IntroductionOsteosynthesis of femoral neck fractures (FNFs) is an important treatment option, especially for younger patients. We aimed to assess the rate of early implant-related complications in FNF osteosynthesis using the Femoral Neck System (FNS).Patients and methodsConsecutive patients diagnosed with displaced or nondisplaced FNFs were treated with FNS in this prospective, observational, multicenter investigation. Patients were followed up for minimally 3 months and up to 12 months if radiologic bone union and no pain was not achieved beforehand. Predefined treatment-related adverse events (AEs, defined as implant failure, loss of reduction, iatrogenic fractures, deep infection, and surgical revision), radiologic bone union, and patient-reported Harris hip score (HHS) and EQ-5D-5L index score were assessed.ResultsOne hundred and twenty-five patients were included in the study. Thirty-eight (30.4%) fractures were displaced (Garden III and IV), and 37 (29.6%) were vertical fractures (Pauwels type III). Predefined treatment-related AE rate at 3 months was 8 patients, 6.4% (95% CI, 2.8–12.2), and at 12 months, 11 patients, 8.8% (95% CI, 4.5–15.2). Cumulative incidences of bone union were 68% at 3 months, 90% at 6 months, and 98% at 12 months. The mean changes of HHS and EQ-5D-5L index score between preinjury and at 12 months were -7.5 (95% CI, [ – 21.1] to [6.2]) and  – 0.03 (95% CI, [ – 0.21] to [0.15]), respectively; neither were statistically significant.ConclusionThe current study on osteosynthesis of FNFs with the FNS resulted in treatment-related complication rates of 6.4% (95% CI, 2.8–12.2) at 3 months and 8.8% (95% CI, 4.5–15.2) at 12 months. On average, patients returned to preinjury function and quality of life. The current study may also indicate that the conventional wisdom of treating stable FNF in patients aged between 60 and 80 years with osteosynthesis may need to be reconsidered.RegistrationThe study is registered with ClinicalTrials.gov (registration number: NCT02422355).