Shock Waves Ease Navicular Lameness

A case series of 27 horses with navicular syndrome treated by extracorporeal shock wave therapy was reviewed with comparisons of pre- and post-treatment lameness and radiographic scores. Most horses in the study were Quarter Horses and the median duration of lameness was 12 months. Follow-up was obtained at 6 and 12 months after treatment.

The mean lameness grades for the worst limb inside a circle at the trot were 2.5 and 1.6 pre- and post-treatment, respectively.  Most (81 percent) owners reported the lameness had improved post-treatment and unblinded lameness examinations before and after treatment suggested 70 percent of horses improved. Lameness examinations performed with video tape and no knowledge of treatment status only suggested that 56 percent of horses improved. There were no significant changes in radiographic scores pre- and post-treatment.

The authors concluded shock wave therapy should be considered a viable treatment for navicular syndrome in horses. However, they also suggest further studies including objective data such as gait analysis are needed.

—McClure S et al. AAEP 2004; 50: 316-319.

Inflammatory Enzyme Activity in Laminitis

An experimental study was conducted to evaluate the activity of the inflammatory enzymes cyclo-oxygenase (COX)-1 and -2 during the early phases of laminitis. Specimens of laminae were collected from anesthetized horses about 3 hours after laminitis was induced using black walnut extract. Similar samples were collected from normal control horses, and the level of COX-1 and -2 activity (expression of mRNA) was compared between both groups.

Because the samples were taken early in the development of laminitis, no clinical signs of laminitis were seen in either group. COX-2 expression was significantly increased in laminitic horses compared with controls, however COX-1 levels were not different between groups.

Although both are known to be involved in inflammation, the exact roles of COX-1 and COX-2 in the development of laminitis are not fully understood. It is possible that some COX-1 activity may actually be beneficial during the body’s response to inflammation, and new anti-inflammatory medications that selectively target COX-2 activity are available. The results of this study suggest an important role for COX-2 in the development of laminitis. The authors concluded the results support the aggressive use of non-steroidal anti-inflammatory medication in horses at risk for laminitis, particularly those that are selective against COX-2.

—Waguespack RW et al. AJVR, 2004: 65;1724-1729

Risk Factors for Falls In Jump Races

A prospective observational study was used to identify factors associated with the risk of horses falling during hurdle and steeplechase races. Horse, race, track, travel, equipment and behavior information was collected on 2,879 starts from 9 racetracks and comparisons were made between horses that fell and those that did not.

There were 124 falls with 8.9 percent of those horses sustaining an injury and 6.5 percent of those injuries being fatal. In all, 44 percent of fatalities were associated with a fall.  Steeplechase races were higher risk compared to hurdle races. There was considerable variation in risk between tracks.

In steeplechase races, longer travel time to the racetrack, younger horses, novice racers, good and good-to-firm track condition, sunny weather and increasing rainfall in the previous 24 hours were all associated with an increased risk of falling. The results were similar for hurdle races, except that novice hurdle racers were less risky compared to professional racers, rainfall was associated with lower risk and trotting/cantering in the paddock was linked to increased risk.

This study identified modifiable risk factors for falling, most notably travel times to the track and track condition. The results could be used to help improve safety for horses and jockeys alike, and suggest that more research into pre-race behavior may be beneficial.

—Pinchbeck GL et al. EVJ 2004;36:595-601.

Shock Waves And Palmar Digital Nerves

An experimental study was conducted on 6 horses to examine the functional and structural changes in palmar digital nerves following extracorporeal shock wave therapy. A single shock wave treatment was applied to each medial and lateral palmar digital nerve under sedation. Nerve conduction tests were compared between treated and non-treated nerves at intervals of 3, 7 and 35 days following treatment. In addition, following surgical neurectomy, nerve morphology was assessed using electronic microscopy.

Most treated nerves had significantly slower nerve conduction velocities compared with controls on days 3, 7 and 35. Microscopic examinations revealed disruption of the insulating sheath surrounding larger nerves but no damage to the nerve cells themselves.

The changes observed could explain the pain relieving effects seen with shock wave therapy. The authors concluded additional long-term studies following multiple treatments are needed and recommend caution when treating horses with pre-existing conditions that could develop into catastrophic injuries when exercised after treatment.

—Bolt DM et al. AJVR 2004; 65: 1714-1718