Induced membrane by silver-coated knee megaprosthesis: keep or toss?

The development of prosthesis for wide resection offered to the orthopedic oncological and degenerative surgery further therapeutic opportunities (1). Modular megaprosthesis are currently the most common extremities long bones method of reconstruction thanks to their availability, the relative ease use, the immediate fixation, the early weight bearing, the relatively rapid function recovery and the excellent cosmetic appearance (2). However they represent a complex and not without risks surgery thus solely reserved to selected cases (3). Due to improve the joint replacement procedures, the construct must be long-lasting and biomechanically steady (4). Despite the innovative materials and implant designs, these systems are affected by a high rate of complications among which infections are definitely the most serious (1); revision surgery is thus relatively frequent. Afterwards the joint replacement surgery, the homeostatic balance among the bone and the surrounding soft tissues with the current biomaterials shall be achieved. As well as all medical devices, orthopedic implants may have limited life expectancy due to the host foreign body reaction that may occur when the latter conditions are not met (5). Studies have shown that various biomechanical factors could lead whether a fibrous encapsulation or a bony covering which marks the foreign materials (6). In orthopaedics, the foreign body reaction is well known for therapeutic purposes in the alleged Masquelet technique for segmental bone loss two-stage reconstruction (7). This latter procedure is grounded on the development of an induced membrane around a polymethylmethacrylate (PMMA) spacer which is removed 6–8 weeks after placement. The membrane envelops the cavity thus created, which will then be filled with an autologous corticocancellous bone graft, or similar, in order to achieve bone reconstruction (8). Animal studies were capable of characterizing the membrane architecture demonstrating the wellstructured layered organization (9). Although in Literature there is no univocal evidence on the induced membrane role and benefits so far, previous studies have suggested that this specialized tissue creates advantageous local conditions that promote the bone graft remodeling and osteointegration (10).