The accuracy of orthognathic surgery has improved with three-dimensional virtual planning. The translation of the planning to the surgical result is reported to vary by >2mm. The aim of this randomized controlled multi-centre trial was to determine whether the use of splintless patient-specific osteosynthesis can improve the accuracy of maxillary translation. Patients requiring a Le Fort I osteotomy were included in the trial. The intervention group was treated using patient-specific osteosynthesis and the control group with conventional osteosynthesis and splint-based positioning. Fifty-eight patients completed the study protocol, 27 in the patient-specific osteosynthesis group and 31 in the control group. The per protocol median anteroposterior deviation was found to be 1.05mm (interquartile range (IQR) 0.45-2.72mm) in the patient-specific osteosynthesis group and 1.74mm (IQR 1.02-3.02mm) in the control group. The cranial-caudal deviation was 0.87mm (IQR 0.49-1.44mm) and 0.98mm (IQR 0.28-2.10mm), respectively, whereas the left-right translation deviation was 0.46mm (IQR 0.19-0.96mm) in the patient-specific osteosynthesis group and 1.07mm (IQR 0.62-1.55mm) in the control group. The splintless patient-specific osteosynthesis method improves the accuracy of maxillary translations in orthognathic surgery and is clinically relevant for planned anteroposterior translations of more than 3.70mm.