Positioning the Catheter Tip Anterior or Posterior to the Saphenous Nerve in Continuous Adductor Canal Block: A Mono-Centric Retrospective Comparative Study

Antonio Coviello,1 Alessio Bernasconi,2 Giovanni Balato,2 Ezio Spasari,1 Marilena Ianniello,1 Massimo Mariconda,2 Maria Vargas,1 Carmine Iacovazzo,1 Francesco Smeraglia,2 Andrea Tognù,3 Giuseppe Servillo1 1Department of Neurosciences, Reproductive and Odontostomatological Sciences, University of Naples “Federico II”, Naples, 80100, Italy; 2Department of Public Health, School of Medicine, University of Naples “Federico II”, Unit of Orthopedics and Traumatology, Naples, Italy; 3Department of Anesthesiology and Intensive Care Medicine, Istituto Ortopedico Rizzoli IRCCS, Bologna, 40136, ItalyCorrespondence: Antonio Coviello, Department of Neurosciences, Reproductive and Odontostomatological Sciences, University of Naples “Federico II”, Via Vitruvio, 3, Naples, 80100, Italy, Email antonio_coviello@live.itBackground and Aim: Ultrasound-guided continuous adductor canal block (cACB) is a conventional choice in patients undergoing total knee arthroplasty (TKA) for the management of the postoperative pain. This study aims to compare different catheter tip locations for cACB relative to the saphenous nerve (anteriorly vs posteriorly) in terms of efficacy and complications.Methods: At the department of Surgical Sciences, Orthopedic Trauma and Emergencies of the University of Naples Federico II (Naples, Italy), between January 2020 and November 2021, retrospective comparative study was executed. Patients planned for TKA were included in the study if they met the follow inclusion criteria: patients undergone TKA; aged 50– 85 years; body mass index (BMI) of 18– 35 kg/m2; American Society of Anesthesiologists (ASA) physical status classification from I to III; subarachnoid technique for anesthesiology plane; continuous adductor canal block performed by an anesthetist with considerable experience. Patients were assigned to receive cACB with the catheter tip located anteriorly (Group 1, G1) or posteriorly to the saphenous nerve (Group 2, G2). Postoperative pain, a