POPULARIZING SUMMARY Thighbone (femur) fractures are frequently the result of road traffic accidents or other accidents involving great heights and/or speed in young people. The usual way of treating these fractures is by inserting an intramedullary nail into the marrow space of the femur. This way, a connection is made between the two pieces, allowing the healing process of bone to occur. A possible and frequent complication of this type of connection is rotational malalignment. This happens if the two (or more) pieces of bone are not aligned properly, resulting in a wrong stance of the rest of the leg and possibly even physical complaints. Previous research stated that rotational malalignment can be found in 20 to 30% of the patients after a femur fracture treated with an intramedullary nail in the marrow space. The amount or severity of rotational malalignment is expressed in degrees and based on comparison to the healthy leg. Specific questionnaires are used to ask the patient how they feel, which movements hurt and how walking is going. In this study, we wanted to determine how frequently fractures of the mid-femur occur, how often rotational malalignment occurs after inserting an intramedullary nail, and what the impact of rotational malalignment is on patients by performing a literature search. We found that femur fractures occur between 6.5 and 40.8 fractures per 100,000 people yearly. Converted to the entire world’s population, 1 to 3 million people suffer a femur fracture every year. In 533 patients who were treated with an intramedullary nail, we found 87 patients who had a rotational malalignment of more than 15°. So, rotational malalignment occurred in 16.3% of the patients. The results of the questionnaires were more diverse, because not every study used the same ones. Patients with a rotational malalignment of 10° compared to their healthy side, had more knee pain while climbing stairs. If the rotational malalignment resulted in the foot standing 20° or more outwards, the patients’ quality of life was lower. Pain in the hip, upper leg, or knee was worse in patients with a rotational malalignment greater than 15°.   SOCIAL OUTREACH Thighbone (femur) fractures affect 1 to 3 million people every year, despite it being the strongest bone in the human body. The main mechanisms of injury are high energy injuries such as road traffic injuries for the younger population and osteoporotic fractures in the older population. The standard treatment is intramedullary nailing, but an improperly aligned fracture can result in rotational malalignment and rotational malalignment can result in functional complaints. Malalignments >15° were present in 16.3% of the fractures in the studies included in this review. Research on the impact of this injury is necessary, as the people suffering a femur fracture are often young and may be (partially) disabled for the rest of their lives. This in turn results in a socioeconomic and mental burden as the duration of revalidation and inability to work is long. This period can extend even further if the rotational malalignment must be surgically corrected. We think it may be favorable to establish a fixed set of questionnaires for femur fractures. Additionally, more studies on the frequency of rotational malalignment in large patient groups may be beneficial. The end goal should be to develop techniques to lower the incidence of rotational malalignment, which in turn may reduce the socioeconomic and mental burden.