Lameness Diagnosis via Head and Pelvis Movement

"I used to think I knew how to evaluate a horse's movement for lameness, until I started to look more carefully. Two highly experienced practitioners can evaluate a lame horse and come up with different (lame) legs," said Kevin Keegan, DVM, MS, Dipl. ACVS, associate professor of veterinary medicine and surgery at the University of Missouri. He discussed conclusions he and colleagues noted about interpreting lameness via head and pelvic movement using observations of more than 100 horses evaluated on a treadmill with computer-assisted gait analysis and video.

Keegan said most equine practitioners use head movement to determine forelimb lameness and pelvis movement to clarify hind limb lameness. He added that multiple lamenesses can certainly complicate the issue.

Keegan showed a video of a normal horse trotting on a treadmill with a graphic evaluation of his head position (seen head-on). His perfectly consistent wave pattern of head up and down movement contrasted with a video of a lame horse (one forelimb) that showed less downward movement of the head only and no change in upward movement. Another lame horse (one forelimb) only had more upward head movement when pushing off of the lame limb.

Similar principles apply when evaluating hind limb lameness, Keegan said. Traditionally, veterinarians watch horses move away from them to look for a "hip hike," in which the sore limb is carried higher to identify the lame leg. Rather, he prefers to look at the entire vertical movement of the pelvis when left and right hind limbs land and push off. "Look at the pelvis like it's a big head," he said.

"We've had hundreds of horses on the treadmill; all (hind limb) lame horses had asymmetrical movement of the pelvis (comparing vertical movement during right and left hind limb landings), regardless of pelvic tilt," he explained. "You see symmetrical movement of the pelvis in a sound horse, even if the pelvis is rotated to one side, because the vertical movement of the pelvis is symmetrical. The most sensitive measurement of lameness is the vertical movement of the head and pelvis. Stride length and other characteristics are more variable and can give you false negatives."

Keegan offered several observations of head and pelvis carriage changes with forelimb, hindlimb, and compensatory lameness. (These can be found online at the address below.)

"A more objective description of the head and pelvic movements seen during lameness will assist equine practitioners in their clinical lameness evaluations," he said.

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Silicone to Lube Joints?

"We had heard several anecdotal reports of intra-articular administration of liquid silicone being used as a lubricant in equine joints (to treat osteoarthritis)," began Daniel Burba, DVM, Dipl. ACVS, professor of equine surgery at Louisiana State University (LSU). Burba noted that only one study, published in 1967, has reported the effects of liquid silicone in equine joints.

"Silicone has been used in Standardbred racehorses in conjunction with corticosteroids to treat refractory degenerative joint disease," he noted.

Burba and colleagues studied the effects of medical grade sterile silicone injected into one knee in eight horses that were free of middle carpal joint disease. The four geldings and four mares were five to 10 years old and were all sound. The opposite knee on each horse was injected with saline as a control.

The results? Not only did silicone not help--it hurt. By eight hours post-injection, all eight silicone-treated limbs were sore, and after six weeks, five of the eight were still lame. One saline-treated limb was lame from eight to 24 hours. Joint circumference in silicone-treated knees significantly increased from eight hours to two weeks post-injection due to effusion. Joint effusion was present in four silicone-treated knees and one untreated knee after six weeks. Changes in synovial fluid and membranes of treated knees were seen.

Burba noted, "The articular cartilage was essentially normal. Nothing indicated erosion of cartilage." The silicone seemed to have dissipated out of the joint without generating significant chronic inflammation, which was interesting since the treated joints still exhibited effusion six weeks post-injection. The effusion might have persisted from the initial inflammation that the silicone created, he noted.

"Administration of silicone resulted in synovitis, but a single administration of silicone polymer had no apparent effects on articular cartilage within six weeks of administration," Burba stated. "However, clinical signs of joint disease (effusion, lameness) persisted.

"Because of the degree of clinically apparent synovitis, liquid silicone is not recommended for intra-articular use in normal joints in the horse," the authors concluded. "However, results may differ in osteoarthritic joints."

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Hock Injections

The hock (tarsus) is a complex collection of joints. Identifying and treating lameness in one or more of those joints can be challenging. Alberto Serena, DMV, MRCVS, of Auburn University, and colleagues have found that injecting medication into one joint can treat an adjacent joint.

This study showed that when 80 mg of methylprednisolone acetate (MPA) is injected into the tarso-metatarsal (TMT) joint, a therapeutic concentration of its ester, methylprednisolone (MP), will diffuse into the distal intertarsal (DIT) joint. These are the two lower hock joints that often develop osteoarthritis.

There were two phases of the study; in the first, MPA was injected into one TMT joint in each of seven sound horses. Serena reported that the concentration of MP in the DIT joint was highest six hours after injection of the TMT joint, but it was evident after a half-hour and dropped quickly to zero concentration by 12 hours.

In the second phase, nine horses received injections of MPA into the left TMT, with MP measured in all DIT joints at six hours.

"Treating horses for osteoarthritis of the lower two hock joints can be accomplished by injecting the TMT joint alone," he concluded. "Administering a corticosteroid into the TMT joint alone is safer, easier, and less time-consuming than injecting MPA into both joints."

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Sacroiliac Pain

Kevin Haussler, DVM, DC, PhD, lecturer in anatomy in the department of biomedical sciences, college of veterinary medicine at Cornell University, succinctly summed up the perplexing issue of diagnosing and treating sacroiliac pain when he said: "I've never been so sure about what I do not know, and I have never been so unsure about what I do know."

It was quite apparent that many other veterinarians felt the same way because they filled the huge room to overflow.

Other presenters on sacroiliac pain were Sue Dyson, VetMB, PhD, FRCVS, of the Centre for Equine Studies, Newmarket, England, and Emmanuel Engeli, Vet. Dipl ACVS, ECVS, of Switzerland.

The sacroiliac joint region continues to be an area of confusion for many practitioners because of its deep location and unique anatomical features, Haussler said. The sacroiliac joint, he explained, is a synovial articulation located at the junction between the ventral wing of the ilium and the dorsal wing of the sacrum (from the point of the croup downward).

The sacroiliac joint, Haussler said, "functions as the pelvic attachment to the axial skeleton, providing support during the weight bearing and helping transfer propulsive forces of the hind limb to the vertebral column." Problems that occur in the sacroiliac joint region, he noted, include osteoarthritis, ilial wing stress fractures, tuber sacrale asymmetry, desmitis (ligament inflammation), and muscle strain.

Haussler said the use of ultrasound and nuclear scintigraphy "have provided new insights into documenting sacroiliac joint pathology. Unfortunately, there continues to be limited understanding and research into the pathophysiology of specific sacroiliac joint injuries."

Dyson reported on a study involving two groups of horses in England. The majority of the horses involved, she said, had a history of reduced performance or unwillingness to work. The diagnosis of sacroiliac joint disease was made after other causes of hind limb lameness had been excluded.

"Complaints included lack of hind limb power, deterioration of quality of movement, change in behavior, reluctance to work on the bit, difficulty in lateral movements, changing legs behind in canter, failure to perform correct flying changes, or refusal to jump," she said. "Some horses had also become awkward to shoe the hind limbs. The clinical duration of clinical signs ranged from one month to more than one year; however, many riders thought retrospectively that the horse had not been right for about two years or was always inclined to be stiff in the back. In many horses, there had been an insidious onset and progression of clinical signs.

"To an untrained observer, many of the horses appeared clinically normal and had been training and competing up until clinical investigation, but with reduced performance," said Dyson. "A second group of horses had a sudden onset of bucking behavior when ridden, tending to buck and kick out simultaneously and sometimes repeatedly to one side."

Most of the horses in the study were used for either dressage or show jumping, with some used for eventing and lower-level competition or show jumping.

When examined in hand on a hard surface, Dyson said, the most common feature among the study horses with perceived sacroiliac problems was reduced hind limb impulsion. "Some horses," she said, "had a rolling hind limb gait, some moved exceptionally wide behind, others moved close, and a few plaited. Many horses had more than one gait abnormality. Stiffness and poor hind limb impulsion were common features on the longe. A few horses tended to break to canter rather than increase hind limb impulsion, whereas others showed a poor-quality canter. Clinical signs were invariably worse when the horse was ridden and sometimes only apparent under these conditions. In some horses, the deterioration in gait when the horse was ridden was profound and dramatic.

"Some of these horses," she added, "were also extremely reluctant to go forward. In less severely affected horses, kicking behavior only became evident when the horse was asked to collect and work with increased hind limb engagement."

A part of the study involved injecting the sacroiliac joint of affected horses with an analgesic, then determining response. The result surprised many of the researchers because of the dramatic effect.

She said: "Marked improvement in gait was observed in many horses and highlighted the degree of discomfort that the horse had been suffering, despite relatively subtle clinical signs in some horses before injection. Horses generally moved much more freely and willingly and with increased animation. There was improved hind limb impulsion and a change in balance because of increased engagement of the hind limbs and subsequent lightening of the forehand. The horses tended to have a more consistent contact with the bit. There was a marked reduction in back stiffness. In several horses that had previously refused to lift either hind limb from the ground, both hind limbs could be lifted.

"Horses that bucked or kicked out," Dyson said, "usually responded dramatically by almost complete cessation of this behavior and marked increase in willingness to move forward."

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Shock Wave to Treat Navicular

Scott McClure, DVM, PhD, an assistant professor in the department of veterinary clinical sciences at Iowa State University, discussed a study evaluating extracorporeal shock wave therapy (ESWT) in treating 32 horses with navicular syndrome. Horses were treated one time with 2,000 shock wave pulses under general anesthesia in lateral recumbency (laying on their sides).

Part of the challenge of treating this area with ESWT is, "To do this, you have to be able to get the shock wave (through the thick tissues of the foot) to the navicular bone, so you do two approaches, through the heel bulbs and the frog," explained McClure. "Pare them down the evening before the treatment, soak the foot, and come back and freshen the edges to get the shock in the foot."

After treatment, the horses were discharged and owners were instructed to maintain the horses' current shoeing regimens and add no additional treatment. Bute was given to the horses for one week, and they were given a week of stall rest followed by a week of hand walking.

An unmasked evaluation (meaning the veterinarian had performed the treatment and was familiar with the cases) was done at six months post-treatment. Client perception was gauged at six and 12 months post-treatment, masked radiograph evaluations were completed (the radiologist was not familiar with the cases), and masked veterinary evaluations were performed via videotape (reviewers were not associated with the study and were unfamiliar with the cases).

In the unmasked veterinary evaluation, 27 of the 32 horses (84%) were available for follow-up. Of those 27 horses, 22 (81%) had improved according to evaluation as they trotted in-hand in a straight line on a hard surface. When trotted in a circle, 19 of the 27 (70%) had improved. The decrease in lameness was statistically significant.

The clients' evaluations (on the 27 horses) at six months post-treatment showed that 22 (81%) had improved, four (15%) remained the same, and one (4%) got worse. At 12 months post-treatment, 16 horses were available for follow-up, and none were reported to have increased lameness associated with navicular syndrome.

In the masked veterinary evaluation, "We had videotapes of the (32) horses pre-treatment and 16 horses six months post-treatment," said McClure. "They were randomly mixed and evaluated by three equine veterinarians (not associated with the study)."

In the 16 horses, the duration of the navicular syndrome-associated lameness prior to presentation to McClure was anywhere from two weeks to three years. In-hand videotape evaluations at six months post-treatment showed that nine of 16 improved (56%), two had no change (8%), and five had progression of the disease. Eleven of the 16 horses (69%) had returned to their intended use by the six month follow-up.

Radiographs were looked at blindly six months post-treatment and scored. McClure said there were no significant changes in the radiographic scores between pre-treatment and six months post-treatment evaluations.

"So you ask yourself why it would work," said McClure. "Is ischemic necrosis (cell death caused by oxygen deprivation) a component? From things that we're learning every day, it may well be. We know there's some neurovascularization following ESWT (regeneration of blood supply in tissues). There are a lot more capillaries in shock wave therapy-treated tendons than control tendons.

"The decreased lameness in these horses is encouraging because many of these horses had been chronically lame and most had been unresponsive to conventional treatments," McClure added. He suggested that to make the study more objective and exact, gait analysis and controls could be incorporated into the study. "While it is possible that there could be spontaneous improvement in some horses, the duration and severity of the disease in these horses makes it unlikely."

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