Equine Tendon and Ligament Disorders Flashcards
What is the difference between a tendon and a ligament?
TENDON = muscle to bone
LIGAMENT = bone to bone
What is the predominant anatomic makeup of tendons and ligaments? What are paratenons?
Type 1 collagen –> grouped into fascicles
elastic covering surrounding tendons to decrease friction
How are tendons able to elongate?
- fascicles elide next to each other
- fascicles have crimp - waveform seen in relaxation
What is the most common cause of tendonitis/desmitis? At what point does this happen?
overstrain or percutaneous trauma
when tendons are extended >10-12% of their length –> at gallop, horses’ tendons can stretch 12-16%
What is the stress-strain curve?
more stress causes deformation, stretch, and strain on tendions, leading to microtrauma and eventual failure (rupture)
Where are injuries in tendons/ligaments most commonly found? Why?
core lesion at the center of the tendon
little blood supply at the center + tendons stretch at the center first –> hypo/anechoic hematoma seen
What is tendon/ligament healing like? What does this result in?
slow and inadequate due to hypoxic environment
increased risk of re-injury –> can’t get back to same strength
What is the ideal environment for tendon and ligament healing?
linear arrangement of predominately small, Type 1 collagen fibrils with strong proteoglycan content
What are 3 historical clues for tendonitis/desmitis diagnosis?
- running/playing hard
- just in hard work with no incident
- long toe, low heel, deep footing = increased stress on palmar/plantar aspect
What are the 2 most common clinical signs associated with tendonitis/desmitis?
- inflammation - red, heat, swelling (proximal, midbody, suspensory bodies)
- lameness - “bowed tendon”
What are 3 major parts of diagnosing tendonitis/desmitis?
- PE - TPR, characterize swelling (edema, effusion, tendon damage)
- lameness exam - degree of lameness
- diagnostic nerve blocks - may interfere with U/S!
What is considered one of the most important modalities for tendonitis/desmitis?
U/S
+/- MRI
+/- radiographs
What are 3 steps to preparing for tendon ultrasounds?
- clip affected area and opposite limb for comparison
- scrub with chlorhexidine or betadine and rinse with alcohol
- apply gel liberally and allow it to soak into leg
How are tendons measured on ultrasound?
- split leg into zones from dorsal accessory carpal bone and below
- compare with measurements published for the size of tendons in the zone
How do tendons appear on transverse and longitudinal views?
TRANSVERSE - probe perpendicular, cross-section appearance
LONGITUDINAL - probe parallel, fiber pattern
Lable the tendons seen on this ultrasound.
- RED = SDF
- BLUE = DDF
- GREEN = accessory ligament of DDF (check ligament)
- YELLOW = suspensory ligament, attaches to MC3
What are 5 uses of U/S when diagnosing tendonitis?
- region or location of lesion
- length of lesion
- alteration of echogenicity - pattern (homogenous, heterogenous, focal, diffuse), scores
- % cross-sectional area affected
- changes in character of the lesion over time
What is the purpose of using MRI when diagnosing tendonitis?
finding pathology that is not visible on radiographs or ultrasound
- good for foot pathology
What are the 3 phases of tendon and ligament healing?
- INFLAMMATORY (2-3 days) - intratendinous hemorrhage at the site of disrupted matrix with edema, neutrophil infiltration, and proteolytic enzyme release (initial enlargement) –> no point in U/S at this point
- REPARATIVE (lasts months) - much higher % of type 3 collage (scar)
- REMODELING - gradual change back to type 1 collagen, but never to 100% –> scar is much more stiff compared to tendon
Where is re-injury most commonly seen in tendons?
adjacent to the original scar
What horses most commonly develop SDF tendonitis? What are 3 signs?
racehorses - speed injury
- lameness
- characteristic “bowed tendon” swelling
- pain on palpation
How is SDF tendonitis diagnosed? Treated?
U/S - monitors lesion resolution too
minimum 6 months of rest
What are 3 signs of DDF tendonitis? What is it commonly associated with?
- lameness
- less of a “bow” compared to SDF tendonitis
- pain on palpation
caudal heel pain - use MRI
How do flexor lesions in the digital tendon sheath appear? What impedes healing? What decreases prognosis?
carpal tunnel-like syndrome - palmar anular ligament constriction forms 2 bumps of tenosynovitis –> requires transection
synovial fluid
chronicity
What is a possible etiology to proximal suspensory ligament desmitis in the forelimb? What is the most common sign? What is associated?
performance horses working on questionable footing
intermittent, subtle lameness more obvious when on the outside of the circle, worse on soft ground (more strain on scar)
“splint” - exocytosis of MC2 or MC4
What flexion and nerve block are used to diagnose proximal suspensory ligament desmitis of the forelimb?
pain on palpation and FL flexion
lateral palmar nerve at the level of the accessory carpal bone
What 4 imaging modalities are available for proximal suspensory ligament desmitis of the forelimb?
- ultrasound - difficult due to varying amount of muscle fibers
- radiography - concurrent changes in MC3
- nuclear scintigraphy
- MRI
What are 2 common etiologies of proximal suspensory ligament desmitis of the hindlimb?
- sport horses - dressage, jumping, reining
- conformation - straight hocks with hyperextended fetlocks
What flexion and nerve block are used for diagnosing proximal suspensory ligament desmitis of the hindlimb?
pain on palpation and HL flexion
deep branch of the lateral plantar nerve
What are 4 imagins modalities used for diagnosing proximal suspensory ligament desmitis of the hindlimb?
- radiographs - sclerosis at points of insertion (proximal splint)
- U/S - enlargement of ligament, lesions, 1-2 days post-nerve block
- nuclear scintigraphy - 3-5 days post nerve block
- CT/MRI
What are 3 signs of branch of suspensory ligament desmitis?
- moderate lameness
- positive to lower limb flexion
- pain/swelling on palpation
What are 2 methods of diagnosing branch of suspensory ligament desmitis? What is prognosis like?
- U/S - insertional lesions, core lesions (roughened sesamoids and interruption near attachments)
- radiographs - concurrent PSB lesions
fair - ~40% return to full use, re-injury possible
What are 2 characteristics of degenerative suspensory ligament desmitis (DSLD)? What is the most common etiology?
- progression –> fetlock can eventually touch the ground
- bilateral, HL > FL
conformation - straight hock, fetlock hyperextension
What 3 treatments are used for degenerative suspensory ligament desmitis? What is prognosis like?
- corrective shoeing - egg bar and wedge –> less pressure on palmar/plantar (too much of a wedge can increase pressure of ligament)
- analgesia
- fetlock arthrodesis
guarded to grave
What are the 4 steps of intralesional therapy for soft tissue injuries?
- clip and aseptically prep the leg
- local block
- insert needle into the lesion under U/S guidance
- inject therapeutic agent
What is annular ligament desmotomy considered the only effective treatment for?
annular ligament constriction secondary to DDFT and SDFT tears
When is a fasciotomy/neurectomy performed? How is it performed?
chronic hindlimb proximal suspensory ligament desmitis
- transect plantar fascia - releases pressure and stops compartment syndrome
- transect innervation to the proximal suspensory - deep branch of the lateral plantar nerve
What are 3 examples of counter irritation for treating soft tissue injuries?
- external/internal blistering
- pin/line firing
- cryotherapy
What is septic tendon sheath treated? What are the 3 major complications?
- LAVAGE
- systemic and local antibiotics
- analgesia
- adhesions
- lysis of proximal sesamoid bones
- destruction of flexor tendons
How are collateral ligament ruptures treated in horses? What is prognosis like?
like a fracture - external coaptation for 4-6 weeks minimum
good with no underlying joint damage - may result in OA
