NATURE BIOMEDICAL ENGINEERING 1, 0087 (2017) | DOI: 10.1038/s41551-017-0087 | www.nature.com/natbiomedeng 1 news & views PUBLISHED: 13 JUNE 2017 | VOLUME: 1 | ARTICLE NUMBER: 0087 O steoarthritis typically results in joint movement becoming increasingly painful where the lubricated articular surface of the cartilage in the joint is progressively degraded. In severe conditions, the replacement of the native joint with an artifcial one, if medically possible, can retain patient mobility 1 . Such artifcial joints are biologically inert materials designed with optimal chemical composition, surface charge and roughness for improved osseointegration; however, the proteins that adsorb to these surfaces and foster osseointegration are also the proteins that encourage bacterial attachment and subsequent bioflm formation 2 . In general, artifcial joints comprise either a mechanically robust metal (commonly titanium alloy, cobalt/chrome/molybdenum alloy or tantalum) stem or a composite stem interfacing with a ceramic or polymer (usually ultrahigh-molecular-weight polyethylene; UHMWPE), shaped to mimic the articulating surface (Fig. 1). In total-joint arthroplasties, of which the most common are artifcial hips and knees, success rates for joint placement and patient satisfaction are generally high. Depending on the design, implants can last between 10 and 20 years, and sometimes longer. When they fail, it is typically because of either aseptic loosening or infection of the joint 3 . Aseptic loosening is mainly associated with material degradation, infammation, and osteolysis — that is, bone resorption induced by wear particles. Infection is an uncommon complication (average rates are in the 1–2% range) that leads to implant failure, and is devastating for patients 4 . During the primary implantation of the artifcial joint, such as a hip implant, the synovium (connective tissue lining the inner surface of synovial joints and tendon sheath) is retained as much as possible so that the implant resides in a similar environment to the native hip. If bacterial colonization occurs, poor antibiotic penetrance and facilitated bacterial bioflm formation in the presence of the implant leaves little choice but for a surgical intervention to remove infected materials. In the case of an established infection, joint components are removed, bone surfaces are debrided, and any remaining synovium is removed. All joint surfaces are aggressively washed with various antiseptics. At this juncture, implantation of a new artifcial joint can occur — and fxation of the implant is usually done with bone cement, which can be used as a reservoir for antibiotics. Tis type of re-implantation is referred to as a one-stage revision, and is ofen used in Europe. Alternatively, an implanted cement spacer that contains antibiotics and that can bear some weight serves as an antibiotic-elution system. Te spacer is usually retained for at least six weeks, during which antibiotic elution, which decreases over time, is designed to prevent the re-establishment of infection. But the antibiotic levels in the spacer compromise its mechanical robustness. Afer six weeks, if the clinical signs are favourable, the patient undergoes a revision surgery with the implantation of a new, usually cemented artifcial joint, thus completing the two-stage procedure commonly used in the United States. With these aggressive measures, successful eradication of infection only occurs in 20–90% of the cases 5 . To improve antibiotic-elution characteristics, diferent antibiotic controlled-release systems have been developed 6 , but they do not elute antibiotics for the necessary several weeks or have sufcient mechanical robustness. Reporting in Nature Biomedical Engineering, Ebru Oral and colleagues now show that a mechanically robust artifcial joint designed to include both a long-term antimicrobial surface and an antibiotic- elution system 7 allows for long-term retention of the joint implant, which should lead to a decrease of surgical procedures and costs, and ultimately save lives. Oral and co-authors loaded the UHMWPE articulating joint with either vancomycin, or rifampin and vancomycin, a combination that increases efcacy against both Gram-negative and Gram-positive strains of bacteria. One challenge was to balance the antibiotic-elution levels required for efcacy (more than three weeks) with acceptable mechanical properties for the UHMWPE implant. Te authors found that drug clusters with eccentric shape and JOINT IMPLANTS An elution solution An optimized drug-eluting polymer for the surface of articulating artifcial joints may make them infection-free. Noreen J. Hickok Pelvis Acetabulum Femur Acetabular cup Femoral head Textured stem Native hip Total-hip components Articulating surfaces Insert Cut Figure 1 | A ball-and-socket hip-joint replacement. The cartilage (blue) coats the femoral head and the acetabulum; when lubricated by the proteins in the synovial fuid, the joints enjoy essentially friction-free movement. In a hip replacement, the acetabulum is removed and the femoral head is sawn of. In the uncemented version shown here, the femoral canal is reamed and the stem of the hip implant is press-ft inserted into the reamed bone. The replacement acetabular cup is anchored into the pelvis, allowing re-creation of the ball-and-socket joint. Usually enough synovium remains to allow for the production of synovial fuid that lubricates the articulating surfaces. Figure adapted from ref.  7 , Macmillan Publishers Ltd. ©2017MacmillanPublishersLimited,partofSpringerNature.Allrightsreserved.