17 Oct ITS BONE BREAKING TIME!
Today we are going to discuss how we decide on where we break the bone and what size and length of PRECICE nail we will use.
It is very important to calculate the right location to break the bone. The way we decide on where we break the bone depends on a few factors.
- We want to be in an area of the bone as close as possible to the narrowest point (called the isthmus) to avoid having any kind of deformity around the nail.
- We want to be sure the nail in the part under the break will be strong enough to support 8cm of length, so we use a formula to calculate how much nail we need below the break (desired length + 5cm + 3cm).
- We look at the side view xray (called lateral or sagittal xray) to assess where the bow of your femur bone is located to make sure we break the bone close to this area.
To decide on the length and the size (diameter) of the PRECICE nail that is right for you, we consider the location where we are bone breaking, making sure that it is as close as possible to the narrow part of the bone called the isthmus. We often make this decision based on your calibrated radiographs by drawing lines on your radiographs, we call this preoperative planning.
Pink line = 275mm PRECICE nail
Blue line = 160mm from end of the nail
(based on above calculation 8+5+3 = 16cm)
Therefore, osteotomy will be at yellow line.
If yellow line location is not to our liking, we can calculate using a shorter (245mm ) or longer (305mm) nail, until we are satisfied with the location of our osteotomy.
For selecting Nail Diameter
Available sizes are 8.5mm, 10.7mm and 12.5mm
Most patients get a 10.7mm nail, unless they have a very big canal
We calculate the size based on the width of your bone at the isthmus (narrowest part of the bone on both AP and Lateral radiographs)
We prefer to use at least a 10.7mm nail as the weight bearing capacity is the same as the 12.5mm nail
The 8.5mm nail is mainly used in pediatrics
We look at the outer diameter = red line = example 21mm
And the inner diameter = green line = example 12.5mm
It is recommended to have at least 3-4mm of cortical bone left after reaming (preparing canal for the nail)
For a 10.7mm nail we would ream the canal to at least 12.5mm
this example, the patient would do well with a 10.7mm nail
If you got all that, amazing! Now you can tell me what size and length of nail you need at your in person visit!