Effect of Monopolar Electrocautery and Blunt Dissection on Muscle Damage and Inflammation in Patients Undergoing Lumbar Microdiscectomy

Introduction

Lumbar disc herniation is one of the most common spinal disorders in the general population and requires surgical intervention in cases in which severe and chronic pain or neurological deficits are present. In the posterior surgical approach, a midline longitudinal incision is made, followed by paravertebral dissection and hemilaminectomy; subsequently, discectomy is performed [1]. Iatrogenic muscle and soft tissue injuries occurring during surgery can lead to a high risk of morbidity due to the development of ischemic necrosis and denervation in the paraspinal muscles [2].

Although a small incision during microsurgery provides adequate exposure, dissection of the multifidus muscle, one of the basic stabilizing components of the spine, can cause tissue damage [3]. In the postoperative period, even if neurological decompression is achieved, damage to the paraspinal muscles and thoracolumbar fascia can contribute to persistent low back pain [4]. This situation highlights the need to minimize muscle damage to ensure postoperative pain control and spinal stability. Determining the most appropriate muscle dissection technique is critical to reduce damage [5].

A dose-response relationship has been established between surgical invasiveness and increased creatine kinase (CK) levels [5–7]. Considering this situation, this retrospective study aimed to compare monopolar electrocauterization and blunt dissection surgery in terms of muscle damage (measured by serum CK and lactate dehydrogenase levels [LDH]), inflammation (measured by C-reactive protein [CRP] levels), and intraoperative bleeding (measured by hemoglobin levels) in 72 patients undergoing lumbar microdiscectomy.

Material and Methods

ETHICAL APPROVAL:

This retrospective study was conducted with the approval of the Ordu University Clinical Research Ethics Committee (approval No. 2023/299). Written informed consent for the use of their data in academic publications was obtained from all patients included in the study. The study is based on a retrospective analysis of postoperative laboratory data from patients who underwent microdiscectomy between 2021 and 2023. Patient data was anonymized and de-identified prior to analysis to ensure confidentiality and compliance with ethical guidelines.

INCLUSION AND EXCLUSION CRITERIA:

Only patients diagnosed with single-level lumbar disc herniation who underwent microdiscectomy and had complete postoperative laboratory records were included in the study. Patients with a body mass index (BMI) below 18 or above 30, history of recurrent disc herniation, requiring instrumentation, and with a history of cardiac disease, malignancy, neuromuscular disorders, or hematologic diseases were excluded from the study.

DATA COLLECTION AND LABORATORY PARAMETERS:

Blood samples for complete blood count (CBC), biochemical, and coagulation tests were collected from the patients 24 h before surgery and 1 h and 24 h after surgery. In the biochemical analyses, CK, LDH, and CRP levels were evaluated, while coagulation parameters included the international normalized ratio (INR), prothrombin time (PT), and activated partial thromboplastin time (APTT) (Table 1).

GROUP ALLOCATION:

In the study, group A consisted of patients who underwent dissection using a monopolar electrocautery, whereas group B included patients who underwent blunt dissection using a scalpel, Metzenbaum surgical scissors, and a periosteal elevator. For group allocation, cases performed by 2 surgeons who routinely applied 1 of the 2 dissection techniques were included in the study. Each surgery within a group was performed by a single surgeon who consistently used the respective technique as part of their standard clinical practice. Thus, the differences between the techniques were objectively evaluated without requiring the surgeons to deviate from their routine practices.

STATISTICAL ANALYSIS:

All statistical analyses were conducted using MedCalc Statistical Software (version 20.009; Ostend, Belgium). Categorical variables were summarized as frequencies and percentages. Numerical variables were expressed as mean±standard deviation for normally distributed data, and as median with interquartile range (IQR) for non-normally distributed data.

The normality of data distribution was assessed using the Shapiro-Wilk test. Additionally, Q-Q plots were used to visually evaluate the distribution of numerical variables.

Group comparisons for categorical variables were performed using the chi-square test. For numerical variables, the independent samples t test was applied when the data were normally distributed, whereas the Mann-Whitney U test was used for non-normally distributed variables.

For repeated measurements (1 h before surgery and 1 and 24 h after surgery), repeated measures ANOVA was used for data with normal distribution. When the normality assumption was not met, the Friedman test was applied. In cases in which significant differences were detected, post hoc pairwise comparisons were performed with Bonferroni correction to control for type I error.

All results were graphically illustrated using box-and-whisker plots. A P value of less than 0.05 was considered statistically significant.

SURGICAL TECHNIQUE:

All patients were positioned in the prone position with the surgical incision site placed in 30° flexion, and the procedures were performed under intrathecal general anesthesia. During positioning, gel positioning cushions were placed medially to support the iliac crests, while gel positioning pads were placed under the knees and feet to ensure proper alignment and reduce pressure points. After determining the surgical level under fluoroscopy, a 3-cm midline skin incision was made, which was then extended unilaterally on the side of the disc herniation, resulting in a total incision length of 5 cm. The lumbar fascia was opened unilaterally, and the paravertebral muscles were retracted laterally. Fascia and muscle dissection were performed using monopolar electrocautery in 36 patients and scissors with the blunt dissection technique in 36 patients.

In the group where monopolar electrocautery was used, the lumbar fascia was incised with electrocautery, and the multifidus muscle was dissected along the spinous processes, lamina, and facet joints using electrocautery (group A). In the blunt dissection group, the lumbar fascia was opened with a 1-cm vertical incision using a scalpel, then extended 5 cm in the cranio-caudal direction with Metzenbaum scissors. The multifidus muscle was separated along the spinous processes, lamina, and facet joints using blunt dissection with a Langenbeck periosteal elevator and gauze (group B). Muscle retraction was achieved using the same size Meyerding self-retaining retractor in all cases.

After the surgical level was confirmed using fluoroscopy, the surgical procedure was performed using 3-mm and 4-mm Kerrison rongeurs under a microscope (Leica ProVido, Germany) in accordance with the literature, preserving the facet capsule and including half of both the upper and lower lamina. After exposing the ligamentum flavum, the dura was seen by dissection and protected with an elevator, and the nerve root was observed. After the safe disc excision and decompression of the nerve roots was confirmed, the wound was closed in layers using the same type of suture material in all patients. The patients were mobilized 6 h after surgery [8].

Results

A total of 72 patients were included in the study, of whom 38 were women and 34 were men. The mean age of patients in group A was 47.69 years, while in group B, it was 45.51 years. In patients who underwent single-level lumbar microdiscectomy, thoracolumbar fascia incisions and muscle dissections were performed using monopolar electrocautery in 36 patients (group A), while a scalpel, Metzenbaum scissors, and the blunt dissection technique were used in 36 patients (group B).

In group A, the median CK value obtained from preoperative blood samples was 80.5, whereas in group B, this value was 112. At 1 h after surgery, the mean CK level was measured as 128.5 in group A and 138.5 in group B. By 24 h after surgery, the mean CK level increased to 177 in group A, while it reached 313 in group B. On day 1 after surgery, CK levels in group B were statistically significantly higher than those in group A (P<0.05) (Figures 1, 2).

Regarding LDH levels, the preoperative median value was 200 in group A and 179 in group B. At 1 h after surgery, the mean LDH level was 162 in group A and 149 in group B. At 24 h after surgery, the LDH level was 158 in group A and 160 in group B. No statistically significant difference was found between the 1 h postoperative (P=0.076) and 24-h postoperative (P=0.879) measurements (Figures 3, 4).

When CRP levels were evaluated, the preoperative median value was 0.98 for group A and 0.73 for group B. At 1 h after surgery, the mean CRP level increased to 2.2 in group A, while it was 0.66 in group B. At 24 h after surgery, the mean CRP level was 7.4 in group A and 4.81 in group B. In group A, CRP levels showed a statistically significant increase at1 h after surgery (P=0.003) (Figures 5, 6).

Regarding hemoglobin levels, the preoperative median hemoglobin value in group A was 12.65, decreasing to 11.45 at 1 h after surgery and 11.25 at 24 h after surgery. In group B, the preoperative hemoglobin level was 14.1, while at 1 h and 24 h after surgery, it was 12.65. In group A, hemoglobin levels decreased by 9.48% at 1 h after surgery and by 12.65% at 24 after surgery, compared with preoperative values. In group B, this decrease was 14.1% at 1 h and 24 h after surgery (Figure 7).

Coagulation parameters were within normal limits in all patients. The mean INR, APTT, and PT values were INR 1.03, APTT 25.77, and PT 9.21 in group A, while in group B, they were INR 0.91, APTT 25.51, and PT 9.14.

Discussion

LIMITATIONS:

This study has several limitations. Since patients who underwent microdiscectomy were discharged within the first 24 h postoperatively, it was not possible to assess CK levels during the 24- to 72-h period, which is when CK typically peaks. This limitation restricts the long-term monitoring of muscle breakdown.

In addition, the study was conducted at a single center with a limited number of patients. Multicenter studies with larger sample sizes and long-term follow-up are needed to provide a more comprehensive understanding of the effects of different surgical techniques on muscle injury, inflammatory response, and clinical outcomes.

Although a significant increase in CRP levels was observed in the electrocautery group, the clinical implications of this biochemical inflammatory response were not directly assessed. Subjective clinical data, such as postoperative pain scores (eg, the visual analog scale), were not included in the study. This absence makes it difficult to interpret the effect of inflammatory markers on patient comfort and recovery.

Furthermore, the use of LDH levels to assess muscle injury presents another limitation. LDH is a nonspecific marker of general tissue damage and is not exclusive to skeletal muscle. Therefore, its reliability in evaluating surgery-related muscle injury is limited, which should be considered account when interpreting the biochemical findings of this study.

Despite these limitations, the data obtained provide important insights into the biochemical effects of electrocautery use. However, future studies incorporating more comprehensive clinical and biochemical assessments will help to strengthen the clinical relevance of such findings.

Conclusions

In our study, the effects of different dissection techniques in lumbar microdiscectomy surgery on muscle damage, inflammatory response, and intraoperative bleeding control were compared. Monopolar electrocautery was found to be associated with less muscle breakdown, compared with scalpel and blunt dissection; however, it was observed to induce a more pronounced inflammatory response. On the other hand, the lower hemoglobin loss in patients who underwent electrocautery suggests that this method provides an advantage in intraoperative bleeding control.