Reliability of photogrammetry for evaluating pelvic posture in healthy individuals

Miaomiao DONG; Xiang LI; Jiani XIE; Lixin ZHANG; Yuexi WANG

ABSTRACT

BACKGROUND:

In clinical practice,the anterior superior iliac spine and posterior superior iliac spine are usually located by palpation,and the tilt of the pelvis is determined by visual observation method or photogrammetry.Among them,the visual observation method can only have qualitative conclusions,and its reliability is poor.The photogrammetry is not only more convenient and fast,but also can give more accurate quantitative data,which is one of the best clinical evaluation methods.However,there are no studies on the reliability of pelvic posture assessment using photogrammetry in China.

OBJECTIVE:

To evaluate the pelvic posture by visual observation method and photogrammetry,and to compare the reliability level of the two methods to guide clinical application.

METHODS:

Forty-five healthy subjects were selected and red marks were made at the bilateral anterior superior iliac spine and posterior superior iliac spine.Pelvic posture was photographed from the front,back(coronal plane),left,and right(sagittal plane).The left and right pelvic tilt angles(α,β angles)were selected from the front and back views,which represented the angle between the bilateral anterior superior iliac spine line or the bilateral posterior superior iliac spine line and the horizontal line.The anterior and posterior pelvic tilt angles(γ,θ angles)were selected from the side view,which represented the angle between the ipsilateral anterior superior iliac spine and posterior superior iliac spine line and the horizontal plane,indicating the sagittal plane pelvic tilt.Evaluation methods included visual observation method and photogrammetry.Two evaluators independently evaluated the pelvic α,β,γ,θ angles using the visual observation method first,and then recorded the pelvic α,β,γ,θ angles using the photogrammetry.After a one-month interval,the visual observation method and photogrammetry were performed again,and the pelvic α,β,γ,θ angles were recorded.The intraclass correlation coefficients were used to analyze the data obtained from the two evaluation methods and the before-and-after measurements0.90-0.99 as an excellent correlation,0.80-0.89 as a good correlation,0.70-0.79 as a moderate correlation,and≤0.69 as a poor correlation.The standard error of measurement and the minimal detectable change with 95%confidence intervals were calculated to evaluate the inter-rater and intra-rater reliability. RESULTS AND

CONCLUSION:

(1)The interrater intraclass correlation coefficients of the visual observation method and photogrammetry were as followsanterior view0.682 and 0.718,posterior view0.513 and 0.867,left view0.739 and 0.960,and right view0.756 and 0.971.The visual observation method showed poor correlation between the anterior and posterior views and moderate correlation between the left and right views,while the photogrammetry showed moderate correlation for the anterior view,good correlation for the posterior view,and excellent correlation for the left and right views.The standard error values of measurement were as followsanterior view3.266 and 1.625,posterior view4.278 and 1.763,left view5.935 and 1.787,and right view5.723 and 1.698.The minimal detectable change values with 95%confidence intervals were as followsanterior view9.053 and 4.504,posterior view11.858 and 4.887,left view16.451 and 4.953,and right view15.863 and 4.707.(2)The interrater intraclass correlation coefficients of the visual observation method and photogrammetry were as followsanterior view0.452 and 0.723,posterior view0.483 and 0.904,left view0.518 and 0.955,and right view0.657 and 0.968.The visual observation method showed poor correlation in all four directions,while the photogrammetry showed moderate correlation for the anterior view and excellent correlation for the other three directions.The standard error values of measurement were as followsanterior view5.651 and 1.610,posterior view4.237 and 1.523,left view7.322 and 1.891,and right view6.509 and 1.781.The minimal detectable change values with 95%confidence intervals were as followsanterior view15.664 and 4.463,posterior view11.744 and 4.222,left view20.296 and 5.242,and right view18.042 and 4.937.(3)These results confirm that the sagittal and coronal plane photogrammetries have good intrarater and interrater reliability for evaluating pelvic posture,especially with the use of the photogrammetry,which has good data stability.This method is simple,fast,efficient,accurate,low-cost,and does not cause X-ray damage,and can qualitatively and quantitatively reflect the actual situation of the patient's pelvis,making it suitable for clinical use.