EQUINE LAMENESS: Proceedings of Fifth Bain-Fallon Memorial Lectures

EQUINE LAMENESS: Proceedings of Fifth BainFallon Memorial Lectures Edited by R. J. Rose; p u b l i s h e d by T h e A u s t r a l i a n E q u i n e V e t e r i n a r y Association; paperback; 208 pages; $25.50 (Australian)price includes posted airmail. On May 16-19, 1983, the Australian Equine Veterinary Association presented the Fifth Bain-Fallon Memorial Lectures. This series of meetings featured Equine Lameness as the sole topic. The speakers were Albert A. Gabel, Ohio State University; Leo B. Jeffcott, University of Melbourne; Ken A. Johnson, University of Sydney; Reuben J. Rose, University of Sydney; and Ron D. Sande, Washington State University. The book is divided into seven sections; Assessment of Lameness, Foot and pastern, Joint disease, Fetlock and metacarpus, Carpus and tendons, Upper forelimb and neck, and Hindlimb and back. Dr. Sande provides much helpful information on radiographic techniques in each of these sections. In discussing joint disease he says, "Width of the cartilage space is considered by many to be a cardinal sign in joint disease. This finding, if properly used and understood, is quite valuable. If not, it may be misleading. The width of the joint space is subject to parallax and two dimensional imaging is n o t o r i o u s l y deceptive. The student of radiography is cautioned to use two opposing views to avoid perceptual errors... The width of any cartilage space is a factor of the age of the patient, weight bearing status of the limb, angle of projection of the x-ray beam and the anatomic characteristics of the joint." Throughout the series Dr. Gabel presented 14 lectures. These provide some valuable insights into Standardbred lameness p r o b l e m s specifically and T h o r o u g h b r e d lameness problems in general. Dr. Gabel spoke about preventing lameness, emphasizing that proper selection in the breeding process is an important factor in the prevention of later lameness. A study Gabel made of 113 two-year-old Standardbred horses at the race track showed that "the use of x-rays of the distal radial physes does not appear to be a useful indicator of two-year-old Standardbred's ability to race or stay sound." Jeffcott lists at least five causes of cervical vertebral stenosis; c e r v i c a l v e r t e b r a l d i s p l a c e m e n t , m e d i c a l impingement of articular processes, functional stenosis of the vertebral canal, arthropathy of articular processes and synovial cysts. Dr. Johnson provides some good information on joint problems. "Complete immobilization of a joint in the period immediately following surgery is detrimental to the health of the articular cartilage," he says. "Also 176

complete and active weight bearing is contraindicated. Studies of the best postoperative regime are in their infancy, but the result of two groups are pertinent. "l)Continuous passive motion (CPM) is a new concept developed in experiments on rabbits. Non-weightbearing stifle joints were put in a continuous cycle of flexion and extension, through a range of 70 degrees. Full thickness articular cartilage defects in adult rabbits healed with hyaline cartilage in 44% of defects with C P M , 5% with intermittent m o t i o n a n d 3% w i t h immobilization. Also C P M caused significantly greater r e d u c t i o n in the s e v e r i t y of r a d i o g r a p h i c , g r o s s pathologic and biochemical lesions in the stifle joint of rabbits with acute septic arthritis, than did intermittent motion or immobilization. "2)Physiological joint loading in addition to normal joint motion is necessary to maintain integrity of articular cartilage. Experiments in dogs with below stifle amputation, showed articular cartilage degeneration even though stifle joint motion was still present but not under any load." Dr: Rose attempts to resolve some of the problems in the diagnosis of navicular disease. "Because of the confusion that has resulted from problems in diagnosis," Rose says, "Navicular disease has come to be regarded by many clinicians as the last hope of the diagnostically destitute." He describes techniques such as flexion test, extension test, palmar digital nerve block and radiography. Besides the standard forms of therapy, Rose describes the use of Isoxsuprine hydrochloride in treatment of navicular disease. This is a peripheral vasodilating agent which acts by a direct musculotropic effect on smooth muscle. "Its main use in veterinary medicine," says Rose, "has been as a uterine relaxant, but in man it has been used to treat peripheral vascular disease. With this in mind, the oral use of isoxsuprine was investigated as a possible treatment for navicular disease." His study showed that while clinical dose rates of 0.6 m g / k g of isoxsuprine paste produced no decrease in blood pressure, there was a significant increase in distal limb temperature, assessed using thermography. "This increase in distal limb t e m p e r a t u r e r e a c h e d a m a x i m u m of 3.1 d e g r e e s centigrade, 4 hours after oral isoxsuprine administration, implying a direct vasodilational effect. The increase in distal limb temperature persisted for up to 10-12 hours after treatment. "In clinical and double blind trials, the efficacy of isoxsuprine to treat navicular disease was shown and the dose rates that produced a clinical effect fell in the range 0.6-0.9 mg/dg. This is equivalent to 7-10 ml of Circulon paste (40 mg/ml) for a 450 kg horse. Eighty-eight per cent of horses became sound on treatment, and 90% of the horses that became sound remained sound for 2 months or more after ceasing 9-12 weeks of therapy. "As this treatment is a physiological one, it appears to be the most promising of the currently available forms of therapy. The long-term results also look encouraging, and some horses have remained sound 12 months or more after ceasing treatment."WEJ EQUINE VETERINARY SCIENCE