Connect with us

Prosthetic services

Upper limb prosthetics

Introduction to Upper Limb Prosthetics

Prosthetic arms can be inert, body-powered or bionic. The inert type of prosthetic arm is not activated and therefore serves a cosmetic function only. A body-powered prosthesis uses existing body motion to activate a movement device. The most common form of body-powered upper limb prosthetic is the shoulder harness which is used to activate the arm or hand.

Myobock® Below Elbow Prosthesis

Roger Wolfson and Associates is certified to provide the Myobock® Below Elbow upper limb prosthetic.

The Myobock® Below Elbow is a myo-electrically controlled upper limb prosthesis that includes accessories and fittings to ensure the most dependable rehabilitation results. The components of the Myobock® Below Elbow prosthesis combine optimal outer appearance with high grip force and grip speed, as well as numerous other combination and adjustment options.

DynamicArm Transhumeral Prosthesis
Amputations above the elbow constitute a special challenge since the function of the elbow has to be replaced in addition to that of the hand. The DynamicArm elbow joint makes virtually natural movements possible with its special technology. Controlled by your muscle signals, the DynamicArm is driven by an electric motor. The control unit of the DynamicArm also transmits the muscle signals to the prosthetic hand, so that you are able to rotate the wrist unit in addition to opening and closing the hand with short response times. You can extend and flex the DynamicArm as well.

We recommend combining the DynamicArm with the Ottobock VariPlus Speed. It is equipped with a high-performance drive unit, and opens and closes almost three times as fast as other electric hands. A fitting with the DynamicArm and VariPlus Speed restores numerous abilities to hold objects, grasp and be active at work, in everyday life and recreation.

The Residual Limb

There are three major critical factors involved in the design and optimisation of trans humeral and elbow disarticulation prosthetics, including:

  • Length of the bony lever arm
  • Quality and nature of soft tissue coverage
  • Shape and muscle tone of the residual limb

Assembly

The above-elbow prosthesis consists of:

  • A single plastic upper arm shell
  • An elbow joint, usually with incorporated locking mechanism
  • A plastic forearm
  • A wrist joint
  • A terminal device, either a hook or a hand.

Elbow Unit

A body-powered elbow unit consists of a simple hinge, with a half-dome-shaped plastic covering. To retain an elbow position two options are available, which take the form of either a friction or a locking mechanism. Such devices that function as locking mechanisms are operated using a knob located on the forearm or using a cable attached to the shoulder harness. To assist the user of a body-powered above elbow prosthesis in flexing the elbow, an elbow unit with a forearm lift assist is used, which acts as a spring mechanism that somewhat compensates for gravitational forces.

Wrist Unit

A wrist unit is used for:

  • Attaching purposes
  • Rotation purposes (passively with sound hand)
  • Interchange between hands/hooks.

Terminal Device

The function of the terminal device is to replace the grasp function of the hand.

Three types of terminal device are available:

  • Hook
    • To grasp small objects
    • To grasp, hold, carry, pull or push.
  • Hand
    • To grasp large, round objects
    • To grasp between thumb and first two fingers (three jaw chuck pattern)
  • Passive
    • Entire passive, for cosmetic purposes only

Body Harness              

As the term suggests, a body-powered prosthesis uses the patient’s own body power to activate motion of the artificial limb. Thus, where it concerns upper limb prosthetics, the body harness is a necessary and extremely important component.  The harness transfers motion and forces from the residual limb, shoulder girdle and trunk directly to the prosthesis.  In cases where there is a loss of an elbow, the harness is also fixed to the socket above the elbow stump.  The higher the amputation level, the more difficult it becomes to control and fix the prosthesis. Nevertheless, a patient with a shoulder level amputation can still be fitted with a prosthetic.

A body harness can also be used to control elbow flexion and locking. In the case of a below elbow fitting, the harness activates the terminal device only.

A body-powered prosthesis together with natural muscle motion enables good functionality. The pressure of the harness on the body also gives the patient sensory feedback.  However, the degree of sensory feedback depends on the fit of the prosthetic socket, the harness as well as the features of the prosthetic hand.

When fitting a body harness, no two people are the same. Hence, the fitting must be performed on an individual basis. Two patients with the same physical constitution may be different with respect to the motion and force in the shoulder girdle region as well as each residual limb is different.

To accommodate an above elbow prosthesis, two very different harness systems have been developed and proven in practice, enabling performance of the required functions consisting of activating the terminal device, below elbow flexing and independent locking or releasing of the elbow joint.

Basic functions of the harness system

The main function of the harness is to suspend the prosthesis to the residual limb. In so doing it should:

  • Distribute load as much as possible
  • Be well suited to the patient’s body structure
  • Be stable in all normal positions of use

Upper limb prosthetic rehabilitation

Follow up consultation sessions are the most important aspect of the upper limb prosthetic rehabilitation process. Yet, most often, this process is neglected.  There are three important aspects to consider following the initial prosthetic fitting:

  • Maintenance of the socket fit, suspension and comfort of the patient, especially where this pertains to volume changes in the residual limb.
  • Ongoing monitoring to ensure that the patient fully masters the functions of the prosthesis at home as well as in the work environment.
  • Re-evaluation of socket style, harness design and component selection based on the experience of the individual.

There are numerous aspects to upper limb prosthetic rehabilitation that cannot be addressed until the patient has had a reasonable amount of time to assimilate the use of the new prosthetic. Questions need to be answered and new skills need to be mastered. In line with goals and aspirations, the fit, comfort and function of the prosthesis need to be maintained and optimized over time.

Successful long term use of an upper limb prosthesis depends primarily on its comfort and perceived value. Innovative design and careful custom adaptation of socket and harness principles, careful attention to follow up adjustments and prescription revisions based on changing needs are essential to successful prosthetic rehabilitation.

Continue Reading
Click to comment

Leave a Reply

Your email address will not be published. Required fields are marked *

Prosthetic services

Does your prosthesis hurt? Are you walking with difficulty?

While various levels of amputations are carried out, by far, the most common involve:

  • Below knee (trans tibial)
  • Above knee (trans femoral)

No matter the amputation level, there is a great deal your dedicated prosthetist can do to diagnose and employ the right measures in order to alleviate any painful conditions associated with prosthetic use.

Continue Reading

Prosthetic services

From amputation to prosthesis in three weeks

From post-op to crutches within five days and walking comfortably with a prosthesis in as little as three weeks! The idea of walking with crutches within five days post-op and being able to walk with a prosthesis in as little as three weeks after undergoing an amputation sounds like science fiction – but it is not. It is just up to clever engineering on behalf of Roger Wolfson and a desire to get walking again.

Yet, it is even more surprising to learn that the technique used in creating a prosthesis designed to do just that has been around for many years.

Why surgeons should regularly use the services of a prosthetist when performing an amputation

Should a surgeon perform the amputation procedure in consultation with a prosthetist that is familiar with the Immediate Post-Operative Prosthesis (IPOP) technique, the results can be extremely beneficial to the well-being of the patient, and result in considerable cost savings to both patients and funding sponsors alike.

A scientific paper pertaining to this very topic was presented at an Orthopaedic Surgeons Congress that took place in South Africa recently. However, despite the fact that the Chairman of the Congress raised the burning question as to why, in fact, surgeons don’t regularly consult with a prosthetist around the surgical procedure, the fact still remains that as things currently stand, the number of surgeons that use the services of a prosthetist nevertheless remains fewer than desired.

Continue Reading

Prosthetic services

Measuring Residual Limb

When is the residual limb ready for measurement?

How long does it take before for the residual limb is ready for measurement?

Once the initial measurements have been taken a number of test fittings are carried out.   This is vital for the comfort of the patient. I like to compare the making of a prosthesis to the making of a wedding dress. For a young future bride the making of a wedding dress is of vital importance and she wants to have it fitting absolutely perfectly.

The more fittings the dressmaker is prepared to do for her, the happier she will be as she wants the outcome to be perfect. If the dressmaker’s worth her salt and has pride in her work she will be happy to do the extra fittings even though they are not in the initial cost.

We will do as much as it takes to make sure that the outcome of the prosthesis will give the patient comfort, mobility and confidence. If the patient is a trans femoral (above knee amputee)the process of measuring and fitting for the first walking prosthesis takes between three and five days.

If the amputee is a trans tibial (below the knee amputee) the first walking prosthesis can be anything from one hour to 2 days once both the patient and the prosthetist are happy with the fit. When the final prosthesis is made the time frame should not be longer than three weeks before the finished prosthesis is fitted.

During this process the amputee goes for an extensive exercise program which is carried out by an experienced physiotherapy team.

The Rehabilitation exercise program is optional and it depends on the economic situation of the patient usually the medical aid will pay for this service as they have already invested money in the prosthesis and they would like the amputee to make full use of the prosthesis. Even though the exercise sessions are long and hard my patients report to me that they are a lot of fun. Actually I find them fun because I join in some times especially the dance class.

Continue Reading

Trending