Inclusion criteria:  Major subject (≥18 years old) Subject operated at the HUS between March and December 2019 Subject with a surgical indication for arthrodesis and decompression of the lumbar canal for degenerative spondylolisthesis L3-L4 or L4-L5 Subject not having expressed his opposition, after information, to the reuse of his data for the purposes of this research.  Exclusion criteria:  Subject having expressed opposition to participating in the study Subject under guardianship or guardianship Subject under safeguard of justice