the science of horsemanship - working with bone to prevent injury in racehorses
DESCRIPTION
Accompanying slides for Professor Whitton's lecture. Listen to the lecture at: https://soundcloud.com/fvasunimelb/science-of-horsemanshipDr Chris Whitton is the head of the University of Melbourne’s Equine Centre and Associate Professor of Equine Medicine and Surgery. Dr Whitton coordinates the equine scintigraphy service and works as a specialist equine surgeon in the hospital. He has lectured and published extensively on lameness matters. His current research interests are in prevention and diagnosis of injury in performance horses.TRANSCRIPT
Chris Whitton BVSc FACVSc PhD
The Science of Horsemanship Working with bone to prevent injury in racehorses
Research team
• Collaborators ‒ Prof Eleanor Mackie, University of Melbourne ‒ Prof Ego Seeman, Austin Hospital ‒ Prof Marcus Pandy, University of Melbourne ‒ Prof Peter Lee, University of Melbourne ‒ Dr Simon Harrison, CSIRO, Victoria ‒ Prof Chris Kawcak, Colorado State University ‒ Prof Sue Stover, University of California, Davis
• Funding ‒ RIRDC ‒ Racing Victoria ‒ Victorian Government
Research team
• Postdocs and postgraduate students ‒ Dr Michiko Mirams ‒ Gareth Trope ‒ Dr Ebi Bani Hassan ‒ Fatemeh Malikipour ‒ Sandra Martig ‒ Josie Holmes ‒ Babatunde Awodele ‒ Amy Williamson ‒ Megan Thomas
Racehorse injury
• What’s the problem? • How injury occurs
‒ Bone fatigue ‒ Bone adaptation and
repair • Injury prevention
Injury rates
• Victoria flat racing ‒ 1 death/2272
starts ‒ 69% deaths
due to limb injuries
‒ 92% due to bone fatigue
Injury rates
Prevalence • Joint surface lesions
‒ Hong Kong • 70-80%
‒ Victoria • Forelimbs 66% • Hindlimbs 58%
Racing injuries
Bone fatigue • Injuries specific for racehorses • Accumulation of high speed exercise a risk factor • Fractures occur spontaneously • Pre-existing pathology observed • Microcracks identified at predeliction sites
Flat racing
Risk of fatality • Longer career duration
• Greater number of races in career
• Greater number of races in last 30d
• Started 1-14 days prior
Accumulation of damage over time
Rapid accumulation of damage
Flat racing
Risk of joint surface injury • Total lifetime races
• Multiple racing seasons
• Shorter time between races
• Shorter time since last race
Accumulation of damage over time Rapid accumulation of damage
Fatigue injuries
Consequences • Fatalities • Jockey injuries • Premature retirement • Poor performance
Fatigue injuries
Jockey injuries
Conclusions: Prevention of the most common catastrophic injuries and conditions of the racehorse, e.g. fetlock injuries, may be the most effective at decreasing rates of falls and injuries to jockeys during racing.
Results: Jockey falls occurred in 24% of TB race-related horse fatalities, and jockey injury occurred in 64% of falls.
Fatigue injuries
Consequences • Bone fatigue in joints
‒ Catastrophic failure ‒ Joint surface failure
Fatigue injuries
Consequences • Bone fatigue in joints
‒ Catastrophic failure ‒ Joint surface failure
Fatigue injuries
Consequences • Bone fatigue in joints
‒ Catastrophic failure ‒ Joint surface failure
Fatigue injuries
Consequences • Bone fatigue in joints
‒ Catastrophic failure ‒ Joint surface failure
Fatigue injuries
Consequences • Bone fatigue in joints
‒ Catastrophic failure ‒ Joint surface failure
Fatigue injuries
Poor performance • Horses with bone injury identified on bone scan
‒ Performance inferior to age matched controls
Bone fatigue
Prevalence • Microfractures
‒ 46/48 horses had microfractures in fetlock
‒ Both 2-year-olds resting from training
Bone fatigue
Prevalence • Microfractures
‒ Increase with career duration
‒ Increase with training duration
Bone fatigue
Fatigue behaviour • Gradual degrading of mechanical properties due to repeated loading
‒ Molecular debonding ‒ Microcracks ‒ Complete failure
0.20
0.40
0.60
0.80
1.00
0.00 0.20 0.40 0.60 0.80 1.00
n/nf
En/Emax
Bone response
Evolution • Minimum amount of bone to get the job done • Bone
‒ Heavy ‒ Requires energy
Bone response
Adapt • Net increase or decrease in bone volume
Repair • Removal and replacement of bone • No net change in bone volume
Adaptation
Adaptation • Greater risk of fracture (Parkin et al. 2005)
‒ Horses that do no gallop work prior to racing ‒ Horses in their first year of racing
Bone response
Repair • Normal process • Remodelling
– Resorption and deposition resulting in replacement of bone
Repair
Remodelling • Replacement of bone repairs fatigue damage • Remodelling inhibited when bone subjected to high repeated load
Bone injury
Subchondral bone • Resting horse
‒ Constantly replacing bone ‒ Repair increased in response to damage
Time
Damage
Repair
Bone injury
Subchondral bone • Galloping horse
‒ Damage accumulating ‒ Repair reduced
Time
Repair
Damage
Bone injury High load environment
Repair inhibited
Fatigue accumulates Failure
Bone replaced
Rest
Resorption
Prevention
Why? • Early detection challenging • Many injuries unrepairable • Avoids prolonged rehabilitation • Low grade injuries impair performance
Fatigue management
Inspection • Prerace veterinary examination
– Hong Kong - 90% of fatalities - no abnormalities
Prevention
Military recruits (Finestone & Milgrom 2008)
Incidence 31% in 1983
Incidence 10% in 2003
Modifications
Prevention
Military recruits • Reduce number of cycles of load
‒ Reduced stress fractures by more than half
‒ Did not impair performance
Horsemanship
Working with bone • Bone is a dynamic tissue • Facilitate and maximise adaptation • Allow bone repair
Working with bone
Adaptation • When first commencing training • When returning to training from a rest period
Prevention
Maximise adaptation • Humans
‒ Greatest potential is prior to puberty (Kannus et al. 1995)
‒ Benefits persist through adulthood (Warden et al. 2007)
• Horses ‒ Longer career and more starts
with younger age at 1st start (Bailey et al. 1999, Velie et al. 2012)
Prevention
Maximising adaptation • Most responsive prior to skeletal maturity
‒ Distal MC adaptation with 8 weeks of canter (Boyde & Firth 2005)
‒ When increasing speed reduce distance (Nunamaker 1996)
Prevention
Adaptation • Potential to develop highly porous bone
‒ Horse rested for greater than 10-14 days
‒ Horses in training
2 weeks rest
Full work
Repair
Where we go wrong • Inhibit remodelling too much • Train for too long • Rest periods too short
Prevention
Bone replacement • Duration of training
– Less than 20 weeks • Duration of rest
periods ‒ Benefit maximised in
first 10 weeks
Future
Reducing injuries • Monitor injury rates • Educate the industry
‒ Continuing education mandatory • Invest in research
‒ More work on bone fatigue ‒ Define a safe level of training ‒ What affects loads in joints ‒ How to maximise bone adaptation and repair
Horsemanship
• A large proportion of limb injuries are due to bone fatigue
‒ Bone fatigue is preventable
‒ Every injury is a failure
Horsemanship
• Bone can adapt and repair
‒ Understanding bone better • Fewer injuries horses
and jockeys • Better performance
Horsemanship
• Minimum amount of work for optimum fitness • Maximise adaptation to high speed • Allow adequate time for bone repair