Poly-L-lactic acid (PLLA) implants have been used for bone fixation for decades. However, upon insertion, they can cause a foreign body reaction (FBR) that may lead to complications. On 15 December 2023, a systematic review was conducted to search for articles on the PubMed, MeSH term, and Scopus databases using the keywords ‘PLLA’ and ‘foreign body reaction’. The articles were reviewed not only for the question of FBR, its severity, and the manifestation of symptoms but also for the type of implant and its location in the body, the species, and the number of individuals included. A total of 71 original articles were identified. Of these, two-thirds reported on in vivo trials, and one-third reported on clinical applications. The overall majority of the reactions were mild in more than half of the investigations. Symptoms of extreme and extensive FBR mainly include osteolysis, ganglion cysts, and swelling. The localization of PLLA implants in bone can often result in osteolysis due to local acidosis. This issue can be mitigated by adding hydroxyapatite. There should be no strong FBR when PLLA is fragmented to 0.5–4 µm by extracorporeal shock wave.

Aims: This study aims to enhance understanding of clinical and radiological consequences and involved mechanisms that led to corrosion of the Precice Stryde (Stryde) intramedullary lengthening nail in the post market surveillance era of the device. Between 2018 and 2021 more than 2,000 Stryde nails have been implanted worldwide. However, the outcome of treatment with the Stryde system is insufficiently reported. Methods: This is a retrospective single-centre study analyzing outcome of 57 consecutive lengthening procedures performed with the Stryde nail at the authors’ institution from February 2019 until November 2020. Macro- and microscopic metallographic analysis of four retrieved nails was conducted. To investigate observed corrosion at telescoping junction, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) were performed. Results: Adjacent to the nail’s telescoping junction, osteolytic changes were observed in bi-planar radiographs of 20/57 segments (35%) after a mean of 9.5 months (95% confidence interval 7.2 to 11.9) after surgery. A total of 8/20 patients with osseous alterations (40%) reported rest and ambulation pain of the lengthened segment during consolidation. So far, 24 Stryde nails were retrieved and in 20 (83%) macroscopic corrosion was observed at the nail’s telescoping junction. Before implant removal 11/20 radiographs (55%) of lengthened segments with these 20 nails revealed osteolysis. Implant retrieval analysis by means of SEM showed pitting and crevice corrosion. EDX detected chromium as the main metallic element of corrosion. Conclusion: Patients are exposed to the risk of implant-related osteolysis of unclear short- and long-term clinical consequences. The authors advocate in favour of an early implant removal after osseous consolidation. Cite this article: Bone Joint Res 2021;10(7):425–436.

Implant-related infections are a significant concern in orthopedic surgery. A novel anti-infective implant coating made of bioresorbable polymer with silver nitrate was developed. A controlled release of silver ions into the vicinity of the prosthesis can be triggered on-demand by extracorporeal shock waves to effectively combat all clinically relevant microorganisms. Microscopy techniques were used to examine the effects of shock wave application on coated titanium discs. Cytotoxicity was measured using a fibroblast proliferation assay. The anti-infective effect was assessed by monitoring the growth curves of three bacterial strains and by conventional culture. Microscopic analysis confirmed surface disruption of the coatings, with a complete release of silver in the focus area after shock wave application. Spectrometry detected an increase in silver concentration in the surrounding of the discs that surpassed the minimum inhibitory concentration (MIC) for both S. epidermidis RP62A and E. coli ATCC 25922. The released silver demonstrated an anti-infective effect, significantly inhibiting bacterial growth, especially at 6% and 8% silver concentrations. Cytotoxicity testing showed decreasing fibroblast viability with increasing silver concentration in the coating, with 6% silver maintaining viability above 25%. Compared to a commonly used electroplated silver coating on the market, the new coating demonstrated superior antimicrobial efficacy and lower cytotoxicity.

Bacterial biofilms on foreign surfaces are considered a primary cause of implant-related infections, which are challenging to treat. A new implant coating was developed, containing anti-infective silver within a biocompatible polymer carrier substance. In addition to its passive effect on the implant surface, highly concentrated anti-infective silver can be released as needed via the application of high-energy shock waves. This intervention could be applied transcutaneously in a clinical setting without the need for additional surgery. We investigated the inhibition of biofilm formation and the effectiveness of eradication after activation of the coating via shock waves in an in vitro biofilm model using Staphylococcus epidermidis RP62A. This was performed via scanning electron microscopy and quantitative microbiology. Additionally, we examined the cytotoxicity of the new coating on normal human fibroblasts and Saos-2 osteoblast-like cells, depending on the silver concentration. All studies were compared to uncoated titanium surfaces Ti6Al4V and a conventional electroplated silver coating. Cytotoxicity toward normal human fibroblasts and Saos-2 osteoblast-like cells increased with higher silver content but remained tolerable at 6%. Compared to uncoated Ti6Al4V and the electroplated silver coating, the new coating with a silver content of 4% and 6% exhibited a significant reduction in adherent bacteria by a factor of approximately 1000. This was also evident via microscopic examination of the surface morphology of the biofilms. Furthermore, following shock wave activation, no bacteria were detectable on either the implant or in the surrounding fluid after a 24 h period.

The widespread prevalence of periprosthetic joint infections (PJIs) poses significant challenges in orthopedic surgeries, with pathogens such as Staphylococcus epidermidis being particularly problematic due to their capability to form biofilms on implants. This study investigates the efficacy of an innovative silver nitrate-embedded poly-L-lactide biopolymer coating designed to prevent such infections. The methods involved applying varying concentrations of silver nitrate to in vitro setups and recording the resultant bacterial growth inhibition across different serum environments, including human serum and various animal sera. Results highlighted a consistent and significant inhibition of S. epidermidis growth at all tested concentrations in each type of serum without adverse interactions with serum proteins, which commonly compromise antimicrobial efficacy. This study concludes that the silver nitrate-embedded biopolymer coating exhibits potent antibacterial properties and has potential for use in clinical settings to reduce the incidence of PJIs. Furthermore, the findings underscore the importance of considering serum interactions in the design and testing of antimicrobial implants to ensure their effectiveness in actual use scenarios. These promising results pave the way for further research to validate and refine this technology for clinical application, focusing on optimizing silver ion release and assessing biocompatibility in vivo.

To solve the issue of implant-associated infections, an antibacterial biocompatible multilayer coating was developed. For the approval of such a coating system as a medical device, the characterization of its mechanical and tribological properties is required. Since none of the existing test standards is fully applicable to the present coating system, a testing concept was developed to investigate the wettability, topography, morphology, thickness, hardness, Young’s modulus, adhesion strength and tribological characteristics of the multilayer coating.