Roland Perrin

A technique for computed tomography (CT) of the foot in the standing horse

Summary Computed tomography (CT) in equine orthopaedics is currently limited because of the price, availability, impossibility to transport the scanner into surgical theatre, and the contraindications of general anaesthesia in some patients. A pQCT (peripheral quantitative computerised tomography) scanner was designed by the authors to image the limbs of the horse, both in standing or recumbent position. Standing computed tomography of the foot with a pQCT scanner is feasible and well tolerated by the horse. It enables good visualisation of bony structures but is not suitable to evaluate soft tissues. The technique can also assist surgery by assessing the 3D configuration of bone lesions.

Use of computed tomography to diagnose new bone formation associated with desmitis of the proximal aspect of the suspensory ligament in third metacarpal or third metatarsal bones of three horses.

CASE DESCRIPTION 3 horses with lameness localized to the proximal aspect of the metacarpus or metatarsus. CLINICAL FINDINGS All horses had evidence of problems that originated from the proximal aspect of the suspensory ligament (PASL), including signs of pain on palpation, positive results of diagnostic nerve blocks, ultrasonographic detection of enlargement and diffuse areas of reduced echogenicity in the proximal region of insertion of the ligament, and radiographic detection of increased mineral opacity in the proximal aspect of the metacarpus or metatarsus. Desmitis of the PASL was diagnosed in each horse; however, conservative treatment failed to improve the lameness. The horses were taken to surgery for splitting of the PASL and osteostixis of the proximal aspect of the third metacarpal or metatarsal bone. At that time, the proximal aspect of the metacarpus or metatarsus was evaluated via computed tomography (CT), which identified new bone formation at the proximal aspect of the third metacarpal or metatarsal bone that had not already been identified. TREATMENT AND OUTCOME In all horses, the newly formed bone was removed surgically under radiographic and CT guidance, and the splitting and osteostixis that had been planned were performed. After rehabilitation, all horses returned to full training at 6 months after surgery. All horses responded well to the surgical treatment and were sound 8 months afterward. CLINICAL RELEVANCE Use of CT imaging should be considered in lame horses with pain associated with the proximal aspect of the third metacarpal or metatarsal bones that does not improve with conservative treatment.

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.

Evaluation of a vessel sealing device to assist eye enucleation and exenteration in the horse.

Summary This study describes and evaluates the LigaSure for eye enucleation or exenteration in horses. According to the medical records of the Clinique Desbrosse, 17 horses underwent eye removal using the LigaSure between April 2005 and March 2009. It was applied at 7 different steps of the procedure and accounted for the different possible sources of bleeding. The Ligasure was also used to transect the optic pedicle in the 5 most recent cases. Very few complications were encountered with the technique described. Reliable vessel sealing and haemostasis was achieved in all horses.

Ex Vivo Assessment of an Ultrasound‐Guided Injection Technique of the Navicular Bursa in the Horse

Synovitis of the navicular bursa is common in performance horses. The objective of this study was to describe an ultrasound‐guided technique to inject a distended navicular bursa and to evaluate its feasibility for use by a clinician not trained in the technique. Twenty distal limbs of horses of various breeds and sizes were used. To produce synovial distension, the navicular bursa of each limb was injected with contrast medium using a lateral approach and radiography was performed to confirm that the contrast medium was distending the bursa. The digit was positioned with the distal interphalangeal joint in hyperextension. A microconvex ultrasound probe was placed in the hollow of the pastern, palmar to the middle phalanx and the region was assessed in a transverse plane slightly oblique to the horizontal plane. The ultrasound probe was rotated to visualize both the lateral and medial recesses and to select which side was more distended to inject. A 21G 0.8 × 50 mm needle was inserted abaxially to the probe in the plane of the ultrasound beam into the proximal recess of this navicular bursa and a methylene blue solution was injected. Following injection, dissection was performed to assess whether the navicular bursa had been successfully injected. This ultrasound‐guided technique was reliably performed with a success rate of 68%. The success of injection is influenced by hyperextension of the foot, quality of ultrasound images and degree of distension of the bursa.

LE TRAITEMENT DES FRACTURES CHEZ LE CHEVAL, OÙ EN SOMMES-NOUS?

Even in the early 21st century, the treatment of equine fractures remains a challenge for veterinary surgeons. In this presentation, we review the current situation as well as its historical background. The treatment of equine fractures is poised for rapid changes. Surgical techniques and patient management have improved, and surgeons have become more specialized. However, the small number of published cases shows that owners are not yet aware of the revolution which has taken place in this field. It is for us, veterinary surgeons, to make them see this new potential.