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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!

A
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
Q

How is a comminuted fracture defined?

A
  • 3+ fragments, communication of fracture lines

=> large triangular fragment when 3 -> BUTTERFLY fragment

=> Severe if >5 fragments

26
Q

Classification system for open fractures?

A

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
Q

What feature of chip fractures helps distinguish them from e.g. dystophic mineralisation or ossificaiton centres?

A
  • Presence of fracture bed
28
Q

What is the definition of slab fracture? Which bones are commonly affected?

A
  • TYPICALLY CUBOIDAL
  • Fractures that run from one joint surface to another

=> if only one joint surface = chip

29
Q

Definition of segmental fracture?

A
  • Multiple fracture lines that DO NOT communicate (cf. comminuted)
30
Q

Definition of condylar fracture?

A
  • Fracture of condyle away from parent bone

=> ALSO CAN HAVE BICONDYLAR, SUPRACONDYLAR, T and Y

31
Q

Definition of abrasion / shearing fracture?

A
  • Often due to friction / glancing trauma -> e.g. asphalt

=> loss of soft tissue and bone, OPEN and commonly involve joint

32
Q

What are the ABCDS of orthopaedic imaging?

A

Alignment

Bone

Cartilage (= joints)

Device

Soft tissue

33
Q

What can result in excessive callus formation / periosteal reaction x3?

A
  • Movement
  • Infection
  • Periosteal injury
34
Q

DDx for periimplant lucency

A
  • Loosening
  • Infection
  • Bone necrosis (high speed drill)
  • Artefact
35
Q

What features are typically identified with implant associated infection?

A
  • Irregular lucency with ill-defined margins

=> NOTE: If even and sclerotic margins, less likely infectious!

36
Q

What radiographic criterion is most commoly used to demonstrate fracture healing?

A
  • Callus bridging the fracture site
37
Q

How do different stabilisation methods relate to callus formation?

A
  • MORE callus with casts
  • ESF < casts
  • Primary: Minimal
38
Q

How quickly should post op emphysema take to resolve?

A

7-10 days

39
Q

4 DDx for ST mineralisation around fracture site

A
  • Fragment
  • Bone graft
  • Dystrophic (associated with injury)
  • Mineralised haematoma
40
Q

List 6 classes of malunion

A
  • Valgus vs varus
  • Antecurvatum vs recurvatum
  • Torsional
  • Translational
41
Q

What degree of torsional malunion is poorly visualised on rx?

A

<10 deg

42
Q

Difference between delayed and non union?

A
  • 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
Q

What is a pseudoarthrosis? How is it different from a fibrous union?

A
  • 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
Q

Classifications of Nonunion fractures?

A

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
Q

Anatomy of a sequestrum!

A
  • Sequestrum: Sharply marginated sclerotic fragment
  • Involucrum: Radiolucent halo, with sclerotic margin
  • Cloaca: Draining tract

NOTE MAY BE STERILE OR INFECTIOUS

46
Q

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?

A
  • 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
Q

Features of premature distal radial physis closure?

A
  • Humeroradial sublux
  • Humeroulnar sublux
  • Antebrachiocarpal sublux

+- Manus deflection (less severe than ulna)

48
Q

Box

A

THRALL - Thom (40 decks)

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