ObjectiveTo evaluate three commonly used internal fixations for general floating shoulder injury by biomechanical testing, in order to provide biomechanics basis for surgical choices. MethodsThe superior shoulder suspensory complex (SSSC) was anatomized from 7 cases of antisepsis cadaveric specimens including collarbone and scapula. In the man-made damage models, 4 statuses including prefixation, pure acromioclavicular joint fixation, acromioclavicular joint fixation with scapula neck single plate fixation, and acromioclavicular joint fixation with scapula neck double plate fixation were tested to measure the range of motion (ROM) and neutral zone (NZ) of scapula neck under different statuses by spinal motion analysis system, and stabilizing function of different fixations for instable SSSC were compared. ResultsThe biomechanical testing showed that the NZs of acromioclavicular joint fixation with scapula neck double plate fixation were respectively flexion-extension (3.88±1.71)°, lateral-bending (1.89±0.21)°, and axial-torque (3.13±1.37)°, and the ROMs were respectively flexion-extension (12.91±4.82)°, lateral-bending (18.44±4.43)°, and axial-torque (11.27±4.41)°, which decreased more evidently than other fixation groups (P<0.05). ConclusionAcromioclavicular joint fixation with scapula neck double plate fixation is the best treatment for floating shoulder injury, which can restore the stability of the shoulder effectively.