Throughout the world, there are millions of individuals who wear a prosthetic leg. And with so many living life as an amputee, there are bound to be more having issues related to their foot bumper or wedge than you would expect. As an amputee, you may find yourself experiencing things like, your walking is off, or it feels like you’re walking up or down a hill, maybe even your knee is buckling or your heel feels way too soft.
If this has been your experience, then odds are, you may have the incorrect foot bumper or need a wedge added or removed. Read on, because we are going to be showing you the top reasons why you need to use a correct foot bumper or wedge, why it is so important and what you should expect. But before that, for those who are new to this whole prosthetic thing, let’s go into what a foot bumper and wedge is.
What is a Prosthetic Foot Bumper or Wedge?
Bumpers are used to help improve your walking and alignment by changing the durometer or stiffness of a prosthetic foot. Likewise, wedges affect prosthetic alignment of the heel or toe of a carbon graphite foot. Both the foot bumper and wedge are tools allowing micro adjustments to be made in how the foot performs and reacts to obstacles like curbs and uneven terrain. Consider these tiny rubber “tools” as a way to further improve your walking and secondly personalize your prosthetic leg. Now, it is important to note that not all feet are designed the same and may not use a bumper or allow for a wedge, and with that in mind there are some things you should know to ensure you are wearing the correct foot bumper or wedge.
- Different types of feet contain bumpers or wedges. Typically carbon feet use wedges and single axis or multi-axis feet incorporate bumpers into their designs.
- A single axis foot has a front and back bumper to control of ankle motion and any indirectly knee flexion and extension
- Wedges for Carbon feet are glued in the back of your foot between the toe and heel spring to affect the stiffness of the heel and move your center of gravity (COG) forward over the toe. Moving your body weight forward will indirectly affect your knee and make it easier to bend when your heel contacts the floor.
Why is this Important?
Now, while most people live busy lives and would rather deal with bumper or wedge related issues later, addressing these issues today can save your lower back or prevent inadvertent knee buckling.
If the posterior bumper is too stiff or a wedge is too thick, it's going to cause a flexion moment at the knee, as well as create a torque moment inside your below knee (transtibial) socket along the bottom of your tibia. In plain english, this means your foot may twist the wrong way or possibly your knee will abruptly flex, which is not good for you or your prosthetic limb.
In an above-the-knee prosthetic socket, you may experience abrupt knee flexion. And if the anterior bumper was too soft, you might see a drop-off at the end of stance phase, what many Prosthetists refer to as “walking down a hill.”
This means that you would have limited push-off and burn a lot more energy than necessary. For example, when walking, as you came over the toe, the ankle would feel too soft. Or think of it this way; during “heel strike” the back bumper is controlling the descent of the foot to the floor and the anterior bumper is controlling the forward movement of the pylon as it comes over your prosthetic foot.
How to Know if You Need a Different Durometer Bumper or Wedge Thickness?
Now that you know more about a foot bumper and wedge and why is it important to have the correct one, the next important thing you should know is if you need to update either.
So how do you know if you need a different bumper or wedge? If your prosthetic leg is having one or more of these issues, you may need to change your bumper or wedge:
- Your heel is too bouncy and mushy
- Your knee hyperextends or it doesn't flex the right way.
- When you place your heel on the ground, most prosthetic knees should flex 5 degrees, give or take. If your knee doesn't, than this will make it harder for you to get to that phase of walking where your entire weight is on your prosthesis, as forces are causing your knee to travel in the wrong direction.
- Your toe or front bumper is stiff, making it feel like you're climbing a hill.
- While it may be easier to go down hill, you’ll be unable to load the toe enough to get the full energy storage capabilities of your foot. Now, on the flip side, your toe or front bumper may be soft, which will make you feel a drop off, causing you to lose any energy return your foot may provide. You may also find it difficult to push off which will drain even more energy, making it that much harder to climb a hill. However, if you experience knee buckling, as an above-knee amputee, your heel wedge may be too thick or back bumper is too hard.
What to Expect After Installation?
Now that you have learned all about bumpers and wedges, it's time to visit your Prosthetist. So, what exactly should you expect after installing the correct bumper or wedge? The first thing you should expect is to feel less tired at the end of the day, even if you walked farther than you have before. Next is that the stiffness in your toe should be the appropriate amount so that it will allow you to load it more effectively giving you a smoother gait pattern while not taking up too much of your energy. Lastly, for people with above knee prosthesis, it will create less knee flexion moments which lessens the chance your prosthetic knee will inadvertently buckle and cause you to fall.
In conclusion, we will end with some tips and tricks to ensure you get the most out of your prosthesis. Although it's a constant process, you must always remember to have your prosthesis fine tuned to maximize its potential. Now, if your prosthesis is a few years old, it might be best to bring it in for a full inspection. As the years pass, you may have lost or gained weight, which may negatively affect the function of your prosthesis. Nevertheless, it is always a great idea to have your prosthesis go through a full inspection at least once a year to ensure it’s working properly. If you’re unsure whether your foot uses a bumper or has the ability to add a wedge, feel free to leave a comment below to see if there is one available for your foot model. Cheers!