Kapitel 42 – External fixation Flashcards
Whats the difference between positive and negative profile pins?
Positive-profile pins have a single diameter solid shaft, with threads that are rolled onto the end or center of the shaft, such that the outside diameter of the threaded portion is larger than the diameter of the rest of the shaft
Negative-profile pins have threads cut into the pin such that the outer diameter of the threaded portion is the same as that of the shaft, and the core of the threaded portion is of a smaller diameter.
What is the average increase in the ultimate pin-strength in a the negative-profile Duraface pin, compared to the corresponding positive-profile pin?
a. 26%
b. 54%
c. 40%
d. 73%
54%
What is a Type 1b fixator frame?
a. Unilateral, biplanar
b. Bilateral, biplanar
c. Bilateral, uniplanar
d. Unilateral, uniplanar
Unilateral, biplanar
What does articulation and diagonals refer to? Which one add more stability?
Articulations: Interconnecting bars at one end of the fixator that do not cross the fracture gap
Diagonals: interconnecting bars that do cross the fracture gap. Add more stability.
What should de diameter of acrylic connecting bar be as a general recommendation? And the diameter to reach the same stiffness as a stainless steal bar?
a. The diameter of the acrylic bars should be 2 to 2.5 times the diameter of the bone
b. 3-4 times bigger than the diameter of the stainless steel to reach the same stiffness.
What is “Period of latency” and for how long is it usually? And what is the appropriate rate of distraction?
It is the period after an corrective osteotomy where the bone is left stable over the course of few days. This delay, called the period of latency, is necessary for the formation of a fracture hematoma, which is the location where bone regeneration occurs. The length of time the osteotomy is held static in latency varies with patient age, location in the bone, and healing potential, but is usually between three and five days. Used during distraction osteogenesis.
1 mm/day
How many pins should be placed per bone segment proximal and distal to the fracture?
3-4 pins
In what order are the pins usually inserted?
The two far pins first, followed by the near pins
The general recommendation is to place pins three-fourths of the bone diameter away from adjacent joints and one-half of the bone diameter away from the fracture line.
What is the recommended size of the pin?
the pin diameter should not exceed 25% of the diameter of the bone.
What is the general rule conserning timing for destabilization of the frame?
a. 4 to 6 weeks for young dogs
b. 6 weeks for adult dogs
c. 8 to 10 weeks for older dogs and cats
How should pins be places in the vertebral column and directed in what angle?
Placed in the body of the vertebra and within a range of 45 to 60 degrees from the sagittal plane
