I am a physiotherapist undertaking some research involving joint laxity at the shoulder.
How is glenohumeral anterior-posterior translation best quantified non-invasively? I have read a few articles on the subject – all using various methods. Cutaneous electromagnetic sensors have been used however my concern is that as they are cutaneous any joint movement will influence the results due to changes in the position of sensors from skin movement and changes in muscle bulk. Ultrasound avoids this limitation (and has recently been correlated with stress radiography showing good/excellent outcomes) however I wonder how difficult it is to identify the bony landmarks and maintain a reference point during active movement – I believe all studies to date have looked at passive translation of the joint in a static position. For my study it would be clinically more relevant to measure translation during active movement in order to take into account of the effects of dynamic stability/control. Any other ideas would be much appreciated.
Thanks
glenohumeral stiffness
This is also an issue of interest to me currently, as I am investigating shoulder pain and stability in hemiplegia. Methods have been developed at Case for the quantification of whole arm stiffness under dynamic conditions, and we intend to adapt these to the glenohumeral joint. Stochastic perturbations are applied to the joint using a robot manipulator and system identification techniques are used to quantify the stiffness and viscosity of the joint at various frequencies. I realise this is slightly different from what you are interested in, as it does not directly quantify GH laxity during movement. It does, however, provide a measure of stiffness under dynamic conditions and as such can inform us about likely changes to the stability of the joint.
The technique, as applied to whole arm stiffness, has been described in the following papers:
Perreault EJ, Kirsch RF, Crago PE. Multijoint dynamics and postural stability of the human arm. Exp Brain Res. 2004 Aug;157(4):507-17.
Acosta AM, Kirsch RF, Perreault EJ. A robotic manipulator for the characterization of two-dimensional dynamic stiffness using stochastic displacement perturbations. J Neurosci Methods. 2000 Oct 30;102(2):177-86.
Perreault EJ, Kirsch RF, Acosta AM. Multiple-input, multiple-output system identification for characterization of limb stiffness dynamics. Biol Cybern. 1999 May;80(5):327-37.
Best wishes,
Ed Chadwick.
GH stiffness
Thanks for the advice and references Ed - I'll read up and see if this method will be of benefit for our study.
Kind regards.