Invariance of head-pelvis alignment and compensatory mechanisms for asymptomatic adults older than 49 years

The aim was to quantify the postural alignment of asymptomatic elderly, in comparison to a reference population, searching for possible invariants and compensatory mechanisms. 41 volunteers (49-76 years old) underwent bi-planar X-rays with 3D reconstructions of the spine and pelvis. Alignment parameters were compared with those of a reference group of asymptomatic subjects younger than 40 years old, with a particular focus on center of acoustic meati (CAM) and odontoid (OD) with regard to hip axis (HA). Possible markers of compensation were also investigated. No significant difference among groups appeared for CAM-HA and OD-HA parameters. Twenty four percent of elders had an abnormally high SVA value and twenty seven percent had an abnormal global spine inclination. Increased pelvic tilt and cervical lordosis allowed maintaining the head above the pelvis. CAM-HA and OD-HA appeared quasi-invariant even in asymptomatic elderly. Some subjects exhibited alteration of spine alignment, compensated at the pelvis and cervical regions.