When a patient receives a new hip, it is usually adjusted only approximately to leg length. Greater accuracy requires a more precise measuring process as well as adjustable implants. Now, a new type of measurement method coupled with a modular implant should allow orthopedic surgeons to precisely calibrate leg length after the operation so it matches its original length. The researchers will be introducing their development at the Medtec expo in Stuttgart, April 21-23 (Hall 7, Booth B04).
A painful hip that feels unstable and no longer has the same range of motion: For many patients, this means they need a prosthetic hip – something that happens to more than 200,000 people each year in Germany alone.
Implant manufacturers face numerous challenges; for example, the artificial joints may eventually break. In addition, orthopedic surgeons currently have no suitable method for precisely measuring leg length before the operation or for adjusting the implants accordingly.
The result is that after the operation, the leg can actually be longer or shorter than it used to be. This leads to problems with the spine, which have to be resolved using shoe inserts.
There’s a better solution on the horizon: With the completely new measuring technique developed by the Fraunhofer Institute for Machine Tools and Forming Technology IWU, orthopedic surgeons will be able to measure their patients’ leg lengths much more precisely.
The Fraunhofer researchers collaborated on the new system with several project partners: the Clinic for Orthopedics, Trauma Surgery and Plastic Surgery at the Leipzig University Hospital; University of Applied Sciences Zwickau and its Research and Transfer Centre; AQ Implants GmbH; and MSB-Orthopädie-Technik GmbH.
“The margin of error in our process is less than one centimeter,” explains Dr. Ronny Grunert, a researcher at IWU. “Eventually we’d like to get that down to five millimeters.” Currently, the usual procedure calls for the doctors to determine leg length with a tape measure, which can lead to errors of up to two centimeters.
Here’s how it works: With the patient in a prone position, the doctor affixes a small plastic box containing two LEDs to the patient’s shin. The doctor then takes hold of the patient’s heel and lifts it upward. With that motion, the two lights trace an arc that is recorded by a camera positioned about 1.5 meters to the side of the patient.
The principle is similar to that of a compass. The hip joint, from which the leg “hangs,” is essentially the point of the compass, while the LEDs act as the pencil. If the distance between the two changes, i.e. if the leg becomes shorter or longer, that will change the arc traced by the LEDs. The doctor takes this measurement twice – once right before the operation and once after the implant has been temporarily inserted. The box remains on the leg during the operation.
A software program compares both arcs to determine if the leg is the same length it was before the procedure. If necessary, the doctor can make adjustments to the artificial hip. Initial testing of a measuring system prototype has already met with success at the Leipzig University hospital. There are plans for a clinical trial later this year, and the new system could be on the market in about two years.
Unbreakable, adjustable hip implants
Fraunhofer’s researchers also optimized the hip implants, again working together with partners from industry, medicine and research. “We’ve developed an implant that can be adjusted to each individual patient,” says Grunert. The trick was to do away with prefabricated implants in various sizes and use a modular system instead.
In this method, the doctor can select the right hip stem as well as the right neck for each patient. Special screw connections are used to attach the individual parts to each other and the combined unit is implanted in the hip for testing. The doctor now measures the leg length, and, if necessary, can easily separate the implant’s various components to exchange them for better-fitting parts or adjust them as required.
Another advantage is that the artificial hip is less prone to breakage than conventional modular models with a conical clamping ring. Currently, the doctor connects the stem and the neck of the prefabricated artificial hip during the operation with a well-placed stroke of the hammer. This puts tremendous stress on the connection point, a conical clamping ring.
Furthermore, once the parts have been joined together, it’s virtually impossible to separate and adjust them. That’s not the case for the specialized screws that hold the parts of the new implants together. The point where they connect is mechanically stable and prevents the implant from breaking.
The new system was developed within the “artificial joints” cooperative network, which is funded by the Federal Ministry for Economic Affairs and Energy (BMWi) and coordinated by Fraunhofer IWU. At the Medtec expo, the researchers will present the leg-length measuring system and the modular hip implant as well as the artificial joint network.
Britta Widmann | Fraunhofer-Gesellschaft
AchemAsia 2019 will take place in Shanghai
15.06.2018 | DECHEMA Gesellschaft für Chemische Technik und Biotechnologie e.V.
Insects supply chitin as a raw material for the textile industry
05.06.2018 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences