Suspensory Apparatus Prosthesis in the Horse Part 1: In Vitro Mechanical Properties

Mechanical properties of equine suspensory apparatus preparations and three braided synthetic prostheses were evaluated in vitro. Force versus displacement plots and failure modes were recorded from single load-to-failure testing in 18 cadaver limbs before and after replacement of each suspensory apparatus with a prosthesis. Mean load at failure, energy to failure, and stiffness values of polytetrafluoroethylene (PTFE) prostheses were lower than those of the suspensory apparatus and aramid prosthesis. The PTFE prosthesis failed by elongation or rupture of the prosthesis. Mechanical properties of the aramid prosthesis with collar augmentation were not significantly different from the suspensory apparatus. The main site of failure in both aramid prostheses was at the screw fixation to bone.     

Reverse Saphenous Conduit Flap in Cats: An Anatomic Study

The vascular anatomy of the reverse saphenous conduit flap in cats was denned by contrast radiography of both hindlimbs of 18 feline cadaver specimens. In all 36 flaps, flow of contrast medium from the femoral artery to the distal end of the flap was documented. Direct anastomosis of the superficial branch of the cranial tibial artery with the cranial branch of the saphenous artery and communication of the caudal branch of the saphenous artery with the perforating metatarsal artery, via the medial and lateral plantar arteries, was documented. The cranial branch of the medial saphenous vein was shown to anastomose with the cranial branch of the lateral saphenous vein. The presence of these anastomoses support the feasibility of the reverse saphenous conduit flap as an option for reconstruction of wounds of the metatarsus in cats.     

Arthrographic Analysis of Communication between the Tarsometatarsal and Distal Intertarsal Joints of the Horse

The intra-articular anatomy of 103 equine tarsi was studied by contrast radiography with image intensification and computerized tomography. There was communication between the tarsometatarsal and distal intertarsal joints in 21 of 55 (38%) interpretable tarsometatarsal arthrograms, and in 11 of 48 (23%) interpretable distal intertarsal arthrograms. The difference was not significant. The volume of contrast agent and the pressure of injection did not correlate with communication. Forced injection caused subcutaneous leakage of contrast medium but not communication. Communication occurred via the tarsal canal and the space between the third and the combined first and second tarsal bones. Injection of the distal intertarsal joint from the dorsomedial aspect of the limb, distal to the palpable distal border of the medial branch of the tendon of the tibialis cranialis muscle and between the central, third, and combined first and second tarsal bones, provided reliable access except in the presence of severe periosteal proliferations.     

Microvascular Free Tissue Transfer of the Rectus Abdominis Muscle in Dogs

OBJECTIVE: To assess donor-site morbidity and survival of the rectus abdominis muscle with an overlying skin graft after free tissue transfer to a medial femorotibial defect in dogs. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Phase 1: 6 canine cadavers; phase 2: 7 adult mixed-breed dogs. METHODS: Phase 1: The rectus abdominis muscle was removed from canine cadavers, muscular and vascular dimensions were recorded, and angiography was performed. Phase 2: Muscular transfer was performed through anastomosis of the caudal epigastric artery and vein to the saphenous artery and medial saphenous vein. Transferred tissues were evaluated on postoperative days 3, 6, 10, and 13. Animals were examined daily until euthanasia between postoperative days 31 and 42. Postmortem angiograms were performed and tissues collected for histopathologic evaluation. RESULTS: Phase 1: Appropriate vascular dimensions for microvascular anastomosis were confirmed and surgical technique perfected. Phase 2: Muscular excision produced minimal donor-site morbidity. All muscles survived after microvascular transfer and angiography confirmed vascular patency. All of the skin grafts survived, with one graft undergoing partial necrosis. CONCLUSIONS: The rectus abdominis muscle can be successfully transferred to a medial femorotibial defect and can serve as a bed for acute skin grafting. No significant donor-site morbidity is associated with its removal. CLINICAL RELEVANCE: Microvascular free tissue transfer of the canine rectus abdominis muscle has not been previously described. This technique provides a new alternative for repair of appropriate wounds. Additional studies are needed to define its utility in clinical patients.     

Incorporation of Fresh and Cryopreserved Bone in Osteochondral Autografts in the Horse

The structural integrity of subchondral bone in fresh and frozen osteochondral autografts was investigated at month 3 in 10 horses. Two osteochondral autografts were harvested from the lateral aspect of the lateral trochlear ridge of the left talus in each of 10 anesthetized horses. Grafts were frozen in 7.5% DMSO. After 14 days, the thawed grafts were press-fitted into drill holes in the trochlear ridges of the right stifles. A fresh graft from the right hock was implanted in each left stifle. To control for the effects of surgery, a fresh graft was transferred from the right stifle to the left stifle. The end result was two grafts in each femoropatellar joint. Fresh and frozen bone grafts maintained a structurally intact support for the cartilage surface. Graft stability and surface congruency were determining factors in the outcome of the grafts. Incorporation of both types of graft was complete at month 3, but remodeling of the fresh grafts was more active.     

Endoscopic Examination of Normal Paranasal Sinuses in Horses

The frontal, caudal maxillary, and rostral maxillary sinuses of 10 equine cadavers were examined endoscopically, and the findings were confirmed by sinusotomy. Similar endoscopic examinations were performed in five conscious, adult horses by using sedation and local anesthesia. Useful portals of entry for the arthroscope in adult horses were: for the frontal sinus, 60% of the distance in a lateral direction from midline to the medial canthus and 0.5 cm caudal to the medial canthus; for the caudal maxillary sinus, 2 cm rostral and 2 cm ventral to the medial canthus; and for the rostral maxillary sinus, 50% of the distance from the rostral end of the facial crest to the level of the medial canthus and 1 cm ventral to a line joining the infraorbital foramen and the medial canthus. The frontal sinus portal was most useful for examination of the frontal and caudal maxillary sinuses. The caudal maxillary sinus portal was most useful for examining the sphenopalatine sinus. Structures in the frontal and caudal maxillary sinuses could be approached surgically by viewing them through the frontal sinus portal and guiding an instrument to them through the caudal maxillary sinus portal. Tooth root identification was reliable for the second and third upper molars in animals older than 5 years, but was more difficult for the rostral teeth and in younger animals. Endoscopy was not difficult to perform and was well tolerated in standing, sedated horses. The only complication of this procedure was mild, local subcutaneous emphysema that resolved spontaneously within 14 days.