Effect of reclining angle on lumbar lordosis at driving posture: A radiological evaluation.

Abstract

Optimal seatback angles for automobile drivers' seats have been investigated based on comfort and back muscle activities; however, radiology supported evidences are scarce. The aim of this study was to evaluate optimal range of the seatback reclining regarding torso angles for an automobile driver's seat to preserve lumbar lordosis. Thirty-one healthy volunteers were recruited among five body type categories. Lateral lumbar spine X-rays were obtained for the neutral sitting posture without seatback (reference), and with reclining angles of 23∘ to 33∘ by 2∘ intervals. The Cobb angles for the L1-L4, L4-S1, and L1-S1 segments were measured. The Cobb angle for L4-S1 was nearest to the reference (18.74 ± 1.57∘, mean ± standard error mean) at reclining angles of 29∘ and 31∘ (14.51 ± 1.41∘ and 14.47 ± 1.43∘, respectively). The Cobb angle at L4-S1 between reclining angles of 27∘(12.02 ± 1.31∘) and 29∘ (14.51 ± 1.41∘) were significantly different (p< 0.001). Tall men showed relatively preserved lordosis angles at all reclining angles. Fat men and short women demonstrated prominent loss of lordosis with excessively kyphotic L1-L4 segment. Reclining angles of 29∘ to 31∘ revealed to be optimal for preserving lordosis at the L4-S1 segment. Individualized healthcare-related guideline for driver's seat adjustment setting is necessary.