Effect of iPACK and BiFeS Blocks on Quality of Recovery After Total Knee Arthroplasty (BiFeS-TKA)

May 15, 2026 updated by: Ahmet Murat Yayik, Ataturk University

Effects of iPACK and Biceps Femoris Short Head (BiFeS) Blocks Combined With Adductor Canal Block on Quality of Recovery After Total Knee Arthroplasty: A Prospective, Randomized, Double-Blind Clinical Trial

This prospective, randomized, double-blind clinical trial aims to compare the effects of two different posterior knee analgesia techniques-iPACK block (Interspace Between the Popliteal Artery and the Capsule of the posterior Knee) and the Biceps Femoris Short Head (BiFeS) block-when combined with an adductor canal block (ACB) in patients undergoing elective unilateral total knee arthroplasty (TKA). Effective postoperative analgesia is essential for early mobilization, enhanced recovery, and patient satisfaction after TKA. Although ACB provides good anterior knee analgesia while preserving quadriceps strength, additional posterior knee analgesia is often required.

The iPACK block is a commonly used technique that targets the posterior knee capsule, whereas the newer BiFeS block aims to provide more selective posterolateral sensory blockade with potentially reduced risk of motor involvement. However, comparative clinical data between these two techniques are limited.

The primary objective of this study is to evaluate the difference between the iPACK and BiFeS blocks in terms of Quality of Recovery-15 (QoR-15) scores at 24 hours postoperatively. Secondary objectives include comparisons of postoperative pain scores, opioid consumption, time to first analgesic request, quadriceps and anterior tibialis muscle strength, functional test performance, time to mobilization, active range of motion, and the incidence of adverse events.

A total of 74 adult patients scheduled for elective unilateral TKA under spinal anesthesia will be randomized in a 1:1 ratio into two groups: ACB + iPACK block or ACB + BiFeS block. All blocks will be performed under ultrasound guidance by an experienced anesthesiologist. Outcome assessments will be conducted by blinded investigators. The study aims to provide high-quality clinical evidence regarding the effectiveness of the BiFeS block compared to the widely used iPACK technique.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This study is a prospective, randomized, double-blind, parallel-group, single-center clinical trial designed to compare the effects of two posterior knee analgesia techniques-iPACK block and Biceps Femoris Short Head (BiFeS) block-when combined with an adductor canal block (ACB) on postoperative recovery outcomes following elective total knee arthroplasty (TKA). Postoperative pain after TKA is often severe and can limit early mobilization, delay rehabilitation, and negatively affect recovery. Multimodal analgesia strategies, including regional anesthesia techniques, play an essential role in optimizing postoperative outcomes.

The adductor canal block is widely used because it provides effective anterior knee analgesia while largely preserving quadriceps motor strength. However, it does not adequately address posterior knee pain. The iPACK block is frequently used to supplement ACB, providing analgesia to the posterior knee capsule by targeting the interspace between the popliteal artery and the posterior capsule. The BiFeS block is a newer regional anesthesia technique that involves injection between the femur and the short head of the biceps femoris muscle, targeting terminal sensory branches supplying the posterolateral knee. Cadaveric and early clinical data suggest that the BiFeS block may provide more selective posterior analgesia with limited spread to motor fibers, but comparative clinical data are scarce.

The primary objective of this study is to determine whether the combination of ACB + BiFeS block results in superior quality of recovery compared to ACB + iPACK block, as measured by the QoR-15 score at 24 hours postoperatively. Secondary outcomes include QoR-15 at 48 hours; pain scores at rest and during movement; total opioid consumption at 24 and 48 hours; time to first opioid request; quadriceps and anterior tibialis muscle strength; functional performance assessed using the Timed Up and Go (TUG) and Five Times Sit-to-Stand (FTSST) tests; active knee range of motion; time to first mobilization; and the incidence of adverse events such as nausea, vomiting, pruritus, sedation, neurological symptoms, local anesthetic systemic toxicity, and postoperative falls.

Eligible participants are adults aged 18-75 years undergoing elective primary unilateral TKA under spinal anesthesia, with an ASA physical status of I-III. Exclusion criteria include allergy to study medications, coagulopathy, anticoagulant therapy, severe cardiac, hepatic, or renal dysfunction, pre-existing neuropathic pain, infection at the injection site, neuromuscular disorders of the lower limb, pregnancy, or inability to cooperate with postoperative assessments. Written informed consent will be obtained from all participants. The study has received ethics approval from the Atatürk University Clinical Research Ethics Committee.

Participants will be randomized in a 1:1 ratio using computer-generated block randomization. Both patients and outcome assessors will remain blinded to group assignments. All block procedures will be performed under ultrasound guidance by an experienced anesthesiologist not involved in postoperative assessments. Standardized perioperative management will include spinal anesthesia with hyperbaric bupivacaine, perioperative non-opioid analgesics (paracetamol, dexketoprofen), antiemetic prophylaxis, and postoperative patient-controlled analgesia with fentanyl.

The sample size was calculated based on the minimal clinically important difference (MCID) for the QoR-15 score, assuming an effect size of 8 points, standard deviation of 10, power of 90%, and α = 0.05, resulting in 33 patients per group. Accounting for a 10% dropout rate, 74 patients will be enrolled.

Data will be analyzed using the intention-to-treat principle. Continuous variables will be compared with independent-samples t-tests or Mann-Whitney U tests based on distribution. Mixed-effects models will be used for repeated pain measurements. Categorical variables will be compared using chi-square or Fisher's exact tests. ANCOVA may be applied for adjusted analyses of QoR-15 outcomes.

This trial is expected to contribute important clinical evidence regarding the analgesic effectiveness, functional recovery benefits, and safety profile of the BiFeS block compared with the widely used iPACK block, helping guide postoperative analgesia strategies in total knee arthroplasty.

Study Type

Interventional

Enrollment (Estimated)

74

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 Contact

Study Contact Backup

  • Name: Ahmet Murat Yayık, Associate Professor
  • Phone Number: +90-554-425-92-87
  • Email: m_yayik@hotmail.com

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:

  • Age 18-75 years
  • Scheduled for elective primary unilateral total knee arthroplasty (TKA)
  • Planned spinal anesthesia
  • ASA physical status I-III
  • Ability to understand study procedures and provide written informed consent

Exclusion Criteria:

  • Known allergy or hypersensitivity to local anesthetics or other study medications
  • Coagulopathy or current anticoagulant therapy
  • Severe hepatic, renal, or cardiac failure
  • History of neuropathic pain
  • Infection at the site of proposed nerve block
  • Pre-existing neuromuscular disorders in the lower extremities
  • Inability to cooperate or refusal to participate in the study
  • Pregnancy

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: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Adductor Canal Block + iPACK Block
Participants in this arm will receive an ultrasound-guided adductor canal block (ACB) using 15 mL of 0.25% bupivacaine, followed by an iPACK (Interspace Between the Popliteal Artery and the Capsule of the posterior Knee) block with 25 mL of 0.25% bupivacaine. Blocks will be performed under sterile ultrasound guidance by an experienced anesthesiologist who will not participate in postoperative assessments. All patients will receive standardized spinal anesthesia and perioperative analgesia.
Procedure: Adductor Canal Block (ACB) Only
An ultrasound-guided adductor canal block (ACB) will be performed using 15 mL of 0.25% bupivacaine. The probe will be placed on the proximal thigh to visualize the sartorius muscle and femoral artery. The needle will be advanced in-plane into the adductor canal, and correct placement will be confirmed with 2 mL saline before injection. This block aims to provide anterior knee analgesia while preserving quadriceps strength.
Other Names:
  • ACB
Procedure: IPACK block
The iPACK block will be performed by placing the ultrasound probe at the popliteal region to visualize the popliteal artery and posterior knee capsule. A needle will be advanced in-plane, and 25 mL of 0.25% bupivacaine will be injected between the artery and posterior capsule. This block targets posterior knee pain after total knee arthroplasty without causing motor block.
Other Names:
  • iPACK
  • Interspace Between the Popliteal Artery and the Capsule Block
Experimental: Adductor Canal Block + BiFeS Block
Participants in this arm will receive an ultrasound-guided adductor canal block (ACB) using 15 mL of 0.25% bupivacaine, followed by a BiFeS (Biceps Femoris Short Head) block performed by injecting 25 mL of 0.25% bupivacaine into the potential space between the femur and the short head of the biceps femoris muscle. Procedures will be performed under sterile ultrasound guidance by an anesthesiologist not involved in postoperative assessments. All participants will receive standardized spinal anesthesia and perioperative analgesia.
Procedure: Adductor Canal Block (ACB) Only
An ultrasound-guided adductor canal block (ACB) will be performed using 15 mL of 0.25% bupivacaine. The probe will be placed on the proximal thigh to visualize the sartorius muscle and femoral artery. The needle will be advanced in-plane into the adductor canal, and correct placement will be confirmed with 2 mL saline before injection. This block aims to provide anterior knee analgesia while preserving quadriceps strength.
Other Names:
  • ACB
Procedure: BiFeS Block
The BiFeS block will be performed with the ultrasound probe placed laterally to visualize the femur cortex and the long and short heads of the biceps femoris muscle. The needle will be advanced in-plane into the potential space between the femur and the short head of the biceps femoris. After confirming position with 2 mL saline, 25 mL of 0.25% bupivacaine will be injected. This block provides posterolateral knee analgesia with limited motor involvement.
Other Names:
  • Biceps Femoris Short Head Block
  • BiFeS

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Quality of Recovery-15 (QoR-15) Score at 24 Hours
Time Frame: 24 hours postoperatively
The Quality of Recovery-15 (QoR-15) questionnaire is a validated patient-reported outcome measure assessing overall postoperative recovery across domains such as pain, physical comfort, physical independence, psychological support, and emotional well-being. The total score ranges from 0 to 150, with higher scores indicating better recovery. The outcome compares 24-hour QoR-15 scores between the ACB + iPACK group and the ACB + BiFeS group.
24 hours postoperatively

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Quality of Recovery-15 (QoR-15) Score at 48 Hours
Time Frame: 48 hours postoperatively
The QoR-15 questionnaire assesses multidimensional postoperative recovery, with scores ranging from 0 to 150 (higher scores indicate better recovery). This outcome compares 48-hour QoR-15 scores between the ACB + iPACK and ACB + BiFeS groups.
48 hours postoperatively
Pain Scores (VAS) at Rest and During Movement
Time Frame: 2, 4, 8, 12, 24, and 48 hours postoperatively
Pain intensity will be evaluated using the Visual Analog Scale (VAS), ranging from 0 (no pain) to 10 (worst pain). Assessments will be performed at rest and during movement at predefined postoperative time points.
2, 4, 8, 12, 24, and 48 hours postoperatively
Opioid Consumption (Fentanyl PCA)
Time Frame: 24 and 48 hours postoperatively
Total fentanyl consumption will be extracted from patient-controlled analgesia (PCA) device records, including total delivered dose and number of boluses.
24 and 48 hours postoperatively
Time to First Opioid Request
Time Frame: Up to 48 hours postoperatively
The interval between the end of surgery and the patient's first demand for opioid analgesia via PCA will be recorded, indicating the duration of effective postoperative analgesia.
Up to 48 hours postoperatively
Quadriceps and Anterior Tibialis Muscle Strength
Time Frame: 4, 8, 12, 24, and 48 hours postoperatively
Muscle strength will be assessed using standardized manual muscle testing (0-5 scale) for quadriceps and anterior tibialis muscles. Higher scores reflect greater strength.
4, 8, 12, 24, and 48 hours postoperatively
Timed Up and Go (TUG) Test
Time Frame: Postoperative Day 1 and Day 2
Functional mobility will be evaluated using the TUG test, which measures the time required for a participant to stand from a seated position, walk 3 meters, return, and sit down. Shorter times indicate better mobility.
Postoperative Day 1 and Day 2
Five Times Sit-to-Stand Test (FTSST)
Time Frame: Postoperative Day 1 and Day 2
Lower extremity functional strength will be assessed by recording the time required to stand up and sit down five consecutive times. Faster performance reflects better function.
Postoperative Day 1 and Day 2
Active Range of Motion (Knee Flexion and Extension)
Time Frame: Postoperative Day 1 and Day 2
Knee flexion and extension will be measured using a goniometer to assess active range of motion. Higher degrees indicate improved postoperative mobility.
Postoperative Day 1 and Day 2
Time to First Mobilization
Time Frame: Up to 48 hours postoperatively
The time from arrival in the postoperative care unit to the patient's first successful mobilization (standing or walking with assistance) will be recorded.
Up to 48 hours postoperatively
Adverse Events and Complications
Time Frame: Up to 48 hours postoperatively
Adverse events including nausea, vomiting, pruritus, sedation, falls, neurological symptoms, block-related complications, and signs of local anesthetic systemic toxicity (LAST) will be monitored.
Up to 48 hours postoperatively

Collaborators and Investigators

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

Sponsor

Ataturk University

Investigators

  • Principal Investigator: Ahmet Murat Yayık, Principal Investigator, Ataturk University Department of Anesthesiology and Reanimation
  • Study Director: Mehmet Akif YILMAZ, assistant doctor, Ataturk University Department of Anesthesiology and Reanimation

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)

December 1, 2025

Primary Completion (Estimated)

July 1, 2026

Study Completion (Estimated)

July 2, 2026

Study Registration Dates

First Submitted

November 18, 2025

First Submitted That Met QC Criteria

November 18, 2025

First Posted (Actual)

November 25, 2025

Study Record Updates

Last Update Posted (Actual)

May 18, 2026

Last Update Submitted That Met QC Criteria

May 15, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • B.30.2.ATA.0.01.00/769
  • 2025/2 (Other Identifier: Atatürk University Clinical Research Ethics Committee)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data (IPD) will not be shared because the study involves sensitive patient health information, and data confidentiality will be strictly maintained according to institutional ethical guidelines.

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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