The contour threads, which were the only FDA threads approved for threadlifting procedures, are no longer being made by the company. The main reason for this was there palpability or being able to feel them in thinner patients.
They have been replaced by dissolvable sutures made by the same company and marketed as Quill sutures. They dissolve over 6 months, and therefore this is no longer an issue.
Source: Angiotech manufacturing