Am I a Candidate?

HyProCure sinus tarsi implant

Who can be a candidate?

The insertion of HyProCure into the sinus tarsi space is rather simple, once the surgeon learns the correct technique. The complicated part is to figure out who is a candidate for this life changing procedure. There are going to be several requirements that must be met, but then there is a second set of issues that must also be discussed.

1. Age requirements

The individual must have already celebrated their 3rd birthday. This ensures that the chamber forming the sinus tarsi space is bone not soft but “hard” bone. Initially, bones are soft while they are growing and shaping. It has been found the walls of the sinus tarsi chamber do not become hardened (ossified) until three years of age. Typically, most surgeons will want to wait until the child is several years older. There are no other age restrictions, there is no cutoff date as long as the ankle bone can be repositioned on the heel bone and the sinus tarsi space is open. The oldest person on record to have a HyProCure inserted into their foot was 94 years old.

Age requirements for HyProCure

2. Clinical Findings

These are observations made by looking at the feet and examining the motions of the hindfoot bones. There are 3 different parts of this examination: no weight on the feet, standing on the feet, and walking. It is very important that the entire foot structure is evaluated, but the purposes of determining the very basics on the criteria is met for the possible recommendation of EOTTS-with HyProCure.

Clinical findings for recommendation of EOTTS-with HyProCure

No weight on the feet (non-weightbearing examination)

The doctor will hold the heel in one hand and push the outer part of the forefoot up and toward the leg bone. This simulates the motion of the ankle joint while walking, specifically pronation of the talotarsal (including the subtalar joints). The normal amount of motion should be very slight, just a few degrees. A pathologic amount of motion is more than 8 degrees (it is difficult to accurately see what 6 degrees is or 8 degrees) this is an observation only.

Doctor conducts no weight on the feet non-weightbearing examination

Here is a video that shoes the difference between an acceptable amount of the sub-ankle bone motion on the left and excessive motion on the left.

Another observation that can be made is to look at the inner arch of the foot. The absence or present of arch collapse does not really matter because many people with ankle bone instability also have a somewhat appearing arch. That is one of the main reasons why we don’t like to refer to this condition as a “flat” foot.

Arch with no weight on the foot and loss of inner arch height

Everyone with a flatfoot has ankle bone misalignment, but not everyone with ankle bone instability has a flatfoot.

Standing part of the exam

The doctor will look at the alignment of your lower leg with the front of your foot.

Corrected ankle bone alignment front view

Ankle bone alignment front view:

Start with your ankle bone aligned on the heel bone (corrected ankle bone alignment). The forefoot should be aligned with the lower leg.

Full weight placed on the foot (uncorrected ankle bone alignment)

Then, you just stand with full weight placed on the foot (uncorrected ankle bone alignment). This is also called “relaxed” stance position, as you just normally stand.

Notice how the inner ankle is turned inward and the forefoot is turned outward. The only difference between the aligned and misaligned foot, is the alignment or misalignment of the ankle bone on the heel bone. The open space of the sinus tarsi or the closed spaced of the sinus tarsi.

There are some situations where the lower leg and foot appear to be aligned when standing, however ankle bone instability appears upon walking.

That’s because the weight is being placed on both feet and the true ankle bone instability does not appear until walking. If the ankle bone cannot be repositioned on the heel, then chances are not very good that you will be a candidate for the HyProCure solution.

Observe the inner arch of the foot.

Look at the inner arch of the foot with ankle bone in the corrected position and compare with full weight on your foot, how you normally stand. Can the arch height be recreated? Remember, that many people with ankle bone instability have a normal appearing arch. This condition is about ankle bone displacement not fallen arches or flat feet.

Corrected ankle bone alignment
Uncorrected ankle bone alignment

Here is a video showing that arch is recreated once the ankle bone is placed back on to the heel bone. This is a very good indication that HyProCure could be an option, but this finding along does not guarantee. X-rays must be taken to truly determine if you are a candidate.

Alignment of the back of the heel/ankle area

Next is to take a look at the back of the heel to see if it is angled outward or aligned with the lower leg. There are some physicians who thought it was the heel that turned outward that forced the ankle to turn inward. They got it completely wrong. That because not everyone with ankle bone instability has a heel that turns outward, called heel or calcaneal valgus.

Ankle bone is aligned on the heel bone
Ankle bone is partially dislocated on the heel bone

Too many toes sign

There is one last finding called “too many toes” sign. Look from the back of the foot to the outer forefoot. Usually, you should only see the 5th toe. If you can see more than one toe than this would be a positive “too many toes” sign. This is also directly related to ankle bone instability. You see too many toes when this person is standing in a relaxed position. The ankle is then repositioned on the heel bone and the “too many toes” sign disappears.

normal foot and too many toes sign foot

This video shows the appearance and disappearance of the “too many toes” sign.

Walking / Gait Analysis

The last step during the examination is to have you walk. This is called the “gait” cycle. There are certain parts of the walking cycle when your ankle bone should be in-line with your leg and there should only be a very brief time when the ankle bone turns inward, right after your heel hits the ground.

If your ankle bone turns inward to long, this is called over-pronation. Pronation is a complex series of the motions between the hindfoot bones. Medically, this is called hyperpronation. When using the prefix hyper- in describing the motions of the feet/body it means excessive or too much motion. This over- or hyperpronation can only occur due to ankle bone instability.

There are many different components to watching you walk but the main one to show that you have an ankle bone instability issues are similar to standing phase of the examination.

Common findings of ankle bone instability include:

  • Outward turning of the heel
  • “Too many toes” sign
  • A prolonged/excessive duration of the hindfoot pronation
  • Twisting of the forefoot once your heel lifts off the ground

All of the clinical observations provide a clue that there is a possible ankle bone instability condition. The only way to really know for sure can be determined with x-rays.

X-ray Analysis

The only way to diagnose ankle bone misalignment is by taking x-rays of your feet while you are standing. There are many different findings that must be taken into consideration. Your doctor will look at many other parts of your foot to determine if you are candidate for HyProCure. We will only show you the most important findings that your ankle has a stability and alignment issue. These images are for illustrative purposes only. This site is not meant to diagnose your specific condition.

There is a difference between ankle bone misalignment, a condition where the ankle bone is partially dislocated on the heel bone, verse ankle bone instability. The misalignment can be fixed condition where the ankle bone cannot be repositioned on the heel bone. This type of condition can only be fixed with more aggressive surgery and HyProCure would not be a treatment option. There is an exception, that is when there a partial fusion between the ankle and heel bones. That is something that develops called a tarsal coalition. There are situations where it is possible the surgeon can remove that partial fusion between the two bones and insert HyProCure to maintain the stability and alignment of the ankle bone.

To diagnose ankle bone instability, we would have to see the ankle bone in an abnormal alignment on the hindfoot bones compared to x-rays with the ankle bone placed into its normal alignment.

We strongly recommend that you have 2 sets of x-rays taken of your feet to see if you are a candidate for HyProCure. The first set is with full weight on your feet, in relaxed position, how you normally stand. The second set is with your ankle bone realigned on your heel bone. This will show the realignment of the ankle bone and the reopening of the sinus tarsi space.

Relaxed Stance Postion - Just how you usually stand compared with Corrected stance position - Ankle bone is placed back into alignment
Relaxed foot Uncorrected Stance Postion compared with Corrected Stance Position

Side / Lateral View X-rays

This x-ray was taken without the person’s standing on their foot. You will see the ankle and heel bones and the sinus tarsi space open.

Side foot standing x-ray - ankle bone and heel bones and the sinus tarsi space open
Side foot standing x-ray - corrected ankle bone position

Here we can see an acceptable hindfoot alignment with a stable ankle bone.

Now compare that x-ray to this one. Same person, they just relaxed their ankle bone.

Side foot standing x-ray - uncorrected ankle bone position relaxed standing

We see how the ankle bone has partially dislocated forward and downward.

The ankle bone is pushed downward, and this is what causes the arch to collapse. See how the ankle bone is elevated on the corrected ankle bone position image? Finally, see how the sinus tarsi space is reopened? These images give us an indication that HyProCure is a viable option.

Side foot standing x-ray - corrected ankle bone position - aligned ankle bone compared with uncorrected ankle bone position - ankle bone instability

One of the best ways to determine ankle bone stability or instability is with weightbearing fluoroscopic imaging.

This is a dynamic x-ray so that you can see the motion of the ankle bone. A doctor can use the comparison x-rays, but it is important to see that the ankle bone can be replaced on the heel bone. If the ankle bone cannot be repositioned on the heel bone, then HyProCure cannot be inserted to keep the ankle bone aligned.

Here is another example of someone standing on their foot.

They have their ankle bone stabilized on the heel bone, then they go into relaxed stance showing how ankle bone instability. Notice the ankle bracelet to show the twisting and turning of the hindfoot.

There is a limitation on how much correction can be achieved with HyProCure. You doctor will be able to tell you if you are a possible candidate for HyProCure. The more severe the ankle displacement, the less likely you will be a candidate.

Mild, moderate, severe ankle displacement

Top-Bottom View X-rays.

Both views are needed to determine if the ankle bone instability is present. Sometimes, it is seen on the sideview and not the top view, or it could be the opposite where it is seen on the top-bottom view and not the side view.

First, let’s see what an aligned and stable foot looks like. Here we see the person standing with full weight on the foot. The bisection of the ankle bone provides us with the answer of an alignment or misalignment. The bisection is a line splitting the side-to-side portion of the ankle bone right down the middle. It should extend into the long, thick first metatarsal bone area. Ankle bone misalignment can be diagnosed any time that line-bisection passes to the inside of the foot without touching the first metatarsal bone.

Top-bottom view relaxed standing x-ray - stable and aligned ankle bone

Below we see an example of a misaligned ankle bone.

The red arrow bisection of the ankle bone is lined up on the wrong side of the first metatarsal bone. The only way this can happen is if the ankle bone is partially dislocated on the heel bone. This is considered a transverse plane deformity and is responsible for the twisting of the knee.

Top-bottom view relaxed standing x-ray - misaligned ankle bone

Remember that this image only tells us the ankle bone is misaligned, it does not tell us that ankle instability is present. A second x-ray would have to be taken to document the normalization of the ankle bone alignment.

Here you can clearly see the difference between aligned and misaligned ankle bone.

Top-bottom view relaxed standing x-ray - aligned ankle bone compared with misaligned ankle bone

Below is a video that shows what a stable and aligned ankle bone looks like with weightbearing fluoroscopt. There should only be a minimal amount of ankle bone motion.

Compare that image to ankle bone instability. This clearly shows the ankle bone in the aligned position and then the ankle bone partially dislocates on the heel bone.

Here is the combination of the side and top-bottom view of ankle bone instability. The ankle bone is partially dislocating on the heel bone and is able to be repositioned on the heel bone.

There are degrees of severity just like the side view x-rays.

Top-bottom view relaxed standing x-ray - normal, mild, moderate, severe ankle bone alignment

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