At present, interbody fusion is the mainstream treatment for patients with lumbar spinal stenosis (LSS) and lumbar instability. However, the choice of interbody fusion for LSS patients with lumbar instability remains controversial. Recently, we developed crenel lateral interbody fusion combined with lateral plate fixation(CLIF - LP) for patients with LSS and lumbar instability. This surgical method has many advantages and showed good results for patients with LSS and lumbar instability. Therefore, we propose the following hypothesis: The clinical and imaging efficacy of CLIF-LP in the treatment of LSS patients with lumbar instability is not inferior to that of traditional transforaminal lumber interbody fusion (TLIF).

At present, interbody fusion is the mainstream treatment for patients with lumbar spinal stenosis (LSS) and lumbar instability. However, the choice of interbody fusion for LSS patients with lumbar instability remains controversial. Recently, we developed crenel lateral interbody fusion combined with lateral plate fixation(CLIF - LP) for patients with LSS and lumbar instability. This surgical method has the advantages of direct view operation, "safe" psoas major approach, application of modified retractor, and lateral plate reinforcement, which not only significantly improves the postoperative lumbar function and nerve function of patients with LSS and lumbar instability, but also significantly reduces related complications, accelerates rehabilitation, and reduces the medical cost of patients.

Therefore, we propose the following hypothesis: The clinical and imaging efficacy of CLIF-LP in the treatment of LSS patients with lumbar instability is not inferior to that of traditional transforaminal lumber interbody fusion (TLIF).

Inclusion Criteria:

1. Age 50-80 years old
2. Patients diagnosed with clinical symptoms of lumbar spinal stenosis, neurogenic intermittent claudication, the patient's walking ability is highly limited, and the quality of life is severely reduced
3. Imaging diagnosis of 1-2 LSS patients, consistent with clinical symptoms
4. Lumbar spine instability can be considered if one of the following three criteria is met: ① mechanical back pain with severe (VAS > 7) (pain aggravates with weight bearing). Radiographs of lumbar hyperextension and flexion show a slip of at least 3mm between the two vertebrae, or a rotation Angle of 11°. ③ Degenerative slip
5. Formal conservative treatment is ineffective for more than 3 months
6. No history of lumbar surgery
7. American College of Physicians ASA Grade I or II
8. Subjects voluntarily sign informed consent as subjects

Exclusion Criteria:

1. In patients with significant symptoms of lumbar radiculopathy, the pain from postural changes cannot be relieved
2. Bone stenosis, including developmental lumbar spinal stenosis
3. Free nucleus pulposus tissue into the spinal canal or cause spinal canal compression of the small joint cyst
4. Patients with hypertrophy of the yellow ligament or small joint cyst as the main pressure
5. Intervertebral space or posterior facet joints have fused
6. Infectious, traumatic and neoplastic diseases of the lumbar spine
7. Patients who are unable to undergo MRI
8. Some medical conditions, such as metabolic bone disease, autoimmune disease, poliomyelitis sequelae, osteoporosis, history of poor bone healing, and long-term oral steroids, were determined by the investigators to be unsuitable for inclusion in the study
9. Patients with evidence of neurological disorders (such as peripheral neuropathy), neuromuscular disorders (such as multiple sclerosis, Parkinson's disease, etc.), or systemic diseases (such as inflammatory arthritis) that affect bodily function
10. The patient has participated in other clinical trials in the past 3 months
11. Patients with poor adherence, judged by the researchers to be unable to complete the trial according to the study plan, such as schizophrenia and dementia, did not provide consent to volunteer to participate in the clinical study