46. malunion delayed union nonunion Flashcards Preview

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Flashcards in 46. malunion delayed union nonunion Deck (18)
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1
Q

what is osteosynthesis

A

healing of bone through surgical intervention with an implantable device

2
Q

mechanical failures leading to malunion, delayed union, non union

A
  1. inadequate proximity of fracture ends (inadequate reduction)2. forces and resultant motion of fracture (inadequate stabilization)
3
Q

healing that occurs with intolerable form or function is also known as

A

malunion

4
Q

T/Fbone is formed on the outside of a callus under tension; chondrogenesis is favored in the center of the callus under compression

A

Truebone is formed on the outside of a callus under tension; chondrogenesis is favored in the center of the callus under compression(theory behind distraction osteogenesis—bone is formed under tension)

5
Q

which type of connective tissue is most tolerant to strain

A

most tolerant = fibrous tissuefibrous tissue > cartilage > bone (2%)

6
Q

T/Flarge gap–low strain results in inhibition of callus and potentially delayed healing

A

small gaps–high interfrag strain results in calluslarge gap–low strain results in inhibition of callus and potentially delayed healing

7
Q

what his stress protection phenomenon

A

inhibited healing of fracture bc too little strain prevents callus formation and hinder mechanical signaling for the propagation and stimulation of bone formation

8
Q

T/F Strains of 5-10 % are generally considered adequate

A

TRUE

9
Q

essential bone morphogenic protein

A

BMP 2

10
Q

what is plate luting

A

technique in which PMMA is placed btwn bone and plate to fill in congruencies and providing a conduit for compression btwn bone and plate

11
Q

area of bone responsible for housing principle mesenchymal bone cell

A

cambium layer of the periosteum houses mesenchymal stem cells

12
Q

mechanical causes of delayed union

A

–excessive fracture gaps–motion at fracture site

13
Q

biologic causes of delayed union

A

–intrinsic factors of the patient and/or fracture(inadeqaute cellular activity)

14
Q

treatment options for delayed union

A

use strategies to enhance the biological and mechanical needs–BMP–demineralized bone matrix–autogenous cancellous bone graft–adjust mechanical stiffness if needed

15
Q

what is a nonunion

A

fracture that fails to progress to osteosynthesis regardless of the healing time

16
Q

categories of nonunion

A

viable (adequate biologic environment)1. hypertrophic (elephant)–excessive motion2. moderately hyper trophic (horse)2. oligotrophic–loose implants in the area of healing fx nonviable (biologically inactive)1. dystrophic (nonviable bone on one or both ends)2. necrotic (sequestrum/involucrum)3. defect (too large gap)4. atrophic (dead bone is removed without healing–resorption)

17
Q

treat viable nonunion

A

usually need rigid stabilizationneed to rid hypertrophic callusremove any loose implantsdrill hole into each prox/distal medullary cavity+/- graft, DPM, BMP

18
Q

Treat nonviable nonunions

A

remove all non viable bonestabilizationgrowth factors, grafts +/- amputation

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