Development of a facile fluorophosphonate-functionalised titanium surface for potential orthopaedic applications.

BACKGROUND: Aseptic loosening of total joint replacements (TJRs) continues to be the main cause of implant failures. The socioeconomic impact of surgical revisions is hugely significant; in the United Kingdom alone, it is estimated that £137 m is spent annually on revision arthroplasties. Enhancing the longevity of titanium implants will help reduce the incidence and overall cost of failed devices. METHODS: In realising the development of a superior titanium technology, we exploited the natural affinity of titanium for phosphonic acids and developed a facile means of coating the metal with (3S)1-fluoro-3-hydroxy-4-(oleoyloxy)butyl-1-phosphonate (FHBP), a phosphatase-resistant analogue of lysophosphatidic acid (LPA). Importantly LPA and selected LPA analogues like FHBP synergistically cooperate with calcitriol to promote human osteoblast formation and maturation. RESULTS: Herein, we provide evidence that simply immersing titanium in aqueous solutions of FHBP afforded a surface that was superior to unmodified metal at enhancing osteoblast maturation. Importantly, FHBP-functionalised titanium remained stable to 2 years of ambient storage, resisted ∼35 kGy of gamma irradiation and survived implantation into a bone substitute (Sawbone™) and irrigation. CONCLUSION: The facile step we have taken to modify titanium and the robustness of the final surface finish are appealing properties that are likely to attract the attention of implant manufacturers in the future. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: We have generated a functionalised titanium (Ti) surface by simply immersing Ti in aqueous solutions of a bioactive lipid. As a facile procedure it will have greater appeal to implant manufacturers compared to onerous and costly developmental processes.

Acetic Acid as Part of a Debridement Protocol During Revision Total Knee Arthroplasty.

BACKGROUND: Thorough debridement is mandatory in revision for infected total knee arthroplasties (TKA). We investigated a novel adjuvant chemical debridement strategy using acetic acid (AA) that seeks to create a hostile environment for microorganisms. We report the first orthopedic in vivo series using an AA soak in infected TKAs. We also investigated the in vitro efficacy of AA against bacteria isolated from these knees. METHODS: Twenty-three patients with infected TKA were treated with a standard debridement protocol and chemical debridement with a 20-minute AA soak. In parallel, bacteria from infected TKAs were cultured for in vitro susceptibility testing with AA solutions of different concentrations to understand its potential mechanism of action. RESULTS: Intraoperatively, there were no physiological responses during the AA soak or on release of the tourniquet. Postoperatively, there was no increase in analgesic requirements or wound or soft-tissue complications. Clinical follow-up continued for 24 months to monitor recurrent infection. In vitro, zones of inhibition were formed on less than 40% of the organisms, demonstrating that AA was not directly bactericidal against the majority of the isolates. However, when cultured in a bacterial suspension, AA completely inhibited the growth of the isolates at concentrations as low as 0.19% vol/vol. CONCLUSION: This study has shown that the use of 3% AA soak, as part of a debridement protocol is safe in patients. While the exact mechanism of action is yet to be determined, AA concentrations as low as 0.19% vol/vol in vitro are sufficient to completely inhibit bacterial growth.