OBJECTIVES/GOALS: This investigation aimed to develop and validate a subject-specific finite element analysis (FEA) model with subject-specific mechanical loads during walking and to use this method to compare mechanical stresses between transfemoral and transtibial osseointegrated (OI) implants. METHODS/STUDY POPULATION: One patient with a unilateral transtibial OI prosthesis and one with a unilateral transfemoral OI prosthesis participated in motion analysis to collect kinematics and ground reaction forces during overground walking. Subject-specific musculoskeletal models were created, and static optimization was used to estimate muscle and joint reaction forces throughout walking. 3D FEA models of the tibia, femur, and implants were created using ScanIP and exported into ABAQUS CAE. Muscle forces were applied at corresponding origin/insertion locations, determined from the musculoskeletal models [7]. Fixed boundary conditions were applied at proximal joint centers, and bone stresses throughout gait were calculated. OpenSim and FEA derived estimates of joint reaction forces were compared for validation. RESULTS/ANTICIPATED RESULTS: A maximum stress of 65.53 MPa and 60.70 MPa was observed at the bone-implant interface for the transtibial and transfemoral patients (respectively) in the late stance phase of the walking task, corresponding to terminal stance and heel off. Averaged root mean squared errors of the walking task (in the anterior-posterior, inferior-superior, and medial-lateral directions, respectively) for the transtibial and transfemoral patients were (124, 152, 80) N, (71, 80, 30) N, and (190, 62, 30) N, respectively. DISCUSSION/SIGNIFICANCE: The purpose of the above study was to develop a methodology for determining subject-specific mechanical loads during walking using finite element analysis and compare mechanical stresses in patients with transfemoral and transtibial OI. Similar stresses between the two implant types were found.