The Meridium Foot is Ottobock’s less-expensive cousin to its premium Empower Ankle in the microprocessor ankle/foot category. With its 36.5 degrees range of motion, 4-axis kinematics, and automatically adjusted flexion resistance, it’s yet another worthwhile option for those looking to upgrade to a microprocessor ankle/foot.
A Quick Look at the Meridium Foot
Although this video is from Ottobock and therefore somewhat promotional, it provides a good look at the Meridium Foot in action:
This is not as smooth as Ottobock’s Empower Ankle in similar tasks, but neither is any other microprocessor ankle/foot. It also doesn’t have the Empower’s $40K to $50K US price tag.
The key to appreciating the Meridium for its own virtues is the same as it is for any non-Empower competitor: microprocessor feet/ankles make lives easier for amputees by automatically adjusting to varied terrain.
Meridium Foot’s Key Features
Ankle Range of Motion (ROM)
The reported ankle ROM for the Meridium Foot is 36.5 degrees, making it the highest of all microprocessor ankles/feet.
One does have to be careful with this number because true net ROM consists of the foot ROM as well as the ankle ROM, which is sometimes reported differently by each manufacturer. But we like to include this figure as a reminder to prospective users to discuss ROM (and its implications) with their prosthetist.
The Meridium Foot uses a within-step ankle accommodation strategy. This means that the ankle adjusts to the terrain during the Stance Phase of each step instead of the Swing Phase. This is important because within-step systems generally respond to changing terrain faster than between-step systems.
Meridium’s Foot Sensor and Microprocessor Capabilities
We don’t have a lot of information on Meridium’s sensor and microprocessor systems except for the following:
- Sensor data is updated and processed 100 times a second.
- The device has an Inertial Motion Unit (IMU) that uses gyroscopes and acceleration sensors to determine rotational speeds, rotational position, movements, and the distances covered by the foot in space. This helps differentiate between standing and walking on level ground, as well as on stairs and ramps. It also triggers the activation of energy-saving functions when sitting.
- Meridium can accommodate different shoe heel heights up to 5 cm (2 inches). These adjustments occur automatically within the first 20 steps after a shoe change or can be set immediately through a smartphone application.
Note, however, that for controlling the foot on different terrain or for different walking gaits, Meridium appears to actively manage damping behavior only. That is, it only modifies the level of flexion resistance through each stage of the Stance Phase. The only mention of actively managing the foot angle is to prevent the front of the foot from dipping during the Swing Phase.
We have sent an inquiry about this to Ottobock and will report back if/when we receive a reply.
In the meantime, if you are shopping for a microprocessor ankle, this is another feature worth exploring with a prosthetist. The microprocessor ankles/feet on the market use a surprisingly wide array of strategies to solve the problem of varied terrains. Common sense suggests that some strategies may be more effective than others for specific users.
Electric Power for Push-Off
The Meridium Foot does not augment push-off with electric power, but it does optimize energy storage and reuse through its carbon fiber foot.
The only microprocessor foot/ankle currently on the market that enhances push-off with electric power is Ottobock’s Empower Ankle.
Meridium’s 4-axis Kinematics
One of the interesting features of the Meridium is that it offers 4 axes for foot adjustment: the heel, ankle, toe, and mid-foot. This suggests that it should more easily conform to varied terrain, as explained in this video:
The independent data we have from August 2018 states that the Meridium’s battery life is 24 hours.
The battery requires 8 hours of charging to go from a low-power state to being fully charged.
Water Proofing and Dust Resistance
The Meridium Foot is listed as having an IP rating of 54, meaning it is dust resistant and can tolerate water splashes but not submersion.
According to our independent data from August 2018, the Meridium Foot weighs 1500 grams.
This is again a middle-of-the-pack value, matching the Proprio and Kinnex, but significantly exceeding the weight of both Blatchford’s Elan Foot and Fillauer’s Raize.
User Weight Limit
The maximum user weight for the Meridium is 125 kilograms. This matches that of the Kinnex, Elan, and Proprio, and is 25 kg more than that of the Raize.
The Meridium Foot is rated for K2 and K3 use. It is not intended for high-impact sports, such as running, basketball, etc.
Ottobock provides a software application for users to manage some of Meridium’s settings. The app is called Cockpit:
This app allows users to do the following:
- Set the heel height for a new pair of shoes (i.e. when switching shoes).
- Switch modes for different activities, such as golf, biking, skiing, etc. Note, the prosthetist must first set up these modes, which mainly consists of setting the appropriate resistance levels for each activity.
- Turn Bluetooth on and off.
- View the percentage of remaining battery charge, as well as the daily and total step counts (total step counts are tied to service checks).
The Meridium Foot offers a three-year standard manufacturer warranty, matching that of Ottobock’s Empower, Freedom Innovation’s Kinnex, and Blatchford’s Elan devices.
This warranty includes one free service and a free loaner foot during maintenance and repairs.
Users have the option of purchasing a warranty extension of another three years, providing six years of total warranty coverage.
According to our information from individual users, the Meridium Foot sells for between $20,000 to $25,000 US inclusive of all prosthetist fees.
To see how the price of the Meridium compares to its competitors, please see our Bionic Foot Price List.
Considerations Before Buying a Meridium Foot
The biggest drawback of the Meridium Foot in our view is that it does not seem as smooth as Blatchford’s Elan Foot or Freedom Innovations’ Kinnex when dealing with certain types of terrain. And, of course, none of the existing microprocessor feet/ankles can match the capabilities of the much more expensive Empower Ankle.
However, we are basing this observation solely on all available video footage, i.e. a visual impression only. We have not been able to find a scientific comparison of all the devices on varied terrain.
What we can say is that, if you are in the market for a microprocessor ankle/foot, do yourself a favor and take them all for a test walk. The ankle accommodation and microprocessor strategies differ so significantly from one device to another that compatibility with the individual user may turn out to be the most important factor.
For more information on lower limb bionics, see Understanding Bionic Legs & Feet.
For a list of competitor devices, see All Bionic Feet.
Click here for more information on Ottobock.