Navicular Syndrome - Equine

October 17, 2018
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Patient
Irish Sport Horse Fe, 7 year-old

History
This patient had a history of being reluctant to jump for several weeks.

Lameness Examination
On dynamic examination it was noted at the walk that the left fore landed lateral to expected foot placement. The right fore landed as expected.

When examined at the trot in a straight line there was a mild (2/10) right fore lameness. When lunged on a soft surface there was a mild (2/10) right fore lameness on the left rein and mild-to-moderate (3/5) right fore lameness on the right rein.

When lunged on a firm ground the patient showed mild (2/10) left fore lameness on a left rein and mild-to-moderate (3/10) right fore lameness on a right rein.

Physiological Screen with Digital Thermal Imaging

Digital thermal images were captured with a Digatherm IR camera.

Dramatic thermal asymmetry was noted in the distal fore limbs with the right limb showing hyperthermia throughout. The right fore hyperthermia was more pronounced medially (Fig 1.1 & Fig 1.2).

Fig. 1.1 – Anterior to posterior thermograms of the fore feet.

Fig. 1.2 – Posterior to anterior (bottom) thermograms of the fore feet.

Additional Diagnostics

Radiographs of patient’s front feet were obtained and showed moderate enlargement of the synovial invaginations within the distal border of both navicular bones. Mediolateral foot balance seemed adequate, but the right front showed a broken forward foot-pastern axis. Since there was no definite cause for the lameness on the radiographs, an MRI examination of both foot and pastern was performed.

MRI showed bilateral moderate navicular changes with enlargement of the synovial invaginations and enthesophyte (new bone) formation at the insertion of the collateral distal sesamoidean ligaments. There was STIR hyperintensity within both navicular bones (Figs. 2 & 3).

Mild degenerative joint disease of both distal and proximal interphalangeal joints on both front feet was noted.

Bilateral effusion of the digital flexor tendon sheath was noted. It was not correlated with any tendon lesion and likely represented a synovitis.

Diagnosis

Abnormalities observed in the navicular bones on both radiographic and MRI studies indicated navicular syndrome. Clinically there was suggestion of a more proximal pain component in the right fore.

Fig. 2 – MRI of the right front foot: Frontal T1W (left) and sagittal STIR images (right) of the navicular bone. Enlarged synovial invaginations and increased STIR signal are visible.

Fig. 2 – MRI of the right front foot: Frontal T1W (left) and sagittal STIR images (right) of the navicular bone. Enlarged synovial invaginations and increased STIR signal are visible.

Fig. 3 – MRI of the left front foot: Frontal T1W (left) and sagittal STIR images (right) of the navicular bone. Enlarged synovial invaginations and increased STIR signal are visible.

Fig. 3 – MRI of the left front foot: Frontal T1W (left) and sagittal STIR images (right) of the navicular bone. Enlarged synovial invaginations and increased STIR signal are visible.

Treatment Plan

The navicular bursa of both front feet was medicated with corticosteroids.

Remedial shoeing was recommended to include a 4 degree heel elevation (either with a wedge or a graduated bar shoe).

Controlled exercise was prescribed for 4-5 weeks to include twice daily hand walking exercise.

Value of the Digital Thermal Images

This patient presented with a history of being reluctant to jump for several weeks.

The thermal images demonstrated that there was an abnormality present and convinced the client of the urgency of obtaining a diagnosis.

The thermal images will serve as baseline data for continued monitoring of the patient.

Fig. 4 – Anterior to posterior visual image of the fore feet of a 7 year-old Irish Sport Horse with navicular syndrome.

Fig. 4 – Anterior to posterior visual image of the fore feet of a 7 year-old Irish Sport Horse with navicular syndrome.

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