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IntroductionPatient specific instrumentation is a novel aid the industry has been implementing in our hospitals during the last years. However, the cost of the process and the impossibility to discuss face to face with the manufacturer the needs of the particular cases may favor the in-hospital production of these devices.We present the design and manufacturing process of three patient-specific devices to treat complex common situations in orthopaedic surgery, such as intramedular tumor resections, long bone pseudarthrosis and malunions of articular fractures.Material and MethodsCT scans of the region of interest were performed to all the patients. Horos® software was used to isolate the affected bone region, whereas Meshmixer® software was used to create the patient specific guides. An Ultimaker 2+® 3D printer was used to print the guide, in a biocompatible material (SmartFil® Medical). The printing parameters included a nozzle of 0.6 mm and a layer height of 0.1 mm.There was one case of a low-grade chondrosarcoma in which we created a guide to resect enough cortical bone to make an extended curettage of the lesion. Phenol and PMMA were used as adjuvants after the curettage. We used the same guide to obtain an exact replica of allograft which was later placed in position.We had a femur diaphyseal atrophic pseudarthrosis in a patient with achondroplasia, in which the guide permitted the resection of the affected bone with a saw and posterior osteosynthesis with an anterior LCP plate.Finally, in an intraarticular malunion of a distal radius Die-Punch fracture we used the guide to make an osteotomy of the affected articular portion and correct the articular surface. Bone autograft was added prior to the osteosynthesis with a plate.ResultsMean design time was 6.3 hours. Mean printing time was 5.2 hours. The price of the filament used for each guide was under 10 USD. The mean time from the CT-Scan and the surgery being performed was 2.7 months. In all cases the patient specific guides fitted in the bone and permitted the planned resection/osteotomy.All the surgeries fulfilled their purpose.ConclusionsPatient specific guides are easy to design in a local setting with the aid of free software. Design time still needs dedication although it permits the manufacturing of the guides following surgeon needs. The use of self-designed and printed guides is safe and accurate, with a low cost for the institutions.