Knee bone not connected to the ankle bone

Question 1

Another consideration with high energy fractures unrelated to the fracture site?

Answer 1

Neurologic damage

Question 2

Crepitus

Answer 2

Grating sensation- joint surfaces or bone ends together

Question 3

When taking radiographs of limbs, two considerations

Answer 3

Orthogonal and contralateral limb for comparison

Question 4

Answer 4

Comminuted, Closed, Butterfly, Mid-femoral diaphysis, 100% displacement (cranio-medial)

Question 5

Describe the fracture

Answer 5

Simple, closed, short-oblique, mid-tibial diaphysis, 100% displacement (cranio-medially)

Question 6

Why did the bone fragments displace in this fashion?

Answer 6

Contraction of local dominant muscle group- modified slightly by fracture configuration

Question 7

Down sides to surgery and implants

Answer 7

Interfere with soft tissues with interferes with healing, allowing bacteria in, disrupts haematoma (which is part of the healing process)

Question 8

Plate fixation alone (bone plating)

Answer 8

Counteract all of the fracture forces more or less however, they aren’t a great idea alone often.

Question 9

External Skeletal Fixation

Answer 9

Minimally invasive approach.

Question 10

Is the femur a simple or complex fracture?

Answer 10

Complex. A lot of soft tissue, so do not want to put external skeletal fixation pins. Inability to immobilize hip.

Question 11

What are the 4 As

Answer 11

Alignment, Apposition, Apparatus (plate rod combination), Activity

Question 12

Why can’t we push the pin more distally in the femur?

Answer 12

Canine femur is not straight (cat femurs are)

Question 13

When would we radiograph a second time to check on healing with the plate rod combo (fractures in general)?

Answer 13

6-8 weeks (no less than 3 weeks unless there is a problem)

Question 14

Minimum number of screws

Answer 14

5 cortices either side with 2.5 each. (When you drill through the bone- each screw is going through 2 cortices)

Question 16

What type of bone healing?

Answer 16

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

Question 17

Tibial fixation- what was used initially?

Answer 17

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.

Question 18

What type of bone healing is likely to occur at this fracture site? Tibial bone healing

Answer 18

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

Question 19

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?

Answer 19

Lack of load sharing.

Question 20

Interfragmentary Strain

Answer 20

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

Question 21

With the second repair on the tibial fraction, what was done differently?

Answer 21

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.