Comparing Analgesic Efficacy of a Novel Dual Subsartorial Block Using Two Different Volumes in Patients Undergoing Total Knee Arthroplasty: A Prospective, Double-Blind, Monocentric, Randomised Trial.

Introduction: Total knee arthroplasty (TKA) is a life-changing joint surgery that improves health-related quality of life and functional status. Patients in need of this surgery mostly belong to the geriatric age group with limited functional reserves and multiple co-morbidities requiring utmost perioperative care with the most suitable analgesic modalities. Regional analgesia (RA) should provide effective analgesia while allowing early mobility, reduced opioid consumption, and early discharge. Dual subsartorial block (DSB) is a novel procedure-specific, motor-sparing, and opioid-sparing RA technique for TKA surgeries. Our study compared the analgesic efficacy of the two different combinations of volumes used in DSB.

Methods: This prospective randomized comparative study included patients between 25-75 years of age of American Society of Anesthesiology (ASA) I-II grades who underwent an elective cemented unilateral total knee replacement performed via medial approaches under neuraxial anesthesia. A total of 104 patients were divided into two equal groups based on the local anesthetic (LA) volumes (Group A 10/20 ml and Group B 20/10 ml) used in the DSB. Postoperative pain scores (using a visual analog scale) and quadriceps strengths (using neurological exam), and opioid consumption were measured at regular intervals till discharge.

Results: Most patients (71.2%) remained pain-free and comfortable until discharge, while 28.8% complained of pain within 12 hours of DSB. Mean quadriceps strength remained almost normal (4-5/5) until the discharge with no incidences of buckling or fall in either group. Over time, the postoperative trend between the groups showed a significant difference for dynamic pain (p = 0.002) and quadriceps strength (p = <0.001). There was an insignificant difference (p = 0.161) between the groups regarding opioid consumption, with the median oral morphine equivalent of zero in both groups.  Discussion: The effective analgesic coverage of DSB is based on the involvement of all innervations of the procedure-specific pain generators of TKR surgeries. The specific focus on selective sensory innervations and the type/volume of the LA used makes DSB a motor-sparing RA alternative that facilitates early mobility and discharge. It can provide effective postoperative analgesia without compromising the motor strength of the quadriceps muscle when administered in either 10/20 or 20/10 volumes.