Recruitment centres and estimated recruitment based on number of surgeries performed annually. The hospitals are already recruiting patients
| Centre | Estimated n | % recruited |
| Danderyd Hospital | 8000 | 18% |
| Hässleholm/Kristianstad | 10 000 | 22% |
| Huddinge Hospital | 6000 | 13% |
| Akademiska Hospital | 10 000 | 22% |
| Ortho Centre | 3000 | 7% |
| Umeå | 8000 | 18% |
| Total sample size | 45 000 | 100% |