Biology of anterior cruciate ligament injury and repair: Kappa delta ann doner vaughn award paper 2013

Biologic Impact of Anterior Cruciate Ligament Injury and Reconstruction

Surgical intervention after anterior cruciate ligament (ACL) tears is typically required because of the limited healing capacity of the ACL. However, mechanical factors and the inflammatory response triggered by the injury and surgery can impact patient outcomes. This review explores key aspects of ACL injury and reconstruction biology, including the inflammatory response, limited spontaneous healing, secondary inflammation after reconstruction, and graft healing processes. Understanding these biologic mechanisms is crucial for developing new treatment strategies and enhancing patient well-being. By shedding light on these aspects, clinicians and researchers can work toward improving quality of life for individuals affected by ACL tears.

How Research Improves Clinical Care: The Case for Orthopaedic Surgeon Research Leadership and Collaboration: AOA Critical Issues Symposium

ABSTRACT

Improving the performance and impact of orthopaedic research is a critical leadership challenge. Musculoskeletal (MSK) conditions are a leading cause of disability worldwide, for which research investment and performance lags far behind the burden of disease. In the United States, MSK disorders account for the highest health care costs, have increased in incidence at the fastest rate, and exceed the combined costs of cardiovascular diseases and neoplasms. Despite the cost to society, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), with primary responsibility for MSK research, receives <1.4% of the funds allocated to the National Institutes of Health (NIH). Although orthopaedic surgeons are leading providers of MSK clinical care, the dearth of orthopaedic clinician-scientists also greatly reduces representation of MSK scientific and clinical expertise among academic and scientific leaders. The goals of this symposium were to highlight the critical need for greater prioritization and investment in orthopaedic research and to engage orthopaedic leaders in addressing these needs. Compelling stories of research success from 3 orthopaedic chairs were featured to highlight how orthopaedic surgeon leadership in bench-to-bedside research substantially advances MSK clinical care. Seminar participants also emphasized the need to improve evidence-based clinical practice for which multicenter prospective cohort and registry studies represent opportunities for broader involvement. Prioritization of orthopaedic clinician-scientist development and formation of multidisciplinary partnerships with basic and translational scientists were emphasized as critical needs to advance MSK health. It is critical for orthopaedic chairs to "be invested in" and to "invest in" the success of orthopaedic research. This investment includes developing a professional climate that values research achievement and collaboration as well as implementing strategies to support and sustain research success. Finally, orthopaedic leaders need to advocate for federal research funding to be proportional to the economic burden of disease for which MSK conditions carry the highest current and projected costs. With health-care costs accounting for nearly one-fifth of the U.S. economy, increasing the investment in orthopaedic research to reduce the prevalence, disability, and morbidity from MSK disease needs to be a top orthopaedic and national leadership priority.

Do the Differences in the Epiligament of the Proximal and Distal Parts of the Anterior Cruciate Ligament Explain Their Different Healing Capacities? Quantitative and Immunohistochemical Analysis of CD34 and α-SMA Expression in Relation to the Epiligament Theory

The aim of this study was to assess the epiligament theory by determining the normal epiligament morphology of the proximal and distal parts of the anterior cruciate ligament in humans and analyzing the differences between them and the midportion of the ligament in terms of cell numbers and expression of CD34 and α-SMA. Samples were obtained from the anterior cruciate ligaments of 12 fresh knee joints. Monoclonal antibodies against CD34 and α-SMA were used for immunohistochemistry. Photomicrographs were analyzed using ImageJ software, version 1.53f. The cell density was higher in the epiligament than in the ligament connective tissue. Cell counts were higher in the proximal and distal thirds than in the midsubstance of the epiligament. CD34 was expressed similarly in the proximal and distal thirds, although it seemed slightly more pronounced in the distal third. α-SMA expression was more robust in the proximal than the distal part. The results revealed that CD34 and α-SMA are expressed in the human epiligament. The differences between the numbers of cells in the proximal and distal parts of the epiligament and the expression of CD34 and α-SMA enhance epiligament theory. Future investigations into improving the quality of ligament healing should not overlook the epiligament theory.

Comparison of Clinical Outcomes Between Modern Augmented ACL Repair and Autograft ACL Reconstruction: A Systematic Review and Meta-analysis of Studies With Minimum 2-Year Follow-up

Background

Anterior cruciate ligament (ACL) reconstruction has been the gold standard for primary ACL rupture since the 1990s. In the past decade, ACL repair has received renewed attention and increased research.

Purpose

To compare the clinical outcomes of modern augmented ACL repair versus autograft reconstruction for ACL ruptures.

Study Design

Systematic review; Level of evidence, 3.

Methods

A search of the PubMed, EMBASE, Scopus, Web of Science, and the Cochrane Library databases was conducted for prospective or retrospective comparative studies published between January 1, 2010, and January 3, 2023, with a minimum 2-year follow-up. Two independent reviewers performed data extraction and methodological quality assessment. Sensitivity analysis was performed to maintain the stability of results.

Results

Nine studies were included (minimum follow-up period, 24-60 months). The total sample size was 833 patients (augmented repair group: 358 patients; autograft ACL reconstruction group: 475 patients). There were 4 randomized controlled trials (level 1), 1 prospective comparative study (level 2), 2 retrospective comparative studies (level 3), and 2 case-control studies (level 3). The augmented ACL repair group attained significantly higher Lysholm score (weighted mean difference [WMD] = 1.57; 95% confidence interval [CI], 0.14-3.01; P = .03) and hamstring strength (WMD = 36.69; 95% CI, 29.07-44.31; P < .01) but had higher rates of hardware removal (odds ratio [OR] = 6.30; 95% CI, 2.44-16.23; P = .0001), reoperation (OR = 1.87; 95% CI, 1.33-2.62; P = .0003), and failure (OR = 1.58; 95% CI, 1.03-2.43; P = .0003) compared with the autograft ACL reconstruction group. No significant differences were observed between the repair and reconstruction groups regarding postoperative International Knee Documentation Committee scores, Tegner scores, knee laxity, satisfaction, ACL revisions, complications, and reoperation rather than revision.

Conclusion

Augmented ACL repair was associated with higher rates of reoperation, hardware removal, and failure compared with autograft ACL reconstruction in studies with minimum 2-year follow-up data. However, augmented ACL repair had higher Lysholm scores and hamstring strength versus autograft ACL reconstruction.

Is remnant preservation in anterior cruciate ligament reconstruction superior to the standard technique? An overview of systematic reviews

BACKGROUND

Anterior cruciate ligament injury is a common knee joint injury. Anterior cruciate ligament reconstruction is a common surgical treatment to treat anterior cruciate ligament injury. It may have certain advantages to retain the ligament stump during the operation, but the results of systematic evaluation on whether to retain the ligament stump are different. The conclusion is still controversial, and the quality needs to be strictly evaluated.

OBJECTIVE

To evaluate the methodological quality, risk of bias, reporting quality and evidence quality of the systematic review of remnant preservation in anterior cruciate ligament reconstruction, and to provide reference for clinical work.

METHODS

We systematically searched the system evaluations in 8 electronic databases, the languages were limited to Chinese and English, and the time limit was from the establishment of the database to June 2023. Two reviewers independently screened literature and extracted data. The methodological quality, risk of bias, reporting quality and quality of evidence were evaluated by AMSTAR-2, ROBIS, PRISMA and GRADE tools.

RESULTS

A total of 14 systematic reviews were included. The evaluation of results showed that the methodological quality of the included systematic reviews was relatively low, of which 5 were low quality and 9 were critically low quality. A small number of systematic reviews were low risk of bias. The system evaluation reports are relatively complete, but the lack of program registration is a common problem. A total of 111 pieces of clinical evidence were extracted from the included 14 systematic reviews. The quality of evidence was generally low, with only 7 pieces of high-quality evidence, 45 pieces of medium-quality evidence, and the rest were low and very low-quality evidence. Among the reasons for relegation, imprecision is the most common, followed by inconsistency and indirectness. The existing evidence shows that patients after anterior cruciate ligament reconstruction with remnant preservation have certain advantages in knee joint function, joint stability and proprioception recovery, which may be a more effective surgical method. However, it may also increase the incidence of postoperative complications and adverse reactions.

CONCLUSION

Compared with Standard Technique, Remnant Preservation in Anterior Cruciate Ligament Reconstruction has more advantages in restoring joint function and stability and proprioception. But the potential risks should also be considered by surgeons. At present, the quality of evidence is generally low, and the reliability of the conclusion is insufficient. It still needs to be verified and further in-depth research is needed.

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.

Revisiting the role of hyperbaric oxygen therapy in knee injuries: Potential benefits and mechanisms

Knee injury negatively impacts routine activities and quality of life of millions of people every year. Disruption of tendons, ligaments, and articular cartilage are major causes of knee lesions, leading to social and economic losses. Besides the attempts for an optimal recovery of knee function after surgery, the joint healing process is not always adequate given the nature of intra-articular environment. Based on that, different therapeutic methods attempt to improve healing capacity. Hyperbaric oxygen therapy (HBOT) is an innovative biophysical approach that can be used as an adjuvant treatment post-knee surgery, to potentially prevent chronic disorders that commonly follows knee injuries. Given the well-recognized role of HBOT in improving wound healing, further research is necessary to clarify the benefits of HBOT in damaged musculoskeletal tissues, especially knee disorders. Here, we review important mechanisms of action for HBOT-induced healing including the induction of angiogenesis, modulation of inflammation and extracellular matrix components, and activation of parenchyma cells-key events to restore knee function after injury. This review discusses the basic science of the healing process in knee injuries, the role of oxygen during cicatrization, and shed light on the promising actions of HBOT in treating knee disorders, such as tendon, ligament, and cartilage injuries.

Advanced Gene Therapy Strategies for the Repair of ACL Injuries

The anterior cruciate ligament (ACL), the principal ligament for stabilization of the knee, is highly predisposed to injury in the human population. As a result of its poor intrinsic healing capacities, surgical intervention is generally necessary to repair ACL lesions, yet the outcomes are never fully satisfactory in terms of long-lasting, complete, and safe repair. Gene therapy, based on the transfer of therapeutic genetic sequences via a gene vector, is a potent tool to durably and adeptly enhance the processes of ACL repair and has been reported for its workability in various experimental models relevant to ACL injuries in vitro, in situ, and in vivo. As critical hurdles to the effective and safe translation of gene therapy for clinical applications still remain, including physiological barriers and host immune responses, biomaterial-guided gene therapy inspired by drug delivery systems has been further developed to protect and improve the classical procedures of gene transfer in the future treatment of ACL injuries in patients, as critically presented here.

Effects of remnant preservation in anterior cruciate ligament reconstruction: A systematic review and meta-analysis

Background

Compared with standard anterior cruciate ligament (ACL) reconstruction, it is controversial whether anterior cruciate ligament reconstruction (ACLR) with remnant preservation can lead to better clinical outcomes. We conducted a systematic study and meta-analysis to assess the differences in clinical efficacy between the two.

Method

We searched for clinical randomized controlled studies and cohort studies included in the Cochrane library, PubMed, and Embase from March 2012 to March 2022 in English. The included studies were ACLR with or without remant preservation, and the data were extracted and the quality of the included studies was assessed by two authors, respectively. Revman 5.4 was used for statistical analysis and conclusions were presented.

Result

Ten articles containing a total of 777 patients were finally included. There was no significant difference in postoperative Lachman test [OR = 1.66, 95%CI (0.79, 3.49), P = 0.18 > 0.05], Tegner score [SMD = −0.13, 95%CI (−0.47, 0.22), P = 0.46 > 0.05], synovial coverage rate by second-look arthroscopy [OR = 1.55, 95%CI (0.66, 3.65), P = 0.32 > 0.05], the rate of cyclops lesion [OR = 3.92, 95%CI (0.53, 29.29), P = 0.18 > 0.05], joint range of motion [SMD = 0.27, 95%CI (−0.13, 0.68), P = 0.19 > 0.05] and re-injury rate [OR = 0.57, 95%CI (0.18, 1.74), P = 0.32 > 0.05] between the two groups. There were statistically significant differences in postoperative Lysholm score [SMD = 0.98, 95% CI (0.32, 1.64), P = 0.004 < 0.05], International Knee Documantation Committee grade (IKDC grade) [OR = 2.19, 95%CI (1.03, 4.65), P = 0.04 < 0.05], Pivot shift test [OR = 1.71, 95%CI (1.06, 2.77), P = 0.03 < 0.05], KT1000/2000 arthrometer side-to-side difference [SMD = −0.22, 95%CI (−0.42, −0.03), P = 0.02 < 0.05], operation time [SMD = 11.69, 95%CI (8.85, 14.54), P = 0.00001 < 0.05] and degree of tibial tunnel enlargement [SMD = −0.66, 95%CI (−1.08, −0.23), P = 0.002 < 0.05].

Conclusion

This meta-analysis concluded that remnant preservation significantly had better results in terms of patient functional score (Lysholm, IKDC), knee stability (Pivot shift test, postoperative side-to-side anterior laxity) and tibial tunnel enlargement. In terms of complications (incidence of Cyclops lesions, range of motion, re-injury rate), no significant differences were seen between the two groups. Although many studies concluded that remnant preservation could bring better synovial coverage, this meta-analysis indicated that there is insufficient evidence to support it, possibly due to different remnant preservation procedures.The potential risks associated with longer operation times are also worth considering.

Cellular Augmentation of Anterior Cruciate Ligament Surgery Is Not Currently Evidence Based: A Systematic Review of Clinical Studies

PURPOSE

To perform a systematic review of clinical outcome studies exploring cellular augmentation of anterior cruciate ligament (ACL) surgery, including stem cell techniques.

METHODS

A systematic search was performed according to the Preferred Reporting Items of Systematic Reviews and Meta-analyses (PRISMA) guidelines using the Cochrane, PubMed, MEDLINE, SPORTDiscus, and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases from 2000 to 2019. The inclusion criteria were clinical studies that reported on ACL surgery augmented with stem cells or cellular therapy and patient-reported outcome measures or graft healing. Risk of bias was assessed using the Cochrane risk-of-bias tool for randomized clinical trials, and nonrandomized trials were assessed using the Methodological Items for Non-randomized Studies (MINORS) tool. Methodologic assessment was performed according to the Modified Coleman Methodology Score.

RESULTS

Four studies were found: 2 randomized clinical trials, 1 cohort study with a matched historical control group, and 1 case series. The mean Modified Coleman Methodology Score in these studies was 59, and there was a low risk of bias in 1 study. One study reported outcomes of augmented ACL repair, and 3 studies reported the results of augmented ACL reconstruction. Cellular therapies varied and included concentrated bone marrow aspirate, collagenase/centrifuge processed adipose, and marrow stimulation combined with platelet-rich plasma, as well as cells cultured from allograft bone marrow aspirate. The concentrated bone marrow aspirate and adipose tissue study results did not support their use. The marrow stimulation technique combined with repair led to promising clinical results. The use of allograft cultured cells improved patient-reported outcomes and postoperative radiographic findings.

CONCLUSIONS

Augmentation of ACL surgery with cellular therapy is not supported by clinical evidence at this time.

LEVEL OF EVIDENCE

Level IV.

Efficacy of repair for ACL injury: a meta‑analysis of randomized controlled trials

We aim to compare the curative effect of primary repair for anterior cruciate ligament (ACL) injury with reconstruction and provide the reliable evidence for its clinical application. The literatures were searched in PubMed, EMBASE, Springer, and other medical literature databases published between January 1970 and June 2021. Basic characteristics, surgery technique, clinical outcome scores and physical examination results were recorded and evaluated. Seven randomized controlled trials (RCT) were eligible for inclusion. The results showed that there were no statistically significant differences between arthroscopic ACL repair and ACL reconstruction for Tegner, Lysholm, Lachman, KT-1000, range of motion (ROM), functional outcomes and reoperation rate (P > 0.05), even the result of IKDC scores showed that arthroscopic repair was better than reconstruction (P = 0.04). However, through the subgroup analysis, it was found that the short-term follow-up results of arthroscopic ACL repair were indeed better than those of open ACL repair. Therefore, we can assume that the arthroscopic ACL repair technique is an optional and promising surgical method to treat ACL injury.

Design Features and Rationale of the BEAR-MOON (Bridge-Enhanced ACL Restoration Multicenter Orthopaedic Outcomes Network) Randomized Clinical Trial

Background:

BEAR (bridge-enhanced anterior cruciate ligament [ACL] restoration), a paradigm-shifting technology to heal midsubstance ACL tears, has been demonstrated to be effective in a single-center 2:1 randomized controlled trial (RCT) versus hamstring ACL reconstruction. Widespread dissemination of BEAR into clinical practice should also be informed by a multicenter RCT to demonstrate exportability and compare efficacy with bone--patellar tendon–bone (BPTB) ACL reconstruction, another clinically standard treatment.

Purpose:

To present the design and initial preparation of a multicenter RCT of BEAR versus BPTB ACL reconstruction (the BEAR: Multicenter Orthopaedic Outcomes Network [BEAR-MOON] trial). Design and analytic issues in planning the complex BEAR-MOON trial, involving the US National Institute of Arthritis and Musculoskeletal and Skin Diseases, the US Food and Drug Administration, the BEAR implant manufacturer, a data and safety monitoring board, and institutional review boards, can usefully inform both clinicians on the trial’s strengths and limitations and future investigators on planning of complex orthopaedic studies.

Study Design:

Clinical trial.

Methods:

We describe the distinctive clinical, methodological, and operational challenges of comparing the innovative BEAR procedure with the well-established BPTB operation, and we outline the clinical motivation, experimental setting, study design, surgical challenges, rehabilitation, outcome measures, and planned analysis of the BEAR-MOON trial.

Results:

BEAR-MOON is a 6-center, 12-surgeon, 200-patient randomized, partially blinded, noninferiority RCT comparing BEAR with BPTB ACL reconstruction for treating first-time midsubstance ACL tears. Noninferiority of BEAR relative to BPTB will be claimed if the total score on the International Knee Documentation Committee (IKDC) subjective knee evaluation form and the knee arthrometer 30-lb (13.61-kg) side-to-side laxity difference are both within respective margins of 16 points for the IKDC and 2.5 mm for knee laxity.

Conclusion:

Major issues include patient selection, need for intraoperative randomization and treatment-specific postoperative physical therapy regimens (because of fundamental differences in surgical technique, initial stability construct, and healing), and choice of noninferiority margins for short-term efficacy outcomes of a novel intervention with evident short-term advantages and theoretical, but unverified, long-term benefits on other dimensions.

Current trends in the anterior cruciate ligament part 1: biology and biomechanics

A trend within the orthopedic community is rejection of the belief that "one size fits all." Freddie Fu, among others, strived to individualize the treatment of anterior cruciate ligament (ACL) injuries based on the patient's anatomy. Further, during the last two decades, greater emphasis has been placed on improving the outcomes of ACL reconstruction (ACL-R). Accordingly, anatomic tunnel placement is paramount in preventing graft impingement and restoring knee kinematics. Additionally, identification and management of concomitant knee injuries help to re-establish knee kinematics and prevent lower outcomes and registry studies continue to determine which graft yields the best outcomes. The utilization of registry studies has provided several large-scale epidemiologic studies that have bolstered outcomes data, such as avoiding allografts in pediatric populations and incorporating extra-articular stabilizing procedures in younger athletes to prevent re-rupture. In describing the anatomic and biomechanical understanding of the ACL and the resulting improvements in terms of surgical reconstruction, the purpose of this article is to illustrate how basic science advancements have directly led to improvements in clinical outcomes for ACL-injured patients.Level of evidenceV.

Rehabilitation Principles to Consider for Anterior Cruciate Ligament Repair

CONTEXT

Injury to the anterior cruciate ligament (ACL) is among the most common orthopaedic injuries, and reconstruction of a ruptured ACL is a common orthopaedic procedure. In general, surgical intervention is necessary to restore stability to the injured knee, and to prevent meniscal damage. Along with surgery, intense postoperative physical therapy is needed to restore function to the injured extremity. ACL reconstruction (ACLR) has been the standard of care in recent decades, and advances in surgical technology have reintroduced the prospect of augmented primary repair of the native ACL via a variety of methods.

EVIDENCE ACQUISITION

A search of PubMed database of articles and reviews available in English was performed through 2020. The search terms ACLR, anterior cruciate ligament repair, bridge enhanced acl repair, suture anchor repair, dynamic intraligamentary stabilization, internal bracing, suture ligament augmentation, and internal brace ligament augmentation were used.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

No exact consensus exists on effective rehabilitation protocols after ACL repair techniques, as the variation in published protocols seem even greater than the variation in those for ACLR. For some techniques such as internal bracing and dynamic interligamentary stabilization, it is likely permissible for the patients to progress to full weightbearing and discontinue bracing sooner. However, caution should be applied with regard to earlier return to sport than after ACLR as to minimize risk for retear.

CONCLUSION

More research is needed to address how physical therapies must adapt to these innovative repair techniques. Until that is accomplished, we recommend that physical therapists understand the differences among the various ACL surgery techniques discussed here and work with the surgeons to develop a rehabilitation protocol for their mutual patients.

STRENGTH OF RECOMMENDATION TAXONOMY (SORT)

C.

Diffusion tensor imaging of the anterior cruciate ligament following primary repair with internal bracing: A longitudinal study

Diffusion tensor imaging (DTI) provides information about tissue microstructure and its degree of organization by quantifying water diffusion. We aimed to monitor longitudinal changes in DTI parameters (fractional isotropy, FA; mean diffusivity, MD; axial diffusivity, AD; radial diffusivity, RD) of the anterior cruciate ligament (ACL) following primary repair with internal bracing (IBLA). Fourteen patients undergoing IBLA were enrolled prospectively and scheduled for clinical follow-up, including instrumented laxity testing, and DTI at 3, 6, 12, and 24 months postoperatively. DTI was also performed in seven healthy subjects. Fiber tractography was used for 3D segmentation of the whole ACL volume, from which median DTI parameters were calculated. The posterior cruciate ligament (PCL) served as a control. Longitudinal DTI changes were assessed using a linear mixed model, and repeated measures correlations were calculated between DTI parameters and clinical laxity tests. At follow-up, thirteen patients had a stable knee and one patient sustained an ACL rerupture after 12 months postoperatively. The ACL repair showed a significant decrease of FA within the first 12 months after surgery, followed by stable FA values thereafter, while ACL diffusivities decreased over time returning towards normal values at 24 months postoperatively. For PCL there were no significant DTI changes over time. There was a significant correlation between ACL FA and laxity tests (r = -0.42, P = .017). This study has shown the potential of DTI to longitudinally monitor diffusion changes in the ACL following IBLA. The DTI findings suggest that healing of the ACL repair is incomplete at 24 months postoperatively.

Fibrous Systems as Potential Solutions for Tendon and Ligament Repair, Healing, and Regeneration

Tendon and ligament injuries caused by trauma and degenerative diseases are frequent and affect diverse groups of the population. Such injuries reduce musculoskeletal performance, limit joint mobility, and lower people's comfort. Currently, various treatment strategies and surgical procedures are used to heal, repair, and restore the native tissue function. However, these strategies are inadequate and, in some cases, fail to re-establish the lost functionality. Tissue engineering and regenerative medicine approaches aim to overcome these disadvantages by stimulating the regeneration and formation of neotissues. Design and fabrication of artificial scaffolds with tailored mechanical properties are crucial for restoring the mechanical function of tendons. In this review, the tendon and ligament structure, their physiology, and performance are presented. On the other hand, the requirements are focused for the development of an effective reconstruction device. The most common fiber-based scaffolding systems are also described for tendon and ligament tissue regeneration like strand fibers, woven, knitted, braided, and braid-twisted fibrous structures, as well as electrospun and wet-spun constructs, discussing critically the advantages and limitations of their utilization. Finally, the potential of multilayered systems as the most effective candidates for tendon and ligaments tissue engineering is pointed out.

Patellar Bone-Tendon-Bone Autografts versus Quadriceps Tendon Allograft with Synthetic Augmentation in a Canine Model

Patellar bone-tendon-bone (pBTB) autografts are often considered the "gold standard" for complete anterior cruciate ligament (ACL) reconstruction and are also associated with significant complications and early-onset knee osteoarthritis (OA). A novel quadriceps tendon allograft with synthetic augmentation, or "internal brace" (QTIB), has been reported to have potential advantages for ACL reconstruction based on animal model data. In this preclinical canine comparison study, we hypothesized that QTIB allograft compared with pBTB autograft would provide superior durability for knee stability, function, and prevention of OA. Under approval from our Institutional Animal Care and Use Committee, adult purpose-bred research hounds (n = 10) underwent arthroscopic complete transection of the ACL followed by either an arthroscopic-assisted all-inside ACL reconstruction using the QTIB allograft (n = 5) or pBTB autograft (n = 5). Contralateral knees were used as nonoperated controls (n = 10). Radiographic and arthroscopic assessments were performed at 2 and 6 months, respectively, after surgery. Anterior drawer, internal rotation, lameness, kinetics, pain, effusion, and comfortable range of knee motion were measured at 2, 3, and 6 months. Biomechanical and histologic assessments were performed at 6 months. All reconstructed knees were stable and had intact ACL grafts 6 months after surgery. At 6 months, QTIB reconstructed knees had significantly less lameness, lower pain, less effusion, and increased range of motion when compared with BTB knees (p < 0.05). BTB knees had significantly higher radiographic OA scores than QTIB knees at 6 months (p < 0.05). Superior outcomes associated with QTIB allograft may be due to the lack of donor site morbidity, the use of a robust tendon graft, and/or protection of the graft from the synthetic augmentation. Robust tendon grafts combined with a synthetic internal brace and platelet-rich plasma (PRP) may allow for more rapid and robust tendon-bone healing and graft "ligamentization," which protects the graft from early failure and rapid OA development that can plague commonly-used allografts.

Efficacy of Nonaugmented, Static Augmented, and Dynamic Augmented Suture Repair of the Ruptured Anterior Cruciate Ligament: A Systematic Review of the Literature

BACKGROUND

Anterior cruciate ligament suture repair (ACLSR) was abandoned late last century in favor of anterior cruciate ligament (ACL) reconstruction (ACLR) because of overall disappointing results. However, in recent years there has been renewed and increasing interest in ACLSR for treatment of ACL ruptures. Several contemporary ACLSR techniques are being used, but any difference in effectiveness is unclear.

HYPOTHESIS

Contemporary nonaugmented (NA), static augmented (SA), and dynamic augmented (DA) ACLSR leads to (1) comparable outcomes overall and (2) comparable outcomes between proximal third, middle third, and combined ACL rupture locations (a) within and (b) between ACLSR technique categories.

STUDY DESIGN

Systematic review.

METHODS

An electronic search was performed in the MEDLINE and Embase databases for the period between January 1, 2010, and August 7, 2019. All articles describing clinical and patient-reported outcomes for ACLSR were identified and included, and outcomes for NA, SA, and DA ACLSR categories were compared.

RESULTS

A total of 31 articles and 2422 patients were included. The majority of articles (65%) and patients (89%) reported outcomes of DA ACLSR. Overall, there was high heterogeneity in study characteristics and level as well as quality of evidence (19 level 4; 7 level 3; 3 level 2; and 2 level 1). Most studies indicated excellent patient-reported outcomes. Overall, the variability in (and the maximum of) the reported failure rate was high within all ACLSR categories. The variability in (and the maximum of) the reported rate of all other complications was highest for DA ACLSR. Regarding ACL rupture location, the failure rate was highest in proximal ACL ruptures within the SA and DA ACLSR categories; rates of all other reported complications were highest in combined ACL ruptures within the DA ACLSR category. However, no studies in the NA category and only 1 study in the SA ACLSR category evaluated combined ACL ruptures. The majority of studies comparing ACLSR and ACLR found no differences in outcomes.

CONCLUSION

The amount of high-quality evidence for contemporary ACLSR is poor. This makes it difficult to interpret differences among ACLSR categories and among ACL rupture locations and, though promising, to establish the role of ACLSR in the treatment of ACL ruptures. More high-quality large randomized clinical trials with longer follow-up comparing ACLSR and ACLR are needed.

The effect of thermosensitive hydrogel platelet-rich-plasma complex in the treatment of partial tear of anterior cruciate ligament in rat model

Background/Objective

The treatment of anterior cruciate ligament (ACL) partial tear is controversial. The reconstructive surgery is invasive while the prevalence of subsequent insufficiency after conservative treatment has been reported to range from 11% to 62%. Therefore, a new method that promotes tissue regeneration is needed. The aim of this study was to observe the healing of ACL partial tear biomechanically and histologically after the administration of a thermosensitive hydrogel platelet-rich-plasma (PRP) complex.

Methods

The complex was prepared according to a previously published protocol. One hundred and fifty 12-week-old male Sprague-Dawley rats were included and they were allocated into 4 groups. Lesion control group (Group 1), treatment group (Group 2), gel-only group (Group 3) and intact group (Group 4). Biomechanical testing, histological analysis (H&E and immunohistochemical staining) and scoring was performed.

Results

On gross observation, the treatment group showed a continuous ACL with slightly thickened synovium or a partially healed ACL at 6-week follow up. In the biomechanical testing at 6 weeks after surgery, the failure load of the treatment group was significantly superior when compared with the lesion control group (52.7±10.8N vs. 41.6±7.8N, p<0.01), but the failure load was not restored to level of the intact group (52.7±10.8N vs. 61.5±9.1N, p=0.037). The maturity index of wound sites showed no significant inter-group differences at any timepoints. However, an increased expression of vascular endothelial growth factor (VEGF) and pro-collagen I was detected.

Conclusion

The thermosensitive hydrogel-PRP was shown to be effective in enhancing the healing of ACL partial tear in the rat model, and potentially this complex can be used as a treatment for patients with ACL partial tear.

The translational potential of this article

The thermosensitive hydrogel-PRP is potentially translated to clinical use to treat patients with ACL partial tear by injection under arthroscopy or ultrasound guiding.

Paediatric proximal ACL tears managed with direct ACL repair is safe, effective and has excellent short-term outcomes

PURPOSE

Anterior cruciate ligament (ACL) surgery in the paediatric population has long been a challenge. Non-operative treatment will result in persistent instability which can lead to chondral and meniscal injuries. The results of primary open ACL repair are poor. Concerns of growth plate disturbance with transphyseal techniques and issues with relatively small-diameter grafts in Tanner 1 and 2 patients, which are inadequate, have contributed to these challenges. With advancing instrumentation, there is renewed interest in ACL repair. The minimally invasive approach of arthroscopic primary ACL repair retains the native ligament. The objective and subjective outcomes at 2 years are presented.

METHODS

Paediatric patients, less than 16 years of age, presenting acutely with complete proximal ACL ruptures underwent direct arthroscopic ACL repair, reinforced by a temporary internal brace, which was subsequently removed after 3 months. Patient-reported outcome measures including the Lysholm, Tegner and KOOS scores were collected at 6 months, 1 year and 2 years post-operatively.

RESULTS

Twenty patients (age 6-16) completed data at 2 years post-operatively. There were no failures, no complications and no growth disturbance out to 2 years. The 2-year postoperative outcomes; Lysholm 95 (90-100), Tegner 7 (6-10), KOOS-Child 96.5 (88.9-100) demonstrated statistically significant improvements following surgery (p < 0.001). Objective measurements with an accelerometer did not demonstrate any significant side-to-side difference.

CONCLUSION

ACL repair for proximal ACL tears in the paediatric population demonstrates the potential for excellent outcomes at short-term follow-up. This presents an attractive alternative to ACL reconstruction when an adequate ACL remnant permits direct repair. Our results demonstrate that paediatric ACL repair is safe and effective.

Bridge-Enhanced Anterior Cruciate Ligament Repair Is Not Inferior to Autograft Anterior Cruciate Ligament Reconstruction at 2 Years: Results of a Prospective Randomized Clinical Trial

BACKGROUND

Preclinical studies suggest that for complete midsubstance anterior cruciate ligament (ACL) injuries, a suture repair of the ACL augmented with a protein implant placed in the gap between the torn ends (bridge-enhanced ACL repair [BEAR]) may be a viable alternative to ACL reconstruction (ACLR).

HYPOTHESIS

We hypothesized that patients treated with BEAR would have a noninferior patient-reported outcomes (International Knee Documentation Committee [IKDC] Subjective Score; prespecified noninferiority margin, -11.5 points) and instrumented anteroposterior (AP) knee laxity (prespecified noninferiority margin, +2-mm side-to-side difference) and superior muscle strength at 2 years after surgery when compared with patients who underwent ACLR with autograft.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

One hundred patients (median age, 17 years; median preoperative Marx activity score, 16) with complete midsubstance ACL injuries were enrolled and underwent surgery within 45 days of injury. Patients were randomly assigned to receive either BEAR (n = 65) or autograft ACLR (n = 35 [33 with quadrupled semitendinosus-gracilis and 2 with bone-patellar tendon-bone]). Outcomes-including the IKDC Subjective Score, the side-to-side difference in instrumented AP knee laxity, and muscle strength-were assessed at 2 years by an independent examiner blinded to the procedure. Patients were unblinded after their 2-year visit.

RESULTS

In total, 96% of the patients returned for 2-year follow-up. Noninferiority criteria were met for both the IKDC Subjective Score (BEAR, 88.9 points; ACLR, 84.8 points; mean difference, 4.1 points [95% CI, -1.5 to 9.7]) and the side-to-side difference in AP knee laxity (BEAR, 1.61 mm; ACLR, 1.77 mm; mean difference, -0.15 mm [95% CI, -1.48 to 1.17]). The BEAR group had a significantly higher mean hamstring muscle strength index than the ACLR group at 2 years (98.2% vs 63.2%; P < .001). In addition, 14% of the BEAR group and 6% of the ACLR group had a reinjury that required a second ipsilateral ACL surgical procedure (P = .32). Furthermore, the 8 patients who converted from BEAR to ACLR in the study period and returned for the 2-year postoperative visit had similar primary outcomes to patients who had a single ipsilateral ACL procedure.

CONCLUSION

BEAR resulted in noninferior patient-reported outcomes and AP knee laxity and superior hamstring muscle strength when compared with autograft ACLR at 2-year follow-up in a young and active cohort. These promising results suggest that longer-term studies of this technique are justified.

REGISTRATION

NCT02664545 (ClinicalTrials.gov identifier).

Artificial ligament made from silk protein/Laponite hybrid fibers

With developments in tissue engineering, artificial ligaments are expected to be future materials for anterior cruciate ligament (ACL) reconstruction. However, poor healing of the intraosseous part after ACL reconstruction significantly hinders their applications in this field. In this study, a bioactive clay Laponite (LAP) was introduced into the regenerated silk fibroin (RSF) spinning dope to produce functional RSF/LAP hybrid fibers by wet-spinning. These RSF/LAP hybrid fibers were then woven into artificial ligament for ACL reconstruction. The structure and mechanical properties of RSF/LAP hybrid fibers were extensively studied by different means. Results confirmed the presence of LAP in RSF fibers and revealed that the addition of LAP slightly deteriorated the comprehensive mechanical properties of RSF fibers. However, they were still much tougher (with higher breaking energy) than those of degummed natural silkworm silk that was earlier used for making artificial ligament. The artificial ligament woven from RSF/LAP hybrid fibers showed better cytocompatibility and osteogenic differentiation with mouse pre-osteoblasts in vitro than those made from degummed natural silkworm silks and pure RSF fibers. Furthermore, in vivo study in a rat ACL reconstruction model demonstrated that the presence of LAP in the artificial ligament could significantly enhance the graft osseointegration process and also improve the corresponding biomechanical properties of the artificial ligament. Based upon these results, the RSF/LAP hybrid fibers, which can be mass produced by wet-spinning process, are believed to have a great potential for use as artificial ligament materials for ACL reconstruction. STATEMENT OF SIGNIFICANCE: In this study, we successfully introduced Laponite (LAP), a kind of clay that has the function of osteogenic induction, into regenerated silk fibroin (RSF) fibers, which was prepared by a mature wet-spinning method developed in our lab. We believe that through artificial spinning, additional functional components can be added into RSF fibers, which one can hardly achieve with natural silks. We showed that the artificial ligament woven from RSF/LAP hybrid fibers had better cytocompatibility and osteogenic differentiation for mouse pre-osteoblasts in vitro, and significantly enhanced the graft osseointegration process and improved the corresponding biomechanical properties in a rat ACL reconstruction model in vivo, compared to those artificial ligaments made from degummed natural silkworm silks and pure RSF fibers.

Clinical Outcomes of Arthroscopic Primary Anterior Cruciate Ligament Repair: A Systematic Review from the Scientific Anterior Cruciate Ligament Network International Study Group

PURPOSE

To perform a systematic review of contemporary studies reporting clinical outcomes of primary anterior cruciate ligament (ACL) repair to determine whether these studies demonstrate any significant benefit of ACL repair and whether there is evidence of a deterioration of mid-term outcomes as seen in historical data.

METHODS

A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A PubMed search using the keywords "repair" AND "Anterior Cruciate Ligament" was performed (limits: English language, publication date between January 1, 2014, and January 13, 2019). All identified studies reporting clinical outcomes of arthroscopic ACL repair were included. Critical appraisal was conducted using the Cochrane Risk of Bias Tool for Randomized Clinical Trials and the Methodological Index for Non-Randomized Studies. Basic parameters of each study including population characteristics, repair technique, physical examination findings, and clinical outcome scores were recorded and evaluated.

RESULTS

Nineteen eligible studies were identified (including 5 comparative studies). None of the comparative studies showed any significant difference between repair and reconstruction groups with respect to International Knee Documentation Committee (IKDC), Lysholm, Tegner, side-to-side laxity difference, Lachman, pivot shift tests, or graft rupture rates. Four non-comparative studies reported outcomes at medium- to long-term follow up (range of mean follow up 43.3-79 months) with a mean Lysholm score between 85.3 and 100, mean IKDC subjective score between 87.3 and 100, and mean Tegner activity score between 5 and 7.

CONCLUSIONS

Comparative studies identified no significant differences between ACL repair and reconstruction with respect to Lysholm, IKDC, side-to-side laxity difference, pivot shift grade, or graft rupture rates. However, these studies had major limitations including small numbers and short durations of follow up. Case series demonstrated that excellent outcomes can be achieved at medium- to long-term follow up with the SAR technique.

LEVEL OF EVIDENCE

IV; Systematic review of Level II to IV investigations.

A multi-chamber tissue culture device for load-dependent parallel evaluation of tendon explants

Background

Injuries in the musculoskeletal system, such as tendon and ligament ruptures, are challenging to manage and often require surgical reconstructions with limited long-term success. Thus, characterizations of these tissues are urgently needed to better understand cellular mechanisms that regulate tissue homeostasis and healing. Explant culturing systems allow for ex vivo analysis of tissues in an environment that mimics the native microenvironment in vivo.

Methods

Collaborative efforts within our institution facilitated the establishment of a novel explant culturing system. Tissue specimens cultured in single wells, with individual applied loading and/or biological environment, allowed characterization of tissue cultured under a variety of biological loading conditions. Quantitative PCR analysis for selected gene markers was our primary outcome.

Results

Data were stratified for analysis by either culture environment or loading condition. Our gene expression results show that specimens clustered by culture condition may differ in molecular markers related to ECM production (e.g., Col1a1, Adamts4) and/or organization (e.g., Tnc, Dnc). In contrast, loading condition did significantly alter the median gene expression levels of tissues in comparison to unloaded control samples, although gene expression values related to ECM degradation (e.g., Mmp1, Mmp10) were altered in tendons cultured under tension in the device.

Conclusion

Our study demonstrates promising utility of a novel explant culturing system for further characterization of musculoskeletal tissues such as native tendons and ligaments, as well as pathologic fibrotic tissues resulting from arthrofibrosis or Dupuytren’s disease.

In vivo assessment of high-molecular-weight polyethylene core suture tape for intra-articular ligament reconstruction: an animal study

AIMS

Options for the treatment of intra-articular ligament injuries are limited, and insufficient ligament reconstruction can cause painful joint instability, loss of function, and progressive development of degenerative arthritis. This study aimed to assess the capability of a biologically enhanced matrix material for ligament reconstruction to withstand tensile forces within the joint and enhance ligament regeneration needed to regain joint function.

MATERIALS AND METHODS

A total of 18 New Zealand rabbits underwent bilateral anterior cruciate ligament reconstruction by autograft, FiberTape, or FiberTape-augmented autograft. Primary outcomes were biomechanical assessment (n = 17), microCT (µCT) assessment (n = 12), histological evaluation (n = 12), and quantitative polymerase chain reaction (qPCR) analysis (n = 6).

RESULTS

At eight weeks, FiberTape alone or FiberTape-augmented autograft demonstrated increased biomechanical stability compared with autograft regarding ultimate load to failure (p = 0.035), elongation (p = 0.006), and energy absorption (p = 0.022). FiberTape-grafted samples also demonstrated increased bone mineral density in the bone tunnel (p = 0.039). Histological evaluation showed integration of all grafts in the bone tunnels by new bone formation, and limited signs of inflammation overall. A lack of prolonged inflammation in all samples was confirmed by quantification of inflammation biomarkers. However, no regeneration of ligament-like tissue was observed along the suture tape materials. Except for one autograft failure, no adverse events were detected.

CONCLUSION

Our results indicate that FiberTape increases the biomechanical performance of intra-articular ligament reconstructions in a verified rabbit model at eight weeks. Within this period, FiberTape did not adversely affect bone tunnel healing or invoke a prolonged elevation in inflammation. Cite this article: Bone Joint J 2019;101-B:1238-1247.

Cartilage Damage Is Related to ACL Stiffness in a Porcine Model of ACL Repair

Inferior anterior cruciate ligament (ACL) structural properties may inadequately restrain tibiofemoral joint motion following surgery, contributing to the increased risk of post-traumatic osteoarthritis. Using both a direct measure of ACL linear stiffness and an in vivo magnetic resonance imaging (MRI) T₂ *-based prediction model, we hypothesized that cartilage damage and ACL stiffness would increase over time, and that an inverse relationship between cartilage damage and ACL stiffness would emerge at a later stage of healing. After either 6, 12, or 24 weeks (w) of healing after ACL repair, ACL linear stiffness was determined from the force-displacement relationship during tensile testing ex vivo and predicted in vivo from the MRI T₂ *-based multiple linear regression model in 24 Yucatan minipigs. Tibiofemoral cartilage was graded postmortem. There was no relationship between cartilage damage and ACL stiffness at 6 w (R²  = 0.04; p = 0.65), 12 w (R²  = 0.02; p = 0.77), or when the data from all animals were pooled (R²  = 0.02; p = 0.47). A significant inverse relationship between cartilage damage and ACL stiffness based on both ex vivo measurement (R²  = 0.90; p < 0.001) and in vivo MRI prediction (R²  = 0.78; p = 0.004) of ACL stiffness emerged at 24 w. This result suggests that 90% of the variability in gross cartilage changes is associated with the repaired ACL linear stiffness at 6 months of healing. Clinical Significance: Techniques that provide a higher stiffness to the repaired ACL may be required to mitigate the post-traumatic osteoarthritis commonly seen after ACL injury, and MRI T₂ * can be used as a noninvasive estimation of ligament stiffness. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2249-2257, 2019.

Non-operative treatment of ACL injury is associated with opposing subjective and objective outcomes over 20 years of follow-up

PURPOSE

The aim of this study was the evaluation of long-term clinical and radiological outcomes of non-operative treatment of anterior cruciate ligament (ACL) deficiency. The hypothesis was that conservative treatment would be associated with a deterioration of subjective and objective measures of joint health and disability over time.

METHODS

From an initial sample of 41 patients conservatively treated for ACL rupture, 10 received secondary ACL reconstruction, 1 was excluded due to contralateral ACL injury, and 1 patient required total knee replacement and a high tibial osteotomy. Seven further patients were lost to follow-up. The remaining 21 patients (15 male, 6 female, mean age 53.1 ± 9.2 years at the last follow-up) were evaluated by the same two examiners 5-7, 10-13 and 20-22 years after the injury. The evaluation was based on objective and subjective scores, instrumented testing, radiographic examination and assessment of sports activity.

RESULTS

While subjective patient satisfaction improved over time, objective scores stayed constant or deteriorated (radiologic evaluation). Instrumented knee laxity testing showed an initial tendency to increasing instability, followed by a decrease in anterior tibial translation in the second half of the observation period. Physical activity levels, particularly in high-risk sports, decreased significantly (p < 0.05) compared to preinjury levels. All patients developed significant arthritic degenerative changes over time compared to the uninjured contralateral knee. No correlation to activities in high- or low-risk pivoting sports was found.

CONCLUSIONS

Patient satisfaction with conservative treatment of ACL injuries is good in spite of objective measures indicating increasing degenerative changes.

LEVEL OF EVIDENCE

IV.

Changes in Cross-sectional Area and Signal Intensity of Healing Anterior Cruciate Ligaments and Grafts in the First 2 Years After Surgery

BACKGROUND

The quality of a repaired anterior cruciate ligament (ACL) or reconstructed graft is typically quantified in clinical studies by evaluating knee, lower extremity, or patient performance. However, magnetic resonance imaging of the healing ACL or graft may provide a more direct measure of tissue quality (ie, signal intensity) and quantity (ie, cross-sectional area).

HYPOTHESES

(1) Average cross-sectional area or signal intensity of a healing ACL after bridge-enhanced ACL repair (BEAR) or a hamstring autograft (ACL reconstruction) will change postoperatively from 3 to 24 months. (2) The average cross-sectional area and signal intensity of the healing ligament or graft will correlate with anatomic features of the knee associated with ACL injury.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Patients with a complete midsubstance ACL tear who were treated with either BEAR (n = 10) or ACL reconstruction (n = 10) underwent magnetic resonance imaging at 3, 6, 12, and 24 months after surgery. Images were analyzed to determine the average cross-sectional area and signal intensity of the ACL or graft at each time point. ACL orientation, stump length, and bony anatomy were also assessed.

RESULTS

Mean cross-sectional area of the grafts was 48% to 98% larger than the contralateral intact ACLs at all time points (P < .01). The BEAR ACLs were 23% to 28% greater in cross-sectional area than the contralateral intact ACLs at 3 and 6 months (P < .02) but similar at 12 and 24 months. The BEAR ACLs were similar in sagittal orientation to the contralateral ACLs, while the grafts were 6.5° more vertical (P = .005). For the BEAR ACLs, a bigger notch correlated with a bigger cross-sectional area, while a shorter ACL femoral stump, steeper lateral tibial slope, and shallower medial tibial depth were associated with higher signal intensity (R² > .40, P < .05). Performance of notchplasty resulted in an increased ACL cross-sectional area after the BEAR procedure (P = .007). No anatomic features were correlated with ACL graft size or signal intensity.

CONCLUSION

Hamstring autografts were larger in cross-sectional area and more vertically oriented than the native ACLs at 24 months after surgery. BEAR ACLs had a cross-sectional area, signal intensity, and sagittal orientation similar to the contralateral ACLs at 24 months. The early signal intensity and cross-sectional area of the repaired ACL may be affected by specific anatomic features, including lateral tibial slope and notch width-observations that deserve further study in a larger cohort of patients.

REGISTRATION

NCT02292004 (ClinicalTrials.gov identifier).

Figure-of-4 Cruciate Remnant Objective Assessment Test Reducibility of Anterior Cruciate Ligament Stump for Feasibility of Arthroscopic Primary Anterior Cruciate Ligament Repair

Suture of the anterior cruciate ligament (ACL) has reemerged as a treatment option for proximal ACL tears. Preoperative imaging can provide insight into the feasibility of performing arthroscopic primary ACL repair, but the final decision is taken only after confirming with arthroscopy that the ACL remnant is reducible. We describe a test called the Figure-of-4 Cruciate Remnant Objective Assessment test that objectively interprets the reducibility of the ACL remnant for arthroscopic primary ACL repair.

MRI following primary repair of the anterior cruciate ligament

Primary repair of the anterior cruciate ligament (ACL) is being performed increasingly in the treatment of acute proximal ACL ruptures. Advantages of ACL repair over surgical reconstruction with a tendon graft include preservation of the anatomy and proprioceptive function of the native ACL, and therefore, faster rehabilitation. The addition of an internal brace protects the repair during ACL healing and can increase the success rate of the procedure. Given this evolution of ACL surgical treatment, radiologists should be familiar with the new repair techniques and their appearances on postoperative imaging. In this article, we describe two different surgical techniques for primary ACL repair, dynamic intraligamentary stabilisation and internal brace ligament augmentation, and provide an overview of the normal and abnormal appearances after this type of repair at magnetic resonance imaging (MRI) follow-up.

Postoperative Magnetic Resonance Imaging following Arthroscopic Primary Anterior Cruciate Ligament Repair

Introduction

Recently, there has been a resurgence of interest in arthroscopic primary anterior cruciate ligament (ACL) repair. To date, no studies have assessed the role of postoperative magnetic resonance imaging (MRI) on the status and maturation of the repaired ligament. The goal of this study was therefore to assess (I) the accuracy of MRI on rerupture of the repaired ligament and (II) the maturation of the repaired ACL.

Methods

All postoperative MRIs of patients that underwent arthroscopic primary ACL repair were included. A musculoskeletal radiologist, blinded for MRI indication, surgery-MRI time interval, and clinical stability, retrospectively assessed the ligament continuity and graded ligament maturation as hypointense (similar to intact PCL), isointense (>50% similar to PCL), or hyperintense (<50% similar to PCL).

Results

Thirty-seven MRIs were included from 36 patients. Mean age was 30 years (range: 14–57 years), and mean surgery-MRI interval was 1.5 years (range: 0.1–4.9 years). The radiologist recognized 6 out of 8 reruptures and 26 out of 29 intact ligaments (sensitivity 75%, specificity 90%, and accuracy 86%). Ligaments in the first year were more often hyperintense than after one year (60% vs. 11%, p=0.02), most often isointense (60%) between one and two years, and more often hypointense after two years than before two years (56% vs. 10%, p=0.03).

Conclusion

Postoperative MRI was found to accurately predict the rerupture of the primarily repaired ACL. Furthermore, it can be expected that the repaired ligament is hyperintense within the first year, while the signal becomes similar to the intact PCL after two years.

Acute Anterior Cruciate Ligament Rupture: Repair or Reconstruction? Two-Year Results of a Randomized Controlled Clinical Trial

BACKGROUND

Contemporary anterior cruciate ligament (ACL) suture repair techniques have been subject to renewed interest in recent years. Although several clinical studies have yielded good short-term results, high-quality evidence is lacking in regard to the effectiveness of this treatment compared with ACL reconstruction.

HYPOTHESIS

Dynamic augmented ACL suture repair is at least as effective as anatomic single-bundle ACL reconstruction for the treatment of acute ACL rupture in terms of patient self-reported outcomes at 2 years postoperatively.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

After stratification and randomization, 48 patients underwent either dynamic augmented ACL suture repair or ACL reconstruction with a single-bundle, all-inside, semitendinosus technique. The International Knee Documentation Committee (IKDC) subjective score at 2 years postoperatively was the primary outcome measure. Patient-reported outcomes (IKDC subjective score, Knee injury and Osteoarthritis Outcome Score, Tegner score, visual analog scale for satisfaction), clinical outcomes (IKDC physical examination score, leg symmetry index for the quadriceps, hamstrings strength, and jump test battery), and radiological outcomes as well as adverse events including reruptures were recorded. Analyses were based on an intention-to-treat principle.

RESULTS

The lower limit for the median IKDC subjective score of the repair group (86.2) fell within the prespecified noninferiority margin, confirming noninferiority of dynamic augmented ACL suture repair compared with ACL reconstruction. No statistical difference was found between groups for median IKDC subjective score (repair, 95.4; reconstruction, 94.3). Overall, 2 reruptures (8.7%) occurred in the dynamic ACL suture repair group and 4 reruptures (19.0%) in the ACL reconstruction group; further, 5 repeat surgeries-other than for revision ACL surgery-took place in 4 patients from the dynamic ACL suture repair group (20.8%) and in 3 patients from the ACL reconstruction group (14.3%).

CONCLUSION

Dynamic augmented ACL suture repair is not inferior to ACL reconstruction in terms of subjective patient-reported outcomes as measured with the IKDC subjective score 2 years postoperatively. However, for reasons other than revision ACL surgery due to rerupture, a higher number of related adverse events leading to repeat surgery were seen in the dynamic augmented ACL suture repair group within 2 years postoperatively.

CLINICAL RELEVANCE

Dynamic augmented ACL suture repair might be a viable treatment option for patients with an acute ACL rupture.

REGISTRATION

NCT02310854 ( ClinicalTrials.gov identifier).

Dynamic augmentation restores anterior tibial translation in ACL suture repair: a biomechanical comparison of non-, static and dynamic augmentation techniques

PURPOSE

There is a lack of objective evidence investigating how previous non-augmented ACL suture repair techniques and contemporary augmentation techniques in ACL suture repair restrain anterior tibial translation (ATT) across the arc of flexion, and after cyclic loading of the knee. The purpose of this work was to test the null hypotheses that there would be no statistically significant difference in ATT after non-, static- and dynamic-augmented ACL suture repair, and they will not restore ATT to normal values across the arc of flexion of the knee after cyclic loading.

METHODS

Eleven human cadaveric knees were mounted in a test rig, and knee kinematics from 0° to 90° of flexion were recorded by use of an optical tracking system. Measurements were recorded without load and with 89-N tibial anterior force. The knees were tested in the following states: ACL-intact, ACL-deficient, non-augmented suture repair, static tape augmentation and dynamic augmentation after 10 and 300 loading cycles.

RESULTS

Only static tape augmentation and dynamic augmentation restored ATT to values similar to the ACL-intact state directly postoperation, and maintained this after cyclic loading. However, contrary to dynamic augmentation, the ATT after static tape augmentation failed to remain statistically less than for the ACL-deficient state after cyclic loading. Moreover, after cyclic loading, ATT was significantly less with dynamic augmentation when compared to static tape augmentation.

CONCLUSION

In contrast to non-augmented ACL suture repair and static tape augmentation, only dynamic augmentation resulted in restoration of ATT values similar to the ACL-intact knee and decreased ATT values when compared to the ACL-deficient knee immediately post-operation and also after cyclic loading, across the arc of flexion, thus allowing the null hypotheses to be rejected. This may assist healing of the ruptured ACL. Therefore, this study would support further clinical evaluation of dynamic augmentation of ACL repair.

Is There a Role for Internal Bracing and Repair of the Anterior Cruciate Ligament? A Systematic Literature Review

BACKGROUND

Renewed interest has arisen in arthroscopic anterior cruciate ligament (ACL) repair techniques.

HYPOTHESIS

ACL repair with or without some form of internal bracing could lead to good outcomes in a carefully selected subset of patients.

STUDY DESIGN

Systematic review.

METHODS

An electronic database search was performed to identify 89 papers describing preclinical and clinical studies on the outcome of ACL repair.

RESULTS

Proximal ACL tear patterns showed a better healing potential with primary repair than distal or midsubstance tears. Some form of internal bracing increased the success rate of ACL repair. Improvement in the biological characteristics of the repair was obtained by bone marrow access by drilling tunnels or microfracture. Augmentation with platelet-rich plasma was beneficial only in combination with a structural scaffold. Skeletally immature patients had the best outcomes. Acute repair offered improved outcomes with regard to load, stiffness, laxity, and rerupture.

CONCLUSION

ACL repair may be a viable option in young patients with acute, proximal ACL tears. The use of internal bracing, biological augmentation, and scaffold tissue may increase the success rate of repair.

A systematic review of long-term patient reported outcomes for the treatment of anterior cruciate ligament injuries in the skeletally immature

PURPOSE

To systematically review the available literature regarding outcomes for the treatment of anterior cruciate ligament (ACL) injuries in the skeletally immature at skeletal maturity or more than five years after surgery.

METHODS

A systematic search was performed of seven online databases for literature reporting patient reported outcomes for the treatment of ACL injuries in the skeletally immature. A systematic review of this literature was performed examining the outcomes and their association with skeletal immaturity and treatment techniques.

RESULTS

A total of 18 articles reported the outcomes of 425 subjects. The mean age at surgery ranged from 10.3 to 15 years. Mean follow-up ranged from 36 to 163 months. Ten studies followed up subjects until skeletal maturity. Mean outcome scores were similar for extraphyseal (Lysholm 96.2 (95.7 to 97.4), Tegner 6.75, IKDC 95.4 (94 to 100)) and transphyseal surgery (Lysholm 94.3 (84.6-100), Tegner 7.6 (6 to 8.7), International Knee Documentation Committee (IKDC) 93.6 (84 to 99)). However, the lower range boundary for Lysholm and IKDC was worse for the transphyseal group. The results for non-surgical treatments were worse (Lysholm 63.2, Tegner 4.8, IKDC 87). No significant differences were found in the incidence of limb-length discrepancy (p = 0.32), coronal plane growth disturbance (p = 0.48), graft rupture (p = 0.88) and persistent symptomatic instability (p = 0.11) with transphyseal and extraphyseal surgical techniques.

CONCLUSION

Both transphyseal and extraphyseal reconstructive techniques produced good patient reported outcomes, with no significant differences in the incidence of limb-length discrepancy, coronal plane growth disturbance, graft rupture and persistent symptomatic instability. They compare favourably with the repair techniques reviewed and the natural history of the condition. Further high-quality studies comparing the transphyseal and extraphyseal techniques are required.

LEVEL OF EVIDENCE

Level IV.

Effects of controlled abnormal joint movement on the molecular biological response in intra-articular tissues during the acute phase of anterior cruciate ligament injury in a rat model

Background

The anterior cruciate ligament (ACL) is responsible for braking forward movement of the tibia relative to the femur and for tibial rotation. After ACL injury, this braking performance deteriorates, inducing abnormal joint movement. The purpose of this study was to clarify the effects of controlled abnormal joint movement on the molecular biological response in intra-articular tissues during the acute phase of ACL injury.

Methods

Eighty-four mature Wistar male rats were randomly assigned to a controlled abnormal movement (CAM) group, an ACL-transection (ACL-T) group, a sham-operated group, or an intact group. The ACL was completely transected at its midportion in the ACL-T and CAM groups, and a nylon suture was used to control abnormal tibial translation in the CAM group. The sham-operated group underwent skin and joint capsule incisions and tibial drilling without ACL transection. Animals were not restricted activity until sacrifice 1, 3, or 5 days after surgery for histological and gene expression assessments. Acute-phase inflammation requires an important balance between degenerative and biosynthetic processes and is controlled by the activities of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Both types of gene were analyzed in this study.

Results

The ACL-T and CAM groups exhibited cleavage of the ACL at all time points. However, for the CAM group, the gap in the ligament stump was extremely small, and fibroblast proliferation was observed around the stump. Relative to the ACL-T group, the CAM group demonstrated significantly lower expression of MMP-13 mRNA and a lower MMP-13/TIMP-1 ratio on days 1 and 5 in the ACL, the medial meniscus and the lateral meniscus. The expression of TIMP-1 mRNA was not significantly different between the ACL-T and CAM groups.

Conclusions

The study results suggested that controlling abnormal movement inhibited the inflammatory reaction in intra-articular tissues after ACL injury. This reaction was down-regulated in intra-articular tissues in the CAM group. Abnormal joint control caused prolonged inflammation and inhibited remodeling during the acute phase of ACL rupture.

Reinterventions after dynamic intraligamentary stabilization in primary anterior cruciate ligament repair

BACKGROUND

The goal of this study was to perform an in-depth analysis of the frequency and cause of secondary interventions subsequent to primary anterior cruciate ligament (ACL) repair with dynamic intraligamentary stabilization (DIS).

METHODS

Between July 2009 and June 2014, 455 patients underwent DIS treatment. The minimum follow-up was 21months (mean 28months, range 21-64months).

RESULTS

A total of 215 (48.2%) reinterventions were performed in 190 (42.6%) patients. One-hundred and seventy-six (39.4%) were non-revision reinterventions, and 39 (8.7%) were revision ACL reconstructions. Re-arthroscopies included 26 (5.8%) scar tissue debridements with hardware removal due to range of motion deficits, 14 (3.1%) partial meniscectomies, four (0.9%) meniscal sutures, and four (0.9%) arthroscopies due to crepitation or knee pain. Minor non-revision reinterventions performed under analgosedation consisted of 97 (21.7%) hardware removals, 20 (4.5%) hardware removals with manipulations under anesthesia, and four manipulations under anesthesia alone (0.9%).

CONCLUSIONS

In our study, the revision rate was within the range of published results after ACL reconstructions. In over 90% of patients, the native ACL was preserved with no need for a secondary reconstruction. Most of the non-revision reinterventions were minor and included hardware removals and manipulations under anesthesia. The re-arthroscopy rate was lower than that after ACL reconstruction with fewer secondary meniscal sutures and partial meniscectomies. Early treatment of meniscal tears may be one crucial benefit of ACL repair with DIS.

Structural and Anatomic Restoration of the Anterior Cruciate Ligament Is Associated With Less Cartilage Damage 1 Year After Surgery: Healing Ligament Properties Affect Cartilage Damage

BACKGROUND

Abnormal joint motion has been linked to joint arthrosis after anterior cruciate ligament (ACL) reconstruction. However, the relationships between the graft properties (ie, structural and anatomic) and extent of posttraumatic osteoarthritis are not well defined.

HYPOTHESES

(1) The structural (tensile) and anatomic (area and alignment) properties of the reconstructed graft or repaired ACL correlate with the total cartilage lesion area 1 year after ACL surgery, and (2) side-to-side differences in anterior-posterior (AP) knee laxity correlate with the total cartilage lesion area 1 year postoperatively.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen minipigs underwent unilateral ACL transection and were randomly treated with ACL reconstruction or bridge-enhanced ACL repair. The tensile properties, cross-sectional area, and multiplanar alignment of the healing ACL or graft, AP knee laxity, and cartilage lesion areas were assessed 1 year after surgery.

RESULTS

In the reconstructed group, the normalized graft yield and maximum failure loads, cross-sectional area, sagittal and coronal elevation angles, and side-to-side differences in AP knee laxity at 60° of flexion were associated with the total cartilage lesion area 1 year after surgery (R² > 0.5, P < .04). In the repaired group, normalized ACL yield load, linear stiffness, cross-sectional area, and the sagittal and coronal elevation angles were associated with the total cartilage lesion area (R² > 0.5, P < .05). Smaller cartilage lesion areas were observed in the surgically treated knees when the structural and anatomic properties of the ligament or graft and AP laxity values were closer to those of the contralateral ACL-intact knee. Reconstructed grafts had a significantly larger normalized cross-sectional area and sagittal elevation angle (more vertical) when compared with repaired ACLs (P < .02).

CONCLUSION

The tensile properties, cross-sectional area, and multiplanar alignment of the healing ACLs or grafts and AP knee laxity in reconstructed knees were associated with the extent of tibiofemoral cartilage damage after ACL surgery.

CLINICAL RELEVANCE

These data highlight the need for novel ACL injury treatments that can restore the structural and anatomic properties of the torn ACL to those of the native ACL in an effort to minimize the risk of early-onset posttraumatic osteoarthritis.

Permanent knee sensorimotor system changes following ACL injury and surgery

The cruciate ligaments are components of the knee capsuloligamentous system providing vital neurosensory and biomechanical function. Since most historical primary ACL repair attempts were unsuccessful, reconstruction has become the preferred surgery. However, an increased understanding of the efficacy of lesion-site scaffolding, innovative suturing methods and materials, and evolving use of biological healing mediators such as platelet-rich plasma and stem cells has prompted reconsideration of what was once believed to be impossible. A growing number of in vivo animal studies and prospective clinical studies are providing increasing support for this intervention. The significance of ACL repair rather than reconstruction is that it more likely preserves the native neurosensory system, entheses, and ACL footprints. Tissue preservation combined with restored biomechanical function increases the likelihood for premorbid neuromuscular control system and dynamic knee stability recovery. This recovery should increase the potential for more patients to safely return to sports at their desired intensity and frequency. This current concepts paper revisits cruciate ligament neurosensory and neurovascular anatomy from the perspective of knee capsuloligamentous system function. Peripheral and central nerve pathways and central cortical representation mapping are also discussed. Surgical restoration of a more physiologically sound knee joint may be essential to solving the osteoarthritis dilemma. Innovative rehabilitative strategies and outcome measurement methodologies using more holistic and clinically relevant measurements that closely link biomechanical and neurosensory characteristics of physiological ACL function are discussed. Greater consideration of task-specific patient physical function and psychobehavioral links should better delineate the true efficacy of all ACL surgical and non-surgical interventions. Level of evidence IV.

Osteogenic and tenogenic induction of hBMSCs by an integrated nanofibrous scaffold with chemical and structural mimicry of the bone–ligament connection

A novel electrospinning nanofiber collecting device was designed and utilized to fabricate an integrated PCL nanofibrous scaffold with a “random–aligned–random” structure.

The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) Procedure: An Early Feasibility Cohort Study

Background:

This study assessed the safety of the newly developed bridge-enhanced anterior cruciate ligament (ACL) repair (BEAR), which involves suture repair of the ligament combined with a bioactive scaffold to bridge the gap between the torn ligament ends. As the intra-articular environment is complex in its response to implanted materials, this study was designed to determine whether there would be a significant rate of adverse reaction to the implanted scaffold.

Hypothesis:

The primary hypothesis was that the implanted scaffold would not result in a deep joint infection (arthrocentesis with positive culture) or significant inflammation (clinical symptoms justifying arthrocentesis but negative culture). The secondary hypotheses were that patients treated with BEAR would have early postoperative outcomes that were similar to patients treated with ACL reconstruction with an autologous hamstring graft.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 20 patients were enrolled in this nonrandomized, first-in-human study. Ten patients received BEAR treatment and 10 received a hamstring autograft ACL reconstruction. The BEAR procedure was performed by augmenting a suture repair with a proprietary scaffold, the BEAR scaffold, placed in between the torn ends of the ACL at the time of suture repair. The BEAR scaffold is to our knowledge the only device that fills the gap between the torn ligament ends to have current Investigational Device Exemption approval from the Food and Drug Administration. Ten milliliters of autologous whole blood were added to the scaffold prior to wound closure. Outcomes were assessed at 3 months postoperatively. The outcomes measures included postoperative pain, muscle atrophy, loss of joint range of motion, and implant failure (designated by an International Knee Documentation Committee grade C or D Lachman test and/or an absence of continuous ACL tissue on magnetic resonance images).

Results:

There were no joint infections or signs of significant inflammation in either group. There were no differences between groups in effusion or pain, and no failures by Lachman examination criteria (BEAR, 8 grade A and 2 grade B; ACL reconstruction, 10 grade A). Magnetic resonance images from all of the BEAR and ACL-reconstructed patients demonstrated a continuous ACL or intact graft. In addition, hamstring strength at 3 months was significantly better in the BEAR group than in the hamstring autograft group (mean ± SD: 77.9% ± 14.6% vs 55.9% ± 7.8% of the contralateral side; P < .001).

Conclusion:

The results of this study suggest that the BEAR procedure may have a rate of adverse reactions low enough to warrant a study of efficacy in a larger group of patients.

Effect of Changing the Joint Kinematics of Knees With a Ruptured Anterior Cruciate Ligament on the Molecular Biological Responses and Spontaneous Healing in a Rat Model

BACKGROUND

The poor healing capacity of a completely ruptured anterior cruciate ligament (ACL) has been attributed to an insufficient vascular supply, cellular metabolism, and deficient premature scaffold formation because of the unique intra-articular environment. However, previous studies have focused on intra-articular factors without considering extra-articular factors, including the biomechanical aspects of ACL-deficient knees.

HYPOTHESIS

Changing the joint kinematics of an ACL-ruptured knee will improve cellular biological responses and lead to spontaneous healing through the mechanotransduction mechanism.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 66 skeletally mature Wistar rats were randomly assigned to a sham-operated group (SO), ACL-transection group (ACL-T), controlled abnormal movement group (CAM), and an intact group (IN). The ACL was completely transected at the midportion in the ACL-T and CAM groups, and the CAM group underwent extra-articular braking to control for abnormal tibial translation. The SO group underwent skin and joint capsule incisions and tibial drilling, without ACL transection and extra-articular braking. The animals were allowed full cage activity until sacrifice at 1, 2, 4, 6, and 8 weeks postoperatively for histological, molecular biological, and biomechanical assessment.

RESULTS

All injured ACLs in the ACL-T group were not healed, but those in the CAM group healed spontaneously, showing a typical ligament healing response. Regarding the molecular biological response, there was an upregulation of anabolic factors (ie, transforming growth factor-β) and downregulation of catabolic factors (ie, matrix metalloproteinase). Examination of the mechanical properties at 8 weeks after injury showed that >50% of the strength of the intact ACL had returned.

CONCLUSION

Our results suggest that changing the joint kinematics of knees with a ruptured ACL alters the molecular biological responses and leads to spontaneous healing. These data support our hypothesis that the mechanotransduction mechanism mediates molecular responses and determines whether the ACL will heal.

CLINICAL RELEVANCE

Elucidating the relationship between the mechanotransduction mechanism and healing responses in knees with completely ruptured ACLs may result in the development of novel nonsurgical treatment that enables the ACL to spontaneously heal in patients who are not suitable for reconstruction.

Primary repair of the anterior cruciate ligament: A paradigm shift

Over the last century, many surgical treatments have been developed in the orthopedic field, including treatments of anterior cruciate ligament (ACL) injuries. These treatments ideally evolve in a process of trial and error with prospective comparison of new treatments to the current treatment standard. However, these evolutions are sometimes not linear and periodically undergo paradigm shifts. In this article, we review the evolution of ACL treatment and explain how it underwent a paradigm shift. Open primary ACL repair was the most common treatment in the 1970s and 1980s, but because multiple studies noted deterioration of outcomes at mid-term follow-up, in addition to several randomized clinical trials (RCTs) that noted better outcomes following ACL reconstruction, the open primary repair technique was abandoned. At the end of the primary repair era, however, several studies showed that outcomes of open primary repair were good to excellent and did not deteriorate when this technique was selectively performed in patients with proximal ACL tears, whereas primary repair led to disappointing and unpredictable results in patients with mid-substance tears. Unfortunately, enrollment of patients in the aforementioned RCTs was already finished, ultimately leading to abandoning of open primary repair, despite the advantages of ligament preservation. In this review, we discuss (I) why the evolution of ACL treatment underwent a paradigm shift, (II) which factors may have played a role in this and (III) what the future role of arthroscopic primary ACL repair is in the evolution of ACL treatments.