Ottobock’s Empower Ankle is a unique bionic ankle/foot that provides electric propulsion in addition to automatically adjusting foot position and resistance.
What’s On This Page?
- A Quick Look at the Empower Ankle
- Ankle Range of Motion (ROM)
- Ankle Accommodation
- Electric Propulsion
- Sensor and Microprocessor Capabilities
- Water and Dust Resistance
- Device Weight & User Weight Limit
- K-Level Rating
- User Software
- Compatibility with Bionic Knees
- User Feedback Survey & Results
- Video Reviews
- Considerations Before Buying an Empower Ankle
- Related Information
A Quick Look at the Empower Ankle
There is no better example of the Empower’s benefits than the following video of a double amputee walking, then running, up and down stairs.
In our opinion, this is astonishing. Imagine showing this to double amputees at the turn of the century and telling them that this was only a decade or two away!
This next video provides a good technical description of the Empower:
Ankle Range of Motion (ROM)
The reported ROM for the Empower Ankle is 22 degrees plantar flexion (foot pointed downward). Dorsiflexion (foot pointed upward) is entirely dependent on the foot component’s carbon spring.
The Empower Ankle automatically adjusts its foot stiffness in the heel strike portion of the Stance Phase. This ensures optimum shock absorption and foot loading.
It also adjusts its power generation during push-off at the end of the Stance Phase.
And we believe, but are not yet certain, that it adjusts the foot angle in the Swing Phase of the gait cycle, i.e. while the foot is in the air.
The Empower Ankle is the only bionic ankle/foot to offer a powered push-off feature, meaning it is the only one to provide net positive energy when walking. This occurs at the end of the Stance Phase and is especially beneficial to users when ascending stairs, ramps, and hills.
All other bionic ankles/feet rely on a carbon fiber foot to mechanically store and release energy, but this still results in a net energy loss because only part of the expended energy can be stored and reused with each step.
The Empower uses both a carbon fiber foot (the Taleo LP) and electric propulsion combined, giving it the best of both worlds.
Note that the Empower does not provide any push-off when descending stairs, ramps, or hills.
Sensor and Microprocessor Capabilities
With six sensors, two microprocessors, and the ability to make thousands of adjustments per second, the Empower Ankle will automatically adjust to most terrains.
The lithium-polymer battery used to power the Empower Ankle is generally good for eight hours of use depending on the level of activity. With the recent switch to the Taleo LP foot component, which offers improved energy storage and reuse, this may increase the number of hours per battery. Ottobock is currently gathering data on this and will adjust its specifications accordingly.
In any event, users generally carry a spare battery, which gives them more than enough battery power to last a full day.
The dual-bay charger can charge two batteries fully in 90 minutes.
Water and Dust Resistance
The Empower Ankle has an IP rating of 24. This means that it is protected against larger objects but not dust, and from water splashing from any angle but not water jets or immersion.
Device Weight & User Weight Limit
The Empower Ankle weighs approximately 2.14 kilograms with a normal footshell. This makes the Empower the heaviest of all bionic ankles/feet, approximately 600 grams heavier than its nearest competitor.
However, this is not a fair comparison. The Empower provides added push-off power via an electrical power system, whereas other bionic feet do not.
The best way to determine how the added weight and the push-off power offset is to examine the net impact of the Empower Ankle’s use on its wearer. In clinical studies, patients using an Empower Ankle were able to increase walking speed, reduce fatigue, and reduce the stress on other joints. This suggests that the added weight is not a problem. However, some customers disagree (see Considerations Before Buying an Empower Ankle).
The minimum user weight for the Empower Ankle is between 68 kg and 77 kg. The maximum weight is 130 kg.
The Empower Ankle is rated for K3 use.
For a thorough understanding of K-levels, please see the Amputee Coalition’s web page on this topic.
There is no user software for the Empower Ankle. Instead, setup software is provided to each clinician that allows the clinician to customize the ankle for each user.
Ottobock offers a three-year comprehensive warranty package on the Empower Ankle. This guarantees no repair costs during this period. The company also provides a free service inspection after 24 months, as well as a free service unit during repairs and/or service inspections.
The warranty can be extended to six years at the option of the user.
The best price estimate that we have for the Empower Ankle is $40,000 to $50,000 US inclusive of all clinical fees. This figure comes straight from its inventor, Hugh Herr, in a September 2020 interview.
Unfortunately, Mr. Herr also pointed out that there is still no reimbursement support for this extraordinary device from the Centers for Medicare & Medicaid Services (CMS). This means that only current or former members of the military, or those covered by the US Department of Labor’s Office of Worker’s Compensation Programs (OWCP), generally have access to the Empower.
To see how the price of the Empower compares to its competitors, please see our Bionic Foot Price List.
Compatibility With Bionic Knees
The Empower Ankle has been approved for use with the C-Leg, Genium, and Genium X3 bionic knees — all Ottobock devices.
User Feedback Survey & Results
Are you or have you previously been an Empower Ankle user? If so, please share your insights with others looking at the Empower as a possible prosthesis.
We do not yet have a sufficient number of survey participants to publish fair and accurate results for the Empower.
As soon as we do, we’ll update this section.
Sometimes, we run across videos created by patients or prosthetists that we think are worth sharing.
Here’s one from an end-user that we found to be quite thorough and genuine:
Considerations Before Buying an Empower Ankle
Compatibility, compatibility, compatibility.
We started out viewing the Empower Ankle as the ultimate bionic ankle/foot because we had never before seen amputees accomplish such remarkable feats with any other device. This remains a valid observation.
However, since then, we’ve received a lot of feedback from end-users that the Empower can be hit-and-miss. Some people absolutely love it; others find the increased weight and power augmentation to throw off their gait. This is why you must — and we emphasize must — insist on a free trial with a bionic limb before you buy it. If the team you’re seeing won’t arrange one for you, get another team. Don’t get stuck with the wrong device for years before you can change it!
Otherwise, the main drawback with the Empower Ankle is its high price or, more specifically, the lack of public and private insurance coverage for it.
For a list of competitor devices, see All Bionic Feet.
For a comprehensive description of all current lower-limb technologies, devices, and research, see our complete guide.
Click here for more information on Ottobock.