Relationship of the Lumbar Lordosis Angle to the Level of Termination of the Conus Medullaris and Thecal Sac

The level of termination of the conus medullaris (CM) and thecal sac (TS) is subject to variations. We try to correlate in this study these variations with the lumbar lordosis angle (LLA) using MRI scans. A retrospective study was conducted using available MRI scans of the lumbar spine. The CM level of termination (CMLT) and the TS level of termination (TSLT) were identified according to a vertebral level after dividing it into 3 parts. The LLA was also identified for each individual. Linear regression models were fitted to the data available on 141 individuals. Of these 70 were males and 71 were females. The most common site of CMLT was at the upper third of L1 (32.6%) and that of the TSLT was at the middle third of S2 (29.8%). The mean LLA was 46° (20°–81°). The most proximal CMLT was at the upper third of T12, whereas the most distal one was at the upper third of L2. The most proximal TSLT was at the upper third of S1, whereas the most distal one was at S3-S4 disc space. The CMLT showed a positive correlation with the LLA. In conclusion the CMLT and TSLT may be related to variations of the LLA.