Biomechanical measuring systems: Versatile tools for many disciplines

When human movements are no longer as smooth as they should be – due to misalignments or as the result of an injury for example – biomechanical measuring systems spring into action. Thanks to different types of sensors and optical technologies, physicians, therapists, and sports scientists embark on a search for possible causes and corrective options.

Biomechanics focuses on human movement patterns. Orthopedics uses corresponding measuring systems to diagnose the misalignment of joints. This allows for timely corrective interventions with physical therapy or auxiliary aids that prevent or at least significantly reduce damage to joints and bones. "Biomechanical measuring systems offer a comprehensive analysis with objective measurement data and assist therapists, physicians, trainers and orthopedic technicians in analyzing and treating the human locomotor system," explains Stefan Lehnen, International Sales Manager, zebris Medical GmbH in an interview with MEDICA-tradefair.com.

A typical example of this are plates that allow orthopedic technicians to measure the pressure distribution under the sole of the foot. This measurement indicates whether the patient has misaligned feet that affect all joints of the movement apparatus (foot, knees, and hips) and thus cause pain and potential joint damage. Based on this measurement, patients can receive custom-made insoles, which correct the alignment of the feet and steer walking patterns in the right direction again. "Joint misalignments, as well as strength and movement deficits, are dynamically assessed and training contents analyzed using video analysis, pressure distribution measurements, force measurements and functional analysis. Along with orthopedic examination findings, this enables a comprehensive picture of the dynamic pressure load situation, which is the basis for further orthopedic treatment or rehabilitation measures," adds Lehnen.

In addition to pressure sensors, biomechanical sequences are also measured with a multitude of other sensors and techniques. Optical systems like the DIERS formetric 4D (DIERS International GmbH) measure the patient’s back and spine in 3D and over a time sequence (4D). Dr. Marcel Betsch of the University Hospital RWTH Aachen and his team use this system: "By using a light projector, a horizontal light grid is projected on the back and pelvis of patients. This grid is recorded with a digital video camera and converted into a three-dimensional reconstruction of the spine via a computer system. This method is ideal for the treatment and monitoring of spinal disorders like scoliosis." The formetric 4D analysis system uses the surface of the back to calculate a model of the spine. Besides osteoporosis and scoliosis analysis, the system can also be used to study functional diseases that are diagnosed as part of neurological examinations and postural alignment tests.

Motion capture technology is also among the optical technologies used for biomechanical measurement. In this case, cameras measure the light reflection of markers the patient or test person wears on clothing. Motion capture originates in the movie industry and is used to create virtual characters. Perhaps the best-known example of this is "Gollum", a creature from the "Lord of the Rings" trilogy played by actor Andy Serkis – including facial expressions because they can also be transferred from a person to a virtual character using motion capture. This shows the biggest advantage of the motion capture technology: Its biochemical measurements are very precise and thus primarily relevant for research applications.

Optical technologies are increasingly important in biomechanics since they facilitate quick and non-invasive measurements. Meanwhile, measuring with sensors worn on the patient’s body is somewhat more cumbersome. One example of this are inertial sensors (acceleration sensors) like the MyoMotion system by Velamed GmbH. Says Betsch, "Up to 16 inertial sensors are attached to the joints, allowing us to accurately analyze the motions. Since they work with Bluetooth, patients can be examined in everyday situations such as climbing stairs or getting up. In doing so, we are not dependent on an artificial laboratory environment."

There are many different technical ways to make biomechanical measurements. We only mentioned a few of them. Meanwhile, the applications and diseases that can be diagnosed with this technique are just as varied. Orthopedics is not the only field that benefits from the use of high-tech sensors in biomechanics. Other disciplines such as geriatrics also enjoy the advantages.

When it comes to analyzing older adults, mobility and speed are often used as general health parameters. This is where biomechanical sensors and measurement systems can excel. Exams where older adults walk a certain distance, maintain their balance or stand up from a sitting position as fast and steadily as possible are frequently still conducted with analog tools, in this case by using paper, pencil and a stopwatch. The examining doctor or nursing staff must record results by "eyeballing" the patient.

Today, Dr. Betsch and his team already deliberate how biomechanical measurement can also be used in other fields of medicine. "I think we will have measuring systems in the future that easily measure the entire body in a relatively short time without the need of attaching markers to patients beforehand – similarly to how full-body scanners work at the airport. This would allow us to quickly obtain preliminary information about potential pathologies, which we could subsequently substantiate with further examinations." That's why it is just a matter of time before sensors and measuring systems make a better assessment of patients and their physical ability possible – and all of it in an absolutely contact-free manner.