关键词:  , 腰椎, 椎间盘退行性变, 磁共振成像, 责任间隙

Abstract: Background　Disc degeneration is the initiating factor for a series of lumbar degenerative diseases.Previous reports mostly have focused on the epidemiologic and imaging characteristics of lumbar disc degeneration.However，the studies investigating lumbar degenerative diseases with refractory lumbocrural pain that necessitate surgical procedures are sparse.The distribution of the degenerative disc is unknown，along with the index segment（operated segment）.Objective　To study the imaging distribution of disc degeneration and characteristics of the index levels in patients with lumbar degenerative diseases undergoing operation.Methods　503 cases of lumbar degenerative diseases who underwent anteroposterior and lateral radiographs，dynamic radiographs，and sagittal MRI in PLA 960 hospital from January 2012 to February 2016 were enrolled.The distribution of lumbar disc degeneration and index segments was analyzed〔including lumbar instability，Modic changes，high intensity zone（HIZ），and Schmorl's nodes（SN）〕.Disc degeneration was evaluated with the Pfirrmann's staging system，with Ⅰ and Ⅱ designating the normal discs，while Ⅲ-Ⅴ indicating degenerative changes（Ⅳ and Ⅴ implying serious degeneration）.Multi-segment（≥2） disc degenerations used a custom W classification.Results　There were 2 515 degenerative discs in 503 patients，demonstrating a degeneration rate of 74.08% （1 863/2 515），and serious degeneration rate was 36.46%（917/2 515）.The degeneration rate of upper lumbar segments was 56.96%（573/1 006，L1-2 and L2-3），with serious disc degeneration accounting for 34.55%（198/573）.In the lower lumbar segments（L3-4，L4-5，L5-S1），the degeneration rate was 85.49%（1 290/1 509），with the serious disc degeneration rate being 55.74%（719/1 290）.Lower lumbar segments were associated with higher disc degeneration rate and serious degeneration rate（P<0.05）.Female patients of ≥40 years had higher disc degeneration rate（P<0.05）.Female cases ≥40 years showed more instability（P<0.05），but demonstrated no significantly different Modic change，HIZ and SN incidence compared with male cases（P>0.05）.Male patients of <40 years had slightly higher instability than female patients of the same age group（P>0.05），but demonstrated significantly different Modic change，HIZ and SN incidence（P<0.05）.The differences in the incidence of Modic changes and HIZ in males <40 years and ≥40 years were significant（P<0.05）.The differences in the incidence of lumbar spine instability，HIZ and SN in females <40 years and ≥40 years were significant（P<0.05）.There was significant difference in distribution of lumbar instability，Modic changes，SN and HIZ in different degenerated segments（P<0.01）.There were 381 cases of single-segment undergoing operation，102 cases of two-gap，14 cases of three-gap，4 of four-gap，and 2 of five-gap.The degeneration rate of the intervertebral disc in the index level was 99.01%（498/503），and the rate of severe degeneration was 62.82%（316/503）.Conclusion　Lumbar degenerative diseases necessitating surgical interventions had a higher disc degeneration rate，with a female predominance.The degeneration rate increased in lower segments.Female patients were prone to have lumbar instability and Modic changes，whereas showing less serious disc degeneration.The age of 40 years is the watershed for the occurrence of Modic changes and HIZ in male cases，similarly in female patients for lumbar instability，HIZ，and SN.There were disc degeneration in most index segments，representing higher serious degeneration rates.

Key words: Lumbar Vertebrae, Intervertebral Disc Degeneration, Magnetic Resonance Imaging, Index Level