Lecture 14 2/13/25 Flashcards
What are the forces that act on bone?
-bending
-compression/tension
-torsion
How do IM pins neutralize the various forces on bone?
*+++ neutralization of bending
*no neutralization of rotation
*no neutralization of axial compression
*no neutralization of tension
How do interlocking nails neutralize the various forces on bone?
*+++ neutralization of bending
*++ neutralization of rotation
*++ neutralization of axial compression
*++ neutralization of tension
How do bone plates neutralize the various forces on bone?
*++ neutralization of bending
*+++ neutralization of rotation
*+++ neutralization of axial compression
*+++ neutralization of tension
How do ex-fixes neutralize the various forces on bone?
+(++) neutralization of bending, rotation, axial compression, and tension based on configuration and additional components added
What are the types of cerclage done?
-full cerclage
-hemi-cerclage
-inter-fragment cerclage
-tension band (most common)
What must be done for a cerclage wire to be placed?
must have 360 degree reconstruction of the cylinder of bone at the level the wire is to be placed
What are the characteristics of the twist knot method for applying a cerclage wire?
-weakest method
-ends of the wire wrap around each other
-pull up while twisting to tighten the wire
What are the characteristics of the loop knot method for applying a cerclage wire?
-uses a special wire type with a loop at one end
-requires a loop wire tightener to apply the wire
-can be applied as a single loop or a double loop
-double loop is the strongest method and only used in large animal
Which fractures can a cerclage wire be applied to?
long oblique fractures in which the shaft has been rebuilt with careful technique
What are the basic elements of an external fixator?
-fixation pins that attach the device to the bone
-fixation clamps that secure the fixation pins to the rods
-connecting rods that interconnect the fixation pins and span the structure
What are the characteristics of an acrylic column ex-fix?
-replaces the clamps and rods
-forms the frame of the ESF device
How many fixation pins should be placed for an ex-fix?
three pins in each major fragment
What is the far-near-near-far principle of fixation pin insertion?
-reduces the frame working length
-ensures there are not large spans of bone without pins that could increase movement
-want one pin near the fracture site, one pin far from the fracture site, and one pin in between at a minimum
How are the fixation pin insertion sites selected?
-selected to minimize the thickness of soft tissue being penetrated
-selected according to “safe corridors” based on tissue thickness, blood supply, etc.
What are the characteristics of a type 1a ex-fix?
-unilateral fixator
-half pins
-single plane
Identify the ex-fix.
type 1a
What are the characteristics of a type 1b ex-fix?
-unilateral fixator
-half pins
-two different planes
-30 to 60 degree angles
-most common in vet med
-can be reinforced with diagonal linkages
Identify the ex-fix.
type 1b
Identify the ex-fix.
type 1b with diagonal linkage reinforcement
What are the characteristics of a type 2 ex-fix?
-bilateral fixator
-full pins
-single plane
Identify the ex-fix.
type 2
What are the characteristics of a modified type 2 ex-fix?
-combines full pins with half pins
-reduces interference with soft tissue
Identify the ex-fix.
modified type 2
What are the characteristics of a type 3 ex-fix?
-bilateral fixator
-half and full pins
-two planes
-very rigid
-combines a type 2 frontal plane with a type 1 sagittal plane
Identify the ex-fix.
type 3
What are the characteristics of ex-fix frame stiffness?
increases with number of planes and number of sides
What are the characteristics of circular fixators?
-used for fractures and limb deformities
-most complex orthopedic implant
What are the ring types for circular fixators?
-full ring
-half ring
-extended ring
What are the characteristics of ring placement in a circular fixator?
-use very small pins under a lot of tension
-can put pins all over to increase the stability
What are the mechanical advantages of interlocking nails?
-intra-medullary location
-locking bolts
-stability based on locking efficacy
What are the benefits of intra-medullary location for the interlocking nails?
-large moment of inertia
-near bone neutral axis
-counteract bending
What forces are counteracted by locking bolts?
-compression
-torsion
Which fracture types can benefit from interlocking nails?
diaphyseal fractures of the femur, tibia, and humerus
What are the biological advantages of interlocking nails?
-nail insertion through remote incisions
-preservation of fracture hematoma
-preservation of periosteal blood supply
-very stable against all forces
