46. malunion delayed union nonunion

Question 1

what is osteosynthesis

Answer 1

healing of bone through surgical intervention with an implantable device

Question 2

mechanical failures leading to malunion, delayed union, non union

Answer 2

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

Question 3

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

Answer 3

malunion

Question 4

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

Answer 4

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)

Question 5

which type of connective tissue is most tolerant to strain

Answer 5

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

Question 6

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

Answer 6

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

Question 7

what his stress protection phenomenon

Answer 7

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

Question 8

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

Answer 8

TRUE

Question 9

essential bone morphogenic protein

Answer 9

BMP 2

Question 10

what is plate luting

Answer 10

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

Question 11

area of bone responsible for housing principle mesenchymal bone cell

Answer 11

cambium layer of the periosteum houses mesenchymal stem cells

Question 12

mechanical causes of delayed union

Answer 12

–excessive fracture gaps–motion at fracture site

Question 13

biologic causes of delayed union

Answer 13

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

Question 14

treatment options for delayed union

Answer 14

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

Question 15

what is a nonunion

Answer 15

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

Question 16

categories of nonunion

Answer 16

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)

Question 17

treat viable nonunion

Answer 17

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

Question 18

Treat nonviable nonunions

Answer 18

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