The Motor-sparing Paradigm in Knee Analgesia: Advancing Multi-block Strategies with the BiFeS Block as A New Player

Advances in anatomical understanding and enhanced recovery pathways have reshaped regional anaesthesia strategies for total knee arthroplasty (TKA).Motor-sparing techniques have gained increasing importance, reflecting modern priorities such as early mobilisation, reduced fall risk, and optimised functional recovery.This evolution extends beyond the practice patterns described in the review published in the Turkish Journal of Anaesthesiology and Reanimation. 1 Recent systematic evaluations have further highlighted the growing role of selective, function-preserving regional techniques in contemporary perioperative care. 2 Despite progress with anterior-based approaches such as the adductor canal block (ACB), posterolateral knee pain remains a frequently under-addressed component of postoperative discomfort.Anatomical studies have clarified the sensory innervation of the posterior knee capsule, 3 demonstrating contributions from superolateral genicular branches that are not consistently covered by traditional anterior or periarticular techniques.This understanding has stimulated the development of more selective posterior interventions aligned with current motor-sparing goals.Among these innovations, the biceps femoris short head (BiFeS) block represents a recent anatomically targeted addition.First described by Kilicaslan et al., 4 the BiFeS block was designed to target the articular branches that innervate the posterolateral aspect of the knee joint by promoting local anaesthetic spread along the facies poplitea toward the superior lateral genicular nerve and adjacent articular branches, while largely sparing the main motor nerves.4,5 This anatomical selectivity has been proposed as an explanation for its posterolateral analgesic effect without clinically relevant motor impairment.The combined use of ACB and BiFeS blocks has recently been incorporated into our clinical practice.We present a representative case to illustrate the technique and its potential functional profile.A sixty-two-year-old male patient (American Society of Anesthesiologists physical status II) underwent unilateral TKA.Informed consent was obtained from the patient for both the procedure and the publication of this case.With the patient in the supine position, baseline isometric strength of the foot muscles was assessed using a handheld dynamometer.Plantar flexion measured 13.1 kilogram-force (kgf) and dorsiflexion measured 9.4 kgf.After mild sedation (midazolam 1 mg, fentanyl 25 μg, and dexamethasone 8 mg , administered intravenously), an ACB was performed with 15 mL of 0.25% bupivacaine.