Classical popliteal sciatic block versus Crosswise Approach to Popliteal Sciatic (CAPS) block for below-knee surgery: a randomised controlled trial.
4 affiliations
- 1Department of Anaesthesiology and Intensive Care, Faculty of Medicine, Hospital Canselor Tuanku Muhriz, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, Cheras, Kuala Lumpur, 56000, Malaysia. [email protected].
- 2Anaesthesiology Unit, Hospital Tunku Ampuan Besar Tuanku Aishah Rohani, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, Cheras, Kuala Lumpur, 56000, Malaysia. [email protected].
- 3Department of Anaesthesiology and Intensive Care, Hospital Canselor Tuanku Muhriz, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, Cheras, Kuala Lumpur, 56000, Malaysia.
- 4Department of Anaesthesiology and Intensive Care, Faculty of Medicine, Hospital Canselor Tuanku Muhriz, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, Cheras, Kuala Lumpur, 56000, Malaysia.
Abstract
Background
Ultrasound-guided popliteal sciatic nerve block is frequently used for below-knee surgery. The classical approach often requires lateral decubitus or prone positioning, which may be uncomfortable for patients with lower limb injuries. The Crosswise Approach to Popliteal Sciatic (CAPS) block allows the procedure to be performed with the patient supine. This randomised trial compared the classical approach with CAPS in terms of patient comfort, block performance, and clinical outcomes.Methods
Eighty American Society of Anesthesiologists Physical Status I-III patients undergoing unilateral below-knee surgery were randomised to receive either a classical popliteal sciatic block in the lateral position (Group A) or a CAPS block in the supine position (Group B). All procedures were ultrasound-guided with 20 mL of 0.5% ropivacaine after lignocaine skin infiltration. All patients also received a femoral nerve block. Pain scores (verbal numerical rating scale [VNRS]) during positioning and block performance, fentanyl requirements, block performance time, sensory onset time, block success, adverse effects, and patient satisfaction were assessed.Results
All blocks were successful. Median highest pain scores were low in both groups (1.5 [classical] vs. 3.0 [CAPS] VNRS; p = 0.050). The proportion of patients reporting no pain (VNRS = 0) did not differ significantly between groups (30.0% [classical] vs. 15.0% [CAPS]; p = 0.180). Fentanyl supplementation (any dose) was required in 45% of Group A and 60% of Group B (p = 0.365). Block performance time was shorter with CAPS (10.5 min) than the classical approach (12.0 min; p = 0.002). Sensory onset time was similar (~ 20 min; p = 0.919). No major complications occurred. Transient sensory symptoms lasting more than 24 h occurred in two patients (5.0%) in Group A and one (2.5%) in Group B. Patient satisfaction remained high in both groups, with 75.0% of Group A and 67.5% of Group B rating satisfaction as 4 or 5 on a 5-point Likert scale (p = 0.120).Conclusion
Both techniques provide effective and safe anaesthesia for below-knee surgery with comparable clinical outcomes. CAPS provides a logistical advantage by allowing the procedure to be performed in the supine position, which may be of value in patients unable to tolerate lateral decubitus positioning, as well as a modest reduction in procedural time (approximately 1.5 min). Either technique may be selected based on patient factors and operator preference.Trial registration
ClinicalTrials.gov (NCT07134608), registered 21 March 2025. Retrospectively registered.
Related
- Sequential Lidocaine and Liposomal Bupivacaine for Popliteal Sciatic Nerve Block in Foot and Ankle Surgery: A Randomized Controlled Trial
- Incidental Popliteal Bursa Localization on I-131 Whole-Body Scintigraphy
- “Pave and Cover” strategy for Rotarex-assisted endovascular repair of thrombosed popliteal artery aneurysm to mitigate distal embolization
- Intravascular ultrasound-guided repair of delayed traumatic popliteal artery occlusion using an interwoven nitinol stent.
- Endovascular repair of iatrogenic popliteal artery injury with acute limb ischemia during unicompartmental knee arthroplasty
BibTeX
@article{teo2026classical,
title = {{Classical popliteal sciatic block versus Crosswise Approach to Popliteal Sciatic (CAPS) block for below-knee surgery: a randomised controlled trial.}},
author = {Rufinah Teo and Iskandar Khalid and Ahmad Faiz Che Kasim and Syarifah Noor Nazihah Sayed Masri and Tse Siang Tan and Nadia Md Nor},
journal = {BMC anesthesiology},
year = {2026},
month = aug,
doi = {10.1186/s12871-026-04137-8},
url = {https://europepmc.org/article/MED/42958476},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Classical popliteal sciatic block versus Crosswise Approach to Popliteal Sciatic (CAPS) block for below-knee surgery: a randomised controlled trial.
AU - Rufinah Teo
AU - Iskandar Khalid
AU - Ahmad Faiz Che Kasim
AU - Syarifah Noor Nazihah Sayed Masri
AU - Tse Siang Tan
AU - Nadia Md Nor
PY - 2026
DA - 2026/08/01
JO - BMC anesthesiology
DO - 10.1186/s12871-026-04137-8
UR - https://europepmc.org/article/MED/42958476
AB - Background Ultrasound-guided popliteal sciatic nerve block is frequently used for below-knee surgery. The classical approach often requires lateral decubitus or prone positioning, which may be uncomfortable for patients with lower limb injuries. The Crosswise Approach to Popliteal Sciatic (CAPS) block allows the procedure to be performed with the patient supine. This randomised trial compared the classical approach with CAPS in terms of patient comfort, block performance, and clinical outcomes.Methods Eighty American Society of Anesthesiologists Physical Status I-III patients undergoing unilateral below-knee surgery were randomised to receive either a classical popliteal sciatic block in the lateral position (Group A) or a CAPS block in the supine position (Group B). All procedures were ultrasound-guided with 20 mL of 0.5% ropivacaine after lignocaine skin infiltration. All patients also received a femoral nerve block. Pain scores (verbal numerical rating scale [VNRS]) during positioning and block performance, fentanyl requirements, block performance time, sensory onset time, block success, adverse effects, and patient satisfaction were assessed.Results All blocks were successful. Median highest pain scores were low in both groups (1.5 [classical] vs. 3.0 [CAPS] VNRS; p = 0.050). The proportion of patients reporting no pain (VNRS = 0) did not differ significantly between groups (30.0% [classical] vs. 15.0% [CAPS]; p = 0.180). Fentanyl supplementation (any dose) was required in 45% of Group A and 60% of Group B (p = 0.365). Block performance time was shorter with CAPS (10.5 min) than the classical approach (12.0 min; p = 0.002). Sensory onset time was similar (~ 20 min; p = 0.919). No major complications occurred. Transient sensory symptoms lasting more than 24 h occurred in two patients (5.0%) in Group A and one (2.5%) in Group B. Patient satisfaction remained high in both groups, with 75.0% of Group A and 67.5% of Group B rating satisfaction as 4 or 5 on a 5-point Likert scale (p = 0.120).Conclusion Both techniques provide effective and safe anaesthesia for below-knee surgery with comparable clinical outcomes. CAPS provides a logistical advantage by allowing the procedure to be performed in the supine position, which may be of value in patients unable to tolerate lateral decubitus positioning, as well as a modest reduction in procedural time (approximately 1.5 min). Either technique may be selected based on patient factors and operator preference.Trial registration ClinicalTrials.gov (NCT07134608), registered 21 March 2025. Retrospectively registered.
SN - 1471-2253
ER -