An interventional study of Ultrasound-Guided iPACK Block and Ultrasound-Guided Popliteal Plexus Block in Osteoarthritis, Knee and Postoperative Pain, sponsored by Clinica Santa Maria. Not yet recruiting. Open to participants aged 18 Years to 85 Years. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Clinica Santa Maria · Not applicable, Interventional, and Treatment
Total knee arthroplasty (TKA) is commonly associated with significant postoperative pain, including pain arising from the posterior aspect of the knee. Regional anesthesia techniques are frequently used as part of a multimodal analgesic strategy to improve pain control, reduce opioid requirements, and facilitate early functional recovery.
This prospective, randomized, double-blind, superiority clinical trial will compare the analgesic efficacy of the interspace between the popliteal artery and capsule of the posterior knee (iPACK) block with the popliteal plexus block in adult patients undergoing elective unilateral primary total knee arthroplasty. All participants will receive a continuous femoral triangle block and a standardized multimodal postoperative analgesic regimen.
Participants will be randomly assigned to receive either an ultrasound-guided iPACK block or an ultrasound-guided popliteal plexus block. The primary outcome will be cumulative intravenous morphine consumption delivered through a patient-controlled analgesia (PCA) device during the first 24 hours after surgery.
Secondary outcomes will include cumulative morphine consumption during the first 12 hours, posterior knee pain at rest and during movement, time to first PCA morphine administration, quality of recovery assessed with the QoR-15 questionnaire, distal motor function, early functional recovery, block performance time, postoperative adverse effects, and neurological symptoms.
The study hypothesis is that the popliteal plexus block will provide superior opioid-sparing analgesia compared with the iPACK block when both techniques are combined with a continuous femoral triangle block, while preserving distal motor function and maintaining an acceptable safety profile.
Total knee arthroplasty (TKA) is commonly associated with significant postoperative pain, including pain arising from the posterior aspect of the knee. Effective multimodal analgesia is important to facilitate early mobilization, functional recovery, participation in physical therapy, and patient satisfaction while minimizing opioid consumption and opioid-related adverse effects.
Motor-sparing regional anesthesia techniques are an important component of multimodal analgesia for TKA. The femoral triangle block provides analgesia primarily to the anterior and medial aspects of the knee while aiming to preserve quadriceps motor function. However, additional regional anesthesia techniques are often required to adequately treat pain originating from the posterior aspect of the knee.
The interspace between the popliteal artery and capsule of the posterior knee (iPACK) block is commonly used to provide posterior knee analgesia by targeting terminal articular sensory branches while minimizing blockade of the main tibial and common peroneal nerves. The popliteal plexus block (PPB) is an alternative motor-sparing regional anesthesia technique targeting the neural plexus contributing to the sensory innervation of the posterior knee.
Previous randomized studies suggest that the popliteal plexus block can provide effective posterior knee analgesia while preserving distal motor function. Direct comparison with the iPACK block has demonstrated non-inferior analgesia and shorter block performance time. Nevertheless, uncertainty remains regarding whether the popliteal plexus block provides superior opioid-sparing analgesia compared with the iPACK block when both techniques are incorporated into an otherwise standardized multimodal analgesic regimen.
This prospective, randomized, double-blind, superiority clinical trial will compare ultrasound-guided popliteal plexus block with ultrasound-guided iPACK block in adults undergoing elective unilateral primary total knee arthroplasty. All participants will receive a continuous femoral triangle block and a standardized multimodal postoperative analgesic regimen.
Participants will be randomly allocated to one of two parallel groups. Participants in the active comparator group will receive an ultrasound-guided iPACK block, whereas participants in the experimental group will receive an ultrasound-guided popliteal plexus block. Perioperative anesthetic management, continuous femoral triangle analgesia, postoperative multimodal analgesia, and intravenous patient-controlled analgesia (PCA) settings will otherwise be standardized between groups.
The primary outcome will be cumulative intravenous morphine consumption administered through the PCA device during the first 24 hours after surgery. The study is designed to test the hypothesis that the popliteal plexus block is superior to the iPACK block in reducing 24-hour postoperative morphine consumption.
Secondary opioid-related outcomes will include cumulative intravenous morphine consumption during the first 12 hours after surgery and the time from the end of surgery to the first successful intravenous morphine administration through the PCA device.
Posterior knee pain will be evaluated separately at rest and during movement using an 11-point Numeric Rating Scale (NRS) ranging from 0 to 10, where 0 represents no pain and 10 represents the worst imaginable pain. Posterior knee pain will be assessed at 2, 4, 6, 12, and 24 hours postoperatively.
Quality of postoperative recovery will be evaluated using the 15-item Quality of Recovery questionnaire (QoR-15). The questionnaire will be administered preoperatively and 24 hours after surgery. The 24-hour QoR-15 score will be compared between groups, with the preoperative score used as a baseline measure of recovery status.
Distal motor function will be evaluated by assessing ankle dorsiflexion and plantar flexion strength using the Medical Research Council (MRC) muscle strength scale. Motor function will be assessed preoperatively and at 6 and 24 hours postoperatively to determine whether either posterior knee block results in clinically relevant distal motor impairment.
Early functional recovery will also be assessed during the first postoperative physical therapy evaluation within 24 hours after surgery. The ability to perform an active straight leg raise will be recorded as a binary outcome (Yes/No). The ability to stand and ambulate using the prescribed assistive device, such as a walker or crutches, will also be recorded as a binary outcome (Yes/No). When ambulation is not achieved, the principal reason will be documented when possible, including motor weakness, pain, dizziness or hypotension, nausea, or other causes.
The technical efficiency of the two posterior knee blocks will be evaluated by measuring block performance time. Performance time will be recorded in minutes and defined as the interval from initial placement of the ultrasound transducer for acquisition of the block image until withdrawal of the block needle following completion of local anesthetic injection.
Postoperative adverse effects will include nausea and vomiting, pruritus, and urinary retention. Procedure-related safety outcomes will include accidental vascular puncture, local anesthetic systemic toxicity, and new postoperative neurological symptoms.
Neurological symptoms potentially related to the regional anesthesia procedures, including numbness, paresthesia, dysesthesia, weakness, or other new sensory or motor deficits affecting the operated lower limb, will be assessed during the postoperative period. Participants will additionally undergo a standardized telephone follow-up approximately 7 days after surgery to identify persistent or newly reported neurological symptoms. Participants reporting clinically relevant persistent, progressive, or motor neurological deficits will be referred for further clinical evaluation according to institutional practice.
The study aims to determine whether the popliteal plexus block provides superior opioid-sparing analgesia compared with the iPACK block when both are used as adjuncts to a continuous femoral triangle block for primary total knee arthroplasty. In addition to analgesic efficacy, the study will evaluate posterior knee pain, quality of recovery, distal motor function, early functional recovery, technical efficiency, and the safety profile of both regional anesthesia techniques.
3,391 studies on the registry are indexed under Osteoarthritis, Knee; 628 are open to participants now.
This study's planned enrollment of 136 is above the median of 69 across 2,808 interventional studies indexed under Osteoarthritis, Knee.
Browse Osteoarthritis, Knee studies →Clinica Santa Maria is the lead sponsor of 3 studies on the registry; 1 is open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Participants allocated to this group will receive an ultrasound-guided iPACK (interspace between the popliteal artery and capsule of the posterior knee) block using 20 mL of 0.25% bupivacaine. All participants will also receive a continuous femoral triangle block and standardized multimodal postoperative analgesia
Procedure: Ultrasound-Guided iPACK Block · Procedure: Ultrasound-Guided Continuous Femoral Triangle Block
Participants allocated to this group will receive an ultrasound-guided popliteal plexus block using 20 mL of 0.25% bupivacaine. All participants will also receive a continuous femoral triangle block and standardized multimodal postoperative analgesia
Procedure: Ultrasound-Guided Popliteal Plexus Block · Procedure: Ultrasound-Guided Continuous Femoral Triangle Block
An ultrasound-guided iPACK block will be performed by depositing 20 mL of 0.25% bupivacaine in the tissue plane between the popliteal artery and the posterior capsule of the knee to provide analgesia to the posterior aspect of the knee while minimizing blockade of the major motor branches of the sciatic nerve
An ultrasound-guided popliteal plexus block will be performed using 20 mL of 0.25% bupivacaine. The technique is intended to provide analgesia to the posterior aspect of the knee by targeting the neural plexus contributing to the sensory innervation of the posterior knee while minimizing clinically relevant distal motor blockade
All participants will receive an ultrasound-guided continuous femoral triangle block. An initial bolus of 20 mL of 0.25% bupivacaine will be administered, followed by a continuous infusion of 0.1% bupivacaine at 5 mL/hour through a perineural catheter as part of the standardized postoperative analgesic regimen
Cumulative Intravenous Morphine Equivalent Consumption During the First 24 Hours After Surgery.
Total cumulative intravenous morphine consumption administered through a patient-controlled analgesia (PCA) device during the first 24 hours after primary total knee arthroplasty. The total amount of morphine delivered by the PCA device will be recorded for each participant and expressed in milligrams (mg).
Time frame: From the end of surgery to 24 hours postoperatively.
Cumulative Intravenous Morphine Consumption During the First 12 Hours After Surgery
Total cumulative intravenous morphine consumption administered through a patient-controlled analgesia (PCA) device during the first 12 hours after primary total knee arthroplasty. The total amount of morphine delivered by the PCA device will be recorded for each participant and expressed in milligrams (mg).
Time frame: From the end of surgery to 12 hours postoperatively.
Posterior Knee Pain During Movement
Pain specifically localized to the posterior aspect of the operated knee will be assessed during movement using an 11-point Numeric Rating Scale (NRS) ranging from 0 to 10, where 0 represents no pain and 10 represents the worst imaginable pain.
Time frame: 2, 4, 6, 12, and 24 hours postoperatively.
Posterior Knee Pain at Rest
Pain specifically localized to the posterior aspect of the operated knee will be assessed at rest using an 11-point Numeric Rating Scale (NRS) ranging from 0 to 10, where 0 represents no pain and 10 represents the worst imaginable pain.
Time frame: 2, 4, 6, 12, and 24 hours postoperatively.
Time to First Patient-Controlled Analgesia Morphine Demand
Time elapsed from the end of surgery until the first successful intravenous morphine administration through the patient-controlled analgesia (PCA) device.
Time frame: From the end of surgery to 24 hours postoperatively.
Change in Quality of Recovery-15 (QoR-15) Score at 24 Hours
Quality of postoperative recovery will be assessed using the 15-item Quality of Recovery questionnaire (QoR-15). The questionnaire will be administered preoperatively and 24 hours after surgery. The QoR-15 total score ranges from 0 to 150, with higher scores indicating better quality of recovery. Change from the preoperative baseline score to the 24-hour postoperative score will be compared between groups
Time frame: Preoperatively and 24 hours after surgery.
Ankle Dorsiflexion Motor Strength
Motor strength of ankle dorsiflexion will be assessed using the Medical Research Council (MRC) muscle strength scale, ranging from 0 to 5, where 0 represents no visible muscle contraction and 5 represents normal strength against full resistance.
Time frame: Preoperatively, and at 6 and 24 hours postoperatively.
Ankle Plantar Flexion Motor Strength
Ankle plantar flexion strength will be assessed using the Medical Research Council (MRC) muscle strength scale, ranging from 0 to 5, where 0 represents no visible muscle contraction and 5 represents normal strength against full resistance.
Time frame: Preoperatively, and at 6 and 24 hours postoperatively.
Ability to Perform an Active Straight Leg Raise
The ability to actively elevate the operated lower limb with the knee maintained in extension will be assessed as a binary outcome (Yes/No). A successful straight leg raise will be defined as the participant being able to lift the operated leg from the bed while maintaining knee extension, without physical assistance.
Time frame: During the first postoperative physical therapy assessment, within 24 hours after surgery.
Ability to Ambulate With an Assistive Device
The ability to ambulate using the prescribed assistive device, such as a walker or crutches, will be assessed as a binary outcome (Yes/No) during the first postoperative physical therapy session. Successful ambulation will be defined as the participant being able to stand and ambulate using the prescribed assistive device, with supervision or verbal guidance if required.
Time frame: During the first postoperative physical therapy session, within 24 hours after surgery.
Performance Time of the Study Block
The time required to perform the assigned posterior knee block (iPACK block or popliteal plexus block) will be recorded in minutes. Block performance time will be defined as the interval from initial placement of the ultrasound transducer for acquisition of the block image until withdrawal of the block needle following completion of local anesthetic injection.
Time frame: During performance of the study regional anesthesia procedure.
Incidence of Postoperative Nausea and Vomiting
Number and proportion of participants experiencing nausea and/or vomiting during the first 24 hours after surgery.
Time frame: Within 24 hours after surgery.
Incidence of Postoperative Pruritus
Number and proportion of participants experiencing pruritus during the first 24 hours after surgery.
Time frame: Within 24 hours after surgery
Incidence of Postoperative Urinary Retention
Number and proportion of participants developing urinary retention during the first 24 hours after surgery.
Time frame: Within 24 hours after surgery.
Incidence of Accidental Vascular Puncture
Number and proportion of participants in whom accidental vascular puncture occurs during performance of the study regional anesthesia procedure.
Time frame: During performance of the regional anesthesia procedure.
Incidence of Local Anesthetic Systemic Toxicity
Number and proportion of participants presenting signs or symptoms consistent with local anesthetic systemic toxicity following regional anesthesia.
Time frame: From performance of the regional anesthesia procedures to 24 hours postoperatively.
Incidence of Postoperative Neurological Symptoms
The number and proportion of participants presenting new neurological symptoms potentially related to the regional anesthesia procedures will be recorded. Symptoms of interest will include persistent numbness, paresthesia, dysesthesia, weakness, or other new sensory or motor deficits. Neurological symptoms will be assessed during the first 24 hours after surgery and reassessed by a standardized telephone follow-up approximately 7 days after surgery.
Time frame: From the regional anesthesia procedure through 7 days postoperatively.
No study locations are listed for this record.
Plan to share: Yes — De-identified individual participant data underlying the results reported in the primary publication may be made available to qualified researchers upon reasonable request to the principal investigator. Requests will be evaluated based on scientific merit and will be subject to applicable institutional and ethical requirements.
Supporting information: Study protocol, Statistical analysis plan
Time frame: Data will be available following publication of the primary study results and for a period of 5 years.
Access criteria: Data may be provided to qualified researchers with a methodologically sound research proposal, following approval by the study investigators and subject to applicable ethical, institutional, and data protection requirements.
No publications or documents are linked to this record.
Start is estimated for Nov 2026; primary completion for May 2028, 18 months later.
Of 1,143 non-industry interventional studies with no phase under Osteoarthritis, Knee, half reached primary completion within 18 months of starting (the median), counting those still running; a quarter within 8 and three quarters within 36. This study's planned 18 months is close to that.
Counting every sponsor, half of 1,285 studies reached it within 18 months; a quarter within 8 and three quarters within 36.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Clinica Santa Maria