Thomas Launois

Use of Computed Tomography in Standing Position to Identify Guidelines for Screw Insertion in the Distal Phalanx of Horses: An Ex Vivo Study

OBJECTIVES To compare the precision of radiography and computed tomography (CT) preoperatively in the standing position for identification of guidelines for screw insertion in the distal phalanx, and to identify whether standing CT might improve operative time compared with preoperative radiographic planning. STUDY DESIGN Experimental ex vivo study. ANIMALS Cadaveric equine thoracic limb pairs (n=10). METHODS Insertion of a 4.5 mm cortex screw in lag fashion into an intact distal phalanx was evaluated in 2 groups (n=10) of cadaveric equine thoracic limbs. In 1 group, the site, direction, and length of the implant were determined by radiography, and in the other group, by CT. Accuracy of screw placement was verified by specimen dissection. Outcomes were (1) absence of penetration of the articular surface, the solar surface, or the semilunar canal (2) appropriate length and direction of the screw. Surgical time was also measured. RESULTS No screw penetrated the articular surface, the solar surface, or the semilunar canal in either group. CT was more accurate to identify guidelines for screw insertion (U=23.50, P=.049). With CT, surgical time (mean, 7.7 minutes) was significantly shorter (U=0.000, P=.000) than with radiography (mean, 12.7 minutes). CONCLUSION Standing CT can be used to accurately determine anatomic landmarks for screw insertion in lag fashion in sagittal fractures of the distal phalanx. CLINICAL RELEVANCE This study has a clear clinical relevance for improved internal fixation of sagittal fractures of the distal phalanx.

Computed Tomography and Magnetic Resonance Anatomy of the Normal Orbit and Eye of the Horse

Traumatic and infectious diseases of the eye and orbit can occur in horses. For diagnosis and monitoring of such diseases, medical imaging is useful including computed tomography (CT) and magnetic resonance imaging (MRI). The aim of the current study was to describe CT and MRI anatomy of the equine orbit and ocular globe. The heads from four adult horses were scanned with a 6‐slice Emotion 6 CT (Siemens, Erlangen), and a 3.0 Tesla Siemens Verio 6 MRI using T1 and T2‐weighted sequences. To validate CT and MR reference images, these were compared with anatomical models and gross anatomical sections. The bony limits of the orbital cavity, the relationship of the orbit with sinuses and foramina of the skull were well identified by CT. MRI was useful to observe soft tissues and was able to identify adnexae of the ocular globe (eyelids, periorbital fat, extraocular muscles, lacrymal and tarsal glands). Although MRI was able to identify all components of the eye (including the posterior chamber), it could not differentiate sclera from choroid and retina. The only nerve identified was the optic nerve. Vessels were not seen in this series of cadaver heads. This study showed that CT and MRI are useful techniques to image the equine orbit and eye that can have clinical applications.

LE TRAITEMENT CHIRURGICAL DES FRACTURES DU DOIGT CHEZ LE CHEVAL, ASSISTÉ PAR LE SCANNER

In sport horses, fractures of the digit are common, especially in the distal and proximal phalanxes. They can be simple or comminuted, and they are frequently intra-articular. Accurate reconstruction and strong stabilisation are compulsory to limit the development of osteoarthritis. CT-assisted surgery relies on the acquisition of images before or during the surgical procedure, to visualize the fracture in two or three dimensions, and assist the surgeon in his decision and surgical procedure. We use computed tomography pre- or preoperatively, as when preparing surgery on a foot with the horse standing. The objective of this article is to present both techniques and describe three clinical cases: a fracture of the distal phalanx and two different types of fractures of the proximal one.

Computed tomography to identify preoperative guidelines for internal fixation of the distal sesamoid bone in horses: an in vitro study.

OBJECTIVE To assess the reliability of computed tomography (CT) to identify the direction of implant insertion for cortical screws along the longitudinal axis of intact (nonfractured) distal sesamoid bones. STUDY DESIGN In vitro study. SAMPLE POPULATION Cadaveric paired equine forelimbs (n=16). METHODS Insertion of a cortical screw in lag fashion along the longitudinal axis of intact (nonfractured) distal sesamoid bones was evaluated in 2 groups (3.5 and 4.5 mm) of 8 paired limbs. In each group, the direction of the distal sesamoid bone was determined by CT (Equine XTC 3000 pQCT scanner). Screw placement was verified by specimen dissection. Implant direction was considered satisfactory if the entire screw length was within the distal sesamoid bone and not damaging the articular or flexural surfaces. RESULTS In our sample and according to our criteria, the proportion of satisfactory direction of screws was 0.63 (5/8) for 4.5 mm implants, and 0.87 (7/8) for 3.5 mm implants. CONCLUSIONS CT is a useful imaging modality to identify anatomic landmarks for insertion of a 3.5 mm cortical screw in the distal sesamoid bone.

KÉRATITES NON ULCÉRATIVES CHEZ LE CHEVAL

The horse’s cornea is particularly prone to aggressive inflammatory conditions, characterized by neovascularization, fibroplasia and a strong cellular response resulting in a disorganization of the corneal structure and maintaining the inflammatory reaction. Non-ulcerative keratopathies include immunemediated keratitis (IMMK), non-ulcerative kerato-uveitis, endothelial dystrophy/degeneration, calcific corneal dystrophy/degeneration, stromal abscess and onchocercosis. Surgical and medical treatments are designed to control the inflammatory response and fibroplasia, as well as limit the extension of the corneal edema. Equine ophthalmology relies on the use of various advanced techniques, often similar to those used in human medicine, though sometimes limited by the anatomical and physiological specificities of the equine eye