Is just one screw really enough? Single- versus double-screw in the medial malleolus in supination-external rotation ankle fractures: A comparative biomechanical study using partially threaded cancellous screws.

OBJECTIVE: The aim of this study is to investigate stiffness and the maximum load to failure values of single- and double-screw fixation of oblique medial malleolus fractures using partially threaded cancellous screws. Our hypothesis is that single-screw fixation of medial malleolus fractures after SER injuries provides similar stiffness when compared with double-screw fixation. DESIGN: Biomechanical study. METHODS: Twelve composite polyurethane synthetic right distal tibiae were used in the experiment. Oblique fractures of the medial malleolus were created with a band saw using a custom-made osteotomy guide to standardize the cuts in all models. Bone models were randomly separated into two groups and fixed with one (n = 6) or two (n = 6) 4.0 mm partially threaded cancellous screws placed perpendicular to the fracture line. These were tested by applying an offset axial tension at 10 mm/minute up to maximum load displacement, defined as subsidence of the medial malleolus fragment. Maximum load to failure was determined for the groups at the point where the curve ceased to be linear and suffered an inflection. Force versus displacement curves were obtained and recorded. The student's t-test for independent samples was used to compare stiffness (N / mm) and maximum load (N) between experimental groups, with a p value of < 0.05. RESULTS: There were no significant differences in stiffness (p = 0.290) and maximum load (p = 0.191) among the two fixation constructs. Mean stiffness was 62.26 (±SD 21.11) N/mm for double-screw fixation group and 48.24 (±SD 22.40) N/mm for single-screw fixation group. Mean maximum load was 387.83 (±SD 115.78) N for double-screw fixation group and 306.64 (±SD 81.97) N for single-screw fixation group. CONCLUSION: Fixation with one 4.0 mm partially threaded cancellous screw was not shown to be biomechanically inferior to fixation with two 4.0 mm partially threaded cancellous screws in an oblique fracture of the medial malleolus, supporting previous clinical studies that have shown that one screw is sufficient for fractures of the medial malleolus.

Partner responsiveness moderates the relation between COVID-19-related stressors and changes in mood during the pandemic.

The COVID-19 pandemic has created an unusually stressful situation for many people around the world. Due to the restrictions, many have been isolated in their homes, and having a responsive partner may have become even more important. The present study aimed to investigate (1) whether there were any differences in social and work-related stressors and changes in negative mood during the COVID-19 pandemic as a function of marital status, and (2) whether perceived partner responsiveness can attenuate the associations between COVID-19-related stressors and changes in negative mood. The participants were 2,400 Brazilian adults recruited via the Internet, using a virtual sampling strategy. They were assigned to three distinct groups based on their relationship status. The results showed that a relatively large proportion of the sample reported increased levels of negative mood, and that married/cohabitating couples reported low levels of negative change in mood compared to single participants. We also found that partner responsiveness attenuated the association between stress and mental health, but only for people who were dating. Our study contributes new insights by showing that effects on mental health during the COVID-19 pandemic are dependent on relationship type and perceived partner responsiveness.