Background: CrossFit is one of the fastest growing “high-intensity functional training” methods in recent years. Due to the very demanding motion sequences and high loads, it was initially assumed that there was an extremely high risk of injury. However, studies have shown that injury rates are given between 0.74–3.3 per 1000 h of training, which is not higher than in other individual sports such as weightlifting. The purpose of the study was to estimate the type of pain symptoms that are directly related to CrossFit, to estimate the frequency of injuries that occur within a population of recreational CrossFit athletes, and, finally, to identify the factors influencing the frequency of pain during CrossFit training. Methods: A total of 414 active CrossFit athletes completed an online survey inclusive of 29 items focusing on individual physical characteristics and training behavior, as well as simultaneous or previously practiced sports. Results: There was a significantly higher proportion of knee pain in athletes who had previously or simultaneously played another sport (p = 0.014). The duration, intensity, or type of personal training plan developed, along with personal information such as age, gender, or BMI, had no significant influence on the pain data. We could not find any significant variance between the groups that we formed based on the differently stated one-repetition max (RMs). There were differences in athletes who stated that they did specific accessory exercises for small muscle groups. Above all, athletes performing exercises for the hamstrings and the gluteus medius indicated fewer pain symptoms for the sacro-iliac joint (SIJ)/iliac and lower back locations. Conclusions: It is important not to see CrossFit as a single type of sport. When treating a CrossFit athlete, care should be taken to address inter-individual differences. This underlines the significant differences of this study between the individual athletes with regard to the ability to master certain skills or their previous sporting experience. The mere fact of mastering certain exercises seems to lead to significantly more pain in certain regions. In addition, there seems to be a connection between the previous or simultaneous participation in other sports and the indication of pain in the knee region.

Background: Intramedullary limb lengthening has become more popular in the past two decades. This study aimed to investigate the mechanical properties of the various intramedullary lengthening devices currently available to orthopedic surgeons. Materials and Methods: A load cell connected to an electromechanical tensile testing machine was used to apply a bending force to nine intramedullary lengthening nails: Albizzia Ø 11 mm, intramedullary skeletal kinetic distractor Ø 10.7 mm, Precice Ø 10.7 mm, G-Nail Ø 13 mm, and Betzbone Ø 9 mm to Ø 13 mm. The force needed to deform each nail by 0.01 mm, 0.05 mm, 1 mm, and 3 mm was measured and compared. Results: The nail with the smallest diameter (Betzbone Ø 9 mm) needed the least force to deform. The nails with the biggest diameter (G-Nail Ø 13 mm and Betzbone Ø 13 mm) needed the most force to deform. Comparing similar-sized implants, nails manufactured from surgical steel or cobalt-chrome were more resistant to plastic deformation than titanium nails. Conclusion: Intramedullary lengthening device's ability to resist bending deformation depends on the diameter and material of the nail. Surgical steel and cobalt-chrome alloy nails showed higher resistant to plastic deformation when compared to titanium nails.

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