Abstract
Background and Aims:
Distal motor-sparing nerve blocks are increasingly popular for knee arthroplasty pain. Genicular nerve ablation, initially proposed for knee osteoarthritis, is also currently used for postoperative pain management. We hypothesised that superior postoperative analgesia can be achieved by combining genicular nerve block with adductor canal block (ACB) by reducing 24-hour opioid consumption.
Methods:
Fifty patients were assigned to Group I (ultrasound-guided ACB with 20 mL of 0.25% ropivacaine and 4 mg dexamethasone and ultrasound-guided superomedial (SM), superolateral (SL), and inferomedial (IM) GNB with 5 mL of 0.25% ropivacaine and 2 mg of dexamethasone at each location and Group II (ultrasound-guided ACB with 20 mL of 0.25% ropivacaine, 4 mg dexamethasone, and ultrasound-guided three-location GNB with 15 mL of 0.9% saline). The outcomes measured were 24-hour morphine consumption, pain scores over 24 hours, and the time to rescue analgesia. The continuous data were analysed using an unpaired t-test or the Mann-Whitney U test, and the Chi-square test was used to analyse the categorical variables.
Results:
The mean total consumption of morphine (mg) was 5.96 [standard deviation (SD): 2.73] in Group I and 15.52 (SD: 2.67) in Group II, with a mean difference of 9.56 [95% confidence interval (CI): -4.66, −2.39] (P < 0.001, Cohen’s d = 3.54). In Group II, the mean time for first rescue analgesia was 20.73 (SD: 7.28) hours, whereas it was 24.00 (SD: 0.00) hours in Group I, with a mean difference of −3.27 (95% CI: −11.33, 4.783) (P = 0.034, Cohen’s d = 0.45). Pain severity at rest was substantially lower in Group I at 6 hours (P = 0.020), 12 hours (P = 0.003), and 24 hours (P = 0.002). Pain score with movement in Group I was considerably lower at 6 hours (P = 0.008) and 12 hours (P < 0.001).
Conclusion:
Combining genicular block with ACB provided superior postoperative analgesia and reduced opioid consumption compared to ACB alone.
Keywords: Adductor canal block, analgesia, genicular nerve block, knee osteoarthritis, knee, nerve block, pain, postoperative pain, regional anaesthesia, total knee arthroplasty, ultrasound
INTRODUCTION
Knee osteoarthritis (OA) is a significant musculoskeletal chronic pain problem, and its prevalence is on the rise among the elderly population.[1] When conventional conservative treatments fail and patients develop knee deformity due to OA, total knee arthroplasty (TKA) is recommended.[2] TKA is associated with severe pain during the postoperative period.[3] Untreated severe postoperative pain can lead to delayed ambulation and unwillingness to participate in physical therapy. Furthermore, after TKA, if pain is not managed adequately, then there is a likelihood that acute pain can translate into chronic persistent pain.[4]
In recent years, multimodal analgesia combined with regional nerve block has been the norm in managing postoperative pain in TKA owing to superior analgesia and opioid-sparing benefits. Regional blocks, notably femoral nerve or adductor canal blocks (ACB), have been used extensively for TKA. Despite the extensive use of ACB, even in the first or second postoperative day, most patients still experience moderate-intensity pain on activity, indicating that additional regional anaesthesia (RA) techniques may provide better pain relief.[5]
Recent cadaveric studies have extensively looked into knee joint innervations and prospective targets for pain-carrying articular branches of the knee joint, many of which are not typically covered in the traditional ACB.[6,7] To cover other genicular nerves (GNs) and branches innervating the knee joint, an additional genicular nerve block (GNB) may provide better analgesia.[8,9]
Research on GNB for acute pain in TKA is limited, even though radiofrequency ablation targeting GN has been extensively studied in OA knees.[10] We conducted this trial to test the hypothesis that performing GNB in addition to routine ACB will reduce 24-hour opioid consumption and provide better postoperative analgesia. The primary objective was to find out the total opioid consumption in the initial 24 hours between the two groups. The secondary objectives were to determine postoperative pain scores, time interval to first rescue analgesic demand, patient satisfaction scores, and adverse effects.
METHODS
The study was approved by the Institutional Ethics Committee of the Kalinga Institute of Medical Sciences (vide approval number: KIIT/KIMS/IEC/970/2022, dated 18/07/2022) and registered with the Clinical Trials Registry-India (CTRI/2022/11/045333, https://www.ctri.nic.in). The protocol followed the 2013 Helsinki Declaration and Good Clinical Practice guidelines. This research was conducted at a tertiary care hospital from December 2022 to March 2024. Written informed consent was obtained from each subject to participate in the study and use the patient data for research and educational purposes.
Fifty patients with the American Society of Anesthesiologists (ASA) physical status I–III and knee OA, planned for unilateral primary TKA under spinal anaesthesia (SA), were recruited. The patients with contraindication to SA or peripheral nerve blocks (PNB), use of opioids for chronic pain, history of psychiatric illness, prior ipsilateral knee surgery or trauma, bilateral or revision TKA, and severe cardiovascular and renal disease were excluded from recruitment.
An unbiased researcher with no role in interventions or assessments performed the randomisation and concealment process. Patients were randomised into two groups using computer-generated codes. The researcher, who performed all the evaluations, and the subjects were unaware of the randomisation. The allocation sequence was done with sequentially numbered, sealed, opaque envelopes for assignment lists. Each envelope was opened only after the participant consented to join the study, ensuring the allocation was concealed until the point of assignment. Before the block, the interventionist opened the concealed envelope and revealed the patient’s treatment allocation. The drug was prepared by a nurse unaware of the study allocation or evaluation process. The nurse and anaesthesiologist in charge of the case were the only ones who knew about the procedure. A different anaesthesiologist, blinded to the group allocation and interventions, collected postoperative data.
Group I received ultrasound-guided ACB with 20 mL of 0.25% ropivacaine and 4 mg dexamethasone and ultrasound-guided superomedial (SM), superolateral (SL), and inferomedial (IM) GNB with 5 mL of 0.25% ropivacaine and 2 mg of dexamethasone at each location (total of 15 mL and 6 mg dexamethasone). Group II received ultrasound-guided ACB with 20 mL of 0.25% ropivacaine, 4 mg dexamethasone, and ultrasound-guided three-location GNB with 15 mL of 0.9% saline.
Following intravenous (IV) access and routine monitoring, one experienced anaesthesiologist performed all blocks. The IM, SL, and SM GNs were blocked using real-time ultrasound guidance (M Turbo, FUJIFORM Sonosite Edge II, Inc., USA) with a linear high-frequency (6–13 MHz) probe. We used a 20-G 50-mm block needle (Stimuplex Ultra 360, B Braun Melsungen, Germany) that was inserted in-plane from anterior to posterior, targeting the middle of the anteroposterior width of the femur (for SM and SL GN) and tibia (for IM GN). Injectate spread across the bone surface was observed with real-time ultrasound [Figure 1a]. For ACB, the block needle was advanced from lateral to medial by using an in-plane approach at the mid-point of the adductor canal. Local anaesthetic (LA) was injected after piercing the vasto-adductor membrane. The spread was observed at approximately the 9-11 o’clock location of the superficial femoral artery on the right side and the 1-3 o’clock position on the left side [Figure 1b].
Figure 1.
(a) Transverse (short-axis) sono-anatomy for superomedial genicular nerve block (SMGNB) at the shaft condyle junction. The bold blue arrows indicate the posterior-to-anterior block needle direction, and LA is deposited at the top of the periosteum. VAS Med = Vastus Medialis; ANT = Anterior; LA = Local Anaesthetic. (b) Sono-anatomy adductor canal block (ACB). The bold blue arrows indicate the needle path, and the red arrow indicates the spread of LA around the saphenous nerve. MED = Medial; ART = Superficial Femoral Artery; VM = Vastus Medialis; LA = Local Anaesthetic
Patients received oral paracetamol (1 g) and celecoxib (200 mg) 2 hours before surgery. The visual analogue scale (VAS) pain scale of 0–10 (0 = no pain and 10 = worst imaginable pain) was explained to the subjects. Additionally, they were shown a patient-controlled analgesia (PCA) pump and how to use it, and they were asked to inform the nurse whenever VAS ≥4. For postoperative pain management, we used a CADD PCA pump (CADD LEGACY® PCA, Smith Medical, CA, USA). Every participant received SA with 12–15 mg of hyperbaric 0.5% bupivacaine. Supplemental analgesia was provided with IV paracetamol 1 g and IV diclofenac 75 mg at the end of surgery. Postoperative pain relief was provided with paracetamol 1 g IV every 8 hours, and diclofenac 75 mg IV 12-hourly. Pain was assessed at arrival in the preoperative area before the block (baseline) and at 3, 6, 12, and 24 hours post-surgery at rest and during movement (passive 15° limb lifting). PCA pump setting included a lockout interval of 10 minutes, a maximum dose of 5 mg/h (morphine 1 mg/mL), and a bolus dose of 1 mL without any background infusion.
The cumulative morphine consumption within the initial 24 hours postoperatively was the primary outcome. The secondary outcomes were time until the request for first rescue analgesia (VAS ≥ 4); VAS scores at 3, 6, 12, and 24 hours post-surgery at rest and during movement; patient satisfaction score; and adverse effects such as nausea, vomiting, and sedation (Ramsay sedation scale). The analgesic request time was measured as the interval between the performance of the block and the patient’s first PCA button press. Patient satisfaction was obtained using the 5-point Likert scale.[11]
Open-Source Epidemiologic Statistics for Public Health (developed by Emory University’s Rollins School of Public Health, www.OpenEpi.com) was used for sample size calculation. The sample size was calculated from a previous trial by Rambhia M et al.[9] Considering the opioid consumption at 24 hours, which was substantially lower in the GNB group relative to the saline group [23 (SD: 20) vs 58 (SD: 35)], with a 5% level of significance, 95% CI, and 95% power, the minimum required sample size was 19 in each group, that is, 38 in total. By taking 20% attrition, a total sample size of 50 (i.e. 25 in each group) was considered.
Statistical Package for the Social Sciences (SPSS) statistics software version 29.0 [International Business Machines Corporation (IBM Corp.), Armonk, NY, USA] was used to analyse the data statistically. Continuous data such as age, body mass index, opioid usage, and time to first analgesic were normally distributed per the Shapiro-Wilk test, described as mean (SD), and analysed using an unpaired t-test. The VAS score was non-normally distributed as per the Shapiro-Wilk test and presented as median [interquartile range (IQR)]. The statistical relevance of the variation in skewed continuous data between Group I and Group II was determined using the Mann-Whitney U test (for intergroup comparison) and Friedman ANOVA (for intragroup comparison). Categorical variables, including age group, gender, and patient satisfaction per the Likert scale and incidence of adverse events, were presented as percentages and frequencies and then compared using the Chi-square test. Statistical significance was set at P < 0.05.
RESULTS
The eligibility of 58 patients to participate in the study was assessed. The study excluded eight subjects: three declined to consent, and five failed to fulfil the inclusion criteria. Thus, 50 subjects were sequentially categorised into two groups and analysed [Figure 2]. Both groups had similar demographic data and baseline characteristics [Table 1].
Figure 2.
CONSORT flow diagram for enrolment, group allocation, follow-up, and analysis. CONSORT = Consolidated Standards of Reporting Trials; GNB = Genicular Nerve Block; ACB = Adductor Canal Block
Table 1.
Baseline demographic and pain characteristics
| Parameters | Group I (n=25) | Group II (n=25) | P |
|---|---|---|---|
| Age (years) | 60.76 (6.14) | 63.44 (7.76) | 0.190 |
| Gender (Male/Female) | 9/16 | 14/11 | 0.260 |
| BMI (kg/m2) | 28.82 (11.66) | 27.94 (10.80) | 0.769 |
| ASA Class I:II:III | 9:12:4 | 10:11:4 | 0.950 |
| Duration of surgery (min.) | 95.0 (19.6) | 90.7 (23.5) | 0.310 |
| Preoperative pain intensity (VAS) | |||
| Rest | 1 (1.0–1.0); 1–1 | 1 (1.0–1.0); 1–1 | ˃0.99 |
| Movement | 1 (1.0–2.0); 1–3 | 2 (1.0–2.0); 13 | 0.400 |
Data expressed as median [(first quartile–third quartile) (IQR)]; Range (min–max), mean (SD) and number of patients. Group I=GNB+ACB; Group II=ACB; BMI=Body mass index; ASA=American Society of Anesthesiologists physical status; VAS=Visual analogue scale; GNB=Genicular nerve block; ACB=Adductor canal block; IQR=Interquartile range; SD=Standard deviation
The VAS score of both groups decreased significantly from baseline to 24 hours postoperatively, both while resting and during movement (P < 0.001). Group I experienced substantially less pain at rest than Group II at 6 hours (P = 0.020), 12 hours (P = 0.003), and 24 hours (P = 0.002) [Table 2]. In contrast to Group II, Group I had substantially lower VAS at 6 hours (P = 0.008) and 12 hours (P < 0.001) during movement [Table 3]. Compared to Group II, Group I required delayed analgesia, the difference being statistically noteworthy. In Group II, the mean time for first rescue analgesia was 20.73 (SD: 7.28) hours, whereas it was 24.00 (SD: 0) hours in Group I, with a mean difference of −3.27 (95% CI: −11.33, 4.783) (P = 0.034, Cohen’s d = 0.45) [Table 4]. Group I had significantly less consumption of 24-hour opioids compared to Group II. The mean morphine consumption (mg) in Group I was 5.96 (SD: 2.73) versus 15.52 (SD: 2.67) in Group II, with a mean difference of 9.56 (95% CI: - 4.66, −2.39) (P ˂ 0.001, Cohen’s d = 3.54) [Table 4]. There was significantly better patient satisfaction in Group I than in Group II (P = 0.045) [Table 4]. There were two cases (8%) of sedation in Group I versus one case (4%) in Group II (P > 0.050). Group I had no PONV (0%), contrary to two cases (8%) in Group II (P = 0.490) [Table 4].
Table 2.
Comparison of pain severity concerning VAS score at rest between Group I and Group II
| Timepoint (h) | Group I (n=25) | Group II (n=25) | Standardised Test Statistic | P |
|---|---|---|---|---|
| 3 | 1 (1.0–1.0); 1–1 | 1 (1.0–1.0); 1–1 | 2.053 | >0.99 |
| 6 | 1 (1.0–1.0); 1–1 | 1 (1.0–1.5); 1–2 | 1.983 | 0.02 |
| 12 | 1 (1.0–1.0); 1–1 | 1 (1.0–2.0); 1–3 | 2.747 | 0.003 |
| 24 | 1 (1.0–1.5); 1–2 | 2 (1.0–3.0); 1–4 | 2.878 | 0.002 |
| P (Friedman ANOVA) | 0.0002 | <0.001 |
Data are expressed as median [(first quartile–third quartile) (IQR)]; Range (min–max). Group I=GNB + ACB; Group II=ACB; n=Number of patients; IQR=Interquartile range; GNB=Genicular nerve block; ACB=Adductor canal block
Table 3.
Comparison of pain severity concerning VAS score at movement between Group I and Group II
| Timepoint (h) | Group I (n=25) | Group II (n=25) | Standardised Test Statistic | P |
|---|---|---|---|---|
| 3 | 1 (1.0–1.0); 1–1 | 1 (1.0–1.0); 1–1 | 2.32 | >0.99 |
| 6 | 1 (1.0–1.0); 1–1 | 1 (1.0–2.0); 1–3 | 2.408 | 0.008 |
| 12 | 1 (1.0–1.0); 1–1 | 2 (1.0–3.0); 1–4 | 3.540 | <0.001 |
| 24 | 1 (1.0–2.5); 1–4 | 2 (1.0–3.0); 1–4 | 1.036 | 0.15 |
| P (Friedman ANOVA) | 0.0002 | <0.001 |
Data are expressed as median [(first quartile–third quartile) (IQR)]; Range (min–max). Group I=GNB+ACB; Group II=ACB; n=Number of patients, IQR=Interquartile range; GNB=Genicular nerve block; ACB=Adductor canal block
Table 4.
Characteristics of the postoperative analgesic profile, patient satisfaction scores, and postoperative adverse effects
| Parameters | Group I (n=25) | Group II (n=25) | Mean difference (95% CI) | Cohen’s d Effect size | P |
|---|---|---|---|---|---|
| 24-h morphine consumption (mg), mean (SD) | 5.96 (2.73) | 15.52 (2.67) | 9.56 (−4.66, -2.39) | 3.54 | ˂0.001 |
| Time to first request rescue analgesia (hour), mean (SD) | 24.0 (0) | 20.73 (7.28) | −3.27 (−11.33, 4.78) | 0.45 | 0.034 |
| Patient satisfaction score (n) | |||||
| Very satisfied Satisfied Neither satisfied nor dissatisfied Dissatisfied |
9 13 3 0 |
7 7 6 5 |
0.045 | ||
| Postoperative adverse effects | |||||
| PONV (n) Sedation (n) Local anaesthetic toxicity (n) Infection (n) |
0 2 0 0 |
2 1 0 0 |
0.490 ˃0.99 |
||
Data are expressed as mean (SD) and number of patients. Group I=GNB + ACB; Group II=ACB; PONV=Postoperative nausea and vomiting; GNB=Genicular nerve block; ACB=Adductor canal block; SD=Standard deviation
DISCUSSION
This study demonstrated that adding GNB to ACB provides superior postoperative analgesia in TKA. The GNB + ACB group showed considerably reduced VAS scores, longer time to initial rescue analgesia demand, and less opioid consumption than the ACB group.
Pain management following TKA has undergone a paradigm shift in the last 2–3 decades, from epidural to femoral/sciatic block, then ACB with or without iPACK (inter-space between the popliteal artery and capsule of the knee) block, periarticular infiltration (PAI), to very recent GNB. Epidural and FNB have stood the test of time with excellent pain relief, but motor blockade paved the way for more distal blocks such as ACB.[5] Recently, there has been further interest in more distal blocks targeting the articular branches of the knee, namely GNB and iPACK. Understanding the complex knee innervation is essential so that anaesthesiologists can practice the best RA technique for ever-evolving knee analgesia.
Recent cadaveric studies have extensively investigated knee joint innervations and targets for blocking articular branches of the knee joint. The femoral and sciatic nerves give rise to at least eight distinct branches that innervate the anterior knee. Among these are the articular branches emerging from the nerves to every vasti (medialis, intermedius, and lateralis), the saphenous nerve, and the four major GNs, namely SL, SM, IM, and inferolateral (IL).[6,7,12] The medial knee capsule, including the retinaculum, receives substantial input from the nerve to the vastus medialis, nerve to vastus intermedius, saphenous nerve, anterior branch of the obturator nerve, and SMGN. The SL side of the knee joint is supplied by the nerve to the vastus lateralis, nerve to vastus intermedius, and SLGN. In contrast, the IL quadrant is provided by the fibular nerve. The tibial nerve and the obturator nerve’s posterior branch supply the posterior part of the knee capsule.[6,7,12] Cadaveric studies involving the adductor canal show that only 3–4 nerves are blocked, whereas 8–10 nerves innervate the anterior knee.[6,7,13]
Our primary outcome measure of 24-hour opioid consumption was considerably less in Group I compared to Group II, resembling other studies.[9,14,15,16,17] Rambhia M et al.[9] used a 3-location GNB and compared it with a sham GNB in the other group. All patients were given iPACK, ACB infusion, and a standard oral analgesic protocol. They found that the GNB group had substantially decreased opioid consumption at 24 hours. Few case series and case reports where GNB was used in the TKA setting have demonstrated superior analgesia with reduced opioid consumption.[9,14] Akesen et al.[15] conducted a study comparing three groups involving GNB, iPACK, and control. They concluded that GNB is a promising technique that improves pain relief in the immediate and early postoperative period without motor blockade. In another study, GNB was compared with iPACK with a background of continuous ACB in both groups, and the authors found that the GNB + iPACK combination provided better analgesia and lesser morphine consumption.[16] Dündar et al.[17] found that the iPACK and control groups had substantially higher tramadol rescue values than GNB, consistent with our observations. Conversely, in the research done by Eid GM et al.[18] and Cuñat et al.,[19] the PAI group consumed less postoperative morphine over the initial 2 postoperative days than the GNB group. In our trial, both groups’ VAS scores significantly decreased on the first postoperative day. In addition, the pain was considerably less in GNB + ACB compared to ACB alone at 6, 12, and 24 hours postoperatively, concordant with previous trials where GNB was also used as an RA technique.[9,14,15,16,19]
GNB was compared with ACB in arthroscopic knee surgeries, and the authors found equivalent analgesic efficacies.[20,21,22] Recent meta-analysis and narrative review looked into the analgesic efficacy of FNB, ACB, iPACK, and GNB after TKA. GNB demonstrated the highest efficacy in pain reduction during mobilisation at 24 hours, achieving 94% effectiveness.[5,23]
Our study has a few limitations. First, our findings are in the context of the present block regimen, which includes ACB. However, when different block regimens, such as PAI, iPACK block, or a combination of various blocks, are used, it is still unclear whether GNB as a sole block would be effective in post-TKA pain control. Second, ambulation and motor strength of the quadriceps were not assessed. Finally, a smaller sample size is another limitation.
We found better postoperative analgesia when GNB was combined with ACB. However, the optimal LA volume for GNB remains to be determined. While most studies used 5 mL around each nerve, a single study used 2 mL of LA, indicating the need for further investigation. Based on the data from knee innervation and recent trials, we suggest the following RA techniques for adequate knee analgesia: ACB with GNB, or GNB can be combined with iPACK or PAI, which has been found to be effective in a few trials.[16,17,18,19] We propose further high-quality research involving large sample sizes to find the best possible solo or combination RA technique for TKA patients.
CONCLUSION
Our RCT demonstrated that the combination of genicular nerve block with adductor canal block provides better postoperative analgesia and lesser opioid consumption in the first 24 hours compared to ACB alone in patients undergoing total knee arthroplasty.
Conflicts of interest
There are no conflicts of interest.
Author’s contribution
RKS: Concept, design, definition of intellectual content, manuscript editing and manuscript review. LKS: Concept, design, literature search, manuscript preparation, manuscript editing and manuscript review. PM: Literature search, data acquisition, manuscript preparation. GCS: Design, definition of intellectual content and manuscript preparation. ASN: Definition of intellectual content, manuscript editing and manuscript review. PS: Data analysis and statistical analysis.
Study data availability
De-identified data may be requested with reasonable justification from the authors (via email to the corresponding author) and will be shared after approval, in accordance with the authors’ institution’s policy.
Disclosure of use of artificial intelligence (AI)-assistive or generative tools
The AI tools or language models (LLM) have not been utilised in the manuscript, except that software has been used for grammar corrections and references.
Declaration of use of permitted tools
Nil.
Presentation at conferences/CMEs and abstract publication
None.
Funding Statement
Nil.
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