The ManuTrain being put through its paces

Compliance is often a question of comfort. For this reason, Bauerfeind has redesigned the ManuTrain and replaced the support’s rigid inner hand stay with a more flexible strap system. Is the medically required wrist stabilization still the same? This has been confirmed by a technical test procedure in FH Münster’s Biomechatronics Laboratory.

The hand and forearm are mat red, flexibly connected with edges in the area of the wrist. Study Director Maxim Kirillov, M.Sc., skillfully dismantles the model – or “phantom” as he likes to call it – on the test rig. “This phantom is based on the 3D scan of a male test subject’s hand,” Kirillov explains, “we did without replicating the muscles and soft tissue to ensure a high degree of test reproducibility. We replicated skin friction properties with 2 mm PU hard foam.” The new ManuTrain is quickly put on, and a digital sensor is attached to the blue fascia strap.

FH Münster’s Biomechatronics Laboratory has performed a stabilization test: how effectively does the new ManuTrain featuring a strap system stabilize the wrist compared with its predecessor generation with an inner hand stay? Prof. Dr.-Ing. David Hochmann, Laboratory Director and expert for medical technology test procedures, explains: “The demand for substantiating products and their functions using measurement technology is constantly increasing. In orthopedic technology, however, it’s often no longer possible to create a new test for every product because of the large number of products and low quantities. We therefore work with adaptable universal test rigs, modular models of different body parts and numerous sensors. We can use these tools flexibly with our knowledge and experience and continue to develop them. This means we can answer specific questions with little effort in a short time.” As was the case with the new ManuTrain, which has been on the market since February.

A specially developed procedure

The frame of the universal test rig starts to move without a sound. The model carries out flexion and extension movements. The data for joint angle, joint moment and strap forces is transmitted to a measuring amplifier. Graphs and readings appear on Maxim Kirillov’s laptop monitor. The Study Director and doctoral candidate has designed, performed and evaluated the test. He explains the test procedure: “There are no specified standards yet in the area of orthopedic engineering. So we had to develop a procedure and validate it in accordance with VDI Guideline 5703 [editor’s note: published by the Association of German Engineers]. We already had a test procedure for hand braces in our portfolio, which we were able to adapt for the test on supports with stabilizing elements.” The precise details of the test setup were crucial. “Our existing model consisted of hand and forearm sections, connected via a hinge in the center of the joint,” Maxim Kirillov describes. The phantom is suitable for tests with braces. What was missing for tests with supports was an extensive area anatomically replicating a human forearm. “We therefore had to modify our phantom to support the strap in the wrist area.”

Measurements were taken for the resistance of the support which underwent wrist movements of 15 degrees’ extension and -25 degrees’ flexion triggered by the compression-tension testing machine. This resistance allows the scientists to conclude the degree of limitation of the anatomical range of motion and therefore the stabilizing effect of the stay and strap system. Maxim Kirillov explains the processed data: “The ManuTrain from both generations demonstrates comparable behavior in flexion and extension directions, meaning their functional capacity is the same. With the ManuTrain featuring the strap system, the maximum values fluctuate a little more between the individual measurements.” It was therefore verified that the improved wearing comfort of the ManuTrain featuring a strap is not accompanied by a deterioration in the stabilization effect.

Interaction between patient and medical device

Maxim Kirillov turns off the test rig; the model hand remains suspended. What conclusions for medical effectiveness can be drawn from the measurements? Study Director Kirillov emphasizes clearly: “Our test procedure can only detect differences or similarities between devices, in this case between the ManuTrain with a stay and the ManuTrain with a strap. Clinical research has to work out whether and which differences are relevant to treatment.” Examinations using testing technology nevertheless provide valuable insights into the extent and transferability of product features, and allow the researchers to measure the interaction between the patient and the medical device. Prof. Hochmann sees increased potential for the professionalizing medical retail industry: “We have developed a small AFO test rig for medical retailers, for example, and successfully tested it in some companies. It can be used to test their own products or 3D printed parts, and it allow them to document changes for the health insurance companies and justify the provision of a new product.”

ManuTrain

The new generation of the ­ManuTrain support stabilizes the wrist using an adjustable system comprising a stabilizing strap (partly elastic) and a fascia strap (elastic), instead of an inner hand stay. The ManuTrain alleviates pain in cases of osteoarthritis, tenosynovitis or during long-term post-operative follow-up care by exerting compression and limiting wrist movement. Depending on how the wearer feels, the stabilizing strap can be removed, followed by the fascia strap during further improvement, to allow for three activity levels. The highly textured knitted fabric keeps the ManuTrain securely in position, even during movement.

Images: Bauerfeind, Sven Hillert