Effects of various load magnitudes on ACL: an in vitro study using adolescent porcine stifle joints.

INTRODUCTION: The escalating incidence of anterior cruciate ligament (ACL) injuries, particularly among adolescents, is a pressing concern. The study of ACL biomechanics in this demographic presents challenges due to the scarcity of cadaveric specimens. This research endeavors to validate the adolescent porcine stifle joint as a fitting model for ACL studies. METHODS: We conducted experiments on 30 fresh porcine stifle knee joints. (Breed: Yorkshire, Weight: avg 90 lbs, Age Range: 2-4 months). They were stored at - 22 °C and a subsequent 24-h thaw at room temperature before being prepared for the experiment. These joints were randomly assigned to three groups. The first group served as a control and underwent only the load-to-failure test. The remaining two groups were subjected to 100 cycles, with forces of 300N and 520N, respectively. The load values of 300N and 520N correspond to three and five times the body weight (BW) of our juvenile porcine, respectively. RESULT: The 520N force demonstrated a higher strain than the 300N, indicating a direct correlation between ACL strain and augmented loads. A significant difference in load-to-failure (p = 0.014) was observed between non-cyclically loaded ACLs and those subjected to 100 cycles at 520N. Three of the ten samples in the 520N group failed before completing 100 cycles. The ruptured ACLs from these tests closely resembled adolescent ACL injuries in detachment patterns. ACL stiffness was also measured post-cyclical loading by applying force and pulling the ACL at a rate of 1 mm per sec. Moreover, ACL stiffness measurements decreased from 152.46 N/mm in the control group to 129.42 N/mm after 100 cycles at 300N and a more significant drop to 86.90 N/mm after 100 cycles at 520N. A one-way analysis of variance (ANOVA) and t-test were chosen for statistical analysis. CONCLUSIONS: The porcine stifle joint is an appropriate model for understanding ACL biomechanics in the skeletally immature demographic. The results emphasize the ligament's susceptibility to injury under high-impact loads pertinent to sports activities. The study advocates for further research into different loading scenarios and the protective role of muscle co-activation in ACL injury prevention.

Anterior Cruciate Ligament Reconstruction: Is Biological Augmentation Beneficial?

Surgical reconstruction in anterior cruciate ligament (ACL) ruptures has proven to be a highly effective technique that usually provides satisfactory results. However, despite the majority of patients recovering their function after this procedure, ACL reconstruction (ACLR) is still imperfect. To improve these results, various biological augmentation (BA) techniques have been employed mostly in animal models. They include: (1) growth factors (bone morphogenetic protein, epidermal growth factor, granulocyte colony-stimulating factor, basic fibroblast growth factor, transforming growth factor-ß, hepatocyte growth factor, vascular endothelial growth factor, and platelet concentrates such as platelet-rich plasma, fibrin clot, and autologous conditioned serum), (2) mesenchymal stem cells, (3) autologous tissue, (4) various pharmaceuticals (matrix metalloproteinase-inhibitor alpha-2-macroglobulin bisphosphonates), (5) biophysical/environmental methods (hyperbaric oxygen, low-intensity pulsed ultrasound, extracorporeal shockwave therapy), (6) biomaterials (fixation methods, biological coatings, biosynthetic bone substitutes, osteoconductive materials), and (7) gene therapy. All of them have shown good results in experimental studies; however, the clinical studies on BA published so far are highly heterogeneous and have a low degree of evidence. The most widely used technique to date is platelet-rich plasma. My position is that orthopedic surgeons must be very cautious when considering using PRP or other BA methods in ACLR.

Subjective assessment reported by patients shows differences between single-bundle and double-bundle anterior cruciate ligament reconstruction, systematic review and meta-analysis.

To determine the functional recovery, active reincorporation, and anteroposterior and rotational stability of patients undergoing anterior cruciate ligament (ACL) reconstruction using arthroscopy techniques with simple-bundle (SB) or double-bundle (DB). The following databases were searched: PubMed, Embase (Elsevier platform), the Cochrane Central Register of Controlled Trials (Wiley platform), Web of Science, and CINAHL. Level I and II studies involving anterior cruciate ligament arthroscopy were included in the search. Records were screened by title and abstract and assessed the risk of bias of selected studies. Meta-analyses using RevMan 5.3 software were conducted on the following outcomes: knee functionality, objective measurements of knee stability, rotational knee stability and knee anterior stability, sports reincorporation, and subjective assessments. Twenty-four studies of patients undergoing ACL reconstruction were included in the qualitative and quantitative synthesis (1707 patients) for Lysholm score, Subjective International Knee Documentation Committee (IKDC) score, Tegner score, KT-1000/2000, Lachman test, Objective IKDC score, and Pivot-Shift test. A return to pre-injury level showed a significant decrease in the Lysholm score (mean difference, - 0.99; 95% CI - 1.71 to - 0.40; P = 0.007) and Tegner score (mean difference, - 0.07; 95% CI, - 0.13 to - 0.01; P = 0.02) at DB reconstruction, similar to the knee functionality outcome of the subjective IKDC score (mean difference - 1.42; 95% CI - 2.46 to - 0.38; P = 0.007). There is no clear or significant difference in clinical stability and knee function or in sports incorporation with the true difference occurring in the subjective assessment.

Alterations in sensorimotor function after ACL reconstruction during active joint position sense testing. A systematic review.

BACKGROUND: The anterior cruciate ligament (ACL) rupture can lead to impaired knee function. Reconstruction decreases the mechanical instability but might not have an impact on sensorimotor alterations. OBJECTIVE: Evaluation of the sensorimotor function measured with the active joint position sense (JPS) test in anterior cruciate ligament (ACL) reconstructed patients compared to the contralateral side and a healthy control group. METHODS: The databases MEDLINE, CINAHL, EMBASE, PEDro, Cochrane Library and SPORTDiscus were systematically searched from origin until April 2020. Studies published in English, German, French, Spanish or Italian language were included. Evaluation of the sensorimotor performance was restricted to the active joint position sense test in ACL reconstructed participants or healthy controls. The Preferred Items for Systematic Reviews and Meta-Analyses guidelines were followed. Study quality was evaluated using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Data was descriptively synthesized. RESULTS: Ten studies were included after application of the selective criteria. Higher angular deviation, reaching significant difference (p < 0.001) in one study, was shown up to three months after surgery in the affected limb. Six months post-operative significantly less error (p < 0.01) was found in the reconstructed leg compared to the contralateral side and healthy controls. One or more years after ACL reconstruction significant differences were inconsistent along the studies. CONCLUSIONS: Altered sensorimotor function was present after ACL reconstruction. Due to inconsistencies and small magnitudes, clinical relevance might be questionable. JPS testing can be performed in acute injured persons and prospective studies could enhance knowledge of sensorimotor function throughout the rehabilitative processes.

Clinical, Functional, and Physical Activity Outcomes 5 Years Following the Treatment Algorithm of the Delaware-Oslo ACL Cohort Study.

BACKGROUND: Anterior cruciate ligament (ACL) injuries can be treated with or without ACL reconstruction (ACLR), and more high-quality studies evaluating outcomes after the different treatment courses are needed. The purpose of the present study was to describe and compare 5-year clinical, functional, and physical activity outcomes for patients who followed our decision-making and treatment algorithm and chose (1) early ACLR with preoperative and postoperative rehabilitation, (2) delayed ACLR with preoperative and postoperative rehabilitation, or (3) progressive rehabilitation alone. Early ACLR was defined as that performed ≤6 months after the preoperative rehabilitation program, and late ACLR was defined as that performed >6 months after the preoperative rehabilitation program. METHODS: We included 276 patients from a prospective cohort study. The patients had been active in jumping, pivoting, and cutting sports before the injury and sustained a unilateral ACL injury without substantial concomitant knee injuries. The patients chose their treatment through a shared decision-making process. At 5 years, we assessed the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF), Knee injury and Osteoarthritis Outcome Score (KOOS), Marx Activity Rating Scale, sports participation, quadriceps muscle strength, single-legged hop performance, and new ipsilateral and contralateral knee injuries. RESULTS: The 5-year follow-up rate was 80%. At 5 years, 64% of the patients had undergone early ACLR, 11% had undergone delayed ACLR, and 25% had had progressive rehabilitation alone. Understandably, the choices that participants made differed by age, concomitant injuries, symptoms, and predominantly level-I versus level-II preinjury activity level. There were no significant differences in any clinical, functional, or physical activity outcomes among the treatment groups. Across treatment groups, 95% to 100% of patients were still active in some kind of sports and 65% to 88% had IKDC-SKF and KOOS scores above the threshold for a patient acceptable symptom state. CONCLUSIONS: Patients with ACL injury who were active in jumping, pivoting, and cutting sports prior to injury; who had no substantial concomitant knee injuries; and who followed our decision-making and treatment algorithm had good 5-year knee function and high sport participation rates. Three of 4 patients had undergone ACLR within 5 years. There were no significant differences in any outcomes among patients treated with early ACLR, delayed ACLR, or progressive rehabilitation alone. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Texture analysis to differentiate anterior cruciate ligament in patients after surgery with platelet-rich plasma.

BACKGROUND: Platelet-rich plasma (PRP) has been used to favor anterior cruciate ligament (ACL) healing after reconstruction surgeries. However, clinical data are still inconclusive and subjective about PRP. Thus, we propose a quantitative method to demonstrate that PRP produced morphological structure changes. METHODS: Thirty-four patients undergoing ACL reconstruction surgery were evaluated and divided into control group (sixteen patients) without PRP application and experiment group (eighteen patients) with intraoperative application of PRP. Magnetic resonance imaging (MRI) scans were performed 3 months after surgery. We used Matlab® and machine learning (ML) in Orange Canvas® to texture analysis (TA) features extraction. Experienced radiologists delimited the regions of interest (RoIs) in the T2-weighted images. Sixty-two texture parameters were extracted, including gray-level co-occurrence matrix and gray level run length. We used the algorithms logistic regression (LR), naive Bayes (NB), and stochastic gradient descent (SGD). RESULTS: The accuracy of the classification with NB, LR, and SGD was 83.3%, 75%, 75%, respectively. For the area under the curve, NB, LR, and SGD presented values of 91.7%, 94.4%, 75%, respectively. In clinical evaluations, the groups show similar responses in terms of improvement in pain and increase in the IKDC index (International Knee Documentation Committee) and Lysholm score indices differing only in the assessment of flexion, which presents a significant difference for the group treated with PRP. CONCLUSIONS: Here, we demonstrated quantitatively that patients who received PRP presented texture changes when compared to the control group. Thus, our findings suggest that PRP interferes with morphological parameters of the ACL. TRIAL REGISTRATION: Protocol no. CAAE 56164316.6.0000.5411.

Multiple Ligament Knee Reconstructions.

Patients with multiligament knee injuries require a thorough examination (Lachman, posterior-drawer, varus, valgus, and rotational testing). Diagnoses are confirmed with magnetic resonance imaging as well as stress radiographs (posterior, varus, and valgus) when indicated. Multiple systematic reviews have reported that early (<3 weeks after injury) single-stage surgery and early knee motion improves patient-reported outcomes. Anatomic-based reconstructions of the torn primary static stabilizers and repair of the capsular structures and any tendinous avulsions are performed in a single-stage. Open anteromedial or posterolateral incisions are preferentially performed first to identify the torn structures and to prepare the posterolateral corner (PLC) and medial knee reconstruction tunnels. Next, arthroscopy allows preparation of the anterior cruciate ligament (ACL) and double-bundle (DB) posterior cruciate ligament (PCL) tunnels. Careful attention to tunnel trajectory minimizes the risk for convergence. Meniscal tears are preferentially repaired (root and ramp tears are commonly seen in this patient group). Graft passage is performed after all tunnels are reamed. The graft tensioning and fixation sequence is as follows: anterolateral bundle of the PCL to restore the central pivot, posteromedial bundle of the PCL, ACL, PLC (including fibular [lateral] collateral ligament), and posteromedial corner (including medial collateral ligament). Graft integrity and full knee range of motion should be verified before closure. Physical therapy commences on postoperative day 1 with immediate knee motion (flexion from 0°-90°; prone for DB-PCL reconstruction) and quadriceps activation. Patients are nonweightbearing for 6 weeks. Patients with ACL-based reconstructions wear an immobilizer for 6 weeks then transition to a hinged ACL brace. Patients with PCL-based reconstructions transition into a dynamic PCL brace once swelling subsides and wear it routinely for 6 months. Functional testing and stress radiography are performed to validate return to sports.

Anterior cruciate ligament reconstruction in a rabbit model using a silk-collagen scaffold modified by hydroxyapatite at both ends: a histological and biomechanical study.

BACKGROUND: To investigate osteointegration at the graft-bone interface and the prevention of osteoarthritis after anterior cruciate ligament (ACL) reconstruction using a silk-collagen scaffold with both ends modified by hydroxyapatite (HA) in a rabbit model. METHODS: The HA/silk-collagen scaffold was fabricated using a degummed, knitted silk scaffold, collagen I matrix, and simulated body fluid (SBF). The HA/silk-collagen scaffold was rolled up to make a graft for replacing the native ACL in the experimental group (HA group), and the silk-collagen scaffold was used in the control (S group). All specimens were harvested at 16 weeks postoperatively to evaluate graft-bone healing and osteoarthritis prevention. RESULTS: Histological staining revealed the massive formation of more mature bone at the tendon-bone interface, and immunohistochemistry staining revealed more collagen I and osteocalcin deposition in the HA group than in the S group. Higher signals indicating more bone mineral formation were detected in the HA group than in the S group, which was consistent with the results of biomechanical testing. Better osteoarthritis prevention was also observed in the HA group, indicating a more stable knee joint in the HA group than in the S group. CONCLUSION: The HA/silk-collagen scaffold promotes osteointegration at the tendon-bone interface after ACL reconstruction and has great potential for clinical applications.

Weight-bearing status affects in vivo kinematics following mobile-bearing unicompartmental knee arthroplasty.

PURPOSE: The effects of weight bearing (WB) on knee kinematics following mobile-bearing unicompartmental knee arthroplasty (UKA) remain unknown. The purpose of this study was to clarify the effects of WB on in vivo kinematics of mobile-bearing UKA during high knee flexion activities. METHODS: The kinematics of UKA were evaluated under fluoroscopy during squatting (WB) and active-assisted knee flexion (non-weight bearing, NWB). Range of motion, femoral axis rotation relative to the tibia, anteroposterior (AP) translation of the medial and lateral sides, and kinematic pathway were measured. RESULTS: There were no differences in knee flexion range and external rotation of the femur in each flexion angle between the WB conditions. The amount of femoral external rotation between minimum flexion and 60° of flexion during WB was significantly larger than that during NWB, and that between 60° and 130° of flexion during NWB was significantly larger than that during WB. There were no differences in medial AP translation of the femur in each flexion angle between the WB conditions. However, on the lateral side, posterior translation of 52.9 ± 12.7% was observed between minimum flexion and 130° of flexion during WB. During NWB, there was no significant translation between minimum flexion and 60° of flexion; beyond 60° of flexion, posterior translation was 41.6 ± 8.7%. Between 20° and 80° of flexion, the lateral side in WB was located more posteriorly than in NWB (p < 0.05). CONCLUSION: Mobile-bearing UKA has good anterior stability throughout the range of knee flexion. WB status affects the in vivo kinematics following mobile-bearing UKA. LEVEL OF EVIDENCE: III.

A Biomechanical Study of Pivot-Shift and Lachman Translations in Anterior Cruciate Ligament-Sectioned Knees, Anterior Cruciate Ligament-Reconstructed Knees, and Knees With Partial Anterior Cruciate Ligament Graft Slackening: Instrumented Lachman Tests Statistically Correlate and Supplement Subjective Pivot-Shift Tests.

PURPOSE: To determine the statistical and predictive correlation between instrumented Lachman and pivot-shift tests with progressive loss of anterior cruciate ligament (ACL) function. METHODS: The kinematic correlations between pivot-shift and Lachman anterior tibial translations (ATTs) in ACL-deficient and ACL-reconstructed states and in partially lax ACL grafts were determined with precise robotic testing in cadaveric knees. The Lachman test (100-N anteroposterior) and 2 pivot-shift loadings were conducted: anterior tibial loading (100 N), valgus rotation (7 Nm), and internal rotation (5 Nm and 1 Nm). The tibia was digitized to study the resulting medial, central, and lateral tibiofemoral compartment translations. In group 1 knees, 15 bone-patellar tendon-bone reconstructions were first tested, followed by ACL graft loosening with 3- and 5-mm increases in Lachman ATT. In group 2, 43 knees underwent robotic testing before and after ACL sectioning and underwent analysis of the effect of 3- and 5-mm increases in Lachman ATT and complete ACL sectioning on pivot-shift compartment translations. RESULTS: In group 1 knees, ACL graft loosening allowing a 3-mm increase in Lachman ATT resulted in increases in pivot-shift lateral compartment translation (lateral compartment ATT) of only 1.6 ± 0.3 mm and 2.2 ± 1.0 mm (internal rotation of 5 Nm and 1 Nm, respectively) that were one-half of those required for a positive pivot-shift test finding. In group 2, for a 3-mm increased Lachman test, there were no positive pivot-shift values. In both groups, a Lachman test with an increase in ATT of 3 mm or less (100 N) had a 100% predictive value for a negative pivot-shift test finding. With ACL graft loosening and a 5-mm increase in the Lachman ATT, group 1 still had no positive pivot-shift values, and in group 2, a positive pivot-shift test finding occurred in 3 of 43 knees (7%, pivot shift 1-Nm internal rotation). After ACL sectioning, a highly predictive correlation was found between abnormal increases in Lachman and pivot-shift translations (P < .001). CONCLUSIONS: ACL graft slackening and an instrumented Lachman test with an increase in ATT of 3 mm or less were 100% predictive of a negative pivot-shift subluxation finding and retained ACL stability. Further graft slackening and a 5-mm increase in the Lachman ATT produced pivot-shift lateral compartment ATT increases still less than the values in the ACL-deficient state; however, 7% of the knees (3 of 43) were converted to a positive pivot-shift test finding indicative of ACL graft failure. CLINICAL RELEVANCE: Instrumented Lachman tests provide objective data on ACL function and graft failure to supplement subjective pivot-shift tests and are highly recommended for single-center and multicenter ACL studies. In the past decade, a near majority of published ACL studies no longer reported on instrumented Lachman tests, relying solely on highly subjective pivot-shift grading by multiple examiners.

ACL deficiency influences medio-lateral tibial alignment and knee varus-valgus during in vivo activities.

PURPOSE: The role of the anterior cruciate ligament (ACL) in knee biomechanics in vivo and under weight-bearing is still unclear. The purpose of this study was to compare the tibiofemoral kinematics of ACL-deficient knees to healthy contralateral ones during the execution of weight-bearing activities. METHODS: Eight patients with isolated ACL injury and healthy contralateral knees were included in the study. Patients were asked to perform a single step forward and a single leg squat first with the injured knee and then with the contralateral one. Knee motion was determined using a validated model-based tracking process that matched subject-specific MRI bone models to dynamic biplane radiographic images, under the principles of Roentgen stereophotogrammetric analysis (RSA). Data processing was performed in a specific software developed in Matlab. RESULTS: Statistically significant differences (p < 0.05) were found for single leg squat along the frontal plane: ACL-deficient knees showed a more varus angle, especially at the highest knee flexion angles (40°-50° on average), compared to the contralateral knees. Furthermore, ACL-deficient knees showed tibial medialization along the entire task, while contralateral knees were always laterally aligned. This difference became statistically relevant (p < 0.05) for knee flexion angles included between 0° and about 30°. CONCLUSION: ACL-deficient knees showed an abnormal tibial medialization and increased varus angle during single leg squat when compared to the contralateral knees. These biomechanical anomalies could cause a different force distribution on tibial plateau, explaining the higher risk of early osteoarthritis in ACL deficiency. The clinical relevance of this study is that also safe activities used in ACL rehabilitation protocols are significantly altered in ACL deficiency. LEVEL OF EVIDENCE: III.

The superficial medial collateral ligament is the major restraint to anteromedial instability of the knee.

PURPOSE: The purpose of the present study was to determine how the medial structures and ACL contribute to restraining anteromedial instability of the knee. METHODS: Twenty-eight paired, fresh-frozen human cadaveric knees were tested in a six-degree of freedom robotic setup. After sequentially cutting the dMCL, sMCL, POL and ACL in four different cutting orders, the following simulated clinical laxity tests were applied at 0°, 30°, 60° and 90° of knee flexion: 4 Nm external tibial rotation (ER), 4 Nm internal tibial rotation (IR), 8 Nm valgus rotation (VR) and anteromedial rotation (AMR)-combined 89 N anterior tibial translation and 4 Nm ER. Knee kinematics were recorded in the intact state and after each cut using an optical tracking system. Differences in medial compartment translation (AMT) and tibial rotation (AMR, ER, IR, VR) from the intact state were then analyzed. RESULTS: The sMCL was the most important restraint to AMR, ER and VR at all flexion angles. Release of the proximal tibial attachment of the sMCL caused no significant increase in laxity if the distal sMCL attachment remained intact. The dMCL was a minor restraint to AMT and ER. The POL controlled IR and was a minor restraint to AMT and ER near extension. The ACL contributed with the sMCL in restraining AMT and was a secondary restraint to ER and VR in the MCL deficient knee. CONCLUSION: The sMCL appears to be the most important restraint to anteromedial instability; the dMCL and POL play more minor roles. Based on the present data a new classification of anteromedial instability is proposed, which may support clinical examination and treatment decision. In higher grades of anteromedial instability an injury to the sMCL should be suspected and addressed if treated surgically.

Effect of Slope and Varus Correction High Tibial Osteotomy in the ACL-Deficient and ACL-Reconstructed Knee on Kinematics and ACL Graft Force: A Biomechanical Analysis.

BACKGROUND: Correction of high posterior tibial slope is an important treatment option for revision of anterior cruciate ligament (ACL) failure as seen in clinical and biomechanical studies. In cases with moderate to severe medial compartment arthritis, an additional varus correction osteotomy may be added to improve alignment. PURPOSE: To investigate the influence of coronal and sagittal correction high tibial osteotomy in ACL-deficient and ACL-reconstructed knees on knee kinematics and ACL graft load. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were selected according to previous computed tomography measurements with increased native slope and slight varus tibial alignment (mean ± SD): slope, 9.9°± 1.4°; medial proximal tibia angle, 86.5°± 2.1°; age, 47.7 ± 5.8 years. A 10° anterior closing-wedge osteotomy, as well as an additional 5° of simulated varus correction osteotomy, were created and fixed using an external fixator. Four alignment conditions-native, varus correction, slope correction, and combined varus and slope correction-were randomly tested in 2 states: ACL-deficient and ACL-reconstructed. Compressive axial loads were applied to the tibia while mounted on a free-moving X-Y table and free-rotating tibia in a knee testing fixture. Three-dimensional motion tracking captured anterior tibial translation (ATT) and internal tibial rotation. Change of tensile forces on the reconstructed ACL graft were recorded. RESULTS: In the ACL-deficient knee, an isolated varus correction led to a significant increase of ATT by 4.3 ± 4.0 mm (P = .04). Isolated slope reduction resulted in the greatest decrease of ATT by 6.2 ± 4.3 mm (P < .001). In the ACL-reconstructed knee, ATT showed comparable changes, while combined varus and slope correction led to lower ATT by 3.7 ± 2.6 mm (P = .01) than ATT in the native alignment. Internal tibial rotation was not significantly altered by varus correction but significantly increased after isolated slope correction by 4.0°± 4.1° (P < .01). Each isolated or combined osteotomy showed decreased forces on the graft as compared with the native state. The combined varus and slope osteotomy led to a mean decrease of ACL graft force by 33% at 200 N and by 58% at 400 N as compared with the native condition (P < .001). CONCLUSION: A combined varus and slope correction led to a relevant decrease of ATT in the ACL-deficient and ACL-reconstructed cadaveric knee. ACL graft forces were significantly decreased after combined varus and slope correction. Thus, our biomechanical findings support the treatment goal of a perpendicular-aligned tibial plateau for ACL insufficiencies, especially in cases of revision surgery. CLINICAL RELEVANCE: This study shows the beneficial knee kinematics and reduced forces on the ACL graft after combined varus and slope correction.

The Anterolateral Ligament of the Knee: An Updated Systematic Review of Anatomy, Biomechanics, and Clinical Outcomes.

PURPOSE: To perform an updated systematic review of the anatomy, biomechanics, function of the anterolateral ligament (ALL), and the clinical outcomes of anterolateral ligament reconstruction (ALLR) when performed in conjunction with anterior cruciate ligament reconstruction (ACLR). METHODS: A systematic search of the literature was performed by searching PubMed, the Cochrane Library, and Embase with the search phrase anterolateral ligament for articles published from February 2017 to May 2020. Inclusion criteria included studies that evaluated the anatomy, function, or biomechanics of the ALL; surgical technique articles on ALLR; clinical articles reporting outcomes of ALLR; studies published in English; and full-text articles. Exclusion criteria included studies published before February 2017. A subjective synthesis was performed, in which ranges were reported, and individual study data were presented in forest plots. RESULTS: Overall, 40 articles were included in this systematic review, with 11 articles describing ALL anatomy, 14 articles analyzing ALL function and biomechanics, 7 articles discussing the surgical technique of combined ACLR and ALLR (ACLR/ALLR), and 8 articles describing the clinical outcomes of ACLR/ALLR. The addition of ALLR in combination with ACLR (ACLR+) results in lower graft failure rates for ACLR/ALLR (0.0%-15.7%) when compared with isolated ACLR (I-ACLR) patients (7.4%-21.7%). Three of 5 studies using the Subjective International Knee Documentation Committee score, 2 of 5 studies using the Lysholm score, and 1 of 2 studies using the Tegner score reported significantly better scores at latest follow-up among ACLR+ patients compared with I-ACLR (P < .05). CONCLUSIONS: The ALL acts as a secondary stabilizer to the anterior cruciate ligament and helps resist internal knee rotation and anterior tibial translation. Based on the current literature, combined ACLR with ALLR may result in lower graft failure rates and improved patient-reported outcomes when compared with I-ACLR in patients with specific indications, although several studies have shown equivalent outcomes between these 2 cohorts. CLINICAL RELEVANCE: The contents of this review provide great insight for orthopaedic surgeons who are performing ACLR and considering additional procedures to increase overall knee stability and decrease likeliness for re-rupture. The postoperative functional and clinical outcomes shown in patients undergoing ACLR+ compared with I-ACLR should be given proper consideration when evaluating available treatment courses.

Evidence for the effects of prehabilitation before ACL-reconstruction on return to sport-related and self-reported knee function: A systematic review.

STUDY DESIGN: Systematic review. BACKGROUND AND OBJECTIVES: Preoperative neuromuscular function is predictive for knee function and return to sports (RTS) after reconstruction of the anterior cruciate ligament (ACL). The aim of this review was to examine the potential benefits of prehabilitation on pre-/postoperative objective, self-reported and RTS-specific outcomes. METHODS: A systematic search was conducted within three databases. From the 1.071 studies screened, two randomized control trials (RCTs), two control trials (CTs) and two cohort studies (CS) met the inclusion criteria. Methodological quality rating adopted the PEDro- (RCT, CT) or Newcastle-Ottawa-Scale (CS). RESULTS AND CONCLUSIONS: Methodological quality of the included studies was moderate (PEDro score: 6.5 ± 1.7; range 4 to 9). Two studies reported higher increases of the maximal quadriceps torque from baseline to pre-reconstruction: one study in the limb symmetry index (LSI), and one in both legs of the prehabilitation group compared to the controls. At 12-weeks post-reconstruction, one study (from two) indicated that the prehabilitation group had a lesser post-operative decline in the single-leg-hop for distance LSI (clinically meaningful). Similar findings were found in terms of quadriceps strength LSI (one study). At both pre-reconstruction (three studies) and two-year post-surgery (two studies), the prehabilitation groups reached significantly higher self-reported knee function (clinically meaningful) than the controls. RTS tended to be faster (one study). At two years post-surgery, RTS rates (one study) were higher in the prehabilitation groups. The results provide evidence for the relevance of prehabilitation prior to ACL-reconstruction to improve neuromuscular and self-reported knee function as well as RTS. More high quality confirmatory RCTs are warranted. REGISTRATION NUMBER: PROSPERO 2017: CRD42017065491.

Single bout of vibration-induced hamstrings fatigue reduces quadriceps inhibition and coactivation of knee muscles after anterior cruciate ligament (ACL) reconstruction.

Persistent quadriceps strength deficits in individuals with anterior cruciate ligament reconstruction (ACLr) have been attributed to arthrogenic muscle inhibition (AMI). The purpose of the present study was to investigate the effect of vibration-induced hamstrings fatigue on AMI in patients with ACLr. Eight participants with unilateral ACLr (post-surgery time: M = 46.5, SD = 23.5 months; age: M = 21.4, SD = 1.4 years) and eight individuals with no previous history of knee injury (age: M = 22.5, SD = 2.5 years) were recruited. A fatigue protocol, consisting of 10 min of prolonged local hamstrings vibration, was applied to both the ACLr and control groups. The central activation ratio (CAR) of the quadriceps was measured with a superimposed burst of electrical stimulation, and hamstrings/quadriceps coactivation was assessed using electromyography (EMG) during isometric knee extension exercises, both before and after prolonged local vibration. For the ACLr group, the hamstrings strength, measured by a load cell on a purpose-built chair, was significantly (P = 0.016) reduced about 14.5%, indicating fatigue was actually induced in the hamstrings. At baseline, the ACLr group showed a trend (P = 0.051) toward a lower quadriceps CAR (M = 93.2%, SD = 6.2% versus M = 98.1%, SD = 1.1%) and significantly (P = 0.001) higher hamstrings/quadriceps coactivation (M = 15.1%, SD = 6.2% versus M = 7.5%, SD = 4.0%) during knee extension compared to the control group. The fatigue protocol significantly (P = 0.001) increased quadriceps CAR (from M = 93.2%, SD = 6.2% to M = 97.9%, SD = 2.8%) and significantly (P = 0.006) decreased hamstrings/quadriceps coactivation during knee extension (from M = 15.1%, SD = 6.2% to M = 9.5%, SD = 4.5%) in the ACLr group. In conclusion, vibration-induced hamstrings fatigue can alleviate AMI of the quadriceps in patients with ACLr. This finding has clinical implications in the management of recovery for ACLr patients with quadriceps strength deficits and dysfunction.

Single leg aerobic capacity and strength in individuals with surgically repaired anterior cruciate ligaments.

OBJECTIVES: Compare single-leg aerobic capacity and strength differences between the surgically repaired ACL leg (injured) and the uninjured leg. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Eight participants (5 female, 3 male, age = 23 ± 3.5 y, mass = 72.3 ± 17.3 kg, height = 169.7 ± 9.4 cm) that returned to play from ACL surgery between six and 18 months. MAIN OUTCOME MEASURES: Participants performed an aerobically-based, single-leg cycling protocol to determine maximum oxygen consumption, ventilatory threshold, heart rate, rating of perceived exertion, and maximal watts cycled. Participants also performed isokinetic knee flexion and extension on a dynamometer to assess peak torque, total work, work fatigue, and power. RESULTS: There were no statistical differences in single-leg aerobic capacity or strength outcomes between the injured and uninjured legs. CONCLUSIONS: Individuals who have had an ACL surgically repaired six to 18 months after return to play do not appear to have aerobic capacity or strength deficits between the injured leg and uninjured leg.

Use of the normalcy index for the assessment of abnormal gait in the anterior cruciate ligament deficiency combined with meniscus injury.

The normalcy index (NI) has been implemented by several studies as a simple index for quantitatively analyzing diffident gait abnormalities, such as children with cerebral palsy and idiopathic toe-walkers. However, whether the NI can be used in anterior cruciate ligament (ACL) deficiency with different types of meniscus injuries or not, has not been reported yet. In this study, 25 patients who combined different types of ACL and meniscus injuries were evaluated by the NI analysis. 12 healthy subjects were used to define the normal range of NI. The result showed that NI values of patients were significantly larger than the control group (P < 0.05). Meanwhile, the tendency of increasing NI values associated with increasing pathology were significant with only 5 subjects in the smallest group (Jonkheere-Terpsta test: P < 0.001). These results indicated that the NI was a concise yet effective tool to evaluate combined ACL and meniscus injury patients. Increasing severity degree of meniscus tears in ACL rupture patients is corresponded to increasing NI values. It also demonstrates that the proposed NI can be applied as a robustness factor to detect the discrepancy between healthy and patient subjects clinically, and has the potential in the quantitative evaluation of pre- or post-surgery and rehabilitation.

Early clinical and neuromuscular properties in patients with normal or sub-normal subjective knee function after anterior cruciate ligament reconstruction.

PURPOSE: To determine clinical and neuromuscular properties in patients with normal or sub-normal subjective knee function after finalisation of 6 months' post-operative rehabilitation following anterior cruciate ligament reconstruction (ACLR). METHODS: Sixty patients after primary anatomical single-bundle hamstring ACLR were prospectively enrolled. Demographics, subjective, clinical and functional status of the injured knee were recorded at baseline, 6 and 12 months post-operatively. Return to pre-injury activities time (months) was monitored. Tensiomyography and isokinetic dynamometry of thigh muscles were performed at 6 months, when standard ACLR rehabilitation is finalized. Based on their IKDC Subjective Knee Evaluation scores at 6 months, they were assigned into "Normal" or "Sub-normal" group. All the above measured parameters were then compared between the two groups. RESULTS: At 6 months' timeline, 21 patients (35%) perceived their knee function as "Normal", while 39 (65%) were "Sub-normal". There were no differences in clinical status between both groups, but patients in Normal group achieved higher IKDC, Lysholm, Tegner scores as well as higher single-leg hop test. They were taller, had lower body mass index and more of them achieved their preinjury level of activity at 12 months (67% vs. 33%). Tensiomyography revealed higher biceps femoris as well as semitendinosus and semimembranosus radial displacement values on the operated leg in Normal group. Isokinetic dynamometry showed significantly higher normalised peak torque and average power of knee extensor muscles. CONCLUSIONS: Patients who perceive their knee function as normal at 6 months following ACLR presented with better neuromuscular properties of the thigh muscles. Decreased hamstring stiffness seems to be the key to higher return-to-preinjury activity. Postoperative rehabilitation should be more focused on reducing hamstring stiffness in addition to improving knee extensor muscle strength. Level of evidence II (prospective cohort study).

Fibrocartilaginous metaplasia and neovascularization of the anterior cruciate ligament in patients with osteoarthritis.

INTRODUCTION: The anterior cruciate ligament (ACL) prevents the anterior translocation and medial rotation of the tibia against the femur. It is typically composed of dense regular connective tissue (DRCT), small amount of loose connective tissue, little vasculature, and few nerve endings. The objective of the current study was to evaluate the details of histological changes in ACLs of patients with clinically diagnosed osteoarthritis (OA). MATERIALS AND METHODS: The ACLs of six patients undergoing total knee replacement because of OA (OA group) were compared with 16 normal ACLs from cadavers (control). The ACLs were analyzed for tissue composition and number of blood vessels across the full length and thickness of the ligament. Percentages for areas of DRCT, fibrocartilage, degenerative tissue, and vasculature were calculated. Tissue composition and relative number of blood vessels were compared between groups. RESULTS: The proportion of DRCT to non-DRCT was significantly smaller in the OA group than the control group (p < .001); non-DRCT included degenerative connective tissue and fibrocartilage. The number of blood vessels to area was greater in the OA group than the control group (p = .002). Six of control (37.5%) and five of OA ACLs (83%) showed areas of calcification. CONCLUSIONS: These results indicate that inflammatory processes contributing to OA in the knee cause changes in the composition of the ACL that lead to destruction of collagen bundles, increased vascularization, calcification, and formation of fibrocartilage-like tissue inside the ligament. These changes make ligament-retaining total knee arthroplasty a less beneficial option for knee repair.