Anterior Cruciate Ligament Healing Research Articles

A New Tissue Engineering Strategy to Promote Tendon-bone Healing: Regulation of Osteogenic and Chondrogenic Differentiation of Tendon-derived Stem Cells.

In the field of sports medicine, repair surgery for anterior cruciate ligament (ACL) and rotator cuff (RC) injuries are remarkably common. Despite the availability of relatively effective treatment modalities, outcomes often fall short of expectations. This comprehensive review aims to thoroughly examine current strategies employed to promote tendon-bone healing and analyze pertinent preclinical and clinical research. Amidst ongoing investigations, tendon-derived stem cells (TDSCs), which have comparatively limited prior exploration, have garnered increasing attention in the context of tendon-bone healing, emerging as a promising cell type for regenerative therapies. This review article delves into the potential of combining TDSCs with tissue engineering methods, with ACL reconstruction as the main focus. It comprehensively reviews relevant research on ACL and RC healing to address the issues of graft healing and bone tunnel integration. To optimize tendon-bone healing outcomes, our emphasis lies in not only reconstructing the original microstructure of the tendon-bone interface but also achieving proper bone tunnel integration, encompassing both cartilage and bone formation. In this endeavor, we thoroughly analyze the transcriptional and molecular regulatory variables governing TDSCs differentiation, incorporating a retrospective analysis utilizing single-cell sequencing, with the aim of unearthing relevant signaling pathways and processes. By presenting a novel strategy rooted in TDSCs-driven osteogenic and chondrogenic differentiation for tendon-bone healing, this study paves the way for potential future research avenues and promising therapeutic applications. It is anticipated that the findings herein will contribute to advancing the field of tendon-bone healing and foster the exploration of TDSCs as a viable option for regenerative therapies in the future.

Enhancing tendon-bone integration and healing with advanced multi-layer nanofiber-reinforced 3D scaffolds for acellular tendon complexes

Advancements in tissue engineering are crucial for successfully healing tendon-bone connections, especially in situations like anterior cruciate ligament (ACL) restoration. This study presents a new and innovative three-dimensional scaffold, reinforced with nanofibers, that is specifically intended for acellular tendon complexes. The scaffold consists of a distinct layered arrangement comprising an acellular tendon core, a middle layer of polyurethane/type I collagen (PU/Col I) yarn, and an outside layer of poly (L-lactic acid)/bioactive glass (PLLA/BG) nanofiber membrane. Every layer is designed to fulfill specific yet harmonious purposes. The acellular tendon core is a solid structural base and a favorable environment for tendon cell functions, resulting in considerable tensile strength. The central PU/Col I yarn layer is vital in promoting the tendinogenic differentiation of stem cells derived from tendons and increasing the expression of critical tendinogenic factors. The external PLLA/BG nanofiber membrane fosters the process of bone marrow mesenchymal stem cells differentiating into bone cells and enhances the expression of markers associated with bone formation. Our scaffold's biocompatibility and multi-functional design were confirmed through extensive in vivo evaluations, such as histological staining and biomechanical analyses. These assessments combined showed notable enhancements in ACL repair and healing. This study emphasizes the promise of multi-layered nanofiber scaffolds in orthopedic tissue engineering and also introduces new possibilities for the creation of improved materials for regenerating the tendon-bone interface.

Regenerative Anterior Cruciate Ligament Healing in Youth and Adolescent Athletes: The Emerging Age of Recovery Science.

Anterior cruciate ligament (ACL) injuries mainly arise from non-contact mechanisms during sport performance, with most injuries occurring among youth or adolescent-age athletes, particularly females. The growing popularity of elite-level sport training has increased the total volume, intensity and frequency of exercise and competition loading to levels that may exceed natural healing capacity. Growing evidence suggests that the prevailing mechanism that leads to non-contact ACL injury from sudden mechanical fatigue failure may be accumulated microtrauma. Given the consequences of primary ACL injury on the future health and quality of life of youth and adolescent athletes, the objective of this review is to identify key "recovery science" factors that can help prevent these injuries. Recovery science is any aspect of sports training (type, volume, intensity, frequency), nutrition, and sleep/rest or other therapeutic modalities that may prevent the accumulated microtrauma that precedes non-contact ACL injury from sudden mechanical fatigue failure. This review discusses ACL injury epidemiology, current surgical efficacy, the native ACL vascular network, regional ACL histological complexities such as the entheses and crimp patterns, extracellular matrix remodeling, the concept of causal histogenesis, exercise dosage and ligament metabolism, central nervous system reorganization post-ACL rupture, homeostasis regulation, nutrition, sleep and the autonomic nervous system. Based on this information, now may be a good time to re-think primary ACL injury prevention strategies with greater use of modified sport training, improved active recovery that includes well-planned nutrition, and healthy sleep patterns. The scientific rationale behind the efficacy of regenerative orthobiologics and concomitant therapies for primary ACL injury prevention in youth and adolescent athletes are also discussed.

Comprehensive evaluation of magnetic resonance imaging sequences for signal intensity based assessment of anterior cruciate ligament healing following surgical treatment.

Normalized signal intensity (SI) obtained from magnetic resonance imaging (MRI) has been used to track anterior cruciate ligament (ACL) postoperative remodeling. We aimed to assess the effect of MRI sequence (PD: proton density-weighted; T2: T2-weighted; CISS: constructive interference in steady state) on postoperative changes in healing ACLs/grafts. We hypothesized that CISS is better at detecting longitudinal SI and texture changes of the healing ACL/graft compared to the common clinical sequences (PD and T2). MR images of patients who underwent ACL surgery were evaluated and separated into groups based on surgical procedure (Bridge-Enhanced ACL Repair (BEAR; n = 50) versus ACL reconstruction (ACLR; n = 24)). CISS images showed decreasing SI across all timepoints in both the BEAR and ACLR groups (p < 0.01), PD and T2 images showed decreasing SI in the 6-to-12- and 12-to-24-month postoperative timeframes in the BEAR group (p < 0.02), and PD images additionally showed decreasing SI between 6- and 24-months postoperation in the ACLR group (p = 0.02). CISS images showed texture changes in both the BEAR and ACLR groups, showing increases in energy and decreases in entropy in the 6-to-12- and 6-to-24-month postoperative timeframes in the BEAR group (p 0.04), and increases in energy, decreases in entropy, and increases in homogeneity between 6 and 24 months postoperation in the ACLR group (p < 0.04). PD images showed increases in energy and decreases in entropy between 6- and 24-months postoperation in the ACLR group (p < 0.008). Finally, CISS was estimated to require a smaller sample size than PD and T2 to detect SI differences related to postoperative remodeling.

Anterior Cruciate Ligament Reconstruction With Quadriceps Tendon Autograft: Surgical Technique Using Augmentation With a Biocomposite Scaffold

Anterior cruciate ligament (ACL) reconstruction augmentation continues to be widely studied. Both biologic and synthetic augments have been employed to enhance ACL healing and provide early protection. The BioBrace is a biocomposite scaffold that both mechanically reinforces the graft while biologically enhancing graft healing. The purpose of this article is to describe augmentation of an ACL reconstruction with BioBrace.

The infrapatellar fat pad contributes to spontaneous healing after complete anterior cruciate ligament injury.

Anterior cruciate ligament (ACL) injuries have a very low healing capacity but have recently been shown to heal spontaneously with conservative treatment. This study examined the mechanism of spontaneous ACL healing by focusing on the intra-articular tissues of the knee joint. Skeletally mature Wistar rats (n = 70) were randomly assigned to two groups: the controlled abnormal movement (CAM) and anterior cruciate ligament transection (ACLT) groups. The ACL was completely transected at the mid-portion in both groups. Only the CAM group underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice for histological, and molecular biology analyses. The results showed that the behavior of the stump after ACL injury differed between models 12 h after injury. The femoral stump in the ACLT group retreated posteriorly and upwardly. Macrophage polarity analysis revealed that the stump immune response in the CAM group was more activated than that in the ACLT group 6 h after injury. Microarray analysis of the ACL parenchyma and infrapatellar fat pads suggested the involvement of nuclear factor kappa B (NF-κB) signaling. Real-time polymerase chain reaction (PCR) analysis showed that NF-κB gene expression in the infrapatellar fat pad was significantly increased in the CAM group than in the ACLT group. However, there was no difference in the gene expression levels in the ACL parenchyma between models. In conclusion, the healing response of the ACL was activated within 12 h of injury, resulting in differences in the healing response between the models. It has been suggested that infrapatellar fat pads are involved in the healing process and that angiogenesis and antiapoptotic effects through NF-κB signaling may contribute to this mechanism.

Healing of acute anterior cruciate ligament rupture on MRI and outcomes following non-surgical management with the Cross Bracing Protocol

ObjectiveInvestigate MRI evidence of anterior cruciate ligament (ACL) healing, patient-reported outcomes and knee laxity in patients with acute ACL rupture managed non-surgically with the Cross Bracing Protocol (CBP).MethodsEighty consecutive patients...

Predicting anterior cruciate ligament failure load with T2* relaxometry and machine learning as a prospective imaging biomarker for revision surgery

Non-invasive methods to document healing anterior cruciate ligament (ACL) structural properties could potentially identify patients at risk for revision surgery. The objective was to evaluate machine learning models to predict ACL failure load from magnetic resonance images (MRI) and to determine if those predictions were related to revision surgery incidence. It was hypothesized that the optimal model would demonstrate a lower mean absolute error (MAE) than the benchmark linear regression model, and that patients with a lower estimated failure load would have higher revision incidence 2 years post-surgery. Support vector machine, random forest, AdaBoost, XGBoost, and linear regression models were trained using MRI T2* relaxometry and ACL tensile testing data from minipigs (n = 65). The lowest MAE model was used to estimate ACL failure load for surgical patients at 9 months post-surgery (n = 46) and dichotomized into low and high score groups via Youden’s J statistic to compare revision incidence. Significance was set at alpha = 0.05. The random forest model decreased the failure load MAE by 55% (Wilcoxon signed-rank test: p = 0.01) versus the benchmark. The low score group had a higher revision incidence (21% vs. 5%; Chi-square test: p = 0.09). ACL structural property estimates via MRI may provide a biomarker for clinical decision making.

Platelet-Rich Fibrin–Augmented Gap-Bridging Strategy in Rabbit Anterior Cruciate Ligament Repair

Background: We assessed the efficacy of a novel platelet-rich fibrin (PRF)–augmented repair strategy for promoting biological healing of an anterior cruciate ligament (ACL) midsubstance tear in a rabbit model. The biological gap-bridging effect of a PRF scaffold alone or in combination with rabbit ligamentocytes on primary ACL healing was evaluated both in vitro and in vivo. Hypothesis: A PRF matrix can be implanted as a provisional fibrin-platelet bridging scaffold at an ACL defect to facilitate functional healing. Study Design: Controlled laboratory study. Methods: The biological effects of PRF on primary rabbit ligamentocyte proliferation, tenogenic differentiation, migration, and tendon-specific matrix production were investigated for treatment of cells with PRF-conditioned medium (PRFM). Three-dimensional (3D) lyophilized PRF (LPRF)–cell composite was fabricated by culturing ligamentocytes on an LPRF patch for 14 days. Cell-scaffold interactions were investigated under a scanning electron microscope and through histological analysis. An ACL midsubstance tear model was established in 3 rabbit groups: a ruptured ACL was treated with isolated suture repair in group A, whereas the primary repair was augmented with LPRF and LPRF-cell composite to bridge the gap between ruptured ends of ligaments in groups B and C, respectively. Outcomes—gross appearance, magnetic resonance imaging, and histological analysis—were evaluated in postoperative weeks 8 and 12. Results: PRFM promoted cultured ligamentocyte proliferation, migration, and expression of tenogenic genes (type I and III collagen and tenascin). PRF was noted to upregulate cell tenogenic differentiation in terms of matrix production. In the 3D culture, viable cells formed layers at high density on the LPRF scaffold surface, with notable cell ingrowth and abundant collagenous matrix depositions. Moreover, ACL repair tissue and less articular cartilage damage were observed in knee joints in groups B and C, implying the existence of a chondroprotective phenomenon associated with PRF-augmented treatment. Conclusion: Our PRF-augmented strategy can facilitate the formation of stable repair tissue and thus provide gap-bridging in ACL repair. Clinical Relevance: From the translational viewpoint, effective primary repair of the ACL may enable considerable advancement in therapeutic strategy for ACL injuries, particularly allowing for proprioception retention and thus improved physiological joint kinematics.

Evidence of ACL healing on MRI following ACL rupture treated with rehabilitation alone may be associated with better patient-reported outcomes: a secondary analysis from the KANON trial

ObjectivesEvaluate the natural course of anterior cruciate ligament (ACL) healing on MRI within 5 years of acute ACL rupture and compare 2-year and 5-year outcomes based on healing status and...

Healing of a ruptured anterior cruciate ligament and patient-reported outcomes following non-surgical management with a novel bracing protocol

Introduction: A common belief amongst clinicians, researchers and the public is that a ruptured anterior cruciate ligament (ACL) has no healing capacity. This belief has contributed to the high rate of ACL reconstruction, with substantial health costs. We hypothesised that immobilisation in a knee brace at 90-degrees flexion (reducing the distance between the torn ends of the ACL) after acute ACL rupture would facilitate healing. The objective was to investigate MRI evidence of ACL healing, patient-reported outcomes and knee laxity in the first 80 individuals with ACL rupture managed with a novel non-surgical bracing protocol.

In-office needle arthroscopic assessment after primary ACL repair: short-term results in 15 patients

PurposeIn-office needle arthroscopy has been reported as a diagnostic tool for different knee pathologies. In addition, ACL repair has seen a resurgence with the advent of innovative orthopedic devices. The aim of this study was to assess clinical, radiological, and in-office needle arthroscopic findings in 15 adult patients who underwent acute (within 14 days from injury) anterior cruciate ligament (ACL) repair.MethodsFifteen patients voluntarily participated in the study. A second-look arthroscopy was performed with an in-office needle arthroscopy at an average of 7.2 months after the primary repair. The parameters included in the investigation were the continuity of the anatomical footprint of the repaired ACL, subjective assessment of the ACL tension with the probe, and synovial coverage of the ACL. All patients had a Magnetic Resonance Imaging (MRI) at 6 months after repair and an arthrometric evaluation with the KT-1000. Clinical evaluation with the scores, Tegner Lysholm Knee Scoring Scale (TLKSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) was performed at the final follow-up of 2 years. Moreover, a correlation between the characteristics of ACL appearance at the time of the second look in-office needle arthroscopy, MRI and KT-1000 was performed.ResultsThe mean TLKSS was 97.86, the mean KOOS was 98.08 and the mean subjective IKDC was 96.71. The objective IKDC was A in 10 patients and B in 5 patients. ACL healing was graded as A in 11 patients and B in 4 patients. Synovial coverage was graded as good in 10 patients and fair in 5 while MRI assessment showed a type I ACL in 10 patients, type II in 4 patients and type III in 1 patient.ConclusionIn-office needle arthroscopy is a reliable tool to assess the condition of a repaired ACL. In addition, ACL repair performed in acute proximal tears demonstrated excellent clinical results.

Primary Repair for Treating Acute Proximal Anterior Cruciate Ligament Tears: A Histological Analysis and Prospective Clinical Trial.

Reconstruction surgery for acute proximal anterior cruciate ligament (ACL) tears remains controversial. Recently, ACL primary repair has received increasing attention in ACL treatment. This study aimed to explore the histological characteristics of ACL healing in primary repair and compare its therapeutic and prognostic results with the reconstruction of acute proximal ACL tears. Histological experiments using rabbits and a prospective clinical trial were conducted. We established a rabbit model of ACL primary repair, and histological changes were observed using haematoxylin and eosin (HE) and toluidine blue staining. We performed immunohistochemical analysis of CD34 and S-100 and measured the expression of collagen I and II using qRT-PCR, Western blotting, and immunohistochemistry. The prospective clinical trial involved performing ACL primary repair and reconstruction in patients with acute proximal ACL tears to detect proprioception and evaluate the function of joints. We discovered that primary repair promoted cell proliferation in the tendon-bone transition and ligament portions, reduced osteoarthritis-like pathological changes, and maintained blood vessels and proprioceptors within the ACL. In the clinical trial, primary repair achieved similar therapeutic outcomes, including recovery of knee function and proprioception, in the follow-up period as ACL reconstruction. However, the primary repair had a significantly shorter operative time and lower cost than reconstruction. Therefore, doctors should consider the benefit of primary repair in treating acute proximal ACL tears.

SPONTANEOUS HEALING OF THE RUPTURED ANTERIOR CRUCIATE LIGAMENT: OBSERVATIONS FROM THE KANON TRIAL

Purpose: Anterior cruciate ligament (ACL) rupture is a strong risk factor for the development of knee osteoarthritis, irrespective of management with ACL reconstruction (ACLR) or rehabilitation alone. Poor long-term physical and psychological outcomes are common. It is often assumed that a ruptured ACL cannot heal without surgery, despite a paucity of studies investigating the potential for a ruptured ACL to heal. It is not known if ACL healing on MRI is associated with restoration of knee function or favorable outcomes.

The Effects of Three and Six Sessions of Low Energy Extracorporeal Shockwave Therapy on Graft Incorporation and Knee Functions Post Anterior Cruciate Ligament Reconstruction.

Introduction:One session of high energy extracorporeal shockwave therapy (ESWT) was found to improve the healing of anterior cruciate ligament (ACL) after reconstruction in animal and human studies. This study investigated the effects of three and six sessions of low energy ESWT on graft incorporation and knee functions post ACL reconstruction in humans.Materials and methods:Thirty participants with ACL injuries were recruited and assigned equally into three groups with 10 participants per group (n=10). Participants in the control group received physiotherapy alone without low energy ESWT. Participants in the 3ESWT group underwent three sessions of low energy ESWT (one session per week) combined with physiotherapy, and participants in the 6ESWT group received six sessions of low energy ESWT (one session per week) combined with physiotherapy. However, five participants were lost to follow-up. Evaluations of graft incorporation of the tibial tunnel using magnetic resonance (MRI) and Lysholm score were carried out before ACL reconstruction and after six months post ACL reconstruction.Results:The number of grafts with partial incorporation in the tibia tunnel in 6ESWT was significantly higher compared with the number of grafts with non-incorporation at six months post-operatively, X2 (1, N=9) =5.44, p =0.02. However, there was no significant difference between frequencies of graft incorporation in tibia tunnel in the control and 3ESWT groups, X2 (1, N=7) =3.57, p =0.06 and X2 (1, N=9) =2.78, p =0.10, respectively at 6 months postoperatively. Lysholm scores were significantly higher at 6 months post ACL reconstruction compared to the baseline value for each group (p<0.002, respectively). However, there was no significant difference in the Lysholm score between each group (F = 2.798, p = 0.083).Conclusions:Six sessions of low energy ESWT improved graft incorporation in the tibial tunnel. Both three and six sessions of low energy of ESWT does not affect the knee function score at six months post ACL reconstruction.

Occurrence of inadequate ACL healing after Dynamic Intraligamentary Stabilization and functional outcome—a multicentre case series

IntroductionDynamic Intraligamentary Stabilization (DIS) is a technique for preservation, anatomical repair and stabilization of a freshly injured anterior cruciate ligament (ACL). The main purpose of this study was to evaluate the short-term re-operation rate when compared to traditional autograft reconstruction.MethodsFour, from the developer independent, centres enrolled patients that underwent ACL repair by DIS, according to the specific indications given by MRI imaging at a minimum follow-up of 12 months. The re-operation rate was recorded as primary outcome. Secondary outcome measures were the postoperative antero-posterior knee laxity (using a portable Rolimeter®), as well as the Tegner, Lysholm and IKDC Scores.ResultsA total of 105 patients were investigated with a median follow-up of 21 months. Thirteen patients were lost to follow-up. Of the remaining 92 patients 15 (16.3%) had insufficient functional stability and required subsequent ACL reconstruction. These patients were excluded from further analysis, leaving 77 consecutive patients for a 12 months follow-up. The median age at time of surgery was 30 years for that group. At time of follow-up a median antero-posterior translation difference of 2 mm was measured. None of these patients reported subjective insufficiency (giving way), but in 14 patients (18.2%), the difference of antero-posterior translation was more than 3 mm. We found a median Tegner Score of 5.5, a median Lysholm Score of 95.0 and a median IKDC Score of 89.4.ConclusionThe main finding of this multicentre study is a relevant re-operation rate of 16.3%. Another 18.2% showed objective antero-posterior laxity (≥ 3 mm) during testing raising the suspicion of postoperative non-healing. The failure rate of DIS in this study is higher than for reconstruction with an autologous tendon graft. However, our successfully treated patients had a good clinical and functional outcome based on antero-posterior knee laxity and clinical scores, comparable to patients treated by autograft reconstruction.

Arthroscopic anterior cruciate ligament repair with and without suture augmentation: technical note

Anterior cruciate ligament (ACL) tears are routinely treated with an ACL reconstruction. This is based on historical literature reporting high failure rates after ACL repairs in addition to the limited healing potential of the ACL. Recently, improved understanding of pathophysiology of ligamentous healing has led to increasing interest in treating proximal avulsions with excellent tissue quality in the acute setting, as this technique allows for ACL healing. Potential advantages of ACL repair include preservation of native proprioceptive and kinematics of the knee, avoidance of graft harvesting morbidity and the possibility to perform a primary ACL reconstruction in case of failure. As a consequence, several techniques for ACL repair have been proposed that can be performed in isolation or with suture augmentation. The primary aim of this technical note is to describe step-by-step the ACL repair technique with and without suture augmentation. The secondary aim of the current study is to review the indications, patient selection and advantages of the technique.

Biologic agents to optimize outcomes following ACL repair and reconstruction: A systematic review of clinical evidence.

Treatment options for anterior cruciate ligament (ACL) injuries have greatlydeveloped over the past decades. Althoughreconstruction surgery is a concretereality, stimulation of ACL healing through biological techniques could represent a revolutionary conservative approach. The use of biologic products, such as platelet-rich plasma (PRP) or mesenchymal stem cells (MSCs), to treat partial ruptures or to enhance ligamentization after reconstruction, could thoroughly improve clinical outcomes. The aim of the present paper is to systematically review the available literature onthis topic, to (i) describe the current state of the art in available biologic techniques; (ii) clarify the outcomes of their application; (iii) identify areas needing further investigation and possible future development. A systematic review of the literature on the use of biologically active agents (PRP and MSCs) to enhance outcomes of ACL surgery was performed: 31 studies were included. Based on the ACL injury pattern, 6 papers investigated biologic agents in ACL partial tears whereas 25 papers in ACL reconstruction. Sixteenof twenty-five studies dealing with ACL reconstruction were randomized controlled trials, whereas only case series are available for partial ACL tears. Current evidence is still lacking sound data to support the use of biological agents: no clinical superiority has been described when using PRP in ACL reconstruction. Concerning ACL healing in partial tears, the application of PRP has led to encouraging outcomes, but these findings should be confirmed by appropriately designed RCTs.

Influence of the site of injury on the spontaneous healing response in a rat model of total rupture of the anterior cruciate ligament

ABSTRACT Aim The healing ability of the anterior cruciate ligament (ACL) injury is very poor; however, it has recently been shown to undergo self-healing with conservative treatments. In this study, we evaluated the influence of the site of injury on the healing process after complete transverse tear of ACL using a rat model. Materials and Methods A total of 58 skeletally mature Wistar rats were randomly assigned to various ACL injury groups: controlled abnormal movement-mid-portion (CAM-MP), controlled abnormal movement-femoral side (CAM-FS), ACL transection-mid-portion (ACLT-MP), or ACL transection-femoral side (ACLT-FS) injury groups. The ACL was completely transected in the mid-portion in the ACLT-MP and CAM-MP groups, and on the femoral side in the ACLT-FS and CAM-FS groups. Both CAM groups underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice postoperatively for histological and biomechanical assessment. Results Significant differences were found in the ratios of residual ligament lengths between the CAM-MP and CAM-FS groups, demonstrating the validity of each model. Spontaneous healing of the injured ACL was observed in the CAM-MP and CAM-FS groups but not in the ACLT-MP and ACLT-FS groups. The mechanical strength of the healing ACL did not differ between the CAM-MP and CAM-FS groups 8 weeks after injury; however, the former had better mechanical strength than the latter 12 weeks after the injury. Conclusion ACL injuries in the mid-portion and on the femoral side may be treated with conservative therapy for spontaneous healing.

ACL Repair: A Game Changer or Will History Repeat Itself? A Critical Appraisal.

Until the past decade the common thought was that the anterior cruciate ligament (ACL) was not able to heal and restore knee stability. In this manuscript a brief review of studies of the developers and the early adaptors of four different modern ACL repair techniques are presented. The present status and considerations for the future of ACL repair and its research are shared. After promising short- to midterm ACL healing results by the developers, the results of the early adaptors show more variety in terms of rerupture and reintervention for other reasons. Risk factors for failure are a young age, high preinjury sports activity level, midsubstance ruptures and impaired integrity of the ACL bundles and the synovial sheath. There is a call for more clinical data and randomized clinical trials. Conclusion: an important finding of the past decade is that the ACL is able to heal and subsequently restabilize the knee. Patient selection is emphasized: the ideal patient is a non-high athlete older than 25 and has an acute proximal one bundle ACL rupture. Further research will have to show if ACL repair could be a game changer or if history will repeat itself.