CES is a rare but serious condition, defined as “a spectrum of low back pain, uni-or bilateral sciatica, saddle anaesthesia and motor weakness in the lower extremities with variable rectal and urinary symptoms” . Different stages of CES show different clinical characteristics and should be treated differently. For patients with CES at the late stage, wide laminectomy may be the first choice for those patients. Patients at the preclinical and early stages have better functional recovery than patients in later stages after surgical decompression . Surgical goals are to relieve local compression as soon as possible to reduce the degeneration and death of sensory neurons in the ganglia. However, traditional surgery usually brings relatively large trauma to patients and may also damage the patient's spinal stability, which in turn increased the risks for posterior spinal fusion rate as well as morbidity and rehabilitation needs. Reducing surgical trauma and maintaining the integrity and stability of the spine are challenges in the treatment of LDH. With the rapid development of modern spine surgery technology, PELD has gained popularity in clinical practice. Cong et al.  pooled results comparing endoscopic discectomy versus open microdiscectomy and found a significantly higher satisfaction rate in patients who underwent endoscopic discectomy. Recent meta-analyses and systematic reviews have reported that transforaminal PELD is comparable or superior to conventional open discectomy in terms of its effectiveness and minimal invasiveness for soft LDH . PELD is a minimally invasive surgery under local anaesthesia, known as endoscopy, and provides huge expectancies for the treatment of CES. Li X et al.  reported that PELD could be used as an alternative surgical method for the treatment of CES in properly selected cases.
In this study, we only took patients with CES at the early and middle stages according to Shi’s classification as the subjects of study. Unlike the Li X study, all of our patients were treated with PELD by a transforaminal lumbar approach. The good and excellent outcome of PELD in our study was 86.67%, corresponding closely to the results of previous studies of conventional open surgery for incomplete CES. These 15 patients with CES treated with PELD techniques under local anesthesia showed that such a procedure is safe and effective.
In fact, patients with disc herniation related CES often have a large volume of herniated lumbar disc materials. If the surgeon does not have sophisticated surgical skills, it is likely that the free nucleus pulposus is not completely removed or a serious nervous injury may occur during the surgery. In this study, the modified MacNab score was fair in 2 cases at the last follow-up. The main reason is considered that the foraminoplasty was not insufficient, and the working cannula was inserted into the spinal canal to further squeeze the nerve, resulting in the aggravation of transient nerve compression during the operation.
Therefore, we need to elaborate the technical details of endoscopic treatment of CES. In the transforaminal lumbar approach, the extent of disc herniation, degree of migration, severity of adhesion, softness of the herniated disc, location of exiting nerve root, risk of dural tear, and concurrent spinal stenosis should be evaluated first. The landing on the disc should be as near as possible to the target and as far as possible from the exiting nerve root, which is the first key to surgical success. Second, we should have performed sufficient foraminoplasty by using an red biggest eccentric trepan, different from the traditional TESSYS step-by-step foraminoplasty, to avoid further compression of the nerve root by the placement of the working channel. This is the most important key point to ensure the success and excellent effect of PELD in the treatment of CES. Because disc herniation, which can cause CES, is huge, if the intervertebral foramen is not fully formed during the operation, it will cause iatrogenic nerve injury. Therefore, adequate lumbar foraminal plasty needs to be emphasize. Reasons for failed endoscopic surgery in CES include incomplete decompression, recurrent herniations, haematoma and cerebrospinal fluid leakage [20,21]. Recently, several authors have emphasized the significance of foraminoplasty [22,23]. Even during the operation, if considered necessary, foraminoplasty should definitely be performed again to enlarge the working space. Finally, the herniated fragment should be completely removed after an adequate release process, and the surgeon should not be in a hurry to directly remove the herniated fragment. We need to explore the ventral and dorsal sides of the nerve root and confirm that decompression is sufficient during the operation.