Validity and reliability of skin markers for measurement of intersegmental mobility at L2–3 and L3–4 during lateral bending in healthy individuals: A fluoroscopy study

Determination of the Functional Relationship Between Lumbar Lordosis and Pelvic Tilt

“…Based on the subjects in this study this translates to a 0.4-0.7 degs uncertainty in LL angles in the sagittal plane. Angles derived from marker positions have accuracy of + 0.5 deg relative to spinous processes [33]. AMTI force plates are accurate to 25N at full scale output.…”

“…The vertebral endplates are not visible during motion capture analysis thus skin mounted retro-reflective markers are placed over bony landmarks, such as spinous processes or adjacent muscle bellies, to track spine motion. Studies using magnetic resonance imaging and radiographic techniques have shown skin mounted markers correlate strongly with radiographic position and angle measures [33,34]. In nine healthy young males, Mörl et al (2006) found skin motion related marker shift during flexion was not significantly different from zero for either markers placed over the muscle bellies or spinous processes; and further determined that skin motion was several times less for markers placed over the spinous processes than those placed over the muscle bellies (median = 0.38mm vs 0.86mm) [34].…”

“…In nine healthy young males, Mörl et al (2006) found skin motion related marker shift during flexion was not significantly different from zero for either markers placed over the muscle bellies or spinous processes; and further determined that skin motion was several times less for markers placed over the spinous processes than those placed over the muscle bellies (median = 0.38mm vs 0.86mm) [34]. A collection of techniques involving retro-reflective markers have been used to describe the spine including lumbar depth [35], arc fitting [35], plumbline [36], as well as a variety retro-reflective marker locations and configurations [33][34][35][37][38][39]. However, a standard has not yet been established.…”

“…Another limitation was the palpated location of skin markers were not consistently placed over the intended vertebrae; a limitation common in opto-electronic studies. It was assumed: that using the screw heads in the markers accurately reflected an opto-electronic camera system, and that the EOS system has an accuracy equal to or better than the accuracy of skin markers (+0.5 deg) [33].…”

“…During the EOS scans the subject's arm position was altered from a normal standing position, and their foot position was controlled. It was assumed: that the hyper-tensioned clavicle strap was tightened equally on both sides, and that the EOS system had an accuracy equal to or better than the accuracy of skin markers (+0.5 deg) [33] .…”