- Cause : traumatic penetration of navicular bursa usually via a solar penetration → infection within bursa → direct damage to navicular bone, deep digital flexor tendon.
- Signs : severe lameness [Musculoskeletal: gait evaluation] , puncture wound evident on frog or sole, draining wound above the heel.
- foot paring , plain and positive contrast radiography , centesis of the navicular bursa with cytology and culture/sensitivity of samples, intrasynovial anesthesia of the navicular and/or distal interphalangeal joint may result in gait improvement, post mortem (Fig. 1) .
- Treatment : surgical drainage and removal of infected and necrotic debris.
- Prognosis : depends on extent of infection and duration before effective treatment:
- Fair if confined to bursa.
- Guarded if navicular bone and deep digital flexor tendon involved.
Print off the Owner Factsheet on Penetrating foot injuries to give to your client.
- Forelimb/hindlimb, single limb lameness with reluctance of the horse to put the heel of the foot to the ground.
- Palpable swelling/pain between the bulbs of the heel and the ungual cartilages.
- Pain on digit flexion [Musculoskeletal: manipulative tests] .
- (Fig. 2) application over the frog.
- Discharging solar lesion, commonly located in the mid-third of the frog, often in the sulcus; visible after foot cleaning/sole paring.
- Guarded: if infection is confined to the bursa and treatment is initiated early.
- Guarded to poor: if navicular bone and deep digital flexor tendon are involved.
- Improves for: early and appropriate management; early return to exercise; endoscopic management.
- Horses treated with surgery within 7 days of the puncture had significantly better outcomes than those that were delayed longer.
- Hindlimb cases also had a better prognosis than forelimb.
- Endoscopic treatment of navicular bursal penetration has been as high as 75% successful in complete return to soundness. In addition, concurrent infections of adjacent synovial structures can be treated at the same time.
- Street-nail procedures involve radical surgery that may require second debridement and prolonged pain relief. Success rates after this procedure range between 18.4 and 31.6% for complete soundness.
Expected response to treatment
- Resolution of lameness.
Reasons for treatment failure
- Ongoing infection or inflammation.
- Extensive damage to the navicular bone and flexor tendon cartilage.
- Damage to surrounding soft tissue structure such as the DDFT which fails to heal.
- Infection in other structures such as the DIP joint or digital sheath that is not detected.
- Prolonged duration prior to treatment.