Can Prophylactic Cables Stop Crack Propagation in Revision Arthroplasty: A Biomechanical Study.

BACKGROUND: Intraoperative femur fractures are a common complication of revision hip arthroplasty. This study examined the use of a prophylactic cable in stopping a crack from propagating beyond the cable. METHODS: Seventy sheep femora were prepared. A 5-mm vertical incision was performed. Using a force-controlled materials testing machine, a Wagner shaft was advanced until a crack occurred. Cracks were visualized with green ink. In the first part, the control group without any cable (n = 10) was compared with polyethylene (n = 15) and single CoCr cable (n = 15) groups. The cables were positioned 15 mm distal to the osteotomy. In the second part, three different CoCr configurations were compared, single-wrapped (n = 15), double-wrapped (n = 125), and two separate cables at 10 and 15 mm distal to the osteotomy (n = 15). RESULTS: The polyethylene cable stopped only 3 of 15 cracks (20%), whereas the CoCr cable stopped 11 of 15 cracks (73%) (P = .009). The force needed to initiate the crack between the different groups was not significant. Twelve (80%) of 15 cracks were stopped at the level of the cable with two separate CoCr cables and 15 (100%) of 15 cracks with a double-wrapped cable (P = .11). CONCLUSION: This study demonstrated that an elastic cable is not suitable for preventive cabling. The force required to form a crack is not improved with the use of a prophylactic cable placed 10-15 mm below the osteotomy. While the results on the different configurations were not conclusive, the double-wrapped cable was able to stop all cracks from progressing distally.

Problem-solving in virtual environment simulations prior to direct instruction for differential diagnosis in medical education: An experimental study.

Background: Despite acquiring vast content knowledge about the functioning of the human body through university teaching, medical students struggle to transfer that knowledge to one of the core disciplinary practices - differential diagnosis. The authors aimed to overcome this problem by implementing computer-based virtual environment simulations in medical education courses. Methods: In an experimental study, the authors compared problem-solving in medical computer-based virtual environment simulations prior to instruction with an instruction-first approach. They compared the effects on isomorphic testing and transfer performance of clinical knowledge and clinical reasoning skills as well as evoked learning mechanisms. The study took place in spring 2021 with undergraduate medical students in the scope of a medical trajectory course. Due to Corona-Virus-19 measures participants completed all study activities remotely from home. Results: The authors did not find any learning activity sequence to be superior to the other. However, when looking at the two learning activities individually, they found that problem-solving in computer-based virtual environment simulations and direct instruction might be equally effective for learning content knowledge. Nevertheless, problem-solving in computer-based virtual environment simulations with formative feedback might be more effective for learning clinical reasoning skills than mere instruction. Conclusions: The findings indicate that problem-solving in computer-based virtual environment simulations might be more effective for learning clinical reasoning skills than mere theoretical instruction. The present study has a high level of ecological validity because it took place in a realistic setting where students had to perform all learning and testing tasks autonomously.