Over 40 years ago, it was first reported in the orthopedic literature that penicillin, gentamycin, and erythromycin could be introduced into bone cement to help treat and minimize the spread of infection of the bone.¹ Since then, the use of antibiotic-impregnated cement has gone through many modifications. The “two-stage revision,” as it is now known, was first developed and reported by Insall and reported in 1983.² It was initially recommended to allow the cement to cure and properly model to bone and allow a block-like structure to rest on the cortical rim of the tibia. The two-stage revision remains the benchmark in North America for treatment of periprosthetic joint infection (PJI) and carries with it a reported success rate of 80 to 94%.^2,3

By definition, a static spacer keeps the knee joint in full extension or minimal flexion. Advantages of static spacers include lower cost, perceived easier implantation, and joint immobilization to facilitate soft-tissue healing.⁴ The most commonly cited issue with static spacers remains postoperative stiffness.⁴ However, spacer dissociation from the bone ends leading to more bone loss can occur, as well as spacer extrusion, which can result in damage to the extensor mechanism, capsule, and ligaments.⁵

The articulating spacer allowing motion during the treatment period has gained popularity because of the perceived advantages to the patient and surgeon: prevention of extensor mechanism shortening, easier reimplantation surgery, and improved postoperative range of motion.^4,6 This technique has evolved from rudimentary spacers to preserve joint motion to more complex implants with intramedullary rods, which can aid in settings of severe bone loss.⁶ A variation of a mobile spacer is achieved by using antibiotic cement and implanting inexpensive or recycled components to allow for articulation.⁷ The possible development of a biofilm on the metal implant surface remains a concern with some surgeons and continues to push people away from this management method.⁸ Intraoperative molding of cement spacers, either by hand or by cement molds, mimics primary implants and allows surgeons the freedom to select sizes to fit the patient, without exposed metal.^1,4 One concern with intraoperative molds is the rough contact surfaces, which may result in a large amount of cement debris. Examples of intraoperative molding for articulating spacers include Stage One (Biomet, Warsaw IN, USA) and Prostalac (DePuy Synthes, Warsaw IN, USA). Prefabricated, manufactured articulating antibiotic spacers have been on the market for several years. They come with predetermined antibiotic concentrations, most commonly gentamycin.⁹ Some examples of available, prefabricated spacers include the InterSpace (Exactech, Gainesville FL, USA) and the Remedy (OsteoRemedies, Memphis TN, USA). They both contain 0.9-2.7 g of gentamycin per spacer (depending on the size). Factory-manufactured spacers have relatively smooth articular surfaces and well-defined antibiotic elution.