Abstract:Objectives：To measure the lumbar 4-5 intervertebral disc height and intervertebral disc height index of normal population.Methods：478 patients examined by lumbar vertebra MRI and the results suggested the lumbar segment 4-5 was normal in our hospital from January 2013 to June 2014 were collected. According to the inclusion and exclusion criteria, a total of 269 patients were incorporated into the group. Among them, 137 were male and 132 were female. These patients were divided into three groups: young group (20-40 years old), middle-aged group (40-60 years old) and the elderly group (over 60 years old) to measure the L4-5 intervertebral disc height and intervertebral disc height index and statistical analysis. Change rules of normal L4-5 intervertebral disc height and intervertebral disc height index in different age groups were analyzed.Results：269 patients with normal L4-5 intervertebral disc height and intervertebral disc height index were measured. Among them, 100 patients were in the young group, 47 were male and 53 were female; 107 patients were in the middle-aged group, 57 were male and 50 were female; 62 patients were in the elderly group , 33 were male and 29 were female.The L4-5 intervertebral height of 62 elderly patients (male 33/ female 29) was 14.9±2.0mm (male 15.3±1.6 female 14.7±2.3), 15.4±2.0mm (male 15.9±1.4, female 14.6±1.9), 12.0±1.4mm (male 12.9±1.1, female 11.8±1.3), respectively.The L4-5 intervertebral height index was 0.33±0.04 (male 0.34±0.03, female 0.32±0.05), 0.34±0.03 (male 0.35±0.04, female 0.33±0.04), and 0.28±0.02 (male 0.29±0.03, female 0.27±0.03), respectively.Intervertebral height and intervertebral height index were significantly decreased in the elderly group compared with the young group and the middle age group (P<0.05).Conclusion：The normal range of L4-5 intervertebral height and intervertebral height index in normal adults of different ages were obtained.Intervertebral disc height and intervertebral disc height index of the population below 60-year-old increase with age, while they decrease significantly after 60 years old.