Robotic Arm Reaches Out To Knee Surgeons

Orthopedic surgeons have found a helpful hand, or more precisely a robotic arm, that will allow them to perform more accurate knee surgeries. MAKO Surgical has released a Robotic Arm Interactive Orthopedic System that is designed to assist surgeons during knee resurfacing operations. This medical robotic arm has just been selected by R&D Magazine as a winner of the 48th Annual R&D 100 Awards, identifying it as one of the 100 most technologically significant products introduced into the marketplace over the past year.

More than 10 million Americans have knee osteoarthritis, and it is the most common cause of disability in the United States. Osteoarthritis occurs when the cartilage between two bones is worn down and the bones begin to directly rub against each other at the joint. The main problem for knees is the deterioration of the articular cartilage, the smooth lining that covers the ends of the leg bones where they meet to form the knee joint. This cartilage deterioration typically leads to pain, stiffness, limited range in motion of the knee, localized swelling, and the formation of bone spurs (small growths of new bone). The pain is usually worse after activity.

Knee osteoarthritis is diagnosed based on medical history, physical examination, x-ray imaging and possibly MRI (magnetic resonance imaging). Although many people with osteoarthritis don’t need surgery, in some cases surgery is required. Surgery may involve joint replacement in which the rough worn surfaces of the joint are replaced with a smooth artificial material, such as metal or plastic pieces.

Most people affected by osteoarthritis of the knee are older than 45 years. However, some younger active patients have early osteoarthritis. Such patients with arthritis in only one area of the knee can have partial knee resurfacing surgery, which is significantly less invasive than standard total knee replacement surgery. Partial knee resurfacing replaces only the deteriorated section of the knee with a small partial knee implant, without disturbing the knee’s healthy tissue. The benefits of this less invasive surgery can be significant: smaller incision, less bone removed, less discomfort, shorter hospital stay, less physical therapy required, and more rapid healing. Since less bone is removed (about 0.25” instead of 0.5”), future total knee replacement surgery can also be more easily performed, if necessary.

However, partial knee resurfacing can be a difficult operation to perform. Using the MAKO robotic arm system to assist with the surgery will hopefully provide increased stability and precision. It also allows the surgery to be performed for a greater number of patients, since it allows the replacement of the top (patellofemoral) portion of the knee joint instead of just the inner (medial) or outer (lateral) portion. The system provides patient-specific, pre-surgical planning with 3-D modeling based on CT (x-ray computed tomography) images. The system also provides real-time visual, tactile and auditory feedback during the surgery. This should enable the orthopedic surgeons to more precisely position the partial knee implants. Hopefully this new technology will help provide a more natural feeling artificial knee and a healthier active lifestyle to some people that suffer from knee osteoarthritis.


The Workings of Fireworks

fireworks racks
Racks of cylindrical mortars used to shoot off shells into the air. Each has a fireworks shell inside, with only the main fuse visible.

My friend is a licensed pyrotechnician. Every July 4th, I help her setup and fire off a local city’s fireworks show. When you experience a fireworks show from below, you see, hear, feel and almost taste the fireworks. You are also privy to the behind the scenes drama as the fireworks is hand lit, like watching a play from back stage. It is hard to ever go back to watching the pretty lights up in the sky from far away. And it has made me appreciate fireworks more, even from a scientist’s perspective.

There is more to fireworks than pretty lights up in the sky. How are the bursts of colored light created? How do they make the different effects? How do they get up so high in the sky? There is plenty of science behind a fireworks show.

Shell being placed into a mortar.

Black powder is used to lift each fireworks shell into the air. It has been around for many centuries. It is a combination of potassium nitrate, charcoal and sulfur. If you burn black powder in the open, the heat and gas from the explosion quickly dissipates. So you put the black powder inside the bottom of the fireworks shell and place the fireworks shell inside a mortar (launch gun). This allows you to trap the heat and gas from the burning black powder, causing the gas pressure to build up until an explosion launches the fireworks shell high into the air. The fireworks shell must fit snugly in the mortar, or pressure will escape and cause a misfire. A variety of different sized shells and corresponding mortars are used to create an interesting fireworks show.

Lighting fireworks
Lit fireworks shell just before it shoots into the air.

The heart of a fireworks shell is the multiple compartments of combustible materials, called stars. Each kind of shell consists of different kinds of stars, in order to get the different colors and effects that we all enjoy. Great care goes into a shell design. Each star is made from a combination of binders, oxidizers and coloring agents. Binders (typically dextrin) are used to hold everything together. Oxidizers are used to produce the oxygen needed for the mixture inside the star to burn. The most common oxidizer is potassium perchlorate. Perchlorate ions have a chlorine atom bonded to 4 oxygen atoms, so perchlorates are relatively stable compounds that release a lot of oxygen. The fireworks colors are imparted by different metal compounds, such as: magnesium or aluminum for silver; strontium carbonate for red; calcium salts for orange; sodium oxalate for yellow; barium nitrate for green; and copper carbonate for blue.  As a star burns, the perchlorate releases oxygen and its chlorine combines with the metal compounds to form metal chlorides. These metal chlorides release energy in the form of visible light when they reach high temperatures. The color (and wavelength) of the emitted light varies with the temperature and metal compound. Blue is the hardest color to produce, because it requires a higher temperature.

A fireworks shell is ignited by lighting the main fuse. This simultaneously lights both a fast-acting side fuse and a slow time-delayed fuse. The side fuse quickly ignites the black powder to launch the shell high into the air. The time-delayed fuse burns slowly into the center of the shell as it hurls into the sky, causing the aerial fireworks display when it reaches and ignites the stars. The amount of black powder in each shell is precisely determined so that the time-delayed fuse ignites the correct star compartment when the shell is reaching the apex of its upward flight.

Fireworks Finale
Fireworks display.

A shell can also contain sound charges, creating the exciting crackling, bangs and booms to accompany the light show. When you watch fireworks, you see them much sooner than you hear them because light travels much faster than sound.

So when you watch fireworks on Sunday, you may want to think about all the science that goes on to produce the show. Or you may just want to “ooh” and “ah” in appreciation of the beautiful aerial display. Just make sure that you verbalize your pleasure, because the crew working the show will love hearing your encouragement.

Is Ginger Better Than Advil?

fresh ginger
Courtesy of Creative Commons

I just spent a sunny Sunday afternoon pulling weeds up on my hillside, and now my lower back is complaining. I guess I overdid it. Normally I’d stretch for a while and take a couple Advil, but maybe I should take ginger instead?

University of Georgia researchers have found that ginger reduces muscle pain caused by exercise. Their results were recently published in the Journal of Pain. They compared the effect of taking ginger capsules to  ”dummy” placebo capsules on muscle pain. Volunteers took either raw ginger, heat-treated ginger or placebo capsules for 11 days. The volunteers performed strenuous arm exercises on the eighth day, and the researchers assessed their pain level and various measures of inflammation during the final three days.

This was a “double-blind, placebo controlled, randomized” study, which simply means that neither the volunteers nor the researchers knew who was getting the ginger capsules. This is particularly important for these kinds of studies. Rating your pain level is subjective and can be affected by whether you think you’re taking the ginger.

The strenuous arm exercises induced mild muscle pain 24 hours later. However, the muscle pain was rated to be 25% lower by the volunteers taking ginger than those taking the placebo — a moderate-to-large reduction in muscle pain.

The researchers claim that ginger consumption may be more effective than nonsteroidal anti-inflammatory drugs (such as aspirin or ibuprofen), based on past studies performed by others. Ginger has also been shown to reduce hip and/or knee pain in osteoarthritis patients.

However, it is important to recognize that you have to take ginger for several days for it to work. Unlike ibuprofen, you can’t just take a couple ginger tablets (after overdoing it in the garden) and wait an hour to feel better. So if you know that you’re going to be a weekend warrior, you might want to plan ahead and take ginger capsules during the week.

Solar-Powered Drip Irrigation May Save Lives in Africa

Americans spend on average 12.4% of their paycheck on food according to the U.S. Department of Labor’s latest survey. In contrast, sub-Saharan African communities spend 50-80% of their income on food, even though they are engaged in agricultural production as their main livelihood. These communities rely on rain-fed agriculture for crop production, despite having a short annual rainy season of only 3-6 months. Traditionally women and girls are responsible for hauling water by hand from very long distances in order to grow some crops, particularly during the long dry season.

Only 4% of cropland is irrigated in sub-Saharan Africa. Clearly irrigation could help improve quality of life for these food-insecure communities, if a water source is available. The most efficient type of irrigation for such a dry climate is drip (micro) irrigation, which delivers water and fertilizer directly to the roots of a plant. Low-pressure drip irrigation systems require only 1 m of pressure to irrigate plots of up to 1,000 square meters (0.25 acres). However, this irrigation technology requires access to a reliable water source.

One solution is a photovoltaic-powered drip irrigation system that combines the efficiency of the drip irrigation with the reliability of a solar-powered water pump. In such a system, a photovoltaic solar array powers a surface or submersible pump (depending on the water source) that feeds water into a reservoir. The reservoir then gravity-distributes the water to the low-pressure drip irrigation system. Energy is stored via the height of column of water in the reservoir. These systems can be configured so that no batteries are required. The pump only runs during the daytime and the system passively self-regulates. Namely, the volume of water increases on clear hot days when plants need the most water.

This kind of solar-powered drip irrigation system was tested in two rural villages in Northern Benin. The systems were installed and financed by an Non-governmental Organization, Solar Electric Light Fund, with the goal of boosting vegetable production from communal gardens in order to combat high malnutrition and poverty levels. The research was performed in collaboration with Stanford University. This NGO-academic research team scientifically evaluated the impact of the irrigation system on the community through a randomized controlled project that was rigorously studied and analyzed. The study results were recently published by Stanford University in the Proceeding of the National Academy of Sciences.

Three solar-powered drip irrigation systems were installed in two villages. Each irrigation system was used collectively by an agricultural group of 30-35 women, who each farmed her own 120 square meter plot and some additional shared plots used for group expenses. Researchers monitored these communities, as well as two “control” villages in which women’s agricultural groups grew vegetables by hand watering. This allowed a comparison between the solar-powered drip irrigation system to traditional watering method.

Each of the solar-powered irrigation systems supplied on average 1.9 tonnes of produce per month — including high-valued crops such as tomatoes, okra, peppers, eggplants, carrots, and greens — without displacing other agricultural production. The women farmers kept on average 18% by weight of the vegetables and sold the rest at local markets. As a result, vegetable intake across all villages increased by about 1 serving (150 g raw weight) per day during the rainy season. For the villages with irrigation systems, the vegetable intake rose to 3-5 servings per day even during the dry season. Overall the users of the irrigation systems showed remarkable benefits even in the first year, compared with the control households. The article states, “Their standard of living increased relative to the non-beneficiaries (by 80% of the baseline), their consumption of vegetables increased to the Recommended Daily Allowance, and the income generated by production of market vegetables enabled them to purchase staples and protein during the dry season.”

Hardly anyone is going to argue against the potential benefit of irrigation in Africa. However, one question remains — is the expense of a solar-powered system really necessary? The Stanford researchers would argue that it is, despite the expensive up-front costs. They compared their irrigation system with a hypothetical alternative system that used a liquid-fuel (gasoline, kerosene, or diesel) engine-driven pump, instead of the photovoltaic array and pump. This alternate pump can have significant problems, because fuel supplies can be unreliable and fuel prices volatile. According to their analysis, the solar-powered irrigation system is actually more cost effective in the long run, particular when fuel prices are high. It is also better for the environment since it doesn’t cause carbon-emissions.

The solar-powered drip irrigation system in the Benin project cost approximately $18,000 to install ($475 per 120 square meter plot) and requires about $5,750 ($143 per plot) per year to maintain. Based on the projected earnings of the farmers, the system should pay for itself in about 2.3 years. In addition, the cost of the photovoltaic arrays is expected to lower for larger-scale projects.

The project in Benin isn’t the only one underway. Solar-powered drip irrigation systems are also being installed by other groups in different areas of the world. For instance, the Sustainable Agriculture Water Management Project has installed solar-powered drip irrigation systems to 5,000 farmers in Sri Lanka’s dry zones. The hope is that these international efforts can provide substantial economic, nutritional, and environmental benefits to food-insecure impoverished communities.