+0
Hello,
Can you please tell me if the meaning is clear?

TWG and CS groups were divided into four subgroups according to the four intended positions of the chest tube tip (target position in pleural cavity): first (back-down right), second (front-up-right), third (front-up-left), fourth (back-down-left).

Thank you
Comments  
.
Do you need the numbers? They add to the confusion.

The TWG and CS groups were divided into four subgroups according to the four intended positions of the chest tube tip (target position in pleural cavity): back-down-right, front-up-right, front-up-left, and back-down-left.
.
Ok, thank you.
Students: Are you brave enough to let our tutors analyse your pronunciation?
Should I use definite article with TWG and CS?
.
Here, the noun is 'groups', not TWG and CS. Or do you mean generally? Remind me what they mean, and I'll give you my recommendation.
.
I mean generally.
TWG-targeted wire guided technique

CS-classical surgical technique
Teachers: We supply a list of EFL job vacancies
.
Then they are both countable 'techniques', so usually you would want the article.
.
Thanks.