Contralateral trans-spinous base inclined approach using AUSS for two-level lumbar lateral recess and foraminal stenosis: a case report

Background Lumbar spinal stenosis (LSS) is common in elderly and can significantly impair quality of life. With advances in minimally invasive spine surgery, techniques such as unilateral biportal endoscopy (UBE) and arthroscopic-assisted uni-portal spinal surgery (AUSS) have become mainstream treatments. However, LSS in elderly often involves complex pathology, including spinal instability and multilevel stenosis. Traditional open surgery carries risks of iatrogenic instability, significant blood loss, and suboptimal clinical outcomes. Case presentation A 72-year-old man presented with low back pain radiating to the left lower extremity Physical exam revealed mild left thigh muscle atrophy. Positive femoral nerve stretch test, diminished patellar reflex, and extensor hallucis longus (EHL) strength graded 4/5. Imaging showed mild lumbar scoliosis, grade I anterior spondylolisthesis at L3, and MRI findings of left lateral recess stenosis at L3/4 and L4/5, along with disc herniation, ligamentum flavum hypertrophy, and facet arthropathy. A far-lateral disc herniation at L4/5 was compressing the exiting left L4 nerve root. Given the patient's fragility and surgical risks, we used a novel contralateral trans-spinous base inclined (CTI) approach-AUSS for laminectomy and spinal canal decompression. The patient experienced immediate postoperative pain relief and neurological improvement. Postoperative imaging confirmed effective decompression at both levels with no progression of spondylolisthesis. The facet joint average preservation rate was 93.97%. Conclusion The CTI-AUSS technique is a safe and effective option for treating multilevel lumbar lateral recess and foraminal stenosis in elderly. It provides excellent clinical and radiographic outcomes while preserving spinal stability, protecting paraspinal muscles and facet joints, and reducing the risk of postoperative instability or spondylolisthesis.