AAEP Convention 2004 Wrap-Up: Kester News Hour
Probably the best-attended session at the American Association of Equine Practitioners (AAEP) Convention, the Kester News Hour features brief reports of new research that was too new or brief for inclusion in the scientific program. The information is presented in a fun, rapid-fire format by two of the country's top equine veterinary specialists--internal medicine guru John Madigan, DVM, MS, Dipl. ACVIM, professor of medicine and epidemiology and section chief of equine medicine at the Veterinary Medical Teaching Hospital of the University of California, Davis; and orthopedic surgery specialist Larry Bramlage, DVM, MS, Dipl. ACVS, a partner in Rood and Riddle Equine Hospital in Lexington, Ky., and the immediate past president of the AAEP. Following are brief reports of the research they found important for this popular session.
Bone Mass and Exercise
Bramlage discussed a 10-year study of 112 12-18-year-old women, which found that exercise was more beneficial than calcium supplementation in developing strong bones. This study, which investigated the value of calcium supplementation on bone mass (40-50% of bone mass is formed during adolescence), found no difference in bone mass with supplementation, but exercise increased it 3-5%.
"These were not athletes; it was just moderate exercise," Bramlage commented. "So should we train 2-year-olds? Many have felt that training a 2-year-old gets them a better start on developing a good skeleton than waiting until they're older, and that we can do more to develop the skeleton at that point than at any other time in their lives."
Prognosis for Septic Arthritis
Bramlage discussed a study of synovial (joint) fluid matrix metalloproteinases (MMP, a type of enzyme) in regard to septic arthritis. The study found pro-MMP (MMP precursors) and white blood cell (WBC) counts in synovial fluid of affected joints are good correlates to prognosis (lower MMPs and WBCs equaled better prognosis). Flushing the joint cleans out much of the MMP and WBC content; he noted that even just one flush improved the prognosis.
"The theory is that if you're in doubt about a possible infection, it really points out that you should go ahead and flush," he said. "The WBCs will be back in the joint in hours, but the flush eliminates substrate for destructive enzymes (elements for them to break down, the products of which can worsen inflammation). The MMPs are what are by and large the destructors of bone remodeling and tumor metastasis. Be aggressive with treatment."
Another study he referenced found that when steroids were injected into a joint, any infection response (due to non-sterile site preparation) was delayed for several days by the steroids.
How Hyaluronic Acid Works
A paper published in Equine Veterinary Journal (EVJ) documented the levels of hyaluronic acid (HA) after intravenous (IV) and intra-articular (IA, within the joint) use. The study found that after IV use, serum values return to normal in three hours, while after IA use, joint levels return to control levels after 24 hours.
"We're not totally sure how it works," said Bramlage. "It probably does have some anti-inflammatory activity, but most of it (HA) in the joint sticks to the sides of synovial lining as a lubricant. Sliding occurs between layers of a substance, and this is how HA lubricates. Since it sticks to the sides of joints, you may not sample it accurately from the center of the joint. Clients kind of had the idea that it was like motor oil, but it's much more complicated than that."
Markers of Fracture Predisposition
Bramlage reported on another 2004 study presented at the 2004 British Equine Veterinary Association Conferencce (BEVA) that "is the first indication that there may be a genetic predisposition to fracture." The study identified two different versions of the cartilage oligomeric matrix protein gene--244 and 250 in length--in 86 fracture patients and 172 controls. It found that fracture cases were 2.3 times more likely to have 244/244 allele expression (rather than 244/250), although the mechanics are still unknown. Bramlage commented that the predisposition might be that they can run fast (rather than having more fragile bones).
"Trainers and vets for a long time have thought that some bloodlines produce horses that have 'softer bone' than others," noted Bramlage. "This is the first situation where an investigation has really shown statistically that this might be true. It's nowhere near a pre-purchase situation yet (something tested for prior to purchase of a horse), but potentially it could be."
Another study of bone markers from the 2004 BEVA meeting evaluated markers at the start of training, then followed those horses' histories to measure risk of fracture and fatigue injury of the cannon bone in those 2-year-olds. Researchers then compared fractures and fatigue injury to bone markers to see if there was any correlation.
It found that these markers were no help in predicting fractures, but there were some marker differences in horses that bucked their shins. "Perhaps the pathology of the two diseases is different?" Bramlage commented. "It would be of more help if they could predict fracture. Markers at this point have no use in a pre-purchase scenario."
Tips of the Hat
Madigan and Bramlage recognized several people who made significant contributions to equine health and welfare and veterinary medicine this year.
Representative Bob Goodlatte (R-VA) was very amenable to sitting down with both sides and learning more about the slaughter issue.
Prior to Hurricane Frances in Florida, Jeffrey T. Berk, DVM, a partner in Ocala Equine Hospital in Ocala, Fla., called together the American Veterinary Medical Association's Veterinary Medical Assistance Team and took it upon himself to organize a meeting of area veterinarians.
Leon Scrutchfield, DVM, was one of the first veterinarians to push equine dentistry to a new level, and he is retiring soon. Another veterinarian, Lowell Smalley, DVM, headed up the AAEP Dentistry Committee that raised standards and awareness in veterinary dentistry.
Robert Miller, DVM, of Thousand Oaks, Calif., was recently inducted into the Western Regional Cowboy Hall of Fame.
A general tip of the hat was given to those performing research and striving to improve the lives of horses.
Another EVJ study investigated the effects of palmar digital nerve blocks on (proximal) interphalangeal pastern joint pain in the forelimbs. "[Injections] at two and three centimeters above the cartilages of the foot anesthetized the pastern joint partly or fully," he reported. "But with one centimeter (above the cartilages), only one horse showed analgesia," said Bramlage. "So when anesthetizing the foot only, block low. You will get lots of things blocked if you don't stay right down on the foot cartilages!"
A Washington State study published in Veterinary Surgery evaluated bacterial contamination of an arthrocentesis site before and after four methods of preparation in horses with and without evidence of skin contamination. The four methods included povidone iodine as a 10-minute scrub, as a five-minute scrub, three 30-second scrubs of the iodophore solution, and a topical application of a commercially available paint-on iodine surgical preparation solution.
Bramlage reported that all methods reduced contamination. There were small decreases in contamination with more scrub time, but they were not significant. He remarked that on short-haired horses, you don't really have to clip the area in question, but you do have to get the dirt off first. "The trouble with hair is that there's dirt resident in it," he added.
Shock Wave Therapy
Good short-term response to focused shock wave therapy (SWT) was seen in seven of 14 horses treated for various causes of back pain, Bramlage reported from a study presented at BEVA. However, long-term improvement was only seen in horses that had soft tissue injuries (three of 14).
An EVJ study of radial pressure wave therapy (PWT) found that 41% of hindlimb lameness cases and 53% of forelimb lameness cases had returned to work six months after diagnosis and treatment. "Injuries such as proximal suspensory desmitis can be improved with this (shock wave therapy)," Bramlage commented.
Is Your Horse Left- or Right-Hoofed?
Bramlage reported on a study published in the 2004 BEVA Proceedings on lateralization in horses (left and right "handedness"). The study found that about 50% of Thoroughbreds, 52.5% of Standardbreds, and 17.5% of Quarter Horses had a side bias (mostly left leg forward--40.5%, 40%, and 10%, respectively) while grazing, while the rest were ambidextrous. Thoroughbreds were also assessed for nostril bias when sniffing, and the whole population used the right nostril first.
"We've selected Thoroughbreds and Standardbreds for racing in a circle (possibly selecting for lateralization)," he commented.
Word of the Year
"The word for 2005: Prolotherapy," said Bramlage. "It's the newest thing in the human literature for back pain, kind of like an internal blister. It involves repeated injections of irritant solution, such as hypertonic glucose, to reduce pain. There have been two articles published on it this year, and it was recently endorsed by former Surgeon General Everett Koop, who said it helped his back. This made it recently popular, even though it's been around since 1937. It is proposed to be a way to strengthen the ligaments of the back."
Diagnostic Joint Arthroscopy
Another EVJ study looked at 74 slaughter horses to clarify the value of diagnostic joint arthroscopy in assessing fetlock joint damage. The joints were scoped, then opened and scored. The correlation of arthroscopic assessment of cartilage damage with true joint damage was poor due to the limited amount of cartilage that could be seen, Bramlage said. "You might think it looks good, but there's a lot you can't see in the fetlock joint, unlike some other joints."
Bramlage said a Veterinary Surgery paper studying cannon bone failure in Thoroughbred racehorses noted that condylar fractures (those of the rounded joint surface at the end of a bone) originate by progressive worsening of microcracks of subchondral bone (found just under cartilage).
In another 2004 BEVA study, evidence of pre-existing cartilage pathology was found in 73% of 75 horses euthanized for lateral condylar fractures. The authors noted that this finding might be normal for the population, and that further study is needed.
A study published in the American Journal of Veterinary Research found that the risk of suspensory apparatus failure (SAF) in racehorses was doubled with hoof pads or moderate ligamentous suspensory apparatus injury (MLSAI), and long lay-up time also increased risk. The risk of forelimb metacarpal condylar fracture (CDF) increased four-fold with MLSAI.
"Treating moderate suspensory apparatus injury should reduce SAF and CDF in the opposite forelimb was the conclusion of the paper," Bramlage commented. "The paper doesn't really fit what we see clinically, as we don't really see SAF and then CDF. CDF is not an acute injury. Clinically, as a horse starts to get sore in one limb, he shifts weight to the other, so SAF is often a secondary injury. I think we have to entertain the possibility that the sequence of the injury is the other way around. Since condylar fractures are the result of accumulated damage, the horse may be avoiding that limb and injuring the suspensory ligament before the condylar fracture occurs."
Herniation After Castration
An EVJ study of castration in draft colts evaluated the incidence of herniation before and after this procedure. It found that 4.6% of colts experience inguinal or scrotal hernias pre-operatively, and 4.8% had small intestine evisceration (intestinal protrusion) after castration. Of the latter, those seen to eviscerate and were immediately corrected had a 72% survival rate. There was no difference between closed and open castration techniques and the rate of herniation or evisceration. This increased risk in the draft horse likely has to do with the young age of castration common in draft breeds.
More information: www.TheHorse.com/ViewArticle.aspx?id=5406.
BY STEPHANIE L. CHURCH AND CHRISTY WEST
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