| Author | Year | Hips | Follow up (years) | Impingement sign (%) |
| Siebenrock et al. [22] | 1999 | 75 | 11 | 29 |
| Steppacher et al. [23] | 2008 | 58 | 19 | 38 |
| Ziebarth et al. [8] | 2010 | 46 | 3.5 | 47 |