| Background:The degenerative lumbar spinal stenosis(DLSS)is the most common reason for low back pain and lower limb discomfort.DLSS develops when intervertebral disc degeneration,ligamentum flavum thickening and facet joint hypertrophy appears.Much evidence suggests that intervertebral disc degeneration occurs ahead of other spinal elements.And the loss of intervertebral height might be the key to DLSS.The disc bulge,facet joint degeneration,ligamentum flavum hypertrophy and paravertebral muscles atrophy due to denervation happen as consequences.Degeneration of facet joints may present as hyperplasia and sclerosis that restrict mobility of spine,but some patients have an enlarged joint space with fluid accumulation,leading to decreased stability of spine;however,either of them results in abnormal stress.Paravertebral muscle atrophy also leads to decreased stability of spine,which in turn acts on the intervertebral disc and accelerates its degeneration.Cartilaginous endplate injury hinders the exchange of nutrients and metabolites of the intervertebral disc and body,which aggravates the degenerative process of the disc.Therefore,it should be taken into consideration that changes of the intervertebral disc and its height in the development of DLSS,as well as the correlation with other spinal radiographic parameters.However,patients with DLSS usually lack of pre-morbid radiographic data,so whether the pre-morbid disc height of DLSS patients differs from that of healthy subjects remains unclear.And few articles reported the correlation between intervertebral disc height and other radiographic parameters in patients with DLSS.Objective:To investigate the radiographic risk factors for DLSS and analyze correlations among various radiographic parameters based on lumbar spine MRI data from patients with DLSS and healthy population.Method:Patients treated surgically for L4-5 central DLSS from September 2017 to December 2022 and healthy subjects undergoing routine health checks at the same period were enrolled.A total of 171 participants were included.89 cases were included in the stenosis group,29 men and 60 women,59.72±10.38 years(range:39 to 80 years).There were 82 cases in the healthy group,23 males and 59 females,57.24±8.94 years(range:40 to 74 years).MRI of the lumbar spine was performed in both groups,and lumbar dynamic position X-ray was also performed in the stenosis group.The intervertebral disc height of L1-S1 in both groups was measured by the modified distortion-compensated roentgen analysis(DCRA),and the ratio of L4-5 to L3-4 intervertebral disc height(IDHL4-5/L3-4),the initial height of L4-5 in the stenosis group(iIDHL4-5)were also calculated.Evaluate and measure disc degeneration,cartilaginous endplate injury,Modic changes,ligamentum flavum thickness,and range of intervertebral mobility(ROM).The dural sac area,facet joint opening(FJO),facet joint angle(FJA),and standard cross-sectional area of multifidus,erector spinae,and psoas major muscles(SCSA)at L4-5 median disc level.The disc degeneration was assessed using the Pfirrmann grading system,and cartilaginous endplate injury was evaluated using Rajasekaran grading criteria.The initial intervertebral disc height was calculated according to the disc height of L3-4 in the stenosis group and the IDHL4-5/L3-4 in the healthy group.The ROM was the difference in intervertebral angle between over-extension and over-flexion films on dynamic X-ray.The standard cross-sectional area of the paravertebral muscles was the ratio between the muscle area and L4-5 intervertebral disc area.The t-test and chi-square test was used to check the difference in radiographic parameters between two groups.The receiver operating characteristic curve(ROC)and Youden index were used to determine cut-off values of initial intervertebral disc height,facet joint opening and angle.Correlation analysis was performed using Pearson analysis and Spearman rank correlation analysis.Results:The Kappa coefficient for interobserver agreement on intervertebral disc degeneration,cartilaginous endplate injury,and Modic changes was substantial(k=0.798,k=0.711,k=0.892),and good interobserver reproducibility for other continuous variables of radiographic parameters(ICC:0.712～0.824)was observed.The intervertebral disc height in the stenosis group was higher than that in the healthy group except for L4-5(P<0.05).The IDHL4-5/L3-4 in the stenosis and healthy groups were 1.08±0.19 and 1.12±0.24,respectively,which were not statistically significant.However,the iIDHL4-5 in the stenosis group was significantly higher(P=0.002).Compared with the healthy group,the ligamentum flavum was thicker at all lumbar segments(P<0.001).The facet joint angle and opening in the stenosis group and the healthy group were 53.70±10.46° and 4.11±0.85 mm,43.57±8.27° and 3.53±0.45 mm,respectively.And differences between the two groups were statistically significant(P<0.001).Compared with the healthy group,the SCSAs of the paravertebral muscles were significantly smaller in the stenosis group(P<0.002).At L4-5,disc degeneration was more severe in the stenosis group than in the healthy group(P<0.001)with no statistically significant difference in the other segments(P>0.05),while all lumbar segments showed more severe cartilaginous endplate injury in the stenosis group(P<0.001).The ROC curve and Youden index showed the cutoff value of L4-5 initial intervertebral disc height was 10.26 mm,facet joint opening’s cut-off value was 3.75 mm,facet joint angle was 45.40°.Intervertebral disc height negatively correlated with disc degeneration at L2-S1 and positively correlated with the range of intervertebral mobility at L1-S1.The intervertebral disc height correlated with cartilaginous endplate injury at L5-S1(r=-0.54,P<0.001),with Modic changes at L2-3(r=-0.43,P<0.001)and L5-S1(r=-0.50,P<0.001),and with ligamentum flavum thickness at L3-4(r=-0.39,P<0.001),and no statistical correlation was observed at other segments.At L4-5,intervertebral disc height was positively correlated with SCSA of the multifidus(r=0.31,P=0.003)and psoas major(r=0.46,P<0.001).A positive correlation was observed between the disc degeneration and the SCSA of the multifidus(r=-0.41,P<0.001)and psoas major(r=-0.47,P<0.001).A positive linear relationship between the cartilaginous endplate injury and disc degeneration was observed at L1-2(r=0.41,P<0.001),L2-3(r=0.44,P=0.002),and L5-S1(r=0.40,P<0.001),and no statistical correlation was observed at L3-4 and L4-5.Conclusion:All initial lumbar intervertebral disc height of DLSS patients were higher than that of the healthy population.Patients were at increased risk for developing degenerative lumbar stenosis with higher initial disc height(≥10.26 mm),greater facet joint opening(facet joint space≥3.75 mm),or more sagittal alignment(facet joint angle≥45.40°).Larger disc height contributes to DLSS by increasing intervertebral mobility and promoting disc degeneration;paravertebral muscle atrophy,greater facet joint angle and opening contribute to DLSS by decreasing spinal stability.Patients with DLSS have more severe lumbar cartilaginous endplate injury and thicker ligamentum flavum,which may be the reason for the population to develop DLSS. |
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