Sun Z, Xu C, Yin M, et al. - This research sought to correlate the reliability and reproducibility of Spinal Deformity Study Group (SDSG) and Clinical and Radiographic Degenerative Spondylolisthesis (CARDS) classifications, and to explore their clinical application value. Researchers recruited a total of 117 patients with L5/S1 lumbar degenerative spondylolisthesis (DS). They selected five experienced spine surgeons to evaluate DS with SDSG and CARDS systems. They used Kappa (K) value to assess the coefficient consistency for multi-factor and assess the inter- and intra-observer agreement. The analysis was repeated after 12 weeks. Compared with the CARDS system, SDSG system had better inter-observer reliability, and though the CARDS system is more intuitive and simpler, it is more likely to produce deviations when using it. According to the results, both SDSG and CARDS systems demonstrate substantial agreement and have great significance in the surgical strategy of L5/S1 lumbar DS; they can be widely applied in clinical practice.