This study was a retrospective, multicenter study that aimed to determine whether the clinical and radiological outcomes of patients with obesity after BELD are different compared with those of non-obese patients. BELD can be considered a relatively useful surgical method in patients with obesity because there is no difference in the improvement of the patient’s clinical picture, radiological results, and complications such as recurrence and reoperation.
It is currently controversial whether patients with obesity have better outcomes after lumbar surgery than patients without. According to previous studies, patients with obesity had worse outcomes in terms of surgery-related factors such as excess blood loss, length of hospital stay, operative time, and surgical site infection as a result of lumbar MISS [27]. In a study on lumbar interbody fusion with MISS, the obese group showed more complications and poorer results, such as longer hospital stays, than the non-obese group [28]. While patients with obesity reported poor clinical outcomes after undergoing lumbar MISS, according to some studies, there was no difference in clinical results between patients with and without obesity after microscopic discectomy [17]. And for disc herniation, there is a study that gender is not related to the success of conservative treatment or surgical treatment, and the occurrence of recurrent disc herniation after surgery [29,30,31]. Therefore, we designed this study and analyzed the results to determine the clinical and radiological results of BELD in patients with obesity and gender difference with HIVD.
Conducting spinal surgery on patients with obesity is challenging for several reasons: (1) anesthesia is problematic; (2) the abdominal pressure can increase when using a normal Wilson frame to hold the patient in the prone position; therefore, bleeding can occur more often, which has been reported to be related to the occurrence of wound problems or surgical site infections [15, 16]; and (3) it is difficult to access the surgical field during open surgery and the field of view is limited. In particular, the working space of the tubular retractor used in the microscopic technique becomes smaller, and it is more difficult to maneuver it when the length of the tube is increased. However, because there is a high degree of freedom in moving the instrument in BESS, the difficulty of the operation is not substantially increased. Therefore, biportal endoscopy is considered more suitable than microscopy when performing spinal surgery on patients with obesity with HIVD.
BESS reduces the size of the incision and because constant pressure is generated by the continuous water irrigation during surgery in this technique, intraoperative bleeding and the infection rate can be reduced [32]. Patients with obesity require a more notable incision and have greater muscle depth than patients without obesity, making the use of electrocautery inevitable. However, because BESS uses radiofrequency and not electrocautery, less muscle injury is expected (Fig. 4) [33].
Our study found no difference in the clinical and radiological results between the obese and non-obese groups after BELD. This may result from the advantages that BELD offers regarding a better surgical field of vision and less muscle injury. Previous studies have shown that obese people are more likely to undergo infection and excessive bleeding after spine surgery [14,15,16]. However, in our study results, we confirmed that there was no difference in the amount of bleeding and the infection rates between obese and non-obese groups. Through this, it is possible to know the advantages of the BELD compared to the conventional surgical techniques. In addition, in a study on microscopic discectomy surgery, ODI scores also showed a tendency to decrease as BMI increased [17]. In this study, it was confirmed that there was no difference in ODI scores after surgery between the obese and non-obese groups. This suggests that using an endoscope rather than a microscope in the obese disc herniation patient’s surgery could lower the degree of disability in patients after the surgery. Of course, a well-designed study is needed for this. Therefore, BELD is considered a good option for spinal surgery in patients with obesity.
In demographics, 1:1 age and sex matched case control studies were conducted to reduce bias. In this study, no study results were obtained according to age or gender. In a follow-up study, it would be useful to stratify age and compare surgical outcomes according to gender.
This study has some limitations. First, it was retrospective and involved a small number of patients. BELD is a relatively recent surgical development, and thus few patients with obesity were available for this study [20, 34]. To overcome this limitation, we recruited patients from two institutions and reduced selection bias through case-control matching. Second, the postoperative follow-up period was relatively short (12 months). Although clinical outcomes and recurrence that may change after 12 months have not been studied, the results up to 12 months seemed similar to those of the Spine Patient Outcomes Research Trial study, which followed up similar patients for 3 years. Therefore, it is thought that the subsequent course will show similar results. Although clinical outcomes after several years are important, the clinical outcomes at 12 months after surgery are also valuable; as such, the current study can be clinically meaningful. Third, we used PROs to evaluate clinical outcomes to obese and non-obese patients in our study. These measure the subjective degree of pain, disability, and quality of life of patients. According to a study, patients with obesity performed more self-assessments than those without obesity and showed a tendency toward negative self-assessment [35]. Therefore, differences may have already occurred during the data collection process in obese and non-obese patients. To resolve this difference, while the patient was completing the questionnaire, the investigator objectively explained the questions to allow the patient to select an appropriate score for the symptoms and discomfort they currently felt.
The long follow-up period more than 1 year after surgery in a study designed as a randomized controlled trial and investigating various risk factors that can affect the outcome of surgery is thought to be able to determine the results of BELD surgery more accurately in obese patients in the follow-up study.