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