<![CDATA[Postoperative recovery following major orthopedic and abdominal surgery is frequently complicated by metabolic stress, hypercatabolism, skeletal muscle loss, and prolonged hospitalization. Surgical trauma triggers inflammatory and neuroendocrine responses that accelerate muscle protein breakdown and impair functional recovery. Amino acid supplementation, particularly formulations enriched with essential amino acids (EAAs) and branched-chain amino acids (BCAAs), has been proposed as a targeted nutritional strategy to preserve muscle mass and enhance postoperative outcomes. However, evidence across surgical specialties remains heterogeneous. This systematic review aimed to evaluate the effectiveness of perioperative amino acid supplementation in improving muscle-related recovery, enhancing functional outcomes, and reducing hospital length of stay (LOS) in adult patients undergoing orthopedic or abdominal surgery. A systematic literature search was conducted following the PRISMA 2020 guidelines using the PubMed/MEDLINE, ScienceDirect, and Embase databases. Eligible studies included randomized controlled trials and comparative retrospective studies involving adults (>18 years) receiving enteral or parenteral amino acid supplementation during the perioperative period. Primary outcomes included postoperative muscle mass, muscle strength, functional recovery indicators, and hospital LOS. Risk of bias was assessed using the Cochrane RoB 2 tool and ROBINS-I. From 200 identified records, 10 studies comprising 1,061 patients met the inclusion criteria. The included studies involved patients undergoing orthopedic procedures (total hip arthroplasty, total knee arthroplasty, hip fracture surgery) and abdominal surgeries (gastrectomy, colectomy, gastrointestinal cancer resection). Evidence suggests that EAA and BCAA supplementation contributes to better preservation of skeletal muscle mass and faster recovery of muscle strength, particularly when combined with postoperative rehabilitation.]]>
