Patients who fail to respond to conservative treatment are treated with surgery, the aim of which is to remove the herniated nucleus pulposus to the largest extent possible to relieve nerve compression while minimizing spinal instability [1–4]. IFD is the most commonly performed clinical procedure and is considered the standard procedure for treating LDH. Because the operation is easy to perform and allows a clear field of vision, the technique enables surgeons to reveal and cut the ligamentum flavum and the pathological hyperplasia of bones under naked-eye observation in order to expand and decompress the nerve root canals. Thus, compression of the nerve root and dural sac can be relieved while the normal anatomy of the spine is preserved to the greatest extent possible to ensure patients can undergo early postoperative rehabilitation [5, 6]. Nevertheless, in clinical practice, since the nerve root and dural sac need to be pulled during this surgery to expose the herniated nucleus pulposus, the dura can be injured easily, and there is a high risk of adherent and damaged nerve roots. Moreover, the soft tissue needs to be stripped during this surgery, which can easily lead to denervation of the muscles and is not conducive to postoperative recovery of the patients [14, 15]. In this study, there were two cases of dura mater injury complicated with cerebrospinal fluid leakage. One day after surgery, the severity of lower back pain was significantly higher in Group A than in Group B, which might be related to IFD leading to more trauma.
In recent years, many advancements in spinal endoscopy have been made, and lumbar discectomy under endoscopy has been frequently performed for the treatment of LDH. Transforaminal endoscopic discectomy can be performed to remove the herniated nucleus pulposus directly via the subforaminal safe-triangle approach, thereby eliminating the degenerated nucleus pulposus and its metabolites and reducing the central pressure on the intervertebral disc. Moreover, it can minimize damage to normal tissues and maintain spinal stability [6, 7]. Combined with radiofrequency bipolar haemostasis and reconstruction of the fenestrated fibrous ring, this surgical approach greatly reduces the amount of postoperative scarring around the nerve root, as well as the severity of denervation in the ablation of the intervertebral disc, and it alleviates the postoperative symptoms of lower back pain [16, 17]. Radiating pain in the lower limbs is caused by the dual effects of mechanical compression and chemical stimulation at the nerve root. After the nucleus pulposus is removed, the centre of the intervertebral disc is decompressed, allowing the fibrous ring, especially its herniated portion, to retract, which constitutes the first stage of decompression of the nerve root. When the tongue-shaped end of the working cannula is retracted near the lateral recess, the course of the nerve root and the side of the dural sac can be clearly identified by rotating and turning the cannula. The adhesions and un-retracted bulges and herniations can be removed directly and clearly under the endoscope, achieving the second stage of local decompression of the nerve root. Different types of ring drills used in PTED can be used to enlarge the transforaminal working cannula to a moderate extent, allowing the endoscope to reach any position inside the intervertebral disc and the spinal canal on the affected side to remove the herniated tissue. The shortcomings of incomplete decompression after early transforaminal endoscopic discectomy are thus entirely resolved. After intraoperative injection of methylene blue into the intervertebral disc, the degenerative and damaged tissues are first stained dark blue, while the nerve root, the fibrous ring, and the dural sac are not stained, for the most part, thereby improving the surgeon’s ability to identify the target to be removed.
Compared with IFD, PTED involves a smaller incision and a clearer field of vision, while the ligamentum flavum is not removed and the paravertebral muscles are not dissected. These advantages help reduce the amount of postoperative adhesion and denervation of the nerve root inside the spinal canal. Moreover, local anaesthesia is administered during the surgery to enable communication with the patient during the procedure and prevent nerve damage. Moreover, cannulas of various sizes are used to establish the working cannula, thereby minimizing damage to the spine and ensuring lumbar spinal stability [18, 19]. This study shows that PTED leads to less intraoperative blood loss, faster off-bed rehabilitation, and a shorter length of hospital stay, which is consistent with the results of the previous study. This study also shows that there is no statistically significant difference in surgery duration between the two groups over time. A possible reason for this result is that the surgeons’ expertise in performing minimally invasive techniques is constantly improving in our spine centre, and their level of proficiency is satisfactory.
Different spine surgical options have their respective advantages. The surgical method should be selected according to the type of the herniated disc so that the optimal surgical outcome is obtained, the incidence of postoperative complications is minimized, and ultimately, the patients experience improvement. This study also has some limitations: it had a single-centre retrospective study design, and the patient population was not very homogenous. In the future, a prospective study will be carried out to analyse the efficacy of IFD and PTED in treating LDH.