Recognising and understanding soft tissue injuries Flashcards
Tendon injuries in racehorses - epidemiology
- account for >35% of all injures to flat and
National Hunt horses - 53% of injuries during steeplechase races
- 15% of National Hunt horses affected in one
season - 97-99% affect the forelimb
- 75-93% affect the SDFT
Tendon injuries in event horses - epidemiology
- 43% of injuries sustained
– 33% SDFT, 31% suspensory ligament, 17% DDFT
Losses due to soft tissue injury
1 – Days in training
* Injured horses are likely removed
from training reducing revenues for trainers
2 – Presentations to racecourses
* Injured horses don’t race, reducing
entry fees and racecourse finances
3 – Wastage
* Some horses removed from racing
but continuing in other disciplines
* Some horses euthanised due to poor
prognosis
Stress vs strain
- Stress put on a tissue is the pressure per cross-sectional area
– Stress is proportional to the force you add on each end of that structure - Strain is the amount that the structure you’re stressing deforms under each unit of stress
Tendon loading curve
1 - Straightening of tendon crimp
2 - Elastic deformation
3 - Non-elastic deformation
4 - Failure/rupture
What is elastic deformation?
- every bit of energy put into the tendon it will bounce back and give you everything back you put into it
- here we sit in a happy system -> no energy being dissipated, no failure of tendon fibre
What is plastic deformation?
- where you have elongation of a substance and it’s never going to return quite to where you started
- caused some damage to the tissue but is still structurally fairly sound
The tendon loading and unloading curve
- Force strain % curve
- Looking at energy return
- Most of the energy is elastically returned
- Small amount (area between the lines) is transformed to heat
- Important factor for the SDFT, accelerates protein degradation
- Core of SDFT can reach 45oC
Some of the factors affecting structural properties
- crimp
- glycosaminoglycans (GAGs)
- cartilage oligomeric matrix peptide (COMP)
- collagen
Crimp
- Straightens out in the initial phase of tendon loading
- Distributed differently over the cross section of the tendon in older horses
- Reduces with age -> tendons become less elastic -> affects injury rates
- Important in the very early stage of the stress strain curve and in absorbing that early amount of energy
GAGs
- Important components of the extracellular matrix
COMP
- Correlates with elasticity of tendon
- Increased COMP, more elastic
- Reduces with age -> tendons become less elastic -> affects injury rates
Collagen
- Size and number of fibrils changes over time
- Collagen types and distribution can change over time
Is the blood supply to tendons good?
- No it is poor, particularly within sheaths and bursae
- Therefore, poor recruitment of inflammatory cells
Variation of collagen deposition in the DDFT
- In the mid metacarpal region – lots of type 1 collagen
with elastic properties - In the fetlock region – more type 2 collagen which is
resistant to compression - Chondroid metaplasia