Rib fracture in a horse during an endurance race

Abstract

We describe a fatal case, in which a horse suffered a fall and as a consequence, rib fractures. Diagnosis was made postmortem and the horse died without showing clear signs of respiratory dysfunction. The retrospective reports of injuries can be important to reduce these traumatic events and to avoid fatalities.

Accidents and traumatic injuries are common during endurance races, with various outcomes for riders and horses. According to some reports of the American Endurance Ride Conference, 18% of horse fatalities during endurance rides are due to accidents. Accidents are unpredictable and are sometimes associated with the difficulty of the terrain. However, the compilation and retrospective reporting of wounds and injuries occurring during races can be important in helping to reduce these traumatic events and to avoid fatalities.

In the present report, we describe the case of a horse which suffered a fall during an endurance race, and as a consequence, had rib fractures. The horse died 1 d after the race without showing clear clinical signs of respiratory dysfunction; diagnosis was made postmortem.

Case description

An 8-year-old Arabian gelding that had 2 years in competition competed in a race in Northern Spain. The 4 categories of endurance racing set by the International Federation of Equestrian Sports (FEI) to be completed in 1 d are CEI* (40 to 79 km), CEI** (80 to 119 km), CEI*** (120+ km), and CEI**** (160 km). This horse was competing at the CEI** level, covering a distance of 116 km, divided into phases of 40, 28, 20, and 28 km. Fifteen horses started the race and 8 finished; these 8 were considered fit at the last “vet-gate” or veterinary checkpoint. Mean speeds during the ride ranged between 13 km/h and 14.7 km/h. The race course consisted of variable terrain, alternating steep slopes (60% of the course) with stretches of flat tracks. The surface was good, with some sections of asphalt. The weather was cold (from 2°C to 8°C) and it snowed and rained intermittently during the race.

The horse finished the first phase leading the race, with an average speed of 13.7 km/h. In the vet-gate he was found to be fit to continue. In the middle of the second phase, the horse suffered a fall and rolled over in the process. Terrain in the area of the accident was flat and in good condition, although the track was narrow. There was a small puddle in the middle of the track, where the horse that was ahead had a fall. In order to avoid injuring other riders and horses, the horse went off the track and fell while trotting.

The rider decided to continue the race, but reported the accident in the next vet-gate to the president of the ground jury. The horse was considered fit in the vet-gate of the second and third phases presenting normal behavior during exercise, and heart rate recovery times were within the normal limits expected for a trained endurance horse. Additionally, he showed appetite and thirst during the compulsory rest periods after these phases. According to the information provided by the rider, the horse was in good condition and retained a desire to run during the competition.

During the preparation for the last phase of the race, the rider observed some discomfort in the horse when tightening the girth, but no other abnormal clinical signs were found and therefore, the horse continued in the competition. During the last phase, after covering 96 km, the horse showed apathy and 1 km before the end of the race, he wanted to lie down and did not want to go further. The horse was eliminated from the race as he tried to lie down and synchronous diaphragmatic flutter was observed for a few minutes, just before arriving at the vet gate. As a consequence of these clinical signs, the veterinarians sent the horse to the treatment area.

The animal was placed in a trailer and transported to the veterinary treatment area, located 2.5 km away. On arrival, the horse was sitting in the trailer, and again while in the treatment box. While sitting, the horse appeared to be comfortable and after that, he was able to get up without significant difficulty. The veterinarian observed signs compatible with ataxia and weakness. The main differential diagnoses at that time were hypoglycemia, exercise exhaustion, and neurological diseases, associated with metabolic disturbances or with the trauma.

In the treatment area, the owner observed aggressive behavior when he manipulated the sternum and ventral part of the thorax. Immediately after that, the horse showed tachypnea with short breaths for 1 min. Physical examination revealed a heart rate of 50 beats/min, capillary refill time of 2 s, skin turgor of 2 s, and mucous membranes were mildly hyperemic. Intravenous fluid therapy was administered, consisting of 10 L of an IV isotonic electrolyte rehydration solution. Other medications were not administered and the horse clinically improved, he did not try to lie down and the weakness disappeared. Thus, 2 h after fluid therapy, the heart rate decreased to 35 beats/min, and clinical signs compatible with dehydration (capillary refill time < 1 s, mucous membranes appeared pink and wet, and skin turgor was not persistent) and synchronous diaphragmatic flutter had resolved. Because of this clinical improvement, the owner received authorization from the veterinarian to leave the place of competition, but the horse remained. Two hours later, the veterinarian checked the horse and he appeared to be healthy; after that, he remained without veterinary supervision. More clinical signs were not observed by the owners and the horse was eating and drinking properly. The day after the competition, the horse was found dead in the treatment box.

Postmortem examination

A complete postmortem examination was performed 2 d after death. The body was in good condition, because of the low temperatures. Ribs 6, 7, and 8 in the right hemithorax were fractured in their proximal 3rd and the adjacent intercostal muscles were damaged. Hemothorax and pneumothorax were present. The lung parenchyma adjacent to the fractures had traumatic hemorrhagic injury. The ventral half of the diaphragmatic lobe of the right lung contained blood. Blood was also found in the lower respiratory airways, up to the trachea. Other macroscopic abnormalities were not found in the postmortem examination. Urine was collected for a complete analysis and all values were within normal limits.

Discussion

We describe a case of an endurance horse which fell early during a competition and as a consequence, experienced rib fractures. The trauma from the accident remained subclinical until the last phase of the event, when the pain from the fractured ribs, the injury in the intercostal muscles or/and the hemothorax and pneumothorax induced behavioral changes. Based on the sequence of events and timing of development of clinical signs, it is likely that the original injury induced incomplete fractures of the ribs, and subsequent extreme exercise and/or recumbency induced fracture displacement with concomitant pulmonary contusions, hemothorax, and pneumothorax. We surmised that breathing changes could have resulted in respiratory alkalosis, and as a consequence, synchronous diaphragmatic flutter appeared (1,2).

Rib fractures are not common in adult horses, and are usually associated with traumatic events. By contrast, rib fractures appear to be common in equine neonates, particularly involving the ventral regions of the more cranial ribs. These fractures can arise during delivery or from direct trauma (3,4).

The treatment for rib fractures consists of immobilization via surgical stabilization when fractures are displaced and suspected to be inducing trauma to underlying structures such as the heart and pulmonary parenchyma, or more conservatively, with strict stall confinement. Analgesia must also be provided when there is severe pain. If the rib fracture is successfully stabilized, continued damage to the adjacent structures, such as lung, is minimized (4).

In our opinion, postmortem examination should be mandatory for competition-related deaths. The data must be collected and reported for dissemination of knowledge to the veterinary community. More appropriate clinical tests for horses which have suffered accidents during races could assist with early diagnosis, such as a complete musculoskeletal examination after the fall. However, the rules of the FEI do not allow more in-depth clinical examinations of these animals during competition.

In conclusion, the consequences of some traumatic events may be unrecognized during endurance races and can lead to an erroneous diagnosis of exhaustion.