Delayed unions, nonunions, malunions

Question 1

Which is false?
A Larger strain seems to encourage stronger healing in smaller gaps
B Less strain is tolerated in larger gaps
C Strains of 30% have a positive effect on the healing of 1 mm diaphyseal gaps compared with 7% strain
D 7% strain had a severely negative influence on bone healing in larger 6 mm fracture gaps.

Answer 1

D (30%)

Question 2

Which is true?
A Stress protection is when healing of fractures is inhibited if too much strain is imparted to the healing fracture callus.
B Limiting strain to less than 1% to 2% should be avoided
C With ring fixators, as as loads decrease, the stiffness and strength of fixation would increase.
D With regard to simple axial loading and fractures with a few to several millimeters of gap or comminution, strains of 2% to 3% are generally considered adequate.

Answer 2

B is true

A (too little)
C loads increase–> strength inc.
D (5-10%)

Question 3

Which of the following is false?
A The bone marrow is the only source of stem cells for bone.
B Large amount of motion produce a large callus and therefore more time
C Intrinsic factors of the patient and fracture are the most common causes for delayed union
D Rads can begin as early as 3-4 weeks to detect delayed healing

Answer 3

A (FALSE cambium layer of periosteum is important source)

Question 4

a. _______________ deposit bone matrix in the form of thin layers known as ________________?

Answer 4

Osteoblasts, lamellae

Question 5

In the process of deposition of the matrix, osteoblasts become encased in small hollows with the matrix called?

a. Canaliculi
b. Lacunae
c. Haversian canals
d. Volkmanns canals

Answer 5

B

Question 6

T/F: lamellae in trabecular bone do not form Haversian systems?

Answer 6

true

Question 7

What are 2 types of viable non-unions? why do they occur?

Answer 7

Hypertrophic: motion
Oligotrophic: loose implants –> poor vascularity –> lack of cellular activity

Question 8

list 3 nonviable nonunions? why do they occur?

Answer 8

Dystrophic: compromise of vasculature
Necrotic: infected
Atrophic: dead bone removed without replacement (defect: big gap)

Question 9

Which of the following is not a method for treatment of nonunion and delayed union fractures?
A. Extracorporeal Shock Wave therapy
B. Pulsed Electromagnetic field
C. Low-intensity pulsed ultrasonography
D. External coaptation

Answer 9

D.