Proximal Spread in Adductor Canal Block(ACB) (ACB)

May 12, 2026 updated by: Müge Çakırca, Ankara Etlik City Hospital

The Impact of Injection Level on the Proximal Spread of Local Anesthetic and Clinical Outcomes in Adductor Canal Block

This prospective, randomized clinical study is designed to evaluate the effects of two different injection levels of adductor canal block (ACB) on the proximal spread of local anesthetic and clinical outcomes in patients undergoing total knee arthroplasty. The study will be conducted at Ankara Etlik City Hospital and will include a total of 68 patients. All cases are limited to unilateral elective knee replacement surgeries performed under spinal anesthesia. In this study, the comparison will be based on the application of adductor canal block at two distinct injection levels. In both groups, blocks will be performed under ultrasound (USG) guidance using the same technical principles and standardized conditions; in the first group, the block will be administered at the level where the vasto-adductor membrane is first visualized, while in the second group, it will be performed at the level where the adductor longus ends. The type, concentration, and volume of local anesthetic used in both groups will be standardized as 20 mL of 0.25% bupivacaine. The groups will be compared in terms of the proximal spread of the local anesthetic based on the injection level, the area of spread at the apex of the iliopectineal fossa, the involvement of the femoral nerve, the incidence of postoperative falls, and analgesic consumption.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Detailed Description

This prospective, randomized clinical trial is designed to evaluate the effects of two distinct injection levels of ultrasound-guided adductor canal block (ACB) on the proximal spread of local anesthetic and clinical outcomes in patients undergoing total knee arthroplasty (TKA). The study will be conducted at Ankara Etlik City Hospital with a total of 68 patients. All cases are limited to unilateral elective knee replacement surgeries performed under spinal anesthesia. Inclusion and Exclusion Criteria Inclusion criteria are defined as patients aged 18 years and older, with an ASA (American Society of Anesthesiologists) physical status of I-III, scheduled for elective unilateral TKA under spinal anesthesia. Exclusion criteria include patients scheduled for bilateral knee arthroplasty, known allergy to local anesthetics, chronic pain syndromes or regular opioid use, peripheral neuropathy or neurological diseases affecting femoral nerve function, coagulopathy or use of anticoagulant therapy, infection at the injection site, and patients unable to provide written informed consent. Randomization and Intervention Patients will be randomized into two groups using the sealed envelope method. In Group 1, the ACB will be performed under ultrasound (USG) guidance at the level where the vasto-adductor membrane (VAM) is first visualized. In Group 2, the block will be performed at the level where the adductor longus muscle ends. All blocks will be administered by experienced anesthesiologists using a standardized dose of 20 mL 0.25% bupivacaine. Clinicians performing the block will not be involved in the postoperative data collection process. Procedure and Monitoring All patients will undergo standard monitoring, including electrocardiography (EKG), non-invasive arterial blood pressure, and peripheral oxygen saturation (SpO_2). Following the administration of spinal anesthesia according to clinical protocols, the ACB will be performed under USG guidance based on the randomization results. Standard care will be provided throughout the surgical and anesthetic management, and perioperative data will be recorded. Outcome Measures and Evaluation Following the block, the spread of the local anesthetic will be evaluated in real-time using ultrasound. The distance between the injection point and the highest proximal point of the anesthetic spread will be measured in centimeters. Additionally, the spread area of the local anesthetic at the level of the apex of the iliopectineal fossa will be recorded using the planimetric measurement tools of the USG device. The reach of the local anesthetic to the femoral nerve will also be assessed via USG. Postoperatively, patients will follow standard clinical monitoring. Motor block will be evaluated based on the incidence of postoperative falls (yes/no). Sensory block efficacy will be assessed through total analgesic consumption recorded within the first 24 hours postoperatively. All collected data will be recorded for statistical analysis and compared based on the injection levels.

Study Type

Interventional

Enrollment (Estimated)

68

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • * Patients aged > 18 years.

    • ASA physical status classification I-III.
    • Patients scheduled for elective, unilateral total knee arthroplasty (TKA).
    • Planned administration of spinal anesthesia.
    • Ability to provide written informed consent.

Exclusion Criteria:Scheduled for bilateral knee arthroplasty.

  • Known hypersensitivity or allergy to local anesthetics.
  • History of chronic pain syndrome or regular opioid consumption.
  • Presence of peripheral neuropathy or neurological disorders affecting the femoral nerve.
  • Coagulopathy or ongoing anticoagulant therapy.
  • Active infection at the site of injection.
  • Inability or refusal to provide written informed consent.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Group 1: ACB at the proximal vasto-adductor membrane level (20 mL 0.25% bupivacaine)
Group 1: Patients receiving ultrasound-guided adductor canal block with 20 mL of 0.25% bupivacaine at the level where the vasto-adductor membrane is first visualized.
Drug: Comparison of Proximal Adductor Canal Block
In this study, patients were evaluated using two distinct approaches based on the evolution of anatomical definitions in recent literature: the proximal application, traditionally referred to as the adductor canal block but now more accurately defined as the 'Femoral Triangle Block' in current publications,
Active Comparator: Group 2: Level of the end of the adductor longus
Group 2: Patients receiving ultrasound-guided adductor canal block with 20 mL of 0.25% bupivacaine at the level where the adductor longus muscle ends.
Drug: Comparison True Distal Adductor Canal Block.
In this study, patients were evaluated using two distinct approaches based on the evolution of anatomical definitions in recent literature: the proximal application, traditionally referred to as the adductor canal block but now more accurately defined as the true 'Distal Adductor Canal Block' performed in accordance with contemporary anatomical criteria."

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Proximal spread of local anesthetic
Time Frame: The first postoperative hour
The primary objective of this study is to compare the proximal spread of local anesthetic following ultrasound-guided adductor canal block performed at two distinct injection levels. In the first group, the injection will be administered at the level where the vastoadductor membrane is first visualized ultrasonographically in the proximal region. In the second group, the injection will be performed at the level where the adductor magnus and sartorius muscles first intersect.In both patient groups, the area of local anesthetic spread at the apex of the iliopectineal fossa will be measured in $cm^2$ using ultrasonography. Additionally, the distance between the needle insertion point (injection level) and the apex of the iliopectineal fossa, as well as the distance from the needle insertion point to the most proximal point where the local anesthetic is ultrasonographically visualized, will be recorded in cm.
The first postoperative hour

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Pain Scores (Numeric Rating Scale)
Time Frame: post-op hours 6 and 24
Evaluation of NRS(Numeric Rating Scale) scores at the 6th and 24th postoperative hours.The Numerical Rating Scale (NRS) is a common subjective clinical tool that requires patients to quantify their pain intensity on a scale ranging from 0 to 10
post-op hours 6 and 24
Assessment of Motor Block
Time Frame: Postoperative 24th hours
Motor block and falls were evaluated at the 24th hour.Ambulation was assessed within the first 24 hours postoperatively. Successful ambulation was defined as the ability to walk without falling; patients who failed to ambulate or suffered a fall during the attempt were categorized as 'treatment failure'.
Postoperative 24th hours

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Ankara Etlik City Hospital

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

April 7, 2026

Primary Completion (Estimated)

May 30, 2026

Study Completion (Estimated)

June 1, 2026

Study Registration Dates

First Submitted

April 7, 2026

First Submitted That Met QC Criteria

May 12, 2026

First Posted (Actual)

May 19, 2026

Study Record Updates

Last Update Posted (Actual)

May 19, 2026

Last Update Submitted That Met QC Criteria

May 12, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2024-KAEK-40 (Ankara Etlik City Hospital Clinical Research Ethics Committee)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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