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Regaining Movement : Restoring Feeling

Regaining Movement : Restoring Feeling

07 Aug 14:00 by Julie McEwan

Julie McEwan blogs on medical devices for Parkinson's disease and stroke

We are all used to seeing the ‘traditional’ solutions for managing reduced mobility, due to illness or injury. Canes, stick, rollators and wheelchairs are everyday objects – in fact we are currently joined by two crutches in our office, after our colleague Alex tore a ligament whilst playing football.

Regular followers of my blog will be aware of my fascination with cutting edge technology in the medical device industry and the positive impact this has on patients. This week I am turning the spotlight onto advances in this particular area; the patients and indeed therapeutic areas they serve.

I recently read an article focusing on a mobility aid for those suffering from peripheral neuropathy. This disease results in damage to the nervous system causing a desensitisation of feeling, impaired balance and reduced awareness of one’s own position. The cumulative effect leads to a greater occurrence of falls and a general lack of stability. A specialised insole has been developed, that works in conjunction with a unit worn around the leg, to counteract this by offering sensory cues which readdress this. During initial trials, not only was an improvement in patients’ functional gait analysis reported, but more interestingly a huge increase in the patient’s confidence levels (measured on a reported standard called Activities Specific Balance Confidence Scale). Similar devices exist for Parkinson’s sufferers, including a device worn over the shoe that projects a marker in front of the patient. This sensory cue has been found to assist with Frozen Gait, a symptom of the disease which makes sufferers feel like their feet are literally frozen to the floor, particularly when switching between motor actions. Research shows that people suffering from Parkinson’s are more dependent on visual cues as spatial awareness of limbs is decreased.

These devices would need to be continuously worn for the benefits to be retained however, improvements in affected gait are also being seen from training. One study in the States focused on children suffering from cerebral palsy and an altered gait referred to as ‘crouch gait’. Due to the condition, the children displayed muscle weakness and a limited range of motion within the legs. Using a device, tethered to the pelvis, researchers applied different low levels of downward force through the centre of the pelvis, in regular sessions over 6 weeks. This training increased strength within the calf muscle -which is the primary load bearing muscle when standing and lead to improvements in posture, range of motion, length of stride and overall muscle coordination.

Advancements in exoskeleton development are already showing benefits for stroke patients and those affected by muscular atrophy. These lightweight suits (some weighing as little as 900 grams) use cables and belts attached to an actuator to propel the patient to walk, adjusting and correcting the problems in gait as they go. These devices can act on the lower leg, ankle or hip to provide assistance where necessary. Again, leading to improvements in confidence and stability. Research continues to make these devices smaller, lighter and more discrete so they can be worn under clothing.

3D printing has also been utilised in this vein, with an exoskeleton arm being printed to help a 3 year old boy with Spinal Muscular Atrophy. The designer was initially approached by the boys exasperated mother after she had tried some low cost devices without success. Further advancements even include an exoskeleton that assesses a patient’s natural gait and use algorithms to determine deviations from this, predicting a potential fall and using motors to re-establish hip stability to correct and prevent. The application of this device is huge, not only for injury and illness sufferers but also for the elderly. 

Perhaps the most startling and, in my opinion, the most fascinating, advancements can be seen in prosthetic development.

Researchers at MIT have been working on surgical possibilities that could improve the feedback between amputees and their prosthetic limbs. Muscles work in pairs, an antagonist and an agonist. This relationship provide feedback and allow us the spatial  awareness of our limbs. Amputation removes this relationship and this is what the researchers attempted to mimic.  Experimenting on rats, the researchers connected nerves to muscle grafts at the amputation site and could recreate the muscle partnership – so as one muscle stretched the other contracted, providing spatial feedback on the position of the prosthetic limb. With the ability to harvest muscle grafts from other areas of the patient’s body this technique could be used in any amputation location – as long as some of the nerve remains to work with.

To complement the awareness of the prosthetic limb new advances, demonstrate the movement of prosthetic limbs simply by using the imagination.  In trials sensors were implanted into the patient to collect signals from the spinal cord. In this early stage, the signals were used to control a virtual arm on a screen but the researchers involved suggested that the same principles could be used to conduct trials with a real prosthetic moving forward.

Earlier this year a patient in the Netherlands was fitted with the first click on robotic prosthetic. This was the culmination of three surgeries. Initially a metal rod was inserted into the marrow cavity of the bone in the upper arm, followed by a connecting rod which is screwed through the patient’s skin. Finally, a specialist plastic surgeon reconnects the nerves that originally connected the hand and lower arm to the muscles in the upper arm. Following a strenuous rehabilitation period, the prosthetic arm can be moved by muscle contraction in the upper arm. The patient imagines opening and closing the prosthetic hand, for example, this causes muscle activity in the upper arm which is detected by a sensor – making the movement possible.

Trials are also underway for patients that suffer from partial and total paralysis. One patient who lost the use of his hands after breaking his neck, was able to move his hands again. This success was the interface between a small computer chip inserted into the patient’s brain, an external cable link and an electrode sleeve. The patient’s brain signals were interpreted via this network, in real time, to allow the movement. The partnership of a brain implant and a full body exoskeleton has allowed movement in the limbs of paraplegic patients. This implant, known as a ‘stentrode’ is inserted into a major blood vessel in the brain. Next to the brain tissue, this implant detects the message that the brain would normally send to the limbs to cause movement. This is sent, again by external wires from the back of the head, to the exoskeleton and results in the appropriate limb movement.

With further technological and scientific discoveries and developments in this area it is hard to imagine and exciting to speculate, what might be possible twenty years from now…………………

More Blogs from Julie McEwan

Julie has written numerous interesting and well researched blogs on a wide range of topics related to Medical Devices and Human Factors.  Please click here to read more of Julie's blogs and here to find out more about Julie.