Anterolateral augmentation procedures during anterior cruciate ligament reconstructions in skeletally immature patients: Scoping review of surgical techniques and outcomes

Abstract Purpose Graft failure rates after anterior cruciate ligament reconstruction (ACLR) in children and adolescents are higher compared to adults. Anterolateral augmentation procedures have recently generated increased focus regarding their ability to reduce graft failure rates. Concerns in skeletally immatures are potential growth disturbances and overconstraint after anterolateral augmentation. The aim of this scoping review is to provide an overview of all current anterolateral augmentation procedures in skeletally immature patients and to discuss surgical techniques, clinical and biomechanical outcomes. Methods This scoping review was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta‐Analysis) statement extension for scoping reviews. On 22 December 2022, an information specialist performed a systematic literature search in Cochrane, PubMed (Medline) and EMBASE databases. Inclusion criteria were anterolateral augmentation procedures, including lateral extra‐articular tenodesis (LET) and anterolateral ligament reconstruction (ALLR), in combination with ACLR in skeletally immatures. Results Twenty studies were included after screening 1.485 abstracts. Seventeen studies describe LET techniques, four studies ALLR techniques and one study both techniques. Biomechanical data is scarce and shows conflicting results. Two studies compared ACLR with LET to ACLR in skeletally immatures with promising results in favour of the combined procedure. There were no differences in outcomes between LET and ALLR. Conclusions Several LET and ALLR techniques have been described for skeletally immature patients and the first clinical data on LET and ALLR is available, which showed promising results. Further research is necessary to evaluate the risk of growth disturbances and overconstraint in skeletally immatures. Level of Evidence Level IV.

The literature on ALLR or LET in skeletally immature children and adolescents is scarce [4,36].This might be due to the fear of inducing growth disturbances by performing an anterolateral augmentation procedure, which makes this a controversial topic with paediatric ACL.In a systematic review, Carrozzo et al. [4] evaluated outcomes of over-the-top techniques, which includes a LET in its techniques, in skeletally immature patients and found low graft failure, low growth disturbance and high return to sport rates [4].In addition to these LET techniques, several other anterolateral augmentation surgical techniques have been developed for transphyseal, all-epiphyseal or hybrid ACLRs [36,8,42].There is no current overview of these techniques and their outcomes.The aim of this scoping review is to provide an overview of all current anterolateral augmentation procedures, both additional to the intra-articular ACLR and as a continuation of the ACLR itself, in skeletally immature patients and to discuss biomechanical outcomes, surgical techniques and clinical outcomes.

METHODS
This scoping review was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) statement extension for scoping reviews [48].The general purpose for inducting a scoping review is to identify and map the available evidence and not to produce a critically appraised and synthesised answer to a specific question [32].

Selection criteria
Table 1 presents the inclusion and exclusion criteria applied to identify relevant articles.In cadaveric studies, both skeletally immatures and matures were eligible for inclusion due to ethical considerations and as not the effects on growth can be measured in cadavers, but the focus was on biomechanical outcomes.

Intervention
LET or ALLR techniques combined with a transphyseal ACLR, over-the-top ACLR, all-epiphyseal ACLR or hybrid ACLR (partial epiphyseal and transphyseal) were included in this review.LET essentially involves fixing the iliotibial tract (ITB) to the femur and exists in many different techniques, including (modified) Lemaire technique, Losee technique, MacIntosh reconstruction and Ellison distal ITB transfer [19,7,26,29].In an ALLR, a 'free graft' is used as graft for the ALL to restore the anatomy of the ALL [5,6].

Search strategy
On 22 December 2022, an information specialist (E.D.) performed a systematic literature search in Cochrane, PubMed (Medline) and EMBASE databases, as shown in Appendix S1.All published articles up to 22 December 2022 were considered eligible.The following terms, including synonyms and closely related words, were used as index terms or free-text words: 'anterior cruciate ligament reconstruction', 'transphyseal', 'allepiphyseal', 'over-the-top', 'lateral extra articular' and 'anterolateral ligament'.

Study selection
Two researchers (M.D., S. V.) independently screened the abstracts for eligibility by using the Rayyan QCRI app (http://rayyan.qrci.org)[35].A full-text version of all eligible studies was independently reviewed by the same two researchers (M.D., S. V.).All references of these studies were screened for additional eligible articles.Any disagreement between the reviewers during the different screening phases was resolved through discussion.

Data collection and charting process
Two authors (M.D., S. V.) independently charted all relevant data in a predefined Excel sheet.Data related to surgical technique, biomechanics and clinical outcome was gathered.Any disagreement about the interpretation of the results was resolved through discussion.
Specific parameters of the surgical technique used in each study were collected, including the femoral attachment, tibial attachment, graft type, fixation method, knee angle during fixation, graft tension at fixation and associated ligament reconstruction procedures, as well as biomechanical data if available.Findings from biomechanical studies of ALLR and LET were collected, including knee translation, rotational torque, kinematics and position of knee during testing, as well as other relevant reported results.Clinical outcomes, such as graft failure, growth disturbances and joint degeneration, were charted.

Synthesis of results
Results were divided based on the anterolateral augmentation technique, in LET and ALLR.Surgical techniques are described as descriptive as well as schematic in figures.Clinical outcomes are presented by means of tables.Outcomes of biomechanical studies were discussed separately, as studies compared LET to ALLR techniques.| 5 of 15 Marcacci over-the-top technique [24,40] and one on Ellison technique [12].A schematic representation of the different ACLR techniques in combination with LET is presented in Figure 2. Of the MacIntosh over-the-top technique two alternatives have been used namely using the ITB (Figure 2a) or a combination of ITB and hamstring (HS) graft (Figure 2b).An example of a Marcacci technique is shown in Figure 2c and a Lemaire LET with hybrid ACLR in Figure 2d.As no description of the ACLR technique was provided in the manuscript, no example of the Ellison LET technique is shown in Figure 2 [12].The Ellison LET technique involved a detachment of a strip of the ITB from Gerdy tubercle, reflection proximal to the lateral collateral ligament and fixation to Gerdy tubercle while passing the ITB strip under the lateral collateral ligament [12].

Clinical outcomes
Two studies [30,37] compared the results of ACLR with LET with ACLR without LET, of which the results are shown in Table 3.Both studies showed significant better knee anterior-posterior and rotational stability and reduced graft failure rates in the ACLR + LET groups versus isolated ACLR [30,37].Rate of growth disturbances was low in both studies for ACLR and ACLR + LET and high PROMs and return to sports rates were presented [30,37].
In eight studies, noncomparative clinical outcomes of an ACLR with LET are described (Table 4) [21,12,23,24,30,40,44,50,51].Mean age was ≤13 years in all studies except one study, which included both skeletally mature and immature patients [12].Only one study presented additional bone age [51] and two studies Tanner stages [22,40].All studies had a mean follow-up of ≥2 years.In most of these studies, additional LET resulted in relatively low graft failure rates (0%-17%), low growth disturbance rates (0%-17%) and high PROMs and return to sports rates.
ACLR + ALLR described by Foissey et al. and Morin et al. were similar and a schematic representation of this technique is shown in Figure 3a [14,31].Both techniques were hybrid ACLR with a continuous HS graft, which is used as ALLR [14,31].The continuous graft consisted of a three-strand semitendinosus and one-strand gracilis tendon [31].Two convergent, epiphyseal tunnels are created medial and lateral to Gerdy tubercle [31].For the ACLR, a femoral allepihyseal and tibial transphyseal were made [31].The ACLR graft is fixed in the femoral tunnel, and the ALL graft is passed in a posteroanterior fashion through the ALLR tibial tunnels under the iliotibial band and attached to the ACL traction wire at the femur in extension and neutral rotation [31].
Patel et al. [36] presented an ALLR technique, performed after a closed-socket, all-epiphyseal ACLR technique (Figure 3b) [36].In this ALLR technique, the ITB was used for both anterolateral capsular reinforcement and ALLR, by leaving the tibial insertion of the ITB intact, attaching the ITB posterior to the femoral ACL graft button and fixing the ITB at the midpoint between Gerdy&#39;s tubercle and the fibular head [36].The anterolateral capsular reinforcement was fixed with the knee in 90°of flexion and the ALLR in full extension [36].
Trentacosta et al. [47] presented an ALLR technique for skeletally immature patients in an adult cadaveric study [47].The ALLR technique was performed by using a prepared posterior tibialis tendon allograft, which was fixed to femur and tibia in tunnels with an anchor (Figure 3c) [47].The position of the tunnels was slightly proximal and posterior to the lateral epicondyle of the femur and 1 cm distal to the joint space on the midpoint between Gerdy&#39;s tubercle and the fibular head [47].Graft tensioning was performed with the knee in extension [47].

Clinical outcomes
In contrast with studies LET clinical outcomes on ALLR are very scarce.Only Foissey et al. [14] reported complications after ACLR + ALLR in comparison to the outcomes of hybrid ACLR + LET (Table 5).Mean age of these patients was 13.8 (±1.4) years and all bone ages were <13.5 years in girls and <15.5 years in boys.There were no differences in outcomes between ACLR + LET versus ACLR + ALLR [14].

DISCUSSION
The most important finding of this scoping review was that several LET and ALLR techniques have been described for skeletally immature patients and first clinical data on LET and ALLR is available.To this date, two studies compared ACLR with LET to ACLR in skeletally immature patients with promising results in favour of the combined procedure [30,37].
The role of the anterolateral structures of the knee in contributing to anterolateral rotatory stability of the knee has gained interest in recent literature [12,18,27,28].In response to this, the Anterolateral Complex Consensus Group suggested some possible indications for a LET procedure as an augmentation of an ACLR [45,12,16].These indications include: knee hyperextension greater than 10°, generalised hyperlaxity (Beighton score >4), grade 2 or higher pivot-shift test result or revision ACLr [45].Other risk factors for graft failure, such as age, sex, contralateral ACL injury and pivoting sport participation are taken into consideration for additional anterolateral augmentation [45].TA B L E 4 Clinical outcomes of LET.

Characteristics
Mean age (years)
There is currently little evidence to guide surgical indications for anterolateral augmentation with concurrent ACLR in skeletally immature patients [36].This population has an increased risk of graft failure because of their young age [2,36].Anterolateral augmentation during ACLR may therefore be considered to reduce graft failure rates in this population [4,30].Anterolateral augmentation procedures result however in additional surgical morbidity and can potentially result in overconstraint [21] and growth disturbances [40,51].Based on the currently available literature, graft failures rates might be lower in cases with anterolateral augmentation [30,37].It should be noted that evidence is still limited, especially on overconstraint and growth disturbances in this population.
The two studies that compared ACLR versus ACLR + LET showed promising results in favour of the combined procedure [30,37].In the study by Monaco et al. [30], no graft failures were found in the ACLR + LET group, which F I G U R E 3 Anterolateral ligament reconstruction (ALLR) techniques.(a) Hybrid anterior cruciate ligament reconstruction (ACLR) technique using triple semitendinosus (ST) graft and single gracilis (G) graft, which is continuous as ALLR graft [14,31].(b) All-epiphyseal hamstring ACLR using strip of ITB as ALLR and capsular reinforcement [36].(c) All-epiphyseal hamstring ACLR using posterior tibialis tendon as ALLR [47].
| 11 of 15     was significantly less than the 15% graft failure in the ACLR group [30].Post-ACLR laxity was also less in the ACLR + LET group.No differences in nongraft failurerelated reoperations or complications were found [30].Perelli et al. [37] had similar findings of graft failure rates of 15% (isolated ACLR) versus 6% (ACLR + LET) and similar rates of growth disturbances between the two groups.The anterior-posterior and rotational stability was also significantly better in the ACLR + LET group [37].Some of the noncomparative studies showed similar clinical results [12,23,22,24,40], although some studies found higher graft failure rates (14%-17%) [44,50] and growth disturbance rates (17%) in patients with over-the-top LET [51].Differences in the growth disturbance rates may be caused by the operative techniques, but also by the age of the patients and methods of determining growth disturbances.For example, Monaco et al. [30] included 16-year-old adolescents and evaluated growth disturbances clinically, whilst Wilson et al. [51] analysed adolescents with remaining growth of >18 months with lower limb radiographs [51].
To prevent these growth disturbances, all techniques described in this scoping review adjusted the anterolateral augmentation procedure to the physes.No sutures or staples were placed across open physes in any of the described techniques.Fixing the ITB proximal to the growth plate, however, could create a 'tenodesis effect' and possible growth disturbance, as it could act as a tether on the lateral side of the distal femoral physis and cause a valgus deformity [12,25].This phenomenon was demonstrated in a skeletally immature canine model when a transphyseal ACLR was excessively tensioned [12,9].Multiple studies fixed the LET proximal to the femoral growth plate, but only two of those studies evaluated growth disturbances [23,22,40,50,51].Wilson et al. [51] found that the operated leg had greater valgus angle compared to the nonoperated leg in 16.7% (n = 3) of the patients [51].In the over-the-top technique described by Di Sarsina et al. [40], none of the patients developed a valgus knee after ACLR with LET fixed proximal to the femoral physis [40].The 'tenodesis effect' is therefore yet to be determined in future studies.
Biomechanical studies showed different results on stability and overconstraint after LET [21,43,47].Evidence of biomechanical outcomes is low, due to small number of cadaveric knees.Probably due to ethical considerations, no studies were performed in skeletally immatures.Sena et al.ITB over-the-top ACLR with LET resulted in most studies in good stability and the addition of LET in the ITB over-the-top procedure improved stability [43].There are concerns regarding overconstraint, as it may lead to an increase in tibiofemoral contact pressures resulting in accelerated degeneration [34].Overconstraint in the ITB over-the-top technique is reported in two studies [43,47].This might be due to the degree of external rotation of the tibia during femoral fixation of the LET [17,47].Trentacosta et al. [47] fixed the ITB to the femur with the foot in neutral rotation, whilst Kennedy et al. [21] and Sena et al. [43] held the foot in 15°of external rotation.Thus, current biomechanical studies do not show a superior ACLR technique regarding knee kinematics, but overconstraint of the ITB over-the-top ACLR technique is a risk that is likely reduced by not placing the foot in external rotation while fixating the LET to the femur [47].
The addition of an ALLR in an all-epiphyseal ACLR did not improve rotational stability in the cadaveric knees [47].This seemed to be in contrast to the LET in the ITB over-the-top procedure, in which the stability of the knee was similar in ALL intact and ALL deficient states [47].The LET of the ITB over-thetop ACLR has therefore a stabilising effect on the knee [47].Clinical outcomes of hybrid ACLR + ALLR versus hybrid ACLR + LET showed no differences in complications [14].There are currently no other studies investigating clinical outcomes after ALLR in skeletally immature patients.Future studies have to determine whether LET or ALLR are best to use as anterolateral augmentation procedure in the skeletally immature.

Limitations
Limitations of this scoping review are due to the design of the included studies, which are technical notes, cadaveric studies, case series or retrospective cohort studies.There are currently no randomised controlled trials on anterolateral augmentation procedures in skeletally immature patients.There is not only a great variety in techniques of the ACLR and anterolateral augmentation procedures but also in the evaluation of outcomes such as growth disturbances, which makes comparing outcomes between studies difficult.

CONCLUSION
This scoping review is the first to show results and surgical techniques of LET and ALLR with ACLR in skeletally immatures.There are currently two studies . The specific locations of fixations of the grafts and fixations methods varied among ACLR techniques (see Appendix S3 for an overview).The LET was most commonly combined with an ACLR over-the-top F I G U R E 2 Different techniques of anterior cruciate ligament reconstruction (ACLR) in combination with lateral extra-articular tenodesis (LET).(a) An iliotibial tract (ITB) over-the-top technique with LET [23, 22], (b) a hybrid ACLR with ITB LET [51], (c) an extra-physeal hamstring over-the-top with LET [24, 40] and (d) a hybrid ACLR with hamstring tendons and ITB LET [14].

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TA B L E 1 Inclusion and exclusion criteria.dueto small numbers of cadaveric studies and cadaveric knees.ITB over-thetop ACLR with LET resulted in most studies in good stability and the addition of LET in the ITB over-the-top procedure improved rotational stability.Overconstraint in this technique is reported in two studies.Allepiphyseal ACLR with LET or ALLR showed different results regarding restoring stability of the knee.Additional ALLR in all-epiphyseal ACLR did not improve stability.
TA B L E 3 Clinical outcomes of isolated ACLR versus ACLR + LET.
Note: p Values are significant in bold.Abbreviations: ACLR, anterior cruciate ligament reconstruction; HSS Pedi-FABS, Hospital for Special Surgery Pediatric Functional Activity Brief Scale; KiRA, Kinematic Rapid Assessment; KOOS, Knee Injury and Osteoarthritis Outcome Score; LET, lateral extra-articular tenodesis; n.s., not significant; Pedi-IKDC, Pediatric International Knee Documentation Committee; SD, standard deviation.
Anterior Cruciate Ligament Return to Sport after Injury scale; HSS Pedi-FABS, Hospital for Special Surgery Pediatric Functional Activity Brief scale; KiRA, Kinematic Rapid Assessment; KOOS, Knee Injury and Osteoarthritis Outcome Score; LET, lateral extra-articular tenodesis; LLD, leg length discrepancies; LSI, Limb Symmetry Index; n.s., not significant; Pedi-IKDC, Pediatric International Knee Documentation Committee; SANE, Single Assessment Numeric Evaluation; SD, standard deviation.
Abbreviations: ACL-RSI, a Four skeletally immature patients.b Greater than 18 months remaining growth (n = 18).c Data available from 23 patients at 2 years follow-up.
[14] L E 5 Comparison of complications after ACLR + ALLR versus ACLR + LET by Foissey et al.[14].Required contralateral epiphysiodesis because of overgrowth.evaluatingACLR+LET versus isolated ACLR with promising results.There is little evidence on ALLR in skeletally immature patients and the effects of anterolateral augmentation on growth and overconstraint.AUTHOR CONTRIBUTIONSMartijn Dietvorst was involved in conception and design of the study, data extraction, analyses and interpretation and drafting the manuscript.Stéphanie Verhagen contributed to data extraction, interpretation of the data and revision of the manuscript.Marieke C. van der Steen was involved in conception and design of the study, data analysis and interpretation and revision of the manuscript.Florens Q. M. P. van Douveren performed revision of the manuscript.Rob P. A. Janssen was involved conception and design of the study, data interpretation and revision of the manuscript.All authors read and approved the final manuscript. a