Equis ISSN 2398-2977

Foot: subsolar abscess/infection

Contributor(s): Olin Balch, Simon Curtis, Graham Munroe, Vetstream Ltd

Introduction

  • Very common.
  • Usually due to penetrating foreign body and ingress of bacteria through the insensitive sole or frog of the foot; the pathology is in the deeper sensitive tissue which if severe enough may extend to the pedal bone periosteum, the digital cushion, navicular bursa, palmar/plantar partition of the coffin joint and insertion of the deep digital flexor tendon (DDFT). When such deeper tissues are involved the condition can become potentially life-threatnening. 
  • Signs: lameness of varying severity   Musculoskeletal: gait evaluation  , forelimb > hindlimb.
  • Diagnosis: foot examination   Foot / shoe: examination  and manipulative tests   Musculoskeletal: manipulative tests  ; foot trimming may reveal point of abscess; may be difficult even with radiography   Digit: radiography  .
  • Treatment: local drainage, and control of infection, pain and inflammation.
  • Prognosis: dependent on extent of initial damage, adequate treatment and rest.
Print off the Owner factsheets on Caring for your horse's feet and Subsolar abscess - pus in the foot to give to your clients.

Pathogenesis

Etiology

  • Penetrating foreign body, most likely through the sole or frog, eg nails, screws, wire, stones, glass or even wood.
  • May be iatrogenic, associated with nail misplacement during shoeing - nail prick or nail bind.
  • Infection may enter the hoof capsule through small defects in the horn, especially at the sole/heel junction.

Predisposing factors

General
  • Exercise in poor conditions such as wet muddy areas and hard rough ground can increase the incidence.
  • Poor foot shape and balance are common predisposing causes, most particularly the long toe/low heel conformation and poor mediolateral foot balance.

Pathophysiology

  • Infection into the foot   →   inflammation   →    increased pressure on sensitive hoof laminae   →    pain and lameness.
  • An abscess develops in the subsolar area, usually between thestratumgerminativumand thestratumcorneum, if penetration has been deep enough or if the infection spreads.
  • Abscessation may develop from previous bruise or hematoma   Foot: sole bruising  .
  • Pus develops and may discharge through the penetrating site, elsewhere through the sole or proximally around the coronet, typically opposite to the site of the infection.
  • Lameness diminishes with either natural or induced drainage.
  • If drainage occurs at the coronet (the junction of the hairline and the wall), short horizontal defects (cracks) may appear in the hoof wall and slowly move distally as the hoof grows out.
  • Forelimbs more commonly affected than hindlimbs.
  • Chronic discharge may lead to sinus and fistula development.
  • Infection may extend to any or all of the structures in the region, eg pedal bone, coffin joint, navicular bursa, DDFT.
  • Chronic abscessation may occur in chronic laminitis   Foot: laminitis  , immunocompromise, keratoma   Foot: keratoma  or septic osteitis   Bone: osteitis - septic  .

Timecourse

  • If infection becomes established the disease is likely to be protracted.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Milner P I (2011)Diagnosis and management of solar penetrations.Equine Vet J23(3), 142-147 VetMedResource.
  • Stephenson R (2011)Presenting signs of foot abscessation - A practice based survey of 150 cases.UK Vet16, 4-7 VetMedResource.
  • Carmalt J L (2009)What is your diagnosis? Subsolar abscess with secondary distal interphalangeal joint synovitis.JAVMA235(4), 377-378 PubMed.
  • Cullimore A (2009)Clinical aspects of the equine foot. Part 4: Sole penetrations.UK Vet14(5), 8-13 VetMedResource.
  • Leonard J Met al(1990)What is your diagnosis? Hoof abscesses and cellulitis extending along the palmar aspect of the pastern of the left forelimb.JAVMA196(1), 1791-1794 PubMed.
  • DeBowes R Met al(1989)Penetrating wounds, abscesses, gravel and bruising of the equine foot.Vet Clin North Am Equine Pract5(1), 179-194 PubMed.
  • Fessler J F (1989)Hoof injuries.Vet Clin North Am Equine Pract5(3), 643-664 PubMed.
  • Jamison J Met al(1983)What is your diagnosis? Sole abscess involving the lateral and plantar aspects of the foot.JAVMA182(6), 625-626 PubMed.


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