Influence of the intramedullary nail preparation method on nail's mechanical properties and degradation rate Anna Morawska-Chochół a, ⁎, Jan Chłopek a , Barbara Szaraniec a , Patrycja Domalik-Pyzik a , Ewa Balacha a , Maciej Boguń b , Rafael Kucharski c,d a AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Department of Biomaterials, al. A. Mickiewicza 30, 30-059 Krakow, Poland b Lodz University of Technology, Faculty of Material Technologies and Textile Design, Department of Material and Commodity Sciences and Textile Metrology, ul. Żeromskiego 116, 90-924 Lodz, Poland c Association “HEALTH”, ul. Kosciuszki 191, 40-525 Katowice, Poland d IEE-Group, Hannover, Germany abstract article info Article history: Received 28 July 2014 Received in revised form 5 November 2014 Accepted 23 February 2015 Available online 25 February 2015 Keywords: Intramedullary nails Biodegradable composites Injection moulding Hot pressing Forming from solution When it comes to the treatment of long bone fractures, scientists are still investigating new materials for intramedullary nails and different manufacturing methods. Some of the most promising materials used in the field are resorbable polymers and their composites, especially since there is a wide range of potential manufacturing and processing methods. The aim of this work was to select the best manufacturing method and technological parameters to obtain multiphase, and multifunctional, biodegradable intramedullary nails. All composites were based on a poly(L-lactide) matrix. Either magnesium alloy wires or carbon and alginate fibres were introduced in order to reinforce the nails. The polylactide matrix was also modified with tricalcium phosphate and gentamicin sulfate. The composite nails were manufactured using three different methods: forming from solution, injection moulding and hot pressing. The effect of each method of manufacturing on mechanical properties and degradation rate of the nails was evaluated. The study showed that injection moulding provides higher uniformity and homogeneity of the particle-modified polylactide matrix, whereas hot pressing favours applying higher volume fractions of fibres and their better impregnation with the polymer matrix. Thus, it was concluded that the fabrication method should be individually selected dependently on the nail's desired phase composition. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The obvious advantages of intramedullary osteosynthesis, such as: a good stabilization of bone fragments guaranteeing elasticity of the fixation, minimal damage of the surrounding tissue and low surgical risk, make it a significant and valuable method of long bone fracture treatment [1–6]. Metals are frequently used for intramedullary nails, e.g. stainless steel and titanium alloys [7]. Metal implants, however, have to be removed from the organism after they have fulfilled their task. Therefore, a patient needs another surgical intervention, which involves negative medical and financial consequences. Moreover, although the mechanical strength of metallic nails is fully satisfactory for bone stabilization (the bending strength of stainless steel 316L is in the range of 240–770 MPa), their Young's modulus is too high in relation to the bone's (E = 193 GPa for 316L and E = 110–114 GPa for Ti6Al–4V, while E = 10–40 GPa for bone) [8,9]. This significant dis- proportion causes stress shielding and inadvisable changes in natural bone biomechanics, that can further lead to bone resorption and cause bone fracture [10]. Taking all these factors into account, it is clear that resorbable nails can be endowed with more desired mechanical proper- ties creating better internal fixation devices. In the field of resorbable biomaterials, there is a large selection of medically approved degradable polymers [11–15]. However, due to the low strength of the pure polymers, a polymer-based reinforced composite would be more appropriate for use in intramedullary nails. The greatest advantage of composites is the fact that their properties can be easily tailored to required specifications therefore, it is possible to obtain composite nails of mechanical parameters fitted to the bone properties. A gradual transfer of load from the biodegradable nails to the bone, without stress shielding, should allow proper bone healing with the added benefit of no necessary additional surgery for implant removal. One of the first attempts at applying resorbable materials for intramedullary osteosynthesis was undertaken by Saikku-Bäckström et al. in 2004 [16]. The tests involved using a copolymer of 96% L- lactide and 4% D-lactide (PLA96). The work was performed using Materials Science and Engineering C 51 (2015) 99–106 ⁎ Corresponding author. E-mail address: morawska@agh.edu.pl (A. Morawska-Chochół). http://dx.doi.org/10.1016/j.msec.2015.02.043 0928-4931/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec