Via Yale News: https://news.yale.edu/2021/05/25/all-favor-test-aortic-aneurysms-raise-your-hand 

Some excerpt of it:

"The test is simple: Holding up one hand and keeping the palm flat, the patient flexes their thumb as far as possible across the palm. If the thumb crosses beyond the far edge of the flat palm, the patient may be harboring a hidden aneurysm.

Being able to move the thumb in that way is an indication that a patient’s long bones are excessive and their joints are lax — possible signs of connective tissue disease throughout the body, including the aorta.

The researchers said it is important to emphasize that not everyone who tests positive is an aneurysm carrier. Also, they noted, aneurysms often take decades to progress to the point of rupture and a positive test is not cause for panic.

For the study, the researchers gave the test to 305 patients undergoing cardiac surgery for a variety of disorders, including aortic aneurysms. “Our study showed that the majority of aneurysm patients do not manifest a positive thumb-palm sign, but patients who do have a positive test have a high likelihood of harboring an aneurysm,” Elefteriades said."