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Aims We propose a state-of-the-art temporary spacer, consisting of a cobalt-chrome (CoCr) femoral component and a gentamicin-eluting ultra-high molecular weight polyethylene (UHMWPE) tibial insert, which can provide therapeutic delivery of gentamicin, while retaining excellent mechanical properties. The proposed implant is designed to replace conventional spacers made from bone cement. Methods Gentamicin-loaded UHMWPE was prepared using phase-separated compression moulding, and its drug elution kinetics, antibacterial, mechanical, and wear properties were compared with those of conventional gentamicin-loaded bone cement. Results Gentamicin-loaded UHMWPE tibial components not only eradicated planktonic Staphylococcus aureus, but also prevented colonization of both femoral and tibial components. The proposed spacer possesses far superior mechanical and wear properties when compared with conventional bone cement spacers. Conclusion The proposed gentamicin-eluting UHMWPE spacer can provide antibacterial efficacy comparable with currently used bone cement spacers, while overcoming their drawbacks. The novel spacer proposed here has the potential to drastically reduce complications associated with currently used bone cement spacers and substantially improve patients’ quality of life during the treatment. Cite this article: Bone Joint J 2020;102-B(6 Supple A):151–157.

Total joint arthroplasty is one of the most common surgeries in the United States, with almost a million procedures performed annually. Periprosthetic joint infections (PJI) remain the most devastating complications associated with total joint replacement. Effective antibacterial prophylaxis after primary arthroplasty could substantially reduce incidence rate of PJI. In the present study we propose to provide post‐arthroplasty prophylaxis via dual‐analgesic loaded ultra‐high molecular weight polyethylene (UHMWPE). Our approach is based on previous studies that showed pronounced antibacterial activity of analgesic‐ and NSAID‐loaded UHMWPE against Staphylococci. Here, we prepared bupivacaine/tolfenamic acid‐loaded UHMWPE and assessed its antibacterial activity against Staphylococcus aureus and Staphylococcus epidermidis. Dual‐drug loaded UHMWPE yielded an additional 1–2 log reduction of bacteria, when compared with single‐drug loaded UHMWPE. Analysis of the drug elution kinetics suggested that the observed increase in antibacterial activity is due to the increased tolfenamic acid elution from dual‐drug loaded UHMWPE. We showed that the increased fractal dimension of the drug domains in UHMWPE could be associated with increased drug elution, leading to higher antibacterial activity. Dual‐analgesic loaded UHMWPE proposed here can be used as part of multi‐modal antibacterial prophylaxis and promises substantial reduction in post‐arthroplasty mortality and morbidity.

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Background Postoperative behavior and allodynia evaluation in rodents are commonly used to confirm preclinical disease models. In contrast, we are investigating pain and functional recovery after traumatic fracture and surgical repair. We created a tibial fracture in the rat and repaired the fracture internally with plating. We hypothesized that histological bone healing would be strongly correlated with functional recovery. Methods Sixteen male Sprague-Dawley rats underwent a metaphyseal transverse osteotomy of the proximal tibia. The defect was repaired by abutting the bone surfaces and fixing them in place using a 5-hole Y-plate with 4 screws. Fracture healing was investigated quantitatively and qualitatively at 2, 4, 6, and 8 weeks using micro-CT imaging, X-ray, and histology. Functional recovery was assessed using video recording and analysis of gait, static weight bearing, hind paw reflex response, and toe spread. Results The micro-CT and histological results demonstrated complete fracture healing at 8 weeks. Specific gait analysis parameters: temporal symmetry, hindlimb duty factor imbalance, phase dispersion, and toe spread showed longitudinal changes commensurate with fracture healing. Conclusions We aim to use this model to evaluate the efficacy of locally administered non-opioid analgesics with long-term effects on healing and function. Our long-term goal is to assess the local efficacy of drug delivery devices in improving post-surgical pain and function. The correlation in this tibia fracture model between bone healing and functional outcomes suggests that post-operative recovery can be monitored, and treatments can be compared using these endpoint measurements.