Unilateral biportal endoscopic discectomy versus percutaneous endoscopic lumbar discectomy in the treatment of lumbar disc herniation: a retrospective study

Lumbar disc herniation (LDH) is a primary cause of back pain and sciatica, affecting 1% to 5% of the population annually [1]. Although nonsurgical care remains the mainstay of initial treatment, discectomy surgery is applied to effectively alleviate symptoms that persist for prolonged periods of time [2]. Minimally invasive spine surgery technology has been widely used for treatment of LDH [3]. In percutaneous endoscopic lumbar discectomy (PELD), which was first described in the early 1980s [4], a surgeon uses a unilateral single channel endoscopy to directly reach the target position through Kambin’s triangle, remove the herniated disc tissue and release nerve roots [5]. PELD has not only yielded successful outcomes compared to conventional open or microendoscopic surgery, but has shown advantages in controlling muscular trauma, shortening hospital stay, and maintaining the spinal segment stability [6]. Consequently, it has been standardized as a representative minimally invasive spine surgical technique for LDH [7].

Unilateral biportal endoscopic discectomy (UBE) is a rapidly growing surgical method that uses arthroscopic system for treatment of LDH. Notably, the technique has two independent channel endoscopies, which provide a clear and magnified surgical field that improves operational flexibility, helps the surgeon to perform precise and extensive decompression [8]. Results from preliminary clinical trials, and the complications of UBE in LDH treatment have been documented [9]. In the present study, we compared the safety and efficacy between UBE and PELD for treatment of patients with LDH.

The significant improvements in pain score and functional status observed in both groups at 1 day, 1 month, and 6 month follow-ups were consistent with prior finding [12‐14]. The modified MacNab criteria revealed an acceptable patient satisfaction in UBE and PELD groups, indicating that both techniques were equally effective in treating LDH. However, UBE technique was linked to significantly higher TBL, higher IBL, higher HBL, longer operation times, longer hospital stays, longer incision lengths, and more total hospitalization costs.

The rapid development of high-resolution endoscopes has increased interest in minimally invasive spine surgery technology. with more emphasis now on enhanced recovery after surgery, PELD, which results in favorable long-term outcomes [15], has been standardized as a representative minimally invasive spine surgical technique for LDH treatment [7]. The integrity of the paraspinal muscle was preserved by directly reaching the target position using a muscle-splitting technique with sequential dilators and blunt obturator [12]. Notably, PELD has various advantages over other minimally invasive discectomy approaches, such as MD and MED, including less occurrence of paravertebral muscle injury, preservation of bony structures, and rapid recovery [15, 16]. Use of the UBE technique for treatment of disc herniation was first described by Antoni in 1966 [17]. Since then, the technique has been rapidly applied in recent years. Generally, it combines muscle splitting and small extent muscle-stripping techniques to create a working space in the interlaminar space using serial dilators, bipolar radiofrequency probe, and continuous saline irrigation. Consequently, it provides a clear visualization of neural elements, surrounding soft tissues, vascular and bony structures [8], thereby creating a conducive environment for delicate nerve manipulation process and an easy and safe decompression. The UBE technique provides a minimally invasive option for nerve decompression in patients with posterior epidural migration of herniation disc, lumbar spinal stenosis and lumbar osteoporotic vertebral compression fracture [18‐20].

However, the learning curve for UBE technique remains steep. Creating the working space and identifying spinolaminar junction were a great challenge in our first several cases; however, our personal experience indicates that, a definite preoperative orientation and trajectory, a clear anatomic knowledge and familiarity with UBE instruments are correlated with a shorter procedure duration. Furthermore, adequate hemostasis and delicate dissection of meningo-vertebral ligament were vital to avoid complications such as such as postoperative epidural hematoma and iatrogenic durotomy.

To our knowledge, only one report has compared median follow-up clinical outcomes between UBE and PELD for LDH treatment [21]. Specifically, 40 LDH patients in PELD (20 cases) and UBE (20 cases) group were analyzed, and favorable outcomes were achieved over a 6-month follow-up period. This study included patients with single L4/5 LDH and collected and evaluated their intraoperative hemorrhages. The present study reviewed patients with L3-4, L4-5 and L5-S1 LDH and then analyzed intraoperative, hidden and total blood loss as a parameter for understanding perioperative blood loss.

In spinal surgery, total blood loss is composed of visible blood loss, including intraoperative hemorrhages and drainage, as well as HBL in which blood extravasates into tissues and accumulates in the surgical field. Notably, compared with visible blood loss, HBL is often overlooked by spine surgeons [22], while an association is found between HBL and perioperative complications [23, 24]. Zhang et al. [25] found that HBL is seriously underestimated and accounts for a large percentage of TBL in minimally invasive transforaminal lumbar interbody fusion. On the other hand, Ao et al. [26] demonstrated that a large amount of HBL existed during percutaneous endoscopic surgery. In this study, PELD group exhibited significantly lower HBL than UBE group, mainly because PELD utilizes an existing natural access, intervertebral foramina, and allowed the surgeon to directly reach the disc without excision of the lamina, and ligamentum flavum. However, the partial laminotomy employed in UBE technique may have caused bleeding of cancellous bone. Our findings were consistent with those of Wang et al. [27] who reported a 469.5 mL of HBL following UBE surgery. However, their study included patients with lumbar degenerative diseases, including LDH, lumbar stenosis, and spondylolisthesis. This study only recruited LDH patients. Surgeons need to pay more attention to HBL within the perioperative management of UBE surgery to further improve patient safety and postoperative outcomes.

Regarding complications, a dural tear occurred in one patient of the UBE group. According to previous research, a dural tear is the most prevalent UBE complication, as evidenced by an incidence rate ranging from 1.5 to 5.8% [9]. The risk factors for dural tear include damage to the dura mater by instruments or radiofrequency, adhesion in the spinal canal, giant disc fragments, and loosened dura [28]. Therefore, it is particularly important to delicately dissect the meningo-vertebral ligament. For small tears of less than 4 mm, absolute bed rest and simple observation are recommended [29], while for larger defects of more than 10 mm, open repair is considered a safe treatment method [30]. Nevertheless, the endoscopic dural repair technique requires further development to improve efficacy and patient safety [31]. We found no dural tear in PELD group. Chen et al. [7] recently evaluated variability in tissue pain during PELD for LDH treatment, and found that with regards to VAS leg, the most intense pain originated from the nerve root/dural sac. This could help surgeons avoid nerve injury, dural sac tear, and other surgical complications by preliminarily judging the nature of tissues according to intraoperative VAS scores of patients under local anesthesia.

This study had several limitations. Firstly, there were no radiologic outcomes such as stability of lumbar spine and adjacent segment degeneration. Secondly, the study adopted a retrospective design. Future studies are expected to adopt prospective, multicenter studies with larger samples sizes, and also compare uniportal and other microscopic endoscopic procedures with long-term clinical outcomes.

Application of UBE for treatment of lumbar disc herniation yielded similar clinical outcomes to PELD, including pain control and patient satisfaction. However, UBE was associated with various disadvantages relative to PELD, including increased total, intraoperative and hidden blood loss, longer operation times, longer hospital stays, and more total hospitalization costs. Although UBE is an effective and minimally invasive surgical technique for treatment of LDH patients, further improvements are needed to narrow down these differences compared to PELD.