EQUINE VETERINARY EDUCATION / AE / MARCH 2015
133
Case Report Pseudo-polydactyly in a horse
L. Valbonetti*, C. Briola†, U. Tosi, G. Marruchella and A. Muttini Faculty of Veterinary Medicine, University of Teramo, Teramo, Italy; and †Clinica Veterinaria Roma Sud s.r.l., Veterinary Practitioner, Rome, Italy. *Corresponding author email:
valbonettiluca@gmail.com
Keywords: horse; hoof; malformation; polydactyly
Summary A 14-month-old half-breed horse showed a severe lameness due to a lesion of the right forefoot which appeared completely and asymmetrically cleaved, from the solar margin to the coronary band. The horse was presented to an abattoir for slaughter and both forelimbs were collected for diagnostic investigations. The hoof lesion described herein does not fulfil the diagnostic criteria of equine polydactyly since post mortem imaging and pathological investigations ruled out the presence of supernumerary digits. Based on the clinical signs, diagnostic imaging (computed tomography) and gross examination, a diagnosis of pseudo-polydactyly was proposed. To the best of our knowledge, the features of the present case report are unique, thus widening the range of lesions observed at the level of the hoof, which is crucial for horse health and activity.
Case history
A 14-month-old half-breed horse was referred to the Veterinary University of Teramo (Italy) for severe lameness apparently caused by a malformation of the right forelimb. The horse was at pasture with his mother until 12 months old and was then confined in a stable until clinical evaluation, 2 months later. At that time, the owner reported a ‘hoof crack’ that was observed a few days after birth.
Clinical and post mortem findings The subject under investigation showed an excellent body condition although the right forefoot appeared completely
and asymmetrically cleaved from the solar margin to the coronary band. A severe lateral deviation of the digit was evident. The same digit was also externally rotated showing a toe-out conformation (Fig 1). A grade 4 lameness (AAEP scoring; Baxter and Stashak 2011) was observed. The lameness was severe at walk and at trot in a straight line, with a shortened stride and a clear lateral deviation of the digit during the stance phase. The low 4-point palmar block led to a visible improvement of the lameness. The horse was slaughtered and the distal part of both forelimbs collected for diagnostic imaging and pathological investigations. A computed tomography (CT) study of both forelimbs
was performed using a CT scanner (Philips MX 16-slices)1. The sequences were acquired by spiral technique with overlapping, with 1mm thickness, 1mm of gap, 120 Kv and 130 mAs. Bi-dimensional (2D) and 3-dimensional (3D) rendering were acquired using open source software (VolView 3.4)2.
Computed tomography study of the right distal forelimb
did not demonstrate the presence of any supernumerary bone. In detail, the metacarpal bones appeared normal, while the proximal (PP), middle (MP) and distal (DP) phalanges were changed, deviated and axially rotated. Planar and 3D rendering showed a severe reduction of the DP size, internal rotation of the MP and bone remodelling with exostoses which was more prominent on the MP and DP (Figs 2 and 3). Computed tomography examination of the distal left forelimb revealed no apparent abnormalities. The morphology and topography of the bones, as well as the
Fig 1: Right forelimb. The distal part is laterally deviated and the hoof apparently cloven into two asymmetric portions. The lateral portion is smaller and shows a traumatic injury of the toe. At inspection and palpation, the lateral part of the hoof was mobile and likely devoid of a skeletal structure (a). Both hoof portions were completely covered by a continuous layer of horn and separated by a clearly evident interdigital space (b).
a)
b) © 2015 EVJ Ltd
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