Internal fixation: pins, wires and interlocking nails Flashcards
When is internal fixation warranted?
when external coaptation can’t be use or has distinct disadvantages
What bones should internal fixation always be used?
humerus and femur
What kind of fractures should usually be fixed by internal fixation?
- oblique
2. comminuted
What do intramedullar pins control?
bending. but need help for controlling others
What do interlocking nails, external skeletal fixators and bone plates control?
all the forces that act on the fracture if the correct hardware/configuration is used
What is internal fixation?
fracture repair by means of hardware that attaches directly to the bone
What are fractures for which internal fixation is much better than external coaptation?
- open fractures
- fractures of femur, humerus, pelvis
- articular fractures–perfect reduction–early joint movement
- oblique or comminuted fractures–control commpresion
- fractures in which primary force acting is tension–olecranon, calcaneus, greater trochanter
What forces to intramedullar pins control?
bending
What is an intramedullary pin
a rod that stabilizes broken bone by passing longitudinally within medullary canal, v/ close to neutral axis
what is a K-wire
A small pin
What are 4 advantages of intramedullary pins
- availability
- axial alignment
- bending control
- minimal to moderate blood supply disruption
What are 4 advantages of intramedullary pins
- availability
- axial alignment
- bending control
- minimal to moderate blood supply disruption
What are 4 disadvantages of intramedullary pins?
- pins control only bending
- can’t always anatomically repair comminuted fractures
- potential for injury to surrounding structures–sciatic nerve
- not good for skull, pelvis. RADIUS
What are two ways to place an IM pin
- normograde placement-
2. retrograde placement
What is normograde placement?
reduction of fracture then pin run down middle–for tibia, often ulna, humerus
What is retrograde placement?
pin inserted in the proximal fragment, then pull out proximal end. –easier to get in canal. NOT tibia. usually in femor
What is retrograde placement?
pin inserted in the proximal fragment, then pull out proximal end. –easier to get in canal. NOT tibia. usually in femor
What should the diameter of an IM pin be?
60% the diameter of the medullary canal at skinniest point of the bone–still allows blood supply UNLESS combined with bone plate or external fixation (50% then)
How should the IM pin be positioned?
run the length of the bone and spear the cortex at the bottom but do not penetrate it
What is cross-pinning?
NOT Im pins. The pins are placed so they cross the fracture line and two cortices
What are forces neutralized by cross pins?
- torsion
- compression
- moderate bending
When is cross pinning appropriate?
for repairing physeal or very distal/proximal metaphyseal fractures
What are wiring techniques used for?
- prevent propagation of fissues
- reconstruct fragments
- hold fracture in reduction until definitive repair
- help control torsion and compressive along with IM pin
What is a full cerclage?
the passing wire around the circumference of bone to stabilize a fracture
What is the only appropriate use of full cerclage?
for use in long oblique fractures. the cylinder of bone must be reconstructed! and must be TIGHT
Why must full cerclage wires be tight?
because if they wiggle they distrupt blood supply to the fracture –thus MUST be perpendicular to bone and not on tapering areas unless anchored
What is interfragmentary wiring?
placing wires through two bone fragments to connect them
Where can interfragmentary wiring be used?
transverse, short and long oblique fractures. can also use with cross pins/skewer pins
Where can interfragmentary wiring be used?
transverse, short and long oblique fractures. can also use with cross pins/skewer pins
What is tension band wiring?
It is wiring to counteract tensile force. it transforms bad tensile forces into good compressive forces. Parallel pins are placed perpendicular to the fracture line. A figure of 8 wire is passed through a distal hole and around the pins and tightened
What is an interlocking nail?
a rode placed in the medullary canal and fixed in place with scews or bolts that pass from the outside of the bone, through holes in rod and back through cortex
usually left in place
What forces do interlocking nails control?
- bending!
- compression (scews)
- torsion (screws)
What are the advantages of interlocking nail?
- can fix comminuted fractures without requiring anatomic reconstruction
- less disruptive than plate placement so only moderately disrupts blood supply
- cheaper than bone plate
What are the limitations of interlocking nail?
- need a bone protrusion to introduce into the bone: femur, humerus, tibia NOT RADIUS
- require a box of special equipment
- big learning curve
What is an IM ESF tie-in
leave IM pin protruding. pass transfixation pin and external fixating bar (tie-in)
IM, external skeletal fixator
What is a plate-pin combination?
have a pin AND a bone plate
gives superior bending control–can also drop IM pin diameter to 50% and only need 1 screw per fragment going all the way across
What is a plate-pin combination?
have a pin AND a bone plate
gives superior bending control–can also drop IM pin diameter to 50% and only need 1 screw per fragment going all the way across. For the skinny diaphyseal parts just need to go into one cortex
