Key Features: i-limb digits

Every i-limb digits solution is unique, but here are some of the key elements that have to be considered for every fitting:


Selection criteria

There are physical criteria that dictate whether i-limb digits is an appropriate solution or not. Ideal candidates for i-limb digits have amputation levels through, or just proximal, to the metacarpal phalangeal level of one or more digits. We consult with prosthetists in order to ensure that the appropriate i-limb digits solution is supplied.

Socket Interface Materials

Every effort is made to ensure that i-limb digits solutions preserve the critical functional elements of the hand, as well as protecting any compromised skin. This preservation is normally accomplished by using silicone interface materials, which allow users to comfortably wear the sockets without further irritating or damaging the soft tissue of their digits or hands.

Power

Each i-limb digits solution requires batteries, access to charging the batteries, and a method of turning the device off and on.

Positioning these elements in the device depends on the length of the remnant limb. If the amputation is far enough proximal to the MCP joints, these elements of the device can be integrated into the "palm" of the prosthesis.

If the limb deficiency site is more distal, then the "hardware" must be moved onto the forearm, and housed in as unobtrusive a method as possible, while still providing access for charging the batteries.

Battery, controller module and associated wiring have been housed in a number of personalized and functional ways and result from the interaction between the patient and the prosthetist.

This aspect of i-limb digits design is one of the more challenging and requires an experienced upper limb prosthetist to customize this design.

Control Strategy

The most common method of controlling i-limb digits is to use myoelectrodes or force-sensing resistors (FSR's). Electrodes sense muscle contraction while sitting on the skin above the muscle. The muscle contraction is filtered, amplified, and then sent to the processor which tells the fingers whether to open or close.

FSRs sense pressure and can be utilized if motion is available from a remnant digit to press into one or more of these sensors.

Control App

The biosim mobile control app allows the prosthetist to interact with the i-limb digits system. It communicates wirelessly via Bluetooth® connection between the mobile device and the controller inside the prosthesis.

biosim allows the prosthetist to make adjustments to the prosthesis without tethering and statistical information can be gathered in real-time.

Input signals can be adjusted through gain and threshold levels, various control strategies can be changed and utilized, and hand features can be enabled and disabled all through biosim.