Recognising and understanding soft tissue injuries Flashcards
What losses are associated with soft tissue injuries?
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
How are tendons organised?
Type 1 collagen organised in triple helix - into interdigitating fibres into fibrils.
Forms fibres and bundles and the whole tendon structures.
What happens t the lost energy between the loadinga nd unloading of the tendon in the horse?
Lost energy becomes heat - tendons are heated after galloping (up to 45 degrees).
Lots of people cool distal limbs after races.
What factors affect the structural properties of tendons?
Crimp:
Straightens out in the initial phase of tendon loading
Distributed differently over the cross section of the tendon in older horses
Glycosaminoglycans (GAGs)
Important components of the extracellular matrix
Cartilage Oligometric Matrix Peptide (COMP):
Correlates with elasticity of tendon
Increased COMP, more elastic
Collagen:
Size and number of fibrils
Collagen types and distribution
Clinically important
* COMP and crimp reduce with age– tendons become less elastic
* Affects injury rates
* Tendons consist of large amounts of extracellular matrix (ECM) and relatively few cells
* Implications for healing and remodelling
* Blood supply is poor – particularly within sheaths and bursae
* Poor recruitment of inflammatory cells
What 4 tendons are most important?
Superficial digital flexor tendon (SDFT)
Deep digital flexor tendon (DDFT)
Suspensory ligament (SL)
Inferior check ligament (AL-DDFT)
How does the composition of the DDFT and suspensory ligament change along their course?
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
The suspensory ligament is even more varied:
* Evolutionarily the suspensory ligament should be called the interosseous muscle
* The proximal end of the ligament still retains some muscle fibres and some fat – makes ultrasound challenging!
Where do most injuries occur in the SDFT?
The vast majority of SDFT injuries/pathology occur in the mid metacarpal region of the forelimb
(Occasionally hindlimb pathology is seen, and occasionally disease of the branches close to the insertion onto second phalanx)
Where do most injuries occur in the DDFT?
The vast majority of DDFT injuries/pathology occur within the digital flexor tendon sheath, pastern or within the hoof.
(Occasionally seen in the mid-metacarpal region in the forelimb alongside severe check ligament injury)
Where do most injuries occur in the suspensory ligament?
The majority of SL injuries/pathology occur at the proximal origin or at the branches of insertion onto the proximal sesamoid bones.
Both forelimb (acute lameness) and hindlimb (gradual onset lameness)
(Occasionally lesions in the suspensory body are seen but rarely as solitary lesions)
Where do most injuries occur in the inferior check ligament?
Check ligament injuries are easily palpated in the proximal third of the forelimb metacarpus, usually larger on the lateral side.
(Hind limb injuries are VERY rare, and some horses don’t have a hindlimb check ligament at all!)
Are most tendons injuries acute traumatic incidents or chronic?
Some soft tissue injuries are true acute traumatic incidents
Interference/overreach injuries:
* Horses at speed can strike a loaded forelimb with a rapidly protracting hind limb leading to acute damage of a previously normal soft tissue
* Often skin lacerations are seen alongside
However, this isn’t the case for most…
Microdamage precedes acute injury in most cases!
Increasing age, working in non-elastic region of loading curve, repetitive loading, poor reparative and adaptive processes in tendon tissue, matrix degeneration, reduction in crimp, reduction in comp, increases in type 2 and 3 collagen, poor vascularity, tendon heating…………….
Can we prevent tendon injuries?
Training tendons
* Neonates have high capacity for adaptation and low injury risk - training window exists
* Adults have inexistent capacity for adaptation and high injury risk so training will only degenerate the tendons.
- early conditioning is important
Competitive horses
* An established horse should not be routinely trained at or above the expectations of the horse during competition
* You cannot train adult soft tissues, only accelerate microdamage!
* Must be balanced with the aerobic fitness of the horse, and psychological training of horse and rider.
Boots
- Solid boots reduce risk of direct over reaching trauma
- BUT – consider the implications these might have for the physiological heating effect!!
Track surfaces
- Consider material surface, moisture content, changes in composition during a race, differences between training and racing surfaces
What clinical signs and pathology are associated with the different stages of SDFT injuries?
- An easy diagnosis by palpation/visual inspection
- Characteristic “palmar bow” seen to the profile of the tendon
- Heat, pain, swelling, resentment of palpation
Inflammatory phase - Days
Clinical signs
* Lameness
* Pain on palpation
* Heat
* Swelling
Pathology
* Haemorrhage
* Inflammation
* neutrophils
* macrophages andmonocytes
* increased blood flow
* edema
* proteolytic enzymes
Reparative/proliferative phase - Weeks
Clinical signs
* Reduction or absenceof lameness
* Resolution of signs ofinflammation
* Tendon still palpablyenlarged and soft
* Signs of re-injury ifexercised too early
Pathology
* Angiogenesis
* Fibroplasia
* ++ fibroblasts
* collagen III
* small collagen fibrilsformed
Remodeling/maturation phase - Months
Clinical signs
* Tendon size decreases
* Tendon less pliable
* Reduced fetlock extension
* Contractures
Pathology
* Collagen transformation fromIII to I
* Cross-linking
* Thicker collagen fibrils
What part of the tendon is under most stress following an injury?
Just above and just below injury
Most likely places for re-injury
