Ankle Fracture Epidemiology in the United States: Patient-Related Trends and Mechanisms of Injury.

Current nationwide epidemiological data regarding ankle fractures are scarce. Such information is important towards better quantifying the mortality associated with such injuries, financial impact, as well as the implementation of preventative measures. This study evaluated the epidemiology of ankle fractures that occurred during a 5-year period. Specifically, we evaluated demographics, mechanism of injury, and disposition. The National Electronic Injury Surveillance System was queried to identify all patients with ankle fractures that presented to US hospital emergency departments between 2012 and 2016. Census data were used to determine the incidence rates of ankle fractures in terms of age, sex, and race. There was an estimated total of 673,214 ankle fractures that occurred during this period, with an incidence rate of 4.22/10,000 person-years. The mean age of patients with an ankle fracture was 37 ± 22.86 (SD) years; 23.5% of ankle fractures occurred in patients aged 10 to 19 years (7.56/10,000 person-years). In addition, 44% of ankle fractures occurred in men (3.81/10,000 person-years), whereas 56% occurred in women (4.63/10,000 person-years). Data on race/ethnicity were available for 71% of the subjects, with incidence rates of 2.85/10,000 person-years for whites, 3.01/10,000 person-years for blacks, and 4.08/10,000 person-years for others. The most common mechanism of injury was falls (54.83%), followed by sports (20.76%), exercise (16.84%), jumping (4.42%), trauma (2.84%), and other (0.30%). For disposition, 81.84% of patients were treated and released, 1.43% were transferred, 16.01% were admitted, 0.59% were held for observation, and 0.13% left against medical advice. The highest incidence of ankle fractures in men occurred in the 10-to-19-years age group, but women were more commonly affected in all other age groups.

Epidermal growth factor differentially affects integrin-mediated adhesion and proliferation of ACL and MCL fibroblasts.

The anterior cruciate ligament (ACL) and the medial collateral ligament (MCL) are two commonly injured structures in the human knee. While the MCL heals post-traumatically, the ACL does not. Since growth factors play a major role in the proliferation phase of wound healing, we compared the differential effects of epidermal growth factor (EGF) on adhesion and proliferation of ACL and MCL fibroblasts. Using a micropipette/micromanipulator system we found that cells subjected to shorter incubation periods (15 minutes) with EGF (5, 10, 50 ng/ml) showed a general increase in adhesion to the extracellular matrix fibronectin while cells subjected to longer incubation periods (4, 6, 10, and 24 hr) with EGF (5 ng/ml) showed decreases in adhesion. For both incubation durations, MCL fibroblasts displayed a greater change in adhesion than ACL fibroblasts, when compared to control. Investigation of integrin expression showed no fluctuation in cell surface expression of the alpha5 subunit of the FN-binding integrin alpha5beta1 for all EGF (5 ng/ml) incubation times. MCL cells showed a significant increase in proliferation upon stimulation with EGF compared to ACL cells when cultured in FN coated wells. The results found in this study help provide a better understanding of EGF's role in adhesion and proliferation, two events that may contribute to the differential healing response between ACL and MCL fibroblasts. Following exposure to EGF, ACL and MCL cells initially respond by increasing their adhesion strength. MCL cells respond to all concentrations of EGF while ACL cells appear to have a threshold concentration after which EGF effects plataeu. After this initial response period (<10 hr) cells exhibit lower adhesion strength and higher proliferation rate. It is possible that the release from FN serves to enhance the ability of the cells to proliferate. These results may aid in understanding the ligament healing process.