Locomotion 2 Flashcards
For patients with high energy trauma what is the priority
- For patients presenting with high energy trauma orthopaedic injury is NOT the priority
- Once the patient is stabilized, visual orthopaedic assessment, screening neurological examination and orthopaedic examination can take place:
○ All limbs and the spinal column should be evaluated
○ Watch the patient carefully when they are walking.
What are the 3 natures of fractures and 3 energy levels
1) traumatic
2) stress
3) pathologic (underlying disease)
1) low energy - non-displaced fracture
2) high energy (comminuted fracture
3) very high energy (gunshot injury)
What are the 4 different completeness categories of fractures
1) Complete - fracture involves the entire cortex; on a single radiograph both cortical lines are fractured
2) Incomplete - fracture doesn’t involve the entire cortex, with some cortex intact
○ Generally due to penetration
3) Greenstick fracture - immature bones, periosteum is intact
4) Stress fracture - due to repeated cycling, more common in performance animals
What are the 4 different types in number of fracture lines
1) Simple - one fracture line - transverse or oblique
2) Multiple - >1 fracture line in a single bone, fractures are not continuous
○ spiral and segmental (directions)
3) Comminuted - complete fracture with multiple bone fragments
○ Can no longer reconstruct
4) Segmental - complete fracture, with a diaphyseal fragment with a complete cortex
What are the 7 different direction of fracture lines
1) Transverse
2) Oblique
3) Spiral
4) Fissure
5) Avulsion
6) Depressed (flat bones)
7) “T” and “Y” fractures (elbows)
Relationship of fracture fragments what need to describe
describe the location of major distal fragment, relative to proximal fragment
- Describe the location of major distal fragment
- Degree of end-to-end apposition
- Alignment
- angulation
- rotation
- Limb/bone shortening (over-riding)
- Luxations - combination of injury to both the bone and joint -> most commonly occur with the elbow and the hock
What are the 2 different soft tissue injury
1) closed (skin remains intact)
2) open
- Gas opacity in soft tissues - communication with the outside world
- Bone fragments protruding through skin, and radiopaque debris within soft tissue
- Interposition of soft tissue
what occurs with new bone formation, when is there a fibrous scar and the 3 stages
New bone forms and remodels –no fibrous scar tissue
- Fibrous scar tissue occurs when there is a failure in bone healing -> consequence of unfavourable mechanical environment such as instability
Stages:
1) Fracture-haematoma following a fracture (haemorrhage)
2) Cellular components such as activated platelets and components
3) Then heal via a variety of means
What are the 2 types of bone healing and the types within
1) Direct bone union
1. primary and secondary
primary divided into contact and gap healing
2) indirect bone union - fracture callous forms
Inter-fragmentary Strain Theory what is the equation and why is it important
strain = change in length of gap/ original length of gap
- Forming bone is intolerant of strain
- New bone can only form under conditions of < 2% strain
Strain is high when:
1. Change in length is high (instability)
2. The initial gap is small (large fracture gap can lead to a low strain environment)
Direct Bone Union what does it require and does a fracture callus form
•Requires: - Anatomic alignment - Absolute stability of fragments (<2% strain) - Compression - ideally • Little to no fracture callus forms
Contact healing when does it occur and how
Compression - occurs when bone fragments are in direct contact (no fracture gap) and fragments are stable
• Cutting cones (the way the osteoclasts come through)
- Simple transverse fracture, simple anatomically alignment
- Composed of Osteoclasts with trailing osteoblasts cross the fracture site
» Rate 50-80um/day
» Simultaneous resorption of old bone and deposition of new lamellar bone
Gap healing when does it occur and how
- Occurs where small gaps (<1mm) present between fracture fragments but rigid stability is present
- Inter-fragmentary strain < 2%
- Vessels and loose connective tissue
- Woven bone deposited initially:’
- Orientation perpendicular to fracture ends (weak)
- 3 weeks –cutting cones remodel lamellar bone parallel to long axis
What is the direction of inital bone formation for contact and gap healing and why
contact - parallel as lamellar bone initally deposited
Gap - perpendivular as woven bone initially deposited before cutting cones remodel to lamellar bone
Secondary Osteonal Reconstruction when occur
- can occur with callus where stability less than absolute and deformation great to allow primary bone deposition
- widening of a gap to decrease strain
- callus formation to increase stability and decrease strain
Indirect bone union reslt of what, what results in and the 4 phases
The result of:
- Instability (IFS>2%)
- Gaps between fragment ends >1mm
•Results in:
- Sequential and orderly deposition of tissues more tolerant of strain to those less tolerant
•Phases:
1. Inflammatory (haematoma, granulation tissue) - initiates fracture healing -> bleeding and platelet degranulation results in the delivery of cytokines and growth factors and an influx of inflammatory cells to clean up debris and damaged tissue
2. Soft Callus (Cartilage)
3. Hard Callus -> woven bone
4. Remodelling -> lamellar bone
•Callus deposition is a response to instability and results in increasing stability
What are the 2 main forces created and their effect on bone and what has to occur for a fracture to occur
1) Weight bearing creates a ground reaction force
- This creates bending, compressive and rotational forces on the bone
2) Muscle contraction creates tension and rotation
- Forces create the fracture -> when the sum of forces that act on the bone exceeds its strength
- Act at the site once the fracture has been created -> Instability
what is the bone, what is the amount of deformation proportional to, and what is the amount of soft tissue damage proportional to and what occurs with high and low energy fractures
Bone is viscoelastic
- Amount of deformation is proportional to rate of loading
- Energy stored during deformation released at time of yield (fracture)
- Amount of soft tissue damage is proportional to energy released
- Energy absorbed = area under curve= energy released at fracture
- Rapid loading -> high energy fracture (gunshot wounds) -> lots of soft tissue damage
Low loading -> low energy fracture -> less soft tissue injury
Bone is anisotropic what does this mean and list the forces that act on it
- Stronger when loaded longitudinally vs transversely
- Stronger in compression vs tension
THEREFORE - The forces acting on bone determine the fracture conformation / morphology
- Compression
- Bending
- Torsion
- Tension / distraction
What do compressive forces and bending forces lead to
compressive = oblique fractures
bending = transverse
- concave surface subject to compression
- convex surface subject to tension
- bone is weaker in tension - fracture starts here and propagates across the bone
what do tensile forces and torsional forces lead to
= trasnverse fracture
- fracture is perpendicular to direction of tensile load
- often combination with bending
torsional = spiral cracks
Bending + compression what does it lead to, how does it occur
= butterfly fracture
- starts similar to pure bending -> propagates along transverse line -> compression causes an oblique fracture on the other side
What are the 3 aims of the surgeon in fracture repair
1) Provide stability against forces acting at the fracture site - Choose appropriate implant system
2) Preserve the vascular supply of the healing bone
3) Limb alignment and alignment of fracture ends
What are the 3 factors that result in different prognosis for fractures
1) Mechanical factors - what breed (large or small), how many limbs, compression what number of fragments
- High score if single limb, small breed, compression needed
2) Biological factors - health of the patient, age, co-current injuries
- High score if young, healthy, closed fracture etc,
3) Patent/owner factors - risk tolerance, compliance, economic state
- High score if good compliance for client and patient
carpenters approach what type of approach, positives and negatives and what suitable to
Carpnter’s Approach
- Historical approach - not used as much
- Rigid anatomic reconstruction of bone column
- Functional load sharing
NEGATIVE
- Extensive dissection:
- Loss of soft tissue attachment
- ↓ Blood supply
- Remove fracture haematoma
- Longer time taken therefore higher chance of infection
•Suitable for simple transverse fractures
Gardener’s Approach what also called, positives and negatives and what suitable to
- Also known as Biologic Osteosynthesis
- Alignment of fragments to preserve length, angular and rotational alignment
- No attempt at anatomic reconstruction
- Preservation of fracture haematoma
- Preservation of soft tissue attachments and blood supply
- Closed or indirect fracture reduction
- Open but do not touch approach (OBDNT)
give examples of external and internal fixation
External coaptation - Bandages - Splints/Casts Internal fixation: - Intramedullary (IM) Pins / wires - Interlocking nails (ILNs) - Plates / Screws - DCP vs Locking plates
External Coaptation what are the 4 ways it can be used, what forces are they good at preventing and which aren’t they
1) Primary method of immobilisation - cast
2) Temporary immobilisation
3) Adjunctive support/immobilisation
4) To prevent weight bearing
- Only good at preventing BENDING
- Can Potentially reduce ROTATIONAL forces but only if the joint above and below the fracture are immobilised.
- Easily accomplished for metapodial and phalangeal fractures
- Difficult to accomplish/maintain for antebrachial or tibial fractures
Extremely difficult to achieve for humeral and femoral fractures
What are the 2 types of bandages and what are they good for
1) Robert jones bandage
- good for temporary support
- very bulky
2) modifies robert jones
- useful to limit soft tissue swelling
- not sufficient for fractures
How to increase resistance of material to bending forces
- AMI of a rod ∝ Radius 4
- Small increase in radius → large increase in AMI
- Choose larger pin size when possible to get increase resist to bending
- AMI of a plate ∝Height 3
- Thicker plate resistance to bending
Bending forces what best neutralised by
- Best neutralised by an implant placed in the neutral axis of the bone - In the medullary canal
- Pins - good with bending, not rotational, no compression
- Interlocking nails - combine pins with interlocking help with additional stability
Alternate Methods: - Plate fixation within the bone
- External fixation
Torsional forces neutralised by
- Plate and screws
- Interlocking nail
- External skeletal fixation
•Poorly resisted by intramedullary pins - Combine IM pin with plate or ESF
Cyclic stress and implant failure what occurs
- Stainless steel is very susceptible to cyclic stress
- Fracture management is a race between bone healing and implant failure
- Implants will almost always fail IF the bone does not heal
- Why regular follow-up is needed
Bone marrow how look different between adult and young
- Diffusely red in younger animals -> high amount of red marrow -> high haematopoiesis
- Atrophy of the fat within the bone marrow -> emaciated state of the animal, last area that fat would be used
What are the 3 general skeletal muscle responses
1) Innervation
○ Skeletal muscle need motoneuron to innervate muscle to get contraction
2) Necrosis and regeneration
○ necrosis parasitic, black leg disease, trauma
○ Doesn’t matter the cause the healing is the same
3) Structural
○ Tends to be genetics
What are the 7 signs of muscle disease
- Atrophy -> condition score decrease
- Hypertrophy -> can be compensatory, special issue in the cardiac muscle
- Swelling -> fluid accumulation
- Weakness
- Muscle spasm -> uncontrolled contraction
- Abnormal gait -> muscular dystrophy first clinical sign
- Esophageal dysfunction ->
Muscle dysfunction what are the 3 general causes and causes within
1) Physiological
- muscle rupture
- exercise induced damage
- loss of innervation
- loss of blood supply -> ischemic damage in muscle
- endocrine/electrolyte imbalance
2) genetic
- errors of metabolism
- genetic defects
- developmental defects
3) Nutritional/toxic
- deficiency of selenuim/vit E
- toxic plants
- feed additives
- toxins
What is a motor unit
Motoneuron + all muscle fibres innervated from the motoneuron
Muscle fibres just innervated by ONE motoneuron
What are the 2 fibre types and there function
Type 1 - rich in mitochondria, fatigue resistant, tend to be in posture related muscle
Type 2 fibres - white fibres
- Larger, fast-twitching fibres, not as much mitochondria, rely on glycolysis, fatigue quickly
What are the 5 causes f atrophy and the fibre type mainly affected
1) denervation - type 1 and 2
2) disuse - type 2
3) endocrine - type 2
4) malnutrition - type 2
5) congenital myopathy - type 1
