Questioning the routine metal implant removal after bone fracture healing has increased. One of the main indications for removal is metal weakening in biological bone healing conditions, in addition to reports about its breakage even prior to bone healing. The aim of this study is to investigate the mechanical properties of osteosynthesis plates made out of standard surgical stainless steel in simulated biological conditions. Implants made out of 316L stainless steel were kept for one year in simulated body fluid (SBF). We analysed 48 plates made out of standard surgical stainless steel that were divided in four groups. One was the control group and the remaining were immersed in solutions with various pH values according to pH changes during bone fracture healing. The immersed plates were tested mechanically through one year, and those in the control group at the beginning of the study. During one year microstructural changes of the immersed plates were examined five times using a scanning electron microscope (SEM), and only once in the control group. There were significant microstructural pitting corrosion changes after six months and after one year in all plates that were in simulated biological conditions, regardless of the group pH value. Static and dynamic mechanical plate loading tests were performed one year after storage in solutions with various pH values. Following the complete mechanical testing no statistically significant changes were found between groups kept in simulated biological conditions for one year and the control group. The study showed no changes in the mechanical properties of the investigated implants regardless of significant microstructural changes as a consequence of pitting corrosion in simulated biological conditions, which precludes the probability of implant weakening and indication for its removal one year after fracture fixation.