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Combined Anterolateral Complex and Anterior Cruciate Ligament Injury: Anatomy, Biomechanics and Management – State-of-the-art

Open AccessPublished:November 08, 2022DOI:https://doi.org/10.1016/j.jisako.2022.10.004

      Abstract

      Anterior cruciate ligament (ACL) rupture typically occurs because of sudden axial loading of the knee in conjunction with a coupled valgus and rotational moment about the tibia. However, the ACL is not the only structure damaged during this mechanism of injury, and studies have shown that the anterolateral complex (ALC) of the knee is also commonly involved. Biomechanical studies have established that the ALC plays an important role as a secondary stabilizer to control anterolateral rotational laxity (ALRL). Indeed, it has been suggested that failure to address injury to the ALC at the time of ACL reconstruction (ALCR)
      may increase the risk of graft failure owing to persistent ALRL. The concept of combining a lateral extra-articular procedure to augment ACLR for the treatment of ACL injury emerged with a view to decrease the failure rate of either procedure in isolation. This state-of-the-art review discusses the history of the anatomy of the ALC, the biomechanics of a variety of lateral extra-articular augmentation procedures, and provides clinical guidelines for their use in primary ACLR.

      Introduction

      Injury to the anterolateral complex (ALC) of the knee has been established as a significant
      contributing factor in the aetiology of anterolateral rotatory laxity (ALRL)[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ]. The ALC is comprised of superficial and deep aspects of the iliotibial band (ITB) with its Kaplan fiber (KF) attachments on the distal femur, along with the anterolateral ligament (ALL) which has been defined as a structure within the anterolateral capsule[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ]. Much of our understanding of the ALC and the contribution of each of the individual structures has emanated from anatomical dissection and biomechanical sectioning studies[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ,
      • Kaplan E.B.
      The iliotibial tract; clinical and morphological significance.
      ,
      • Terry G.C.
      • Hughston J.C.
      • Norwood L.A.
      The anatomy of the iliopatellar band and iliotibial tract.
      ,
      • Getgood A.
      The Anterolateral Complex: More than Just One Ligament.
      ,

      Segond, P., Recherches cliniques et expérimentales sur les épanchements sanguins du genou par entorse. 1879: Aux Bureaux du Progrès médical.

      ,

      Feagin, J.A., The crucial ligaments: diagnosis and treatment of ligamentous injuries about the knee. 1988: Churchill Livingstone.

      ]4-6. It has become increasingly evident with biomechanical and clinical studies that ACL reconstruction (ACLR) alone in the setting of ACL injury may not always eliminate residual ALRL and symptoms of instability[
      • Geeslin A.G.
      • et al.
      Anterolateral Knee Extra-articular Stabilizers: A Robotic Study Comparing Anterolateral Ligament Reconstruction and Modified Lemaire Lateral Extra-articular Tenodesis.
      ,
      • Inderhaug E.
      • et al.
      Biomechanical Comparison of Anterolateral Procedures Combined With Anterior Cruciate Ligament Reconstruction.
      ,
      • Neri T.
      • et al.
      Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction.
      ]. Moreover, the addition of a lateral extra-articular procedure to augment the ACLR has the potential to restore native knee kinematics in the setting of a combined ACL and ALC injury and decrease the rates of re-injury [
      • Devitt B.M.
      • et al.
      The role of lateral extra-articular tenodesis in primary anterior cruciate ligament reconstruction: a systematic review with meta-analysis and best-evidence synthesis.
      ,
      • Hewison C.E.
      • et al.
      Lateral extra-articular tenodesis reduces rotational laxity when combined with anterior cruciate ligament reconstruction: a systematic review of the literature.
      ,
      • Song E.K.
      • et al.
      Clinical outcome of avulsion fracture of the anterior cruciate ligament between children and adults.
      ,

      Getgood, A., et al., No Difference in Functional Outcomes When Lateral Extra-articular Tenodesis is Added to Anterior Cruciate Ligament Reconstruction in young active patients: The Stability Study. Arthroscopy, 2020.

      ,
      • Getgood A.M.
      • et al.
      Lateral extra-articular tenodesis reduces failure of hamstring tendon autograft anterior cruciate ligament reconstruction: 2-year outcomes from the STABILITY study randomized clinical trial.
      ,
      • Sonnery-Cottet B.
      • et al.
      Combined Anterior Cruciate Ligament and Anterolateral Ligament Reconstruction.
      ,

      Meier, B., Surgery Fixes a Ligament (if It Exists). Does It Fix the Knee?, in New York Times. 2016: on-line.

      ,
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Protects the Repaired Medial Meniscus: A Comparative Study of 383 Anterior Cruciate Ligament Reconstructions From the SANTI Study Group With a Minimum Follow-up of 2 Years.
      ,
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ]. A number of different lateral extra-articular procedures have been described to augment ACLR[
      • Slette E.L.
      • et al.
      Biomechanical Results of Lateral Extra-articular Tenodesis Procedures of the Knee: A Systematic Review.
      ]; for the purpose of this review the collective term for these procedures is hereinafter referred to as ‘lateral extra-articular augmentation procedure’ (LEAP). However, it is important to recognise that a LEAP is not always an innocuous procedure and carries the risk of certain complications[
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ]. Also, a LEAP should not be used ubiquitously in every primary ACLR. The aims of this state-of-the-art review are as follows:
      • To provide an overview of the evolution of our understanding of the anatomy of the anterolateral side of the knee
      • To analyse the biomechanics of a number of different LEAPs of the knee
      • To discuss the indications for a LEAP in the setting of primary ACL injury and suggest a guide for clinical decision-making

      Anatomy of the anterolateral side of the knee: An evolution in understanding

      Numerous historical studies have been published exploring the anatomy of the anterolateral side of the knee[
      • Kaplan E.B.
      The iliotibial tract; clinical and morphological significance.
      ,
      • Terry G.C.
      • Hughston J.C.
      • Norwood L.A.
      The anatomy of the iliopatellar band and iliotibial tract.
      ]. However, since 2013 and the publication of a seminal study by Claes et al entitled, ‘Anatomy of the anterolateral ligament of the knee’, this topic has gained renewed attention[
      • Claes S.
      • et al.
      Anatomy of the anterolateral ligament of the knee.
      ]. Notwithstanding the importance of the ALL, which itself has been the source of much controversy, what has emerged is that this structure is not a newly identified structure, but is part of the anterolateral complex (ALC) of the knee[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ,
      • Getgood A.
      The Anterolateral Complex: More than Just One Ligament.
      ].
      The original description was made by a French surgeon, Paul Segond in 1879, in his study entitled, ‘Les épanchements sanguins du genou par entorse,’ which was a treatise on the origin of a traumatic hemarthrosis of the knee following a so-called sprain[

      Segond, P., Recherches cliniques et expérimentales sur les épanchements sanguins du genou par entorse. 1879: Aux Bureaux du Progrès médical.

      ]. Segond’s treatise is based on an anatomical and biomechanical study of 90 cadaveric knees. Murgier et al, in their commentary of the translation of Segond’s original work, made some key comments which are highly relevant in the understanding of the role of the structures of the ALC of the knee:
      Segond recognised the importance of an anterolateral rotatory force as a pathomechanism of ACL and ALC injury: ‘Clinical observation and experimentation show that forced rotational movements of the leg on the thigh are responsible for most knee sprains. It is therefore the lesions caused by this type of movement that especially cause us to wonder about the reason for the blood.’ Indeed, the methodology employed to induce the knee injury confirms this understanding: ‘..we employed, as an immobilization method, 1 or 2 assistants who firmly grasped the thigh while, from our side, we applied forced movements to the knee using the only traumatic force that we were capable of producing ourselves.’ Segond is best known identifying the fracture, which bears his name (Segond Fracture), on the anterolateral aspect of the tibia, which occurred as a result of the forced anterolateral rotation and subluxation of the tibia which was required to induce an ACL rupture. It should be noted that Segond fractures represent only a small proportion of ALC injuries (between 3-10%) and soft tissue damage is often present in the absence of plain radiograph evidence of injury [
      • Cavaignac E.
      • et al.
      Is Treatment of Segond Fracture Necessary With Combined Anterior Cruciate Ligament Reconstruction? Letter to the Editor.
      ,
      • Pan Z.
      • et al.
      Is Treatment of Segond Fracture Necessary With Combined Anterior Cruciate Ligament Reconstruction? Letter to the Editor.
      ].
      The next point is very simple, often overlooked, but perhaps the most crucial of all. It relates to the method of dissection. The quotation from Segond’s treatise that has been ubiquitously used to draw parallels with the findings of Claes et al, describes, ‘a pearly, resistant, fibrous band that is placed under extreme tension when the knee is forcefully rotated internally.’ What has failed to have been disclosed in manuscripts that use this phrase is the preceding sentence which provides the context and states: ‘This can easily be seen when we examine a knee without its skin envelope.’ It doesn’t describe removing the iliotibial band (ITB) entirely as is the case in the study by Claes et al and many others[
      • Claes S.
      • et al.
      Anatomy of the anterolateral ligament of the knee.
      ,
      • Daggett M.
      • et al.
      The Anterolateral Ligament: An Anatomic Study on Sex-Based Differences.
      ,
      • Vincent J.P.
      • et al.
      The anterolateral ligament of the human knee: an anatomic and histologic study.
      ,
      • Daggett M.
      • et al.
      Femoral Origin of the Anterolateral Ligament: An Anatomic Analysis.
      ]. What it is actually describing is the ITB itself and not the ALL in isolation. It is very obvious that Segond recognised the importance of the ITB, a fact that is supported by Kaplan and others that followed[
      • Kaplan E.B.
      The iliotibial tract; clinical and morphological significance.
      ].
      Kaplan, an anatomist and hand surgeon, made a significant contribution to understanding the anatomy of this region by describing the layers of the ITB attachment to the distal femur in his publication in 1958[
      • Kaplan E.B.
      The iliotibial tract; clinical and morphological significance.
      ,
      • Spinner R.J.
      • Dellon A.L.
      Emanuel B. Kaplan, M.D. (1894-1980): A Legendary Anatomist and Hand Surgeon.
      ]. Following this, the lateral side of the knee was largely ignored in the literature for an extended period of time. It was considered by many a region akin to the ‘dark side of the moon’, as described in John Feagin’s seminal book ‘Crucial Ligaments’, such was its mystery, obscurity and complexity[

      Feagin, J.A., The crucial ligaments: diagnosis and treatment of ligamentous injuries about the knee. 1988: Churchill Livingstone.

      ]. Terry et al finally shone some light on the area in their study published in 1986, which meticulously detailed the two main component parts of the lateral fascia lata; the iliopatellar band and the iliotibial tract (ITT)[
      • Terry G.C.
      • Hughston J.C.
      • Norwood L.A.
      The anatomy of the iliopatellar band and iliotibial tract.
      ]. The authors used the term ‘anterolateral ligament’ in this manuscript to refer to the deep, capsulo-osseous, and superficial layers of the ITT[
      • Terry G.C.
      • Hughston J.C.
      • Norwood L.A.
      The anatomy of the iliopatellar band and iliotibial tract.
      ]. Around the same period, Lobenhoffer et al further defined the contribution of the ITT by documenting the existence of ‘the retrograde tract’ which provides a connection from the posterolateral aspect of the femur to Gerdy’s tubercle on the anterolateral aspect of the tibia[
      • Lobenhoffer P.
      • et al.
      Distal femoral fixation of the iliotibial tract.
      ]; the authors describe this connection as “an arc bridging the knee joint” and make reference to a similar finding by Müller et al called the “lig. femoro-tibiale laterale anterius.”[
      • Muller W.
      [Functional anatomy and clinical findings of the knee joint].
      ]
      Chinese whispers’ refers to a children’s game in which a sequence of repetitions of a story are told, each one differing slightly from the previous, so that the final telling bears only a scant resemblance to the original. This is a particularly apt description of how the confusion surrounding the nomenclature used to describe the complex anatomy of the anterolateral side of the knee was created[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ]. Vieira et al. are often credited with coining the phrase ‘Anterolateral ligament’, although they clearly make reference to the term originating from the study by Terry et al[
      • Vieira E.L.
      • et al.
      An anatomic study of the iliotibial tract.
      ]. But, the term actually goes back further and was indeed mentioned by Kaplan in his original work on the surgical approach to the lateral side of the knee which even preceded his anatomical treatise on the iliotibial tract[
      • Kaplan E.B.
      Surgical approach to the lateral (peroneal) side of the knee joint.
      ]; he makes the following statement: “In extensive lateral approaches to the knee joint, it was noted that the iliotibial tract acted as an accessory anterolateral ligament of the knee preserving stability in which the lateral collateral ligament was lost.” The structure which Vieira et al later described is a capsulo-osseous extension of the ITT which “starts from the lateral supraepicondylar region, bordering the lateral edge of the lateral epicondyle and inserting laterally to the Gerdy’s tubercle”[
      • Vieira E.L.
      • et al.
      An anatomic study of the iliotibial tract.
      ].
      There have been a myriad of anatomical studies focusing on the ALL, including dissection at the time of total knee replacement in live patients as well as a number of cadaveric dissections[
      • Terry G.C.
      • Hughston J.C.
      • Norwood L.A.
      The anatomy of the iliopatellar band and iliotibial tract.
      ,
      • Vincent J.P.
      • et al.
      The anterolateral ligament of the human knee: an anatomic and histologic study.
      ,
      • Vieira E.L.
      • et al.
      An anatomic study of the iliotibial tract.
      ]; each report slight variations in attachment sites and relationship to adjacent structures. The theory also emerged that the ALL and the mid-third lateral capsular ligament were one and the same thing[
      • Caterine S.
      • et al.
      A cadaveric study of the anterolateral ligament: re-introducing the lateral capsular ligament.
      ]. Caterine et al, in addition to others, performed histological analysis of the ALL structure and further substantiated the belief that it has ligamentous properties as a result of its well-organised collagen bundles[
      • Vincent J.P.
      • et al.
      The anterolateral ligament of the human knee: an anatomic and histologic study.
      ,
      • Caterine S.
      • et al.
      A cadaveric study of the anterolateral ligament: re-introducing the lateral capsular ligament.
      ,
      • Helito C.P.
      • et al.
      Anatomy and Histology of the Knee Anterolateral Ligament.
      ]. Indeed, it has been demonstrated that the ALL has significantly different biomechanical properties to the adjacent capsule; this is analogous the shoulder and the inferior glenohumeral ligament[
      • Smeets K.
      • et al.
      The Anterolateral Ligament Has Similar Biomechanical and Histologic Properties to the Inferior Glenohumeral Ligament.
      ].
      An attempt to develop consensus on the relative importance of the ALL and the other anterolateral structures of the knee was made with the formation of the Anterolateral Complex Consensus Group which consisted of 36 international researchers and clinicians in the field[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ]. The group met in London, United Kingdom, in October 2017. The aims of the group were three:
      • 1.
        Develop a consensus in terms of the anatomical terminology utilised for structures within the anterolateral capsule.
      • 2.
        Produce position statements as to the kinematic role of key structures in the knee, pertaining specifically to ALRL and ACL deficiency.
      • 3.
        Provide clinical guidance on when to utilise an anterolateral procedure in the ACL-deficient knee.
      The group made specific reference to the layers of the lateral side of the knee and anterolateral complex. In particular, the anatomical work of Seebacher et al was heavily referenced, in which the lateral structure of the knee can be divided into three distinct layers[
      • Seebacher J.R.
      • et al.
      The structure of the posterolateral aspect of the knee.
      ] (Figure 1). The authors described Layer 3 of the anterolateral capsule as splitting into a superficial and deep lamina anterior to the LCL, and enveloping it posterolaterally. Accordingly, the consensus group concluded that the ALL is a structure within Layer 3 of the anterolateral capsule, and that the superficial lamina is the ALL with the deep lamina being the true capsule of the knee at this level.
      Figure 1
      Figure 1Seebacher et al[
      • Seebacher J.R.
      • et al.
      The structure of the posterolateral aspect of the knee.
      ] - A view of the right knee joint from above after removal of the right femur. Note the three layers of the lateral side and the division of the posterolateral part of the capsule (Layer III) into deep and superficial laminae which are separated by the lateral inferior genicular vessels.
      The group made the following statement regarding the anatomy of the anterolateral complex of the knee:
      • 1.
        The ALL is a structure within the anterolateral complex
      • 2.
        The structures of the anterolateral complex, from superficial to deep, are:
        • a.
          Superficial IT band and iliopatellar band
        • b.
          Deep IT band incorporating
          • i.
            Kaplan fibre system
            • 1.
              Supracondylar attachments
              • a.
                Proximal
              • b.
                Distal
            • ii.
              Retrograde (Condylar) attachment continuous with capsule-osseous layer of the IT band
        • c.
          ALL and capsule
      • 3.
        The ALL is a capsular structure within Seebacher Layer 3 of the anterolateral capsule of the knee[
        • Seebacher J.R.
        • et al.
        The structure of the posterolateral aspect of the knee.
        ].
      • 4.
        The ALL has variable gross morphology between individuals in terms of size and thickness.
      • 5.
        The ALL predominantly attaches posterior and proximal to the lateral femoral epicondyle and the origin of the LCL, runs superficial to the LCL and attaches on the tibia midway between the anterior border of the fibular head and the posterior border of Gerdy’s Tubercle (GT).
      • 6.
        There is an attachment of the ALL to the lateral meniscus.
      Based on this consensus, it is reasonable to conclude that the anterolateral complex of the knee is complex by name and complex by nature.
      The concept of ‘anterolateral rotatory instability’ of the knee was introduced by Hughston et al in 1976[
      • Hughston J.C.
      • et al.
      Classification of knee ligament instabilities. Part II. The lateral compartment.
      ]. In their study, the authors described an injury pattern ‘caused by a tear of the middle one-third of the lateral capsular ligament but it may be accentuated by other tears, principally a tear of the anterior cruciate.’ As this theory began to evolve, the pedants pointed out that ‘instability’ is a subjective feeling experienced by the patient and what we, as physicians, can assess clinically is actually joint laxity. Therefore, the terminology has changed to reflect the correct scientific jargon: Anterolateral rotatory laxity (ALRL).

      Biomechanics of lateral extra-articular augmentation procedures

      The ALC of the knee also plays a critical role in normal knee kinematics. Assessment of knee kinematics is typically performed in the clinic by clinical examination; this involves examination of all six-degrees of freedom of the knee, through assessment of range of motion and a variety of specialty tests designed to measure sagittal, coronal and rotatory laxity. With respect to ACL injury and assessment, the examination of the knee involves assessment of both anterior tibial translation with the Lachman or anterior drawer tests, and also anterolateral tibial translation with tests such as the pivot shift test.
      In order to simplify the understanding of the biomechanics of LEAPs, they have been broadly classified in two groups: (Figure 2)
      • Anatomical reconstructions: Anterolateral ligament reconstruction
      • Non-anatomical reconstructions: LEAPs using the ITB
      Figure 2
      Figure 2A-E: A variety of lateral augmentation procedures divided into 2 groups[
      • Neri T.
      • et al.
      Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction.
      ]: Anatomic and Non-Anatomic. A. Anatomic: Anterolateral ligament Reconstruction. B-E Non-anatomic: B. Modified Ellison; C. Modified Deep Lemaire; D. Modified Superficial Lemaire; and, E. MacIntosh technique.
      The majority of LEAPs are based on a proximally fixed construct, typically with a strip of ITB, which remains attached to its insertion at or near to the GT[
      • Slette E.L.
      • et al.
      Biomechanical Results of Lateral Extra-articular Tenodesis Procedures of the Knee: A Systematic Review.
      ]. The free proximal end passes either deep or superficial to the lateral collateral ligament (LCL) and is typically fixed
      to the femur posterior and proximal to the lateral epicondyle; the main varieties of this technique discussed in this review are the MacIntosh and the modified Lemaire procedures[
      • Galway H.R.
      • MacIntosh D.L.
      The lateral pivot shift: a symptom and sign of anterior cruciate ligament insufficiency.
      ,
      • Lemaire M.
      [Chronic knee instability. Technics and results of ligament plasty in sports injuries].
      ]. A distally fixed ITB transfer, originally described by Ellison, has also been used[
      • Ellison A.E.
      Distal iliotibial-band transfer for anterolateral rotatory instability of the knee.
      ]. This technique uses a strip of ITB, which is elevated from the GT with or without a sliver of bone and reflected proximally and then passed deep to the LCL and reattached to the region of the GT. Finally, the ALLR typically involves using a free graft of gracilis tendon, which is fixed to a point posterior and proximal to the origin of the LCL on the lateral femoral epicondyle and passed to a point of the tibia mid-way between the fibular heard and GT[
      • Neri T.
      • et al.
      The anterolateral ligament: Anatomic implications for its reconstruction.
      ,
      • Sonnery-Cottet B.
      • Vieira T.D.
      • Ouanezar H.
      Anterolateral Ligament of the Knee: Diagnosis, Indications, Technique, Outcomes.
      ]. The graft is passed deep to the ITB.
      In terms of comparison, the three main biomechanical functions of these procedures have been considered: Control of anterior tibial translation; control of internal rotation (IR) of the tibia; and ALRL during a simulated PS test.

      Anterior tibial translation

      The majority of available studies show that the ALLR has little or no influence on the control of anterior tibial translation[
      • Sonnery-Cottet B.
      • et al.
      The Involvement of the Anterolateral Ligament in Rotational Control of the Knee.
      ,
      • Drews B.H.
      • et al.
      Function and strain of the anterolateral ligament part I: biomechanical analysis.
      ]. In contrast, because of the more horizontal course of the graft, the lateral extra-articular tenodesis (LET) using ITB seems to have a greater effect on this translation parameter[
      • Aguilera-Tejero E.
      • et al.
      Measurement of pulmonary diffusing capacity for carbon monoxide and functional residual capacity during rebreathing in conscious thoroughbreds.
      ,
      • Amis A.A.
      Anterolateral knee biomechanics.
      ]. This can be explained by a difference in geometry between the anatomical fixation points of the grafts. While there is no difference in the femoral insertion location between the two techniques (they both use a tunnel positioned posterior and proximal to the femoral epicondyle), there is a difference in their tibial fixation locations. The ALL tibial insertion is at a point midway between a line connecting GT and the fibular head [
      • Claes S.
      • et al.
      Anatomy of the anterolateral ligament of the knee.
      ,
      • Neri T.
      • et al.
      The anterolateral ligament: Anatomic implications for its reconstruction.
      ]. The tibial positioning of the LET is located at the GT, which is more anterior (approximately 18-20 mm) to that of the ALLR[
      • Neri T.
      • et al.
      The anterolateral ligament: Anatomic implications for its reconstruction.
      ]. Thus, the force resisting antero-posterior translation and internal rotation of the tibia (particularly its horizontal anteroposterior component), will be greater for the LET than for the ALLR [
      • Neri T.
      • et al.
      The anterolateral ligament: Anatomic implications for its reconstruction.
      ,
      • Neri T.
      • et al.
      Anterolateral Ligament of the Knee: What we Know About its Anatomy, Histology, Biomechanical Properties and Function.
      ] (Figure 2).

      Internal Rotation

      The role of the ALLR and LET in controlling tibial IR is widely supported in the literature [
      • Sonnery-Cottet B.
      • et al.
      The Involvement of the Anterolateral Ligament in Rotational Control of the Knee.
      ,
      • Musahl V.
      • et al.
      Contributions of the anterolateral complex and the anterolateral ligament to rotatory knee stability in the setting of ACL Injury: a roundtable discussion.
      ]. Injury or sectioning of the ALC structures, including the ALL, KF and ITB , in ACL-deficient knees has been shown to significantly increase IR of the tibia[
      • Sonnery-Cottet B.
      • et al.
      The Involvement of the Anterolateral Ligament in Rotational Control of the Knee.
      ,
      • Monaco E.
      • et al.
      The Effect of Sequential Tearing of the Anterior Cruciate and Anterolateral Ligament on Anterior Translation and the Pivot-Shift Phenomenon: A Cadaveric Study Using Navigation.
      ,
      • Kittl C.
      • et al.
      The Role of the Anterolateral Structures and the ACL in Controlling Laxity of the Intact and ACL-Deficient Knee: Response.
      ]. With an increased lever arm, structures on the anterolateral aspect of the knee will have more influence on controlling rotation than an intra-articular structure (Figure 3)[
      • Amis A.A.
      Anterolateral knee biomechanics.
      ]. Its torque will be greater than that of the ACL. These structures have a synergistic function with the ACL in controlling the rotational laxity of the knee [
      • Neri T.
      • et al.
      Determining the change in length of the anterolateral ligament during knee motion: A three-dimensional optoelectronic analysis.
      ]. The ALL controls IR of the tibia at the start of knee flexion, between 0-30° of flexion [
      • Sonnery-Cottet B.
      • et al.
      The Involvement of the Anterolateral Ligament in Rotational Control of the Knee.
      ,
      • Neri T.
      • et al.
      Determining the change in length of the anterolateral ligament during knee motion: A three-dimensional optoelectronic analysis.
      ,
      • Rasmussen M.T.
      • et al.
      An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 1: Secondary Role of the Anterolateral Ligament in the Setting of an Anterior Cruciate Ligament Injury.
      ]. However, in contrast, the ITB and KFsmaintain their control of IR through the whole cycle of knee flexion, with a maximal control around at 90° of knee flexion [
      • Sayac G.
      • et al.
      The anatomy of Kaplan fibers.
      ,
      • Geeslin A.G.
      • et al.
      Anterolateral Knee Extra-articular Stabilizers: A Robotic Sectioning Study of the Anterolateral Ligament and Distal Iliotibial Band Kaplan Fibers.
      ]. When comparing different LEAP, Neri et al demonstrated that only the ALLR and modified Ellison procedure restored overall IR kinematics, through the full range of flexion, compared to the normal intact knee[
      • Neri T.
      • et al.
      Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction.
      ]. From 0° to 90° of flexion, the addition of ALLR produced a significant additional control compared with isolated ACLR, which resulted in a near normal overall kinematics pattern. The addition of a modified Ellison procedure caused a significant decrease in IR between 0° and 45° of knee flexion with a lack of rotational control beyond this range. The authors also found that, regardless of the degree of knee flexion, the superficial and deep Lemaire and modified MacIntosh tenodeses tended to overconstrain the knee during IR (see Fig. 4).
      Figure 3
      Figure 3A and B: Biomechanical considerations for graft location explaining the biomechanical differences between the ALLR and LET procedures, such as the deep modified Lemaire[
      • Neri T.
      • et al.
      Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction.
      ](FALLR: overall action of ALLR, with horizontal (FxALLR) and vertical (FYALLR) components; FLET: overall action of LET, with horizontal (FxLET) and vertical (FYLET) components) – ALLR – Anterolateral ligament reconstruction, LET – Lateral extra-articular tenodesis.
      Figure 4
      Figure 4A and B: Biomechanical function of the anterolateral structures [
      • Neri T.
      • et al.
      Anterolateral Ligament of the Knee: What we Know About its Anatomy, Histology, Biomechanical Properties and Function.
      ].
      A torque is an applied force multiplied by the distance (red dotted lines) from the center of rotation (lever arm).
      A: An intra-articular structure (ACL) is closer to the rotation center. Therefore, a greater force is required to control rotation (internal rotation)
      B: An extra-articular structure is located at a greater distance from the center of rotation. Therefore, less force is needed to control the same rotation

      Simulated pivot shift

      A number of studies have examined the involvement of anterolateral structures in the ALRL found during the PS test[
      • Song E.K.
      • et al.
      Clinical outcome of avulsion fracture of the anterior cruciate ligament between children and adults.
      ,

      Getgood, A., et al., No Difference in Functional Outcomes When Lateral Extra-articular Tenodesis is Added to Anterior Cruciate Ligament Reconstruction in young active patients: The Stability Study. Arthroscopy, 2020.

      ,
      • Getgood A.M.
      • et al.
      Lateral extra-articular tenodesis reduces failure of hamstring tendon autograft anterior cruciate ligament reconstruction: 2-year outcomes from the STABILITY study randomized clinical trial.
      ,
      • Sonnery-Cottet B.
      • et al.
      Combined Anterior Cruciate Ligament and Anterolateral Ligament Reconstruction.
      ]. Like many aspects of the ALC, controversy also exists as to which components of the ALC have the biggest impact in controlling the PS. Some studies suggested that a lesion of these structures is responsible for a higher grade on the PS test than an isolated ACL lesion while others have not [
      • Monaco E.
      • et al.
      The Effect of Sequential Tearing of the Anterior Cruciate and Anterolateral Ligament on Anterior Translation and the Pivot-Shift Phenomenon: A Cadaveric Study Using Navigation.
      ,
      • Ferretti A.
      • et al.
      Risk Factors for Grade 3 Pivot Shift in Knees With Acute Anterior Cruciate Ligament Injuries: A Comprehensive Evaluation of the Importance of Osseous and Soft Tissue Parameters From the SANTI Study Group.
      ,
      • Cavaignac E.
      • et al.
      Ultrasonographic Evaluation of Anterolateral Ligament Injuries: Correlation With Magnetic Resonance Imaging and Pivot-Shift Testing.
      ,
      • Devitt B.M.
      • et al.
      Association Between Radiological Evidence of Kaplan Fiber Injury, Intraoperative Findings, and Pivot-Shift Grade in the Setting of Acute Anterior Cruciate Ligament Injury.
      ]. Bonanzinga et al. found only significant results for the acceleration component of the lateral proximal tibia but not for the IR component during the PS test with combined ALL injury and ACL deficiency [
      • Bonanzinga T.
      • et al.
      Kinematics of ACL and anterolateral ligament. Part I: Combined lesion.
      ]. Noyes et al, in a biomechanical sectioning study revealed that sectioning of the ALL and the ITB in ACL-deficient knees converted 71% of the specimens to a grade 3 pivot shift as measured by composite tibiofemoral translations and rotations[
      • Noyes F.R.
      • Huser L.E.
      • Levy M.S.
      Rotational Knee Instability in ACL-Deficient Knees: Role of the Anterolateral Ligament and Iliotibial Band as Defined by Tibiofemoral Compartment Translations and Rotations.
      ]. Therefore, it would appear that the greater the extent of injury to the ALC the greater the grade of ALRL.
      Notwithstanding the impact of ALC injury on ALRL, LEAP have been shown to have a beneficial effect on reducing simulated PS in the biomechanical setting. There a myriad of biomechanical studies, which have focused on a simulated PS when comparing different LEAP; a comparison of these is made in the next section[
      • Geeslin A.G.
      • et al.
      Anterolateral Knee Extra-articular Stabilizers: A Robotic Study Comparing Anterolateral Ligament Reconstruction and Modified Lemaire Lateral Extra-articular Tenodesis.
      ,
      • Inderhaug E.
      • et al.
      Biomechanical Comparison of Anterolateral Procedures Combined With Anterior Cruciate Ligament Reconstruction.
      ,
      • Inderhaug E.
      • et al.
      Anterolateral Tenodesis or Anterolateral Ligament Complex Reconstruction: Effect of Flexion Angle at Graft Fixation When Combined With ACL Reconstruction.
      ,
      • Devitt B.M.
      • et al.
      Biomechanical Assessment of a Distally Fixed Lateral Extra-articular Augmentation Procedure in the Treatment of Anterolateral Rotational Laxity of the Knee.
      ]. However, It is very important to remember that biomechanical studies, due to the limitations in the loads that can be subjected to the knee and the speeds at which the tests can be performed, are more likely to simulate knee examination in the clinic through manual tests rather that the on-field loads that the knee withstands during sporting activity[
      • Lord B.R.
      • et al.
      Biomechanical comparison of graft structures in anterior cruciate ligament reconstruction.
      ]. In addition, the results of biomechanical tested are representative of only a ‘time zero’ state and do not take into account subsequent healing, cyclic loading, and rehabilitation. The clinical PS is a dynamic examination through a range of motion. It must be considered that biomechanical studies have not replicated in vivo kinematics but only the coupled laxities[
      • Lord B.R.
      • et al.
      Biomechanical comparison of graft structures in anterior cruciate ligament reconstruction.
      ,
      • Goldsmith M.T.
      • et al.
      Biomechanical comparison of anatomic single- and double-bundle anterior cruciate ligament reconstructions: an in vitro study.
      ,
      • Kittl C.
      • et al.
      The Role of the Anterolateral Structures and the ACL in Controlling Laxity of the Intact and ACL-Deficient Knee.
      ].

      Biomechanical comparison of different techniques

      Inderhaug et al, in their seminal paper, demonstrated that there are significant kinematic differences between different LEAP techniques[
      • Inderhaug E.
      • et al.
      Biomechanical Comparison of Anterolateral Procedures Combined With Anterior Cruciate Ligament Reconstruction.
      ]. They reported that only the modified MacIntosh and deep Lemaire procedures restored native knee kinematics, while the ALLR did not [
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ]. The method of fixation of the ALLR has been questioned in this study, as this was fixed with suture anchors and not interference screws, which were employed for the other techniques. Geesling et al. in a robotic study, reported that both the ALLR and LET procedures resulted in significant reductions in tibial IR compared to the intact state, regardless of graft tension or fixation angle[
      • Claes S.
      • et al.
      Anatomy of the anterolateral ligament of the knee.
      ]. However, this study only analyzed the deep Lemaire and ALLR on isolated knees. It should be noted that the ITB was not loaded in either of these studies, a point which is perhaps highly relevant considering the reported importance of this structure[
      • Noyes F.R.
      • et al.
      Anterior Cruciate Ligament Graft Conditioning Required to Prevent an Abnormal Lachman and Pivot Shift After ACL Reconstruction: A Robotic Study of 3 ACL Graft Constructs.
      ]. The vast majority of cadaveric studies performed used knees that were transected at the level of the mid-femur and mid-tibia – as such, the ITB band had no proximal attachment and its only distal attachment to the femur was through the KF, which were sectioned along with the anterolateral capsule and the ALL to create a ‘worst-case scenario injury’. This effectively removed any load through the ITB and effectively rendered it defunct as a secondary stabiliser to the knee[
      • Losee R.E.
      Concepts of the pivot shift.
      ].
      ITB – Iliotibial band, KF – Kaplan Fiber, ALL – Anterolateral Ligament
      Devitt et al, in a novel robotic testing model, loaded the ITB to test a distally-based LET, the modified Ellison procedure, and demonstrated that it closely restored native knee kinematics and only resulted in slight over-constraint with isolated IR at 30° of knee flexion [
      • Cavaignac E.
      • et al.
      Is Treatment of Segond Fracture Necessary With Combined Anterior Cruciate Ligament Reconstruction? Letter to the Editor.
      ]. Neri et al subsequently caried out an in vitro biomechanical study, maintaining the entire lower limb intact thereby preserving the effect of the ITB and biceps femoris, and demonstrated that the addition of ALLR or the modified Ellison procedure to an ACLR in an ACL and ALC deficient knee closely restored native knee kinematics [
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ]. The superficial and deep Lemaire LET, as well as modified MacIntosh procedure, achieved excellent rotational control but tended to over-constrained IR, resulting in a change in intact knee kinematics. So, what is the reason for these differences?
      It has been proposed that the mechanical properties of the graft might be a factor. The ALLR reconstruction is typically performed with a free strip of gracilis tendon while the LET procedure uses the ITB. Wytrykowski et al. analysed the mechanical characteristics of the different grafts and found that the gracilis had a maximum load to failure of 200 N, a stiffness of 131.7 N mm-1, and an elongation at failure of 19 mm, whereas the ITB had a maximum load to failure of 160 N, a stiffness of 39.9 N mm-1 and an elongation at failure of 20.8 mm[
      • Muller W.
      [Functional anatomy and clinical findings of the knee joint].
      ]. However, it unlikely these small differences are not enough to explain the change in kinematics.
      A more likely explanation stems from the difference in the geometry of the fixation points of the two grafts[
      • Terry G.C.
      • Hughston J.C.
      • Norwood L.A.
      The anatomy of the iliopatellar band and iliotibial tract.
      ]. The tibial positioning of the LET is uniform with most techniques as the distal attachment of the ITB is left intact at GT; this is the same for the modified Ellison technique[
      • Feller J.A.
      • et al.
      Augmentation of Primary ACL Reconstruction With a Modified Ellison Lateral Extra-articular Tenodesis in High-Risk Patients: A Pilot Study.
      ]. The distal ALL insertion on the tibia is more posteriorly located, thereby potentially explaining why the forces resisting IR and anteroposterior translation of the tibia are different. (Figure 2). It has also been suggested that the force applied to tension the graft may also play a factor in possibly over-constraining the lateral compartment. Indeed, Inderhaug et al, in their biomechanical study exploring a variety of LEAP techniques, reported a tendency toward overconstraint of anterior translation in deep flexion occurred only with 40 N of tension[
      • Inderhaug E.
      • et al.
      Biomechanical Comparison of Anterolateral Procedures Combined With Anterior Cruciate Ligament Reconstruction.
      ]. They stated that “during pilot testing before the study, 80 N was found to approximate a clinical maximum manual pull, but because of unfavorable kinematic responses to the lesser 60 N, these tensions were not included in the study.” The authors advised that, “surgeons performing combined procedures should be aware of the risk of overconstraining the knee when tensioning and fixing the graft.
      Another important consideration is the effect of passing the graft beneath the lateral collateral ligament (LCL). Neri et al showed that passing the ITB above the LCL (superficial Lemaire) resulted in greater constraint in full flexion compared to when the graft was passed beneath the LCL (deep Lemaire or modified MacIntosh) [
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ]. Biomechanically, there is no clear explanation. One hypothesis could be that in flexion the superficial graft must pass over the epicondyle, which represents a longer distance in flexion than the path beneath the LCL, which closer to the bone. An alternate explanation is that passage of the graft beneath the LCL may create a pulley effect, mainly in extension. Thus, it can be expected that the deep graft is likely to be tighter in extension and the superficial graft tighter in flexion. With the modified Ellison technique, the lack of a femoral attachment increases the range of variation in graft length, potential making this procedure less rigid.

      Lateral augmentation procedures in primary ACLR: A guide for clinical decision-making

      The goal of surgical management of an ACL rupture is to achieve a knee that feels as normal as possible, functions as normal as possible, and that has the lowest possibility of being reinjured.
      Isolated ACLR does not achieve these objectives in all patients. In high risk populations, re-rupture rates range from 10-28%[
      • Wiggins A.J.
      • et al.
      Risk of Secondary Injury in Younger Athletes After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis.
      ,
      • Webster K.E.
      • Feller J.A.
      Exploring the High Reinjury Rate in Younger Patients Undergoing Anterior Cruciate Ligament Reconstruction.
      ]. Reoperation rates for reasons other than graft rupture are as high as 26-30%[
      • Hettrich C.M.
      • et al.
      The rate of subsequent surgery and predictors after anterior cruciate ligament reconstruction: two- and 6-year follow-up results from a multicenter cohort.
      ]. Residual rotatory laxity, as defined by pivot shift can be as high as 51.7% in some cohorts[

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in patients with anterior cruciate ligament injury and ligamentous hyperlaxity leads to better clinical stability and a lower failure rate than isolated anterior cruciate ligament reconstruction. 2019. 35(9): p. 2648-2654.

      ], and return to the same level sport can be less than 50%, even in expert centres[
      • McCullough K.A.
      • et al.
      Return to high school- and college-level football after anterior cruciate ligament reconstruction: a Multicenter Orthopaedic Outcomes Network (MOON) cohort study.
      ]. It is clear there is room for improvement and the addition of a lateral augmentation procedure may provide some benefit in achieving this. However, a number of lingering questions remain:
      • 1.
        Should we use a lateral augmentation procedure in primary ACLR?
      • 2.
        What are the indications for its use?
      • 3.
        And, which one should we use?

      Should we use a lateral augmentation procedure in primary ACLR?

      Multiple studies have demonstrated the effectiveness of different LEAPs in reducing graft re-rupture risk in primary ACLR. Getgood et al observed almost a 3-fold reduction in re-rupture rate for ACLR and LET compared to ACLR alone (4% versus 11% respectively)[
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ]. Sonnery-Cottet et al reported that ACLR with hamstring tendon (HT) autograft and ALLR had a 3.1 times lower re-rupture rate than 4-strand HT alone, and 2.5 times lower than bone patellar tendon bone (BPTB) autograft (4.13% versus 16.77% versus 10.77%, respectively)[
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ]. More recently, the SANTI study group reported 100-month follow-up data comparing isolated ACLR to ACLR and ALLR and showed that patients undergoing isolated ACLR were at >5-fold greater risk of graft rupture and had double the re-operation rate (30% versus 15%)[

      Sonnery-Cottet, B., et al., Graft Rupture Rates After Combined ACL and Anterolateral Ligament Reconstruction Versus Isolated ACL Reconstruction: A Matched-Pair Analysis From the SANTI Study Group. 2021: p. 3635465211028990-3635465211028990.

      ]. In another long-term study with mean follow-up of 15.7 years, Viglietta et al demonstrated a significant difference in ACL graft rupture rates between ACLR and LET (1.3%) and ACLR (10.5%) alone[
      • Viglietta E.
      • et al.
      ACL Reconstruction Combined With the Arnold-Coker Modification of the MacIntosh Lateral Extra-articular Tenodesis: Long-term Clinical and Radiological Outcomes.
      ].
      The benefit of combined procedures seems to be even more pronounced in patients diagnosed with joint hyperlaxity as reported by Helito et al in 2019, where the ACLR group alone had a 21.7% re-rupture rate versus 3.3% for those with combined ACLR and ALLR using gracilis tendon[

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in patients with anterior cruciate ligament injury and ligamentous hyperlaxity leads to better clinical stability and a lower failure rate than isolated anterior cruciate ligament reconstruction. 2019. 35(9): p. 2648-2654.

      ]. A systematic review and meta-analysis in 2021 by Beckers et al supports this weight of evidence for combining a lateral augmentation procedure with ACLR to reduce the risk of graft rupture[
      • Beckers L.
      • et al.
      Clinical outcomes of contemporary lateral augmentation techniques in primary ACL reconstruction: a systematic review and meta-analysis.
      ]. It should be acknowledged that the most of the aforementioned studies used hamstring autograft as the ACLR graft. As such, further studies are required to be able to extrapolate the benefits of combing a LEAP with other graft types, such as patellar tendon and quadriceps tendon autografts, in reducing the risk of graft rupture.
      The effect of LEAPs on functional outcomes with the exclusion of re-rupture risk are a little more mixed [
      • Beckers L.
      • et al.
      Clinical outcomes of contemporary lateral augmentation techniques in primary ACL reconstruction: a systematic review and meta-analysis.
      ]. Importantly, there are few studies demonstrating that isolated ACLR patients have improved outcomes in comparison to combined ACLR and LEAPs. Beckers et al, in a systematic review of 11 studies that reported on a combined total of 1892 patients, showed a strong trend towards improved IKDC, Lyshom, and Tegner scores with combined procedures, with the pooled data for Lysholm reaching statistical significance compared to isolated ACLR[
      • Beckers L.
      • et al.
      Clinical outcomes of contemporary lateral augmentation techniques in primary ACL reconstruction: a systematic review and meta-analysis.
      ].
      Getgood et al demonstrated no significant differences in return to sport (RTS) between isolated ACLR and combined ACLR and LET (85% versus 82% respectively) [
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ]. Sonnery-Cottet et al reported that ACLR and ALLR had higher RTS than ACLR alone with HT (odds ratio of 1.94) but no difference when compared to isolated BPTB ACLR [
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ]. Rosential et al reported a high RTS for professional athletes for combined ACLR and ALLR (85.7% return to play at same level at 8 months), but there was no control group [
      • Rosenstiel N.
      • et al.
      Combined Anterior Cruciate and Anterolateral Ligament Reconstruction in the Professional Athlete: Clinical Outcomes From the Scientific Anterior Cruciate Ligament Network International Study Group in a Series of 70 Patients With a Minimum Follow-Up of 2 Years.
      ]. While Feller et al, in a pilot study of the modified Ellison in a high-risk population showed RTS of 74% at the pre-injury level or higher [
      • Feller J.A.
      • et al.
      Augmentation of Primary ACL Reconstruction With a Modified Ellison Lateral Extra-articular Tenodesis in High-Risk Patients: A Pilot Study.
      ].
      Assessment of the grade of PS is important as it has been shown to correlate with patient outcomes following ACLR, unlike measurements of anterior knee laxity, which do not [
      • Lane C.G.
      • Warren R.
      • Pearle A.D.
      The pivot shift.
      ]. Objective assessment of laxity also favours the combined procedure, particularly for ALRL (pivot shift). Kuntz et al., in a recent systematic review and meta-analysis, concluded that ALLR decreases the grade of PS post ACLR [
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Protects the Repaired Medial Meniscus: A Comparative Study of 383 Anterior Cruciate Ligament Reconstructions From the SANTI Study Group With a Minimum Follow-up of 2 Years.
      ]. In addition, in the setting of primary ACLR, Devitt et al, in another systematic review, found that the addition of a LET to ACLR reduced the grade of PS; however, this occurred more commonly in the chronic setting (ACLR more than 12-months post injury) rather than in acute ACLR[
      • Devitt B.M.
      • et al.
      The Role of Lateral Extra-articular Tenodesis in Primary Anterior Cruciate Ligament Reconstruction: A Systematic Review With Meta-analysis and Best-Evidence Synthesis.
      ]. These same findings have been found in two other systematic reviews [
      • Beckers L.
      • et al.
      Clinical outcomes of contemporary lateral augmentation techniques in primary ACL reconstruction: a systematic review and meta-analysis.
      ,

      Hewison, C.E., et al., Lateral extra-articular tenodesis reduces rotational laxity when combined with anterior cruciate ligament reconstruction: a systematic review of the literature. 2015. 31(10): p. 2022-2034.

      ]. Studies by Helito et al, focusing on ALLR, would also corroborated this; the authors found a residual PS in 9.1% of patients who had ACLR and ALLR versus 35.5% in those who had ACLR alone for chronic ACL rupture [

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in chronic ACL injuries leads to better clinical outcomes than isolated ACL reconstruction. 2018. 26(12): p. 3652-3659.

      ]. In patients with generalised hyperlaxity, a residual PS was present in 26.7% of patients with ACLR and ALLR versus 51.7% for ACLR alone [

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in patients with anterior cruciate ligament injury and ligamentous hyperlaxity leads to better clinical stability and a lower failure rate than isolated anterior cruciate ligament reconstruction. 2019. 35(9): p. 2648-2654.

      ]. However, it is important to note that investigations have also shown that the PS phenomenon is multifactorial and that high-grade PS is generally associated with a secondary injury to a variety of structures in addition to the ACL[
      • Vaudreuil N.J.
      • et al.
      The Pivot Shift: Current Experimental Methodology and Clinical Utility for Anterior Cruciate Ligament Rupture and Associated Injury.
      ]. Two studies have demonstrated increased lateral compartment anterior translation and IR in the setting of lateral meniscus posterior root tears[
      • Lording T.
      • et al.
      Rotational Laxity Control by the Anterolateral Ligament and the Lateral Meniscus Is Dependent on Knee Flexion Angle: A Cadaveric Biomechanical Study.
      ,
      • Shybut T.B.
      • et al.
      Effect of lateral meniscal root tear on the stability of the anterior cruciate ligament-deficient knee.
      ]. These factors clearly need to be considered in the analysis and interpretation of what significance can be given to the PS grade clinically.
      The benefits of a combined procedure should be balanced against its downsides, namely complication rates, surgical time, and expense. Complications after combined ACLR and LEAP in the recent literature are relatively low overall, although as expected, they are slightly higher than in ACLR alone[
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ,
      • Feller J.A.
      • et al.
      Augmentation of Primary ACL Reconstruction With a Modified Ellison Lateral Extra-articular Tenodesis in High-Risk Patients: A Pilot Study.
      ]. Getgood et al reported a higher rate of complications with the addition of a modified Lemaire procedure; the complications related almost exclusively to hardware (14/298 in the combined cases versus 4/291 in isolated ACLR - 10 required removal of the staple for the LET)[
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ]. Sonnery-Cottet et al and Helitos et al showed no difference in complications rates using the ALLR [
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ,

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in patients with anterior cruciate ligament injury and ligamentous hyperlaxity leads to better clinical stability and a lower failure rate than isolated anterior cruciate ligament reconstruction. 2019. 35(9): p. 2648-2654.

      ,

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in chronic ACL injuries leads to better clinical outcomes than isolated ACL reconstruction. 2018. 26(12): p. 3652-3659.

      ].
      An ongoing concern is that LEAP may increase or expediate the development of osteoarthritis (OA) as a result of over-constraint or an increase in contact forces to the lateral compartment. In a 19-year follow-up study of ACLR comparing BPTB with or without LET, Castoldi et al showed that the LET group had half the graft failure rate of isolated BPTB but significantly more lateral compartment OA (59% versus 22% respectively). However, nearly half of the patients who developed the OA had received a lateral meniscectomy and there was a correlation between the meniscectomy and the development of OA [
      • Castoldi M.
      • et al.
      A Randomized Controlled Trial of Bone-Patellar Tendon-Bone Anterior Cruciate Ligament Reconstruction With and Without Lateral Extra-articular Tenodesis: 19-Year Clinical and Radiological Follow-up.
      ]. A recent systematic review by Devitt et al looking at the risk of OA more than 5 years after the index procedure the conclusion was that there was insufficient evidence to say that adding a LET increased the risk of OA at the medium term [
      • Devitt B.M.
      • et al.
      Combined anterior cruciate ligament reconstruction and lateral extra-articular tenodesis does not result in an increased rate of osteoarthritis: a systematic review and best evidence synthesis.
      ]. Finally, Viglietta et al reported a significantly higher risk of long-term OA was found with isolated ACLR than with ACLR combined with a LET procedure[
      • Viglietta E.
      • et al.
      ACL Reconstruction Combined With the Arnold-Coker Modification of the MacIntosh Lateral Extra-articular Tenodesis: Long-term Clinical and Radiological Outcomes.
      ].
      So, as interest in LEAP has risen in the past decade, the weight of clinical evidence has accumulated that in the right context these procedures will improve clinical outcomes and reduce rates of reinjury, with a low rate of complications. The first answer to our triumvirate of questions seems to suggest ‘yes’. It’s the answer to next two questions that are more challenging!

      What are the indications for using a lateral augmentation procedure?

      One approach to this conundrum, is to simply to add the procedure to every ACLR; the logic being that we don’t just ask bad drivers to wear seat belts! Whilst anecdotally the rate of use of LEAP seems to be rapidly increasing, few surgeons currently use it universally[
      • Madhan A.S.
      • et al.
      Trends in Anterolateral Ligament Reconstruction and Lateral Extra-articular Tenodesis With ACL Reconstruction in Children and Adolescents.
      ]. A more nuanced approach is to stratify each patient based upon their risk-profile for graft re-rupture, and to add the LEAP to an ACLR when both the surgeon and patient feel the added surgical time, more difficult early rehabilitation and potential complication rate warrants it.
      Marmura et al have demonstrated that the MOON risk calculator is a valid predictor of ACLR graft rupture and is appropriate for clinical practice[
      • Marmura H.
      • et al.
      Validation of a Risk Calculator to Personalize Graft Choice and Reduce Rupture Rates for Anterior Cruciate Ligament Reconstruction.
      ]; the model predictors for the risk calculator include age, sex, body mass index, sport played at the time of injury, Marx Activity Score, preoperative knee laxity, and graft type. Using data from the Stability study, performed by Getgood et al[
      • Getgood A.M.
      • et al.
      Lateral extra-articular tenodesis reduces failure of hamstring tendon autograft anterior cruciate ligament reconstruction: 2-year outcomes from the STABILITY study randomized clinical trial.
      ], the authors showed acceptable discriminative ability to detect patients that age, high-grade preoperative knee laxity, and graft type were significant predictors of graft rupture in young active patients in this study[
      • Marmura H.
      • et al.
      Validation of a Risk Calculator to Personalize Graft Choice and Reduce Rupture Rates for Anterior Cruciate Ligament Reconstruction.
      ]. They concluded that BPTB and the addition of LET to HT were protective against graft rupture versus HT autograft alone. The risk-weighting for each individual is not exclusive to these factors, and a number of authors have included additional indications for LEAP, including: generalised hyperlaxity, knee hyperextension, positive family history of ACL injury, history of reinjury to a contralateral ACLR, increased tibial sloped, elite athletes and chronic ACL injury[
      • Getgood A.
      • et al.
      The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting.
      ,
      • Sonnery-Cottet B.
      • et al.
      Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group.
      ,
      • Getgood A.M.J.
      • et al.
      Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial.
      ,
      • Feller J.A.
      • et al.
      Augmentation of Primary ACL Reconstruction With a Modified Ellison Lateral Extra-articular Tenodesis in High-Risk Patients: A Pilot Study.
      ,

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in patients with anterior cruciate ligament injury and ligamentous hyperlaxity leads to better clinical stability and a lower failure rate than isolated anterior cruciate ligament reconstruction. 2019. 35(9): p. 2648-2654.

      ,

      Helito, C.P., et al., Combined reconstruction of the anterolateral ligament in chronic ACL injuries leads to better clinical outcomes than isolated ACL reconstruction. 2018. 26(12): p. 3652-3659.

      ]. Box 3 provides a summary of commonly recognised risk factors for ACL graft rupture and proposed indications for a LEAP.(Box 1, Box 2)
      Key Articles
      • 1.
        Getgood, A., et al., The anterolateral complex of the knee: results from the International ALC Consensus Group Meeting. Knee Surg Sports Traumatol Arthrosc, 2019. 27(1): p. 166-176.
      • 2.
        Kaplan, E.B., The iliotibial tract; clinical and morphological significance. J Bone Joint Surg Am, 1958. 40-A(4): p. 817-32.
      • 3.
        Terry, G.C., J.C. Hughston, and L.A. Norwood, The anatomy of the iliopatellar band and iliotibial tract. Am J Sports Med, 1986. 14(1): p. 39-45.
      • 4.
        Inderhaug, E., et al., Biomechanical Comparison of Anterolateral Procedures Combined With Anterior Cruciate Ligament Reconstruction. The American Journal of Sports Medicine, 2016: p. 0363546516681555.
      • 5.
        Geeslin, A.G., et al., Anterolateral Knee Extra-articular Stabilizers: A Robotic Study Comparing Anterolateral Ligament Reconstruction and Modified Lemaire Lateral Extra-articular Tenodesis. Am J Sports Med, 2017: p. 363546517745268.
      • 6.
        Devitt, B.M., et al., The role of lateral extra-articular tenodesis in primary anterior cruciate ligament reconstruction: a systematic review with meta-analysis and best-evidence synthesis. Orthopaedic Journal of Sports Medicine, 2017. 5(10): p. 2325967117731767.
      • 7.
        Neri, T., et al., Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction. Journal of ISAKOS, 2021. 6(2): p. 74-81.
      • 8.
        Getgood, A.M., et al., Lateral extra-articular tenodesis reduces failure of hamstring tendon autograft anterior cruciate ligament reconstruction: 2-year outcomes from the STABILITY study randomized clinical trial. The American journal of sports medicine, 2020. 48(2): p. 285-297.
      • 9.
        Sonnery-Cottet, B., et al., Anterolateral Ligament Reconstruction Is Associated With Significantly Reduced ACL Graft Rupture Rates at a Minimum Follow-up of 2 Years: A Prospective Comparative Study of 502 Patients From the SANTI Study Group. Am J Sports Med, 2017. 45(7): p. 1547-1557.
      • 10.
        Claes, S., et al., Anatomy of the anterolateral ligament of the knee. J Anat, 2013. 223(4): p. 321-8.
      Potential pitfalls of biomechanical studies
      • Biomechanical studies are more likely to simulate knee examination in the clinic through manual tests rather that the on-field loads that the knee withstands during sporting activity
      • Results of biomechanical studies are representative of only a ‘time zero’ state and do not take into account subsequent healing, cyclic loading, and rehabilitation
      • The clinical pivot shift is a dynamic examination through a range of motion - biomechanical studies do not replicate in vivo kinematics of the pivot shift but only the coupled laxities
      • Most biomechanical cadaveric studies are performed using knees that were transected at the level of the mid-femur and mid-tibia – as such, the ITB had no proximal attachment and its only distal attachment to the femur was through the KF, which were sectioned along with the anterolateral capsule and the ALL to create a ‘worst-case scenario injury’ - this effectively removes any load through the ITB and effectively renders it defunct as a secondary stabiliser to the knee
      Key issues of patient selection for Lateral Extra-articular Augmentation Procedure
      Increased Risk of Anterior Crucilate Ligament (ACL) graft rupture
      • Joint hyperlaxity
      • Knee hyperextension (>10 degrees)
      • Elite athletes
      • Return to contact/pivoting sport
      • Chronic ACL deficiency (1 year)
      • High grade pivot shift
      • Contralateral ACL reconstruction failure
      • Meniscal deficiency – Ramp Lesion
      • Increased posterior tibial slop (>12 degrees)
      • Family history of ACL injury
      Recent radiological studies have suggested that MRI might potentially offer a tool to determine those patients with ALC injury that could predict those who could benefit from a LEAP in addition to ACLR[
      • Berthold D.P.
      • et al.
      High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury.
      ,
      • Balendra G.
      • et al.
      Anterolateral complex injuries occur in the majority of 'isolated' anterior cruciate ligament ruptures.
      ]. However, given the lack of consensus on diagnostic parameters for ALC injury and the lack of correlation with clinical examination of ALRL caution should be taken on using radiology evidence of ALC as an indication for a LEAP at this time[
      • Getgood A.
      Editorial Commentary: Magnetic Resonance Imaging of the Knee Anterolateral Ligament: Does It Really Matter?.
      ] [
      • Devitt B.M.
      • Batty L.M.
      High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury: Letter to the Editor.
      ,
      • Rauer T.
      • et al.
      The anterolateral capsule is infrequently damaged as evaluated arthroscopically in patients undergoing anatomic ACL reconstruction.
      ]. While the current literature does not yet answer this question of what are the specific indications for a LEAP conclusively, it would stand to reason that the more risk factors for ACL reinjury, the more benefit should be gained from performing it[
      • Getgood A.
      Editorial Commentary: Indications for Lateral Extra-Articular Tenodesis in Primary Anterior Cruciate Ligament Reconstruction.
      ]. For now, a risk-benefit analysis on a case-to-case basis is certainly good practice.

      Which lateral augmentation procedure should we use?

      The final decision is around which procedure should we use from a myriad of choices. There is much debate between the pros and cons of the LET versus ALLR, and between the different types of LET (deep Lemaire, superficial Lemaire, Macintosh, and Ellison). While there is good clinical and biomechanical evidence to support the use of any of LEAP, there is no clinical evidence to support the use of one over the other. Many surgeons tend to have their ‘favourite’ procedure based upon experience and their interpretation of the literature. There is often a difference in the choice of LEAP based on geography, which likely pertains to the influence of training in certain regions. Slette et al, in a fantastically illustrated systematic review, outlined 12 varieties of LEAP, which incidentally did not include the ALLR[
      • Slette E.L.
      • et al.
      Biomechanical Results of Lateral Extra-articular Tenodesis Procedures of the Knee: A Systematic Review.
      ]. These procedures were conceived by surgeons in North American and Europe, predominantly Italy and France, have been adopted internationally. However, putting aside personal preference and regional bias should we be choosing the specific LEAP based on the patient’s unique surgical considerations?
      An individual with chronic laxity or grade 3 PS may benefit from a greater degree of constraint than perhaps a young patient with an acute injured and treated ACL. A more distally based tenodesis may be more favourable in a skeletally immature patient to avoid the risk of growth plate injury on the femur. The concept of titrating the dose of constraint with each choice of LEAP is important to consider. Where the balance sits between the benefits of increased constraint against the potential effects of increased pressure on a vulnerable compartment is not clear. To date, there are only a handful of biomechanical studies to help us translate this information in the clinical setting. While there remains some disagreement around the precise amount of constraint afforded by the different LEAP, the relative amount of additional constraint to an ACLR and control of IR are mostly in agreement (Table 1).
      Table 1Relative effect on IR constraint of the tibia compared to normal knee kinematics with the addition of a variety of LEAP in addition to ACLR based on biomechanical studies [
      • Inderhaug E.
      • et al.
      Biomechanical Comparison of Anterolateral Procedures Combined With Anterior Cruciate Ligament Reconstruction.
      ,
      • Neri T.
      • et al.
      Different anterolateral procedures have variable impact on knee kinematics and stability when performed in combination with anterior cruciate ligament reconstruction.
      ].
      Constraint to IRNeri et alInderhaug et al
      Under-constraintALLR
      Normal constraintALLRMacIntosh
      Modified EllisonDeep Lemaire
      Over-constraintMacIntoshSuperficial Lemaire
      Superficial Lemaire
      Deep Lemaire
      IR – Internal Rotation, ALLR – Anterolateral ligament reconstruction
      Applying this to a clinical scenario in an algorithmic fashion may provide the solution by suggesting a specific surgical dose which is commensurate to the patient risk of reinjury; e.g. a surgeon may omit a LEAP ‘standard risk’ patient, add either an ALLR or modified Ellison procedure for a ‘moderate risk’ patient, and reserve a MacIntosh or modified Lemaire for ‘high risk’ patients. It is then up to us all to follow-up our patients properly to continually refine our decision-making accuracy. Only then will managing injury to the anterolateral complex become more simple.

      Conclusion

      The ALC of the knee is integral to knee kinematics, especially in the setting of ACL injury. A loss of integrity of the ALC coupled with ACL deficiency can give rise to persistent ALRL of the knee even despite ACLR. The addition of a LEAP to an ACLR has been shown to reduce ALRL and decrease the rates of ACL graft failure. The decision of which LEAP to choose and the indications for its use are not clear and should be made on a case-to-case basis depending on patient risk.

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