Mechanical Properties and Failure Mode of Proximal Screw Fixation Technique Using Locking Compression Plate for Proximal Interphalangeal Arthrodesis in Horses: An Ex Vivo Study.

OBJECTIVE: The aim of this study was to measure the mechanical properties and failure mode of an ex vivo model of proximal interphalangeal arthrodesis in horses with different methods of proximal screw fixation using a locking compression plate. STUDY DESIGN: Pastern joint arthrodesis with a 3-hole 4.5-mm narrow locking compression plate was performed on 20 forelimbs of equine cadavers, randomized into four groups based on the fixation method and type of proximal screw used: unicortical cortex, bicortical cortex, unicortical locking, bicortical locking. Single-cycle axial compression testing was conducted until failure. The frequency of implant plastic deformation was recorded. Bone failure analysis was performed through computed tomography examinations and fractal analysis. RESULTS: There were no differences in the analysed mechanical variables and fractal dimension among the groups. Transarticular screws showed a higher frequency of deformation (75%) regardless of the group. Both unicortical locking and bicortical locking groups deformed the plate more frequently. CONCLUSION: The type of screw used in the proximal hole of the locking compression plate and its method of anchoring in the proximal phalanx do not affect the mechanical properties of pastern arthrodesis in equine cadavers subjected to single-cycle axial compression tests until failure.

Ultimobranchial body cyst in an adult horse: clinical, histopathologic, and immunohistochemical features.

A 9-y-old Mangalarga Marchador gelding was referred to a veterinary hospital because of a swelling on the upper right side of the neck. Ultrasound examination revealed a multilocular structure adjacent to the thyroid gland with low echogenic content suggestive of fluid. The mass was removed surgically. Histologically, the cystic cavities in the surgical sample were filled with abundant eosinophilic secreta and lined by cuboidal, segmentally ciliated, columnar epithelium with interspersed goblet cells. Segmental crowding of the multilayered lining of the cyst was noted. Immunohistochemistry suggested the presence of both C cells and follicular cells, given the positivity of the immunomarkers calcitonin and TTF-1, respectively. The histogenesis of ultimobranchial cysts is uncertain. Based on clinical, histopathologic, and immunohistochemical identification, the cystic structure in this case is compatible with an ultimobranchial body cyst.