Rotational knee stability is a topic with great interest among Anterior Cruciate Ligament (ACL) Reconstruction experts. Previous papers have questioned whether current ACL reconstruction techniques may provide adequate rotational stability in all ACL-deficient individuals, considering their broad spectrum of clinical presentations (Logan 2004, Ristanis 2005). Persistent rotational instability after standard ACL reconstruction have been extensively described, and it has been shown to keep straight correlation with worse outcomes post-operatively (Chouliaras 2007, Kocher 2004). Besides, lack of knee stability could lead to further chondral and meniscal lesions, which could enhance development of knee osteoarthritis (Stergiou 2007).

This discussion has gained increased attention after recent publications regarding the Anterolateral ligament (ALL), described as a structure whose lesion seems to worsen rotational instability when associated to ACL ruptures. (Claes 2013, Helito 2013, etc). Segond first described this ligament in 1897 as a "resistant fibrous band" located in the anterolateral knee compartment with a singular characteristic of tensioning in forced internal rotation (Segond 1879). Afterwards, some authors referred to this structure as a capsular thickening (Hughston 1976). More recently, various anatomical publications brought up this controversy, defining the ALL as a distinct ligament (Claes 2013, Dodds 2014, Helito 2015). Biomechanical data have shown straight correlation between its rupture and worsening of rotational stability, defined with a presence of an obvious positive pivot shift test (Claes 2013, Monaco 2012). Lack of consensus still exists regarding the validity of these findings, but many authors proposed the association of ACL and ALL reconstruction in selected ACL-deficient individuals, considering the theoretical biomechanical advantage of this procedure in promoting combined anteroposterior and rotational stability (Sonnery-Cottet 2015, Sonnery-Cottet 2017, Dodds 2014, Marcacci 2009). In a recent meta-analysis of randomized controlled trials, isolated ACL reconstruction techniques were compared to combined ACL and extra-articular reconstruction techniques and, although Lachman and pivot shift tests were superior in the combined ACL reconstruction group, functional scores were similar (Rezende 2015). Knee stiffness and infection, were also similar between groups, despite previous publications suggesting increased rates in the combined procedure (Anderson 2001, Sonnery-Cottet 2011). However, considering the lack of improvement of knee scores tests, the authors concluded it is still uncertain whether this increased stability surpasses the morbidity of adding an extra-articular procedure (Rezende 2015). In contrast to the obsolete extra-articular techniques included in the latter meta-analyses, anatomical ALL reconstruction techniques have been proposed to better replicate the anatomy of the anterolateral compartment (Sonnery-Cottet 2015). Promising results have been published in a recent prospective cohort study comparing combined ALL and ACL reconstruction with isolated ACL reconstruction techniques, using either hamstrings and bone-patellar-tendon bone grafts. Re-rupture rates were 3.1 times fold less in combined ACL and ALL procedure compared to isolated ACL with hamstrings and 2.3 times fold less compared to isolated ACL with bone-patellar-bone graft . The percutaneous ALL reconstruction technique described in this study not just reproduces more reliably the anatomy of the anterolateral compartment, but it is also less invasive diminishing the morbidity associated with the non-anatomic extra-articular reconstruction techniques, such as the iliotibial band tenodesis (Sonnery-Cottet 2017).

Many controversy still predominates among ACL experts not just regarding ALL in vitro studies, but also the debate about the reliability of the combined ACL and ALL procedure when bringing it to the clinical setting (Guenther D 2016, Kittl C 2016). Concerns have been raised about some aspects of the combined ACL and ALL procedure, in particular its theoretical potential in leading to an excessive knee constriction, as demonstrated in some biomechanical papers (Schon JM 2016). Experts opinions diverge about the potential long-term consequences of the combined ACL and ALL procedure; while defenders state that improved rotational instability should minimize degenerative consequences of a "sub-optimal" knee joint stability supposedly provided by an isolated intra-articular reconstruction, many other surgeons argue that knee osteoarthritis might the evolution of the abnormal kinematics of an overconstrained knee (Inderhaug E 2017, Schon JM 2016, Sonnery-Cottet B 2017). In order to resolve such lack of consensus, clinical trials with high level of evidence should be the priority in this field, with a long term follow-up, aiming to compare functional scores, knee stability tests and complications rates between isolated ACL and combined ACL and ALL reconstruction techniques.

So, the present study aims to compare the effectiveness of the combined ACL and ALL reconstruction with isolated ACL reconstruction in individuals with high risk of ACL re-rupture, through a randomized controlled trial.