Knee bone not connected to the ankle bone Flashcards
Another consideration with high energy fractures unrelated to the fracture site?
Neurologic damage
Crepitus
Grating sensation- joint surfaces or bone ends together
When taking radiographs of limbs, two considerations
Orthogonal and contralateral limb for comparison
Comminuted, Closed, Butterfly, Mid-femoral diaphysis, 100% displacement (cranio-medial)
Describe the fracture
Simple, closed, short-oblique, mid-tibial diaphysis, 100% displacement (cranio-medially)
Why did the bone fragments displace in this fashion?
Contraction of local dominant muscle group- modified slightly by fracture configuration
Down sides to surgery and implants
Interfere with soft tissues with interferes with healing, allowing bacteria in, disrupts haematoma (which is part of the healing process)
Plate fixation alone (bone plating)
Counteract all of the fracture forces more or less however, they aren’t a great idea alone often.
External Skeletal Fixation
Minimally invasive approach.
Is the femur a simple or complex fracture?
Complex. A lot of soft tissue, so do not want to put external skeletal fixation pins. Inability to immobilize hip.
What are the 4 As
Alignment, Apposition, Apparatus (plate rod combination), Activity
Why can’t we push the pin more distally in the femur?
Canine femur is not straight (cat femurs are)
When would we radiograph a second time to check on healing with the plate rod combo (fractures in general)?
6-8 weeks (no less than 3 weeks unless there is a problem)
Minimum number of screws
5 cortices either side with 2.5 each. (When you drill through the bone- each screw is going through 2 cortices)
What type of bone healing?
Indirect bone union- gap plus relative instability will preclude primary healing.
Primary bone healing requires anatomic apposition and compression with fracture gaps < 1 mm
Callus will be evident
Tibial fixation- what was used initially?
Plate fixation. Load share between the tibia and the implant. Did not get enough compression. Therefore high interfragmentary strain. 2 Screws close to the fracture site- which concentrates stress. Trying to bring the bones together.
NOT sufficiently rigid- relatively high motion with a small fracture gap- creates high interfragmentary strain.
What type of bone healing is likely to occur at this fracture site? Tibial bone healing
Direct bone union (pressed up against each other, rigid and stable)
Rigid stabilisation with some load sharing
Intrerfragmentary strain < 2%
Fracture gap < 1 mm but too much for primary contact healing
9 weeks later Fritz is 5/5 lame and completely non weight bearing. Repeat radiographs show plate failed (cyclic metal fatigue) at the fracture site and through the screw hole. We see callus on the radiograph- Callus only forms if you have INDIRECT bone union. So this tells us our aims did not work.
Why did high interfragmentary strain occur?
Lack of load sharing.
Interfragmentary Strain
Problem is exacerbated when fracture gap is small. Because relative deformity is MUCH higher.
** Strain is HIGH when CHANGE IN LENGTH IS HIGH (instability)
** It is also high when the initial gap is small
New bone can only form under < 2%
Strain = change in gap width (.5 mm)/ Original width (2 mm)
Original width is AFTER we put the plate on
Change in the width is what happens after we repaired it to the original gap after the patient WALKS ON THE LEG
** IF original width is higher, strain is higher
** if change in width or instability (motion at the fracture site) is HIGH- then strain is HIGH
With the second repair on the tibial fraction, what was done differently?
Plate rod construct
Place screws farther apart in order to spread the plate stress out over a much longer length of plate and reduced the risk of failure.
