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boards > ch 45 delayed union, non-union, and malunion > Flashcards

ch 45 delayed union, non-union, and malunion Flashcards

1
Q

what are the 4 tenants of bone healing and regeneration

A

mechanics
scaffold
growth factors
cells

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2
Q

what is geometric configuration as it relates to bone healing

A

geometric configuration centers on limb alignment or fracture reduction

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3
Q

what is the maximum gap that a bone can have and still heal

A

definitive number is unknown but ill advised to have a gap wider than the diameter of the bone

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4
Q

what is the most favorable mechanical environment for bone formation

A

Low to moderate magnitudes of tensile strain and hydrostatic tensile stress

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5
Q

during weight bearing, most forces across the diaphysis are ______ → healing tissues are compressed and hydrostatic forces are placed _______ → tension is created on the _______ of the fracture callus

A

During weight bearing, most forces across the diaphysis are AXIAL
Healing tissues are compressed and hydrostatic forces are placed ABAXIALLY
Tension is created on the OUTSIDE of the fracture callus

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6
Q

Bone is formed _____ along tension stresses

A

Bone is formed abaxially along tension stresses

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7
Q

Closer to the center of the callus, stem cells are subjected to _______ forces → favors _____

A

Closer to the center of the callus, stem cells are subjected to COMPRESSIVE forces → favors CHONDROGENESIS

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8
Q

how is axial strain
calculated

A

decrease in gap width divided by total gap width

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9
Q

The amount of strain shown to enhance new bone formation in axial load is as high as _______

A

36%

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10
Q

strains of _____ demonstrate far less bone healing

A

7%

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11
Q

For small gaps, _____ interfragmentary movements result in _____ periosteal areas of callus

A

For small gaps, LARGER interfragmentary movements result in LARGER periosteal areas of callus

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12
Q

For large gaps, interfragmentary movement _______ stimulation of callus and _______ consolidation of the fracture

A

For large gaps, interfragmentary movement INHIBITS stimulation of callus and DELAYS consolidation of the fracture

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13
Q

Stress protection

A

refers to the inhibited healing of fractures if too little strain is imparted to the healing fracture callus

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14
Q

what is the strain needed for simple axial loading and fx with a few to several mm of gap or comminution

A

5-10%

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15
Q

Tensile forces promote stem cell differentiation and proliferation along ______ lineages

A

Tensile forces promote stem cell differentiation and proliferation along OSTEOBLASTIC lineages

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16
Q

Compressive forces promote stem cell proliferation along _______ lineages

A

Compressive forces promote stem cell proliferation along CHONDROBLASTIC lineages

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17
Q

_______ forces promote stem cell proliferation along chondroblastic lineages

A

COMPRESSIVE forces promote stem cell proliferation along chondroblastic lineages

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18
Q

__________ forces promote stem cell differentiation and proliferation along osteoblastic lineages

A

TENSILE forces promote stem cell differentiation and proliferation along osteoblastic lineages

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19
Q

bending forces have compression on ______ side of bend, tension on _______ side

A

bending forces have compression on CONCAVE side of bend, tension on CONVEX side

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20
Q

Bending is a combination of ______ and _____. Maximal ______ and _____ occur at the surface of the bone and decrease toward the neutral axis.

A

Bending is a combination of COMPRESSION and TENSION. Maximal COMPRESSION and TENSION occur at the surface of the bone and decrease toward the neutral axis.

21
Q

Cellular activity (migration, adhesion, proliferation, differentiation) occurs in concert with ________ signaling

A

humoral signaling

22
Q

what are negative intrinsic factors for growth factor activity

A

Diaphyseal cortical bone,
decreased/compromised vascularity of the periosteum,
sparse soft tissue attachments
aged patient

23
Q

what is plate luting

A

technique used in fx repair where PMMA is placed between the bone and the plate as well as the screw heads in the plate

24
Q

Cambrium

A

layer of periosteum
Inner layer cells are osteongenic precursors important for skeletal growth, remodeling, and regional fx repair

25
Q

define delayed union

A

prolongation in time for fx healing

26
Q

how is direct fracture healing characterized radiographically

A

gradual disappearance of the fracture line without the formation of an external callus

27
Q

how is indirect/secondary bone healing radiographically characterized

A

early bone resorption and subsequent callus formation

28
Q

what radiographic changes are expected with indirect bone healing at 5-7 days

A

loss of definition of fracture edges

29
Q

when is callus formation seen with indirect bone healing

A

10-12 days

30
Q

when should the fracture line disappear on radiographs

A

30 days

31
Q

what is expected on radiographs 12 weeks postoperative with indirect bone healing

A

boney callus that bridges the fracture site and remodeling establishes the continuity of the cortex and medulla

32
Q

what will al callus look like in an immature animal with indirect bone healing

A

periosteal stripping → production of a callus away from teh bone as osteoprogenitor cells get pulled with the periosteum

33
Q

with regards to callus formation in mature patients under going secondary bone healing:
Periosteum as the tendency to ____ rather than _____ in mature animals

A

In mature patients the periosteum has the tendency to tear rather than to strip

34
Q

what is a characteristic radiographic finding with delayed unions

A

persistent fracture line with evidence of some non-bridging callus
The marrow cavity remains open without evidence of significant sclerosis of the bone ends

35
Q

what is a non-union fracture

A

fracture that fails to progress to osteosynthesis regardless of healing time

36
Q

what is a biologically viable non-union

A

biological enviornment of the fracture is adequate and a healing response occurs

37
Q

what are radiographic characteristics of a biologically viable nonunion

A

variable amount of callus but the callus fails to bridge the fracture gap

38
Q

describe a hypertrophic nonunion

A

usually shows well marked signs of healing but the process has ceased.
bone ends are enlarged and have an “elephant foot” appearance

39
Q

how is a slightly hypertrophic nonunion different than a hypertrophic nonunion

A

less periosteal reaction → horse hoof appearance

40
Q

oligotrophic nonunion

A

no radiographic signs of callus but are capable of biological activity
fracture ends are usually rounded and undergo decalcification

41
Q

management of a hypertrophic nonunion secondary to excessive motion

A

rigid fixation with dynamic compression to ensure axial load (i.e. plate fixation) is preferred and the fibrous tissue at the area of the fracture should be removed
re-establish medullary canal of host bone sections

42
Q

cause of oligotrophic nonunions

A

excessive motion and lack of cellular activity

43
Q

dystrophic nonunion

A

nonviable bone on one or both sides due to compromise to the vasculature of the bone

44
Q

necrotic nonunion

A

implies an infected section of bone, specifically a sequestrum

45
Q

defect non-union

A

fracture gap that is too large for normal biologic healing with the gap being filled with tissue other than living bone

46
Q

atrophic nonunion

A

occurs when dead bone of the fracture area is removed by the host without a healing or restorative process

47
Q

define malunion fracture

A

failure of mechanical reestablishment of the form and function of the fracture in which healing still occurs

48
Q

what constitutes minor angular limb deformities or minor shortening

A

10° or less in any plane
10% or less than the original length
Generally have a functional malunion

49
Q

what constitutes major angular limb deformities or major shortening

A

> 10° in any plane
10% or less than the original length
Usually functionally impaired

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