"The condition served as a beachhead for having hospital visits."
"The condition served as stepping stone to hospital visits."
"The condition served as a beachhead for having hospital visits."
"the condition" 「その病状」
"served as a beachhead" 「足がかりとなった」
"having hospital visits"「病院を受診する」
"beachhead" より "stepping stone" の方が適切と思います
"The condition served as stepping stone to hospital visits."
"stepping stone" 「足がかり」
[これも](https://eikaiwa.dmm.com/uknow/questions/469/)役に立つかもしれませんので是非クリックしてください。