Abstract
Study Design A population-based study with longitudinal follow-up.
Objective To develop a quantitative index for lumbar disc space narrowing (DSN) evaluation in elderly subjects; to quantify the areal loss of thoracic and lumbar disc space over four years in elderly; and to study whether osteoporosis is associated with faster disc degeneration than normal bone mineral density (BMD) subjects.
Summary of Background Data There is paucity of research center on quantitative classification of lumbar DSN based on disc areal morphometry.
Methods With the database of MrOS/MsOS (Hong Kong) and those who attended the year-4 follow-up (n = 1519 for men and n = 1546 for women), data of 491 women and 592 men were randomly selected. For each spine, the anterior, middle, and posterior heights, anteroposterior diameter and structure area of discs (T4T5 to L4L5) were measured on lateral radiographs. Disc Area Index for Lumbar Spine (DAIL, disc area divided by the mean of the sum of square of the adjacent upper and lower vertebrae anterior-posterior diameter) was developed and compared with semi-quantitative DSN grading.
Results DAIL correlated with semi-quantitative grading, with sensitivity and specificity varying from 87.3% to 96.8% for grade-1 DSN, and 92.9 % to 100% for grade-3 DSN. The thoraco/lumbar disc area loss among men and women during 4 years’ follow-up period varied between 6.31% and 8.64%, and it was greater for women (mean: 7.18%) than for men (mean: 6.20%, p<0.001). Majority of lumbar disc space narrowing progressions during 72 to 76 years old were from normal to grade 1. Osteoporosis was associated with disc area decrease, both for thoracic and lumbar discs.
Conclusion Lumbar DSN can be quantified using DAIL. In elderly Chinese disc area lost faster in females than in males.