A Review of Acrylic Bone Cement in the Masquelet Technique: From Temporary Spacer to a Bioactive Modulator of the Induced Membrane

Critical-sized bone defects remain a major reconstructive challenge, and the Masquelet technique has become an important option in traumatic, infectious, and post-resection settings. This review examines the role of acrylic bone cement in this technique, emphasizing its evolution from a temporary spacer to an active biomaterial that shapes the induced membrane and the local regenerative microenvironment. The article discusses the surgical and biological basis of the technique, the composition and handling characteristics of polymethyl methacrylate (PMMA) bone cement, the rationale for antibiotic-loaded spacers, and the influence of spacer-related variables such as formulation, surface properties, and geometry on membrane quality. It also addresses emerging strategies, including bioactive PMMA modifications, multifunctional cements, and degradable alternatives aimed at improving osteogenesis, angiogenesis, and infection control. Current evidence, derived mainly from in vitro studies and animal models, suggests that the spacer may play a role beyond space maintenance by participating in induced membrane formation and influencing biological signaling related to bone repair. In contrast, the clinical evidence primarily supports the reproducible use of PMMA spacers for dead-space management, infection control, and bone reconstruction. However, important gaps still remain in the translational validation of these biological properties and in the standardization of spacer formulations and antibiotic protocols.