Nearly 2/3 of upper-limb amputations involve finger or partial hand loss. Ossur’s i-Digits line of products provides one of the few bionic options to meet this need.
What’s On This Page?
- A Quick Look at the i-Digits Partial Hand
- Grip Patterns & Control System
- Thumb Rotation
- Proportional Speed Control
- Automatic Finger Stalling
- Sensory Feedback
- Lift Capacity & Grip Strength
- Water and Dust Resistance
- User Software
- Clinical Insights
- User Feedback Survey & Results
- Considerations Before Buying an i-Digits
- Related Information
A Quick Look at i-Digits
These two short videos show i-Digits devices being used for many different tasks:
It is easy to imagine millions of people around the world benefiting from a device like this!
i-Digits comes in two models: Access and Quantum. Access is the basic model, while Quantum adds additional grip capabilities and increased speed and strength.
Grip Patterns & Control System
i-Digits Access offers 12 different preprogrammed grips. The Quantum model offers 20 preprogrammed grips. This sounds like a big difference but most users only use a few core grips.
The main control advantages that Quantum has over Access are:
- the ability to create up to 12 custom grip configurations, which allows users to create custom grips for specific tasks;
- the ability to switch to specific grips using gesture control, meaning you can assign one grip to each of four prosthesis movements (forward, back, left, right); in the absence of this feature, users have to rotate through grips using other gestures or choose a specific grip in a mobile app that communicates with i-Digits via Bluetooth;
- the ability to automatically switch between grips using grip chips; these are small Bluetooth chips that you can position around your environment that trigger specific grips when your i-Digits Quantum passes within a certain proximity; for example, you can place a grip chip near your computer to automatically switch to an ideal grip for typing on a keyboard;
- an increase in the closing speed of the digits by as much as 30%.
Here is a short video demonstrating these advantages:
Unlike its i-Limb cousin, i-Digits does not offer an electronically positioned thumb, if a thumb is present at all. Instead, users must manually rotate the thumb into the desired position.
This is not a major drawback. Myoelectric hands typically require some form of preparation before performing a task, such as selecting an appropriate grip. In most instances, users will intuitively rotate the thumb into position with their free hand.
The use of a manually positioned thumb is also a byproduct of i-Digits modular design, where each digit must be an individual unit. An electronically rotating thumb requires an additional actuator and stronger motor — both difficult design challenges for a thumb that may or may not be present.
Proportional Speed Control
This refers to the ability of the user to control the speed and force of the grip via the speed and force of the muscle signal used to close or open the bionic fingers.
i-Digits offers this capability in both the Access and Quantum models.
Automatic Finger Stalling
Similar to the i-Limb, each i-Digits digit will automatically stall out as it meets resistance, while the other digits continue to close. This ensures a natural grip for any object regardless of its shape.
The importance of this feature can be appreciated simply by observing how a natural hand grips an irregular-shaped object like a wine glass. Anything short of automatic finger stalling might result in an unstable grip.
Sometimes, users of bionic hands can drop an object by accidentally triggering an open signal. i-Digits Quantum detects short, unintended open signals and compensates by re-closing the fingers.
In cases where a stronger grip is required, i-Digits Quantum offers a vari-grip feature. This allows the user to increase the grip force by sustaining a close signal. A perfect use case for this might be gripping a jar tightly enough to open its lid.
i-Digits does not currently offer sensory feedback in any of its models.
Lift Capacity & Grip Strength
The maximum finger carry load for i-Digits is five kilograms. The maximum carry load for the overall device is 20 kg.
We do not have any information on grip force (i.e. no newtons rating), which is likely difficult to calculate given all the possible configurations.
Quantum is described as having up to 30% more strength than Access, but Ossur’s literature doesn’t define what this means.
Ossur states that i-Digits has an expected service life of five years. They also recommend servicing the device every 12 months.
We have not identified any specific complaints about durability with i-Digits. This may be because we have not yet been able to collect sufficient user feedback.
However, Ossur does state that i-Digits is designed for “low to moderate impact activities only.” Also, given its low resistance to water and dust (see next section), it is probably best to think of i-Digits as a relatively fragile device.
Water and Dust Resistance
i-Digits has an IP rating of 22. This is quite low and essentially means that the device has very poor protection against water and no protection against dust.
i-Digits is powered by two Ossur batteries. A fully charged device can be used for 16 hours, depending on the level of use.
Recharge time for a fully drained pair of batteries is two hours.
The batteries must be replaced every year.
Ossur offers end-users the my i-limb mobile application for all i-digits models.
This allows users to instantly select one of 14 grips via the app.
It also allows users to access the advanced features that come with the i-Digits Quantum (as described in the Grip Patterns & Control System section).
We have not been able to obtain any reliable pricing information on i-Digits. This is partly because Ossur is incredibly secretive about prices for all its bionic devices, and partly because i-Digits can have many different configurations, so there is no one price.
However, based on the price of the i-Limb (estimated from $45,000 to $70,000 US, depending on the model), i-Digits is likely expensive.
All i-Digits models come with a standard two-year warranty.
Users can also pay to extend the warranty for as many as three additional years.
The following comments are from clinicians with extensive experience with i-Digits:
I have fit several patients with the Ossur i-Limb technology including several partial-hand (i-Digit), i-Limb Access (base model), and Quantum (top model) solutions. For 90% of applications, the i-Limb features are the same across all models.
Fitting of the i-Digits can be challenging in the longer hand amputation cases (distal to MCP level). Placement of the digits to receive multiple grip patterns is challenging and often some grips have to be sacrificed. Overall this technology is a game changer as it opens up prosthesis use and control for a population that was overlooked for so long, but the prosthesis and batteries can be a bit cumbersome. Despite this, it is a great solution.
Tony Gutierrez, Bionic Prosthetics and Orthotics Group
Munster & Lafayette, Indiana
User Feedback Survey & Results
Are you currently using i-Digits or have you used it in the past?
If so, why not help others by sharing your experiences in this quick survey:
We do not yet have a sufficient number of survey participants to publish fair and accurate results for i-Digits.
As soon as we do, we’ll update this section.
Considerations Before Buying the i-Digits
The biggest single consideration before buying any bionic partial hand is your prosthetist. This is because every residual partial hand can vary significantly. Bionic partial hands must therefore be extensively customized to match your specific requirements. This is true of every prosthesis, of course. It’s just that partial hands tend to have more possible configurations.
We therefore strongly recommend that you deal only with a prosthetist who has proven experience with partial hand devices.
Unfortunately, if you want a bionic partial hand, your product choices are limited. i-Digits is currently one of only two options that we know about. The other is the Vincent Partial, which appears to have similar functionality. But Vincent has not produced any English-language material or videos in years, which makes us question their commitment to the North American market.
Another option is to use a mechanical partial hand prosthesis.
For a list of all competitor devices, see All Partial Hand Options.
For a comprehensive description of all current upper-limb technologies, devices, and research, see our complete guide.
Also, do not miss our article on Myoelectric Control Systems. Getting this part of your bionic system right is probably the single most important element in your long-term satisfaction.
Click here for more information on Ossur Prosthetic Hands and Partial Hands.