Research focusing on the CoxaTrain to treat osteoarthritis of the hip

Run by Hannah Steingrebe, a study conducted at Karlsruhe Institute of Technology (KIT) examined the biomechanical and clinical effects of the CoxaTrain in patients suffering from mild to moderate osteoarthritis of the hip. The data obtained substantiates its effectiveness and opens up new prospects for the use of flexible hip braces when treating osteoarthritis. This is our interview with the Sports and Movement Scientist about key results that have been published so far.

Hannah Steingrebe: The major finding for me is that wearing the brace reduces pain. Most of the 21 test subjects reported that – not just during normal walking, but across all the movement tasks. After one week of wearing the brace, they felt less pain and greater mobility, both when subjected to strain and at rest, even at night when the brace is no longer being worn actively.

Hannah Steingrebe: For patients and physicians, pain reduction and improvement in function are crucial. These are the parameters we want to cover from different angles. In our study, the participants had to have unilateral osteoarthritis and be accustomed to a certain activity level, allowing function tests, such as the six-minute walking test and complex movement tasks. Using questionnaires, the pain level was recorded every day via the Visual Analog Scale – one week without a brace and seven days while wearing the brace. We systematically asked which movements caused pain and when, including at night, for example. The patients also kept a wearing journal.

“For patients and physicians, pain reduction and improvement in function are crucial.”

Another question was whether we are able to substantiate biomechanical effects as well and to connect them to clinical improvements. What kind of changes would we see in relation to gait or joint strain, for example? A 3D movement analysis with a camera system and two force measurement plates delivered the data we needed.

Hannah Steingrebe: We can observe possible effects triggered by the brace on the hip’s range of motion more precisely during these tasks. Compared to simply walking in a straight line, they make more demand on the muscles, provide more differentiated information on what effects the CoxaTrain has on movement patterns and whether normalization of gait can be achieved. Effects on hip extension can be particularly well represented during walking in a straight line. When taking turns and climbing stairs, on the other hand, effects in the frontal and transverse plane come to the fore more effectively. Taking the stairs primarily makes demands on hip adduction; taking 90-degree turns targets internal and external rotation. Research has shown that osteoarthritis usually limits hip extension and reduces adduction. Patients tend to avoid internal rotation because of the pain. In particular with patients like we’ve included in our study, those who are physically active and mainly have mild to moderate symptoms, restrictions will only become apparent during challenging tasks. We can therefore work out how a flexible brace can help them remain active.

Hannah Steingrebe: These two ways describe how you can take a turn: If the affected leg is on the outside when turning, we refer to it as a step turn. If you’re turning via the leg on the inside, it’s a spin turn. The step turn and spin turn require different movement patterns, particularly concerning hip joint rotation. The majority of everyday movements has this type of turn. That makes it relevant for us to check whether the CoxaTrain has an impact on that. We therefore wanted to investigate both types during the study. And it turns out that the effects were different, more significant during the spin turn. When the test subjects were wearing the brace, we measured an increased initial speed, which may indicate greater confidence when moving, and reduced range of motion in the hip in the transverse plane, i.e. less rotation – yet with joint torque remaining the same.

Hannah Steingrebe: Reduced internal rotation is typical for a changed gait in patients suffering from osteoarthritis, but we didn’t notice increased joint strain at the same time. With regard to the clinical effects we observed – reduced pain and greater functional abilities – this result indicates an improvement in the remaining range of motion. When wearing the brace, patients seem no longer able to reach the painful end points. They therefore become altogether more mobile and sometimes also faster. So the interesting question is: To gain greater mobility, do we want to extend or restrict range of motion? That always depends on the movement direction and the movement task we’re performing, as well as the joint strain that occurs at the same time. So we always have to put it in perspective.

“Within the remaining range of motion, when wearing the brace, patients seem no longer able to reach the painful end points. They therefore become altogether more mobile and sometimes also faster.”

Hannah Steingrebe: We observed a reduction in pain during both movement tasks when the brace was worn. We also noticed that patients used the range of motion available to them more effectively. Turning is mainly about hip joint rotation because the body’s center of gravity has to be adjusted to a new direction. Climbing stairs, however, illustrates hip adduction and therefore pelvic stability very well. When going up or down the stairs, we have to lift or decelerate our body’s center of gravity, which we compensate for via the torso, for example. Many people suffering from osteoarthritis of the hip will tend to tilt the pelvis forward at some point to compensate for limited hip extension. The more damaged the joint is, the more this happens. This transfers loads to areas that are not designed for it. This results in subsequent damage, in the sacroiliac joints, for example. When the CoxaTrain was worn, we were able to prove straightening of the pelvis. The brace directly counteracts the osteoarthritis-related pattern in this case, and can promote a more physiological gait.

Hannah Steingrebe: Climbing stairs was the only movement task where the brace increased hip extension. But this may have to do with the fact that there is less maximum hip extension than when turning or walking in a straight line. Patients don’t reach the painful end points of their range of motion here either, and can improve their joint function.

“The answer to what a brace offers and in what area depends on the person and their expectations as well as requirements.”

Hannah Steingrebe: That has to be considered in the respective context. The answer to what a brace offers and in what area depends on the person and their expectations as well as requirements. Plus, pain levels fluctuate with mild osteoarthritis of the hip. That means there will be phases with greater pain and those where patients have practically no problems whatsoever. If the intervals between measurements are long, the probability will be greater that different phases of pain and therefore temporary effects can be recorded. It was our objective therefore to keep timings of the measurements quite close together, but not just record immediate effects triggered by the brace. After one week of wearing the brace, the test subjects had got sufficiently accustomed to the CoxaTrain so it was able to exert its effectiveness at a muscular level. Patients were therefore able to judge quite well whether their hip pain had reduced after wearing the brace. During the six-minute walking test, they were able to see that their maximum walking distance without feeling pain had increased. This really contributed to motivation.

Hannah Steingrebe: Osteoarthritis of the hip does not exclusively manifest in the hip. We found the most significant effects in the pelvic segment, simply because of the anatomical proximity, but also because of the brace’s circular compression and impact on the sacroiliac joints. Movement of the upper body, on the other hand, does not seem to be affected much during the mild to moderate stage. We didn’t spot many changes in the knee joint either in comparison, except individual increased joint torques. But that doesn’t have to indicate a risk of osteoarthritis of the knee. It may just have to do with the walking speed. When the brace was worn, we noticed during all movement tasks that speed had increased. When we walk more quickly, we generate greater ground reaction forces that affect joint torque. Long-term effects on muscle activity would therefore be interesting for future research on osteoarthritis of the hip, and to what extent load is transferred to other joints.

“Improvements within the available range of motion can contribute to almost painless mobilization, helping to delay joint replacement.”

Hannah Steingrebe: In order to detect osteoarthritis of the hip early and to treat it conservatively, a biomechanical movement analysis is beneficial. A tell-tale diagnosis factor is, for example, when patients start to avoid internal rotation to prevent pain. A flexible brace, like the CoxaTrain, can then be a solution for active patients in particular who are not yet severely restricted. Supported by the brace, they can maintain their physical activity more effectively, thus remaining stable in the muscles. A return to the physiological gait doesn’t always have to be the treatment objective. Improvements within the available range of motion can also contribute to almost painless mobilization, helping to delay joint replacement. But if surgery does become necessary, rehabilitation will usually be easier when the muscles are well developed. The cardiovascular system also benefits from activity. We therefore have a small lever here that can have a great effect on staying healthy.

Pain-alleviating mobilization using CoxaTrain
The CoxaTrain hip brace provides relief while walking and significantly reduces pain in the lumbar-pelvic-hip region, offering positive effects on functional abilities. The brace surrounds the pelvic girdle with circular compression, stabilizes the hip as well as lower back, and helps relieve the often painful sacroiliac joints (SI joints). Two SI joint friction pads, the Gluteal Pad and the flexible Trochanter Pad exert a massage effect during walking, thus relaxing the muscles carrying out movements.

More about the KIT study
Comprehensive information on research background, study design, methodology, and the measured clinical effects can be found here.

Topic-related articles
CoxaTrain evaluation study

Kinesiotherapy with a hip brace

Study relating to osteoarthritis of the hip substantiates the effectiveness of the CoxaTrain brace

Pictures: Udo Schönewald, Bauerfeind AG, private