Ch 70 - Muscle and Tendon Disorders Flashcards

1
Q

What is the most common general location for a muscle strain?
What are the three stages of muscle strain?

A

Most common at musculotendinous junction, muscles which cross two or more joints appear predisposed

Three stages:
- Stage I: Myositis and brusing, architecture intact
- Stage II: Myositis and some tearing of the fascial sheath
- Stage III: Tearing of the fascial sheath, muscle fiber disruption and haematoma formation

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2
Q

What are the two processes of muscle healing?

A
  • Direct regeneration of myofibrils
  • Production of fibrous scar tissue
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3
Q

What are the general principles of muscle treatment?

A
  • Maximise direct myofibril repair while minimising scar formation (excessive scar can reduce a muscles ability to produce tension by 50%)
  • Early mobilisation essential for proper myofibril orientation and can be considered after day 5-10
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4
Q

What are some common muscle injuries of the thoracic limb?

A
  • Rupture of long head of triceps brachii (racing Greyhounds). Causes depression caudal and distal to scapula. Reattachment recommended
  • Avulsion of triceps brachii tendon of insertion. Primary reattachment to olecranon with immobilisation with transarticular ESF or transarticular screw
  • Rupture of serratus ventralis causing dramatic dorsal replacement of scapula
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5
Q

What are some common muscle injuries of the pelvic limb?

A
  • Rupture of gracilis (Greyhounds, GSD, Foxhounds). Surgical repair or reattachment
  • Iliopsoas and pectineus muscle strain. Most common! Conservative management usually successful
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6
Q

What are the most common forms of muscle contracture in dogs?

A
  • Infraspinatus contracture (circumbuction and carpal flip with abduction of shoulder, adduction of elbow, lower limb abducted and externally rotated. Tendonectomy with release of surrounding fibrous tissue
  • Quadriceps contracture
  • Gracilis and semitendinosus contracture (limb rises in jerk-like fashion with hyperflexion of the tarsocrural joint and internal rotation of metatarsus)
  • Flexor carpi ulnaris muscle of puppies
  • Myositis ossificans (heterotrophic bone formation in muscles after trauma, most common at hip)
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7
Q

What cells do tendon healing rely on?

A

Influx of fibroblasts to produce new collagen

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8
Q

How does tendon healing differ between paratenon-lined tendons and sheathed tendons?

A

Paratenon-lined:
- Can recieve vascular buds and an influx of undifferentiated cells from the paratenon and surrounding soft tissues.
- Better capacity for rapid healing
- Tendons of insertion of gastroc and triceps

Sheathed:
- Depend much more on intrinsic blood supply
- Digital flexor tendons

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9
Q

How long must the suture material primarily maintain strength and resist gap formation during tendon healing?
What are the three main forms of suture patterns for tendon apposition?

A

Initial three weeks

Suture patterns:
- Locking loop
- Krakow
- Three-loop pulley

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10
Q

What percentage strength does a tendon have at 6 weeks and 1 year after repair?
What percentage of normal capacity strain in placed on a tendon during normal muscle contraction?

A
  • 6 weeks: 56%
  • 1 year: 79%

Normal contraction places 25-33% of normal full capacity of strain. Thus, strength at 6 weeks should be sufficient to withstand limited exercise

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11
Q

What is the general principle of tendon repair?

A

Produce healing without gap formation and allow early loading to ensure correct collagen formation and alignment

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12
Q

What are some common tendon injuries in small animals?

A
  • Superficial digital flexor tendon laceration
  • Common calcaneal tendon injury (most common)
  • Injuries to tendon of origin of biceps brachii (second most common)
  • Injuries to long digital extensor tendon (avulsion or displacement)
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