The role of anterolateral complex surgery and slope-reducing osteotomies in revision ACL reconstructions: a narrative review

Introduction

Background

The anterior cruciate ligament (ACL) is the primary stabilizer of anterior tibial translation (ATT) and internal rotation of the knee. A smaller lateral tibial eminence height, a smaller femoral notch width index, and a posterior tibial slope (PTS) ≥12° are anatomic characteristics associated with an increased risk of ACL injury (1,2). As for revision ACL reconstruction (ACLR), factors like graft diameter, number of previous ACL tears, time to return to sport, and comorbid meniscal or ligament tears play a role in the potential etiology of an ACL graft tear (3). It is thought that augmentation of the anterolateral complex (ALC) could reduce stress on an ACLR revision graft, improve stability, and reduce the ACLR graft failure rate (4). The addition of a lateral extra-articular tenodesis (LET) or reconstruction of the anterolateral ligament (ALL) are two common methods of augmenting the ALC (5,6).

ALC augmentation in the setting of a revision ACLR or in patients with a high-grade pivot shift could improve outcomes and decrease the ACLR graft failure rate and clinical knee laxity. In addition, patients with a PTS ≥12° have a higher risk for ACL graft failure and consideration for a slope-reducing proximal tibial osteotomy (PTO) must be evaluated for in the work-up of all failed ACLRs. As the PTS increases, the force on an ACLR graft increases linearly when adjusted for flexion angle (7,8). Slope-reducing tibial osteotomies are an effective method of reducing posterior slope, leading to reduced ATT, and reducing the risk of ACLR failure (7,9).

Rationale and knowledge gap

Despite improvements in ACLR surgery and rehabilitation, graft failure rate remains unpredictable. Augmentation of the ALC and slope-reducing osteotomies are growing areas of interest for use in revision ACLR to prevent further graft failures. In addition, the role of increased PTS of ≥12° placing increased stress on an ACL graft which can contribute to its failure is being increasingly recognized.

Objective

The objective of this narrative review was to review the current literature relating to the roles of ALC augmentation procedures, namely LET and ALL reconstruction (ALLR), and slope-reducing tibial osteotomies in revision ACLR. We present this article in accordance with the Narrative Review reporting checklist (available at https://aoj.amegroups.com/article/view/10.21037/aoj-24-30/rc).

Methods

A narrative review was performed on the role of ALC surgery and slope-reducing tibial osteotomies in revision ACLRs, using sources from PubMed. Studies were selected based on a review of the title and abstract to determine the study’s relevance to the topic. Studies concerning PTS, revision ACLR, LET surgery, closing wedge osteotomies, or ALL anatomy, biomechanics, and reconstruction were considered. All studies were cross-referenced to find additional resources. Final consideration was given after a review of the full article. A summary of research strategies used for this article can be found in Table 1.

Incidence of revision ACLRs

Incidence

ACLR failure is a serious but not infrequent outcome. A meta-analysis conducted by Liukkonen et al. (10) calculated a pooled ACLR revision rate of 3.14% at 2 years follow-up out of over 50,000 patients. Bone-patellar tendon-bone (BTB) autografts had the lowest revision rate, followed by hamstring autografts (10). Rates of ACL graft failure can vary and are confounded by patient adherence to rehabilitation protocols. In a study of 354 patients under 20 years old who received primary hamstring tendon autografts, the graft tear rate was 18%, most of which occurred within the first 2 years postoperatively (11). The failure rate for male patients under 18 years old has been reported to be as high as 28.3% (11).

A systematic review investigating the risk of secondary injury to the ipsilateral knee ACL graft or contralateral knee ACL after rupture found pooled reinjury rates of 7% and 8% respectively. Rates for athletes who returned to sport after ACL injury were higher, with 8% ipsilateral injuries and 12% contralateral injuries (12). Paterno et al. (13) reported a secondary injury rate as high as 25% within 12 months of return to sport among young athletes who participated in high pivot-shift sports like soccer or basketball. Seventy-five percent of the injuries were to the contralateral ACL, and the majority of injured were female athletes (13).

Risk factors for ACL graft failure

Certain characteristics increase the likelihood of ACLR failures including being female or an adolescent, high body mass index (BMI), inconsistent adherence to ACL rehabilitation protocols, participation in pivot and cutting sports (e.g., basketball, alpine skiing, soccer), high medial and/or lateral PTS, and high baseline laxity (3,12-14). High grade preoperative knee laxity is associated with a 3.27 higher odds of graft failure, as well as increased odds of contralateral ACLR (3,15).

Lateral and/or medial PTS ≥12° are associated with increased risk of ACL tear and are considered pathologic (15). Even slight increases in medial or lateral PTS above normal can increase risk, with some sources advocating for the pathologic PTS cutoff to be ≥10° due to a significant increase in ACLR failures at and above that value. A study by Firth et al. (3) investigated risk factors for ACLR failure in high-risk patients, for instance young athletes, and found that patients with medial PTS >9.4° had 2.7 times greater odds of graft rupture compared to the group with medial PTS ≤9.4°. An increased angle of the medial and lateral PTS is independently associated with an increased risk of an ACL graft tear (14-16). Duerr et al. (16) performed an analysis to determine risk factors for ACL graft tears by matching a cohort of patients with ACL graft failure to patients with no evidence of ACL graft failure at 2 years follow-up. Of the ACL grafts that failed, the average medial and lateral PTS was 13.2° and 12.9° compared to 10.3° and 9.8° in patients with intact grafts, respectively. Lateral PTS ≥12° is also associated with additional injuries in the setting of ACL tears (Figure 1). Bernholt et al. (17) found that those with concomitant primary ACL tears and posterior lateral meniscal root tears had significantly higher medial and lateral PTS when controlling for other variables like lateral femoral condyle and lateral tibial plateau anatomy, weightbearing axis, and medial proximal tibial angle.

Figure 1 Lateral knee radiograph indicating the lateral posterior tibial slope angle (yellow arrow point to yellow line). The lateral PTS can be calculated by finding the angle between a line connecting the highest points of the lateral tibial plateaus and the anatomic axis of the tibia. The anatomic axis of the tibia can be found by drawing a line connecting the midpoints of the width of the bone at points 5 cm to the tibial plateau and 5 cm proximal to the tibial plafond. The PTS is calculated by subtracting that angle from 90°. The PTS in this image is 16.3°. PTS, posterior tibial slope.

Salmon et al. (18) reported on a cohort with over 20 years follow-up after ipsilateral hamstring autograft ACLR and reported that patients with a medial PTS of ≥12° were 11 times more likely to rupture their graft and 7 times more likely to rupture their contralateral graft compared to patients with non-ruptured grafts. Of their population, 20% had a medial PTS above 12°. In that same study, patients who had surgery when they were adolescents had a graft survival rate of 61%, compared to 86% among adults (18). Furthermore, patients who were both adolescents at the time of surgery and had a high PTS of ≥12° had a graft survival rate of only 22% (18).

Some of these risk factors, particularly increased knee laxity from previous ACLR failure and high PTS can be addressed with supplemental ALC surgery, such as LET, ALLR, and/or an anterior closing-wedge PTO (ACW-PTO).

The use of ALC procedures

In the ACL deficient knee, the ALL stabilizes the knee against internal rotation and an excessive pivot shift (19,20). It is thought that a residual internal rotation and/or positive pivot shift after ACLR could be due to damage to the ALC, such as a torn ALL (20). Nitri et al. (19), as a second part to the Rasmussen et al. (20), conducted a cadaveric biomechanical study that found that ACLR + ALLR, in the setting of combined ACL and ALL deficiency, significantly reduced internal rotation compared to isolated ACLR. This implies that an ALLR could be a viable option to provide additional stability to an ACLR that is higher risk, for instance in revision settings. The ALL is not the only structure in the ALC that provides rotational stability. The Kaplan fibers, a deep structure of the distal iliotibial band (ITB) consisting of two distinct bundles, serve as a stabilizer against excessive internal rotation in ACL-deficient knees (21). Geeslin et al. (22) sectioned the ACL then the ALL and Kaplan fibers to compare their roles in an ACL deficient knee. The investigators found that damage to the ALL and/or Kaplan fibers resulted in significantly increased ATT, pivot shift, and internal rotation. At higher angles of flexion (60–90°), sectioning of the Kaplan fibers lead to greater tibial internal rotation compared to when the ALL was sectioned. These results support the idea that isolated ACLR may not be sufficient to restore native knee kinematics, especially at higher degrees of flexion (22,23). Furthermore, because the ITB is commonly harvested for ALC procedures, care should be taken to not damage the Kaplan fibers.

In a meta-analysis conducted by Boksh et al. (24), ACLR graft failure was found to be lower in the augmented ACLR group compared to an isolated ACLR group. The addition of an ALLR or LET to a revision ACLR improved clinical outcomes as well, with that same study reporting improved International Knee Documentation Committee (IKDC) and Lysholm scores in the augmented revision ACLR group compared to the isolated revision ACLR group. In a different study of 78 patients who underwent a revision ACLR with or without a LET, the LET group were significantly more likely to return to sport at a minimum one-year follow-up (25).

High PTS is a common pathology among patients with failed ACLR grafts requiring revision. Of a cohort of 206 patients with ACLR graft insufficiencies, 35% had an increased medial PTS of 12° or higher (26). For patients <12° PTS, a LET can be considered as a less invasive option, especially if in the setting of a primary ACL tear (26). If the patient has both a high PTS and is undergoing a revision ACLR, both an ACW-PTO to address the increased slope and a LET or an ALLR to improve stability can be considered.

ALC surgical techniques

A LET or an ALLR can be used in ACLR revision cases with risk factors like an increased pivot shift, PTS ≥12°, or participation in a pivoting sport. These techniques are performed concomitantly with an ACLR to provide the knee with additional rotational stability to the knee and reduce the risk of an ACLR graft failure.

LET

A LET is an anterolateral procedure used to reduce stress on an ACLR graft and to reduce knee laxity. Typically, a LET is performed in the setting of revision ACLRs. Use of a LET in primary ACLR is considered for patients with high rotary laxity that cannot be addressed otherwise, Segond fractures, high grade Lachman exams, high grade pivot shift exams, or those at a higher risk of re-rupture like in young athletes who participate in pivoting sports (3,4,27). There are several common LET techniques, including the Lemaire, modified Lemaire, MacIntosh, Mueller, Marcacci and Zaffagnini, Losee, or Cocker-Arnold (28). The modified Lemaire procedure appears to be the most common current technique of choice and was used in many of studies reviewed (Figure 2) (4,29-31).

Figure 2 Depiction of the modified Lemaire LET technique. An 8 cm long by 1 cm wide band of distal ITB is left attached distally to Gerdy’s tubercle and is passed deep to the FCL. The LET is fixated proximally and posterior to the femoral attachment of the FCL at 30° of knee flexion. Reproduced with permission from Geeslin et al. (23). LET, lateral extra-articular tenodesis; ITB, iliotibial band; ALL, anterolateral ligament; FCL, fibular collateral ligament; PFL, popliteofibular ligament.

The modified Lemaire technique begins by dissecting down to the ITB and harvesting a central slip of the ITB, 8 cm long by 1 cm wide, leaving the distal attachment to Gerdy’s tubercle intact and taking care not to damage the deeper structures. The free end of the strip is whip-stitched, then passed under the fibular collateral ligament (FCL) and proximally fixated to the lateral femoral condyle, just posterior and proximal to the femoral attachment of the FCL (6). The LET is fixated to the femur using a bone staple, transosseus tunnel, or onlay anchor technique (30).

Other LET techniques are variations on a theme, typically using a strip of ITB distally attached to Gerdy’s tubercle with the proximal end of the strip redirected to a point posterior and proximal to the FCL femoral attachment or looped back down and attached to Gerdy’s tubercle (Figure 2) (28). The Arnold and Coker technique begins the same as the others, but instead of fixating to the femur, the ITB strip is passed beneath the FCL and popliteus tendon and sutured back down to Gerdy’s tubercle (32). Unlike the others, the Marcacci and Zaffagnini technique uses semitendinosus and gracilis tendons sutured together and passes them through the tibial ACLR tunnel to the lateral aspect of the knee, and then fixes the graft to Gerdy’s tubercle on the tibia (33).

ALLR

The ALL is a thickening of the lateral capsule that attaches to the femur 4.7 mm posterior and proximal to the femoral attachment of the FCL, and distally inserts midway between the fibular head and Gerdy’s tubercle (34). The ALL comes into tension with internal rotation at 30° of flexion. At higher degrees of flexion, 60–90°, it is thought that the Kaplan fibers play a bigger role to preventing internal rotation (22).

An ALLR is performed with a gracilis or ITB graft that is fixated approximately where the native ALL attaches (Figure 3) (5,35-37). The ALL graft is fixated with a 6 mm diameter interference screw in the femoral tunnel. The location for the femoral tunnel requires identification of the lateral epicondyle and the FCL femoral attachment. An anatomic tunnel is then reamed 5 mm posterior to the lateral epicondyle. Next the ACL reconstruction is performed (5,36). The tibial tunnel for the ALL is positioned 10 mm distal to the lateral joint line, midway between the anterior aspect of the fibular head and Gerdy’s tubercle (5,36,37). The angle of fixation for the ALL graft varied among the authors, with Tollefson et al. (5) recommending fixation in neutral rotation at 20° of flexion, while others recommend angles between 45–60° or even 60–90° (36,38).

Figure 3 Depiction of anterior (left) and lateral (right) views of a concomitant ALLR and ACLR. The ACLR is performed with a bone-patellar tendon-bone autograft, and the ALLR with a semitendinosus allograft. The ALLR graft is fixated with an interference screw distally to a point 1 cm distal to the joint line, midway between the fibular head and Gerdy’s tubercle, and proximally 4.7 mm posterior and proximal to the femoral attachment of the fibular collateral ligament. The graft is fixated with the knee at 20° of flexion in neutral rotation. Reproduced with permission from Nitri et al. (19). ALL, anterolateral ligament; ALLR, anterolateral ligament reconstruction; ACLR, anterior cruciate ligament reconstruction; FCL, fibular collateral ligament.

An ALLR is a distinct procedure from a lateral extra-articular tenodesis. Both are stabilizing procedures of the ALC but have some key differences. For one, an ALLR mimics a native structure, while LETs do not. LETs are generally performed with ITB grafts, while ALLRs often use gracilis hamstring grafts. A meta-analysis by Na et al. (39) found increased knee stiffness in patients with a LET + ACLR compared to an isolated ACLR, while the ALLR + ACLR group had no significant difference in knee stiffness compared to the isolated ACLR. Furthermore, a study by Helito et al. (40) that compared ALLR + ACLR to LET + ACLR found that the ALLR + ACLR group had improved Lysholm scores and shorter residual lateral pain, but no other significant differences between the groups. Kinematically, the differences between the two procedures are minimal. In the setting of an ACLR with ALL and Kaplan fiber deficiency, a LET resulted in a significant improvement over an ALLR in reducing internal rotation when it is fixated at 30° of flexion, but not at other angles (23,41). There is debate about whether ALLR contributes to significantly higher knee stiffness compared to isolated ACLR procedures. That said, it is better established that whatever stiffness an ALLR produces is less than that of a LET (42). This disparity could be due to the variety of LET procedures that may use nonanatomic attachment sites. As mentioned earlier, a LET reduces internal rotation more than an ALLR, so it is possible that stiffness is directly associated with that reduction. Currently there is no strong opinion on which ALC procedure is superior to the other (23,41). With that in mind, the decision on which should be performed should be made on a case-by-case basis.

LET outcomes

The addition of a LET to an ACLR is reported to significantly improve rotational stability and reduce ACLR graft rupture in patients at a high risk of ACLR failure (3,4). Getgood et al. (4) compared hamstring autograft primary ACLRs alone to the addition of a modified Lemaire LET among 15- to 25-year-old patients returning to sport who were at a high risk of re-rupture. The investigators found 11% of the ACLR group experienced graft ruptures, while the ACLR + LET group had a 4% failure rate. Persistent rotary laxity was also lower in the ACLR + LET group. The ACLR + LET group experienced more pain in the first 3 months post-operatively, but the difference equalized after that period.

Firth et al. conducted a study that investigated the risk factors for primary ACLR failure in high-risk patients who received either an isolated ACLR or ACLR + LET. Characteristics like graft diameter, age, sex, return to sport, PTS, knee laxity, and meniscus state were also monitored to address confounding variables. The authors found that the ACLR + LET group had a 60% lower chance of graft rupture than those with ACLR alone (3). The risk difference between ACLR and ACLR + LET was the same at all levels of tibial slope (3). If a LET is protective at all tibial slope levels, Firth et al. (3) suggested considering a LET before more invasive procedures to correct tibial slope, like slope-reducing osteotomies. Currently there are few studies investigating if the use of a LET can adequately address the increased risk of rupture due to high PTS. More research is needed in that area before definitive recommendations can be made.

There is some concern about a LET causing loss of range of motion by limiting internal rotation beyond normal kinematics (31,42). A cadaveric study by Herbst et al. (31) investigated the effects of an ACLR + LET on knee kinematics. The investigators found that an ACLR + LET better approximated normal knee kinematics when used for comorbid ACL and anterolateral capsule injuries, but over-constrained internal rotation at all degrees of knee flexion when the anterolateral capsule was intact (31). The implications of this potential over-constraint for clinical practice are not clear, especially considering that a LET could loosen over time with healing (23,42,43). A combined ACLR + LET in patients with meniscal pathology was found to decrease ATT compared to the isolated ACLR group at 6 months post-operatively, but not at 12 months (43). Gibbs et al. (43) suggested that the temporarily decreased ATT could be beneficial in protecting the healing ACL and meniscus in the short term and avoid the long-term complications of potential over-constraint.

ALLR outcomes

Outcomes for ALLR are overall good. Of a cohort of 548 patients receiving a quadruple hamstring graft and ALLR, 14 (2.6%) of the study population required ipsilateral ACL graft revision. Seventy-seven (13%) patients required an ipsilateral reoperation, of which 14 were related to ACLR graft failure, and the remaining 63 were hardware removals, meniscus operations, or treatment of arthrofibrosis or infection (44). Stiffness-related complications accounted for 22 of the 77 reoperations. Contralateral ACL rupture rates were close to the rate described in other studies at 8.6% (12,44). Lower ACLR revision rates than isolated ACLR and less stiffness than LETs is a common conclusion (40,44,45). Among young pivot-shift sport athletes, who are known to be at higher risk of ACL rupture, those who received simultaneous hamstring tendon ACLR and ALLR were 2.5 times less likely to rupture their primary ACL graft compared to those who received isolated BPTB grafts (45).

In the setting of a revision ACLR, the addition of an ALLR improves outcomes significantly. Helito et al. (40) compared isolated revision ACLR to ACLR + LET or ACLR + ALLR. The augmented groups showed a significantly lower failure rates, residual pivot shift, and ATT, which was measured by KT-1000 in mm (40). As for clinical outcomes, they also reported that patients who underwent an extra-articular reconstruction and ACLR revision reported greater and longer lasting lateral pain than the isolated ACL reconstruction group, but there was no difference in complications (40).

Sørenson et al. (46) conducted a 2-year study in the setting of revision ACLR and found no significant difference between an isolated ACLR and ACLR + ALLR groups in terms of clinical laxity, rotational knee stability, Knee Injury and Osteoarthritis Outcome Score (KOOS) or Tegner scores, or patient-reported outcomes. This result is partially supported by a meta-analysis conducted by Park et al. (47), which found that a combined ACLR + ALLR significantly improved graft failure, rotational stability, and IKDC scores compared to an isolated ACLR. The Tegner scores were not significantly different between the groups, and Lysholm scores were significantly different in studies with a moderate to high risk of bias, but insignificant in low risk of bias studies (47). Similar to LET, there is a reported risk of over-constraint of internal rotation for anatomic ALLR, regardless of which degree of flexion the knee was in during fixation (42).

The use of slope-reducing osteotomies for increased PTS

Slope-correcting tibial osteotomy

An ACW-PTO is performed by making an anterior incision over the knee, incorporating previous ACLR incisions as able. The authors’ preferred choice is a supratubercle osteotomy. In this technique, subperiosteal dissections are performed at the desired level of the osteotomy along both the medial tibia, with dissection deep to the medial collateral ligament, and lateral tibia with dissection to the anterior aspect of the proximal tibiofibular joint. Dissection deep to the patellar tendon attachment on the tibial tubercle is also performed. Fluoroscopy is then used to place 2 pins perpendicular to the tibial shaft just proximal to the patellar tendon attachment on the tibial tubercle. With a correction calculation of 1 mm for each degree of correction, two pins are placed proximal to the original pins at the desired correction amount and angled such that they intersect with the original guide pins at the posterior tibial cortex, the position of the pins is verified with fluoroscopy prior to removal of wedge (Figure 4). A small oscillating saw is then used to resect the wedge of bone between the guide pins. A small curette is used to remove bone to the posterior cortex. The knee is then hyperextended and the osteotomy is closed and fixed with 3 bone staples (48). Patients can be evaluated 6 months postoperatively with radiographs to assess if they are healed enough for a revision ACLR (48). In revision cases, autografts are preferred over allografts, and bone-patellar tendon-bone grafts or quadriceps tendon grafts with a patellar bone plug are common choices due to their relatively similar biomechanics to the native ACL as well as opportunity for bone-bone consolidation (10). Graft options for revision cases may be limited by previous graft choices.

Figure 4 Fluoroscopic image of the 4 guide pins used to mark the location of the ACW-PTO. The two distal guide pins are placed first on either side of the patellar tendon, just proximal to the patella attachment on the tibia. These should be perpendicular to the tibial shaft. The two proximal guide pins should be angled to meet the first two pins at the posterior cortex. The distance between the entry of the proximal and distal pins should equal the desired correction size, roughly 1 mm per 1° of desired correction. Using these pins as guides, the bone wedge can be resected. ACW-PTO, anterior closing wedge proximal tibial osteotomy.

The prevalence of PTS above 12° in patients with ACLR graft failures is high. Beel et al. (26) investigated the prevalence of medial PTS ≥12° in patients with ACLR graft failures. Seventy-eight percent of patients with three or more graft failures had a high medial PTS, which was significantly higher than those with one or two previous failures, prevalent in 32% and 38% respectively (26). The investigators of that study went on to recommend slope-correcting osteotomy in revision ACLR patients with pathological PTS and recurrent instability (26). Across several studies, the indications for a PTO include at least one ACL graft failure, excessive knee laxity, and a PTS ≥12° (29,49-52).

A combined ACW-PTO and ACLR can be performed in one or two stages. For one stage procedures the ACL tunnels are drilled prior to performing the ACW-PTO and after arthroscopic examination (52). Two stage surgeries involve performing the anterior closing wedge osteotomy and bone grafting the enlarged ACLR tunnels and then staging the revision surgery 6–8 months later once the bone grafted tunnels and closing wedge osteotomy have healed (48).

Slope-correcting tibial osteotomy outcomes

PTS and increased ACLR graft force have a linear relationship at all angles of flexion (8). So, in the setting of lateral or medial PTS ≥12°, a slope-reducing tibial osteotomy is indicated to reduce ACL graft stress and ultimately risk of failure, especially in revision cases. Overall outcomes for ACLR revision with ACW-PTO are good both clinically and functionally. A study by Tollefson et al. (9) found that ACW-PTO in revision ACLR patients with lateral PTS of >14° decreased PTS by 11.2° on average and resulted in a reduction of ATT by 8.9 mm on average [2024]. A meta-analysis by Bosco et al. (49) reported significantly improved Lysholm scores, knee laxity, and reduction in PTS and graft failures following combined ACW-PTO and revision ACLR.

In a retrospective study by Dejour et al. (50), whose cohort underwent simultaneous ACL revision and closing wedge osteotomy after two previous failed ACL grafts, the authors reported no postoperative complications or revisions. The Lysholm and IKDC scores both improved postoperatively, and flexion increased to a mean of 130°. Hyperextension of 5° was present in two patients (50). The medial tibial slope was reduced from a mean of 13° to between 2° and 8°. This was a small study including 9 knees, so larger scale studies are warranted to fully appreciate the outcomes (50). Rozinthe et al. (51) followed up on the Dejour et al. (50) study to include long term outcomes. The investigators performed additional follow-up at a minimum of 7 years postoperatively. Over that period, mean Lysholm and IKDC scores increased, and no revisions were recorded, like the original Dejour study (50,51).

In terms of complications, the two points of potential concern are iatrogenic patella alta and increased knee hyperextension. In a case-series of 68 patients who underwent revision ACLR with ACW-PTO, the patients experienced small but statistically significant changes to coronal alignment. Varus alignment increased by an average of 1°, and patellar height increased by 0.1 using the Caton-Deschamps Index (CDI) (Figure 5) (53). The investigators of the aforementioned study recommended fixing the osteotomy first with a lateral staple to help prevent induced varus (53).

Figure 5 Depiction of a 15° posterior tibial slope (A) corrected to 5° (B) using an anterior closing-wedge proximal tibial osteotomy closed with two proximal tibial staples. The measurements labeled “A” and “B” represent the distance from the lowest point of the patellar articular surface to the tibial articular surface, and the length of the patellar articular surface, respectively. The ratio of A to B is the Caton-Deschamps Index, a measure of patellar height. Reproduced with permission from Tollefson et al. (9).

Tollefson et al. (9) conducted a similar case series that included patients with at least one failed ACLR and lateral PTS >14°, who underwent a two-stage supra-tubercle ACW-PTO, with the goal of 4° PTS postoperatively, and revision ACLR. Tollefson et al. (9) found a significant increase in patellar height using the CDI on postoperative day 1, but no significant difference compared to preoperative values at 3- and 6-month. As for knee hyperextension, a small study including 22 patients followed patients for 2 years postoperatively after revision ACLR with concomitant LET and ACW-PTO (29). Three patients experienced non-symptomatic knee hyperextension. Other studies with similar procedures showed similar results but were small with under 10 patients each (50,52).

The addition of a LET in the setting of an ACW-PTO + ACLR may still be warranted. Pearce et al. (8) tested the addition of a LET to the ACLR and found for every 5° increase in PTS up to 15° there is a 12% to 17% increase in graft force when in the knee is in extension. Addition of a LET reduced graft force by 8.3% at 30° of knee flexion compared to isolated ACLR (8). Slope reduction was more impactful, and for every 5° of correction the graft force reduced by 17% to 22%. Reduction from 20° to 5° resulted in a 46% reduction in graft force (8).

Studies varied in the desired postoperative PTS correction angle for the ACW-PTO and whether to include a LET. Akoto et al. (29) chose to reduce PTS to physiological norm and supplement with a LET, whereas Dejour et al. (50) chose to reduce the PTS to 4° and forgo a LET. Also, these studies did not use a control group, so it is not completely clear if both components are strictly necessary to achieve their results. Further studies should be conducted to identify the optimal post-surgical correction angle for a high PTS. Inconsistencies in the literature include the postoperative correction goal angle of the ACW-PTO, whether to perform a one or two stage operation, whether to supplement with a LET, and the indications for the procedure itself.

Limitations

Limitations of this narrative review include completeness due to individual selection of the included studies by the authors based on topic and content, rather with an algorithm like a systematic review. The studies included were selected from a single database, which could lead to selection bias. There was a lack of consistency across studies of whether medial or lateral PTS should be measured in this setting. If a referenced study did not specify medial or lateral, or referred to both, the authors used the term “posterior tibial slope (PTS)” for the sake of simplicity.

Conclusions

The risk of ACLR failure is increased by risk factors like high tibial slope, preoperative knee laxity, and prior ACLR rupture. ALC procedures and slope-reducing osteotomies may be used to address these specific concerns and reduce the risk of graft rupture. For revision ACLR cases with lower PTS, augmentation with a LET or ALLR to reduce the risk of graft failure and improve rotational stability may be warranted. In the setting of a revision ACLR in patients with a high PTS of ≥12°, a concomitant ACW-PTO and ALC procedure should be considered to decrease the risk of an ACLR graft failure.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://aoj.amegroups.com/article/view/10.21037/aoj-24-30/rc

Peer Review File: Available at https://aoj.amegroups.com/article/view/10.21037/aoj-24-30/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-24-30/coif). R.F.L. serves as an unpaid editorial board member of Annals of Joint from September 2024 to December 2026. R.F.L. has research grants from Ossur, Smith & Nephew, AANA, and AOSSM; collects royalties from Ossur, Smith & Nephew, and Elsevier; collects consulting fees from Smith & Nephew and Ossur; has patents planned, issued, or pending from Smith & Nephew and Ossur; is on the editorial boards of AJSM, JEO, KSSTIA, JKS, IJSPT and OTSM. The other authors have no conflicts of interest to declare.

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