Update on Failure Analysis of Implants in ACL Surgery: Technical Failure or Fate?

Reasons for failure of anterior cruciate ligament (ACL) reconstructions are manifold and require a multifactorial explanatory approach. In addition to technical failures, many modifiable and non-modifiable risk factors for a new ACL injury have to be considered. Technical failures primarily include non-anatomical tibial and femoral tunnel position. In comparison to the transtibial drilling technique, the tibial tunnel-independent technique results in a more anatomical position of the femoral tunnel and should therefore be preferred. One can differentiate between non-modifiable and modifiable risk factors. At the same time, the combination of more than one risk factor increases the risk of injury significantly. Non-modifiable risk factors include genetic predisposition, female sex, young age and ligament hyperlaxity. Young age at the time of the first injury is the most important risk factor for graft failure. Modifiable risk factors include high body mass index (BMI), deficits in jump landing mechanics, a steep posterior tibial slope and narrow intercondylar notch width. Neuromuscular training or additional surgical procedures modify these risk factors and reduce the probability of further injuries. A high tibial osteotomy (HTO) is the surgical procedure of choice for a reduction in the posterior tibial slope and anterior tibial translation. In case of a tibial slope over 12°, this procedure should be considered. In revision anterior cruciate ligament reconstructions with remaining anterolateral rotatory instability, additional lateral extraarticular tenodesis should be taken into account. This is also recommended for patients participating in pivoting sports, having concomitant hyperlaxity or additional injury of peripheral structures with insufficiency of the ACL. In addition, the surface of the pitch can be modified and thus influence the risk of an ACL injury. In summary, a substantiated failure analysis is required to initiate specific and individualised therapy - not only in the case of ACL rerupture. These factors should already be considered in risk assessment during patient information.