Age-related changes in standing ability on a foam surface based on the center-of-mass acceleration of each body segment.

[Purpose] The purpose of this study was to elucidate the age-related changes in the stability of the quiet standing posture based on the acceleration of the center of mass of each body segment under deteriorated somatosensory conditions. [Participants and Methods] The participants in this study were 18 healthy elderly persons and 11 healthy young adults. A foam surface was placed on the force plate for load-bearing onto the somatosensory system. The participants maintained a quiet position on the force plate under two conditions: a firm surface and a foam surface. The accelerations of the head, thorax, pelvis, and whole body center of mass when quiet standing in two conditions were measured by a motion capture system. In the statistical analysis, regarding the center of mass of each body segment, the interactions were examined by performing a two-way analysis of variance using age and surface condition as factors. [Results] A two-way analysis of variance detected an interaction between age and surface factors for anteroposterior acceleration at the center of mass of the head. For other body segments, interactions between the two factors were not detected. [Conclusion] The results of anteroposterior acceleration at the center of mass of the head suggest that under conditions of deteriorated somatosensory function in the lower limbs, minute anteroposterior position adjustment of the head is an essential characteristic of the standing posture control mechanism in the elderly.

Postoperative Recovery of Gait Function at Early Phase Is Delayed in Patients with Spinal Tumors with Impairment of the Joint Position Sense in the Big Toe: A Retrospective Cohort Study.

Introduction: We investigated the effect of preoperative joint position sense in the big toe on the postoperative recovery of gait function after spinal tumor surgery. Methods: Seventy-three patients with spinal tumors who underwent surgery at our hospital between 2014 and 2019 and could be followed for at least 6 months after surgery were included. The patients were divided into the cervical spinal (41 cases) and thoracic spinal (32 cases) groups according to the localization of the tumor. These groups were further classified into an Impaired group (cervical spinal, 34 cases; thoracic spinal, 19 cases) and an Intact group (cervical spinal, 7 cases; thoracic spinal, 13 cases) according to the presence or absence of preoperative joint position sense in the big toe. The amount of change in ambulatory function from the preoperative period to 3 and 6 months postoperatively was compared between the Impaired and Intact groups within each tumor localization category. Results: Impaired preoperative joint position sense in the big toe in patients undergoing thoracic spinal tumor surgery delayed the recovery of gait function in the early postoperative period. Conclusions: In patients with thoracic spinal tumor surgery, the absence of preoperative joint position sense in the big toe delayed the recovery of postoperative gait function.