The number of hip joint surgeries, performed in this country, is increasing by the year. In 2005 almost 14 000 worn out hips were replaced by prosthesis. But even though problems with hips, knees and ankles are so common, there is a big demand for cheaper, more reliable and easier to use equipment for measuring the mobility of these joints. Such equipment is currently being developed at Umeå University.
”What the orthopedist wants to know after a hip replacement is whether it was successful and if the new hip is working in a good and functional way. It may sound very simple but it’s not that easy.”
This says Ronnie Lundström, professor in medical technology and in charge of the project that is developing portable equipment for pre- and post surgery measurements of joint mobility. He says there are different concepts for how to repair a defected hip, but no real science on which method that gives the best results. When a patient’s walking and mobility patterns are being registered after surgery, it is done in a clinical gait laboratory, using analysis based on camera systems. The movement laboratories are expensive and space demanding, there are only a few in Sweden. They also require that the patient is able to come to the clinic, which is not always possible since hip problems often affect older people.
The idea behind Lundström’s project is to develop a new kind of measuring instrument that is portable, cost-effective and easy to use, all in one. The method is based on a number of sensors being attached to the body part, in this case the hip. These sensors will send wireless signals to a portable computer. Through advanced mathematics the measurement results will then presented as a set of different graphs.
“We have a designer tied to the project who is now working on these sensors”, Lundström informs, “at this point we can perform certain tests, but the sensors are not wireless yet.”
Each sensor consists of gyros and accelerometers. A gyro measures the change in angle while the accelerometer measures the change in speed. Each sensor therefore provides information about the body parts movement and displacement in three dimensions.
In the tests that have so far been performed in the walk laboratory, the results from the new instrument have been compared to the ones from the established, camera based method.
“It has been very successful” says Lundström, “we have used the camera based method as a standard and gotten a very good agreement between the different ways of measuring, so it is looking real promising.”
Promising, is a word that keeps coming back in describing the project. The potential for the portable measuring equipment is massive.
“One of the reasons the project is based on hip joint problems is that there was an interest from the orthopedist department here at the hospital” says Lundström, “but we knew early on that the method can be generalized and applied in a number of areas.”
The project is also very interesting from the aspect of working environments, for example in the areas of ergonomics and strain injuries. Today there are no good methods for measuring the physical loads of different forms of heavy manual work. The methods that are available are neither user friendly nor efficient.
“The wireless measuring system we are developing, will make it possible to register every single movement throughout the whole working day. Today, there is no comparable way to quantify physical load” says Lundström.
He also believes the technique could facilitate or replace a number of the measurements in sports medicine and stresses the importance of the equipment being user friendly and accessible for all kinds of doctors, physiotherapists, orthopedics and therapists.
The project is planned to run for three years and Lundström is hoping to have a product ready for the market shortly thereafter.
“There is so much more than research and science that have to work out before you have a commercial product” he says, “but like I said before, everything is looking really good, only a few pieces are missing.”
CMTF, c/o Tillämpad fysik och elektronik
Umeå universitet, 901 87 Umeå
Tel: +46 (0)90-786 96 38.
E-post: Britt Andersson.
