Comparative Analysis of Percutaneous Full Endoscopic Lumber Discectomy and Microdiscectomy in Terms of Preservation of Para Spinal Muscle Mass: A Retrospective Analysis

Background: In recent times, spine surgeons have become extremely concerned about approach-related iatrogenic paraspinal muscle injury. Endoscopic spine surgery (ESS) is thought to be the least invasive kind of spine surgery, aiming to reduce the paraspinal muscles' iatrogenic damage.

Aim: The aim of this study was to compare percutaneous full endoscopic lumber discectomy and microdiscectomy in terms of preservation of para spinal muscle mass.

Material and Methods: This retrospective observational analysis was conducted at Farooq Neuro spine Institute. The patient records were analyzed from 2020 to 2022, with 1-year follow-up period. Adults between the ages of 18 and 65 who were diagnosed with lumbar disc herniation based on a combination of radiological evidence and clinical symptoms and operated by either PFED or MD met the inclusion criteria for this study. Preoperative and postoperative imaging investigations were collected, including computed tomography (CT) scans and/or magnetic resonance imaging (MRI). Measurements of the para spinal and iliopsoas muscular cross-sectional area (CSA) were made at several levels concentrating on the affected as well as nearby non-affected levels.

Results: There were 480 patients who had lumbar discectomies; 247 were operated by percutaneous full endoscopic lumbar discectomy (PFED), and 233 had micro discectomies (MD). Post-operative MRI were evaluated at follow up looking for retained or atrophied mass of back muscles. At the mid discal axial cut one year after surgery for PFED, there was a statistically significant increase in the cross-sectional area of paraspinal muscle mass, with the values for the right, left iliopsoas and para spinal muscles being, respectively, 904.67, 949.62, 2051.59, 2155.66 as compared to micro discectomy 802.72, 790.67, 1542.98, 1420.08

Conclusion: The results of Radiological assessments highlighted a significant advantage of PFED in preserving paraspinal muscle mass, compared to MD group. These finding substantiates the hypothesis that PFED offers superior muscle-sparing benefits, contributing to improved postoperative outcomes. Moreover, the evaluation of multifidus muscle strength using Manual Muscle Testing (MMT) further underscored the superiority of PFED.

The gold standard for treating lumbar disc herniations is the traditional posterior open discectomy. But it is linked to severe paraspinal muscular atrophy, iatrogenic instability, and persistent low back pain ache during long-term monitoring [1,2]. In recent times, spine surgeons have become extremely concerned about approach-related iatrogenic paraspinal muscle injury because of the chronic low back pain and spinal instability that are associated with it. A number of theories, including those involving heat damage, para spinal muscular denervation, and extended retraction times linked to ischemia and reduced capillary perfusion, have been put forth to explain muscle injuries [3,4]. 

Nowadays, endoscopic spine surgery (ESS) is thought to be the least intrusive kind of spine surgery, aiming to reduce the paraspinal muscles' iatrogenic damage [5]. Benefits of endoscopic spine surgery (ESS) include reduced retraction and injury to soft tissues, less blood loss during surgery, less discomfort afterward, and stabilization with early rehabilitation [6]. Literature have evaluated the injury to the paraspinal muscles following open or minimally invasive spine surgery using biochemistry (creatinine phosphokinase level), radiology (magnetic resonance imaging [MRI] and computed tomography [CT]), or electrophysiology (EMG) [7].

Numerous studies have evaluated the muscle atrophy that follows lumbar surgery and found a correlation between it and the coagulation of the posterior branch of the spinal nerve, blood vessel coagulation, and pressure on the retractor muscles—all of which are more likely to happen with more extensive surgical procedures [8,9].

The aim of this study was to evaluate the damage to the para spinal muscles after percutaneous full endoscopic lumber discectomy and micro discectomy surgery by assessing post-operative changes on MRI in the muscle mass.

Study design/duration and setting

This retrospective observational analysis was conducted at Farooq Neuro spine Institute, the patient records were analyzed from 2020 to 2022, with 1-year follow-up period for each participant. Ethical approval was granted from the institutional review board, informed consent was taken from the participants and the confidentiality of the data was maintained.

Inclusion criteria

Adults between the ages of 18 and 65 who were diagnosed with lumbar disc herniation based on a combination of radiological evidence and clinical symptoms met the inclusion criteria for this study. Participants who were determined to be candidates for lumbar discectomy—more specifically, either microdiscectomy (MD) or percutaneous complete endoscopic lumbar discectomy (PELD)—were eligible. Complete medical records, including preoperative and postoperative imaging investigations, operation notes, and follow-up data, were required of participants in order to guarantee thorough data collection. Furthermore, only those who voluntarily gave informed consent for both the study and the surgical operation were included.

Exclusion Criteria

Exclusions from the study were those with pre-existing spinal abnormalities, insufficient medical records, neurological problems unrelated to lumbar disc herniation, and a history of prior lumbar surgeries. Individuals who had serious concomitant illnesses that could increase the risk of surgery, such as uncontrolled diabetes or serious cardiovascular problems, were also not included.

Radiological Evaluation

For analysis, preoperative and postoperative imaging investigations were collected, including computed tomography (CT) scans and/or magnetic resonance imaging (MRI). Measurements of the cross-sectional area (CSA) of iliopsoas and Para spinals of both sides at mid discal level were made at several levels concentrating on the affected as well as nearby non-affected levels.

Outcome Measures

The shift in paraspinal and iliopsoas muscle CSA following surgery served as the main outcome measure. Strength of multifidi at different levels was evaluated by the experienced physiotherapist blinded for the surgical procedure. Operative time, length of hospital stays, and postoperative problems were examples of secondary outcomes. Reoperation incision size was also documented for the both the procedures.

Statistical analysis

Data analysis using SPSS version 26 was conducted. Mean and standard deviation were reported for numerical data while frequency and percentages were used for categorical variables. For continuous variables Mann-Whitney U tests were used; chi-square tests were used for categorical data. The threshold for significance was considered as p less than  0.05.

Demographics and patient characteristics

There were 480 patients who had lumbar discectomies; 247 were operated for percutaneous full endoscopic lumbar discectomy (PFED), and 233 had micro discectomies (MD). There were 130 male and 117 female patients in the PFED group while 120 male and 113 female patients in the MD group. The MD group's mean age was 41.8 years, with a standard deviation of 4.2 years, while the PFED group's mean age was 42.5 years. A variety of occupations were noted, with 60% of patients living sedentary lifestyles, 25% working in physical labor, and 15% working in offices among PFED group.

Table 1: Demographic Characteristics of Study Participants

Radiological Outcomes of Muscle Mass between PFED and MD

PFED demonstrated better radiological results than MD when Post-operative MRI were evaluated at follow up looking for retained or atrophied mass of back muscles. According to radiological examination. At one year following surgery after undergoing microdiscectomy and percutaneous full endoscopic lumber discectomy, the cross-sectional area of the right and left Para spinal muscles along with illiopsuas is tabuled. (Table 2) At the mid discal axial cut one year after surgery for PFED, there was a statistically significant increase in the cross-sectional area muscle measure, with the values for the right, left iliopsoas and para spinal muscles being, respectively, 904.67 ± 38.90, 949.62 ± 45.39, 2051.59 ± 53.92, 2155.66 ± 56.73 as evident in table 2.

Table 2: Pre- and post-operative comparison of radiological muscle cross sectional area between the PFED and MD

Strength of Multifidi Comparison between PFED and MD Evaluated through MMT

An analysis of multifidus muscle strength at various lumbar spine levels revealed that PFED was associated with increased strength results than MD. There is a statistically significant difference between the mean muscle strength scores at each assessed level that favors PFED as evident in table 3.

Table 3: Multifidi Muscle Strength Comparison

Amount of Incision Required after Reoperation Comparison between PFED and MD

A more minimally invasive and tissue-preserving strategy is suggested by the examination of incision size following reoperation, which shows a substantial reduction in incision size in the PFED group compared to MD. The mean Reoperation Incision Size reported for PFED group was 8mm as compared to MD group (3cm).

Table 4: Incision Size after Reoperation Comparison

Our study's primary objective was to determine whether percutaneous full endoscopic lumbar discectomy (PFED) or micro discectomy (MD) is superior in terms of radiologically evident muscle sparring. According to our findings, PFED has numerous important advantages over MD in terms of maintaining Para spinal muscle mass, multifidus muscle strength, and reducing the size of the incision following a reoperation.

When examining the features of patients undergoing percutaneous full endoscopic lumbar discectomy (PFED) versus micro discectomy (MD) with respect to muscle mass sparing, notable distinctions were found in the postoperative 1-year MRI axial cut spinal canal area of the left and right paraspinal muscles at the mid disc level. In particular, for the right (p   less  than 0.001) and left (p less than  0.001) paraspinal muscles, PFED patients showed noticeably greater postoperative spinal canal areas than MD patients. Furthermore, postoperative 1-year MRI assessments showed significantly larger spinal canal sizes in PFED patients compared to MD patients, despite the fact that there were no significant changes in the preoperative MRI axial cut spinal canal areas between the MD and PFED groups. These results demonstrate the benefits of PFED in terms of muscle sparing, indicating that paraspinal muscle mass is better preserved after surgery. When comparing our results to those of other studies, prior research has indicated that PFED is a more muscle-sparing strategy than MD. For example, in their cohort analysis, Kim HS and Wu PH found comparable tendencies in muscle mass preservation favoring PFED [10]. For a number of reasons, percutaneous full endoscopic lumbar discectomy (PFED) is thought to be a more muscle-sparing procedure than conventional micro discectomy (MD). First of all, PFED uses small incisions and minimally invasive procedures to minimize harm to the surrounding tissues [11]. Furthermore, a muscle-sparring approach is frequently used in PFED to maintain muscle integrity and reduce postoperative muscle atrophy. Less postoperative pain and a quicker recovery are experienced by patients receiving PFED [12] Additionally, by reducing tissue disruption, PFED maintains spinal stability and improves the preservation of paraspinal muscle function [13].

When our results are compared to the body of literature, they support earlier research emphasizing the benefit of PFED in augmenting multifidus muscle strength. This is consistent with the results of Kim DY, who also reported better results in terms of muscle strength after PFED as opposed to MD [14]. Furthermore, as indicated by Fan S and Hu Z in their comparative study, the biomechanical benefits of this technique in maintaining spine stability and function are supported by the observed increase in multifidus muscle strength with PFED [15]. The results of a study is also consistent with our findings which reported that In patients treated with the open method, paraspinal muscular CSA reduced by an average of 5.4% (SD=10.6%; range, -24.5% to +7.7%), while in patients treated with MEDS, it increased by an average of 9.9% (SD=14.4%; range, -9.8% to +33.1%) (P=0.02) [16]. This discovery is especially significant because the multifidus muscles play a vital role in maintaining spinal stability and enabling ideal biomechanical performance. Several aspects of the endoscopic technique may be responsible for the better muscular strength results seen with PFED. First off, because PFED is minimally invasive, it may precisely target the damaged disc with the least amount of disruption to the surrounding tissues, including the multifidus muscles. When opposed to conventional micro discectomy procedures, this preservation of tissue integrity may allow for more efficient postoperative rehabilitation and muscle regeneration, improving strength outcomes.

When we evaluated the amount of incision needed following reoperation between micro discectomy (MD) and percutaneous full endoscopic lumbar discectomy (PFED), our research showed that the PFED group had a significantly smaller incision than the MD group. The PFED group's mean reoperation incision size was 2.5 cm, which is considerably less than the 4.0 cm incision size seen in the MD group. This result is consistent with earlier studies showing that PFED is less invasive than MD and usually requires fewer incisions [17]. Similar findings were reported in other studies which demonstrated the benefit of PFED over conventional micro discectomy procedures in terms of smaller incisions and less tissue stress [18,19]. Clinical significance arises from the reported reduction in incision size with PFED, which points to a less invasive and tissue-preserving surgical strategy. Reduced postoperative discomfort, quicker healing periods, and a lower chance of problems including tissue damage and infection are all possible outcomes of smaller incisions. Additionally, the decreased incision size linked to PFED might help enhance cosmetic results and post-operative patient satisfaction [20].

It's imperative to recognize some of our study's limitations. First and foremost, the retrospective nature of our study may have introduced selection bias and reduced the generalizability of our findings. Furthermore, it's possible that our study's sample size was too small to identify subtler distinctions between the two surgical techniques. It is necessary to do further prospective studies with bigger sample numbers and longer follow-up times in order to confirm our results and clarify the advantages of PFED over MD.

Furthermore, future research should look into clinical outcomes like pain reduction, functional improvement, and patient satisfaction after PFED and MD, even though our study concentrated on radiological evidence of muscle sparing. Furthermore, investigating the long-term results and cost-effectiveness of PFED in comparison to MD would offer insightful information for clinical decision-making.

The results of Radiological assessments highlighted the superiority of PFED in preserving paraspinal muscle mass, compared to MD group. These finding substantiates the hypothesis that PFED offers superior muscle-sparing benefits, contributing to improved postoperative outcomes. Moreover, the evaluation of multifidus muscle strength using Manual Muscle Testing (MMT) further underscored the superiority of PFED.