Interfascial Spread of Injectate After Adductor Canal Injection in Fresh Human Cadavers

Comparison of Analgesic Effects of Continuous Femoral Nerve Block, Femoral Triangle Block, and Adductor Block After Total Knee Arthroplasty: A Randomized Clinical Trial

OBJECTIVES

This study aimed to compare the analgesic effects of continuous femoral nerve block (FNB), femoral triangle block (FTB), and adductor canal block (ACB) following total knee arthroplasty (TKA). The goal was to identify the most effective nerve block technique among these.

METHODS

Patients undergoing TKA were randomly assigned to 1 of 3 groups: FNB, FTB, or ACB. Nerve blocks were administered preoperatively, with catheters placed for patient-controlled nerve analgesia (PCNA). The primary end point was the Numeric Rating Scale (NRS) score at movement at 24 hours postsurgery. Secondary end points included NRS scores at rest and movement, quadriceps strength, Timed Up and Go (TUG) test performance, range of motion, effective PCNA utilization, and opioid consumption at various postsurgery time points.

RESULTS

Of the 94 valid data sets analyzed (FNB: 31, FTB: 31, ACB: 32), significant differences were observed in the primary end point (H=7.003, P =0.03). Post hoc analysis with Bonferroni correction showed that the FNB group had a significantly lower median pain score (3 [2 to 4]) compared with the ACB group (4 [3 to 5], Bonferroni-adjusted P =0.03). Regarding secondary end points, both the FNB and FTB groups had significantly lower NRS scores than the ACB group at various time points after surgery. Quadriceps strength and TUG completion were better in the FTB and ACB groups. There were no statistically significant differences among the groups for the other end points.

DISCUSSION

Continuous FTB provides postoperative analgesia comparable to FNB but with the advantage of significantly less impact on quadriceps muscle strength, a benefit not seen with FNB. Both FTB and ACB are effective in preserving quadriceps strength postoperatively.

Application of ultrasound-guided single femoral triangle and adductor canal block in arthroscopic knee surgery: a prospective, double-blind, randomized clinical study

PURPOSE

To compare the difference in analgesic effect between femoral triangle block (FTB) and adductor canal block (ACB) during arthroscopic knee surgery.

METHODS

Patients who underwent arthroscopic knee surgery were randomized preoperatively to FTB group or ACB group. For each group, 20 mL of 0.1% ropivacaine was injected.

PRIMARY OUTCOMES

The numeric rating score (NRS) at 12 h after surgery at rest and during movement.

SECONDARY OUTCOME

(1) The NRS at post anesthesia care unit (PACU) and 2, 24 h after surgery at rest and during movement; (2) The quadriceps muscle strength at PACU and 2, 12, 24 h after surgery; (3) Consumption of Rescue analgesia; (4) Incidence of adverse reactions.

RESULTS

The NRS at 12 h after surgery at rest and during movement of ACB group were higher than FTB group. Among secondary outcomes, the NRS at PACU at rest and during movement, 2 h after surgery during movement of FTB group lower than ACB group; the quadriceps muscle strength at 2 h after surgery of FTB group stronger than ACB group. After multiple linear regression model analysis, the data showed additional statistically significant reduction NRS at 24 h after surgery at rest (0.757, p = 0.037) in FTB group. Other outcomes were similar between two groups.

CONCLUSIONS

The FTB appears to provide superior pain control after knee arthroscopy than ACB, the FTB is superior to the ACB in quadriceps muscle strength at 2 h after surgery.

TRIAL REGISTRATION

The trial was registered in the Chinese Clinical Trial Registry (ChiCTR2300068765). Registration date: 28/02/2023.

Does Proximal Adductor Canal Block Provide Better Analgesic Efficacy than Distal Adductor Canal Block in Patients Undergoing Knee Arthroplasty: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

To compare the analgesic efficacy and adverse events of proximal versus distal ACB for adults undergoing knee arthroplasty, we searched PubMed, Cochrane, Web of Science, and Embase to identify all eligible randomized controlled trials (RCTs). The study quality of the RCTs was evaluated using the Cochrane risk of bias assessment tool. Heterogeneity among studies was examined by Cochrane Q test. Our primary outcomes were pain intensity at rest/during movement and morphine consumption. Statistical analyses were conducted by RevMan Software. Seven eligible studies involving 400 subjects were included in this meta-analysis with 202 participants in the proximal ACB group and 198 participants in the distal ACB group. The results demonstrated that proximal ACB provided significantly better pain relief at rest at 2 h (SMD -0.27, 95% CI -0.54 to -0.01, four trials, 222 participants, I2 = 0, p = 0.04) and 24 h (SMD -0.28, 95% CI -0.48 to -0.08, seven trials, 400 participants, I2 = 0, p = 0.006) following the surgery. We found no evidence of a difference in postoperative pain intensity at other timepoints. Furthermore, we noted no evidence of a difference in cumulative morphine consumption and occurrence of adverse events. Proximal ACB provides better pain relief and comparable adverse effects profile compared with distal ACB. The analgesic benefit offered by proximal ACB, however, did not appear to extend beyond the first 24 h. The overall evidence level was mostly low or very low, which requires more well-organized multicenter randomized trials in the future.

Adductor canal block techniques do not lead to involvement of sciatic nerve branches: a radiological cadaveric study

INTRODUCTION

Low and high volume mid-thigh (ie, distal femoral triangle) and distal adductor canal block approaches are frequently applied for knee surgical procedures. Although these techniques aim to contain the injectate within the adductor canal, spillage into the popliteal fossa has been reported. While in theory this could improve analgesia, it might also result in motor blockade due to coverage of motor branches of the sciatic nerve. This radiological cadaveric study, therefore, investigated the incidence of coverage of sciatic nerve divisions after various adductor canal block techniques.

METHODS

Eighteen fresh, unfrozen and unembalmed human cadavers were randomized to receive ultrasound-guided distal femoral triangle or distal adductor canal injections, with 2 mL or 30 mL injectate volume, on both sides (36 blocks in total). The injectate was a 1:10 dilution of contrast medium in local anesthetic. Injectate spread was assessed using whole-body CT with reconstructions in axial, sagittal and coronal planes.

RESULTS

No coverage of the sciatic nerve or its main divisions was found. The contrast mixture spread to the popliteal fossa in three of 36 nerve blocks. Contrast reached the saphenous nerve after all injections, whereas the femoral nerve was always spared.

CONCLUSIONS

Adductor canal block techniques are unlikely, even when using larger volumes, to block the sciatic nerve, or its main branches. Furthermore, injectate reached the popliteal fossa in a small minority of cases, yet if a clinical analgesic effect is achieved by this mechanism is still unknown.

The Twenty-Five Most Cited Articles About Adductor Canal Block: A Bibliometric Analysis from 1980 to 2022

Introduction

Loco-regional anesthesia role is increasingly important in surgery, especially in postoperative pain control. Using ultrasound-guided techniques has made the loco-regional approach increasingly safe and manageable, guaranteeing excellent analgesic results and patient compliance. This bibliometric research aimed to identify the most influential papers on the adductor canal blocks and outline their characteristics.

Methods

All articles published from 1980 to 2022 were included in the Web of Science, PubMed, and Scopus databases and found using the keywords "Adductor canal block" or "Saphenous nerve block" or "Peripheral nerve block" or "Hunter canal block" or "Subsartorial canal block" or "ACB" or "Knee" or "TKR" or "TKA" or "Analgesia" or "Arthroplasty" or "Replacement" in the title section had bibliometric analysis performed. The first 25 papers were selected and analyzed by the number of citations. The correlation between numerical variables was evaluated using the Pearson Correlation coefficient.

Results

Literature screening found 252 publications. One hundred ten were only about the adductor canal block. Of these, 25 articles were selected for our bibliometric study, published in 8 different journals and with a total number of citations equal to 1.457. "Regional Anesthesia and pain medicine" journal - with 9 articles - was the one that produced the most. There was a significant strong correlation between the n. of citations and the citation rate (R = 0.84, p < 0.001).

Conclusion

The purpose of this study is to be a guide on regional anesthesia and, particularly, on adductor canal block, making the most effective as well as the most cited articles available to anesthesiologists or other researchers interested in this topic.

Ultrasound-guided adductor canal block is superior to femoral nerve block for early postoperative pain relief after single-bundle anterior cruciate ligament reconstruction with hamstring autograft

PURPOSE

This study aimed to compare the combination of a lateral femoral cutaneous nerve (LFCN) block with a femoral nerve block (FNB) and an adductor canal block (ACB) for postoperative pain control in patients undergoing anterior cruciate ligament (ACL) reconstruction with hamstring autograft.

METHODS

A non-randomized, prospective, controlled clinical trial was conducted. The FNB and ACB groups consisted of 41 and 40 patients, respectively. Thirty minutes prior to surgery, the patients received an ultrasound-guided LFCN block either with FNB or ACB. The following values were recorded and compared between the two groups: duration of surgery, pain management during surgery (including total amount of fentanyl administered), and numerical rating scale (NRS) scores at 30 min and 4, 8, 12, 24, 48, and 72 h after surgery. Factors affecting pain relief (NRS < 2) were evaluated, including block type, total amount of fentanyl administered, duration of surgery, age, sex, body mass index, and postoperative suppository use. Significant factors predicting pain relief were determined using the Cox proportional hazard regression model.

RESULTS

There were no significant differences in pain management during the surgery. Pain scores were significantly lower in the ACB group at 30 min, 4 h, 24 h, and 48 h after surgery. The Cox proportional hazard regression model identified ACB as a significant factor for pain relief (hazard ratio: 1.88; 95% confidence interval: 1.12-3.13; p = 0.018).

CONCLUSION

The combination of ACB with LFCN block during ACL reconstruction significantly reduced pain in the early postoperative period compared to FNB with LFCN block.

Pro and Con: How Important Is the Exact Location of Adductor Canal and Femoral Triangle Blocks?

In this Pro-Con commentary article, we debate the importance of anterior thigh block locations for analgesia following total knee arthroplasty. The debate is based on the current literature, our understanding of the relevant anatomy, and a clinical perspective. We review the anatomy of the different fascial compartments, the course of different nerves with respect to the fascia, and the anatomy of the nerve supply to the knee joint. The Pro side of the debate supports the view that more distal block locations in the anterior thigh increase the risk of excluding the medial and intermediate cutaneous nerves of the thigh and the nerve to the vastus medialis, while increasing the risk of spread to the popliteal fossa, making distal femoral triangle block the preferred location. The Con side of the debate adopts the view that while the exact location of local anesthetic injection appears anatomically important, it has not been proven to be clinically relevant.

Motor-Sparing Effect of Adductor Canal Block for Knee Analgesia: An Updated Review and a Subgroup Analysis of Randomized Controlled Trials Based on a Corrected Classification System

OBJECTIVE

Discrepancies in the definition of adductor canal block (ACB) lead to inconsistent results. To investigate the actual analgesic and motor-sparing effects of ACB by anatomically defining femoral triangle block (FTB), proximal ACB (p-ACB), and distal ACB (d-ACB), we re-classified the previously claimed ACB approaches according to the ultrasound findings or descriptions in the corresponding published articles. A meta-analysis with subsequent subgroup analyses based on these corrected results was performed to examine the true impact of ACB on its analgesic effect and motor function (quadriceps muscle strength or mobilization ability). An optimal ACB technique was also suggested based on an updated review of evidence and ultrasound anatomy.

MATERIALS AND METHODS

We systematically searched studies describing the use of ACB for knee surgery. Cochrane Library, PubMed, Web of Science, and Embase were searched with the exclusion of non-English articles from inception to 28 February 2022. The motor-sparing and analgesic aspects in true ACB were evaluated using meta-analyses with subsequent subgroup analyses according to the corrected classification system.

RESULTS

The meta-analysis includes 19 randomized controlled trials. Compared with the femoral nerve block group, the quadriceps muscle strength (standardized mean difference (SMD) = 0.33, 95%-CI [0.01; 0.65]) and mobilization ability (SMD = -22.44, 95%-CI [-35.37; -9.51]) are more preserved in the mixed ACB group at 24 h after knee surgery. Compared with the true ACB group, the FTB group (SMD = 5.59, 95%-CI [3.44; 8.46]) has a significantly decreased mobilization ability at 24 h after knee surgery.

CONCLUSION

By using the corrected classification system, we proved the motor-sparing effect of true ACB compared to FTB. According to the updated ultrasound anatomy, we suggested proximal ACB to be the analgesic technique of choice for knee surgery. Although a single-shot ACB is limited in duration, it remains the candidate of the analgesic standard for knee surgery on postoperative day 1 or 2 because it induces analgesia with less motor involvement in the era of multimodal analgesia. Furthermore, data from the corrected classification system may provide the basis for future research.

Analgesic Impact of a Popliteal Plexus Block to Standard Adductor Canal Block in Arthroscopic Anterior Cruciate Ligament Reconstruction: A Randomized Blind Clinical Trial

Background

Damage to the anterior cruciate ligament (ACL) is crippling and often requires an arthroscopic outpatient surgery. Nevertheless, many patients experience severe pain during the first day after ACL reconstruction (ACLR). The adductor canal block (ACB) has yielded conflicting results for post-ACLR pain relief. This research investigated the effect of a supplemental popliteal plexus block on postoperative pain outcomes compared to a sole ACB.

Methods

Following a randomized design, 60 cases scheduled for knee arthroscopy with ACLR using an ipsilateral hamstring graft were separated into two categories. Subjects in group A (n = 30) received an ACB only, while subjects in group B (n = 30) received combined ACB and popliteal plexus block (PPB).

Results

We found significant differences between the two groups. The time of the first analgesic request (TFR) was later for the combined ACB and PPB (median 8 h) compared to the ACB only group (median 0.5 h). Morphine consumption was lower for patients who received combined ACB and PPB (median 12 mg) compared to ACB only (median 30 mg). The number of the requested doses was lower for the combined ACB and PPB group (median 3 doses) compared to the ACB only group (median 7 doses).

Conclusions

The addition of PPB to ACB was associated with improved analgesia and a reduced need for opioid-based sedatives following ACLR with an ipsilateral hamstring graft (https://clinicaltrials.gov/ct2/show/NCT04020133).

Motor-sparing nerve blocks for total knee replacement: A scoping review

STUDY OBJECTIVE

This scoping review investigates the optimal combination of motor-sparing analgesic interventions for patients undergoing total knee replacement (TKR).

DESIGN

Scoping review.

INTERVENTION

MEDLINE, EMBASE and CINAHL databases were searched (inception-last week of May 2020). Only trials including motor-sparing interventions were included. Randomized controlled trials lacking prospective registration and blinded assessment were excluded.

MAIN RESULTS

The cumulative evidence suggests that femoral triangle blocks outperform placebo and periarticular infiltration. When combined with the latter, femoral triangle blocks are associated with improved pain control, higher patient satisfaction and decreased opioid consumption. Continuous femoral triangle blocks provide superior postoperative analgesia compared with their single-injection counterparts. However, these benefits seem less pronounced when perineural adjuvants are used. Combined femoral triangle-obturator blocks result in improved analgesia and swifter discharge compared with femoral triangle blocks alone.

CONCLUSIONS

The optimal analgesic strategy for TKR may include a combination of different analgesic modalities (periarticular infiltration, femoral triangle blocks, obturator nerve block). Future trials are required to investigate the incremental benefits provided by local anesthetic infiltration between the popliteal artery and the capsule of the knee (IPACK), popliteal plexus block and genicular nerve block.

Femoral nerve block vs adductor canal block after anterior cruciate ligament reconstruction under general anesthesia: A prospective randomized trial protocol

BACKGROUND

Femoral nerve block (FNB) is considered the preferred analgesia after anterior cruciate ligament reconstruction (ACLR), but leads to weakness in the quadriceps muscles. Adductor canal block (ACB) is a new sensory block technique that effectively relieves postoperative pain while preserving quadriceps strength. The purpose of our study was to compare the efficacy of FNB vs ACB for pain control after ACLR.

METHODS

This prospective, randomized, double-blind, controlled, superiority clinical trial was approved by the institutional review board in our university hospital. We enrolled 120 patients set to undergo ACLR in this randomized therapeutic trial. Sixty patients received FNB and the other 60 received ACB for postoperative pain control. All ACB and FNB were performed using ultrasound-guided single-shot procedures. The primary outcomes included maximum voluntary isovolumetric contraction and postoperative pain score. Secondary outcomes included total opioid consumption, length of hospital stay, complication, and satisfaction score.

RESULTS

This clinical trial might provide some insights to estimate and compare the safety and efficacy of ACB vs FNB following ACLR.

TRIAL REGISTRATION

This study protocol was registered in Research Registry (researchregistry5569).

Therapeutic effect of percutaneous vertebroplasty and nonoperative treatment on osteoporotic vertebral compression fracture: A randomized controlled trial protocol

BACKGROUND

Osteoporosis and related complications have been increasing with the aging population. Osteoporotic vertebral compression fractures (OVCFs) are the most common among all osteoporotic fractures. The purpose of this study was performed to compare the efficiency and safety of vertebroplasty versus conservative treatment for acute OVCFs.

METHODS

The conduct of this study followed the Declaration of Helsinki principles and the reporting of this study adhered to the Consolidated Standards of Reporting Trials guidelines for randomized controlled trials. Written informed consent was obtained from every participant. Participants were randomly assigned (1:1) to receive either vertebroplasty or control group. The primary outcome was pain relief at 1 month and 1 year, measured with a Visual Analogue Scale score. The secondary outcomes were Roland-Morris Disability Questionnaire, short form score, European Quality of Life-5 Dimensions, and postoperative complications.

RESULTS

We hypothesize that vertebroplasty will provide a rapid decrease of pain and an early return to daily life activities compared with the control group.

TRIAL REGISTRATION

This study protocol was registered in Research Registry (researchregistry5624).

Comparison of the ultrasound-guided single-injection femoral triangle block versus adductor canal block for analgesia following total knee arthroplasty: a randomized, double-blind trial

PURPOSE

The aim of the study is to compare the femoral triangle (FT) and adductor canal (AC) blocks in terms of the analgesic efficacy and ambulatory outcomes in the context of multimodal analgesia following total knee arthroplasty (TKA).

METHODS

Patients presenting for TKA were assigned to a preoperative ultrasound-guided single-injection FT or AC block. Combined spinal and epidural anesthesia with bupivacaine was administered for TKA. Perioperatively a multimodal analgesic regimen was applied up to 48 h after surgery. The primary outcome was the average pain score during movement in the first 24 h postoperatively. The secondary outcomes included pain scores at rest and during movement at postoperative predetermined time points, cumulative opioid consumption in oral morphine equivalents, functional mobility measured by the timed "Up and Go" (TUG) test and muscle strength in the lower extremity.

RESULTS

Ninety-eight patients completed the study. Patients in the FT group had lower median pain scores during movement in the first 24 h postoperatively than those in the AC group (1.3 [1.0-3.3] vs. 3.0 [1.7-4.3]; median difference: - 1.0, adjusted 95% CI from - 1.7 to - 0.3, P = 0.010). There were significant differences in the pain scores at rest and during movement at 12 and 24 h postoperatively between the two groups (P = 0.008 and 0.005, respectively). Cumulative oral morphine equivalent consumption in the first and second 24 h postoperatively, Functional mobility reflected by the TUG test and muscle strength in the lower extremity showed no significantly statistically differences between the two groups.

CONCLUSIONS

The preoperative FT block provided improved analgesic outcomes without compromising functional mobility in the context of multimodal analgesia following TKA compared with the AC block.

TRIAL REGISTRATION

https://www.chictr.org.cn . Identifier: ChiCTR-INR-17012716.

Proximal versus distal adductor canal blocks for total knee arthroplasty: A protocol for randomized controlled trial

BACKGROUND

Currently, there remains a paucity of literature about the efficiency of proximal adductor canal block (PACB) versus distal adductor canal block (DACB) for pain management after total knee arthroplasty (TKA). The purpose of this study is to perform a randomized controlled trial to compare the efficiency of PACB versus DACB for early postoperative pain treatment after TKA.

METHODS

This study is a 2-arm, parallel-group, randomized controlled trial that is conducted at a single university hospital in China. Subjects presenting for unilateral TKA are randomized in a 1:1 ratio to either a PACB or DACB group. The primary outcome of this noninferiority study is opioid consumption within the first 24 hours following surgery. Secondary outcomes include quadriceps strength, pain scores, distance ambulated, and patient satisfaction. Continuous variables are compared using Student t test.

RESULTS

This clinical trial is expected to provide evidence of whether the PACB and DACB provide similar analgesia after TKA.

TRIAL REGISTRATION

This study protocol was registered in Research Registry (researchregistry5440).

Opioid- and Motor-sparing with Proximal, Mid-, and Distal Locations for Adductor Canal Block in Anterior Cruciate Ligament Reconstruction

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

The ideal location for single-injection adductor canal block that maximizes analgesia while minimizing quadriceps weakness after painful knee surgery is unclear. This triple-blind trial compares ultrasound-guided adductor canal block injection locations with the femoral artery positioned medial (proximal adductor canal), inferior (mid-adductor canal), and lateral (distal adductor canal) to the sartorius muscle to determine the location that optimizes postoperative analgesia and motor function. The hypothesis was that distal adductor block has (1) a superior opioid-sparing effect and (2) preserved quadriceps strength, compared with proximal and mid-locations for anterior cruciate ligament reconstruction.

Methods

For the study, 108 patients were randomized to proximal, mid-, or distal adductor canal injection locations for adductor canal block. Cumulative 24-h oral morphine equivalent consumption and percentage quadriceps strength decrease (maximum voluntary isometric contraction) at 30 min postinjection were coprimary outcomes. The time to first analgesic request, pain scores, postoperative nausea/vomiting at least once within the first 24 h, and block-related complications at 2 weeks were also evaluated.

Results

All patients completed the study. Contrary to the hypothesis, proximal adductor canal block decreased 24-h morphine consumption to a mean ± SD of 34.3 ± 19.1 mg, (P &lt; 0.0001) compared to 64.0 ± 33.6 and 65.7 ± 22.9 mg for the mid- and distal locations, respectively, with differences [95% CI] of 29.7 mg [17.2, 42.2] and 31.4 mg [21.5, 41.3], respectively, mostly in the postanesthesia care unit. Quadriceps strength was similar, with 16.7%:13.4%:15.3% decreases for proximal:mid:distal adductor canal blocks. The nausea/vomiting risk was also lower with proximal adductor canal block (10 of 34, 29.4%) compared to distal location (23 of 36, 63.9%; P = 0.005). The time to first analgesic request was longer, and postoperative pain was improved up to 6 h for proximal adductor canal block, compared to mid- and distal locations.

Conclusions

A proximal adductor canal injection location decreases opioid consumption and opioid-related side effects without compromising quadriceps strength compared to mid- and distal locations for adductor canal block in patients undergoing anterior cruciate ligament reconstruction.

Evaluation of the iPACK block injectate spread: a cadaveric study

BACKGROUND AND OBJECTIVES

Ultrasound-guided infiltration of the interspace between the popliteal artery and capsule of the knee (iPACK) block, a new regional analgesic technique, is believed to relieve posterior knee pain, after total knee arthroplasty, by targeting the articular branches innervating posterior aspect of the joint. The extent of injectate spread and the number of articular branches affected is currently unknown. This cadaveric study aimed to compare the area of dye spread and frequency of articular branches staining following a proximal versus distal injection technique.

METHODS

An ultrasound-guided iPACK injection (10 mL of methylene blue dye solution) was performed in 14 lightly embalmed specimens: 7 injected using a proximal injection technique (1 fingerbreadth above base of patella) and 7 using a distal injection technique (at the superior border of the femoral condyles). Following injection, dissection, digitization, and 3D modeling were performed to map the area of dye spread and determine the frequency of nerve staining.

RESULTS

Both injection techniques achieved a similar mean area of injectate spread. Of the four articular branches supplying the posterior knee joint capsule, the genicular branch of posterior division of obturator nerve was stained in all specimens. The proximal injection resulted in staining of superior medial genicular nerve, due to dye spread through the adductor hiatus, whereas superior lateral genicular nerve and anterior branch of common fibular nerve were consistently stained following distal injection. Other articular branches were stained with variable frequency.

CONCLUSIONS

Both proximal and distal iPACK injection techniques provided a similar area of dye spread in the popliteal region and extensive staining of the articular branches supplying the posterior capsule. The proximal injection technique promoted greater anteromedial dye spread, while the distal injection had more anterolateral spread. Further clinical study is required to confirm our cadaveric findings. .

Defining the Location of the Adductor Canal Using Ultrasound

Background and Objectives

The precise location of the adductor canal remains controversial among anesthesiologists. In numerous studies of the analgesic effect of the so-called adductor canal block for total knee arthroplasty, the needle insertion point has been the midpoint of the thigh, determined as the midpoint between the anterior superior iliac spine and base of patella. “Adductor canal block” may be a misnomer for an approach that is actually an injection into the femoral triangle, a “femoral triangle block.” This block probably has a different analgesic effect compared with an injection into the adductor canal. We sought to determine the exact location of the adductor canal using ultrasound and relate it to the midpoint of the thigh.

Methods

Twenty-two volunteers were examined using ultrasound. The proximal end of the adductor canal was identified where the medial border of the sartorius muscle intersects the medial border of the adductor longus muscle. The distal end of the adductor canal is the adductor hiatus, which was also visualized ultrasonographically.

Results

The mean distance from the anterior superior iliac spine to the midpoint of the thigh was 22.9 cm (range, 20.3–24.9 cm). The mean distance from the anterior superior iliac spine to the proximal end of the adductor canal was 27.4 cm (range, 24.0–31.4 cm). Consequently, the mean distance from the midpoint of the thigh to the proximal end of the adductor canal was 4.6 cm (range, 2.3–7.0 cm).

Conclusions

In all volunteers, the midpoint of the thigh was proximal to the beginning of the adductor canal, suggesting that an injection performed at this level is in fact a femoral triangle block.

Evaluation of the potential efficacy of an ultrasound-guided adductor canal block technique in dog cadavers

OBJECTIVE

To evaluate an ultrasound-guided technique for adductor canal (AC) block by describing the distribution of methylene blue around the AC, popliteal fossa, saphenous, tibial and common fibular nerves in dog cadavers.

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Ten mixed breed canine cadavers weighing 28.55 ± 3.94 kg.

METHODS

Ultrasound scans of the AC were performed bilaterally in 10 canine cadavers. A high-frequency linear transducer was placed on the long axis of the pectineus muscle and using an in-plane technique, an insulated needle was introduced at a proximal to distal direction into the AC. Methylene blue 0.1% (0.3 mL kg^-1) was administered followed by dissection. The presence of dye over the target nerves for ≥2 cm was considered successful distribution. Three of 10 cadavers were submitted to computed tomography (CT) and one of them to magnetic resonance (MR) evaluation.

RESULTS

Methylene blue reached the AC in 20 (100%) and the popliteal fossa in 17 (85%) pelvic limbs. Staining was successful in the saphenous nerve (4.0 ± 1.57 cm) in 11 (55%) limbs, tibial nerve (2.65 ± 0.8 cm) in six (30%) and common fibular nerve (2.7 ± 0.9 cm) in four (20%). There was no evidence of staining around the motor branches of the femoral nerve. No intraneural or intravascular dye spread was found during dissections. Contrast distribution to the popliteal fossa was observed in three limbs (50%) in CT and in one (50%) MR image.

CONCLUSIONS AND CLINICAL RELEVANCE

Although the tibial and common fibular nerves were not stained as often as the saphenous nerve, dye was encountered throughout the popliteal fossa near the nerves. The AC block may be useful for intra and postoperative analgesia in stifle surgery with minimal femoral motor dysfunction. However, further study is required to confirm its efficacy and safety in vivo.

The analgesic effect of a popliteal plexus blockade after total knee arthroplasty: A feasibility study

INTRODUCTION

An obturator nerve block (ONB) and a femoral triangle block (FTB) provide effective analgesia after total knee arthroplasty (TKA) without impeding the ambulation, although the ONB produces motor blockade of the hip adductor muscles. The popliteal plexus (PP) in the popliteal fossa is formed by contribution from the tibial nerve and the posterior obturator nerve, innervating intraarticular genicular structures and the posterior capsule of the knee. We hypothesised that a popliteal plexus block (PPB) as a supplement to an FTB would reduce pain after TKA without anaesthetising motor branches from the sciatic nerve in the popliteal fossa.

AIM

To assess the analgesic effect of adding a PPB to an FTB in 10 subjects with significant pain after TKA.

METHODS

All subjects underwent unilateral TKA with spinal anaesthesia and received an FTB. The cutaneous sensation and the postoperative pain were assessed. The primary outcome was the proportion of subjects with pain above numeric rating scale (NRS) 3 followed by a reduction to NRS 3 or below after conducting a PPB.

RESULTS

Ten subjects with a median pain of NRS 5.5 (interquartile range [IQR] 4-8) after unilateral TKA received a PPB. All 10 subjects experienced a reduction in pain to NRS 3 or below (NRS 1.5 [IQR 0-3]) within a mean time of 8.5 (95% CI 6.8-10.2) minutes. Three subjects were completely pain free after the PPB. The ankle muscle strength was not affected.

CONCLUSIONS

The PPB provided effective pain relief without affecting the ankle muscle strength in all 10 subjects with significant pain after TKA and an FTB.