Poor patient selection - some patients will 'hammer' their graft or not co-operate with rehab. They may be young, and if they want to return to high risk sports they need to know the risks and maybe attend a FIFA programme
Surgeon factors - tunnel position in the notch needs to be optimal
Graft type and thickness - autograft is best. Graft needs to be 8mm or more (but don't overstuff the notch)
Graft tensioning and fixation - tensioning is important (25-30 Newtons). Most modern fixation devices are acceptable, but the endobutton needs to be flush on the bone
?Failure to preserve the ACL remnant - preserving the remnant may help in healing and proprioception