【Introduction】Wall-Occiput distance (WOD) and rib-pelvis distance (RPD) in female patients treated for osteoporosis are estimates of the presence of thoracic and lumbar vertebral　fractures. However, it is unclear whether it is useful for global spinal alignment evaluation. The purpose of this study was to assess the relationship between WOD or RPD and sagittal spinal alignment in the general population, and to assess whether WOD or RPD was useful for estimating the sagittal spinal alignment.

【Methods】The subjects were 910 local residents (344 men, 566 women, average age 68 years, most age group 70s) who agreed with the purpose of this survey and submitted a written consent to participate. Thoracic kyphosis angle (T1-T12, TK), lumbar lordosis angle (L1-S1, LL), and sagittal vertebral axis (SVA) were measured on a standing whole-spine lateral radiograph. SVA was classified into 3 groups: less than 40 mm, 40-95 mm, and more than 95 mm. In addition, WOD was measured while the patient stands straight with his/her back against the wall and heels touching the wall. While the head face forward so that an imaginary line connecting the lateral corner of the eye to the superior junction of the auricle of the ear was parallel to the floor, the distance between the occipital prominence and the wall was quantified. In this study, the inability to touch the wall with the back of the head was judged as WOD positive. RPD was measured while the subject stand straight with arms outstretched at 90 degrees. The examiner stand behind the subject and inserted his or her fingers into the space between the inferior margin of the ribs and the superior surface of the pelvis in the midaxillary line. The rib-pelvis distance was the closest whole number of fingerbreadths between these structures. Two and less than two fingerbreadths were judged as RPD positive.

【Results】1. There was a statistically significant difference between WOD positive / negative and TK or LL. However, the difference between the average values ​​was about 3-4 degrees in each case. On the other hand, in SVA, WOD positive was 41 mm on average and 25 mm negative, and the frequency of WOD positive was 16.5% for less than 40 mm, 23.1% for 40-95 mm, and 60.5% for the group over 95 mm.

2. There was a statistically significant difference between RPD positive / negative and TK or LL. However, the difference in the average values ​​was about 2-3 degrees in each case. On the other hand, in SVA, RPD positive was 39 mm on average and 24 mm negative, and the frequency of RPD positive was 42.8% for less than 40 mm, 55.6% for 40-95 mm, and 67.5% for the group over 95 mm.

3. The sensitivity and specificity of WOD and RPD when detecting SVA 40 mm or more were 72.0% and 83.4% for WOD and both of 57.2% for RPD.

【Conclusion】WOD was convenient for detecting SVA 40 mm or more by a simple method, and its sensitivity was 72.0% and its specificity was 83.4%.