Our results showed a great tolerance for silicone spacers to induce Masquelet’s membranes in irradiated sites. Non-irradiated membranes induced by the two spacer types were non-inflammatory, fibrous and organized in layers of collagen fibres. Irradiation did not change the macroscopic properties of membranes induced by silicone, while PMMA induced membranes were sensitive to radiotherapy, resulting in thicker, strongly inflammatory membranes. Irradiated membranes showed an overall reduced osteogenic potential. Although the results need confirmation in a bone site, the use of medical grade silicone for reconstructing large bone defects might be of great advantage for patients under cancer treatment, since the silicone spacer is easy to remove, showed great tolerance for the radiotherapy and better preserved the vascularisation of the membrane. Therefore, radiotherapy could be performed during the time of membrane formation, reducing the number of surgical interventions.