ch 70 muscle and tendon disorder Flashcards
What are the common classifications of muscular injury?
Contusions (blunt injuries), strains (indirect injuries), lacerations (sharp injuries)
Where do muscle strains most commonly occur?
At the musculotendinous junction
When do strains occur?
After powerful active contraction of the muscle occurs simultaneous with passive extension of the muscle unit
What muscles appear to be more prone to injury?
Muscles that cross 2 or more joints
What are the 3 stages of muscular injury?
Stage I: myositis and bruising, architecture intact
Stage II: myositis and some tearing of the facial sheath
Stage III: tearing of the fascial sheath, muscle fiber disruption, hematoma formation
Where are stage I and II injuries more likely?
Power group of muscles (triceps, biceps femoris, quads, tensor fascia lata, semitendinosus, semimembranosus)
Where are stage III injuries more likely?
Long head of triceps, gracilis, gastrocnemius, tensor fascia lata
What are the two processes by which muscle heals?
Direct regeneration of myofibrils, production of fibrous scar tissue
What determines the balance of these two processes (Direct regeneration of myofibrils, production of fibrous scar tissue)?
Source of myoblasts, intact extracellular matrix, adequate vascularization, adequate innervation, limited stress across the healing wound
Increased fibrosis = inadequate ECM, poor vascularization, poor innervation, increased stress across healing wound
Under what conditions will myofibrils lead to quick and complete repair?
Surviving sarcolemal nuclei, intact endomysium
When does hematoma form?
immediately
At what time point does cellular infiltration and phagocytosis occur following injury?
6-12hr
At what time point does healing commence and how does this happen?
48hr after injury
invasion of capillaries and myoblast proliferation followed by myofiber formation
During what time post-injury does fibroblast proliferation and collagen scar formation occur?
4-6d
By what day is the damaged area filled w/ a new collagen network
Day 10
Until what day does tissue strength continue to increase?
Day 14 (entire process slows down after this point)
What is the primary goal of treatment of muscle injury?
Maximize direct myofibril repair while minimizing scar formation by minimizing early disruptive effects of inflammation, edema
By what percentage can the ability of the muscle to produce tension be reduced w/ excessive scar tissue formation instead of myofibril repair?
50%
What are the recommendations within first 48 hours?
Cold compresses and NSAIDs with light compression bandages
Why is early mobilization following muscular injury important?
To ensure proper myofibril orientation
When should surgery be instigated for muscle trauma?
Advanced stage II and stage III strains to eliminate gaps and appose muscle to optimize healing without scar formation;
when initial inflammatory phase has receded (2-3d following injury)
principles of surgery for muscle strain?
Remove hematoma, debride necrotic material, muscle apposition
What type of suture material should be used with surgery for muscle strain? What pattern?
Long-term absorbable monofilament; horizontal mattress tension relieving sutures;
once sufficient tension sutures are placed to hold the bulk of muscle, additional appositional sutures applied through fascial sheaths
What duration of rest is recommended following surgical repair of muscle?
4w
Ruptures of what muscles occur in racing greyhounds?
Avulsion of the origin of the long head of the triceps brachii; rupture of the gracilis m
PE findings for rupture of long head of triceps brachii?
Depression present caudal and distal to scapula
Treatment options for Avulsion of the origin of the long head of the triceps brachii; rupture of the gracilis m
Conservative (may not reach same performance level) or reattaching muscle belly to scapula
What does avulsion of tendon of insertion of triceps result in?
Severe thoracic limb disability due to loss of elbow extension
What is avulsion of triceps tendon associated with?
Trauma or intratendinous corticosteroid injection
How can avulsion of the origin of the long head of the triceps brachii; rupture of the gracilis m be repaired?
Can use synthetic graft; elbow must be extended throughout healing (transarticular ex fix or transosseous screw)
What is the diagnostic clinical sign associated w/serratus ventralis rupture?
Dramatic dorsal displacement of the scapula
In what other breeds has rupture of the gracilis muscle been described?
GSD, foxhounds, greyhounds
Where can rupture of the gracilis muscle occur?
Musculotendinous jxn, or origin or insertion can avulse from its attachment
Clinical signs of rupture of the gracilis muscle
Large hematoma on medial aspect of the thigh, bruising +/- depression if complete or significant rupture
Treatment of choice for rupture of the gracilis muscle
Surgical repair/reattachment
Treatment of choice for rupture of the gracilis muscle
Surgical repair/reattachment
What maneuvers can diagnose iliopsoas and pectineus muscle strain?
Extension and internal rotation of the hip, digital pressure over the area of the iliopsoas on the lesser trochanter
What is muscle contracture?
The abnormal shortening of muscle tissue, rendering the muscle highly resistant to stretching
Why does shortening occur?
Part of replacement of the majority of muscle tissue by fibrous connective tissue
What causes of muscle contracture have been implicated?
Compartment syndrome, infection, trauma, repetitive strain injury, fracture, prolonged immobilization, various primary muscle diseases
what muscles are most commonly affected by contracture?
Infraspinatus, quadriceps femoris, gracilis, semitendinosus
What other muscles have been reported to be affected by contracture?
Sartorius, supraspinatus, teres minor, iliopsoas, brachialis
What is the most common type of dog affected by infraspinatus contracture?
Medium sized working or athletic dogs
Clinical progression for infraspinatus contracture?
Transient lameness 4-6w prior to contracture; weight bearing lameness or gait anomaly (circumduction of affected forelimb as it is advanced, carpal flip), usually pain free
How do dogs w/ infraspinatus contracture hold the affected limb at rest?
Abducted shoulder, adducted elbow, lower limb abducted and externally rotated
Treatment of choice for infraspinatus contracture
Tendinectomy of the tendon of insertion and surrounding fibrous adhesions
When does quadriceps contracture most commonly occur?
Following femoral fracture, particularly in young dogs
When is risk of quadriceps contracture increased?
If fracture management results in immobilization or poor use of limb during healing
Clinical signs of quadriceps contracture?
Inability to flex stifle or tarsus, leg held straight out in extension
What occurs histologically in cases with quadriceps contracture?
Fibrotic replacement of muscle fibers; eventually periarticular fibrosis and joint ankylosis develop
How successful is surgical intervention for quadriceps contracture
Limited success (breaking down adhesions + muscle lengthening procedure); usually results in amputation
What dogs get gracilis contracture?
German shepherds, middle age (3-7y)
What is the characteristic gait of gracilis contracture?
Limb raised in jerk-like fashion with hyperflexion of tarsocrural joint and internal rotation of metatarsus
Physical exam findings for dog with gracilis contracture?
firm gracilis and enlarged tendon of insertion
Conservative or surgical treatment recommended for gracilis contracture?
Conservative – near 100% recurrence with surgery
Who gets semitendinosus contracture? What does it look like?
German shepherds, signs and treatment identical to gracilis contracture
Who gets flexor carpi ulnaris contracture? (aka carpal flexion syndrome)
Puppies 6-24 weeks
Clinical signs of flexor carpi ulnaris contracture?
Inability to extend carpus, tendon of insertion is tight
Is flexor carpi ulnaris contracture reversible?
Yes – spontaneous resolution with reduced activity and carpal support bandages; recovery in 2-3 weeks
What does tendon healing rely on?
Influx of new fibroblasts to produce new collagen
How does tendon healing occur in paratenon-lined tendons?
In paratenon-lined tendons has vascular beds and there is influx of undifferentiated cells from paratenon
What are examples of paratenon-lined tendons?
aka vascular tendon
triceps and gastroc
How does tendon healing occur in sheathed tendons (avascular tendons)
In sheathed tendon (avascular tendon: DDF)- relies on intrinsic blood supply for healing, so lower healing potential
What does gap formation in tendon healing lead to?
Scar/fibrous formation
When does the tendon lose holding power?
5 days
When does tendon fibroplasia and collagenation occurs?
2 weeks, during these steps gradual increase in strength
For how long does suture provide all strength and resistance of gap formation or elongation?
3 weeks, otherwise gap formation = scar formation
How long before the strength of the tendon achieves 56% of its strength?
6 weeks, its sufficient to exercise
How strong is the the tendon a year following repair?
79%
Recommendations to avoid further damage to tendon in surgery?
Needles or K-wires inserted through body of tendon to reduce manipulation of edges
What suture type on tendons?
Monofilament synthetic long-term absorbable or nonabsorbable
What suture pattern you can use for flat or rounded tendons?
Flat tendons: Kessler (locking loop), Krackow; Rounded tendons: three-loop pulley
What suture to provide final apposition?
Finer gauge suture, horizontal mattress sutures
