Radiological Analysis of Sagittal and Cross-sectional Morphology of Congenital Lumbar Spinal Stenosis

Abstract Background Purpose This retrospective study was applied to investigate the morphology characteristics of the spine and pelvis in patients with congenital spinal stenosis, to explore the effect of morphological parameters in the pathogenesis and development of the disease.Methods The analysis is based on data of a case-control study, including 40 patients (19 females/21 males) with congenital lumbar spinal stenosis, 40 patients (17females/23males) with age-、Sex- and the waist and leg pain score-matched acquired lumbar spinal stenosis and 40 age-、Sex-matched normal volunteers(controls). Lumbar MRI, lumbar computerized tomography（CT）and full-length radiographs were used to obtain sagittal and cross-sectional parameters. Parameters including pelvic incidence（PI）, sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), sagittal vertical axis（SVA）, and thoracic kyphosis（TK）on the sagittal plane were measured on full-length radiographs and analyzed. The anteroposterior (AP) bone canal diameter and spinal canal area of L4 were collected and analyzed on Lumbar CT. Lumbar MRI was taken to evaluate the angle of the ligamentum flavum at the level of L4/5 intervertebral space，and the Lumbar disc degeneration degree was calculated.Results Total scores for lumbar disc degeneration and the angle of the ligamentum flavum were significantly lower in the congenital group than in the acquired group（P= 0.02 and P= 0.012，respectively ； P＜0.05）. The differences of LL, PT, SVA and TK values were statistically significant ， while the differences of SS and PI were not significant among the acquired, congenital, and control groups. TK values were significantly lower in the congenital group than in the acquired and control groups（P=0.024 and P=0.006，respectively； P＜0.05）. Patients in the congenital and acquired groups had significantly lower LL values than patients in the control group (p = 0.000 and 0.041, respectively； P＜0.05). The mean value of LL was 30.31°±13.42° in the congenital group, while 41.10°±12.51° in the acquired group. And the difference of LL between these two groups was statistically significant（p=0.000＜0.05）. The SVA values of the congenital group, acquired group, and control group increased respectively(all P＜0.05). The PT in the congenital group showed significantly lower values than the acquired group (p = 0.041＜0.05). There is no statistically significant difference in other parameters.The correlations between LL and PI are well in the congenital group（r=0.336；P=0.034）, acquired group（r=0.464；P=0.003） and control group（r=0.584；P=0.000）. However, the trend line of LL/PI in the acquired group was drawn below the control population. Also, the trend line of LL/PI in the congenital group was below the waist and leg pain score-matched acquired group with lower lumbar degeneration.Conclusion In addition to bony structural stenosis, the smaller angle of the ligamentum flavum may be an anatomical factor that causes the smaller effective area of the spinal canal in patients with congenital lumbar spinal stenosis. Patients with congenital lumbar spinal stenosis show a significant reduction in the physiological curvature of the thoracic and lumbar spine, and the trunk leans forward. In addition to intervertebral disc degeneration and pain factors, bony spinal stenosis is also a possible factor leading to smaller LL in patients with congenital lumbar spinal stenosis. LL less than 41° can be used as the initial screening standard for congenital lumbar spinal stenosis among patients with lumbar spinal stenosis.