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Study demonstrates pelvic incidence is not a fixed value, can change with varied pelvic positions
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BOSTON — A presenter at the North American Spine Society Annual Meeting said a high percentage of heathy participants changed in their pelvic incidence when they changed their pelvic position.
“[Almost] 80% of our healthy normal patients changed their pelvic incidence with just a simple thing, such as rotating their pelvis anteriorly or posteriorly,” Howard M. Place, MD, said during his presentation. “I think, as a group, we need stop thinking about pelvic incidence as a fixed value. It is something that can be changed at one period, at one time.”
Place and colleagues performed a one-sample observational study and identified 50 healthy adults. Radiographs were taken for all participants in the following positions: a resting position; with anterior pelvic rotation; and with posterior pelvic rotation. Chronbach’s alpha was used to assess interobserver reliability. Investigators assessed pelvic incidence changes by evaluating the changes between pelvic incidence values and change in pelvic position. Pelvic tilt, sacral slope and pelvic incidence were independently measured.
Results showed the internal consistency was 0.971. Place said 88% of participants who went from baseline to maximum anterior pelvic rotation had a mean change of almost 3° and more than 20% had a change of more than 5°.
“We looked at the direction. There was no consistent direction for which [patients] changed. Some changed with an increase in pelvic incidence and some changed with a decrease in pelvic incidence, but they changed,” he said.
Place said when they observed the baseline to posterior pelvic rotation they found 80% of participants had a change in pelvic incidence, with half of those having greater than 3° of change and a quarter of those with a change of more than 5°. He noted 40% of participants showed no consistency in the direction for which they changed.
“Our data suggests that a normal person can change their pelvic vertebrae, not just in its relationship in space, but also in shape,” He said. “Pelvic incidence in our group changed 80% of the time when patients changed their pelvis, both anteriorly and posteriorly.” – by Monica Jaramillo
Reference:
Place HM, et al. Paper #119. Presented at: North American Spine Society Annual Meeting; Oct. 26-29, 2016; Boston.
Disclosure: Place reports no relevant financial disclosures.