Efficacy of an AFCN Proxy Block in Post-TKA Multimodal Pain Management

Official title

Efficacy Assessment of Supra-Sartorial Subcutaneous Infiltration (SSSI) as an Anterior Femoral Cutaneous Nerve Proxy Block in the Multimodal Pain Management After Total Knee Arthroplasty: A Randomized Controlled Trial

Overview

This randomized controlled trial evaluates the additive effect of Supra-Sartorial Subcutaneous Infiltration (SSSI) when performed in combination with intermittent adductor canal block (iACB) and posterior capsule local infiltration analgesia (PC-LIA) for pain management after total knee arthroplasty (TKA). SSSI, an easy-to-perform tentative proxy block to targeted anterior femoral cutaneous nerve (AFCN) block, is tested in 90 adults (45-90 years) randomized into two arms: active SSSI versus sham SSSI. Primary outcome is pain scores at rest and during movement on postoperative day 0; secondary outcomes include daily pain trajectory at rest and during movement, functional recovery scores, rescue analgesic doses over days 0-3, and quality of recovery assessment on day 4.

Detailed description

This prospective, double-blinded, sham-controlled randomized controlled trial investigates the additive analgesic effect of Supra-Sartorial Subcutaneous Infiltration (SSSI) when combined with intermittent adductor canal block (iACB) and posterior capsule local infiltration analgesia (PC-LIA) following total knee arthroplasty (TKA). The SSSI technique was developed as a simplified, practical alternative to the technically demanding targeted anterior femoral cutaneous nerve (AFCN) block. Drawing on preliminary data where SSSI provided clinically meaningful analgesia in approximately 58% of patients when paired with PC-LIA, this trial evaluates the role of SSSI in enhancing motor-sparing analgesia within a multimodal framework. The study will enroll 90 adults between the ages of 45 and 90 undergoing unilateral primary TKA. Participants will be randomized 1:1 into two groups of 45, with stratification based on gender and baseline Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores. All active interventions utilize 0.3% ropivacaine, while the control arm utilizes saline shams for the SSSI component. The SSSI and iACB catheterizations are performed by anesthesiologists in the post-anesthesia care unit, whereas the PC-LIA is administered intraoperatively by the surgical team. Patients in the active group receive active SSSI, active iACB, and active PC-LIA, while those in the sham group receive a saline SSSI alongside active iACB and active PC-LIA. The primary outcome is defined as Visual Analog Scale (VAS) pain scores at rest and during movement at 9:00 PM on postoperative day 0. Secondary outcomes include daily VAS pain scores at rest and during functional assessments such as continuous passive motion (CPM) and the timed up-and-go (TUG) test through postoperative day 1-4. Additionally, the trial monitors the maximal allowable degree of CPM, TUG test performance, cumulative rescue analgesic doses over the first 4 postoperative days, and Quality of Recovery-15 (QoR-15) scores on postoperative day 4. With approximately 96% power to detect a 2-point difference in pain scores, the trial aims to determine if SSSI significantly improves postoperative analgesia without compromising motor function.

Interventions

• Procedure Supra-Sartorial Subcutaneous Infiltration (SSSI)
  20 mL Ropivacaine or saline infiltrated subcutaneously from lateral to medial, superficial to vastus medialis and sartorius muscle, at femoral triangle apex using inject-as-you-advance technique, avoiding hyperechoic nerves.
• Procedure intermittent adductor canal block (iACB)
  A single-shot adductor canal block is first performed post-operatively with 20 mL 0.3% Ropivacaine at the level of femoral triangle apex before inserting a catheter into the canal. The following doses (20 mL each time) start at 9:00 PM on the day of surgery and are intermittently given every 12 hours until day 4.
• Procedure posterior capsule local infiltration analgesia (PC-LIA)
  PC-LIA consists of two 10 mL injections of 0.3% ropivacaine delivered intraoperatively to the posteromedial and posterolateral aspects of the posterior capsule before cementation. The target injection plane is the potential space between the posterior capsule and the popliteal artery.

Primary outcome measures

• Pain: VAS at rest and during movement on postoperative day 0 [Time frame: at 9 PM on postoperative day 0]

Secondary outcome measures (6)

• Pain: VAS at rest and during movement from postoperative day 1-4 [Time frame: From postoperative day 1 at 6 AM to postoperative day 4 at 6 AM.]
• Rescue ACB doses (0.3% ropivacaine, mg) [Time frame: From the time discharging from post-anesthesia care unit to postoperative day 4 at 6 AM]
• Additional morphine doses (mg) [Time frame: From the time discharging from post-anesthesia care unit to postoperative day 4 at 6 AM]
• Functional: TUG test [Time frame: From postoperative day 1 at 6 AM to postoperative day 4 at 6 AM.]
• Functional: CPM maximal allowable angle [Time frame: From postoperative day 0 at 9 PM to day 3 at 6 PM.]
• Quality of Recovery [Time frame: At postoperative day 4 at 6 AM.]

Eligibility criteria

Inclusion criteria

• Adults aged 45-90 undergoing unilateral primary TKA for osteoarthritis.
• American Society of Anesthesiologists (ASA) physical status I-III.
• Able to provide informed consent and use NRS pain scales.
• Surgery scheduled to start before noon to standardize spinal anesthesia recovery.

Exclusion criteria

• Bilateral or revision TKA.
• Contraindications to regional anesthesia (e.g., coagulopathy, infection at injection site).
• Chronic opioid use (>30 mg morphine equivalents/day) or preoperative NRS >4.
• Pre-existing neurological deficits in lower extremities or AFCN-related neuropathy.
• Allergy to ropivacaine.
• Pregnancy, breastfeeding, or cognitive impairment affecting assessments.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Double blind

Primary purpose

Treatment

Study locations

Taiwan · 1 center

• Taipei Municipal Wanfang Hospital — Taipei

Publications

• Yeoh SR, Chang WC, Wang KL, Tai KY, Hsu FK, Chuang CW. Supra-Sartorial Subcutaneous Infiltration (SSSI) for Anterior Femoral Cutaneous Nerve Coverage in Total Knee Arthroplasty: A Preliminary Clinical Study. Biomedicines. 2025 Sep 27;13(10):2368. doi: 10.3390/biomedicines13102368. PMID 41153655
• Kampitak W, Tanavalee A, Tansatit T, Ngarmukos S, Songborassamee N, Vichainarong C. The analgesic efficacy of anterior femoral cutaneous nerve block in combination with femoral triangle block in total knee arthroplasty: a randomized controlled trial. Korean J Anesthesiol. 2021 Dec;74(6):496-505. doi: 10.4097/kja.21120. Epub 2021 Jun 29. PMID 34182749
• Pivec C, Bodner G, Mayer JA, Brugger PC, Paraszti I, Moser V, Traxler H, Riegler G. Novel Demonstration of the Anterior Femoral Cutaneous Nerves using Ultrasound. Ultraschall Med. 2018 Feb 7. doi: 10.1055/s-0043-121628. Online ahead of print. PMID 29415312
• Bjorn S, Nielsen TD, Jensen AE, Jessen C, Kolsen-Petersen JA, Moriggl B, Hoermann R, Bendtsen TF. The Anterior Branch of the Medial Femoral Cutaneous Nerve Innervates Cutaneous and Deep Surgical Incisions in Total Knee Arthroplasty. J Clin Med. 2024 May 31;13(11):3270. doi: 10.3390/jcm13113270. PMID 38892981
• Bjorn S, Nielsen TD, Jensen AE, Jessen C, Kolsen-Petersen JA, Moriggl B, Hoermann R, Nyengaard JR, Bendtsen TF. The anterior branch of the medial femoral cutaneous nerve innervates the anterior knee: a randomized volunteer trial. Minerva Anestesiol. 2023 Jul-Aug;89(7-8):643-652. doi: 10.23736/S0375-9393.22.16910-5. Epub 2023 Feb 27. PMID 36852567
• Bjorn S, Nielsen TD, Moriggl B, Hoermann R, Bendtsen TF. Anesthesia of the anterior femoral cutaneous nerves for total knee arthroplasty incision: randomized volunteer trial. Reg Anesth Pain Med. 2019 Dec 10:rapm-2019-100904. doi: 10.1136/rapm-2019-100904. Online ahead of print. PMID 31826920

Identifiers

NCT: NCT07191964 · N202511018

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗