Background
The shoulder is one of the most mobile joints in the body. However, it is also the most frequently dislocated joint in the body and is more at risk of becoming unstable in comparison to other joints. The many ways in which we can use our shoulder to complete tasks makes it challenging to understand how and why we use our joints and muscles in the way we do. It can therefore be difficult to understand why someone’s shoulder is unstable or the best way to manage it. By using 3D motion analysis technology such as 3D cameras (often seen in gait labs / video games or movies) and surface electromyography that measures muscle activity, along with 2D ultrasound for imaging the muscles, we have undertaken research to identify why shoulder instability might occur in people affected by different conditions.
Our research
In research led by Dr Fraser Philp, our researchers have completed two separate but similar studies. In the first study we used 3D movement analysis to look at the arm movements and muscle activity patterns of young people with and without shoulder instability. The young people were aged between 8 and 18 years of age. They attended the movement analysis laboratory where our technology captured how they moved their arm and which muscles they used. We also kept in contact with participants for a year to find out how many further episodes of instability they had.
In our second study we measured adults with and without Facioscapulohumeral dystrophy (FSHD), a muscle disease which can affect muscles around the shoulder girdle. In addition to the arm movements and muscle activity patterns we took images of their arm muscles to see what information could be helpful alongside the 3D measurements.
What’s involved?
We worked closely with partners at the Orthotic Research and Locomotor Assessment Unit (ORLAU) and their movement analysis laboratory. In order to take the 3D measurements, we had to identify lots of bony surface landmarks on which we could put the reflective markers and the relevant muscles. Once the markers and surface electromyography devices were in place and checked to be working, we asked participants to complete a series of weighted and unweighted arm movements which we recorded.
For the ultrasound images we took measures of how thick the individual muscles were as well as information on how dark or light the muscle was, which in some cases can be used as an indicator of quality.
Our findings
In both studies we were able to identify differences between people with either shoulder instability and FSHD and their respective matched groups who did not have problems with their shoulders. In both cases the research has shown where the main differences are and what might be helpful for informing future research or clinical decision making in the future.
Acknowledgements
This research was funded by the Private Physiotherapy Education Foundation and The Orthopaedic Institute Limited.