Pelvic fractures

Latest Veterinary Research

Pelvic fractures can occur as a result of a traumatic incident such as a kick or a fall, or as a result of repetitive loading during exercise (when they are most commonly incomplete “stress” fractures) (15) (33). If pelvic stress fractures are not detected, they can lead to complete fractures of the pelvis, which unfortunately are frequently fatal.

Pelvic fractures are primarily a problem of racehorses (15) and occur in both flat (15) (44) and national hunt horses (13). Stress fractures affecting the pelvis are a common cause of hindlimb lameness and poor performance but can be difficult to detect in the early stages.

The majority of stress fractures occur during training, rather than on a racetrack (15) (14).

Pelvic stress fractures can be progressive (135) and early detection can help prevent progression to fatal fractures.

A close up of the pelvis in the horse (orange labels)

What is a stress fracture?

Bones that are subjected to excessive repetitive loading, with insufficient time (rest) to adapt and remodel are susceptible to stress fracture formation.

Cyclic loading during locomotion (movement) results in bone fatigue at sites of high load, which may progress from minor micro-cracking to incomplete, non-displaced fractures. If undetected, progressive development can result in a complete, displaced fracture, which is more likely to be fatal or result in a decision to euthanase the horse (33).

Stress fractures can consist of multiple sites of fracture on one or both sides of the pelvis but the ilial wing (the largest bone within the pelvis) is a common location of pelvic stress fractures in the racehorse (135).

Modifiable risk factors

Likelihood of pelvic fracture occurrence has been observed to vary between trainers (15), suggesting that some training practices are associated with a higher risk of pelvic fracture than others. It may be that some training regimens do not allow for sufficient skeletal adaptation to withstand the forces placed upon it. Aspects of training that have been investigated include gallop surface type, topography and condition as well as distances worked at different speeds.

Several individual risk variables have been identified such as:

Workload – pelvic fracture risk increases as total distance of cumulative exercise increases. Furthermore, there was a significant increase in risk if cumulative exercise distances were increased over a 30 day period compared to 60 days, indicating the importance of increasing exercise levels gradually (14). It is likely that this is due to the time required for physiological adaption of the horse to increasing work distances.
Surface effects– see our ‘injury risks associated with surface type and going’ for further detail on all injury risks.
Early investigation of subtle lameness – early veterinary attention for horses with subtle lameness may allow stress fractures to be diagnosed more quickly. Early diagnosis would allow removal of horses from training and reduce the likelihood of progression to catastrophic (fatal) failure.

Video 1: Equine Pelvic Ultrasound Technique (UC Davis) – External and rectal scan techniques.

Photograph by GROSSICK RACING

Prognosis and return to function

Risk of fatality from pelvic fractures in racing reportedly ranges between 0%-13% across three small sampled studies (14) (44) (33).

However, there is evidence that a significant proportion of pelvic fractures occur in training, thus, further training data would be beneficial to quantify the risk of pelvic fracture to racehorses overall.

Read more – click here to read the THN’s FULL RESEARCH REVIEW which summarises the scientific evidence available:

RESEARCH REVIEW – PELVIC FRACTURES: risk factors, diagnosis and future prognosis.