---
title: "INCA trial protocol: Four-nerve motor-sparing strategy versus ACB plus surgeon infiltration for pr"
id: "bmj-open-14-comparison-of-a-four-nerve-block-protocol-versus-adductor-canal-block-plus"
canonical_url: "https://medichelpline.com/clinical-feed/bmj-open-14-comparison-of-a-four-nerve-block-protocol-versus-adductor-canal-block-plus"
content_type: "clinical_feed_article"
specialty: "General"
source_name: "BMJ Open"
source_url: "http://bmjopen.bmj.com/cgi/content/short/16/7/e119093?rss=1"
published_at: "2026-07-21T12:12:52.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# INCA trial protocol: Four-nerve motor-sparing strategy versus ACB plus surgeon infiltration for pr
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/bmj-open-14-comparison-of-a-four-nerve-block-protocol-versus-adductor-canal-block-plus
- **Specialty:** [General](https://medichelpline.com/clinical-feed/general.md)
- **Primary Source:** BMJ Open
- **Source URL:** [Original Journal Publication](http://bmjopen.bmj.com/cgi/content/short/16/7/e119093?rss=1)
- **Published At:** 2026-07-21T12:12:52.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- The INCA trial is a prospective, multicentre, randomised, two-arm superiority protocol comparing a predefined **four-nerve block** strategy to the current standard of **adductor canal block (ACB)** plus active surgeon-delivered **local infiltration analgesia (LIA)** in primary total knee arthroplasty (TKA). - 100 adult patients scheduled for elective unilateral primary TKA will be randomised 1:1 (50 per group) across two French private hospitals with recruitment planned to start 30 April 2026 and anticipated completion February 2027. - Intervention arm: single-shot **ACB** plus three additional ultrasound-guided blocks (lateral femoral cutaneous nerve, obturator nerve and **IPACK**) with sham surgical infiltration; Control arm: single-shot **ACB** plus active peri-articular **LIA** with sham additional blocks. - All participants receive standardised general anaesthesia and identical systemic multimodal analgesia (paracetamol, NSAIDs, nefopam and rescue opioids) to isolate effects of the regional strategies. - Primary outcome: global recovery at 24 hours measured by the **Quality of Recovery-15 (QoR-15)** questionnaire. Secondary outcomes include pain scores at predefined time points, opioid consumption (first 48 hours), rescue analgesia including rescue infiltration, motor function, adverse events, knee range of motion, time to ambulation, PACU and hospital length of stay, QoR-15 at 48 hours and **KOOS-JR** at 1 month. - Randomisation uses a computer-generated concealed sequence with participant-facing sham procedures to preserve blinding; procedural anaesthesiologists and surgeons cannot be blinded. - Operators are experienced regional anaesthesiologists meeting predefined procedural experience thresholds or local sign-off; standard operating procedures, site initiation and prospective recording of deviations are planned to promote reproducibility. - Rescue measures, including escalation of systemic analgesia or rescue active infiltration, are predefined; block failure and inadequate analgesia are defined a priori and managed per protocol; intention-to-treat analysis applies. - Ethical approval by the regional committee (Comité de Protection des Personnes) and written informed consent are required; trial registered as NCT06920186; protocol version 4.0 dated 11 February 2025. - Strengths include concealed randomisation, participant-facing sham procedures, standardised anaesthesia and multimodal analgesia, and a validated primary endpoint; limitations include operator dependence, inability to blind proceduralists, and conduct in two private centres with experienced teams which may limit generalisability.
## Clinical Analysis & Structured Key Points
Skip to main content Intended for healthcare professionals Log In Basket Search for this keyword Advanced search Latest content Archive For authors About Browse by collection You are here Home Archive Volume 16, Issue 7 Email alerts Article Text Article info Citation Tools Share Rapid Responses Article metrics Alerts PDF Anaesthesia Protocol Comparison of a four-nerve block protocol versus adductor canal block plus local infiltration analgesia for primary total knee arthroplasty in two French private hospitals: protocol for the multicentre randomised INCA trial http://orcid.org/0000-0002-7776-4303Yoann Elmaleh1, Olivier Maupain1, Karim Guessous1, Fehmi Kattou1, Raphael Laurent1,2, Thomas Giral1, Thierry Garnier1, Bernard Delvaux1 Correspondence to Dr Yoann Elmaleh; y.elmaleh@quincyanesthesie.com Abstract Background INCA is a multicentre, prospective, randomised, two-arm superiority trial. 100 adult patients scheduled for primary total knee arthroplasty (TKA) will be randomised 1:1 to one of two locoregional analgesia strategies: group 1 (standard strategy), single-shot adductor canal block (ACB) combined with active surgeon-administered peri-articular infiltration with ropivacaine and participant-facing sham peripheral nerve blocks; group 2 (four-nerve block strategy), single-shot ACB combined with three additional ultrasound-guided nerve blocks (lateral femoral cutaneous, obturator and infiltration between the popliteal artery and capsule of the knee (IPACK) blocks) plus sham surgical infiltration. All patients will receive general anaesthesia and identical systemic multimodal analgesia (paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), nefopam and rescue opioids) so that any between-group differences can be attributed to the allocated regional strategy. The primary outcome is global recovery at 24 hours, assessed by the Quality of Recovery-15 (QoR-15) questionnaire. Secondary outcomes include postoperative pain scores, opioid consumption, rescue analgesia including any rescue infiltration, motor function and adverse events, range of motion of the index knee, time to first ambulation, postanaesthesia care unit (PACU) stay, hospital length of stay, QoR-15 at 48 hours and Knee Injury and Osteoarthritis Outcome Score-Joint Replacement (KOOS-JR) at 1 month. Methods INCA is a multicentre, prospective, randomised two-arm superiority trial. 100 adult patients scheduled for primary TKA will be randomised 1:1 to one of two locoregional analgesia strategies: group 1 (standard strategy), single-shot ACB combined with surgeon-administered peri-articular infiltration; group 2 (four-nerve block strategy), single-shot ACB combined with three additional ultrasound-guided nerve blocks (lateral femoral cutaneous, obturator and IPACK blocks) without active infiltration. Participant-facing sham procedures will be used to preserve blinding. All patients will receive general anaesthesia and identical systemic multimodal analgesia (paracetamol, NSAIDs, nefopam and rescue opioids) so that any between-group differences can be attributed to the regional strategy. The primary outcome is global recovery at 24 hours, assessed by the QoR-15 questionnaire. Secondary outcomes include postoperative pain scores, opioid consumption, rescue analgesia including any rescue infiltration, motor function and adverse events, range of motion of the index knee, time to first ambulation, PACU stay, hospital length of stay, QoR-15 at 48 hours and KOOS-JR at 1 month. Ethics and dissemination The study protocol has been approved by the regional ethics committee (Comité de Protection des Personnes). All participants provide written informed consent. The trial will be conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. Study results will be disseminated to participants and submitted for publication in a peer-reviewed journal and presented at national and international conferences to inform best practices in TKA analgesia. Trial registration number NCT06920186. Version 4.0 (11 February 2025). https://creativecommons.org/licenses/by-nc/4.0/ This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: https://creativecommons.org/licenses/by-nc/4.0/. https://doi.org/10.1136/bmjopen-2026-119093 Request Permissions If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways. Request permissions STRENGTHS AND LIMITATIONS OF THIS STUDY Randomised 1:1 allocation with concealed sequence generation will reduce selection bias. Participant-facing sham procedures and blinded postoperative outcome assessment will reduce bias in patient-reported and functional outcomes. General anaesthesia, systemic multimodal analgesia and rehabilitation pathways are standardised across both groups. The primary endpoint is the validated Quality of Recovery-15 score assessed 24 hours after surgery. Operator-dependent block performance, inability to blind the procedural anaesthesiologist and infiltrating surgeon, and conduct in two private centres with experienced regional anaesthesia teams may limit generalisability despite a pragmatic perioperative pathway. Background Total knee arthroplasty (TKA) is associated with intense postoperative pain, justifying the use of multimodal analgesia in which long-acting regional anaesthesia plays a central role.1–3 For years, the femoral nerve block was considered the gold standard for postoperative pain control in knee surgery.4 While it provides reliable and long-lasting analgesia, its major drawback is motor blockade of the quadriceps, which increases the risk of falls and delays early mobilisation.5 These limitations are incompatible with Enhanced Recovery After Surgery programmes that aim for shorter hospital stays and faster return to normal function.6–8 The adductor canal block (ACB), which primarily targets the sensory saphenous nerve, has become a preferred alternative. Performed under ultrasound guidance in the upper thigh through the sartorius muscle,9 ACB provides effective analgesia while preserving quadriceps strength, thus allowing for early ambulation on the day of surgery or the day after without increased fall risk.10 However, the analgesic coverage of ACB, often limited to the saphenous nerve and nerve to vastus medialis, does not address all pain sources around the knee.11 12 To improve its efficacy, ACB is commonly combined with peri-articular local infiltration analgesia (LIA) using long-acting local anaesthetics, a strategy supported by current PROSPECT recommendations.13 This combination reduces pain scores, opioid consumption and may improve early range of motion.14–16 Yet LIA and peripheral nerve blocks are not interchangeable interventions: they differ in anatomical coverage, operator dependence, timing of administration and reproducibility. The clinically relevant question is therefore not whether ‘more blocks are better’, but whether a predefined sensory-oriented multi-block strategy can substitute for active surgeon-delivered infiltration without loss of efficacy and with acceptable feasibility.17 18 Recent studies suggest that combining ACB with additional peripheral nerve blocks may provide better analgesia than pairing it with surgical infiltration.19–21 However, many available comparisons are difficult to interpret because infiltration was used inconsistently across study arms, because only one additional block was tested or because the interventional strategy effectively added techniques rather than substituting one multimodal pathway for another22. The specific role of a sham-controlled substitution design therefore remains insufficiently explored. Other studies have assessed the effect of multiple nerve blocks used in combination.23 ,24 ,25–27 One notable double-blind randomised controlled trial compared a dual block (ACB+infiltration between the popliteal artery and capsule of the knee (IPACK)) to a four-nerve strategy (ACB+IPACK+ lateral femoral cutaneous nerve (LFCN)+obturator nerve block), finding significantly lower morphine consumption in the four-block group (11.2±7.0 mg vs 17.2±9.7 mg, p=0.001).26 These data support the plausibility of broader sensory coverage, but they do not establish whether additional peripheral nerve blocks can substitute for the current multimodal reference strategy of ACB plus LIA. The objective of the INCA trial is therefore to evaluate a predefined motor-sparing four-nerve block strategy, consisting of ACB, LFCN, obturator and IPACK blocks, against the current standard pathway of ACB plus active LIA as a comparison between two fully specified multimodal analgesic strategies. In practical terms, the intervention arm receives quadriblock plus sham surgical infiltration, whereas the control arm receives ACB plus active surgical infiltration with ropivacaine and sham additional blocks. This design was chosen to isolate the incremental value of replacing infiltration with a broader sensory block strategy while preserving patient blinding. The additional blocks target: (1) the LFCN, a purely sensory branch of the lumbar plexus28; (2) the IPACK, which selectively anaesthetises the posterior articular branches of the tibial and peroneal nerves without intended motor impairment29; and (3) the obturator nerve, whose articular branches contribute to innervation of the medial capsule and anteromedial periarticular region. Because the obturator nerve is mixed, any analgesic gain may come at the cost of transient adductor weakness; this risk is therefore explicitly incorporated into the safety assessment. The trial will determine whether this four-nerve block strategy improves recovery while maintaining acceptable motor function and safety despite omission of active infiltration. Neutral or negative results will be interpreted as evidence that replacing infiltration with additional blocks is not advantageous under the tested conditions. Objectives The primary objective of the INCA trial is to determine whether a four-nerve block strategy, including adductor canal, lateral femoral cutaneous, obturator and IPACK blocks together with sham surgical infiltration, improves early postoperative recovery compared with the standard multimodal strategy of a single-shot ACB plus active surgeon-delivered ropivacaine infiltration and sham additional blocks in patients undergoing TKA. The primary outcome is the Quality of Recovery-15 (QoR-15) score measured at 24 hours postoperatively. We hypothesise that patients in the four-nerve block group will report a clinically significant improvement in global recovery, as reflected by a higher QoR-15 score. Secondary objectives include comparison of pain intensity at rest and during movement at defined postoperative time points (2, 6, 12, 24 and 48 hours, and at 1 month), total opioid consumption within the first 48 hours (converted to intravenous morphine equivalents), use of adjunct analgesics and antiemetics, rescue infiltration when required and markers of early functional recovery such as time to ambulation, knee range of motion of the index knee at 48 hours, length of stay in the postanaesthesia care unit (PACU), and total hospital stay. Additional secondary outcomes include patient-reported measures such as QoR-15 at 48 hours, change in Knee Injury and Osteoarthritis Outcome Score-Joint Replacement (KOOS-JR) score from baseline to 1 month, and time to return to daily activities or work. Safety and tolerability outcomes include the incidence of adverse events related to the analgesic technique, including quadriceps weakness, adductor weakness after obturator block, falls, block-related complications and patient-reported discomfort during regional anaesthesia placement. Secondary endpoints will be considered exploratory. In our practice, ACB combined with surgeon-delivered peri-articular infiltration with ropivacaine represents the reference multimodal analgesic pathway for primary TKA and is broadly aligned with current PROSPECT-based care. The intervention arm was intentionally designed as a substitution strategy rather than an augmentation strategy: quadriblock is paired with sham surgical infiltration, while the control pathway combines ACB, sham extra blocks and active infiltration. This prevents the accumulation of active locoregional techniques in one group and allows the trial to test whether a four-nerve motor-sparing strategy can realistically replace infiltration. Before resubmission, the manuscript was rechecked against the current ClinicalTrials.gov record and harmonised for arm descriptions, outcome wording and assessment time points. Methods Study design and setting The INCA trial is a prospective, multicentre, parallel-group, randomised controlled study conducted at two French private hospitals: Hôpital Privé Claude Galien, Quincy-sous-Sénart, France and Clinique des Côtes du Rhône, Roussillon, France (see online supplemental appendix 1). Adult patients scheduled for elective primary unilateral TKA for gonarthrosis will be enrolled and randomised in a 1:1 ratio to one of two perioperative analgesia strategies: a standard regimen combining an ACB with LIA (control group), or an expanded peripheral nerve block protocol (intervention group) consisting of ACB plus additional targeted blocks (IPACK, obturator nerve and lateral femoral cutaneous nerve). A total of 100 participants (50 per group) will be included over an anticipated 12-month recruitment period. Recruitment is planned to start on 30 April 2026, with estimated primary completion in January 2027 and estimated study completion in February 2027. Supplemental material [bmjopen-2026-119093supp001.pdf] Randomisation, allocation concealment and masking Randomisation will be generated using a computerised sequence with concealed allocation through a secure web-based system or sequentially numbered opaque sealed envelopes. To preserve masking, participants allocated to the control group will receive an active ACB, active surgeon-delivered peri-articular infiltration with ropivacaine and sham lateral femoral cutaneous, obturator and IPACK blocks. Participants allocated to the intervention group will receive an active ACB, active lateral femoral cutaneous, obturator and IPACK blocks and sham surgical infiltration without active local anaesthetic. Participants, ward staff, physiotherapists, postoperative outcome assessors, data managers and statisticians will remain blinded to treatment allocation. The anaesthesiologist performing the regional procedures and the surgeon or clinician performing active or sham infiltration cannot be blinded because of the nature of the intervention. Outcome assessments will be conducted by personnel not involved in intervention delivery, and the registry entry was cross-checked against this final masking description before resubmission. Participants Eligible participants are adults (≥18 years) scheduled for elective unilateral primary TKA, able to provide written informed consent and to comply with study procedures and follow-up. Main exclusion criteria include previous major surgery on the index knee, neurological disorders affecting the lower limbs, contraindications to regional anaesthesia (including relevant anticoagulation, local infection at the puncture site or allergy to study drugs), severe cognitive or psychiatric disorders, participation in another interventional trial that may interfere with outcomes, anatomical conditions preventing safe ultrasound-guided block performance, lack of affiliation with the French social security system and legal protection status including guardianship, curatorship or court protection. Pregnant women and women of childbearing potential without effective contraception, according to local regulatory requirements, will be excluded. Patients will be screened and enrolled during preoperative assessment; randomisation will be disclosed shortly before surgery. Patients and the public were not involved in the design, conduct, reporting or dissemination plans of this research. No patients were asked to advise on the research question, outcome measures or study procedures. On study completion, participants may request a lay summary of the overall results in addition to standard scientific dissemination. Interventions All participants will receive standardised general anaesthesia with predefined induction and maintenance agents and perioperative adjunct medications. In both groups, an ultrasound-guided ACB will be performed using ropivacaine. Control group (standard strategy): active ACB+active peri-articular LIA performed by the surgeon (posterior capsule and periarticular soft tissues) using ropivacaine, together with sham lateral femoral cutaneous, obturator and IPACK blocks. This group represents the reference pathway used in the participating centres and corresponds to the current comparator strategy registered on ClinicalTrials.gov. Intervention group (four-nerve block strategy): active ACB+active lateral femoral cutaneous nerve block, active obturator nerve block and active IPACK block, all performed with ropivacaine, together with sham surgical infiltration. No active peri-articular infiltration is administered in this arm. The comparison therefore tests substitution of infiltration by broader sensory block coverage rather than simple addition of blocks. All blocks will be performed by anaesthesiologists experienced in ultrasound-guided regional anaesthesia according to a written standard operating procedure shared by both centres. For this protocol, an experienced operator is defined as an anaesthesiologist routinely practising lower-limb regional anaesthesia who has independently performed at least 50 ACBs and at least 20 procedures for each adjunct technique used in the protocol (lateral femoral cutaneous, obturator and IPACK blocks), or has obtained documented local sign-off after supervised training judged equivalent by the coordinating investigator. Participating anaesthesiologists and surgeons will undergo site initiation focused on the protocol, sham procedures, infiltration technique, local anaesthetic doses and case-report-form completion. The same pool of trained operators will perform procedures in both groups whenever feasible, and key procedural variables, deviations and any retraining needs will be prospectively recorded to promote reproducibility between centres. In the event of block failure or inadequate analgesia, rescue measures may be administered according to a predefined escalation algorithm; participants will remain analysed in their originally assigned group (intention-to-treat). Block failure will be defined a priori as technical inability to complete the allocated procedure and/or absence of the expected sensory effect within the predefined assessment period, when assessable. Inadequate analgesia will be defined as a postoperative pain score ≥4/10 at rest or ≥6/10 during mobilisation despite standard multimodal analgesia. Rescue measures will be recorded in the case report form in chronological order and may include escalation of systemic analgesia and, when clinically required for patient comfort, rescue active infiltration. Rescue infiltration constitutes treatment contamination because it introduces an active component from the comparator pathway into a participant who was not allocated to receive it; it will therefore also be classified as a protocol deviation. Ne
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