Picked-up nail – Diagnosis

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

History

Most horses will have a known history – the owner or handler may have noticed the moment of penetration or found a foreign object embedded when picking out or examining a hoof. The foreign body may be left in place by an owner if there is no risk of the object penetrating deeper if the horse bears weight. In other cases, the penetrating object will have been removed; if this is the case, the person who removed it will ideally have marked the site of penetration on the hoof capsule (a hoof knife leaves a more permanent mark than even a permanent felt pen!) and will have made a note of the depth and direction of penetration.

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Inspection

Normally, the diagnosis is relatively easy to make thanks to the history and obvious findings; the foreign body is often visible, totally or partially embedded in the hoof capsule. If the foreign body has already worked loose, a trace of blood on the hoof can be an indicator of a foreign body penetration. In this case, it is prudent to check the horse’s surroundings to see whether any objects lying around can give some indication of the nature of the object that has penetrated the hoof (nails, screws, etc).

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Palpating the pulse in the digital artery

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Palpation

Care is needed when locating and exposing a foreign body that has become embedded into the underside of the hoof. Since any manipulation of the affected area is extremely painful, examination with the hoof testers can elicit hefty pain reactions.

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Exposing the puncture wound

Once the foreign body has been removed, the hoof should be cleaned, the shoe removed and the sole and frog carefully trimmed. The entry hole of the puncture channel shows up as a black slit or hole in the horn. Any suspect site must be pared away with the hoof knife. The exact extent of the puncture will only become properly evident once the deep puncture channel has been exposed and widened. Synovial fluid, blood or even pus may be discharged in the process. This allows the puncture site to be readily distinguished from any superficial discoloration in the horn, such as may occur with corns.

Matthias Haab, Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Abaxial sesamoid block

Regional anaesthesia (nerve blocks)

In many cases, regional anaesthesia is indicated to prevent pain reactions by the horse when removing the foreign body or exposing the puncture channel. In any case, the affected region will need to be anaesthetised with an abaxial sesamoid nerve block before the puncture channel is probed up to the sensitive dermis.

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Irrigation and probing

After the outer opening of the puncture channel has been opened up, the entry hole needs to be widened, thoroughly cleansed and irrigated with a disinfectant solution (Betadine or chlorhexidine). Subsequently, a sterile probe can be carefully inserted into the puncture channel to determine its depth and direction.

Matthias Haab, Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Puncture of the distal interphalangeal (coffin) joint with a needle

Matthias Haab, Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Matthias Haab, Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Needle aspiration of the synovial structures

If involvement of the synovial structures (coffin joint, DFTS, navicular bursa) is suspected, the structure should be aspirated with a needle following the sterile preparation, at a site distant to the wound. The synovial fluid is collected in an EDTA sample tube and examined in the laboratory for its cell content. If no synovial fluid can be harvested, sterile lactated Ringer’s solution should be applied with careful positive pressure and any discharge of fluid through the foreign body entry site noted. The aspirated synovial structure is then treated locally with antibiotics (gentamicin or amikacin).

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Departement für Pferde, Vetsuisse-Fakultät Universität Zürich

Radiography

Different structures within the hoof may be injured depending on the location and depth of the puncture wound. Radiographs in two planes with a probe inserted into the puncture wound provide more detailed indications about the extent of the injury. A study using contrast medium can provide further information about the affected structures. The joint suspected of being penetrated (usually the coffin joint) should be filled with at least 10ml of contrast medium. The hoof is then radiographed after a few minutes to determine whether the contrast medium drains out through the puncture channel. The navicular bursa and the DFTS can be examined selectively using the same technique.