Measuring results step by step – zebris motion analysis

Embedded in plates or treadmills, sensors that measure the pressure distribution during walking are efficient tools to help diagnose and treat misalignments or to assist in rehabilitation. They enable comprehensive motion analysis without the need to invade the patien's body. Zebris offers this type of biomechanical measuring technology in different device solutions.

In this interview with MEDICA.de, Stefan Lehnen explains how the zebris pressure sensor technology works, details the company’s available device solutions and describes what this type of measuring system is generally able to accomplish in the field of orthopedic care.

Mr. Lehnen, how does the zebris pressure distribution measurement platform for gait and stance analysis work?

Stefan Lehnen: The FDM measuring system uses premium capacitive force sensors that are arranged in matrix shape in various platform sizes. Each sensor has its own calibration curve. The capacitive measurement principle is similar to how a plate-type condenser works. The dielectric is located between two electrodes and determines the distance between these two electrodes. Thanks to the material properties of the dielectric and the exerted pressure on the platform, the distance between the electrodes and hence the capacity of the condenser changes.

If pressure is no longer being exerted, the dielectric returns to its original position. The advantage of the capacitive measurement principle over resistance measurement is its resistance to temperature variations.

Measurement accuracy is ensured by calibrating the individual sensors. Contrary to the resistance measurement principle, a capacitive sensor is less susceptible to wear and tear and can maintain its accuracy over years thanks to recalibration.

The resistive system relies on resistance. Exerted pressure changes the specific resistance in the measuring surface, allowing a change in voltage to be detected. The temperature must be compensated with a specific circuit. Unlike calibrated capacitive sensors, measurement with resistive systems is less accurate.

All measuring results are displayed in real-time on commercially available personal computers.

The measuring results and various automatically generated reports are displayed on the computer with just a mouse click. The report has several pages and includes a chart of the important location and time parameters, such as stance, swing and double stance phases as well as step lengths.

You have integrated this measuring system in various device technologies. What technologies does your company offer?

Lehnen: The device technologies have a broad range of applications. We offer our pressure measurement technology as a classic base plate or in addition to a treadmill.

The base plate, which is integrated under the treadmill belt, also includes a pressure sensor matrix with individually calibrated capacitive sensors. Thanks to a process that was specially designed by zebris, the movement of the treadmill is being compensated, enabling the analysis of totally stable gait and rolloff patterns.

Zebris technologies and measuring systems are already successfully implemented in medical technology but also allow valuable insights about motion sequences and human gait pattern in the sports realm. The detailed analysis of the individual parameters can help to optimize training sessions and schedules: conventional gait analysis is complemented with the avatar-aided balori e-coordination training for balance and coordination and effective training of the putter’s motion in golf.

Where can your systems be applied?

Lehnen: Our systems are used to optimize motion sequences, to detect stress and strains on the body and to prevent pain and discomfort. They can also be used to treat injuries and for surgical applications.

What’s more, they measure the success of rehabilitation efforts and assist in the development and testing of auxiliary aids. The treadmill-assisted zebris Rehawalk® system is designed for the analysis and treatment of gait disorders in neurological, orthopedic and geriatric rehabilitation.

Training with an unweighting system is also an option, thus making the system also suited for patients who suffer from severe functional limitations and enabling them to start therapy even at an early stage of recovery.

The technological possibilities of Rehawalk® can be completely adapted to the patient's needs: the components can be adjusted to any application as prescribed by a therapist and cater to a wide variety of patients, including patients in wheelchairs, patients with reduced mobility and those who are capable of walking. The Rehawalk® system takes its place between the robot-assisted locomotor training and conventional gait therapy.

After an initial gait analysis to assess the current state, gait training via dynamic visual cueing makes up the core element of zebris Rehawalk®.

Thanks to the visual feedback, patients learn proper gait patterns under the direction of a therapist. The ideal gait pattern is projected onto the treadmill. The progress report documents the achievement of goals. Therapists can readjust the parameters at any time based on the patient's performance level. For optimal training control, two gait analyses – before and after a training period- can be compared.

The high number of step repetitions while training on the treadmill support the automation of motion sequences and can have a positive impact on cognition and coordination. Gait training through visual cueing can be already initiated during an early stage of treatment to make gait patterns symmetrical and rhythmic and increase the step length.

What are these types of biomechanical measuring systems generally able to accomplish in the orthopedic realm?

Lehnen: They offer a comprehensive analysis with objective measurement data and assist therapists, physicians, trainers and orthopedic technicians in analyzing and treating the human locomotor system. It is important to identify or predict the biomechanical causes of stress and strain. Targeted measures such as the right choice of footwear, special shoe inserts, physiotherapy, strength training and sensible training programs can remedy or even prevent these causes at the outset.

What are the advantages of your systems compared to other techniques such as X-ray?

Lehnen: 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.

Do you have any specific plans pertaining to the area of orthopedics?

Needless to say, we will continue to keep up with current trends in the medical technology market and translate them into future-oriented technologies – this has always been one of our core competencies. Every manufacturer obviously aims to meet the increasing clinical demands of interdisciplinary medicine. Our main ambition is to support physicians and therapists in successfully diagnosing and treating misalignments of the body and provide future-oriented solutions for rehabilitation. Ultimately, maximizing a patient’s therapeutic success is our primary focus.