Even though ACL reconstruction is a very widely used operation with a very satisfactory success rate which allows the majority of active patients involved in sports activities to resume their pre-operative levels, the persistence of a certain rotatory joint laxity might produce subsequent meniscal or chondral damage leading to a clear degenerative arthritic disease [
24]. Even though the pivot-shift assessment has always been part of the evaluation scoring scales used, it has often been underestimated; only within the last few years has this topic come back to scientific attention thanks to Freddi Fu’s studies on the functional anatomy of the ACL, on its two distinct bundles and, most of all, on failure of the single-bundle reconstruction to restore exact joint stability especially in regard to internal rotation. As a result, many surgeons, with the aim of improving their success rates, have in turn started using the double-bundle reconstruction of the ACL. In recent years, and in particular in the first years of the third millennium, many clinical and laboratory studies have been published on the advantages of reconstruction of the two bundles, thus supporting Fu’s theory [
25‐
27]. In particular, clinical studies with a minimum follow-up of 2 years in which double-bundle reconstructions were used showed better results than the single-bundle, both in terms of knee stability and in terms of recurrence rate. Moreover, other studies, such as the one by Robinson et al. [
28] on cadaver knees with the use of a navigation system, further provided objective data about how, in ACL reconstructions, the AM and PL bundles act differently in stabilizing the knee, particularly during the pivot-shift test, where the PL bundle is important in controlling not only anterior laxity toward knee extension, but also the rotational component. In net contrast with what was reported by the above mentioned authors, in a similar study we performed on cadaver knees with the use of a navigation system, we found that the further addition of the PL bundle to an AM single-bundle reconstruction did not provide any additional stability to the knee in regard to internal rotation. How might these different results be explained since the methodologies of the studies were similar? The explanation may likely be in the different surgical way of reconstructing the AM bundle: in fact, in Robinson’s study, the AM bundle was positioned slightly more anterior and vertical than in our study, whereas we tried to place the femoral insertion, approached with an out-in technique, more horizontal and as posterior as possible, thus in accordance with the actual anatomy of the ACL. This is a very important topic which deserves deeper examination [
29]. Since the beginning of the reconstruction of the ACL with open techniques, it was mandatory for the surgeon to scrupulously respect the anatomy of the ACL with a very posterior positioning of the femoral insertion. Since this goal could not be reached by drilling the femoral condyle from the articular joint, surgeons started using the out-in technique. After a few years, with the advent of arthroscopic techniques, the majority of surgeons preferred to perform less invasive techniques (single-incision techniques), performing trans-tibial femoral tunnel drilling, often resulting in a non-anatomical positioning of the ACL. It seems as if, despite the advantages provided by the scope, the arthroscopists preferred mini-invasiveness over respect of the anatomy and function.
However, since rotatory instability is a complex phenomenon not simply dependent on the ACL rupture or the anatomical reconstruction, other hypotheses have been proposed to correct this type of instability. Among these, an important aspect is represented by the peripheral plasties [
30,
31], whose biomechanical role in controlling rotational instability and the pivot-shift has been widely proven, even in recent studies published by our group: internal rotation was better restored in cases in which the anatomic ACL reconstruction was performed along with a peripheral plasty than in cases treated with a double-bundle technique [
32]. More recently, Colombet et al. [
33] did not reach the same conclusions as us: however, they did not put any tension on the lateral sling, thus losing a big part of the efficacy of the technique itself. Even more controversial is the clinical effectiveness of the peripheral plasties in long-term follow-up, even though Zaffagnini et al. [
34], in assessing three groups of patients treated with hamstrings (STG), bone-patellar-tendon-bone (BPTB) and ST plus peripheral plasty, obtained the best results in the third group. In our experience we found peripheral plasty useful in patients with severe rotatory instability (+++ pivot-shift), in women and in cases of revision.
A complete lesion of the ACL often causes a rotatory instability of the knee detectable with the pivot-shift test. During this complex phenomenon the tibia tends to internally rotate with respect to the femur, thus changing its rotational fulcrum which moves medially closer to the MCL, with following anterior translation of the external tibial plateau. The severity of the pivot-shift, commonly scored in three degrees, essentially depends on the amount of constitutional tibial rotation and on the presence of concomitant associated lesions, such as the ALFTL and the external meniscus. In order to obtain the best rotatory stability, the ACL reconstruction must be performed accurately, reproducing its anatomical positions (either single- or double-bundle). Non-anatomical reconstructions are basically erroneous. Peripheral plasties may contribute to better control of rotator instability and may be indicated in selected types of patients.