Low back pain (LBP) is one of the most leading cause of chronic pain worldwide and 70-85% of adults have experienced LBP during their lifetime. The one of most common symptom of lumbar disc herniation (LDH) is sciatica, affecting about 1-5% of people worldwide. Almost two thirds of patients suffer from continuous pain even after 12 months of the first episode of LBP. Moreover, such persistent pain reduces the patient's quality of life and increases the social and economic burden due to increased hospital stay and surgical treatment. Traditionally, the primary treatment of LDH is non-surgical treatment including pain medication, rehabilitation exercise, and spinal injection, and about 70% of the patients show improvement of pain within 4 weeks. Surgical treatment is considered if there are neurological symptoms such as bladder dysfunction or progressive muscle weakness, or if symptoms persist for more than 6 weeks despite conservative treatment.

The patients with LDH usually experience sudden onset of LBP with radiating pain to lower extremity. Sensory symptoms such as focal paresis or motor weakness of specific myotome can also occur in the LDH patients. The symptoms and area of pain can vary due to the herniation level and severity. Michigan State University (MSU) classification was often used to evaluate and select for surgical treatment of LDH patients. In this classification, the herniated disc is evaluated using T2 axial magnetic resonance imaging (MRI) scan and classified by its size and location. The size of disc herniation is classified into 1 (\*\<50% of the distance to the intra-facet line), 2 (intra-facet line\>\*≥50% of the distance to the intra-facet line), or 3 (beyond intra-facet line). Then the position is classified in to A (central), B (lateral), or C (far lateral). The disc herniations size 3 (beyond intra-facet line) and zone B (lateral) or C (far lateral) are known to have greater impact on nerve compression, which tend to cause worse sciatica and neurologic symptoms and require surgical treatment. Moreover, the patients with larger lumbar disc herniation areas tend to show better outcomes with surgical treatment than conservative treatments and high-grade spinal canal stenosis patients had higher need for surgical treatment.

Over the past few years, various minimally invasive disc decompression procedures, were developed and used in LDH patients. These minimally invasive disc decompression techniques include intradiscal electrothermal therapy, radiofrequency annuloplasy, percutaneous disc decompression, nucleoplasty, and percutaneous laser disc decompression, which caused less damage to spinal structures and reduced tissue destructions than conventional surgical treatments. In particular, nucleoplasty was proven as effective as open discectomy in the treatment of single level lumbar disc herniation. The L'DISQ (U\&I Co., Uijeongbu, Korea) is one of the safe and effective minimally invasive disc decompression procedures which introduced in 2011. In contrast to most percutaneous nucleotomy procedures that used rigid tip, the L'DISQ used a navigable tip and flexible handle allowing resection of the posterolateral or posterior median disc tissue without thermal damage.

The L'DISQ can be mainly performed in patients with less severe LDH while surgical treatment was mainly indicated in patients with severe LDH with neurologic symptoms. However, surgical treatment such as lumbar discectomy or spinal fusion increase hospitalization time and may increase financial burden of patients. And spinal fusion surgery might lead to delayed complications such as back muscle weakness or adjacent segment disease. Moreover, patients with severe LDH might refuse or not be able to perform surgery due to medical, financial, or other personal reasons. Recently, studies on the efficacy of L'DISQ or plasma decompression in disc patients are being conducted, and shows similar outcome when compared to surgical treatment in mild to moderate disc herniation patients. However, no studies have been conducted on the efficacy of L'DISQ in patients with severe LDH requiring surgical treatment. Purpose of this study is to report the efficacy of the L'DISQ procedure in patients with severe LDH corresponding to MSU classification 3.