Ossur’s i-Limb hand is one of the world’s most advanced bionic hands. It is also one of the most expensive. The question is: is it worth it?
What’s On This Page?
- A Quick Look at the i-Limb
- Grip Patterns & Control System
- Enhanced Grip Switching
- Thumb Rotation
- Proportional Speed Control
- Automatic Finger Stalling
- Sensory Feedback
- Wrist Design
- Lift Capacity & Grip Strength
- Water and Dust Resistance
- Glove Options
- User Software
- Suitability for Above-the-Elbow Solutions
- Clinical Insights
- User Feedback Survey & Results
- Considerations Before Buying an i-Limb
- Related Information
A Quick Look at the i-Limb
This video is a bit unusual because it is filmed from a first-person POV, but it does a good job of showing the i-Limb Quantum performing a variety of daily tasks. It also shows the value of having two working hands.
This next video is filmed from a more traditional perspective and, again, shows the i-Limb performing a set of daily tasks:
Note that there are three models of the i-Limb: Access, Ultra, and Quantum, with the Access being the least advance/expensive and the Quantum being the most advanced/expensive.
We will do our best to distinguish between these models in all subsequent sections.
i-Limb Key Features
Grip Patterns & Control System
The i-Limb offers anywhere from 12 different grips for the Access model up to an industry-leading 36 different grips for the Quantum model, including 12 that can be customized by the user.
This may sound impressive, but if you look closely at the preceding videos, you will see that most of the tasks are performed using only a few core grips. This is consistent with most studies on grip usage.
The key question, then, is how well does the i-Limb perform these grips?
We cannot find any evidence that the i-Limb’s core control system (i.e. the accuracy with which it translates myoelectric signals into bionic hand actions) is superior to that of other bionic hands. Indeed, the i-Limb does not seem to be as fluid or intuitive as its main competitor, Ottobock’s Michelangelo Hand, when it comes to fine motor skills.
Here, for example, is a short video of an i-Limb user tying his shoelaces:
And here is a user performing a similar task with a Michelangelo Hand:
The differences are subtle but they are there.
However, the i-Limb doesn’t rely on its core control system to distinguish itself. Instead, it employs several innovative features to augment user control.
Enhanced Grip Switching
If you are not familiar with how the control systems for bionic hands work, you should read the first section of our article A Complete Guide to Bionic Arms & Hands.
All bionic hands offer a method of rotating through available grips. Repeated open gestures are one common way of doing this but this is impractical when there are so many available grips.
A few bionic hands offer direct grip selection through specific gestures or the ability to change grips using a mobile application.
The i-Limb offers all possible forms of grip selection:
- rotation through grips via muscle triggers;
- direct grip selection through specific gestures;
- selection via a mobile application;
- proximity control via grip chips.
Here is a short video demonstrating the use of grip chips:
And here is one showing the setup and use of an Apple Watch to control the i-Limb:
In a natural hand, the thumb performs one of three roles. It gets out of the way, as it does when carrying a shopping bag or suitcase. It can rotate downward and/or outward to oppose one or more fingers, which is how we use it most of the time. And it can also extend out from a closed hand, essentially as a balancing force against the knuckles, as it does when carrying a cup.
Some bionic hands require users to manually position the thumb, typically by using their other hand. This is the case with i-Limb Access.
The Quantum and Ultra models of the i-Limb automatically rotate the thumb into the correct position based on the grip (though you can still manually rotate it if needed). This is similar to the approach used by Psyonic’s Ability Hand and TASKA’s bionic hand but slightly inferior to the thumb rotation exhibited by the Michelangelo Hand.
Proportional Speed Control
As with most myoelectric hands, the i-Limb offers proportional speed control. This allows the user to change the grip speed and strength of the hand just by controlling the strength of muscle signals.
Automatic Finger Stalling
We humans frequently handle objects that are irregularly shaped. A wine glass is a perfect example. If you grasp a wine glass and all four fingers stop closing as soon as the thumb and forefinger encounter the bowl, you will not achieve the ideal grip.
With the i-Limb, the thumb and forefinger automatically stall out in response to resistance, but the middle, ring, and pinky fingers each continue closing until they, too, encounter something solid. In the example of a wine glass, they will correctly grasp the bottom of the bowl and the stem.
This feature allows the i-Limb to automatically conform to many different shapes.
As mentioned above, the i-limb’s fingers will stop closing after encountering a certain amount of resistance. However, there are times when a stronger grip is needed. To achieve this, the user can increase the grip force by sustaining the close signal. This is ideal for, say, grasping a jar tightly enough to open its lid.
Sometimes, users accidentally trigger an open signal. This can cause the hand to drop an object. To prevent this, the i-Limb detects short, unintended open signals and automatically re-closes the hand.
The i-Limb does not offer any form of sensory feedback to end-users.
The i-Limb offers several wrist options, including:
- an industry-standard Quick Disconnect Wrist that allows users to quickly switch between an i-Limb and other devices, such as an Electric Terminal Device (ETD);
- the i-Limb Wrist, which provides electronic wrist rotation;
- a flexion wrist that supports up to 40 degrees of flexion/extension;
- a laminate ring model for wrist disarticulation.
Lift Capacity & Grip Strength
The i-Limb hand with titanium fingers can lift a maximum of 32 Kg per finger and 90 Kg overall.
This puts the i-Limb at the top of the class in lift capacity.
We have very little to say about i-Limb’s durability. We have not uncovered any indication that durability is more or less of a problem for the i-Limb than it is for most myoelectric hands.
However, we rely mostly on the results of our User Satisfaction Survey for an objective assessment of durability. And because this article and the associated survey are new, it will likely be a few months before we have sufficient participants to publish results.
Water and Dust Resistance
The i-Limb has an IP rating of 22, meaning that it is not waterproof or dustproof.
The i-Limb should not be used without an approved cover (i.e. glove). This is the hand’s sole protection against water and dirt, and it also improves appearance.
Covers come in multiple styles and colors, including black, clear, and 18 default skin tones. Users can also request fully customized covers exactly matching their skin tone and features.
Battery options include both internal and external. The advantage of the external battery is that it can be changed by the end-user.
The battery should last an entire day with typical use. When completely drained, it requires two hours to fully recharge.
Ossur recommends that the battery be replaced once every 12 months. Internal batteries can only be replaced by a clinician.
The i-Limb comes with a comprehensive software application for end-users called “my i-limb App”. To our knowledge, this application is available only for Apple devices.
The App’s capabilities vary depending on the i-Limb model. Here are the capabilities for the top-of-the-line Quantum model:
- setting up gesture control, i.e. the ability to select specific grips using gestures;
- creating up to 12 custom grips;
- adjusting the i-Limb’s response speed to make it as much as 30 % faster;
- setting up grip chips and/or QR codes;
- creating configurations for specific tasks, including the muscle control trigger for each task;
- viewing the strength of myoelectric signals as assessment or training tool;
- turning certain features on and off.
As you can see, the application is quite comprehensive.
Suitability for Above-the-Elbow Solutions
The i-Limb can be used as the hand component in above-the-elbow solutions using many non-Ossur components and control systems.
As with most bionic limbs, it is difficult to get an official price for the i-Limb.
But based on our research to date, it appears that i-Limb prices range from about $45,000 US for the Access model to more than $70,000 for the Quantum model.
To see how this compares to other bionic hands, check out our Bionic Hand Price List.
Ossur offers a base two-year warranty on the i-Limb, which can be extended for up to five years at the user’s option.
The device is eligible for a free service every 12 months while under warranty.
Additionally, users can download a software application that includes a Hand Health Check feature. Users are prompted to run a health check every three months and, if issues are detected, Customer Support will contact the user’s prosthetist to arrange an inspection and/or repair.
If requested, Ossur will make a service hand available to users on the same day that the hand is scheduled for repair.
The following comments are from clinicians with extensive experience with the i-Limb:
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. The i-Limb technology is fairly robust for a 5-digit multi-articulating hand, and I have had few breaks over the first couple of years of patient use. The hand is very user friendly from a prosthetist’s standpoint as I can log into its software with an iPhone or iPad, perform myo-testing, and change the patient control parameters or grip selection features. This really simplifies the fitting process. On the patient end, they can also change their grip selections via the app.
Some of the pro’s for the Quantum compared to the Access: auto-thumb rotation based on grip selection (Access has manual or user thumb rotation), grip chips for ADL areas where specialized grips are needed, and gesture or motion-activated grip selection (the most beneficial difference, in my opinion.)
Here is my opinion on the most advanced features: most of my users utilize 3-5 grips for daily use (Power Grip, 3-jaw Chuck Pinch Grip, and the Lateral Grip (thumb only) are the most commonly used. The gesture control on the Quantum is a cool feature but not necessary to receive the majority of benefits for this hand. Overall, most of my patients love the hand’s design and features, and use it more often than not in their ADL and work needs. It is robust and Ossur provides great support.
Tony Gutierrez, Bionic Prosthetics and Orthotics Group
Munster & Lafayette, Indiana
User Feedback Survey & Results
Are you currently using an i-Limb or have you used one 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 the i-Limb.
As soon as we do, we’ll update this section.
Considerations Before Buying the i-Limb
Here is our concern with the i-Limb: it is expensive and yet we’ve not seen any clear proof that it is notably better than some of its less-expensive competitors. It has a broader feature set than any other bionic hand on the market, and one or more of these added features may be extremely important to an individual end-user, but all our anecdotal feedback (via user videos and social media) suggests it is, at its core, an average bionic hand.
Part of our hesitation to give the i-Limb more credit for its impressive feature set is that users tend to use only the basic functions of any bionic hand. For example, even when 36 grip patterns are available, users tend to use only 2 or 3. So are the added features worth it?
Having said all that, we rely on feedback from end-users through our User Satisfaction Survey for a formal assessment of any bionic device, and that’s what we’ll do here.
For a list of competitor devices, see All Bionic Hands.
For a comprehensive description of all current upper-limb technologies, devices, and research, see our complete guide.
If you are shopping for a bionic hand, do not miss our article on Bionic Arm & Hand Control Systems. Getting this part of your bionic system right is probably the biggest single ingredient in your long-term satisfaction.
Click here for more information on Ossur Prosthetic Hands.