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THRALL - Thom > 19. Fracture Healing and Complications in Dogs > Flashcards

19. Fracture Healing and Complications in Dogs Flashcards

1
Q

List 5 types of bone

What types are found in 1) epiphysis and metaphysis 2) diaphysis?

A

Woven, Intramembranous, Long, Flat, Compact

1) Woven, cancellous and llamelar
2) Cortical (compact)

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2
Q

Function of periosteum?

A

Protection and nutrition

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3
Q

List the 3 types of bone cell

A

Osteoblasts

Osteocytes (develop from osteoblasts)

Osteoclasts

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4
Q

Functions of:

1) PTH
2) Calcitonin
3) Vit D

A

1) PTH: in response to LOW Ca -> mobilisation from bone (stimulates osteoclasts)
2) Calcitonin: In response to HIGH Ca -> deposit in bone (inhibits osteoclasts, and GI / renal absorption)
3) Vit D: In response to low Ca -> Promotes Ca and Phos absorption from GI, increased mobilisation from bone

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5
Q

What 3 methods does bone have to react to stiumulus?

A

1) Proliferation
2) Absorption
3) BOTH!

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6
Q

By what methods does bone develop? WHICH BONES DO WHICH?

A

Intramembranous ossification:

  • SKULL AND MANDIBLE
  • Mesenchymal cell proliferation -> transform into matrix producing osteoblasts. Matrix calcifies.
  • Fibrovascular layer on internal and external surfaces provide nutrition and osteogenic cells

Endochondral ossification:

  • LONG BONES predominantly (but some intramembranous)
  • Formation of cartilage model replaced by bone

BOTH:

  • EXTREMITIES, SPINE, PELVIS
  • E.g. tubular bones = primary centre of ossification in middle, growth by intramembranous, then secondary ossification centres develop in apophyses / epiphyses. Further growth from these centres by endochondral.

=> can do both in some instances

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7
Q

What are the 5 histo zones of the physis? Where is the weakest zone?

A

1) Resting zone (immature cells on epiphyseal side of physis)
2) Proliferation / cell growth
3) Maturation
4) Degeneration
5) Provisional calcification

=> WEAK AT HYPERTROPHIED LAYER (maturation / degen / provisional calcification)

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8
Q

What are the 4 major elecments of fracture repair?

A

1) Mechanical environment
2) Osteoconductive scaffolds
3) Osteogenic cells
4) Growth factores

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9
Q

Describe the two main methods of bone healing

A

1) Direct bone healing
- Requires EXCELLENT REDUCTION AND ALIGNMENT and RIGID FIXATION
- Gap < 300microm
- No cartilagenous stage
- Gap filled with fibrous bone, remodelling and reconstruction of haversian system across fracture
2) Indirect bone healing
- MOST COMMON
- CALLUS due to lack of rigid fixation
- Intramembranous and endochondral
- Haematoma -> Fibrous tissue -> fibrocartilage -> endochondral ossification: woven bone (callus) -> compact bone

=> presence of inflamation is key difference from embryonic bone formation

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10
Q

How much stress can the three different tissues associated with bone healing tolerate? What is the progression of tissue types during type 2 healing?

A
  • KEY: MORE FLEXIBLE INITIALLY, BECOMING MORE RIGID

Haematoma -> Fibrous tissue -> fibrocartilage -> endochondral ossification: woven bone (callus) -> compact bone

Granulation tissue -> tolerate 100% deformation

Fibrous tissue -> 10% deformation

Bone -> 2% deformation

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11
Q

What type of bone is produced by distraction osteogenesis?

A
  • Parallel columns of LAMELLAR BONE
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12
Q

List 12 factors affecting fracture healing

A
  • Patient age / weight
  • Reduction
  • Type of fracture
  • Bone involved
  • Quality of reduction
  • Stability
  • Blood supply
  • Infection
  • Systemic disease
  • Iatrogenic factors
  • Pathological fracture
  • Drugs (CS or NSAIDS)
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13
Q

What % of bone fragment ends should be in contact to expect healing?

A

>50%

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14
Q

What is the most common cause of poor fracture healing?

A
  • INSTABILITY
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15
Q

What is the proposed benefit of minimally invasive fracture repair techniques?

A
  • Preserve soft tissue environement -> Viability essential to fracture healing
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16
Q

Small breed dogs may have delayed healing of bones in which region compared to large breeds?

A
  • Antebrachial

=> ALSO HIGHER COMPLICATION RATE

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17
Q

List 4 systemic comorbidities that may delay fracture healing

A
  • HypoT
  • HyperparaT
  • DM
  • Paraneoplastic syndromes
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18
Q

What is the incidence of nonunion fracture in cats and dogs?

A
  • Cats: 0.85-4.3%
  • Dogs: 0-6% (av 3.4%)
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19
Q

Fracture repair delay of what duration is associated with poorer functional outcome?

A

>48hrs

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20
Q

Increased radiopharmaceutical uptake in fractures is associated with what process?

A
  • Osteoblastic activity

=> SENS not spec

21
Q

What is MRI useful in evalulation of fractures?

A
  • Better than rx: evaluation of physeal inury / closure
  • Evaluation of changes to marrow -> aid identification of bone lesions
  • Soft tissues…
22
Q

SALTER HARRIS!

23
Q

How are long and short oblique fractures designated?

A
  • Transverse = 90 deg to long axis
  • Short oblique = >45
  • Long oblique = <45
24
Q

What is a greenstick fracture?

A
  • Incomplete fracture of only one cortex, and concurrent bending of opposite cortex (plastic deformation)
25
How is a comminuted fracture defined?
- 3+ fragments, communication of fracture lines =\> large triangular fragment when 3 -\> BUTTERFLY fragment =\> Severe if \>5 fragments
26
Classification system for open fractures?
Type 1) Small puncture wound \<1cm caused by 1 fragment Type 2) Variable sized wound, more ST damage Type 3) Severe fragmentation, extensive ST injury +- skin loss 3a) No recon 3b) Recon required 3c) Amputation or near amputation of limb
27
What feature of chip fractures helps distinguish them from e.g. dystophic mineralisation or ossificaiton centres?
- Presence of fracture bed
28
What is the definition of slab fracture? Which bones are commonly affected?
- TYPICALLY CUBOIDAL - Fractures that run from one joint surface to another =\> if only one joint surface = chip
29
Definition of segmental fracture?
- Multiple fracture lines that DO NOT communicate (cf. comminuted)
30
Definition of condylar fracture?
- Fracture of condyle away from parent bone =\> ALSO CAN HAVE BICONDYLAR, SUPRACONDYLAR, T and Y
31
Definition of abrasion / shearing fracture?
- Often due to friction / glancing trauma -\> e.g. asphalt =\> loss of soft tissue and bone, OPEN and commonly involve joint
32
What are the ABCDS of orthopaedic imaging?
**A**lignment **B**one **C**artilage (= joints) **D**evice **S**oft tissue
33
What can result in excessive callus formation / periosteal reaction x3?
- Movement - Infection - Periosteal injury
34
DDx for periimplant lucency
- Loosening - Infection - Bone necrosis (high speed drill) - Artefact
35
What features are typically identified with implant associated infection?
- Irregular lucency with ill-defined margins =\> NOTE: If even and sclerotic margins, less likely infectious!
36
What radiographic criterion is most commoly used to demonstrate fracture healing?
- Callus bridging the fracture site
37
How do different stabilisation methods relate to callus formation?
- MORE callus with casts - ESF \< casts - Primary: Minimal
38
How quickly should post op emphysema take to resolve?
7-10 days
39
4 DDx for ST mineralisation around fracture site
- Fragment - Bone graft - Dystrophic (associated with injury) - Mineralised haematoma
40
List 6 classes of malunion
- Valgus vs varus - Antecurvatum vs recurvatum - Torsional - Translational
41
What degree of torsional malunion is poorly visualised on rx?
\<10 deg
42
Difference between delayed and non union?
- Delayed: Taking longer than should, but progressive and will eventually heal - Non-union: Not healed, and no evidence of progression =\> ALL GO THROUGH DELAYED UNION PHASE
43
What is a pseudoarthrosis? How is it different from a fibrous union?
- Chronic motion at fracture site -\> fibrocartlage fills gap. May have good use / no pain Fibrous union = stabilized by fibrous tissue. Radiolucent gap or line may remain, COMMON IN EQUINE DISTAL PHALANX
44
Classifications of Nonunion fractures?
**VIABLE (reactive / vascular) x 3 = Reactive bone and callus** **- Hypertrophic:** ABUNDANT CALLUS, movement / overexercise / loosening. **- Moderately hypertrophic:** LESS CALLUS THAN HYPERTROPHIC **- Oligotrophic:** LITTLE OR NO CALLUS, difficult to distinguish from nonviable. Scinti. Or if any bone activity at fragment ends **NON-VIABLE x 4 =uncommon, lack of blood supply** **- Dystrophic:** Radiolucent fracture gap, no callus and rounded sclerotic ends **- Necrotic** Sequestrum formation. Fragment with sharp edges and sclerotic **- Defect** Large fracture gap too large to bridge **- Atrophic** Progression of other type -\> resorption, rounding of ends and osteoporosis.
45
Anatomy of a sequestrum!
- Sequestrum: Sharply marginated sclerotic fragment - Involucrum: Radiolucent halo, with sclerotic margin - Cloaca: Draining tract NOTE MAY BE STERILE OR INFECTIOUS
46
Angular limb deformity in the dog most commonly occurs from premature closure of which physis? What features are classically seen with angular limb deformity secondary to this issue?
- Distal ulnar physis =\> conical shape may amplify force =\> Lack of synchronous growth = SHORT ULNA SYNDROME: **CRANIAL BOWING OF RADIUS** **DISTAL SUBLUX OF ULNA FROM HUMERUS** **SUBLUX ULNAR CARPAL JOINT** **VALGUS ANGULATION OF MANUS**
47
Features of premature distal radial physis closure?
- Humeroradial sublux - Humeroulnar sublux - Antebrachiocarpal sublux +- Manus deflection (less severe than ulna)
48
Box

THRALL - Thom (40 decks)

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