The induced membrane technique has been used for long bone defect reconstruction after traumatism.
One of the major drawbacks of this method is the difficult removal of the polymethyl methacrylate spacer
after membrane formation. We therefore replaced the stiff PMMA spacer with a semi-flexible medical
grade silicone spacer. This study aimed to compare subcutaneously formed membranes, induced by
PMMA and silicone, in the irradiated or not irradiated areas within 28 rats that received the spacers.
Histological analysis was performed to evaluate the composition of the membrane and to quantify the
amount of vessels. Histomorphometric measurements were used to evaluate membranes’ thickness,
while fibrosis and inflammation were scored. The expression of VEGF and BMP-2 in lysates of the crushed
membranes was determined by Western blotting. ALP expression was analyzed in HBMSC cultures in
contact with the same lysates. Non-irradiated membranes induced by the two spacer types were non-inflammatory,
fibrous and organized in layers. Irradiation did not change the macroscopic properties of
membranes that were induced by silicone, while PMMA induced membranes were sensitive to the radiotherapy,
resulting in thicker, strongly inflammatory membranes. Irradiated membranes showed an overall
reduced osteogenic potential. Medical grade silicone is safe for the use in radiotherapy and might
therefore be of great advantage for patients in need of cancer treatment.