Group I (early) (n = 15) | Group II (late) (n = 24) | p | ||
Operation year | 2008 | 0 | 4 | 0.196 |
2009 | 1 | 3 | ||
2010 | 5 | 8 | ||
2011 | 2 | 5 | ||
2012 | 7 | 4 |