Superior rotational stability and lower re-ruptures rate after combined anterolateral and anterior cruciate ligament reconstruction compared to isolated anterior cruciate ligament reconstruction: a 2-year prospective randomized clinical trial

ABSTRACT Purpose The purpose of the current prospective randomized clinical trial (RCT) was to compare the clinical outcomes of combined anterior cruciate ligament (ACL) and anterolateral ligament (ALL) reconstruction with those of isolated ACL reconstruction and evaluate the re-rupture rate between the two study groups. Methods This prospective RCT included 58 patients (43 men and 15 women) who underwent ACL reconstruction, either isolated (Group I: 26 patients) or combined with the ALL reconstruction (Group II: 32 patients). Preoperatively, the two groups differed in age and rate of medial meniscal injuries. The patients were evaluated preoperatively and postoperatively during the time points corresponding to 6 (T1) weeks, 12 (T2) weeks, 6 (T3) months, 12 (T4) months, and 24 (T5) months. The evaluation included the clinical examination (comprising Lachman test, Pivot Shift test, Range of Motion, and Rolimeter differential anterior laxity), the objective clinical score (Objective IKDC [The International Knee Documentation Committee] score), and the subjective clinical scores (comprising Subjective IKDC score, Lysholm score, and Tegner activity score). The postoperative complications of all the patients were recorded. Results Both the groups reported a significant improvement in clinical scores during the final follow-up as compared to the preoperative value (p < 0.05). The only differences between the two groups were observed with respect to the pivot shift test during each follow-up, wherein more patients from group I reported a pivot shift test grade I as compared to group II (p < 0.05). Three patients from group I reported a re-rupture of the operated knee, whereas no patients from group II reported new ruptures (p = 0.041). Conclusions Combined ACL and ALL reconstruction has proven to be more effective in obtaining a high grade of rotational knee stability during mid-term follow-up as compared to isolated ACL reconstruction along with a significantly lower rate of re-ruptures. Level of Evidence Level I: Randomized Clinical Trial Registration researchregistry5873: www.researchregistry.com


Introduction
Isolated anterior cruciate ligament reconstruction is a wellestablished procedure. However, it may affect individuals in the long-term due to persistent rotational instability occurring in up to 30% of the patients. Rotational instability may be responsible for recurrent ACL injuries, secondary chondral or meniscal injuries, and difficulties in terms of returning to activities concerning pivoting sports [1][2][3][4].
Double-bundle ACL techniques or reconstruction of the peripheral anterolateral structures of the knee can be used for improved rotational control. However, double-bundle ACL reconstruction is not associated with superior clinical outcomes despite the improved biomechanics [Meredick, Samuelsson]. As demonstrated by many recent publications, the increased lever arm of the peripherally located anterolateral structures of the knee explains the possibility of a better control of the rotational instability compared to the centrally located ACL [5][6][7][8]. According to recent publications, the performance of a lateral extra-articular procedure is not associated with a significant overconstraint of the lateral femorotibial compartment of the knee [9][10][11].
The anterolateral ligament (ALL) is an individualized ligamentous structure located in the anterolateral region of the knee. It originates in the femur, proximal, and posterior to the lateral epicondyle and inserts in the tibia, posterior to the center of Gerdy's tubercle, and proximal to the anterior margin of the fibular head [12][13][14]. Despite the various publications regarding the anatomy and biomechanics of the anterolateral ligament, only a few clinical studies were published [8,[15][16][17][18][19][20][21].
The purpose of the current prospective randomized clinical trial was to compare the clinical outcomes of combined ACL and ALL reconstruction with those of isolated ACL reconstruction and evaluate the re-rupture rate between the two study groups.

Material and methods
The Institutional Review Board's ethical approval and informed consent were obtained from the participants before the start of the study and registered in the Research Registry (resear-chregistry5873: www.researchregistry.com). The study was conducted following the CONSORT (Consolidated Standards of Reporting Trials) protocol for RCT [22].
This prospective randomized study included 58 patients who underwent ACL reconstruction, either isolated or combined with the ALL reconstruction in a single-center study, with a minimum of a 2-year follow-up.
The inclusion criteria were as follows: the presence of a unilateral primary ACL tear in skeletally mature patients, preoperative pivot shift test grade II or III, participation in high grade pivoting sports, and chronic ACL lesion. The exclusion criteria were as follows: recurrent ACL tears, previous surgery of the affected knee, presence of multi-ligament injuries in the knee, necessity to associate an extra-articular procedure other than ALL reconstruction, and rheumatoid arthritis.
The exclusion criteria did not consider concomitant meniscal surgery (meniscectomy or meniscal suture) or cartilage treatment (microfracture or debridement). All the procedures were performed by the same surgeon (ȘM). All surgical interventions were carried out using the technique previously described [7,20,23,24].
The participants were randomized using concealed numbered envelopes containing either ACL or ACL+ALL marked pieces of paper [25]. The surgeon opened the envelope just before the surgery and informed the patient about the graft type post-surgery. As the surgery-induced scars were procedure-specific, the blinding of surgeons, patients, or evaluators was not possible. Group I (control group) included 28 patients with isolated ACL reconstruction, and group II (study group) consisted of 32 patients with combined ACL and ALL reconstruction.
A total of 58 patients were included in the study, out of which 26 were present in group I and 32 in group II. Preoperatively, the two groups differed in age (Group I: 34.00 ± 5.61 years; Group II: 28.84 ± 7.53 years; p = 0.005) and rate of medial meniscal injuries (Group I: 21; Group II: 14; p = 0.007). The demographic data are reported in Table 1.

Surgical technique
The surgical procedure is performed with the patient positioned supine with a padded tourniquet applied in the proximal region of the thigh. Two posts are then attached to the surgical table, the first lateral to the proximal thigh and the second as a foot roll meant to maintain 90 degrees of knee flexion. Hamstring graft harvesting is then performed by using a 2-cm skin incision. The semitendinosus tendon is kept attached to obtain a double tibial fixation and a better vascularization of the graft, while the gracilis tendon is whipstitched with a traction suture, detached, and used both for ACL and ALL graft preparation. Two stab incisions are used to prepare a V-shaped tibial tunnel, the first being positioned at the level of the Gerdy tubercle and the second half-way between the Gerdy tubercle and the anterior margin of the peroneal head to replicate the large native tibial insertion of the ALL. A 2-cm incision is centered over the lateral epicondyle and is meant for ACL femoral tunnel drilling. This incision is used for an outside-in drilling of the femoral tunnel with the lateral starting point located posterior and proximal to the lateral epicondyle, corresponding to the femoral origin of the ALL. Tibial tunnel is drilled outside-in by using the graft harvesting incision. The semitendinosus tendon is tripled, and the gracilis tendon is sutured over the tripled semitendinosus graft to prepare the ACL graft. The ALL graft consists of the remaining gracilis tendon. The ACL graft is pulled from the distal to proximal, and the fixation is performed with bioabsorbable screws first on the tibial side and then on the femoral side with 30 degrees flexion and posterior drawer. The ALL graft is pulled deep into the ilio-tibial band from proximal to distal through the V-shaped tibial tunnel and re-routed proximally to its femoral origin located at the lateral entry point of the femoral tunnel. Fixation is performed by using the ACL traction sutures in full extension and neutral rotation [26].

Postoperative rehabilitation
Isometric quadriceps contractions start the second day after surgery. The range of motion from 0 to 90 degrees is permitted during the first postoperative week, 0 to 120 degrees during the second week followed by a progressive increase to obtain the full range of motion at 6 weeks postoperatively. Progressive weight bearing as tolerated is allowed, starting with the 2nd day after surgery. A return is allowed at 3, 6, and 8 to 9 months postoperatively to nonpivoting and noncontact sports, pivoting and noncontact sports, and contact and pivoting sports, respectively. In case of meniscal suture, the ROM was limited to 60 degrees in the first week and 90 degrees in the 2nd week and so on with weight-bearing, as tolerated [26].

Clinical evaluation
The clinical assessments were performed before surgery (T 0 ) and after surgery during the time points corresponding to 6 (T 1 ) weeks, 12 (T 2 ) weeks, 6 (T 3 ) months, 12 (T 4 ) months, and 24 (T 5 ) by two independent assessors who were not involved in the clinical management of the patients (included surgery). This protocol included the clinical examination (comprising Lachman test, Pivot Shift test, Range of Motion [ROM], and Rolimeter differential anterior laxity), the objective clinical scores (Objective IKDC [The International Knee Documentation Committee] score), and the subjective clinical scores (comprising Subjective IKDC score, Lysholm score, and Tegner activity score).
The Lachman test is a specific clinical exam technique used to evaluate patients with a suspected ACL injury. The test relies on proper positioning and technique and is regarded as the most sensitive test for diagnosing acute ACL injuries [27].
The pivot shift test assesses for anterolateral rotatory instability of the knee. It is a very useful test to determine if the patient will have a symptomatic ACL tear or not. With this test, the examiner applies an internal rotation and valgus force to the extended knee, and if there is an ACL tear, the tibia will usually sublux anterolaterally on the femur [28].
The ROM (flexion and extension) was evaluated using a standard longarm goniometer (Baseline Plastic Goniometers -Fabrication Enterprises) as reported by Hancock et al. ROM was measured twice following a cycle of joint flexion and extension [29,30]*.
Differential anterior laxity was measured pre-and postoperatively by the Rolimeter ® device, with three successive measurements per knee, in maximal manual anterior drawer [31]. The International Knee Documentation Committee (IKDC Questionnaire) is a knee-specific patient-reported outcome measure. It's considered to be one of the most reliable outcome reporting tools in its category and was one of the instruments used in the popular MOON study. IKDC has been subjected to a rigorous statistical evaluation and has proven to be a valid and responsive patient-reported outcome measure (PROM) [32].
The Lyshom Knee Scoring Scale is a patient-reported instrument that consists of subscales for pain, instability, locking, swelling, limping, stair climbing, squatting, and the need for support. Scores range from 0 (worse disability) to 100 (less disability) [33].
The Tegner activity scale is a one-item score that graded activity based on work and sports activities on a scale of 0 to 10. Zero represents disability because of knee problems and 10 represents national or international-level soccer [34].
The study groups were compared in terms of the evaluated parameters at all the follow-up intervals. During the final follow-up, only the rate of re-ruptures, the Subjective IKDC score, the Lysholm score, and the Tegner score were evaluated. Additionally, the postoperative complications of all the patients were recorded.

Statistical analysis
Summary statistics are presented as mean and standard deviation (SD) or absolute frequency and percentage. To assess the differences between ACL and ACL+ALL, a t-test was carried out, whereas for categorical variables, a chi-square test or a Fisher's exact test was performed after testing the distribution of continuous variables. A mixed model was used to test the possible score changes over time because it allows the testing of the covariance structure among repeated measures. The compound symmetry, autoregressive, Toeplitz, Huynh-Feldt, and unstructured covariance structures were tested; the unstructured covariance structure was evaluated as the best covariance structure using the likelihood ratio test and Akaike information criterion. Wilcoxon signed rank test was used in the case of ordinal scores. Bonferroni adjustment was applied for multiple comparisons. A Fisher's exact test was used to assess the difference in the rate of re-ruptures between groups; the correlation among variables was analyzed based on variable distribution using Pearson or Spearman correlations, whichever is appropriate. All the tests were two-sided and a p-value of less than 0.05 was considered statistically significant. Statistical analyses were conducted in R version 4.1.1 and SAS/STAT 9.3.

Sample size
A total of 52 subjects were required (26 for each group) to compare the Subjective IKDC between ACL and ACL+ALL using a two-sided t-test, assuming a mean difference of 16, a standard deviation of 20 for both the groups, a 5% alpha, and an 80% power. Given the same parameters, there was an 88% probability for this sample to detect a difference between follow-up measurements. Additional subjects were recruited to ensure statistical significance in case of adverse events.

Categorical indices (Lachman test, pivot shift test, objective IKDC)
Both the groups reported a significant improvement in categorical indices during the final follow-up as compared to the preoperative value (p < 0.05). The only differences between the two groups were observed with respect to the pivot shift test during each follow-up, wherein more patients from group I reported a pivot shift test grade I as compared to Group II (p < 0.05), and in terms of the surgical time (Group I: 72.58 ± 11.92 minutes; Group II: 93.38 ± 15.06 minutes; p < 0.001). Detailed results are reported in Table 2.

Continuous indices (tegner score, subjective IKDC, lysholm score, rollimeter test, range of motion)
Both the groups reported a significant improvement in categorical indices during the final follow-up as compared to the preoperative value (p < 0.05). There were no statistically significant differences between the two groups during any of the follow-ups (p > 0.05). Detailed results are reported in Table 3.

Re-ruptures
Three patients from group I reported a re-rupture of the ACL on the operated knee, while no patients from group II reported new ruptures with a statistically significant difference (p = 0.041).
The three re-rutpures occurred respectively at 18, 20 and 21 months after surgery; in the first two cases the patient was a male, while in the other one a female. In all cases, patients had concomitant meniscus injury (for the first two both medial and lateral, for the third one only lateral).

Discussion
The most important finding of the current study is that there was superior rotational stability in case of the combined ACL and ALL reconstruction group as compared to the isolated ACL reconstruction, which is demonstrated by the Pivot Shift test. Moreover, the isolated ACL reconstruction reported a significantly higher incidence of re-ruptures during the follow-up period.
Several previously published papers have confirmed the superiority of combined reconstruction.
A recent systematic review analzyed failure rates and clinical outcomes after combined ACL/ALL reconstruction with percentage ranging from 2.7% to 11.1% [35]. These results are significantly higher compared with our study; this can be explained by the fact that no postoperative MRI was performed at the final follow-up, and if some patients had experienced ACL re-rupture, this could be hidden clinically by ALL reconstruction [36]. In fact, the ALL functions as a secondary stabilizer to the ACL in resisting anterior tibial translation and internal tibial rotation and in preventing the knee pivot-shift phenomenon [37]. Most biomechanical studies have demonstrated a significant effect of the ALL in providing rotational control of the knee during the simulated pivot shift. The function of the ALL is most important in ACL-deficient states, with most biomechanical studies demonstrating that in the presence of ACL insufficiency, detaching or sectioning the ALL in cadaveric knee specimens results in a significant effect on anteroposterior stability as well as a significant increase in internal rotation [37] In our RCT, furthermore, we found an elevated number of meniscal injuries, but this data is in line with current literature, in fact, meniscus injuries are common in patients with ACL tears, with as many as 65% of ACL injuries presenting with concomitant meniscus tears [38]. Lateral meniscus tears occur slightly more frequently than medial tears with acute ACL injuries (56% vs 44%, respectively), and medial meniscus tears are more common with chronic ACL injuries [38].
Kunze et al. recently published a systematic review and meta-analysis of ALL reconstruction techniques, biomechanical properties, and clinical outcomes [39]. A total of 46 articles were identified that demonstrated that combined ACL/ALL reconstruction restored anterior translation, internal rotation, and pivot shift in this case was better than ACL reconstruction alone. Furthermore, the clinical outcomes after meta-analysis also favored the combined ACL/ALL reconstruction [39].
In 2021, Yin et al. compared the effectiveness of combined ACL/ALL reconstruction with isolated ACLR for treating patients suffering from an injured ACL [40]. A total of six articles with 460 study subjects were included, wherein 193 patients were present in the ACL+ALL reconstruction group and 267 patients in the ACL reconstruction group. The results of the meta-analysis revealed that the combined ACL and ALL reconstruction group had significantly lower measured KT value, Lachman test positive-rate, Pivot Shift test positiverate, and graft rupture rate as compared to the ACL reconstruction group. The ACL+ALL reconstruction group had a higher IKDC and Lysholm score, but there were no significant differences in terms of infections and other complication rates between the two groups [40].
In 2018, Rosenstiel et al. evaluated the clinical outcomes in professional athletes after a combined ACL and ALL reconstruction at a minimum follow-up of 2 years [18]. Seventy-two professional athletes underwent primary ACL and ALL reconstruction. The preoperative side-to-side anteroposterior laxity significantly decreased after surgery. The pivot-shift grade evolved from 16 grade I (22.8%) and 54 grade II or III (77.2%) preoperatively to 66 absent pivot-shift (94.3%) and 4 grade I post surgery. After a year of surgery, 60 athletes (85.7%) returned to professional sports with a mean time interval of 7.9 months. All clinical scores (Objective and Subjective IKDC, Lysholm score, Tegner Score) improved during the final follow-up. Eleven patients (15.7%) underwent a subsequent ipsilateral reoperation including 4 (5.7%) revision ACL reconstructions. The authors concluded that combined ACL and ALL reconstruction is associated with excellent outcomes in the case of professional athletes with respect to graft rupture rates, return to sports, knee stability, and reoperation rates after injury [18].
A similar study was performed by Hamido et al. to compare the outcomes of ACL reconstruction with those of combined ACL and ALL reconstruction in ACL-deficient knees [16]. One hundred and two patients were available for follow-up: 52 from group A (isolated ACL) and 50 from group B (combined ACL/ALL). Postoperatively, the pivot shift was normal in 43 (82.7%) and 48 (96%) patients from groups A and B, respectively (p < 0.001). The median instrumented knee laxity was 2.5 ± 0.7 mm in the patients from group A and 1.2 ± 0.7 mm in the patients from group B (p < 0.001). Additionally, 44 (84.6%) patients from group A exhibited normal IKDC scores, and 3 (5.8%) revealed nearly normal scores, while 48 (96.0%) patients from group B exhibited normal IKDC scores, and 2 (4%) showed nearly normal scores (p < 0.001). The RCT confirmed that the combined ACL and ALL reconstruction resulted in better clinical and functional outcomes than the isolated ACLR as evidenced by decreased rotational instability and instrumented knee laxity, lower graft rupture rates, and higher postoperative IKDC scores [16].
In order to better understand how ALL helps knee stability post ACL reconstruction, it is important to analyze the biomechanics of this ligament. The ALL restrains the tibial intrarotation but not the anterior tibial translation, which is primarily controlled by the ACL. The ACL seems to control the tibial IR in early flexion (0°-30°), while the ALL takes over in deeper flexion (30°-90°) [41].
Conflicting studies argue that the ALL may be a secondary knee stabilizer as it bears loads that are only beyond normal physiological motion in an ACL-deficient knee [42].
However, concern exists that lateral extra-articular tenodesis (LET) procedures may overconstrain the knee, which may cause an increase in the tibiofemoral contact pressures and possibly lead to accelerated knee osteoarthritis. Shimakawa et al. demonstrated that under different loading conditions (0°, 30°, 60°, and 90°), LET did not significantly alter the lateral compartment contact pressures when performed in conjunction with ACLR within the setting of an intact or posterior horn-deficient lateral meniscus [10].
Novaretti et al. quantified the effects of lateral extraarticular tenodesis on the tibiofemoral compartment contact area and pressures, knee kinematics, and forces. They concluded that there was no overconstraint of the knee, increase in contact pressure, or decrease in contact area in the tibiofemoral lateral compartment following the LET procedure with a semitendinosus graft for a deficient ACL. The lack of knee overconstraint without significant increases in lateral compartment pressures indicates that if a LET with semitendinosus graft is not over tensioned, there may not be accelerated degenerative changes in the lateral compartment after this procedure [9].
Neri et al. conducted a pilot biomechanical study to compare the lateral tibiofemoral contact pressures after the most commonly used anterolateral procedures. Compared to isolated ACLR, the addition of ALL reconstruction did not increase the overall LTF contact pressure through the full range of flexion for the internal rotation condition. Conversely, deep Lemaire, superficial Lemaire, and modified MacIntosh procedure increase the overall lateral tibiofemoral contact pressure compared to ACLR in intrarotation [43].
The current study has several limitations. First, the followup period of the current study is relatively short to evaluate the potential development of the arthritic changes in the knee joint. However, the final follow-up interval of 24 months is enough to adequately evaluate the functional results and return to the pre-traumatic level of sports related activities. Second, the study groups used for detecting discrete differences between them are relatively small. Third, the time elapsed between injury and surgery was not evaluated; this may affect the nature of meniscal injuries [44].
Finally, concomitant surgeries such as meniscal or cartilage treatments have not been considered in the exclusion criteria, thereby creating a potential bias in the patients' evaluation, even though there were no significant differences in the incidence of associated lesions.

Conclusions
Combined ACL and ALL reconstruction has proven to be more effective in obtaining a high grade of rotational knee stability during mid-term follow-up as compared to isolated ACL reconstruction along with a significantly lower rate of reruptures.