INTRODUCTION

Knee surgeries often involve a variety of postoperative pain management strategies, including peripheral nerve blocks, central neuraxial blocks, local anesthetic infiltration, and systemic analgesics. Among these, peripheral nerve blocks targeting the knee region have become increasingly popular because of their effectiveness in providing analgesia (1). Recently, the combination of adductor canal block (ACB) and infiltration between the popliteal artery and capsule of the knee (IPACK) block has emerged as a promising strategy (2,3).

The rationale for this study stems from the unique advantages of ACB and IPACK block. ACB selectively blocks the anterior sensation of the knee while minimizing motor loss compared with traditional femoral nerve blocks. IPACK block is a newer technique that targets sensory branches of the sciatic nerve supplying the posterior knee joint. When combined, these blocks have shown enhanced analgesia and reduced opioid consumption in knee surgeries (4). However, despite the advantages of these blocks, epidural analgesia remains the gold standard method in knee surgeries because of its effectiveness, reproducibility, and ability to reduce opioid consumption. However, its side effects, such as urinary retention, delay in mobilization, nausea, and hypotension, have led to a preference for peripheral nerve blocks.

Therefore, this study was designed to compare the analgesic efficacy of ACB + IPACK block combination with single-dose epidural analgesia in arthroscopic knee surgery. Our aim was to assess the primary outcome of analgesic efficacy at different time points (1^st, 8^th, and 24^th hours post-block administration) between the ACB + IPACK block combination and epidural analgesia. Secondary outcomes include chronic pain outcomes at the 3-month post-surgery mark, discharge times, patient mobilization times, and postoperative analgesic requirements. The hypothesis of this study was that the ACB + IPACK block combination would provide comparable or superior analgesia to epidural analgesia, with potential benefits in terms of side effects and recovery times.

METHODS

Study Design

This study was conducted as a prospective observational study.

Setting

The study was conducted between August 15, 2022, and February 15, 2023, following the approval of the University of Health Sciences Hamidiye Faculty of Medicine Ethics Committee (approval number: E-48865165-302.14.06-139413, date: 08.07.2022). This study was conducted in accordance with the Declaration of Helsinki. Informed consent forms were obtained from all patients.

Participants

The study included patients over the age of 18 years who were scheduled to undergo arthroscopic knee surgery under spinal anesthesia and who had no limitations in cooperation or orientation. Patients who did not consent to participate, were under 18 years old, were scheduled for general anesthesia, had diseases limiting cooperation, and were using more than 3 months of gabapentin, pregabalin, or opioid were excluded. In addition, patients with one or more of the following conditions were excluded from the study: previous coagulation or bleeding disorder, receiving anticoagulant therapy, allergy/sensitivity to local anesthetics and/or opioids, and infection in the procedure area.

Variables

The primary outcome compares analgesic efficacy at different time points (1^st, 8^th, and 24^th hours post-block administration) between the ACB + IPACK block combination and epidural analgesia. Secondary outcomes include chronic pain outcomes at the 3-month post-surgery mark, discharge times, patient mobilization times, and postoperative analgesic requirements.

Data Sources/Measurement

Patient data, including age, gender, American Society of Anesthesiologists physical status classification system (ASA) scores, comorbidities, postoperative visual analog scale (VAS) scores, mobilization and discharge times, VAS score at 3 months, and postoperative analgesic requirements, were recorded. The severity of pain was assessed using the VAS at the 1^st, 8^th, and 24^th h after block administration. Mobilization and discharge times were also documented. Follow-up was conducted by contacting the patients again on the 90^th day.

Bias

The study was designed to minimize potential bias by excluding patients with certain conditions and using a standardized protocol for the administration of ACB + IPACK block and epidural analgesia.

Study Size

Statistical power analysis was performed, determining a sample size of 70 patients to achieve 95% power based on similar studies. A total of 80 patients were included in the study, with 40 receiving IPACK and ACBs and 40 undergoing combine spinal epidural, after excluding case losses.

Quantitative Variables

Quantitative variables such as age, ASA scores, postoperative VAS scores, mobilization and discharge times, and VAS score at 3 months were recorded and analyzed.

Statistical Analysis

Data analysis was performed using Python version 3.9.12 and the SciPy package. The Shapiro-Wilk test was used to assess data distribution. Chi-square and Fisher’s exact tests were employed for categorical data, independent t-tests for parametric data, and Mann-Whitney U tests for non-parametric data. Statistical significance was set at p<0.05.

RESULTS

Participants

A total of 90 patients who underwent arthroscopic knee surgery under regional anesthesia between August 15, 2022, and February 15, 2023 were initially included in this study. However, ten patients were excluded at different stages because of incomplete data and the procedure being changed to general anesthesia. Therefore, the final analysis was conducted on 80 patients who were divided into two groups based on the chosen method for postoperative analgesia: IPACK and ACB (group 1) and epidural analgesia (group 2) (Figure 1).

Descriptive Data

Demographic characteristics, including age, gender, and ASA scores, were comparable between the two groups, with no significant differences observed. In group 1 (IPACK and ACB), the mean age was 50.1 years, whereas in group 2 (epidural analgesia), it was 49.4 years. The gender distribution in group 1 comprised 18 males and 22 females, whereas in group 2, there were 21 males and 19 females. Regarding the ASA scores, group 1 included 11 ASA I, 24 ASA II, and 5 ASA III patients, whereas group 2 comprised 14 ASA I, 23 ASA II, and 3 ASA III patients. In terms of comorbidities, group 1 had 32 patients with additional diseases and 12 patients without any additional disease, whereas group 2 had 29 patients with additional diseases and 11 patients without any additional disease. All demographic data are presented in Table 1.

Outcome Data

Comparison of postoperative pain scores between the two groups revealed that the block group (group 1) provided equally effective postoperative analgesia as the epidural group (group 2) at the 8^th and 24^th hours (p>0.05). However, at the 1^st hour, the combined spinal epidural group (group 2) provided more effective analgesia than the block group (p=0.021). The mean 1st hour VAS score in group 1 was 2.12±0.76, significantly higher than the score of 1.64±0.62 in group 2 (p=0.021). No significant differences were found in the 8th hour (group 1: 2.17±0.88, group 2: 1.92±0.74) and 24^th hour (group 1: 2.49±1.04, group 2: 2.24±0.94) VAS scores. The VAS scores of the patients at the 1^st, 8^th, and 24^th h are presented in Table 2. Regarding mobilization time, the patients in group 1 had a significantly shorter duration of 1.16 days than the patients in group 2, whose mobilization time was 1.68 days (p=0.037). However, there was no significant difference in discharge times between the two groups, with group 1 having a mean discharge time of 2.24 days and group 2 having a mean discharge time of 2.4 days (p=0.33).

Main Results

If the patient failed to tolerate pain, 1000 mg paracetamol and 100 mg contramal as rescue analgesia were administered. Rescue analgesia was required in 5 patients in both groups, and no significant difference was detected (p>0.999). To evaluate chronic pain at 3 months, VAS scores were assessed for all 80 patients in the study. The mean VAS score in group 1 was 1.22, whereas it was 1.16 in group 2. No significant difference was observed between the two groups in terms of this parameter (p=0.1).

DISCUSSION

The most important finding of this study was that both IPACK, ACB, and epidural analgesia demonstrated comparable efficacy in providing pain relief in arthroscopic knee surgery patients. The block group showed comparable postoperative analgesia to the epidural group at the 8^th and 24^th h, whereas the combined spinal epidural group provided more effective analgesia at the 1^st h. Additionally, the block group was associated with shorter mobilization times than the epidural group. No significant differences were found in discharge times or chronic pain at 3 months between the two groups.

Peripheral nerve blocks have become increasingly favored in recent years because of the advancements in ultrasound-guided techniques and their proven effectiveness in providing targeted pain relief. In knee surgeries, the combination of femoral nerve block or ACB with subgluteal sciatic block, popliteal sciatic block, or IPACK block has been identified to provide superior pain relief because of the comprehensive sensory innervation of the knee region (5).

IPACK block, which targets the sensory articular branches of the sciatic nerve that innervate the posterior knee joint, has emerged as an effective technique for alleviating posterior knee joint pain. When combined with the ACB, it enhances postoperative pain relief and reduces opioid consumption compared with the ACB alone (6,7). Studies have also reported comparable efficacy between the IPACK block and the genicular nerve block, another peripheral nerve block for posterior sensory block of the knee (8). Moreover, surgeons have achieved similar results to the combination of IPACK and ACB through periarticular local anesthetic infiltration on the posterior part of the knee (9).

The use of peripheral nerve blocks and local anesthetic infiltration in knee surgeries achieves effective postoperative pain relief with minimal motor block. This approach is particularly advantageous considering the undesirable side effects of opioids, such as nausea, vomiting, and constipation (10-12). In addition to reducing opioid consumption, IPACK block and ACB have demonstrated effective postoperative pain relief for knee surgeries, aligning with the principles of multimodal pain control (7,10).

In terms of patient mobilization and discharge, continuous peripheral nerve blocks have been associated with longer durations than single-dose blocks (13,14). However, it has been observed that ACB catheters, which aim to minimize motor loss, facilitate earlier mobilization and discharge compared with femoral nerve catheters (15). The duration of hospitalization and mobilization times were shortened in the IPACK block group compared with that in the epidural analgesia group (16,17). Another study comparing subgluteal sciatic nerve block + femoral nerve block with ACB + IPACK block found that the IPACK group exhibited better early motor function (18).

Postoperative chronic pain is a significant concern in knee surgeries, affecting approximately 10% of patients and increasing to 20% in some cases (19,20). Epidural analgesia has been widely recognized as an effective method for preventing chronic pain by providing successful perioperative analgesia control (17).
The efficacy of IPACK block in preventing chronic pain is still limited, with few studies available (11). However, our study found that ACB + IPACK block was as effective as epidural analgesia in preventing chronic pain.

In addition to knee surgeries, the versatility of IPACK block is evident in other clinical applications such as algology and perioperative analgesia, as well as in procedures such as radiofrequency ablation (21,22). Emerging techniques such as the IPACK block and saphenous, peroneal, accessory obturator, nerve to vastus medialis, and articular branch of the obturator nerve (SPANK) block have expanded the options for sensory blockade in the lower extremities (23).

Study Limitations

This study has several limitations that should be considered. The lack of randomization and the potential for confounding factors should be considered when interpreting the results. The only criterion for mobilization time was the patient’s ability to get out of bed and walk. The VAS score was used to define chronic pain. Symptoms such as paresthesia, burning, and stinging were not questioned. The volume of local anesthetic used for the block may not be standardized because of the lack of a minimum effective concentration for the IPACK block.

CONCLUSION

In conclusion, this study found that IPACK, ACB, and epidural analgesia demonstrated comparable efficacy in providing pain relief in arthroscopic knee surgery patients. The block group showed comparable postoperative analgesia to the epidural group at the 8^th and 24^th h, whereas the combined spinal epidural group provided more effective analgesia at the 1^st h. Additionally, the block group was associated with shorter mobilization times than the epidural group. No significant differences were found in discharge times or chronic pain at 3 months between the two groups. Further randomized controlled trials are needed to confirm these findings.

Ethics

Ethics Committee Approval: The study was conducted between August 15, 2022, and February 15, 2023, following the approval of the University of Health Sciences Turkey, Hamidiye Faculty of Medicine Ethics Committee (approval number: E-48865165-302.14.06-139413, date: 08.07.2022).

Informed Consent: Obtained.

Authorship Contributions

Surgical and Medical Practices: R.O.K., A.T.K., H.K., Concept: R.O.K., A.T.K., H.K., Design: R.O.K., A.T.K., H.K., Data Collection or Processing: R.O.K., A.T.K., H.K., Analysis or Interpretation: E.A.T., Literature Search: R.O.K., A.T.K., H.K., Writing: R.O.K., A.T.K., H.K.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.