Wonderful MAEH2

Prosthetic and orthotic clinics fitting at the highest upper-limb levels are where the MAEH2 belongs. Its intended wearers have a shoulder joint disarticulation or a middle or short upper-arm stump, levels at which the prosthesis must provide the elbow and the positioning of the whole arm as well as the grip. The arm meets that need with two kinds of joint: myoelectric hand and elbow for movement, and passive, self-locking wrist and upper-arm rotation for orientation.

Prosthetists use the rotation joints to prepare the arm before each session of training. With the upper arm and wrist locked at a starting angle, therapists can concentrate on teaching the separate muscle contractions that bend the elbow and those that open and close the hand. As the wearer gains control, the locked angles are adjusted to match the tasks practised, so the orientation joints become part of the training plan.

At home, the pattern is set and then act. A wearer preparing a meal turns the upper arm outward and pitches the wrist, then raises the forearm under muscle control to reach a cupboard shelf and close the hand on a packet. For lifting a shopping bag or carrying a box against the body, the upper arm is turned inward so the forearm comes across the trunk. Holding a jar while the sound hand twists the lid works the same way, with the hand locked at the angle the job needs.

Workplaces with phones, computers and other electronics suit the arm too, since its anti-electromagnetic interference keeps the control signal steady. Clinics that serve both shoulder-level and short upper-arm wearers can fit one component across both groups, choosing three or five fingers per person.

Orientation that stays put through the task

The wrist and upper arm self-lock at any position. Once turned, they keep the hand and forearm aimed where the job is, and every muscle signal goes toward bending the elbow or working the grip.

Powered movement where effort counts most

Bending the elbow and closing the hand are the two actions repeated most during a task, and both answer to myoelectric control. The passive joints take care of the occasional changes in direction.

Forearm direction under the wearer's control

Upper-arm rotation lets the forearm come across the body for carrying or open outward for reaching. At shoulder disarticulation level, that choice of direction decides where the hand can work.

Steady control near phones and electronics

Anti-electromagnetic interference is part of the arm's standard build. The myoelectric signal holds its accuracy with a mobile phone in a pocket or on the desk beside the wearer.

One component across three fitting levels

Shoulder joint disarticulation and middle and short upper-arm stumps are all within the MAEH2's range. A clinic can standardise on one arm for wearers whose residual limbs differ in length.

Hand form matched to the person

Three-finger and five-finger hands are both available. The choice can follow the wearer's daily tasks or personal preference without changing anything above the wrist.

Aluminium and carbon fibre structure

Aluminium and carbon fibre form the frame and the joint housings of the arm. The complete assembly, from hand to upper arm, comes to 1.1 kg.

Simple routine for setting the angle

Setting an angle takes one movement: turn the joint, let go, and it locks. Wearers and clinicians alike can reset the orientation between tasks with the sound hand.

Two degrees of freedom

The hand and the elbow are the two powered movements, and together they handle grasping and raising or lowering the forearm.

Myoelectric hand

Contractions of chosen muscles in the residual limb produce the electrical signals that drive the hand's actions.

Myoelectric elbow joint

Elbow actions run under the same form of control, so the forearm rises and falls in response to the wearer's muscles.

Passive wrist rotation

Turned by hand, the wrist pitches the fingers toward the object before the grip begins.

Passive upper-arm rotation

Rotation at the upper arm swings the forearm's path of movement inward or outward around the arm's long axis.

Self-lock at any position

Both rotation joints lock wherever they are left. No fixed steps limit the angle a wearer can choose.

Anti-electromagnetic interference

Built-in resistance to electromagnetic interference protects the control signal from sources such as mobile phones.

Three-finger hand

A three-finger configuration closes around everyday objects such as cups, packets and bag handles.

Five-finger hand

The five-finger configuration presents a full hand form while working on the same joints.

Shoulder joint disarticulation fitting

The arm is designed for wearers whose amputation is at the shoulder joint itself, where the prosthesis provides the elbow, the hand and the orientation of the arm.

Middle and short upper-arm stumps

Upper-arm residual limbs of middle and short length are also within its intended range.

Aluminium and carbon fibre

These two materials make up the structure of the hand, elbow and rotation joints.

Weight of 1.1 kg

The full MAEH2 assembly weighs 1.1 kg, which is 1,100 g.

The MAEH2 suits clinics fitting shoulder joint disarticulation and middle or short upper-arm stumps, where the wearer depends on the prosthesis for the position of the whole arm. Its strength is the division of labour between its joints. Wrist and upper-arm rotation are set by hand and locked, which fixes the direction of the forearm and the pitch of the hand for the job in front of the wearer. Myoelectric control is then reserved for the elbow and the grip, the movements a task repeats. Built-in anti-electromagnetic interference keeps that control steady around phones and office equipment. For a wearer who reaches into cupboards, lifts bags and holds objects close to the body, the MAEH2 delivers an arm that is set once and then worked by muscle signals.