New Research Limb Fractures

New research into greyhound limb fractures in WA has been published risk factors revealed.

New research reveals risk factors for hock injuries - https://onlinelibrary.wiley.com/doi/full/10.1111/avj.13377#support-information-section

Racing Wagering Western Australia in conjunction with Massey University, has produced a new research paper into risk factors for limb fractures in racing greyhounds. The following is a summary of their findings, which GRNZ is considering in the refinement of our own risk mitigation strategies.

Fracture Incidence from analysis of Western Australia (WA) data

• The overall incidence rate (IR) of race day fractures from the reserach period (2017-2023) was 3.3 fractures per 1000 starts, with the majority of fractures (97.1%) occurring in the limbs.
• Fractures represented 8.9% of the total findings from veterinary examinations on race day.
• The right hindlimb was the most common fracture site (57.6% of all fractures), with 93% of these in the right hock.
• WA had an incidence rate (IR) of 1.0 fractures per 1000 starts in the forelimb compared to 2.2 per 1000 starts in the hindlimb.

Risk Factors for Forelimb Fractures:
It is proposed that forelimb fractures were likely associated with collisions or interference during races, and they were more common in lower-grade races (maiden to 3 wins) where greyhounds are younger and likely less experienced. Ensuring young greyhounds have opportunities to trial in company and complete their QTs is important in preparing them for racing with some experience.
Greyhounds that had an injury in their previous race were 2.3 times more likely to sustain a forelimb fracture, indicating the importance of previous injuries as a risk factor for bone fractures. GRNZ's Safe Return to Racing Policy goes a long way to ensuring that the risks of previous injuries are mitigated.
Tracks with smaller turn radii had an increased risk of forelimb fractures, it is suggested by the authors that this is due to higher loading and torsional forces on the limbs during turns. New Zealand has three tracks with the tightest turn radii (Manukau, Addington and Hatrick) however, the introduction of PBD racing has significantly reduced the incidence of falls and fractures by reducing collisions.


Risk Factors for Hock Fractures:
Age: Older greyhounds (over 30 months) were at higher risk of hock fractures the authors conclude that this is likely due to cyclic bone fatigue and the accumulation of microdamage over time (this microdamage likely causes stress fractures to occur).
Days between races: Greyhounds that had not raced in the previous 15 days were at a greater risk of hock fractures compared to those racing weekly, which might be due to bone remodelling, which begins during rest periods, making the bone more porous and susceptible to fracture when racing resumes. This is especially true when racing resumes at a high frequency (2-5 days between races) that may overwhelm bone repair processes and adaptive remodelling.
Seasonal Effect: Hock fractures were more common in the summer, likely due to firmer track conditions (on home training tracks) caused by higher temperatures and less rainfall. This could affect track moisture content (noted to be poor during summer in a recent review in WA) and, therefore, increase injury risk. GRNZ has implemented a world-class track preparation and maintenance program with state of the art technology assisting in measuring water content and consistency of track surfaces prior to, and during, every race meeting to ensure that surfaces are presented for racing in the safest condition.


Effect of Race Tracks:
Differences between race tracks in WA (e.g., Track B having a lower fracture risk) suggest that track design and configuration, such as track circumference and surface quality, play a significant role in the risk of both forelimb and tarsal fractures. Track A and Track C had higher fracture risks, likely due to smaller turn radius and greater forces applied during the race.


Fracture Fatalities and Injury Recovery Schemes: (RWWA's RtR)
The study recorded 137 fatal fractures, with an IR of 0.7 per 1000 starts, but there was a significant reduction in fatal fractures after the introduction of the Greyhound Injury Full Recovery Scheme in 2019. The fatal fracture rate dropped from 1.5 per 1000 starts (2017-2018) to 0.4 per 1000 starts (2020-2023), as the scheme provided funding for injury recovery (which were previously cost prohibitive for the owner/trainer) decreasing euthanasia after severe injuries. GRNZ's RtR Policy covers the costs of racing injuries and supports full rehabilitation and recovery from injuries so that greyhounds can be successfully rehomed.


Differences in Fracture Risk by Anatomical Location:
Fracture risks differ between the forelimb and hock, with forelimb fractures more likely due to trauma from race incidents (collisions and falls), and hock fractures associated with repetitive stress and cyclic loading during high-speed running, especially on the trailing limb (right hindlimb) during turns. As the causation of these injuries differs, it makes sense to analyse these separately and design interventions which target these injuries specifically.


Limitations and Recommendations:
The study did not include the effects of trainer management or husbandry (nutrition, rearing, training techniques), which could also affect fracture risk. The authors suggest further research into these aspects, and track conditions and differences in track surface preparation across different locations. GRNZ has recently sent a survey to trainers which begins to examine aspects of this. Previous studies of training in New Zealand have highlighted this as an important area of focus.

The study highlights the need for jurisdiction-specific mitigation strategies to reduce fracture risks, especially considering race scheduling, track design, and maintaining race fitness to prevent cyclic bone fatigue.

In response to this paper, GRNZ's injury reduction taskforce will consider the evidence presented and further develop our injury mitigation strategy, in collaboration with the Serious iNjury Review pnale and GRNZ's ANimal Helath and Wel;fare Committee to ensure that Greyhound Racing New Zealand can continue to leaders in injury prevention.

Further information regarding bone remodelling and safe exercise practices will be included in our final Best Practice Guidelines under the Safe Return to Racing Policy.