The investigators will retrospectively study lumbar spinal stenosis patients who underwent OLIF or MIS-TLIF with percutaneous pedicle screw fixation between January 2016 and December 2019.The investigators will measure estimated blood loss, operative time, hospital stay, cost, reoperation, and complication incidence, visual analogue scale (VAS), Oswestry Disability Index (ODI), Japanese Orthopaedic Association (JOA), and Short Form-36 (SF-36) scores, discal and foraminal height, lumbar lordotic angle, and fusion status.The investigators will conduct to evaluate postoperative improvements, complications, and reoperation rates between patients with lumbar spinal stenosis (LSS) undergoing oblique lateral interbody fusion (OLIF) or minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

Inclusion Criteria:

• LSS due to neurogenic claudication; Central stenosis or lateral stenosis who need surgery; Single-level, low-grade (Meyerding grade 1 or 2) isthmic spondylolisthesis or degenerative spondylolisthesis; and imaging findings consistent with the symptoms of LSS.

Exclusion Criteria:

• trauma, active infection, malignant tumors, spinal deformity, previous lumbar fusion, multi-segment fusion, multi-level, high-grade (Meyerding grade 3 or 4) isthmic spondylolisthesis or degenerative spondylolisthesis.

Patients who were diagnosed with LSS and underwent either MIS-TLIF or OLIF surgery between January 2016 and December 2019.