Joint Authorities--Orthopedic State of the Art (BEVA 2007)
You and I both know it: we rarely have time to go through the mail and read every article in every magazine that we receive. Our veterinarians encounter the same situation along with another snag, in that on top of their normal caseload, full schedule, and regular mail, they often come home to a pile of veterinary journals chock full of studies that might be applicable to their patients. Yet, there aren't enough hours in the day to soak it all in. To combat this problem, two veterinarians compiled the latest on equine orthopedic topics and presented it to their colleagues at the 46th British Equine Veterinary Association Congress, held in Edinburgh, Scotland in September 2007. They fashioned the session after a similar, popular news-focused session held at the American Association of Equine Practitioners' convention annually called the Kester News Hour.
Wayne McIlwraith, BVSc, PhD, FRCVS, DSc, DrMedVet (hc), Dipl. ACVS, Barbara Cox Anthony University Chair and Professor and Director of Orthopaedic Research at Colorado State University, and Michael Schramme, DrMedVet, CertEO, PhD, Dipl. ECVS, associate professor of equine surgery and director of the Equine Orthopedic Research Laboratory at North Carolina State University, were panelists in this session. Some of the points they highlighted follow.
Intra-articular joint treatment McIlwraith reviewed a study (Kristiansen et al., Equine Veterinary Journal, 2007) out of a U.K. equine clinic that showed weekly intraarticular (IA) use of polysulfated glycosaminoglycan (PSGAG, or Adequan) in lameness that is abolished by coffin joint anesthesia responded very favorably. Veterinarians have balked at this method over the years due to work showing there was a risk of joint infection. However, if a trained veterinarian administers the medication according to a specific protocol, it can be safe and very useful.
The study was based on seven years of records including horses veterinarians treated with either PSGAG or methylprednisolone acetate (MPA) in the coffin joint. The scientists also had the owners complete a detailed questionnaire that allowed them to describe the horses' state at least one year after treatment. Of the horses receiving three IA injections of PSGAG eight days apart, 67% had a successful outcome. Horses receiving a single IA injection of MPA as a first treatment, then a series of three IA PSGAG injections if the horse did not improve sufficiently to return to work by four weeks, 46% had a successful outcome.
Dressage horses responded better to the treatments than jumping horses (eventers and show jumpers). Researchers concluded that there was a good rationale for using IA PSGAG to treat lameness that's reduced by 75% or more with coffin joint anesthesia. MPA was inferior in this study, and other work at CSU has shown deleterious effects.
"I've always considered it a better product used intra-articularly," said Schramme, who added he hoped this was the rumblings of an "Adequan revival."
Collateral desmitis of the coffin joint Schramme said until recently this has been "considered the second most common soft tissue injury in the foot, and many of us have had a strong suspicion that we are overdiagnosing the problem" with MRI. He said several studies in 2007 had confirmed his suspicion, including one out of The University of Pennsylvania (Spriet et al., Veterinary Radiology & Ultrasound, 2007) that showed if the horse's foot was placed at a particular angle in the center of an open, low-field MR magnet, structures can line up so that there appears to be an asymmetric signal and therefore an injury or artifact. Scientists were able to mimic this "magic angle artifact" phenomenon. Another group of researchers (Smith et al., 2007) was able to show the same situation with an open, standing MRI. "They concluded that every effort should be made to position the horse standing squarely on all four limbs prior to commencing MRI, and to minimize leaning during image acquisition," said Schramme.
MRI Next, McIlwraith recommended an article published in Clinical Techniques in Equine Practice to veterinarians considering employing MRI in their practices (Werpy, 2007). "This chapter is something for those of you who have questions about high- versus low-field systems," said McIlwraith. "It gives you a good overview of the limitations and the advantages of the two systems."
MRI and distal sesamoidean desmitis Schramme continued, describing a Washington State University study published in Veterinary Radiology & Ultrasound (Sampson et al., 2007) that reviewed MRI information on 27 horses with lameness localized to the digit or fetlock region. The researchers wanted to review the MRI findings and determine long-term prognosis for horses with a diagnosis of desmitis of the oblique and/or straight distal sesamoidean ligament.
The horses were anesthetized and in lateral recumbency during the scans. Horses were diagnosed on the basis of an asymmetric signal, "hyperintensity being the hallmark of injury," said McIlwraith. The horses were treated with six months of rest: two months walking, two months jogging, and two months of light riding. Researchers injected MPA and HA into the digital flexor tendons of 22 of the horses to decrease inflammation of the injured ligaments before starting the rest and rehabilitation program. They split the ligaments of two horses: one in the oblique distal sesamoidean ligament, and one in the straight distal sesamoidean ligament.
"The slight weakness of this paper was they did not perform ultrasound on the majority of these cases at the university," Schramme said. "They relied on ultrasound findings of referring veterinarians. In spite of this, only two of these had ultrasonographic suspicion of injury.
"Desmitis of the distal sesamoidean ligament may be a more common lameness than previously reported, and requires high-field MRI" for diagnosis, McIlwraith concluded, noting the prognosis of this injury is favorable when using the treatment described, since 76% of the horses to successfully resume performance.
Shock wave therapy and healthy tissue McIlwraith described a study (Bosch et al., Equine Veterinary Journal, 2007) that examined the biomechanical composition and metabolic activity of tenocytes (tendon cells) in normal tendons exposed to extracorporeal shock wave therapy (ESWT). The scientists took tendon explants for culturing three hours after applying 600 shocks to the superficial digital flexor tendon in the mid-metacarpal area and at the origin of the suspensory ligament. They also grossly examined the tendon tissue six weeks after application of shock waves.
Results showed the synthesis of glycosaminoglycan (GAG), which forms an important component to connective tissue, was increased within three hours of applying ESWT, but it was decreased after six weeks. Similarly, collagen and GAG degradation was increased at three hours, but decreased at six weeks. The disparity between early and later changes makes conclusions difficult here. But the potential for causing deleterious effects to normal tendon requires further investigation.
Endoscopy and Tendon Lesions He went on to recount a surgery study (Smith et al., Equine Veterinary Journal, 2007) in which veterinarians examined flexor tendon lesions in the navicular bursae of 20 lame horses using endoscopy. The procedure, called navicular bursoscopy, corroborates information gathered from noninvasive imaging modalities, allows the veterinarian to see lesions that might not be visible using other diagnostic methods, provides further information on the structure of lesions, and permits minimally invasive surgical access to these lesions.
The veterinarians used endoscopy to examine 23 bursae in 20 horses. They found tears of the DDFT in all of the horses (22 bursae), and in eight bursae they found cartilage lesions (in one bursa this damage was the only abnormal finding). They used CT scan and low-field MRI to predict tendon lesions in most cases, but neither of these modalities was effective in identifying cartilage damage.
Fifteen of the animals had greater than six month follow-up information: Eleven were sound and nine had returned to their preoperative levels of performance.
The researchers concluded that "the diagnostic information obtained and therapeutic options offered by burscoscopy justify its use in horses with clinical findings localizing lameness to the navicular bursae."
Treating "Kissing Spines" Dorsal spinous processes can impinge upon one another, causing excruciating pain in the horse and resulting lameness. European surgeons approached this condition, called "kissing spines," by performing endoscopic resection using an instrument developed for paraspinal endoscopic laminectomy in human patients (Desbrosse et al., Veterinary Surgery 2007).
Eight of the 10 horses in the study that underwent the procedure returned to their previous level of activity, including full work at eight weeks, and their recoveries were accomplished with excellent cosmetic results. Periosteal reaction developed in two horses.
Platelet-rich plasma use Cornell researchers examined the use of platelet-rich plasma (PRP) in horses with tendon injury, according to Schramme (Schnabel et al., Journal of Orthopedic Research, 2007). "The rationale is that if platelets release considerable amounts of growth factors, you could help with the healing of cartilage, tendons, and ligaments)," he said.
"This study looked at gene expression patterns, DNA, and collagen content of equine tendon explants cultured (in vitro) with whole blood, plasma, and platelet-rich plasma," he continued. Concentrations of TGF-1 and PDGF were higher in PRP-treated tendons, compared to other blood products and bone marrow."
Schramme commented that while all blood products stimulate gene expression, PRP seemed to stimulate the greatest number of genes (collagen types II and III, and COMP), with no concomitant (accompanying) increase in molecules of harmful enzymes. "These findings support in vivo (in the live animal) investigation of 100% PRP as an autogenous (generated in the body), patient-side treatment for tendonitis," he noted. "It's another treatment that we need to carefully evaluate in vivo as it continues to come along."
McIlwraith continued on the topic, discussing a pilot study of four horses with osteoarthritis (Carmona et al., Journal of Equine Veterinary Science, 2007) that showed IA treatment with PRP concentrate was safe. "The question is, there were no controls here," he said. "It has no side effects, and is being used in vivo."
An additional abstract (Waselau et al., ECVS, 2007) reported that PRP can be safely used in horses and "might represent a novel valuable alternative and/or adjunctive treatment option in horses with mid-body suspensory ligament desmitis," said McIlwraith. "Again, there were no negative side effects, but we certainly need more control data."
Degenerative suspensory ligament desmitis Degenerative suspensory ligament desmitis (DSLD) is an increasing cause of incurable lameness in Peruvian Pasos and other breeds, said Schramme. He presented information on a University of Georgia study that has been published online (BMC Veterinary Research, 2006). The researchers examined 28 DSLD-affected horses that were donated to the university--22 Peruvian Pasos, six Warmbloods, and eight controls of a different breed--and they looked for tissue changes in these horses.
"They found excessive amounts of proteoglycans in the suspensory ligament, superficial digital flexor tendon, and the patellar and nuchal ligaments (which lies in the neck near the withers)," said Schramme. "This study demonstrates that DSLD is a systemic disorder of all connective tissues and should be more appropriately named.
"They have set up a service where they encourage you to take a biopsy of the nuchal ligament," said Schramme. "Send it to their lab and they will get a response to you at a fairly quick turnaround time. We've used the service several times. It's something that we've used on occasion in that particular scenario, to decide whether to do a neurectomy. If they come back positive, we paint a pretty bleak picture and prognosis." Veterinarians can access the service at www.angelfire.com/bc/curlygait/biopsy.html.
McIlwraith observed, "It's almost like we have a storage disease of proteoglycans," also noting, "we're always behind our human counterparts in (understanding) connective tissue disease. Where does the accumulation of proteoglycans fit in as far as disease goes?"
Prophylactic Adequan McIlwraith moved on to an Oklahoma study (Gary White et al., JEVS, 2007) in which scientists looked at a regimen of intramuscular (IM) Adequan to prevent osteochondrosis in young horses. Seventy-five horses were recruited at 8 weeks of age, and they received 1.1 mg/kg of Adequan two times a week for periods of four weeks, alternating with four-week periods without treatment, until the horses were 1 year old. From age 1, the horses received weekly IM injections. The researchers used case histories on animals treated in the three previous years for OCD as controls.
Of the test group, 14.9% had to eventually be treated for OCD, while in the control group, 29% had to be treated. This was not statistically significant, but "there was a significant reduction in the incidence of surgery for clinically significant joint lesions," said McIlwraith. "The important thing is, is Adequan getting the credit for this? The data this year compared to the three previous years is pretty impressive in the reduction of the need for surgery. It could be prophylactic, or it could be treatment of early lesions."
"PSGAG has the potential to improve the clinical course of osteochondrosis (OC) and OCD," summarized McIlwraith, who added that not all clients can afford surgery, and that 90% of Adequan's market is actually prophylactic use.
A new way to fuse the hocks Sometimes veterinarians find that the best way to solve a joint issue is to fuse the joint, either by ankylosis (the bone fuses to bone on its own naturally or with the help of a chemical process) or by arthrodesis (using hardware via surgery). Fusing part of a painful arthritic joint aims to immobilize the damaged part of the joint and make the horse more comfortable.
Schramme outlined a study that examined achieving ankylosis of a lower joint of the hock (the tarsometatarsal joint; there are six bones in the hock) using either 70% or 95% ethyl alcohol, which is a new type of chemical arthrodesis (Shoemaker et al., American Journal of Veterinary Research, 2006).
Veterinarians treated the hocks of eight healthy, sound mares without radiographic evidence of hock arthritis. Eight of the 16 joints were fused at four months, with significantly more joints fused in the 70% alcohol group, and 15 of the joints fused within a year. Horses had minimal lameness associated with the treatments.
McIlwraith added, "It needs clinical testing, but it certainly produces bone. I think the important question here is what would it be like in the centrodistal joint (a joint closer to the center of the hock), because clinically we can use it there. But certainly people have used it in the tarsometatarsal joint as an alternative and less expensive way to obtain fusion."
IRAP/ACS and Osteoarthritis Schramme described a Colorado State study (Frisbie et al., American Journal of Veterinary Research, 2007) that examined interleukin-1 receptor antagonist protein (IRAP), also called autologous-conditioned serum (ACS)--as a treatment for osteoarthritis. To create IRAP, scientists culture whole blood with glass beads to upregulate interleukin-1 (a mediator of inflammation). The material is put directly back into an arthritic joint in a series of three injections, followed up at monthly intervals with additional doses as needed. The aim of the IRAP, in essence, is to block bad interleukin and allow good interleukin to work in the joint.
In the study, eight horses with experimentally induced osteoarthritis; scientists used the Colorado State model of arthritis for this--were on an ACS treatment regimen, and eight others received a placebo treatment. The veterinarians assessed the horses' lameness and analyzed joint synovial fluid throughout the study, and they examined cartilage and synovial membrane samples at necropsy. They found that there was significant clinical and histological improvement in the horses treated with ACS as compared to the placebo horses.
McIlwraith said the experimentally induced osteoarthritis creates just over a 2 on a lameness scale of 1 to 5, one being the least lame. "This is a relatively low degree of lameness, and that's why we like and use this model," he said. "All other (previous) models were based on a lot more severe lameness than this, which I consider inhumane."
It's important to consider cases carefully before proceeding with ACS treatment, as some cases respond better than others. "We typically use (ACS) in cases that have not responded or cease to respond to hyaluronic acid and triamcinolone," said McIlwraith. "The other indication where we use it is where we have early cartilage disease and we use it as a postoperative treatment."
Avocado and soybean unsaponifiable (ASU) extracts and osteoarthritis The final paper McIlwraith reviewed was one out of his own lab at Colorado State; he and other researchers examined an oral supplement based on soybean and avocado unsaponifiable (ASU) extracts and its effect on horses with experimentally induced osteoarthritis. These extracts are the fraction of oil that does not form soap after hydrolysis.
"There was a significant improvement in the combined score of erosion in the joint and also the synovial membrane hemorrhage score," he said, so the supplement has "some encouraging chondroprotective properties.
"These objective data support the use of ASU extracts as a disease-modifying treatment for management of osteoarthritis in horses," he concluded. While the supplement didn't prove to be a pain inhibitor (lameness wasn't reduced), McIlwraith said there is evidence that the unsaponifiable portion of the supplement will inhibit the effect of a harmful enzyme called interleukin-1 that is produced in arthritic joints.
This was the first time Colorado State's osteoarthritis model was used to test an efficacy of an oral supplement in the live horse (in vivo). In fact, there isn't a lot of research in the equine literature on the efficacy of oral supplements in the live horse; most of the research is done in the laboratory on tissue explants (in vitro). "The in vivo effect might be very different from the in vitro effect," McIlwraith noted, and this type of in vivo research in equine supplements should be encouraged. (Read about this study here.)
About the Author
Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.
POLL: Rehabbing the Injured Horse