain. Vet Clin North Am Equine Pract 2003;19:417–441.

Author(s) ⬆

Author: Robin M. Dabareiner

Consulting Editor: Elizabeth J. Davidson