PAIN INTENSITY AND FUNCTIONAL STATUS 30 DAYS AFTER SURGERY: DIFFERENCE BETWEEN TRANSFORAMINAL AND INTERLAMINAR PERCUTANEOUS ENDOSCOPIC LUMBAR DISCECTOMIES

Objective: To compare the differences between transforaminal and interlaminar endoscopic approaches in terms of pain intensity and functionality 30 days after the surgical procedure. Methods: A retrospective cohort study, with patients treated by percutaneous interlaminar or transforaminal endoscopic discectomy at the Spine Service of the ISCMPA, in southern Brazil. Data were collected from the patients’ electronic medical records by two independent physicians. The clinical outcomes of pain intensity and lumbar functionality were evaluated, respectively, using the visual analogue scale and the Oswestry Disability Index. Results: Thirty-six patients were included in the study, with a mean age of 50.8 ± 15.3 years, 19 (52.8%) of whom were males. As for the clinical outcomes for both transforaminal and interlaminar percutaneous endoscopic approaches, we observed a statistically significant reduction in pain intensity (mean difference of 3.5 points, p < 0.001) and a statistically significant improvement in functionality (mean difference of 33.2 points, p < 0.001) when we compared the pre-and 30-day postoperative periods, with no significant differences in terms of approaches. The type of technical approach also differed in relation to the patients’ age, the location, type, and migration of the herniated disc, and the patient’s time in the operating room. Conclusion: There was a similar effect on pain reduction and restoration of lumbar functions, 30 days after percutaneous endoscopic discectomy, in both technical approaches, with no significant differences between them. Level of Evidence III; Retrospective comparative study.


INTRODUCTION
2][3][4][5][6][7] The surgical options include open discectomy, microdiscectomy, microendoscopic discectomy, and percutaneous endoscopic lumbar discectomy. 8Currently, microdiscectomy is considered the gold standard procedure for the treatment of lumbar disc herniation. 9,10However, minimally invasive spinal surgery has been highlighted in recent years. 11,12There are different approach strategies based on the morphology and the location of the herniated disc. 1,2,13,14The technical approaches include the transforaminal and interlaminar percutaneous endoscopic discectomies. 3,5,15,16he transforaminal endoscopic approach allows the resection of disc herniations located in the foramen or in the lateral recess ventral to the transversal nerve root and is generally applied to spinal segments between L5 and S1, 6,14,17,18 but also allows access to central disc herniations.The interlaminar endoscopic approach is indicated for resections of subarticular disc herniations, particularly in L4/L5 and L5/S1. 19,20The interlaminar approach is believed to have an advantage over the transforaminal approach in migrated lumbar disc herniations. 21However, this approach can reach the herniated disc tissue through the spinal canal, which can increase the risk of epidural fibrosis and the formation of scar tissue. 22ven though total endoscopic discectomy can be performed by interlaminar and transforaminal approaches, it is difficult to determine which one is better in the treatment of lumbar disc herniations.In some cases, sufficient decompression for a herniated disc in L5-S1 could be difficult to achieve via transforaminal access; in these cases, the interlaminar approach is preferred. 23Ruetten et al., 24 were the first to perform discectomy and decompression of the intervertebral disc, creating a foramen in the vertebral canal between the upper and lower vertebral discs.6][27] In addition, the lack of a standard to assist in deciding on an endoscopic approach, especially in relation to disc herniations at the L5-S1 level, remains a problem in surgical practice.
Thus, the objective of the present study was to compare the differences between the transforaminal and interlaminar endoscopic approaches in terms of pain intensity and functionality 30 days after the surgical procedure and, secondly, to evaluate the relationship between the approaches and the sociodemographic and surgical variables.

Design
Retrospective cohort study.

Population
Patients diagnosed with disc herniation, who underwent percutaneous endoscopic lumbar discectomy, between January 2019 and October 2020, and follow-up at the Spinal Surgery Service of the Complexo Hospitalar Irmandade Santa Casa de Misericórdia de Porto Alegre (ISCMPA), Brazil, were included.
To establish the diagnosis, the patients routinely undergo an imaging exam (magnetic resonance or computed tomography), which identifies the type of disc herniation, the vertebral segment, and the laterality corresponding to the radicular signs and symptoms.Surgical treatment is considered for patients with radicular pain, signs of radiculopathy, with evidence of nerve root compression, when a minimum of six weeks of conservative treatment (physiotherapy, medication with anti-inflammatory agents and opioids, corticosteroid injections) was not effective.

Variables
The sociodemographic variables included sex and age, while the clinical variables included presence of neuropathy, pain intensity, evaluated by administration of the analog visual scale (VAS), and functional status, measured by the Oswestry index (ODI).The ODI score varies from 0 to 100, with the higher scores indicating greater disability related to pain, while the VAS scores range from 0 to 10, where the more intense the pain, the higher the score.
The variables related to the surgical procedure and type of lumbar herniation were as follows: technical approach of the percutaneous endoscopic discectomy (interlaminar or transforaminal), type of disc herniation (central, subarticular, foraminal, and extraforaminal), laterality, migration of the herniation evaluated in the sagittal plane (without migration, cranial migration or caudal migration), surgical segment (L3-L4, L4-L5, L5-S1), and time the patient remained in the operating room.

Surgical techniques Transforaminal endoscopic lumbar discectomy
This is considered the traditional approach for the total endoscopic lumbar discectomy.First, the patient is placed in the prone position and undergoes local anesthesia and conscious sedation.Then, the distance from the incision in the skin is planned, depending on the patient's body size, the location of the disc herniation, and the foraminal dimensions, being approximately 8 cm in L3/L4, 10 cm in L4/L5, and 12 cm in L5/S1.After confirming the ideal positioning of the puncture needle, a skin incision and dilation of the soft tissues are performed.Keeping the guidewire in place, foraminoplasty is performed using a bone drill to widen the intervertebral foramen.The working cannula is then introduced.Disc forceps are used to remove the disc herniation, and bipolar probes are used to clot bleeding points.The decompression is considered sufficient when all the herniated mass has been removed and the pulsation of the dural sac has been confirmed under endoscopic vision (Figure 1A).

Interlaminar endoscopic lumbar discectomy
This technique is performed under general anesthesia, with the patient in the ventral position.It consists of the introduction of an endoscope through an entry point at the lateral edge of the interlaminar space on the side of the lesion in the anteroposterior view and parallel to the disc space in the lateral view.Then, a dilator is introduced and fitted into the interlaminar space.A cannula is introduced into the epidural space through an opening in the yellow ligament so the margin of the nerve root is reached.After slight retraction of the nerve root, the peridural dissection is performed.Then, the protruding disc pieces are found and removed using disc tweezers (Figure 1B).

Logistics
The radiological exams for diagnosis of the lumbar disc herniation were reviewed by two independent radiologists with at least two years of experience.
Data were collected from the electronic patient medical records by two independent physicians.
Patients who undergo lumbar disc herniation surgery are routinely followed up in both pre-and postoperative consultations at outpatient clinics.During these consultations, the patients are assessed clinically and pain intensity and functionality questionnaires, previously developed by the ISCMPA Surgery Service are administered.These results are recorded in the patients' electronic medical records.

Statistical analysis
The data were analyzed using the Statistical Package for the Social Sciences program, version 22.0 for Windows (SPSS Inc., Chicago, IL, USA).
The Shapiro-Wilk test was used to evaluate the normality of all the parameters.The continuous variables were described as mean and standard deviation or median and interquartile interval, while the categorical variables were described as absolute and relative frequencies.
The comparative analysis between the transforaminal and interlaminar endoscopic lumbar discectomies was performed according to type and data distribution.For quantitative data with normal distribution, the differences between groups were evaluated using the independent samples t test, and differences between pre-and postoperative data within the groups were evaluated using the paired sample t test.The qualitative data were analyzed using the chi--square, using the Yates' correction or Fisher's exact test if needed.
All the statistical tests used were two-tailed and a level of significance of 5% was established.

Ethics
This study was approved by the Institutional Review Board of the Irmandade Santa Casa de Misericórdia de Porto Alegre (no.4380117) and complied with all the Declaration of Helsinki norms for studies in humans.The informed consent form was waived as this was a retrospective longitudinal study.All the researchers signed a declaration of confidentiality for both patient and study data.

RESULTS
Thirty-six individuals, with a mean age of 50.8 ± 15.3 years, 19 (52.8%) of whom were male, were included in the study.The overall sample characteristics are shown in Table 1.
Table 2 shows the differences between the two percutaneous endoscopic discectomy approaches and the demographic and surgical variables.There was a statistically significant difference in relation to the age of the patients, the locations, and the type and migration of the disc herniation.No significant differences were observed for any of the other variables.
The mean difference in visual analog scale scores reflected a reduction of 3.5 points (CI 95%, 2.5 -4.6, p < 0.001), decreasing from a mean of 7 ± 1.5 points in the preoperative period to 3.5 ± 2.6 points following surgery.The Oswestry index dropped by an average of 33.2 points (CI 95%, 27.2 -39.3, p < 0.001), with mean values of 54.2 ± 21.8 and 20.9 ± 16.5 points in the pre-and postoperative periods, respectively.
Table 3 shows the mean differences in both scales for both transforaminal and interlaminar approaches.Despite the 30-day postoperative clinical improvement for both approaches, no statistically significant difference between the techniques was observed, either in pain intensity (p = 0.051 and p = 0.456, respectively) or functionality (p = 0.198 and p = 0.844, respectively).
The patient spent an average of 203 ± 40.2 and 182 ± 45.7 minutes in the operating room for the transforaminal and interlaminar approaches, respectively.No peri-or postoperative complications, such as dislocation, dural rupture, nerve root injury, or infections, were observed.In addition, none of the patients used analgesics, such as opioids, during the recovery period.All the patients were discharged soon after anesthetic recovery, with no need for readmission to the hospital.

CONTRIBUTIONS OF THE AUTHORS:
Each author made significant individual contributions to this manuscript.CAGC and RGJ: conception of the topic, design of the research project, data collection, statistical analysis, writing, review, and final approval of the work; ODM: data collection, active participation in the discussion of results, review, and final approval of the work; SZ: conception of the topic, writing, and final review; CDB, NRR, FL, and YK: conception of the project, surgeries, discussion of the results, writing, review, and final approval of the work.

DISCUSSION
In the present study, we observed a reduction in pain intensity and an improvement in functionality thirty days following surgery, with no statistically significant difference between the two percutaneous endoscopic discectomy approaches.There were differences between the access techniques for the variables of patient age, the herniation location, type, and migration, and the time the patient remained in the operating room.
20]28 Although there was no significant difference between the techniques, recent studies suggest adopting the interlaminar technique because it presents results similar to those of the transforaminal approach, but with the advantage of a wider anatomical space, reducing surgical time and, consequently, radiation exposure for the patient and the team. 5,19,29In addition, this technique has been shown to preserve most of the yellow ligament and reduce adhesion formation in the epidural scar. 30Another strong point is that it can be easily used by surgeons with experience in microendoscopic discectomy, since they are very similar techniques.
On the other hand, discectomy performed using the transforaminal approach endoscopic technique requires greater vigilance against possible vascular and visceral organ injuries. 31In addition, in cases of disc herniation at the L5-S1 level, the high iliac crest and narrow foramen determine the difficulty of the technique via this approach. 281][32][33] In addition, a recent study suggests an approach combining both techniques for disc herniations with a high potential for migration as an alternative option for these patients. 29ll the study patients successfully completed the surgery and the 30-day postoperative period without complications.These include infection, spinal cord injury, cerebrospinal fluid leakage, nerve root damage, and postoperative sensory abnormalities. 13,18he present study has several limitations.First, it was a retrospective cohort study with data limited to the protocols routinely used in ISCMPA outpatient consultations.Second, there was no control group, that is, patients treated with open lumbar discectomy or microdiscectomy.Third, only the operating room time was recorded, that is, the time from the moment the patient arrived in the operating room until the moment they were released to the recovery room, and not the surgical time.Finally, the study only evaluated one postoperative moment.However, it is important to emphasize that the main objective of this study was to evaluate the difference in pain intensity and changes in lumbar functionality in relation to the type of surgical approach in the first month following percutaneous endoscopic discectomy.

CONCLUSION
In conclusion, a similar effect was observed in pain reduction and recovery of lumbar function 30 days after percutaneous endoscopic discectomy using both technical approaches, with no significant differences between them.Future studies with larger sample sizes and follow-up times, are still necessary.
All authors declare no potential conflict of interest related to this article.

Table 3 .
Mean differences between preoperative and 30-day postoperative pain intensity and functional status by percutaneous endoscopic lumbar discectomy technical approach.