Penetrating injuries to the hoof (solar penetrations) are an infrequent but potentially catastrophic injury in horses. It occurs when a horse stands on a nail or sharp foreign body that becomes lodged in the sole of the hoof and penetrates into the deeper structures.
Photo Credit: Neil Townsend MSc BVSc MRCVS, Three Counties Equine Hospital
The degree of lameness presented by a horse with a solar penetration injury varies depending on the location and depth of the foreign body, as well as the duration of time the object has been embedded. Most commonly, the horse will be non-weight bearing on the affected hoof, appearing “hopping” lame.
The immediate temptation is to remove the penetrating object in order to relieve pain and discomfort. However, this can give a false impression of the seriousness of the injury, as infection of the internal structures of the hoof can result.
Structures potentially affected include the pedal bone, navicular bursa (a synovial fluid filled space that cushions the deep digital flexor tendon as it courses over the navicular bone), the digital tendon sheath (contains a small amount of synovial fluid to enable movement of the flexor tendons around the pastern bone), and the deep digital flexor tendon1.
Ideally, the offending object must be left in place and the leg supported with a bandage while a vet is called. With the foreign object still in place, further investigations such as x-rays can help establish the extent of damage to the internal structures of the hoof.
Appropriate and rapid veterinary action can permit treatment before infection becomes established, and can greatly improve prognosis. Superficial penetrations can be removed by a vet and often treated by cutting away damaged tissue, bandaging and poulticing. Antibiotics may be given and careful use of pain relief made without masking signs of any deteriorating lameness.
Foreign bodies penetrating a synovial cavity, for example the navicular bursa, carry a more guarded prognosis, with surgery inevitably required to clear out debris and flush out contamination.
A study of solar penetrations involving synovial structures found that only 56 percent of horses were discharged from hospital, despite aggressive treatment, with only 36 percent returning to their previous athletic function2.
Good yard and field maintenance is so important to decrease the risk of solar penetrations. This type of injury is also a recognised risk factor for tetanus – it is vital to ensure that your horse’s tetanus vaccination is up to date.
1. H. O’Neill, B. O’Meara (2010). Diagnosis and treatment of penetrating injuries of the hoof in horses. In Practice, Volume 32
2. J. A. Findley et al. (2013). Outcome of horses with synovial structure involvement following solar foot penetrations in four UK veterinary hospitals: 95 cases. Equine Veterinary Journal ISSN 0425-1644