Current Anterior Cruciate Ligament Research Articles

Motivation Unraveled: Giving Choice to Football Players to Improve Anterior Cruciate Ligament Injury Prevention.

Benjaminse, A, Nijmeijer, EM, Gokeler, A, Broekhaar, DC, and Cortes, N. Motivation unraveled: giving choice to football players to improve anterior cruciate ligament injury prevention. J Strength Cond Res XX(X): 000-000, 2024-Providing athletes some control over a training session facilitates motor skill acquisition. This is a promising concept to use in anterior cruciate ligament (ACL) injury prevention, as the key for risk reduction is to improve quality of movement. The goal of this study was to better understand why improved motor learning occurred when football players had the opportunity to choose when to receive feedback when practicing sidestep cutting (SSC) movements. Healthy male recreational football players (n = 22, 22.9 ± 1.7 years, 185.5 ± 7.2 cm, 79.3 ± 9.2 kg) were included and assigned to the self-control (SC) or the yoked (YK) group. The players performed anticipated and unanticipated SSC. They received video instructions and were instructed to "copy the movement of the model to the best of their ability." During the training blocks, the SC group could ask for feedback, whereas the YK group could not. Cutting movement assessment scores (CMAS) were measured to test quality of movement and the Intrinsic Motivation Inventory was administered to measure constructs of motivation. In the anticipated condition, SC group showed better scores in immediate post and the retention test compared with pretest (p < 0.001), whereas the YK group showed worse scores in the retention test compared with immediate posttest (p = 0.001). Perceived competence (p = 0.017) and self-efficacy (p = 0.032) were consistent factors that correlated with improved CMAS in the SC group. This has given us innovative insights into underlying mechanisms optimizing the quality of movement, necessary to improve current ACL injury prevention approaches.

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Using the Anatomic Double-Bundle 2-in-1 Guide System

Background: In double-bundle anterior cruciate ligament (ACL) reconstruction, tunnel coalition may occur intraoperatively or during the postoperative course. Tibial tunnel coalition is more common compared with femoral tunnel coalition. Once tunnel coalition occurs on the tibial side, rotatory knee laxity may not be controlled as expected. We have developed a new device to avoid tibial tunnel coalition with consistency. The purpose of this video is to present the surgical technique for double-bundle ACL reconstruction using a new drill guide. Indications: The novel guide may be used in all cases with confirmed ACL tear in a physically active patient, identical to indications for current ACL reconstruction using the double-bundle technique. Technique Description: The hamstring tendon is harvested for the ACL grafts. Two guide pins for the anteromedial bundle and posterolateral bundle for the tibial tunnel are inserted through the Anatomic Double-Bundle 2-in-1 Guide System. Cannulated drills and dilators are used to create the tunnel to the final diameter. Next, femoral tunnels are created by the outside-in technique using the Anatomic Double-Bundle 2-in-1 Guide System. Grafts are inserted from the tibia and passed through the femur. The grafts are fixed with a post screw and/or interference screw. Results: Two weeks after surgery, no tibial or femoral coalition (0/20 cases) were confirmed and tibial bony bridge at the intraarticular surface was measured 2.7 ± 0.9 mm using computed tomography (CT). One year after surgery, tibial coalition was confirmed in 13.3% (2/15 cases), and femoral coalition in 6.7% (1/15 cases) on CT image mainly due to tunnel widening. The 2 cases with tibial coalition had tibial bony bridge of less than 2 mm on immediate postoperative CT. Discussion/Conclusion: Using the novel guide, 2 tibial tunnels were created easily and accurately compared with the conventional independent drilling technique. The 2 tunnels can also be created simultaneously with single placement of the guide. Two separate tunnels help maintain expected rotatory knee stability after double-bundle ACL reconstruction. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Rebranding the ‘anatomic’ ACL reconstruction: Current concepts

The anterior cruciate ligament (ACL) is a complex ribbon-like structure, which is approximately 3.5 times larger at the tibial and femoral insertions than at the midpoint. Accordingly, it is impossible to recreate with a single cylindrical graft. However, this has not stopped surgeons from using the term “anatomic” to describe multiple ACL reconstruction techniques inserting at a number of different locations within the original ACL footprint, causing confusion. The term “anatomic” should be discarded and replaced by an anatomic description of the tunnel placements on the tibia and femur. Current ACL reconstruction techniques cite anatomical studies that identified “direct and indirect fibres” of the ACL. The “direct fibres” bear 85–95% of the load and provide the main resistance to both anterior tibial translation and internal rotation/pivot shift. On the femur, these fibres insert in a line just posterior to the intercondylar ridge and comprise the portion of the ACL that surgeons should strive to restore. Placement of the graft just posterior to the intercondylar ridge creates a line of placement options from the anteromedial bundle to the “central” position and finally to the posterolateral bundle position. The authors prefer placing the femoral tunnel in the isometric anteromedial position and addressing a high-grade pivot shift at the IT-band with a lateral extra-articular tenodesis. As with the femoral tunnel, the native ACL footprint on the tibia is much larger than the ACL graft and thus can be placed in multiple “anatomic” locations. The authors prefer placement of the tibial tunnel in the anterior most position of the native footprint that does not cause impingement in the femoral notch. Additional research is needed to determine the ideal tunnel positions on the femur and tibia and validating the technique with patient outcomes. However, this cannot be accomplished without describing tunnel placement with specific anatomical locations so other surgeons can replicate the technique.

Biomarkers of Knee Joint Healing in Adolescents Following Anterior Cruciate Ligament Reconstruction: A Systematic Review

Background:Anterior cruciate ligament (ACL) injuries are increasing in prevalence by 2.3% annually in adolescents and have been linked to an increased risk for early-onset knee osteoarthritis (OA). Current ACL rehabilitation guidelines do not directly account for the physiological healing process of the knee joint. Instead, the sole focus is on a patients’ perceived function and their ability to meet functional benchmarks in the lower extremities. The physiological healing process could provide prognostic insight for clinicians and physiotherapists when rehabilitating ACL-injured patients.Hypotheses/Purpose:The purpose of this systematic review was to identify existing literature to determine i) the most prevalent biomarkers for reflecting knee joint healing in patients after ACL reconstruction (ACLR), and ii) the quantity of these studies which include adolescents. Methods: Following PRISMA guidelines, Medline, Embase, SCOPUS and Web of Science databases were searched up until September 2020. Studies were included if they (1) included participants who had sustained a primary ACL injury and undergone a subsequent ACLR, and (2) measured at least one biomarker of knee joint healing at more than one time point. An NIH quality assessment tool was used to assess study quality. The following data were extracted: participant age; biological sample(s); biomarker(s) analyzed.Results:Seven studies met inclusion criteria for this systematic review (Table 1). Interleukin-6 (IL-6) and C-terminal crosslinking telopeptide of type II collagen (CTX-II) were the most prevalent biomarkers used in the literature (3/7 studies). These biomarkers reflected knee joint healing through consistent elevation and/or gradual decrease following ACLR. Six studies evaluated adult populations (age range; Table 1). One study (average age 19.6±4.5) evaluated the effect of age on biomarker levels of knee joint healing and showed a negative correlation between age and CTX-II concentrations (r=-.769, p < 0.001). Conclusions: This systematic review identified (i) seven studies which evaluated healing using biomarkers following ACLR, (ii) IL-6 and CTX-II were most commonly used, and (iii) there is little research evaluating the physiological healing of the knee joint in any cohorts, in particular adolescent patients following ACLR. Adolescents are unique from adults due to growth and sex hormone variation. Therefore, what little biomarker research completed in adults cannot simply be extrapolated to adolescents. In addition to existing biomechanical rehabilitation tasks, we propose that rehabilitation and return to activity assessment following ACLR in adolescents could be informed by the healing status of the knee, improving outcomes and reducing their risk of early-onset knee OA.Table 1.Most prevalent biomarkers of knee joint healing after ACLR, and participant age, from included studies.

Graft Selection in Contemporary Anterior Cruciate Ligament Reconstruction

In the last decade, there have been significant advances in our understanding of anterior cruciate ligament (ACL) reconstruction. Recent prospective cohort studies have identified risk factors for ACL reconstruction graft failure such as younger patient age, increased activity level, nonanatomic tunnel placement, and the use of allograft. Among these, the most easily modifiable risk factor is graft choice. Given that the surgeon's recommendation has been shown to be one of the most important factors behind patients' graft choice, it is critical that the operating surgeon have a thorough understanding of all the ACL graft options available to choose the graft that would be most suitable for the patient's personalized reconstruction (i.e., patient's anatomy, sport, level of competition, age, risk factors for failure, and graft used in previous ACL surgery). The purpose of this review is to provide an up-to-date understanding of the current ACL graft reconstruction options. The indications, advantages, and disadvantages of the different ACL reconstruction graft options available will be discussed.

Implementing ACL Injury Prevention in Daily Sports Practice\u2014It\u2019s Not Just the Program: Let\u2019s Build Together, Involve the Context, and Improve the Content

Although the benefits of current anterior cruciate ligament (ACL) injury prevention programmes have been demonstrated in efficacy studies, they, unfortunately, have had limited public health impact to date. For example, the incidence of ACL injuries continues to rise in adolescent athletes. Raising awareness and educating coaches and athletes is not enough to facilitate the widespread, sustained use of these programmes in the real-world setting. Considering the profound burden of ACL injuries, it is necessary to continue to improve the current ACL injury prevention programmes through co-creation. First, the uptake of the programmes should be optimized by a better appreciation and understanding of the individual, socio-cultural and environmental context (i.e., community). Second, the content of the programmes should be optimized to better reflect the demands of the sport by creating more ownership and increasing motivation (incorporating challenging, sport-specific and fun elements) with the end-users. In addition, implicit motor learning, random practice and differential learning are concepts that should be integrated when practising to obtain the most optimal results when learning or finetuning skills.

Characterisation of the tensile properties of Demineralised Cortical Bone when used as an anterior cruciate ligament allograft

BackgroundGraft choice in anterior cruciate ligament (ACL) reconstruction remains controversial and some grafts fail due to inadequate osteointegration. Demineralised cortical bone (DCB) is an osteoinductive collagen-based scaffold. The aim of this study was to measure the tensile properties of DCB from different locations and from different ages, and determine its compatibility with current ACL fixation systems. MethodsThe tensile properties of DCB manufactured from femur and tibia of young (9 month) and old (2–3 years) sheep was measured to determine the most appropriate graft choice. The ultimate load and stiffness of DCB allograft using two fixation systems, interference screws and sutures tied around screw posts, was measured ex vivo in an ovine ACL reconstruction model. Comparison was made with superficial digital flexor tendon (SDFT) and ovine ACL. ResultsDCB derived from young tibia had the highest ultimate load and stiffness of 67.7 ± 10.6 N and 130.2 ± 64.3 N/mm respectively. No DCB fixation system reached the published peak in vivo force through the ovine ACL of 150 N. SDFT fixation with interference screws (308.2 ± 87.3 N) did reach the in vivo threshold but was significantly weaker than ovine ACL (871.0 ± 64.2 N). ConclusionThe tensile properties of DCB were influenced by the donor age and bone. Owing to inferior tensile properties and incompatibility with suspensory fixation devices, this study indicates DCB is inferior to current tendon grafts options for ACL reconstruction.

Uninjured Youth Athlete Performance on Single-Leg Hop Testing: How Many Can Achieve Recommended Return-to-Sport Criterion?

Current anterior cruciate ligament reconstruction (ACLR) guidelines utilize single-leg hop tests (SLHTs) to assist in return-to-sport decision making. A limb symmetry index (LSI) of ≥90% is often required; however, after ACLR, most youth athletes cannot achieve this standard. Reporting the performance of age-matched normative controls will allow clinicians to compare post-ACLR performance with noninjured peers, improving the utility of SLHTs. The purpose of this study was to report hop test LSI within healthy youth athletes and determine whether athlete performance surpasses post-ACLR requirements. The LSI for the majority of healthy youth athletes will be ≥90%. Cross-sectional cohort study. Level 3. Each participant performed a single hop (SH), triple hop (TrH), crossover hop (CrH), and timed hop (TiH). A 3-trial mean was utilized to calculate an LSI (nondominant/dominant leg [self-reported kicking leg]) for each hop. The frequency of pass/fail at ≥90% LSI was calculated. Pearson correlation coefficients analyzed the relationship between the different hops, and a 2-way analysis of variance determined the effects of age and sex on LSI. A total of 340 participants (54% male; mean age, 10.9 ± 1.5 years; range, 8-14 years) were included. The mean LSI was >95% for each SLHT (SH, 97.9% [SD, 0.7]; TrH, 96.6% [SD, 0.6]; CrH, 96.8% [SD, 0.8]; TiH, 96.5% [SD, 0.6]). When analyzed as a test battery, only 45% of participants achieved this standard. Significantly weak to moderate correlations existed among hop tests (P < 0.01; r = 0.342-0.520). Age and sex had no effect on LSI (P < 0.05). While the mean LSI in our sample was >95% for each individual hop test, participant performance across all SLHT components varied, such that less than half of healthy athletes could achieve ≥90% LSI across all hops. Current guidelines require ≥90% LSI on SLHTs. The majority of healthy youth athletes could not achieve this standard, which questions the validity of this LSI threshold in youth athletes after ACLR.

The Age of hMSC Donor Affects Biomechanical Properties of Tissue Engineered Ligament Constructs

Anterior cruciate ligament (ACL) tears are a major orthopedic challenge. Based on an incidence of 200,000 ACL repairs per year in the United States, the associated cost is in excess of $4 billion annually. Current ACL reconstruction commonly involves the use of allogenic or autogenic tendon grafts. Outcomes for ACL reconstruction with these techniques are limited by graft availability, donor site morbidity, disease transmission, and incomplete integration of native tissue within the surgically created bone tunnel. Thus, there is a demand for alternative tissue sources for ACL reconstruction. Using human derived mesenchymal stem cells (hMSC) as a starting material, we have successfully fabricated scaffold‐less ligament grafts that form their own extracellular matrix and have used these grafts for ACL reconstruction in a sheep model. To better understand the mechanism of graft development during our fabrication process, hMSCs were cultured and harvested at: Day 0 (initial plating), Day 4 (growth phase), Day 8 (differentiation phase), and Day 12 (3‐D construct) for qPCR analysis of bone and ligament markers. At day 15, 3‐D constructs were tested for biomechanics and histology (Fig. 1). The biomechanics data indicated two significantly different cohorts (n&gt;3 per donor per time point) that could be explained by age (young vs. old). In the young cohort (23–25y), the mean tangent modulus of the engineered ligament was significantly stiffer at 19.0 ± 3.2 kPa compared to the old cohort (33–43 y) at 8.7 ± 1.01 kPa. Average gene expression of ligament markers relative to GAPDH were analyzed via qPCR at defined time points during fabrication. We used a combination of gene targets (Collagen 1, Collagen 3, Tenascin C, and Scleraxis) to confirm commitment of the MSCs toward a ligament lineage and to determine any age‐related differences in gene expression. Compared to undifferentiated hMSCs (Day 0), the young cohort showed significantly increased expression of ligament markers Col‐1 &amp; Ten‐C by Day 4, and Col‐3 by Day 8. The old cohort showed an upward trend in the expression of Col‐1 and TenC, but did not reach significance at any time point, compared to age‐matched and undifferentiated hMSCs. Lastly, both the old and young cohort peaked in expression levels of Scleraxis at day 4, followed by a decline (Fig. 2). Additionally, we assessed the presence of collagen in the fully formed constructs with Picrosirius red staining. The images confirm that collagen was present in the constructs at 72 hours following monolayer roll up and there appears to be, qualitatively, less collagen presence in the construct cross sections fabricated from the cells or the 43 y.o donor compared to the constructs fabricated using cells from the 22 y.o donor. In addition, there is an increase in CSA surface area of dense collagen bands in the constructs derived from the cells of young donors compared to the constructs from the older cohort. Based on these data, we conclude that the use of younger donor cells will yield a stiffer and more robust ligament constructs due to the increased generation of ECM. In conclusion, constructs fabricated from the cells of younger donors were stiffer, had collagen deposition, and had earlier expression of ligament markers, all of which will enhance graft effectiveness and clinical outcomes.Figure 1Figure 2

Treatment of Acute Proximal Anterior Cruciate Ligament Tears-Part 2: The Role of Internal Bracing on Gap Formation and Stabilization of Repair Techniques.

Background:The latest biomechanical studies on some form of internal bracing have shown improved stabilization for anterior cruciate ligament (ACL) repair, but gap formation and load-sharing function have not yet been reported.Hypothesis:Internal bracing of an adjustable ACL repair construct provides improved stabilization with reduced gap formation and higher residual loading on the ACL.Study Design:Controlled laboratory study.Methods:Internally braced ACL repair constructs with single– and double–cinch loop (CL) cortical buttons, a knotless suture anchor, and a single-CL cortical button with adjustable loop fixation (CLS-ALD) were tested (n = 20 each) in a porcine model at 4 different loads (n = 5 each) over 4000 cycles at 0.75 Hz (n = 80 total). The CLS-ALD technique allowed for additional preconditioning (10 cycles at 0.5 Hz). Test results of the isolated internal brace groups served as a baseline for comparison. Lastly, specimens were pulled to failure (50 mm/min) with a cut internal brace. Final loading and gap formation on the ACL repair construct as well as ultimate strength were analyzed.Results:A statistical significance for peak loads over peak elongation was found between the CLS-ALD and all other reinforced groups (analysis of covariance, P < .001). Accordingly, the adjustable repair technique showed improved load-bearing capability with the internal brace compared with all other fixed repair groups and revealed significantly higher loads than the knotted single-CL group. Also, significantly reduced gap formation was found for the CLS-ALD compared with all other groups (P < .001), with no gap formation up to 150 N with a final gap of 0.85 ± 0.31 mm at 350 N. A significantly higher ultimate failure load (866.2 ± 104.0 N; P < .001) was found for the button-fixed internal brace group compared with all other groups.Conclusion:Internal bracing had a crucial role in improving the stabilization potential of ACL repair at loads occurring during normal daily activity. The added strength of the internal brace allowed for reducing peak loads on the ACL repair construct as well as restricting gap formation to below 3 mm at loads up to 350 N.Clinical Relevance:Improvements in the mechanical characteristics of current ACL repair techniques that enable reduced gap formation and allow for early range of motion and accelerated rehabilitation may strengthen the self-healing response with the formation of stable scar tissue.

Treatment of Acute Proximal Anterior Cruciate Ligament Tears-Part 1: Gap Formation and Stabilization Potential of Repair Techniques.

Background:Recently, there has been a resurgence of interest in primary repair of the anterior cruciate ligament (ACL), with fixation techniques evolving. However, to date, there have been no biomechanical studies comparing fixed to adjustable fixation repair techniques.Hypothesis:Adjustable ACL repair provides for improved stabilization compared with fixed techniques with respect to both gap formation and residual load-bearing capability.Study Design:Controlled laboratory study.Methods:A total of 4 different ACL repair techniques (n = 5 per group), including single– and double–cinch loop (CL) cortical button fixation as well as knotless single–suture anchor fixation, were tested using a porcine model. For adjustable single-CL loop fixation, additional preconditioning (10 cycles at 0.5 Hz) was performed. The force after fixation and the actuator displacement to achieve a time-zero preload of 10 N were measured for fixed techniques. Incrementally increasing cycling (1 mm/500 cycles) from 1 to 8 mm was performed for 4000 cycles at 0.75 Hz before pull to failure (50 mm/min). The final residual peak load and gap formation for each test block were analyzed as well as ultimate strength.Results:Knot tying of a single-CL over a button (mean ± SD, 0.66 ± 0.23 mm) and knotless anchor fixation (0.20 ± 0.12 mm) resulted in significant time-zero gaps (P < .001) and significantly higher overall gap formation at reduced residual loading (analysis of covariance, P < .001) compared with both the double-CL loop and adjustable fixation techniques. The adjustable group showed the highest failure load and stiffness, at 305.7 N and 117.1 N/mm, respectively. The failure load of the knotted single-CL group was significantly reduced compared with all other groups (P < .001).Conclusion:Adjustable single-CL cortical button fixation with intraoperative preconditioning optimized time-zero ACL tension and led to significantly improved stabilization and reduced gap formation, with the highest ultimate strength. Single-CL loop knot tying over the button and knotless anchor fixation resulted in time-zero gaps to achieve slight tension on the ACL and significantly higher gap formation at reduced load-bearing capability.Clinical Relevance:Although the clinical relevance of gap formation is uncertain, a biomechanical understanding of the stabilization potential of current ACL repair techniques is pertinent to the continued evolution of surgical approaches to enable better clinical outcomes.

A Majority of Anterior Cruciate Ligament Injuries Can Be Prevented by Injury Prevention Programs: A Systematic Review of Randomized Controlled Trials and Cluster–Randomized Controlled Trials With Meta-analysis

Background: Anterior cruciate ligament (ACL) injury prevention programs (IPPs) are generally accepted as being valuable for reducing injury risk. However, significant methodological limitations of previous meta-analyses raise questions about the efficacy of these programs and the extent to which meeting current best-practice ACL IPP recommendations influences the protective effect of these programs. Purpose: To (1) estimate the protective effect of ACL IPPs while controlling for common methodological limitations of previous meta-analyses and (2) systematically categorize IPP components and factors related to IPP delivery to assess the validity of current best-practice IPP recommendations. Study Design: Systematic review with meta-analysis. Methods: A systematic search of 5 electronic scientific databases was conducted to identify studies testing the efficacy of ACL IPPs. Studies were included if (1) the intervention aimed to prevent ACL injury, (2) the incidence rate (IR) or other outcome data that made it possible to calculate the IR for both the intervention and control groups were reported, and (3) the study design was a prospective randomized controlled trial (RCT) or cluster-RCT. Results: Of the 2219 studies screened, 8 studies were included in the quantitative synthesis, and their analysis revealed a significant reduction in ACL IR when athletes received IPPs (IR ratio = 0.47; 95% CI, 0.30-0.73; P < .001). The majority of included IPPs tended to meet minimum best-practice recommendations and incorporated plyometric, strengthening, and agility exercises along with feedback on proper landing technique. However, the specific exercises included in each IPP and key factors related to IPP delivery were highly variable. Conclusion: Despite limiting the analysis to only high-quality studies and controlling for time at risk and potential clustering effects, the study showed that ACL IPPs had a significant protective effect and reduced injury rates by 53%. However, significant variability in the specific exercises and the manner of program delivery suggests that ACL IPPs may be able to be designed within an overarching best-practice framework. This may allow practitioners the flexibility to develop IPPs that meet the specific characteristics of the target population and potentially increase the likelihood that these programs will be widely adopted and implemented.

The Use of Augmented Information for Reducing Anterior Cruciate Ligament Injury Risk During Jump Landings: A Systematic Review.

A comprehensive systematic review of the literature on the use of augmented information in anterior cruciate ligament (ACL) injury-prevention programs to improve jump-landing technique was conducted. The use of motor-learning concepts could provide more robust means of preventing ACL injuries. To systematically summarize the effectiveness of augmented information in improving the biomechanical factors associated with an increased risk for ACL injury. Articles were retrieved using the electronic databases of PubMed, MEDLINE, CINAHL, and Google Scholar and 3 lines of truncated search words: (a) lower extremity, knee, ACL, and anterior cruciate ligament; (b) prevention, injury prevention, and prehab; and (c) augmented information, augmented feedback, feedback, cue, and instruction. We also performed a hand search of the reference lists of the screened articles. We independently assessed the methodologic quality using the Cochrane Group on Screening and Diagnostic Test Methods list. Articles were placed in 1 of 3 augmented-information categories: prescriptive, feedback, or transition. Articles were also categorized based on whether the information likely encouraged an internal or external focus of attention. The searches identified a total of 353 studies, of which 18 were included. Most researchers found that augmented information could lead to technique changes to reduce the biomechanical risk factors associated with ACL injury. The average methodologic quality of the studies was 11.8 out of 17, with a range from 8 to 15. The authors of only 7 studies examined retention of the improved techniques. The evidence suggests that augmented information can be used to significantly improve the biomechanical indicators associated with ACL injury and to enhance current ACL injury-prevention programs. Combined prescriptive and feedback information that encouraged both internal and external foci led to the largest retention effect sizes.

Evidence-Based Best-Practice Guidelines for Preventing Anterior Cruciate Ligament Injuries in Young Female Athletes: A Systematic Review and Meta-analysis

Background: Injury prevention neuromuscular training (NMT) programs reduce the risk for anterior cruciate ligament (ACL) injury. However, variation in program characteristics limits the potential to delineate the most effective practices to optimize injury risk reduction. Purpose: To evaluate the common and effective components included in ACL NMT programs and develop an efficient, user-friendly tool to assess the quality of ACL NMT programs. Study Design: Systematic review and meta-analysis. Methods: Study inclusion required (1) a prospective controlled trial study design, (2) an NMT intervention aimed to reduce incidence of ACL injury, (3) a comparison group, (4) ACL injury incidence, and (5) female participants. The following data were extracted: year of publication, study design, sample size and characteristics, and NMT characteristics including exercise type and number per session, volume, duration, training time, and implementer training. Analysis entailed both univariate subgroup and meta-regression techniques using random-effects models. Results: Eighteen studies were included in the meta-analyses, with a total of 27,231 participants, 347 sustaining an ACL injury. NMT reduced the risk for ACL injury from 1 in 54 to 1 in 111 (odds ratio [OR], 0.51; 95% CI, 0.37-0.69]). The overall mean training volume was 18.17 hours for the entire NMT (24.1 minutes per session, 2.51 times per week). Interventions targeting middle school or high school–aged athletes reduced injury risk (OR, 0.38; 95% CI, 0.24-0.60) to a greater degree than did interventions for college- or professional-aged athletes (OR, 0.65; 95% CI, 0.48-0.89). All interventions included some form of implementer training. Increased landing stabilization and lower body strength exercises during each session improved prophylactic benefits. A meta-regression model and simple checklist based on the aforementioned effective components (slope = −0.15, P = .0008; intercept = 0.04, P = .51) were developed to allow practitioners to evaluate the potential efficacy of their ACL NMT and optimize injury prevention effects. Conclusion: Considering the aggregated evidence, we recommend that ACL NMT programs target younger athletes and use trained implementers who incorporate lower body strength exercises (ie, Nordic hamstrings, lunges, and heel-calf raises) with a specific focus on landing stabilization (jump/hop and hold) throughout their sport seasons. Clinical Relevance: Clinicians, coaches, athletes, parents, and practitioners can use the developed checklist to gain insight into the quality of their current ACL NMT practices and can use the tool to optimize programming for future ACL NMT to reduce ACL injury risk.

The Most Cited Original Articles on Anterior Cruciate Ligament Injuries in the Past 20 Years.

Anterior cruciate ligament (ACL) injuries continue to be a major focus in sports medicine research. With so many changes to our understanding of ACL anatomy and with rapid advances in reconstruction techniques and rehabilitation protocols within the past 20 years, it is important to identify the landmark research that has laid the foundation for current ACL treatments. Using the Web of Science citation index, a search was carried out for the 30 most cited articles on ACL injury published in the last 20 years. The generated list was sorted from highest to lowest citation number. Clinical studies were subcategorized as therapeutic, prognostic, diagnostic, or economic/decision analysis and assigned a level of evidence. Basic science articles were designated anatomic, animal, biomechanical, or clinical. The number of citations per year (citation density) was calculated. The search yielded 6,345 articles. The total number of citations among the top 30 ranged from 188 to 611. Citation density ranged from 10.1 to 66.2. Nineteen articles were clinical, 8 were basic science, and 3 were video analyses. Clinical articles were most commonly therapeutic (18 of 19; 95%). Basic science articles were most commonly biomechanical (7 of 8; 88%). The most common level of evidence was Level II (10 of 19; 53%). More than half of the articles in the top 30 (16 of 30; 53%) were published in The American Journal of Sports Medicine. Many of these articles have played a large role in shaping current clinical practice regarding ACL injuries. We hope that by compiling this list we can draw attention to the continued need for studies of the highest level of evidence.

A Systematic Review of ACL Reconstruction Rehabilitation

Background: Anterior Cruciate Ligament (ACL) reconstruction is a well-known surgical knee procedure performed by orthopaedic surgeons. There is a general consensus for the effectiveness of a postoperative ACL reconstruction rehabilitation program, however there is little consensus regarding the optimal components of a program Objective of the Study: to assess the merits and demerits of current ACL reconstruction rehabilitation programs and interventions based on the evidence supported by previously conducted systematic reviews. Methods: a Systematic search in the scientific database (Medline, Scopus, EMBASE , and Google Scholer) between 1970 and 2017 was conducted for all relevant Systematic reviews discussing the primary endpoint ( ACL reconstruction rehabilitation ) studies were analyzed and included based on the preset inclusion and exclusion criteria. Study screening and quality was assessed against PRISMA guidelines and a best evidence synthesis was performed. Results: the search results yielded five studies which evaluated eight rehabilitation components (bracing, Continuous passive motion (CPM), neuromuscular electrical stimulation (NMES), open kinetic chain (OKC) versus closed kinetic chain (CKC) exercise, progressive eccentric exercise, home versus supervised rehabilitation, accelerated rehabilitation and water based rehabilitation). A strong evidence suggested no added benefit of short term bracing (0-6 weeks post-surgery) compared to standard treatment. Whilst a moderate evidence reinforced no added advantage of continuous passive motion to standard treatment for boosting motion range. Furthermore, a moderate evidence of equal effectiveness of closed versus open kinetic chain exercise and home versus clinic based rehabilitation, on a range of short term outcomes. There was inconsistent or limited evidence for some interventions including: the use of NMES and exercise, accelerated and non-accelerated rehabilitation, early and delayed rehabilitation, and eccentric resistance programs after ACL reconstruction. Conclusion: short term post-operative bracing and continuous passive motion (CPM) introduce no benefit over standard treatment and thus not recommended. A moderate evidence suggested equal efficiency for 1) CKC and OKC are equally effective for knee laxity, pain and function, at least in the short term (6-14 weeks) after ACL reconstruction and 2) home based and clinic based rehabilitation. Nevertheless, the degree of physiotherapy input remains unclear.

Comparison of Anterior Cruciate Ligament Graft Isometry between Paired Femoral and Tibial Tunnels.

Accurate tunnel placement is important for a successful anterior cruciate ligament (ACL) reconstruction. Controversy exists concerning the preferred method of femoral tunnel preparation, with proponents of both medial portal and transtibial drilling techniques. Current ACL literature suggests that placement of the femoral ACL attachment site posterior or "low" in the ACL footprint leads to more anatomically correct ACL mechanics and better rotational control. There is limited literature focusing on ACL graft displacement through knee range of motion based on specific paired placement of femoral and tibial tunnels. Our purpose was to assess ACL isometry between multiple combinations of femoral and tibial tunnels. We hypothesized that placement of the graft at the posterior aspect of the ACL footprint on the femur would be significantly less isometric and lead to more graft displacement as compared with central or anterior placement. The ACL of matched pairs of cadaveric knees was arthroscopically debrided while leaving the soft tissue footprint on the femur and tibia intact. One knee from each pair underwent notchplasty. In all knees, three femoral and three tibial tunnels were created at the anterior, central, and posterior aspects of the ACL footprint. A suture was passed through each tunnel combination (nine potential pairs), and the change in isometry was measured throughout full knee range of motion. Placement of the femoral tunnel along the posterior aspect of the ACL footprint was less isometric compared with a central or anterior position in the femoral footprint. Placement of a posterior tibial tunnel also led to decreased isometry, but tibial tunnel placement affected isometry to a lesser extent than femoral tunnel placement. The combination of a posterior femoral and posterior tibial tunnel resulted in greater than 1 cm of graft excursion from full flexion to extension. Placement of ACL tunnels at anisometric sites may adversely affect the mechanical properties and behavior of the ACL graft, resulting in either graft laxity in flexion or overconstraint and loss of extension.

Efficacy of ACL injury risk screening methods in identifying high-risk landing patterns during a sport-specific task.

Screening methods sensitive to movement strategies that increase anterior cruciate ligament (ACL) loads are likely to be effective in identifying athletes at-risk of ACL injury. Current ACL injury risk screening methods are yet to be evaluated for their ability to identify athletes' who exhibit high-risk lower limb mechanics during sport-specific maneuvers associated with ACL injury occurrences. The purpose of this study was to examine the efficacy of two ACL injury risk screening methods in identifying high-risk lower limb mechanics during a sport-specific landing task. Thirty-two female athletes were screened using the Landing Error Scoring System (LESS) and Tuck Jump Assessment. Participants' also completed a sport-specific landing task, during which three-dimensional kinematic and kinetic data were collected. One-dimensional statistical parametric mapping was used to examine the relationships between screening method scores, and the three-dimensional hip and knee joint rotation and moment data from the sport-specific landing. Higher LESS scores were associated with reduced knee flexion from 30 to 57ms after initial contact (P=0.003) during the sport-specific landing; however, no additional relationships were found. These findings suggest the LESS and Tuck Jump Assessment may have minimal applicability in identifying athletes' who exhibit high-risk landing postures in the sport-specific task examined.

Gold and Hydroxyapatite Nano-Composite Scaffolds for Anterior Cruciate Ligament Reconstruction: In Vitro Characterization.

Current anterior cruciate ligament (ACL) graft replacement materials often fail due to the lack of biological integration. While many newly developed extracellular matrix based scaffolds show good biocompatibility they often do not entice cellular remodeling and the rebuilding of a functional ligament. We have proposed the conjugation of gold nanoparticles (AuNP) and hydroxyapatite nanoparticles (nano-HAp) to acellular tissue to enhance cell attachment and proliferation while maintaining an improved degradation resistance and open microstructure. We are the first to investigate the double conjugation of AuNP and nano-HAp onto decellularized tissue to improve the tissue remodeling response. Decellularized porcine diaphragm was crosslinked with two types of nano-HAp and amine-functionalized AuNP with 1-ethyl-3-(3-dimethlaminopropyl) carbodiimide (EDC) crosslinker. Scaffolds were characterized using electron microscopy, differential scanning calorimetry, and fibroblast assays. Results demonstrated that scaffolds with nano-HAp have increased thermal stability at low levels of crosslinking. The open microstructure of the scaffold was not compromised allowing for cell migration while still providing increased degradation resistance. The addition of < 200 nm nano-HAp decreased cell viability compared to scaffolds without nanoparticles, but the addition of AuNP to scaffolds showed enhanced cell viability in the presence of < 200 nm nano-HAp. The addition of < 40 nm nano-HAp showed an increase in cell viability compared to scaffolds crosslinked without nanoparticles. It is concluded that attaching AuNP and < 40nm nano-HAp to extracellular matrices may improve overall properties.

Enhanced retention of drop vertical jump landing technique: A randomized controlled trial

External focus instructions have been shown to result in superior motor performance compared to internal focus instructions. Using an EF may help to optimize current anterior cruciate ligament (ACL) injury prevention programs. The purpose of the current study was to investigate the effects of instructions on landing technique and performance by comparing an external focus (EF), internal focus (IF), video (VI) and control (CTRL) group. Subjects (age 22.50±1.62years, height 179.70±10.43cm, mass 73.98±12.68kg) were randomly assigned to IF (n=10), EF (n=10), VI (n=10) or CTRL group (n=10). Landing was assessed from a drop vertical jump (DVJ) in five sessions: pretest, two training blocks (TR1 and TR2) and directly after the training sessions (post test) and retention test 1week later. Group specific instructions were offered in TR1 and TR2. Landing technique was assessed with the Landing Error Scoring System (LESS) and jump height was taken as performance measure. The results show that males in the VI group and females both in the VI and EF groups significantly improved jump-landing technique. Retention was achieved and jump height was maintained for males in the VI group and females both in the VI and EF groups. It is therefore concluded that EF and VI instructions have great potential in ACL injury prevention.