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Revision as of 10:23, 11 September 2015 by Friedmar Graichen (Talk | contribs)

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History of the Biomechanics Laboratory

The Biomechanics Laboratory was founded in 1973 by the orthopaedic surgeon Dr. Reinhard Kölbel in the Orthopaedic Hospital of the Free University Berlin at the foundation 'Oskar-Helene-Heim'. After studying biomechanics in England for a year he built up a new research laboratory from scratch. In 1974 a young mechanical engineer, Georg Bergmann, and a technician joined Reinhard Kölbel. The first research projects dealt with fixation strength of cemented artificial joints and a newly developed artificial shoulder joint. In 1975, Antonius Rohlmann and an assistant medical technician joined the team for a research project concerning hip prostheses. This was one of the worldwide first projects applying a finite element model in biomechanics.

Inspired by the wire-bound force measurements in hip implants by Rydell in Sweden in 1966, the idea arose as to measure the forces acting in the shoulder joint. Georg Bergmann developed a new method of measurement, the so-called 'Matrix method', which requires only one sensor per load component to be measured. The new method for measuring loads in joint implants was first presented at the Pauwels symposium organized by Reinhard Kölbel and Georg Bergmann, and held in Berlin in 1979. Reinhard Kölbel left the Oskar-Helene-Heim and the Biomechanics Laboratory in 1979, and Georg Bergmann became the new head of the laboratory.

When applying for a grant to develop an instrumented shoulder joint, one reviewer suggested developing an instrumented hip joint instead. The new method was tested first in the hip of a sheep. At that time the signals of the load sensors (strain gauges) were transmitted via cable to a plug in the skin of the sheep. From an ethical point of view, application in a human was only possible when using wireless data transmission. This required the development of a telemetry unit. A four-channel telemetry transmitter was developed by Georg Bergmann in collaboration with Josef Siraky, an electronic engineer who worked part-time in the Biomechanics Laboratory. This telemetry employed a previously unknown amplification principle for the strain gauge signals, having the advantage of a small but accurate circuitry and low power consumption. Friedmar Graichen joined the team in 1983. He improved the telemetry and actually got the first devices fabricated and working, despite the stone-age microelectronics at that time. He furthermore developed the external equipment for an inductive power supply of the implantable telemetry transmitter and for storing the signals received on the audio track of an external video tape recorder. In 1985, telemeterized hip joints for the sheep were implanted and tested for up to three years.

The first telemeterized hip joint was implanted in an 82 year-old patient in 1988. It allowed the measurement of the three force components acting on the prosthetic ball, and also the temperature in the neck of the implant. In the early 1990s, a telemeterized internal spinal fixation device was developed. It allowed the measurement of three force and three moment components as well as the implant temperature. Towards this aim, an improved eight-channel telemetry transmitter was developed by Friedmar Graichen, using a bipolar integrated circuit. The first pair of spinal fixators was implanted in 1994. Under the guidance of Antonius Rohlmann these temporary implants were used in 10 patients. In the 1990s, another kind of hip prosthesis with a hollow shaft was instrumented with strain gauges for load measurements and additional 10 sensors for measuring the temperature distribution within the implant. In 2004 further miniaturisation leads to the actual 9-channel telemetry transmitter with a programmable custom-made integrated circuit using BICMOS technology for the instrumentation of other implants.

In the first decade of the 21st century telemeterized shoulder joints, knee joints and vertebral body replacements were developed. The first telemeterized shoulder joint was implanted in 2005, the first vertebral body replacement in 2006, and the first knee joint in 2007.

In 2001, the Biomechanics Laboratory moved to the University Hospital Benjamin Franklin of the Free University Berlin. In 2004 this hospital merged with the Charité – Universitätsmedizin Berlin, which is the common hospital of the two largest Berlin universities, the Free University and the Humboldt University.

In 2008 the Biomechanics Laboratory merged with the Research Department of the Center of Musculoskeletal Surgery of the Charité (Head: Prof. Georg Duda) to the Julius Wolff Institut. This combines the research power of both groups. The combined work with musculo-skeletal models plus movement analyses for the calculation of forces inside the body and the accurate load measurements with instrumented implants promise to grant big improvements for the biomechanics of human loading conditions. We hope and are convinced that this work is not only important scientifically but that it will also help patients with musculo-skeletal disorders as fractures, implants or arthritis.

In 2001 we published a collection of selected load data from the hip joint plus gait analyses plus load calculations on compact disc ('HIP98'). The consequential success and wide usage of this data collection motivated us to build up even further the web-based public data collection OrthoLoad. In its final stage it will contain a huge amount of load data from hip, shoulder, knee and spine. The work on this data base does not meet the common criteria of scientific success as impact points and funding money, but it will preserve the outcome of 30 years of scientific work and make it available to the scientific and medical community and the medical industry. This way we hope to remunerate society for some of its investment in our work.