Estimating hip joint center from skin-mounted markers

[Janis Wojtusch]

Hello,

I have a dataset of a female subject with multiple skin-mounted markers and try to estimate the hip joint center with different methods given in literature. I get very different results and actually only one estimation is reasonable according to my opionion. It would be great, if you could give me some feedback or advice on that.

I attached three pictures and a Matlab figure (compressed in the zip file) that allows to navigate in the three-dimensional view. The red dots are the measured markers, the green dots give the estimated position projected onto the skin. The blue symbols represent different estimations of the hip joint center. I have the following markers in the pelvis area:

• Posterior-superior illac spine (left and right)
• Anterior-superior illac spine (left and right)
• Greater trochanter
• Pubic symphysis

I used the following methods to estimate the hip joint center:

• Blue circle symbol - method given in Reed, M. P., Manary, M. A., & Schneider, L. W. (1999). Methods for Measuring and Representing Automobile Occupant Posture.
• Blue cross symbol - method given Davis, R. B., Õunpuu, S., Tyburski, D., & Gage, J. R. (1991). A gait analysis data collection and reduction technique.
• Blue star symbol - method given in Bell, A. L., Pedersen, D. R., & Brand, R. A. (1990). A Comparison of the Accuracy of Several Hip Center Location Prediction Methods.

My Matlab implementation is attached in the text file. The last two methods are also described on the C-Motion wiki:

• http://www.c-motion.com/v3dwiki/inde...avis%29_Pelvis
• http://www.c-motion.com/v3dwiki/inde...le=Coda_Pelvis

The estimations obtained from the methods described by Reed1999 (circle symbol) and Davis1991 (cross symbol) are very close, but compared to the greater trochanter markers too low. Only the estimation given by the method of Bell1990 (star symbol) seems to be in a reasonable position. So I would go with the Bell1990 estimation, but I am quite surprised that the two other methods differ that much with being that close to each other.

[Morgan Sangeux]

Re: Estimating hip joint center from skin-mounted markers

Hi Janis,
I have done a bit of work on this. We evaluated the accuracy of various hip joint centre estimates on normal adults (1) (2) and children with cerebral palsy (i.e. with motor control disability) (3). Similar studies were conducted by Leardini et al. (4) and Hicks et al. (5) on top of Bell study you already mentioned.
All of the above compared the various estimates of the hip joint centres against a medical image based reference. In most cases the objective was to decide whether to use anthropometrics based (the ones you seem to be interested in) or functional methods. From my experience, you can hope to be within 1.5cm of the true hip joint centre If you use the anthropometric equations from (6) or the geometrical sphere fitting functional method (valid only for able bodied subjects). The anthropometric methods necessitate that you are both skilful and careful at locating the pelvic markers.

1. Sangeux M, Pillet H, Skalli W. Which method of hip joint centre localisation should be used in gait analysis? Gait Posture. 2014 May;40(1):20-5.
2. Sangeux M, Peters A, Baker R. Hip joint centre localization: Evaluation on normal subjects in the context of gait analysis. Gait & Posture. 2011;34(3):324-8.
3. Peters A, Baker R, Morris ME, Sangeux M. A comparison of hip joint centre localisation techniques with 3-DUS for clinical gait analysis in children with cerebral palsy. Gait & Posture. 2012;36(2):282-6.
4. Leardini A, Cappozzo A, Catani F, Toksvig-Larsen S, Petitto A, Sforza V, et al. Validation of a functional method for the estimation of hip joint center location. Journal of Biomechanics. 1999;32:99-103.
5. Hicks JL, Richards JG. Clinical applicability of using sphere fitting to find a hip joint centers. Gait & Posture. 2005;22:138-45.
6. Harrington ME, Zavatsky AB, Lawson SEM, Yuan Z, Theologis TN. Prediction of the hip joint centre in adults, children, and patients with cerebral palsy based on magnetic resonance imaging. Journal of Biomechanics. 2007;40(3):595-602.

[Janis Wojtusch]

Re: Estimating hip joint center from skin-mounted markers

Hello Morgan,

thank you very much for your reply and the references. I will definitely try the methods you mentioned.

Janis