This is a prospective single-center study. Patients requiring posterior lumbar interbody fusion (PLIF) for degenerative disease are prospectively enrolled and followed. Patients enrolled in this study have asymptomatic pre-existing spinal canal stenosis at adjacent segment. This study will focus on the effects of preventative limited decompression at adjacent segment.

Adjacent segment pathologies (ASP), including radiological adjacent segment degeneration (ASDeg) and adjacent segment disease (ASDis) after lumbar fusion surgeries have been troubling complications. The development of ASDis greatly reduces postoperative quality of life, and revision surgery may be required in severe cases. Several risk factors for ASP have been reported, such as age, sex, pre-existing adjacent degeneration, multilevel fusions, sagittal imbalance, the type of fusion, facet tropism and laminar inclination. Previous studies have reported asymptomatic pre-existing spinal canal stenosis (SCS) as a risk factor for ASDis that requires additional surgery. Appropriate strategy needs to be explored for the treatment of asymptomatic pre-existing spinal canal stenosis.

Limited decompressions, including partial laminotomy and flavectomy, have been proved to have the role of enlargement in spinal canal. Therefore, we hypothesize that limited decompressions at adjacent segment with asymptomatic pre-existing SCS will have the preventive effect on ASP.

This prospective study will be limited to patients with the same preoperative pathology, the same fusion segments (L4-5 and L5-S1), the same fusion technique (PLIF). Dynamic X-ray and MRI examinations of lumbar will be completed to evaluate the imaging manifestations of the responsible and adjacent segments before surgery. Patients with asymptomatic pre-existing canal stenosis factors (cerebrospinal fluid occlusion grade 1) at L3/4 segment will be enrolled. Patients will be randomly divided into two groups according to different strategies. NS Group includes patients who simply receive responsible segments fused (L4-S1). LD Group includes patients who receive responsible segments fused (L4-S1) plus limited decompression at adjacent segment (L3/4). In terms of limited decompression at the adjacent segment, partial laminotomy, flavectomy, and bilateral medial facetectomies up to the pedicle will be performed. Complete laminectomy and destroy of posterior ligament complex will be avoided.

The patient's age, gender, preoperative body mass index (BMI), American Society of Anesthesiologists classification of anesthesia (ASA grade) will be recorded during the hospital stay. Surgical data including operation time, blood loss, perioperative complications (including cerebrospinal fluid leakage, wound infection, postoperative neurological dysfunction, and perioperative secondary surgery, cardiopulmonary complication, cerebral infarction/hemorrhage, etc.), and length of hospital stay are also recorded. Preoperative clinical function questionnaires, including visual analog scale (VAS) of low back, VAS of the legs, and Oswestry Disability Index (ODI) scores for patients were completed on admission for surgery without any assistance. All the patients enrolled will finished the follow-up from date of surgery at 1,2, 5 and 10 years. The clinical outcomes and ASP will be recorded.

Inclusion Criteria:

• A clear diagnosis of lumbar spinal stenosis, and surgical level of L4-S1 (The levels to be operated on were decided by matching the clinical symptomatology with the radiological findings of the spinal levels that needed decompression);
• Patients have asymptomatic pre-existing spinal canal stenosis (cerebrospinal fluid occlusion grade=1) at adjacent segment.
• Failed at least eight weeks conservative treatment;

Exclusion Criteria:

• Unstable factors (slip, rotation, lateral bending, etc.) in adjacent segment L3/4;
• Preoperative sagittal and coronal imbalance of the spine;
• Lumbar infection and/or tumor diseases;
• A previous history of lumbar fusion surgery.

We will make the clinical study report available for half a year after the publication of the results of the study.

The IPD will become available for half a year after the publication of the results of the study.

The IPD is available to the readers of the journal in which our research is published. The corresponding author of the published papers will review the requests.