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The additive manufacturing of low elastic modulus alloys that have a certain level of porosity for biomedical needs is a growing area of research. Here, we show the results of manufacturing of porous and dense samples by a laser powder bed fusion (LPBF) of Ti-Nb alloy, using two distinctive fusion strategies. The nanostructured Ti-Nb alloy powders were produced by mechanical alloying and have a nanostructured state with nanosized grains up to 90 nm. The manufactured porous samples have pronounced open porosity and advanced roughness, contrary to dense samples with a relatively smooth surface profile. The structure of both types of samples after LPBF is formed by uniaxial grains having micro- and nanosized features. The inner structure of the porous samples is comprised of an open interconnected system of pores. The volume fraction of isolated porosity is 2 vol. % and the total porosity is 20 vol. %. Cell viability was assessed in vitro for 3 and 7 days using the MG63 cell line. With longer culture periods, cells showed an increased cell density over the entire surface of a porous Ti-Nb sample. Both types of samples are not cytotoxic and could be used for further in vivo studies.

Introduction Reconstruction of the anterior cruciate ligament (ACL) is one of the most common surgical procedures around the knee. Despite good long-term outcomes in general, thousands of revisions after ACL reconstruction are performed annually in the world due to graft failures, repeated injuries, technical errors, disorders in ligamentization process or inadequate rehabilitation. The aim of the study was to evaluate the current evidence and describe the relevant clinical features of planning and performing revision ACL reconstruction. Materials and methods A search was conducted for English- and Russian-language publications in the electronic databases PubMed and e-LIBRARY for the period from 2000 to 2020 using the keywords: anterior cruciate ligament, ACL, revision, re-reconstruction, re-rupture. Among 572 publications, 107 corresponded to the study topic. Based on the inclusion criteria (more than 50 reported cases; follow-up more than 2 years; homogeneous groups of patients; assessment with knee function scores; application of various imaging options), 31 articles were included in this review. There were no Russian studies that met the above-mentioned criteria. Results and discussion The analysis of the literature identified four clinically relevant features in the treatment of patients with failures of ACL reconstruction: criteria and principles for the implementation of a one- or two-stage approach; additional features of the revision ACL reconstruction; determination of the optimal graft type. Conclusion Most of the revision ACL reconstructions can be performed at one stage, combined with bone grafting if needed. For a successful treatment outcome, in some cases, correction of frontal and sagittal deformity of the lower limb, management of the injury to other knee joint stabilizers, to cartilage or menisci is required. Surgeons’ preferences in the choice of plastic material has shifted to autografts with bone blocks, or allografts, especially if reconstruction of several stabilizers is necessary.