Surgery for the knee joints is a commonly performed orthopedic procedure that restore the function and relieves the pain. With the TKR (total knee replacement) procedure, the volume is considered to attain 3.46 million by 2030 for every year. Postoperative pain felt after the surgery of the knee joint is still a challenge and significant concern which has been associated with reduced patient satisfaction, chronic pain development, prolonged hospital stay, and delayed movements. Despite various advances reported with multimodal analgesia, more than 50% of the subjects that undergo knee joint procedure report continuous moderate to severe pain in immediate postoperative time.¹

Traditional regional anesthesia procedures such as adductor canal block (ACB) and FNB (femoral nerve block) provides an effective analgesia in anterior knee, however, it does not provide adequate analgesia in pain from the posterior knee. Also, femoral nerve block has been linked to weakness in quadriceps which can increase the risk for fall and can delay the early mobilization.²

The space between posterior knee capsule (iPACK) block and popliteal artery has selectiee target which is terminal articular branches of the tibial nerve that supplies the posterior capsule of the knee and preserve its motor functions. Despite earlier literature reporting analgesic advantages on the use of iPACK block as an adjunct therapy, recent data is scarce concerning its evaluation of additive efficacy within a combined spinal-epidural (CSE) analgesic regimen.³ 

This highlights the need for conduction of further prospective studies to assess the efficacy of iPACK block under ultrasound guidance concerning the postoperative analgesia duration in subject candidate for knee joint surgery using CSE.⁴ Hence, the present study was aimed to evaluate the analgesic effect of iPACK block in subjects undergoing knee joint surgeries in combined spinal epidural (CSE) Anesthesia.

The present prospective, randomized, controlled clinical study was aimed to evaluate the analgesic effect of iPACK block in subjects undergoing knee joint surgeries in combined spinal epidural (CSE) Anesthesia. The study subjects were from Department of Anesthesia of the Institute. Verbal and written informed consent were taken from all the subjects before study participation. The present study assessed 100 subjects from ASA status I and II that were undergoing elective knee joint surgery under combined spinal epidural anesthesia and were divided into two groups of 50 subjects each where Group I was given an ultrasound-guided iPACK block with 20 mL of 0.2% ropivacaine and Group II subjects were given 20 ml of normal saline. The exclusion criteria for the study were subjects with contraindication to neuraxial anaesthesia, pre-existing neurological disorders affecting the lower limb, body mass index >40 kg/m², chronic opioid use (defined as regular use for >3 months), coagulopathy, local infection at the injection site, known allergy to local anaesthetics, and subjects that refused the participation. All the includes subjects were given standard and combined spinal epidural anaesthesia at the L3–L4 interspace under aseptic protocol. Spinal anesthesia was given using 2.5 mL (12.5 mg) of 0.5% hyperbaric bupivacaine followed by insertion of the epidural catheter for postoperative analgesia. After the surgical procedure completion and under effect of spinal anesthesia, subjects were placed in supine position with slightly flexed knee using a support. Under asepsis, an ultrasound-guided iPACK block was given and low-frequency transducer was placed transversally in popliteal fossa for identification of posterior femoral condyle/capsule and popliteal artery. With in-plane technique, 80mm block needle which was 22 gauge was advanced in fascial plane in between popliteal artery and popliteal artery. After ensuring the negative aspiration, Group I (control) was given 20 mL of normal saline (placebo) and Group I was given 20 mL of 0.2% ropivacaine which was incrementally injected with intermittent aspiration. Postoperative analgesia was given using epidural catheter and5 mL boluses of 0.1% ropivacaine in cases with NRS (Numerical Rating Scale) scores of ≥4 with 15 minutes of lockout interval. The primary outcome assessed was postoperative analgesia duration which was time from completion of iPACK block injection to the first request for rescue analgesia (NRS ≥4) and secondary outcome assessed was hemodynamic changes, number of epidural boluses, Numerical Rating Scale (NRS) pain scores, and time to first rescue analgesia. The gathered data was statistically analyzed with statistical tests that included chi-square test, Fisher’s exact test, Mann Whitney U test, and SPSS (Statistical Package for the Social Sciences) software version 24.0 (IBM Corp., Armonk. NY, USA) using ANOVA, chi-square test, and student's t-test. The significance level was considered at a p-value of <0.05.

The present prospective, randomized, controlled clinical study was aimed to evaluate the analgesic effect of iPACK block in subjects undergoing knee joint surgeries in combined spinal epidural (CSE) Anesthesia. The present study assessed 100 subjects from ASA status I and II that were undergoing elective knee joint surgery under combined spinal epidural anesthesia and were divided into two groups of 50 subjects each where Group I was given an ultrasound-guided iPACK block with 20 mL of 0.2% ropivacaine and Group II subjects were given 20 ml of normal saline. The primary outcome assessed was postoperative analgesia duration and secondary outcome assessed was hemodynamic changes, number of epidural boluses, Numerical Rating Scale (NRS) pain scores, and time to first rescue analgesia.

It was seen that for the baseline and intraoperative characteristics in two groups of study subjects, the mean age of the study subjects in placebo and iPACK groups were statistically comparable with p=0.16. Similar non-significant difference was seen in gender distribution, ASA status, and mean BMI of study subjects with p-values of 0.75, 0.76, and 0.53 respectively. The diagnosis was grade 4 osteoarthritis, meniscus tear, and others in 72% (n=36), 16% (n=8), and 12% (n=6) subjects from placebo group and in 68% (n=340, 8% (n=4), and 24% (n=12) subjects from iPACK group respectively. Peak sensory level was T6, T8, and T10 in 40% (n=20), 44% (n=22), and 16% (n=8) subjects from placebo and 28% (n=14), 56% (n=28), and 16% (n=8) study subjects. The mean surgery duration in placebo and iPACK groups was statistically comparable with p=0.475. Similar non-significant difference was seen for motor block duration with p=0.547 (Table 1).

The study results showed that for postoperative analgesic outcomes in study subjects, duration of analgesia was significantly higher in iPACK group compared to placebo group with p<0.001. Mean epidural boluses were significantly higher in placebo group at 0-12 and 0-24 hours and was comparable in two groups at 24-48 hours with respective p-values of <0.001, <0.001, and 0.208. Mean NRS scores were 0 in two groups at immediate and 30 minutes with scores of 0, whereas, at 60 and 240 minutes, scores were 0 in iPACK group which were significantly lower with p<0.001 (Table 2).

It was also seen that time for first rescue analgesia was significantly different between groups where analgesia was needed in iPACK group after 60-240 minutes of surgery, whereas in control group, it was needed in 360-480 minutes. The consumption of bolus in 28-48 hours was comparable in the two groups. For hemodynamic parameters such as mean arterial pressure and heart rate were comparable and stable in the two groups at all the assessment times. The postoperative complications showed a non-significant intergroup difference with p>0.05.

Table 1: Baseline and intraoperative characteristics in two groups of study subjects

Table 2: Postoperative analgesic outcomes in two groups of study subjects

The present study assessed 100 subjects from ASA status I and II that were undergoing elective knee joint surgery under combined spinal epidural anesthesia and were divided into two groups of 50 subjects each where Group I was given an ultrasound-guided iPACK block with 20 mL of 0.2% ropivacaine and Group II subjects were given 20 ml of normal saline. The primary outcome assessed was postoperative analgesia duration and secondary outcome assessed was hemodynamic changes, number of epidural boluses, Numerical Rating Scale (NRS) pain scores, and time to first rescue analgesia. This was in line with the previous studies of Raghunath SS et al5 in 2026 and Bhasin S et al6 in 2018 where study design used by the authors was similar to the design of the present study.

The study results showed that for the baseline and intraoperative characteristics in two groups of study subjects, the mean age of the study subjects in placebo and iPACK groups were statistically comparable with p=0.16. Similar non-significant difference was seen in gender distribution, ASA status, and mean BMI of study subjects with p-values of 0.75, 0.76, and 0.53 respectively. The diagnosis was grade 4 osteoarthritis, meniscus tear, and others in 72% (n=36), 16% (n=8), and 12% (n=6) subjects from placebo group and in 68% (n=340, 8% (n=4), and 24% (n=12) subjects from iPACK group respectively. Peak sensory level was T6, T8, and T10 in 40% (n=20), 44% (n=22), and 16% (n=8) subjects from placebo and 28% (n=14), 56% (n=28), and 16% (n=8) study subjects. The mean surgery duration in placebo and iPACK groups was statistically comparable with p=0.475. Similar non-significant difference was seen for motor block duration with p=0.547. These results were consistent with the findings of Govender-Davies S et al7 in 2024 and Thobhani S et al8 in 2017 where authors in their studies also assessed subjects with comparable demographic and clinical data and undergoing knee surgeries.

It was seen that for postoperative analgesic outcomes in study subjects, duration of analgesia was significantly higher in iPACK group compared to placebo group with p<0.001. Mean epidural boluses were significantly higher in placebo group at 0-12 and 0-24 hours and was comparable in two groups at 24-48 hours with respective p-values of <0.001, <0.001, and 0.208. Mean NRS scores were 0 in two groups at immediate and 30 minutes with scores of 0, whereas, at 60 and 240 minutes, scores were 0 in iPACK group which were significantly lower with p<0.001. These findings were in agreement with the results of Narejo et al9 in 2021 and Kampitak W et al10 in 2019 where results reported by the authors for postoperative analgesic outcomes were comparable to the results of the present study.

The study results also showed that the time for first rescue analgesia was significantly different between groups where analgesia was needed in iPACK group after 60-240 minutes of surgery, whereas in control group, it was needed in 360-480 minutes. The consumption of bolus in 28-48 hours was comparable in the two groups. For hemodynamic parameters such as mean arterial pressure and heart rate were comparable and stable in the two groups at all the assessment times. The postoperative complications showed a non-significant intergroup difference with p>0.05. These results correlated with the findings of Roy R et al11 in 2024 and Tang X et al12 in 2022 where results similar to the present study for first rescue analgesia and consumption of bolus were also reported by the authors in their studies.

Considering its limitations, the present study concludes that there is a significant reduction in the need for rescue analgesia and increased postoperative analgesia in subjects undergoing knee joint surgery using the under ultrasound-guided iPACK block in combination with spinal-epidural anesthesia proving it as an efficacious modality.

1. Zhao C, Liao Q, Yang D, Yang M, Xu P. Advances in perioperative pain management for total knee arthroplasty: a review of multimodal analgesic approaches. J Orthop Surg Res. 2024;19:843.
2. Abdelghaffar MR, Nemr MM, Mabrouk MH, Elgendy HMA, Abdulmageed AM. Analgesic effect of adductor canal block with or without IPACK block after total knee arthroplasty: a comparative study. Anaesth Pain Intensive Care. 2025;29:242– 7.
3. Ma HH, Kan SA, Chiu FY, Su YP. A novel technique of intraoperative infiltration between posterior capsule and popliteal artery can reduce opioid consumption and blood loss in total knee arthroplasty surgery: an age- and gender-matched study. J Orthop Surg Res. 2025;20:205.
4. Wang Q, Hu J, Cai L, Bahete A, Yang J, Kang P. Minimum effective concentration of ropivacaine for ultrasound-guided adductor canal + IPACK block in total knee arthroplasty. J Orthop Surg (Hong Kong). 2022;30:10225536221122339.
5. Raghunath SS, Nizamuddeen BM, Devaraj IC, Patil SM. Analgesic efficacy of the iPACK block in knee joint surgeries under combined spinal-epidural anaesthesia: A randomized controlled trial. Indian J Clin Anaesth. 2026;13:316–321.
6. Bhasin S, Dhar M, Sreevastava DK, Nair R, Chandrakar S. Comparison of Efficacy of Epidural Ropivacaine versus Bupivacaine for Postoperative Pain Relief in Total Knee Replacement Surgeries. Anesth Essays Res. 2018;12:26–30.
7. Govender-Davies S, Davies L, Pillay-Addinall S. A cadaveric study investigating the spread of injectate following an interspace between the popliteal artery and the capsule of the posterior knee block in a neonatal sample: a pilot study. Anat Cell Biol. 2024;57:229–37.
8. Thobhani S, Scalercio L, Elliott CE, Nossaman BD, Thomas LC, Yuratich D, et al. Novel Regional Techniques for Total Knee Arthroplasty Promote Reduced Hospital Length of Stay: An Analysis of 106 Patients. Ochsner J. 2017;17:233–8.
9. Narejo AS, Abdulwahab F, Aqil M, Alsubaie AT, Hazazy HY, Alzahrani T, et al. Efficacy of interspace between the popliteal artery and the capsule of the posterior knee (iPACK) block versus periarticular local infiltration analgesia after unilateral total knee arthroplasty: Prospective randomized control trial. Saudi Med J. 2021;42:1065–71
10. Kampitak W, Tansatit T, Tanavalee A, Ngarmukos S. Optimal injection site for IPACK block for posterior knee pain after total knee arthroplasty: an anatomical and clinical study. Korean J Anesthesiol. 2019;72:486–94
11. Roy R, Agarwal G, Ahuja P, Mohta A. Adductor canal block (ACB) plus infiltration of the posterior capsule of the knee (iPACK) block versus 4-in-1 block in an arthroscopic anterior cruciate ligament (ACL) repair: A randomised study. Indian J Anaesth. 2024;68:959–64.
12. Tang X, Jiang X, Lei L, Zhu W, Fu Z, Wang D, Chen J, Ning N, Zhou Z. IPACK (Interspace between the Popliteal Artery and the Capsule of the Posterior Knee) Block Combined with SACB (Single Adductor Canal Block) Versus SACB for Analgesia after Total Knee Arthroplasty. Orthop Surg. 2022;14:2809–21.