Medical technology is currently capable of treating such physical hardships as loss of limb, eyelid paralysis, and chronic osteoarthritis – but researchers are continually finding ways to improve upon the effectiveness of these and other implanted and prosthetic device technologies. What follows is a sample of new technologies and research efforts that hold promise for a future in which human beings are able not just to survive, but thrive in the face of any conceivable physical difficulty.
Sling Mechanism for Eyelid Paralysis
Humans blink about 15 times a minute – more than 14,000 times in a typical 16-hour day. Because this activity is crucial for cleaning and lubricating the eyes, patients suffering from eyelid paralysis need treatment. Most of these patients injured the cranial nerve that controls involuntary eye blinking, whereas others may have been born with Moebius syndrome, a rare neurological disorder that affects the facial nerves. One current treatment for eyelid paralysis requires the transfer of a muscle from the leg into the face in a 6- to 10-hour surgery, and is not always a suitable option for elderly patients. An alternate treatment involves suturing a small gold weight into the eyelid. The weight closes the eyelid using gravity, but it cannot synchronize the eyes to create a natural blinking pattern.
Now, Craig Senders and Travis Tollefson of the University of California-Davis Department of Otolaryngology, Head, and Neck Surgery, are developing a more attractive third option: an artificial muscle used in conjunction with a sling mechanism to help facial paralysis patients restore the ability to blink more naturally. Illustration of left eyelid sling that is attached to the electroactive polymer artificial muscle device (EPAM) after passing through an interpolation unit that is implanted in the lateral orbital wall (note screw fixation). (UC Davis Health System photo)
The mechanism uses an artificial muscle – invented by SRI International of Menlo Park, CA – to drive eyelid movement. The muscle includes a piece of soft acrylic or silicon layered with carbon grease. When a current is applied, electrostatic attractions cause the outer layers to pull together and squash the soft center. This motion expands the artificial muscle, which is powered by an implanted battery source similar to what is used in cochlear implants. Once the charge is removed, the muscle contracts and flattens the shape of the sling, blinking the eye. When the charge is reactivated, the muscle relaxes and the soft center reverts back to its original shape.
Operating experimentally on cadavers, the researchers inserted a sling made of muscle fascia or implantable fabric around the eye. Small titanium screws secured the eyelid sling to the small bones of the eye. The surgeons disguised the entire device in a natural hollow located at the temple. For patients with one functioning eyelid, a sensor wire threaded over the normal eyelid could detect the natural blink impulse and program the artificial muscle to blink at the same time. Patients with two paralyzed eyelids could use an electronic pacemaker to blink their eyes at a steady rate.
Researchers are still refining the mechanism on cadavers and animal modes, but it is estimated to be available for human patients within the next five years.
Smaller Heart Monitor Implants
Someday, wearable or implanted devices driven by microchip technology could conveniently detect and diagnose heart problems, monitor patients with Parkinson’s disease, or predict seizures in epileptic patients. Researchers at MIT’s Microsystems Technology Laboratory (MTL) have built a prototype device that incorporates a low-power chip to measure and record electrocar-diograms (ECGs). Patients could wear the monitor at home to give doctors a more detailed picture of their everyday heart health. The ECG device currently prescribed to monitor recent heart attack victims is not able to store much data, and runs on a bulky battery that is inconvenient to wear.
The new MIT monitor prototype is an L-shaped device, about 4” long on each side, that sticks to the chest and can be worn without any external wires protruding. It is capable of storing up to two weeks of data in Flash memory, and runs on just two milliwatts of power. In the future, researchers hope to engineer chips that can be powered by energy from the body of the person wearing the device.
ECG data from the chip can be downloaded for analysis, allowing doctors to spot future problems. Down the line, the researchers envision working the algorithm into the chip so that data can be analyzed more immediately. They also plan to incorporate an alarm that will alert the patient and/or doctor if a heart attack appears imminent. The researchers plan to start testing the device on healthy subjects this spring, followed by trials involving patients with cardiovascular disease.
Smarter Bone Implant Material
With any biomedical implant, there runs the risk of rejection – which means that the more successfully it can imitate a specific body material, the higher the likelihood it will be accepted by the body. A “metal foam” developed at North Carolina State University could help future biomedical implants achieve a lower risk of bone rejection compared to conventional implant materials such as titanium.
The novel composite foam is lighter than solid aluminum, and can be made of either 100% steel or a combination of steel and aluminum. The rough surface of the foam would also help foster bone growth into the implant, improving its strength. It is lightweight and displays high-energy absorption capability, but most importantly, it exhibits a modulus of elasticity that is very similar to that of bone. Modulus of elasticity is crucial to the success of a biomedical implant, said Dr. Afsaneh Rabiei, an associate professor of mechanical and aerospace engineering who led the research. It is measured in gigapascals (GPa), and refers to a material’s ability to deform when pressure is applied, and then return to its original shape when pressure is removed. The closer the implant material’s modulus of elasticity is to that of bone, the higher the likelihood that the body will accept the implant.
Pocket-Sized Device Treats Musculoskeletal Pain
Ultrasound technology has been known to relieve muscle and joint pain in doctors’ and physical therapists’ offices, but those benefits could someday be accessible in the comfort of one’s home, thanks to a miniature ultrasound device created by George K. Lewis, a biomedical engineering graduate student at Cornell University. The device is about the size of an iPod and can fit into a pocket. It treats joint pain by sending out ultrasound waves into muscles via a transducer, a coin-sized polystyrene pad. The latest prototype is gentle enough to stay in close contact with the body for up to 10 hours. The device has been successful in trials involving animals, and it is scheduled to undergo testing in a clinical trial restricted to human patients with osteoarthritis of the knee. If future trials are successful, it may help the device receive the FDA approval it needs in order to find its way into the pockets of arthritis sufferers nationwide.
Energy-Recycling Prosthetic Foot
Since a prosthetic foot cannot reproduce the force a living ankle exerts to push off of the ground, it consumes about 23% more energy than natural walking. To cut down on some of that wasted energy, a team of engineers at the University of Michigan has devised a way for an artificial foot to recycle energy between steps by enhancing the power of the ankle push-off, which also has the added benefit of making it easier for the user to walk.
“All prosthetic feet store and return energy, but they don’t give you a choice about when and how. They just return it whenever they want. This is the first device to release the energy in the right way to supplement push-off, and to do so without an external power source,” said Art Kuo, professor in the UM departments of Biomedical Engineering and Mechanical Engineering.
Working together with Steve Collins, a UM graduate student at the time, Kuo created the prosthetic device, which is powered by a small, portable battery that uses less than 1 Watt of electricity. The foot naturally captures the dissipated energy, and a microcontroller prompts the foot to return the energy to the system at the right time. When the researchers tested the device on non-amputees wearing a rigid boot and prosthetic simulator, they found that test subjects spent just 14% more energy walking with the new artificial foot compared to natural walking – a noticeable improvement over the 23% difference observed with conventional prostheses.
The artificial foot is now being tested on amputees at the Seattle Veterans Affairs Medical Center. Commercial devices based on the technology are also under development by an Ann Arbor, MI company.
Hip Replacement Measurement
According to the American Academy of Orthopaedic Surgeons, more than 193,000 total hip replacements are performed each year in the United States. Hip replacement measurements have conventionally relied on a single-marker method, but increased accuracy may result from a double-marker method devised by Richard King, an orthopedic surgeon at the University of Warwick in the United Kingdom.
Working in collaboration with Damian Griffin, a professor of trauma and orthopedic surgery at Warwick Medical School, the pair developed KingMark™, a double-marker calibration device that measures radiological hip magnification. The kit consists of a pad with an incorporated measurement system that includes two separate radio-opaque markers – one behind the pelvis and one in front – as the patient lies with his or her hips on the pad. A string of five linked precision balls is placed on the patient’s abdomen; the anterior (ball) and posterior measurements from the radiograph are entered and calculated. An accurate value for magnification is then generated. This system is less intrusive than the measurement systems currently in place, and is better at generating measurements for larger patients. Voyant Health of Columbia, MD began distributing this technology in the U.S. in March of 2010.