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Purpose: To report the incidence of posterior medial meniscocapsular junction (PMCJ) separation in patients with anterior cruciate ligament (ACL) injury and to evaluate its biomechanical effect on the ACL., Methods: Three hundred thirty-seven consecutive patients undergoing isolated primary ACL reconstruction were retrospectively analyzed for PMCJ lesion. Forty-four patients were identified with PMCJ lesion and studied. Eight cadaver knees underwent biomechanical testing to determine anterior tibial displacement and anteromedial bundle ACL strain in the intact, PMCJ lesion, and PMCJ repair states at 0°, 30°, 60°, and 90° of flexion. Mixed-effects linear regression with Bonferroni correction was used for statistical analysis., Results: PMCJ tear incidence with ACL disruption was 13.1%. Specimen with PMCJ tears had statistically increased anterior tibial translation at 30° (1.2 mm; P < 0.01) and statistically increased ACL strain at 30° (24%; P < 0.01) and 90° (50%; P < 0.01). With PMCJ repair, translation reduced (P > 0.05) by 12%, 18%, and 10% at 0°, 30°, and 90° of flexion, respectively. PMCJ repair reduced (P < 0.05) ACL strain by 40%, 39%, 43%, and 31% at 0°, 30°, 60°, and 90° of flexion, respectively., Conclusions: A PMCJ lesion was observed in 13% of ACL injuries. This injury contributes to increased ACL strain, and PMCJ repair markedly reduces ACL strain to preinjury levels.

Background: It is very important to dynamically evaluate the functional outcome in the knee after anterior cruciate ligament (ACL) reconstruction under physiological weight bearing. The objective of the current study is that we would like to compare the patellofemoral joint kinematics in three ACL status: ACL intact, ACL deficiency, ACL reconstruction., Methods: Twenty patients with unilateral ACL deficient knees were recruited as preoperative group. Six months after ACL reconstruction, these ten subjects were included as postoperative subjects. Ten normal subjects with healthy knees as the control group. Each subject was asked to walk up a custom set of stairs and a single-plane fluoroscopic imaging system was used to determine the 6DOF kinematics of the injured knees, ACL reconstructed knees, and intact knees., Results: ACL deficient knees showed reduced patellar flexion angle and reduced distal patellar translation during knee flexion. ACL reconstructed knees showed abnormal patellofemoral joint kinematics compared to ACL intact and ACL deficient knees, exhibiting increased patellar external rotation, lateral tilt, lateral translation during knee flexion., Conclusion: These findings imply that some alterations persist after ACL deficiency and ACL reconstruction. These abnormal changes will be the onset of degeneration in patellofemoral joint even if the ACL is reconstructed in a way that restores the clinical anteroposterior stability of the knee. Some biomechanical changes should be made to improve the outcome of intervention especially in surgical treatment like ACL reconstruction.

Low amplitude mechanical noise vibration has been shown to improve somatosensory acuity in various clinical groups with comparable deficiencies through a phenomenon known as Stochastic Resonance (SR). This technology showed promising outcomes in improving somatosensory acuity in other clinical patients (e.g., Parkinson's disease and osteoarthritis). Some degree of chronic somatosensory deficiency in the knee has been reported following anterior cruciate ligament (ACL) reconstruction surgery. In this study, the effect of the SR phenomenon on improving knee somatosensory acuity (proprioception and kinesthesia) in female ACL reconstructed (ACLR) participants (n = 19) was tested at three months post-surgery, and the results were compared to healthy controls (n = 28). Proprioception was quantified by the measure of joint position sense (JPS) and kinesthesia with the threshold to detection of passive movement (TDPM). The results based on the statistical analysis demonstrated an overall difference between the somatosensory acuity in the ACLR limb compared to healthy controls (p = 0.007). A larger TDPM was observed in the ACLR limb compared to the healthy controls (p = 0.002). However, the JPS between the ACLR and healthy limbs were not statistically significantly different (p = 0.365). SR significantly improved JPS (p = 0.006) while the effect was more pronounced in the ACLR cohort. The effect on the TDPM did not reach statistical significance (p = 0.681) in either group. In conclusion, deficient kinesthesia in the ACLR limb was observed at three months post-surgery. Also, the positive effects of SR on somatosensory acuity in the ACL reconstructed group warrant further investigation into the use of this phenomenon to improve proprioception in ACLR and healthy groups., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: The purpose of this study was to compare the biomechanical behaviour of two bioabsorbable interference screws with different geometries., Methods: Two different pitch (2.5 and 5 mm) bioabsorbable interference screws, both 9 × 30 mm, were tested. Tests were performed with forty bovine digital extensor tendons and skeletally mature porcine tibiae. Two protocols of cyclic tests at 1 Hz were performed: 1000 cycles from 50 to 250 N, and 5000 cycles from 100 to 300 N (n = 10 for each type of test and screw). After the cyclic loading, a final ramp displacement until failure at 0.5 mm/s was applied., Results: The stiffness after the cyclic phase of the tests was not statistically different between the two screws (1000th cycle: 2.5 mm pitch 280.3 ± 56.4 N/mm, 5 mm pitch 275.2 ± 65.0 N/mm, P = .965; 5000th cycle: 2.5 mm pitch 281.3 ± 66.4 N/mm, 5 mm pitch 286.1 ± 79.4 N/mm, P = .814). The yield load was not significantly different between the screws (1000 cycle tests: 2.5 mm pitch 482.2 ± 120.2 N, 5 mm pitch 495.9 ± 131.3 N, P = .508; 5000 cycle tests: 2.5 mm pitch 476.4 ± 65.3 N, 5 mm pitch 494.3 ± 39.2 N, P = .391). No correlation was found between the insertion torque and yield load (1000 cycle tests, R 2  = 0.013; 5000 cycle tests, R 2  = 0.006)., Conclusions: The pitch of bioabsorbable interference screws does not seem to affect fixation strength. Also, the authors recommend not to use insertion torque alone to estimate the fixation strength.

Background: The observational cohort study investigated whether the flexor muscles peak torque (PT) angle shifting towards extension observed in the involved knee in patients after anterior cruciate ligament reconstruction (ACLR) using semitendinosus and gracilis tendon (STGR) autograft is associated with the postoperative physiotherapy supervision duration., Methods: From 230 ACL-reconstructed males, we identified patients after ACLR utilizing STGR autograft and divided them into those who completed supervised physiotherapy <6 months (Group I; n = 77) and those who completed supervised physiotherapy ≥6 months (Group II; n = 66). The mean follow-up time was 6.84 ± 1.47 months. The ACL-reconstructed patients were compared to 98 controls (Group III). Bilateral knee flexor muscle PT measurements were performed. The relative PT at 180°/s (RPT), PT angle at 180°/s, and range of motion at 180°/s were analysed. The RPT limb symmetry index (LSI) was calculated. Tests for dependent samples, one-way analysis of variance, post hoc test, and linear Pearson's correlation coefficient (r) calculations were performed., Results: The shift towards extension was noted when comparing the ACL-reconstructed limb to the uninvolved limb (Group I, p ≤ 0.001; Group II, p ≤ 0.001) and to Group III (p ≤ 0.001), but it was not correlated with physiotherapy supervision duration (r = -0.037, p = 0.662). In ACL-reconstructed patients, there was a moderate association of supervision duration and knee flexor LSI (r = 0.587, p < 0.001)., Conclusions: The ACL-reconstructed knee flexors PT angle shift towards extension was observed regardless of the duration of postoperative physiotherapy supervision. However, the analysis revealed that the duration of supervised physiotherapy positively influenced the RPT and LSI in patients after the ACLR., Competing Interests: The authors have declared that no competing interests exist.

Purpose: To investigate the changes in landing biomechanics over a 3-year period and their correlation with cartilage degenerative changes in the medial tibiofemoral joint of the knee after anterior cruciate ligament reconstruction (ACLR) using magnetic resonance T1ρ mapping., Methods: Thirty-one anterior cruciate ligament-injured patients underwent magnetic resonance imaging of the injured knee before ACLR and 3 years after ACLR, as well as biomechanical analysis of a drop-landing task at 6 months and 3 years after ACLR. Sixteen healthy individuals were recruited and underwent knee magnetic resonance imaging and biomechanical assessment during a drop-landing task. T1ρ cartilage relaxation times were calculated for the medial femur and tibia., Results: ACLR patients exhibited increased peak vertical ground reaction force (VGRF), VGRF impulse, peak knee flexion moment (KFM), and KFM impulse from 6 months to 3 years (P < .001 for each). Although the ACLR knees showed significantly lower peak VGRF and KFM at 6 months (P < .001 for both) when compared with the controls, there were no significant differences at 3 years. At 3 years, ACLR patients showed higher T1ρ values over the medial femur (P < .001) and tibia (P = .012) when compared with their preoperative values and with healthy control values. Within the ACLR group, side-to-side differences in peak VGRF and sagittal knee biomechanics at 6 months were associated with increased T1ρ values from baseline to 3 years., Conclusions: The results of this longitudinal study show that landing biomechanics are altered after ACLR but biomechanical abnormalities tend to recover at 3 years after ACLR. Differences in lower-extremity mechanics during a landing task at 6 months may be associated with cartilage degeneration at 3 years after anterior cruciate ligament injury and reconstruction., Level of Evidence: Level II, prospective trial., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: Prevalence of knee osteoarthritis increases because life expectancy continues to rise with an active patient population. Hence, the concept of unicompartmental knee arthroplasty (UKA) has regained popularity as a treatment option for unicompartmental knee osteoarthritis. Anterior cruciate ligament (ACL) deficiency is widely considered as a contraindication for UKA, however, there are conflicting reports. If otherwise indicated, some surgeons consider UKA for ACL-deficient patients using a modified surgical technique, with a reduction of posterior tibial slope., Research Question: The purpose of this study was to evaluate outcomes in UKA patients with ACL deficiency in comparison to a conventional UKA group (intact ACL) by the measurement of knee kinematics and kinetics., Methods: Ten patients with conventional UKA and an intact ACL and eight patients with an ACL-deficient UKA and a reduced posterior tibial slope relative to the native knee were recruited. Three-dimensional joint kinematics of the knee were measured, using skin markers and an infrared optical motion capture system. Ground reaction forces (GRF) were measured with force plates in all three directions. Level walking, ramp descent and stair descent were analyzed, comparing implanted and contralateral native knees and the two UKA groups., Results: No significant differences in kinetics and kinematics were observed between conventional UKA and ACL-deficient UKA groups for any of the activities. However, some asymmetries in GRF between the implanted and contralateral side were present for the ACL-deficient group, during level walking (unloading rate) and stair descent (stance time)., Significance: Promising outcomes of the ACL-deficient UKA group suggest that ACL deficiency may not always be a contraindication. Therefore, ACL-deficient UKA could be an alternative treatment option to total knee arthroplasty for an appropriate surgeon selected patient population., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Several investigations have studied gait variability of individuals with anterior cruciate ligament (ACL) deficiency; however, the effect of dual-tasking on the gait variability of these individuals remained unclear. The aim of the present study was to determine the effect of gait speed and dual-tasking on knee flexion-extension variability in subjects with and without ACL deficiency., Methods: The knee flexion-extension Lyapunov exponent (LyE) was measured in 22 ACL-deficient (Mean±SD) (25.95 ± 4.69 years) and 22 healthy subjects (24.18 ± 3.32 years). They walked at three levels of gait speed in isolation or concurrently with a cognitive task., Results: Repeated-measure analyses of variance (ANOVAs) demonstrated that the interaction of group by gait speed was statistically significant. As the gait speed increased from low to high, the knee flexion-extension LyE significantly decreased for the subjects with ACL deficiency (effect size: 0.57, P = 0.01). The interaction of group by cognitive load was not statistically significant (P = 0.07). In addition, the ACL-deficient subjects had statistically slower reaction times than healthy subjects during the dual-task compared with the single-task condition., Conclusions: The ACL-deficient and healthy individuals had a tendency to maintain safe gait. It seems that the ACL-deficient subjects sacrificed the cognitive task more than the healthy individuals to pay more attention toward gait. Additionally, it seems that the gait speed was more challenging than cognitive load on the stride-to-stride variability in the individuals with ACL deficiency., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: The aim of the present study was to evaluate the relationship between tibial slope angle and ligament strain during in vitro landing simulations that induce ACL failure through the application of variable external loading at the knee. The hypothesis tested was that steeper posterior tibial slope angle would be associated with higher ACL strain during a simulated landing task across all external loading conditions., Methods: Kinetics previously derived from an in vivo cohort performing drop landings were reproduced on 45 cadaveric knees via the mechanical impact simulator. MRIs were taken of each specimen and used to calculate medial compartment posterior tibial slope, lateral compartment posterior tibial slope, and coronal plane tibial slope. Linear regression analyses were performed between these angles and ACL strain to determine whether tibial slope was a predictive factor for ACL strain., Findings: Medial and lateral posterior tibial slope were predictive factors for ACL strain during some landings with higher combined loads. Medial posterior slope was more predictive of ACL strain in most landings for male specimens, while lateral posterior and coronal slope were more predictive in female specimens, but primarily when high abduction moments were applied., Interpretation: Tibial slope has the potential to influence ACL strain during landing, especially when large abduction moments are present at the knee. Deleterious external loads to the ACL increase the correlation between tibial slope and ACL strain, which indicates that tibial slope angles are an additive factor for athletes apt to generate large out-of-plane knee moments during landing tasks., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Some types of meniscus tear, especially lateral meniscus tear, have been reported to be associated with rotatory knee laxity. However, precise information regarding the effect of meniscus repair on rotatory laxity is limited. The purpose of this study was to investigate the effects of lateral and medial meniscus repair on rotatory laxity in anterior cruciate ligament (ACL) injured knees., Methods: Forty-one patients who underwent ACL reconstruction were included in the study. The tibial acceleration during the pivot shift test was measured using a triaxial accelerometer preoperatively under anesthesia and intraoperatively before and after medial and lateral meniscus repair and ACL reconstruction during surgery. Effects of meniscus tear and its repair on rotatory laxity were analyzed., Results: Preoperative measurements revealed that patients with lateral meniscus tear showed significantly higher tibial acceleration compared to the patients without meniscus tear (P = 0.006). Intraoperative measurements revealed that medial and lateral meniscus repair significantly reduced tibial acceleration by 1.46 m/s 2 (P = 0.002) and 1.91 m/s 2 (P < 0.001), respectively., Conclusion: In ACL injured knees, knees with lateral meniscus tear showed greater rotatory laxity compared to the knees without meniscus tear. In addition, lateral meniscus repair, and to a lesser degree medial meniscus repair, reduced rotatory laxity during ACL reconstruction surgery. Therefore, the meniscus should be repaired as much as possible for its role as a secondary stabilizer of rotatory laxity. Besides, the effect of meniscus repair on rotatory laxity should be considered when the indication of anterolateral augmentation is determined., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Purpose: To reveal the effects of the positional and length relationships between the interference screws (ISs) and the tendon graft in the bone tunnel on the fixation strength in ligament reconstruction., Methods: We compared three IS positions on the anterior (the Anterior group) or posterior (the Posterior group) or side (the Side group) of the tendon graft in relation to the pullout direction. The tendon graft was pulled at 0°, 30°, 60°, and 90° to the bone tunnel, and the maximum pullout load at each angle was compared among the groups. We also investigated the relationship between the length of the tendon graft and the length of the IS in the bone tunnel. The direction of the pullout force was the same as that of the Anterior group, and the maximum load was compared between groups in which the tendon graft was longer or shorter than the IS., Results: The maximum loads of the Anterior group were significantly greater than those of the Posterior and Side groups at the traction angles of 30° and 60°, respectively. An IS shorter than the tendon graft was found to provide significantly superior fixation strength compared to an IS longer than the tendon graft., Conclusions: Better fixation strength was achieved when the IS was placed on the side of the anchorage tunnel on which the tendon graft was loaded and the IS was shorter than the tendon graft.

Background: Research has indicated that a smaller intercondylar notch could cause contact between the anterior cruciate ligament and the femoral notch, which may predispose individuals to an increased rate of anterior cruciate ligament injury., Hypothesis: Contact between the lateral notch wall and the anterior cruciate ligament does increase the strain past the structural integrity of the ligament., Study Design: A descriptive laboratory study., Methods: A biomechanical study using robotic manipulators was conducted to investigate the occurrence of impingement in human cadaver specimens. Six cadaveric knees from six donors (three male and three female) were instrumented with a thin force sensor, placed on the lateral wall of the femoral condyle, and a differential variable reluctance transducer (DVRT) was attached to the middle section of the anterior medial bundle of the ACL. The knees were then moved through a series of flexion (5° to 90°), valgus (0 to 7.5°), and external rotation (0 to 7.5°) movements using two interacting robots., Results: The results revealed that impingement occurred in both male and female specimens with a maximum impingement force of 28 N. Impingement occurred more prominently in female knees and in the combination loading of valgus and external rotation for both genders. The corresponding strain due to impingement was small or compressive, with the male knee maximum strain less than 1.28% and the female knee strain less than 7.1% in the worse case conditions., Conclusion: The lack of increased force or strain when impingement occurred indicates that impingement may not affect the healthy function of the knee with a nonstenotic notch. Additionally, the analysis shows that impingement may not be a major contributing factor to anterior cruciate ligament injury, but rather a common occurrence in healthy knees., Clinical Relevance: Impingement within the femoral notch does not appear to be a major contributory factor to ACL injury. Other more severe injuries to the knee would occur before ACL impingement with the femoral notch becoming a contributing factor to ACL injury. The small sample size limits the conclusivity of the results presented in this research; thus, additional large sample size studies are warranted.

Purpose: Anterior cruciate ligament (ACL) repair was first described in the mid 1900's. However, due to poorly selected patients led to unsatisfactory early results. We aim to study the outcome of ACL repair in a carefully selected cohort., Methods: Thirteen consecutive patients of acute Type 1 (proximal ACL avulsion) were treated with arthroscopic ACL repair using a suture pull out technique. At the latest follow-up the patients were evaluated for Lysholm score, KT-1000 measurement and clinical assessment for any laxity., Results: At a mean follow-up of 31.3 months, none of the patients had any subjective laxity. The mean Lysholm score was 95 and instrumented laxity measurement did not reveal any significant laxity compared to the opposite knee., Conclusion: The proximal ACL avulsion has healing potential similar to proximal MCL injuries. Performing microfracture of the lateral wall of the notch optimizes the healing environment by negating the effects of the synovial fluid. Performing ACL repair in a carefully selected patient leads to good short term results and saves the patient of a reconstruction procedure, at least in the immediate future., (Copyright © 2018 Daping Hospital and the Research Institute of Surgery of the Third Military Medical University. Production and hosting by Elsevier B.V. All rights reserved.)

The sensorimotor system helps to maintain functional joint stability during movement. After anterior cruciate ligament (ACL) injury and reconstruction, several sensorimotor deficits may arise, including altered proprioception and changes in neuromuscular control. It is still unknown whether the type of autograft used in the reconstruction may influence knee sensorimotor impairments. The aim of this study was to comparatively assess the effects of the hamstring tendon (HT) and bone-patellar tendon-bone (BPTB) ACL reconstruction techniques on knee sensorimotor control 6-12 months post-operation. A total of 83 male subjects participated in this study: 27 healthy participants, 30 BPTB-operated patients and 26 HT-operated patients. Active joint position sense in 3 ranges of motion (90-60°, 60-30°, and 30-0° of knee flexion), isometric steadiness, and onset of muscle activation were used to compare sensorimotor system function between groups. Both operated groups had a small (< 5°) but significant joint position sense error in the 30-0° range when compared to the healthy group. No significant differences were found between the operated and the control groups for isometric steadiness or onset of muscle activation. The results of this study suggest that operated patients present knee proprioceptive deficits independently of surgical technique. Nevertheless, the clinical implications of this impairment are still unknown. It seems that selected surgical approach for ACL reconstruction do not affect functioning of the sensorimotor system to a large degree., Competing Interests: The authors have the following interests. Cristóbal San Martín-Mohr, Iver Cristi-Sánchez and Claudio Oyarzo are employed by Clínica MEDS. There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Purpose: To evaluate the effect of ACL deficiency on the in vivo changes in end-to-end distances and to determine appropriate graft fixation angles for commonly used tunnel positions in contemporary ACL reconstruction techniques., Methods: Twenty-one patients with unilateral ACL-deficient and intact contralateral knees were included. Each knee was studied using a combined magnetic resonance and dual fluoroscopic imaging technique while the patients performed a dynamic step-up motion (~50° of flexion to extension). The end-to-end distances of the centers of the anatomic anteromedial (AM), posterolateral (PL) and single-bundle ACL reconstruction (SB-anatomic) tunnel positions were simulated and analyzed. Comparisons were made between the elongation patterns between the intact and ACL-deficient knees. Additionally, a maximum graft length change of 6% was used to calculate the deepest flexion fixation angle., Results: ACL-deficient knees had significantly longer graft lengths when compared with the intact knees for all studied tunnel positions (p < 0.01). The end-to-end distances for the AM, PL and SB-anatomic grafts were significantly longer between 0-30° of flexion when compared with the intact knee by p < 0.05 for all. Six percent length change occurred with fixation of the AM bundle at 30° of flexion, PL bundle at 10° and the SB-anatomic graft at 20°., Conclusions: ACL-deficient knees had significantly longer in vivo end-to-end distances between 0°-30° of flexion for grafts at the AM, PL and SB-anatomic tunnel positions when compared with the intact knees. Graft fixation angles of <30° for the AM, <10° for the PL, and <20° for the SB-anatomic grafts may prevent permanent graft stretch., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Purpose: Several non-invasive devices have been developed to obtain quantitative assessment of the pivot-shift test in clinical setting using similar but diverse measurement parameters. However, the clinical usability of those measurements has yet to be closely investigated and compared. The purpose of this study was to compare the diagnostic accuracy of three non-invasive measurement devices for the pivot-shift test., Methods: Thirty patients with unilateral anterior cruciate ligament (ACL) injury were enrolled. The pivot-shift test was performed under general anaesthesia. Three devices, an accelerometer system (KiRA), an image analysis iPad application (iPad), and electromagnetic measurement system (EMS), were used simultaneously to provide two parameters, namely tibial acceleration monitored using KiRA and EMS, and tibial translation recorded using iPad and EMS. Side-to-side differences in each parameter and correlation between the measurements were tested, and a receiver-operating characteristic (ROC) curve analysis was conducted to compare their measurement accuracy., Results: Significant side-to-side differences were successfully detected using any of the measurements (all p < 0.01). KiRA demonstrated moderate correlation with the EMS for tibial acceleration (r = 0.54; p < 0.01), while poor correlation was observed between iPad and the EMS for the translation (r = 0.28; p < 0.01). The ROC curve analysis demonstrated better accuracy for the detection of ACL insufficiency in the EMS than KiRA and iPad for tibial acceleration and translation, respectively., Conclusions: Although all three measurements were similarly capable of detecting ACL deficiency, the EMS has the advantage of comprehensive evaluation of the pivot-shift test by evaluating both tibial acceleration and translation with higher accuracy than those of KiRA and iPad. It could be suggested that any of those measurement tools might improve the clinical diagnosis of ACL insufficiency., Level of Evidence: Diagnostic study of consecutive patients with a universally applied gold standard, Level Ib.

Management of anterior cruciate ligament (ACL) injuries in adults aged >40 years has received increased attention in the literature because of an increase in the functional demands of aging athletes. Multiple structural and biomechanical age-dependent changes exist in the ACL, for example, fewer mesenchymal stem cells, decreased healing potential, decreased structural organization, decreased stiffness, and a decreased load to failure with age. As in younger patients, ACL insufficiency can predispose an older patient to the same risks of recurrent instability, meniscal and chondral injury, and osteoarthritis. The role of nonsurgical versus surgical management in these patients remains controversial. Lower-demand patients may be able to cope with ACL deficiency. Higher-demand patients may have functional instability, and the limited studies available suggest good functional outcomes with surgical reconstruction of the ACL in this population.

Purpose: To investigate whether an increased magnitude of quantitative rotatory knee laxity is associated with a greater level of generalized joint laxity in ACL-injured and contralateral knees., Methods: A total of 103 patients were enrolled across four international centers to undergo anatomic ACL reconstruction. Rotatory knee laxity was evaluated preoperatively, both in the awake state and under anesthesia, using the standardized pivot shift test. Two devices were used to quantify rotatory knee laxity; an inertial sensor, measuring the joint acceleration, and an image analysis system, measuring the lateral compartment translation of the tibia. The presence of generalized joint laxity was determined using the Beighton Hypermobility Score. The correlation between the level of generalized joint laxity and the magnitude of rotatory knee laxity was calculated for both the involved knee and the non-involved knee. Further, patients were dichotomized into low (0-4) or high (5-9) Beighton Score groups. Alpha was set at < 0.05., Results: Ninety-six patients had complete datasets, 83 and 13 in the low and high Beighton Score groups respectively. In anesthetized patients, there was a significant correlation between the degree of Beighton Score and quantitative pivot shift when analyzing the non-involved knee using the image analysis system (r = 0.235, p < 0.05). When analyzing the same knee, multivariate analysis adjusted for meniscal injury, age and gender revealed an increased odds ratio for patients with increased lateral compartment translation to be part of the high Beighton Score group (OR 1.86, 95% CI 1.10-3.17, p < 0.05). No other correlation was significant. When analyzing the dichotomized subgroups, no significant correlations could be established., Conclusion: The findings in this study suggest that there is a weak correlation between generalized joint laxity and the contralateral healthy knee, indicating increased rotatory knee laxity in these patients. Generalized joint laxity does not appear to correlate with rotatory knee laxity in ACL-injured knees., Level of Evidence: Prospective cohort study; level of evidence, 2.

Background: Sex-related neuromuscular differences have been linked to greater risk of anterior cruciate ligament injuries in females. Despite this, it remains unclear if sex-related differences are present after injury. This study sought to determine if sex differences are present in the functional roles of knee joint muscles in an anterior cruciate ligament deficient population., Methods: An isometric, weight-bearing, force-generation protocol required injured and healthy males and females to modulate ground reaction forces. Electromyography was used to classify the functional role of 10 lower limb muscles in their contribution to knee joint stability during various loading directions. These roles were compared between the four groups at 12 loading directions using a directional analysis., Findings: Functional muscle roles were different between groups, except for injured males and healthy females. Healthy males had either joint actuators or specific joint stabilisers, but no general stabilisers; the vastus medialis and lateralis of injured males and healthy females were classified as general stabilisers while injured females added the gluteus medialis and medial gastrocnemius as general stabilisers., Interpretation: A population-based hierarchy in functional muscle roles was discovered. Healthy males demonstrated the most specific muscle roles, which can be viewed as more adaptive to variable loading conditions. The more generalised stabilisation strategies seen in injured males and females would alter joint loading which may be detrimental to the knee joint health over time. In summary, (1) these injuries alter muscle roles; (2) these alterations are sex-specific; (3) rehabilitation might be optimised if sex-differences are considered., (Copyright © 2018. Published by Elsevier Ltd.)

Background: Hamstring tendon autografts and soft-tissue allograft are commonly used for anterior cruciate ligament (ACL) reconstruction. However, the clinical outcomes between these two grafts are controversial. This meta-analysis was performed to compare clinical outcomes of primary ACL reconstruction with hamstring tendon autografts versus soft-tissue allografts., Materials and Methods: PubMed, Embase, and the Cochrane Library were searched through 8 September 2017 to identify randomized controlled studies that compared hamstring tendon autografts with soft-tissue allografts for primary ACL reconstruction. Two authors independently graded the methodological quality of each eligible study using the Cochrane Collaboration tool and extracted relevant data. Statistical heterogeneity among the trials was evaluated with chi-square and I-square tests. A sensitivity analysis was conducted to explore sources of heterogeneity. Subgroup analysis was performed to identify potential differences according to type of reconstruction technique (single-bundle or double-bundle)., Results: Eight studies with 785 combined patients (396 hamstring tendon autografts and 389 soft-tissue allografts) were included. Two studies had a high risk of bias. The other six studies had unclear risk of bias. There were significant differences between the groups in subjective International Knee Documentation Committee (IKDC) score (mean difference [MD], 2.43; 95%CI, 0.69-4.18; p = 0.006), Tegner score (MD, 0.24; 95%CI, 0.03-0.45; p = 0.03), and side-to-side difference (MD, -1.37; 95%CI, -2.44 to -0.30; p = 0.01). There was no significant difference between the groups in Lysholm score, complications, pivot shift test, anterior drawer test, Lachman test, overall IKDC score, or range of motion. Subgroup analysis demonstrated that for primary ACL reconstruction using the single-bundle technique, soft-tissue allografts were inferior to hamstring tendon autografts in subjective IKDC score, anterior drawer test, and side-to-side difference., Conclusion: Soft-tissue allografts are inferior to hamstring tendon autografts with respect to subjective patient evaluation and knee stability but superior in the complication of hypoesthesia for patients undergoing primary ACL reconstruction., (Copyright © 2018 IJS Publishing Group Ltd. Published by Elsevier Ltd. All rights reserved.)

Background: Combined rupture of the anterior cruciate ligament (ACL) and patellar tendon (PT) is a rare injury pattern. Currently, little evidence exists to help guide management decisions for these patients., Methods: A systematic literature search was conducted using PubMed (MEDLINE) and Scopus (EMBASE and MEDLINE) for all articles reporting on combined rupture of the ACL and PT. The characteristic injury mechanisms, common presentation findings, and outcomes of simultaneous and staged treatment strategies were determined to provide guidance for the management of this uncommon injury pattern. An additional case report from our institution is also reported., Results: Overall, 17 studies met the inclusion criteria and were included in our qualitative review. The mean age at injury was 30 years (range, 15-50 years). A high-energy injury with a rapid deceleration event through a flexed knee on a fixed foot is commonly described as the mechanism of injury. Anterior cruciate ligament rupture was missed on initial clinical examination in 24.1% compared with 17.2% for PT rupture. Injuries to the medial collateral ligament and menisci occured in 65.5% of cases. Outcome scores were reported in 41.4% (12/22) of patients undergoing staged or simultaneous repair. The Lysholm score postoperatively was 96 ± 3.3 for the staged group compared with 85.3 ± 18.6 for simultaneous repair. There were no clear differences between range of motion, time to return to sport, and complication rates between the groups., Conclusions: A high index of suspicion is required to detect concomitant ACL injuries when assessing high-energy PT ruptures. Simultaneous or staged protocols to address both injuries are safe and effective management strategies for this rare combined injury pattern., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Purpose: Cross-education reduces quadriceps weakness 8 weeks after anterior cruciate ligament (ACL) surgery, but the long-term effects are unknown. We investigated whether cross-education, as an adjuvant to the standard rehabilitation, would accelerate recovery of quadriceps strength and neuromuscular function up to 26 weeks post-surgery., Methods: Group allocation was randomized. The experimental (n = 22) and control (n = 21) group received standard rehabilitation. In addition, the experimental group strength trained the quadriceps of the non-injured leg in weeks 1-12 post-surgery (i.e., cross-education). Primary and secondary outcomes were measured in both legs 29 ± 23 days prior to surgery and at 5, 12, and 26 weeks post-surgery., Results: The primary outcome showed time and cross-education effects. Maximal quadriceps strength in the reconstructed leg decreased 35% and 12% at, respectively, 5 and 12 weeks post-surgery and improved 11% at 26 weeks post-surgery, where strength of the non-injured leg showed a gradual increase post-surgery up to 14% (all p ≤ 0.015). Limb symmetry deteriorated 9-10% more for the experimental than control group at 5 and 12 weeks post-surgery (both p ≤ 0.030). One of 34 secondary outcomes revealed a cross-education effect: Voluntary quadriceps activation of the reconstructed leg was 6% reduced for the experimental vs. control group at 12 weeks post-surgery (p = 0.023). Both legs improved force control (22-34%) and dynamic balance (6-7%) at 26 weeks post-surgery (all p ≤ 0.043). Knee joint proprioception and static balance remained unchanged., Conclusion: Standard rehabilitation improved maximal quadriceps strength, force control, and dynamic balance in both legs relative to pre-surgery but adding cross-education did not accelerate recovery following ACL reconstruction.

Medial unicompartmental knee arthroplasty (UKA) is an accepted treatment for isolated medial osteoarthritis. However, using an improper thickness for the tibial component may contribute to early failure of the prosthesis or disease progression in the unreplaced lateral compartment. Little is known of the effect of insert thickness on both knee kinematics and ligament forces. Therefore, a computational model of the tibiofemoral joint was used to determine how non-conforming, fixed bearing medial UKA affects tibiofemoral kinematics, and tension in the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) during passive knee flexion. Fixed bearing medial UKA could not maintain the medial pivoting that occurred in the intact knee from 0° to 30° of passive flexion. Abnormal anterior-posterior (AP) translations of the femoral condyles relative to the tibia delayed coupled internal tibial rotation, which occurred in the intact knee from 0° to 30° of flexion, but occurred from 30° to 90° of flexion following UKA. Increasing or decreasing tibial insert thickness following medial UKA also failed to restore the medial pivoting behavior of the intact knee despite modulating MCL and ACL forces. Reduced AP constraint in non-conforming medial UKA relative to the intact knee leads to abnormal condylar translations regardless of insert thickness even with intact cruciate and collateral ligaments. This finding suggests that the conformity of the medial compartment as driven by the medial meniscus and articular morphology plays an important role in controlling AP condylar translations in the intact tibiofemoral joint during passive flexion. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1868-1875, 2018., (© 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

Knee laxity may be impacted by rupture of the anterolateral knee ligament (ALL). The goal of this study was to measure tibial translation and rotation as a function of the status of the ALL and the anterior cruciate ligament (ACL). Five pairs of fresh frozen cadaver specimens were analyzed. The knee was positioned in 20° flexion. Calibrated posteroanterior forces and internal/external torques were successively applied. Anterior tibial translation and total internal/external tibial rotation were measured with a navigation system. Three conditions were used in each knee: intact ACL and ALL, transection of ACL or ALL (randomly assigned to each knee of a pair), and transection of both ligaments. The primary outcome criterion was the increase in tibial rotation at 8 Nm. The mean increase in tibial rotation at 8 Nm was 0.8° after transecting the ALL only, 1.2° after transecting the ACL only, and 0.8° after transecting both ligaments. The mean increase in anterior tibial translation at 250 N was 1.2 mm after transecting the ALL only, 9.0 mm after transecting the ACL only, and 6.1 mm after transecting both ligaments. There was no significant increase in the tibial rotation or anterior tibial translation after transecting the ALL only or after transecting the ALL in ACL-deficient knees. The expected role of ALL in controlling anterior or rotational tibia motion could not be confirmed.

Comparing to primary surgery, revision ACL reconstruction is more technically demanding and has a higher failure rate. Theoretically, rehabilitation can improve knee function after ACL reconstruction surgery. This study aimed to compare knee stability, strength, and function between primary and revision ACL reconstructed knees. 40 primary and 40 revision ACL reconstruction surgeries were included between April 2013 and May 2016. Patients with revision surgery had a higher anteroposterior translation comparing those with primary reconstruction (median laxity, 2.0 mm vs. 3.0 mm, p = 0.0022). No differences were noted in knee extensor at 60°/sec or 180°/sec (p = 0.308, p = 0.931, respectively) or in flexor muscle strength at 60°/sec or 180°/sec between primary and revision ACL reconstruction knees (p = 0.091, p = 0.343, respectively). There were also no significant differences between functional scores including IKDC score and Lysholm score in primary versus revision surgeries at 12th months after index operation (p = 0.154, p = 0.324, respectively). In conclusion, despite having higher anteroposterior instability, patients with revision ACL reconstruction can have non-inferior outcomes in isokinetic knee strength and function compared to those with primary ACL reconstruction after proper rehabilitation.

Our previous studies used tibial compression overload to induce anterior cruciate ligament (ACL) rupture in mice, while others have applied similar or greater compressive magnitudes without injury. The causes of these differences in injury threshold are not known. In this study, we compared knee injury thresholds using a "prone configuration" and a "supine configuration" that differed with respect to hip, knee, and ankle flexion, and utilized different fixtures to stabilize the knee. Right limbs of female and male C57BL/6 mice were loaded using the prone configuration, while left limbs were loaded using the supine configuration. Mice underwent progressive loading from 2 to 20 N, or cyclic loading at 9 N or 14 N (n = 9-11/sex/loading method). Progressive loading with the prone configuration resulted in ACL rupture at an average of 10.2 ± 0.9 N for females and 11.4 ± 0.7 N for males. In contrast, progressive loading with the supine configuration resulted in ACL rupture in only 36% of female mice and 50% of male mice. Cyclic loading with the prone configuration resulted in ACL rupture after 15 ± 8 cycles for females and 24 ± 27 cycles for males at 9 N, and always during the first cycle for both sexes at 14 N. In contrast, cyclic loading with the supine configuration was able to complete 1,200 cycles at 9 N without injury for both sexes, and an average of 45 ± 41 cycles for females and 49 ± 25 cycles for males at 14 N before ACL rupture. These results show that tibial compression configurations can strongly affect knee injury thresholds during loading., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The purpose of this study was to develop a magnetic resonance T 2 * relaxometry-based multiple linear regression model to predict the structural properties of the healing anterior cruciate ligament (ACL) over a 24-week healing period following ACL repair in Yucatan minipigs. Two hypotheses were tested: (i) that a regression model based on ACL sub-volumes containing short and long T 2 * relaxation times would outperform a competing model based on sub-volumes of short T 2 * relaxation times only; and (ii) that an optimized regression model would be capable of predicting ACL structural properties between 6 and 24 weeks post-repair. ACLs were imaged in 24 minipigs (8/group) at either 6, 12, or 24 weeks after ACL repair. The structural properties of the ACLs were determined from tensile failure tests. Four multiple linear regression models of increasing complexity were fitted to the data. Akaike Information Criterion values and Bland-Altman tests were used to compare model performance and to test the hypotheses. The structural properties predicted from the multiple linear regression model that was based on the change in ACL sub-volumes of both the short and long T 2 * relaxation times over the healing period were in closest agreement to the measured values, suggesting that the amounts of both organized and disorganized collagen, and the change in these quantities over time, are required to predict the structural properties of healing ACLs accurately., Clinical Significance: our time-specific, T 2 *-based regression model may allow us to estimate the structural properties of ACL repairs in vivo longitudinally. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1701-1709, 2018., (© 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

Background: Functional knee braces are extensively used for partially and completely torn anterior cruciate ligament (ACL) patients and those who have undergone ACL graft reconstruction, in order to support the healing ACL, improve the joint's functional stability, and restore the normal joint kinematics., Research Question: Does wearing braces alter the arthrokinematics of the ACL deficient knees during lung exercise?, Methods: For ten male unilateral ACL deficient subjects, 3D knee models were reconstructed from CT images, acquired in rest position. Sagittal plane fluoroscopy was then performed throughout a complete cycle of lunge in braced and non-braced conditions. The 3D kinematics of the knees were obtained using a 2D-3D registration method in which six anatomical bony landmarks on the fluoroscopic images were matched with those on the 3D models., Results: No significant difference was found between the tibial anterior-posterior translations and abduction-adduction motions of the braced and non-braced knees. A significant decrease, however, was observed after bracing in the tibial internal rotation at 45° flexion during eccentric (non-braced: 5.9° (±6.7°) vs. braced: 2.4° (±7.0°); p = 0.045), and at 30° flexion during concentric (non-braced: 2.3° (±6.9°) vs. braced: -1.6° (±8.1°); p = 0.001) phases of the lunge cycle., Significance: The immediate effect of knee bracing is limited to controlling the tibial rotation of the ACL deficient individuals during the lunge exercise. Hence, care should be taken in prescribing the lunge exercise for rehabilitation of ACL injured patients with high anterior-posterior knee instability, even when wearing knee braces., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: The effects of retaining residual bundles on surgical outcomes has not been observed, so we evaluated the effects of preoperative knee laxity on clinical outcomes after partial anterior cruciate ligament (ACL) reconstruction for partial ACL rupture in this study., Purpose: To evaluate the effects of preoperative knee laxity on clinical outcomes after partial anterior cruciate ligament (ACL) reconstruction for partial ACL rupture., Methods: The data of 47 patients, who had partial ACL rupture and underwent partial ACL reconstruction, were retrospectively analyzed. According to preoperative kneelax arthrometer and pivot shift test, the 47 patients were divided into group A (kneelax arthrometer ≤5mm and pivot shift test 5mm and/or pivot shift test ≥II grade, n=21). The minimum follow-up duration lasted 2 years. The clinical outcomes were evaluated using IKDC (International Knee Documentation Committee) scoring systems, Lysholm knee scoring scale, Tegner activity rating, Lachman test, Pivot shift test and the kneelax arthrometer., Results: The function and stability examinations for the affected knee joint were significantly improved in both groups after partial ACL reconstruction as compared with preoperative ones (all P<0.01). There were no significant differences in the post-operative Lysholm and Tegner scores, Lachman and Pivot shift test results between both groups (all P>0.05). However, there were significant differences between the two groups in terms of the post-operative IKDC scoring system and kneelax arthrometer examination result (all P<0.05)., Conclusions: In the patients with partial ACL rupture, the mechanical strength of the remnant ligament has significant influence on the therapeutic effects of partial reconstruction. The patients with kneelax arthrometer >5mm and/or pivot shift test ≥II grade still have anterior instability in the affected knee after partial reconstruction., (Copyright © 2018 Elsevier B.V. All rights reserved.)

One of the most common injuries of the knee joint is a rupture of the anterior cruciate ligament (ACL). Most authors believe that early rehabilitation of patients after ACL reconstruction promotes better treatment outcomes. Less is known about the influence of the time that passes from injury to surgical reconstruction. Therefore, the goal of this study was to assess the dependence of treatment outcomes of ACL on injury-to-reconstruction and reconstruction-to-rehabilitation time lags. The study included 30 patients of the mean age 34 ± 7 years with trauma-related rupture of ACL and its surgical reconstruction. The time range from ligament rupture to its reconstruction was 120-180 days and from reconstruction to rehabilitation was 1-120 days. Postsurgical rehabilitation outcomes were assessed with the Lysholm knee scale and the IKDC 2000 subjective knee evaluation form. The scales were applied before and after rehabilitation. We found distinct improvements in all physical symptoms in the damaged knee joint, regardless of the time elapsed from trauma to ACL reconstruction and from ACL reconstruction to rehabilitation. The beneficial outcomes of rehabilitation were significantly inversely associated with the time elapsing from reconstruction to rehabilitation commencement but failed to depend on the time from ACL rupture to reconstruction. We conclude that rehabilitation should start as early as possible after ACL reconstruction to optimize the beneficial outcomes in terms of functional physical recovery, whereas the injury-to-reconstruction delay is less meaningful to this end.

Purpose: Anterior cruciate ligament (ACL) reconstruction (ACLR) aims to restore normal knee joint function, stability and biomechanics and in the long term avoid joint degeneration. The purpose of this study is to present the anatomic single bundle (SB) ACLR that emphasizes intraoperative correction of tibiofemoral subluxation that occurs after ACL injury. It was hypothesized that this technique leads to optimal outcomes and better restoration of pathological tibiofemoral joint movement that results from ACL deficiency (ACLD)., Methods: Thirteen men with unilateral ACLD were prospectively evaluated before and at a mean follow-up of 14.9 (SD = 1.8) months after anatomic SB ACLR with bone patellar tendon bone autograft. The anatomic ACLR replicated the native ACL attachment site anatomy and graft orientation. Emphasis was placed on intraoperative correction of tibiofemoral subluxation by reducing anterior tibial translation (ATT) and internal tibial rotation. Function was measured with IKDC, Lysholm and the Tegner activity scale, ATT was measured with the KT-1000 arthrometer and tibial rotation (TR) kinematics were measured with 3Dmotion analysis during a high-demand pivoting task., Results: The results showed significantly higher TR of the ACL-deficient knee when compared to the intact knee prior to surgery (12.2° ± 3.7° and 10.7° ± 2.6° respectively, P = 0.014). Postoperatively, the ACLR knee showed significantly lower TR as compared to the ACL-deficient knee (9.6°±3.1°, P = 0.001) but no difference as compared to the control knee (n.s.). All functional scores were significantly improved and ATT was restored within normal values (P < 0.001)., Conclusions: Intraoperative correction of tibiofemoral subluxation that results after ACL injury is an important step during anatomic SB ACLR. The intraoperative correction of tibiofemoral subluxation along with the replication of native ACL anatomy results in restoration of rotational kinematics of ACLD patients to normal levels that are comparable to the control knee. These results indicate that the reestablishment of tibiofemoral alignment during ACLR may be an important step that facilitates normal knee kinematics postoperatively., Level of Evidence: Level II, prospective cohort study.

Purpose: The purpose of this study is to compare knee laxity and graft function (tissue force) between anatomic and non-anatomic posterolateral (PL) bundle augmentation., Methods: Twelve (n = 12) fresh-frozen mature, unpaired porcine knees were tested using a robotic testing system. Four knee states were compared: (a) intact anterior cruciate ligament (ACL), (b) deficient PL and intermediate bundles, (c) anatomic PL augmentation, and (d) non-anatomic PL augmentation. Anterior tibial translation (ATT), internal rotation (IR) and external rotation (ER), and the in situ tissue force were measured under an 89.0-N anterior tibial load and 4.0-N m internal and external tibial torques., Results: Both anatomic and non-anatomic PL augmentation restored the ER, IR, and ATT of the intact knee at all knee flexion angles (n.s.). Both anatomic and non-anatomic PL augmentation restored the in situ tissue force of the ACL during ER and IR loading and ATT loading at all knee flexion angles except at 60° of knee flexion, where the non-anatomic PL augmentation did not restore the in situ tissue force of the ACL during external rotation loading and the anatomic PL augmentation did not restore the in situ tissue force of the ACL during IR loading. Furthermore, there were no differences in ATT, IR, ER, and in situ tissue force under anterior tibial loading, IR and ER loading between the two reconstruction groups., Conclusion: There were no significant differences between anatomic and non-anatomic PL augmentation using the porcine knee model.

Background: Vascular CD34+ cells in anterior cruciate ligament (ACL) tissues have a potential for high proliferation and multilineage differentiation, which can accelerate tendon-bone healing after ACL reconstruction. To predict outcomes of ACL reconstruction with remnant preservation or ruptured tissue incorporation, patient characteristics should be considered. However, the influence of ACL remnant morphologic pattern on healing potential remains unknown., Hypothesis: The healing potential of ACL remnants could differ among their morphologic patterns., Study Design: Descriptive laboratory study., Methods: ACL remnant tissues were harvested from patients aged <35 years who received primary ACL reconstruction within 3 months after injury. The tissues were evaluated according to the Crain classification (4 patterns). The patterns were divided into 2 groups: the reattachment group (Crain I-III) and the nonreattachment group (Crain IV). ACL remnant cells were characterized via fluorescence-activated cell sorting. The potential for proliferation and multilineage differentiation was assessed and compared between the groups., Results: The ratio of CD34+ cells was significantly higher in the nonreattachment group than in the reattachment group. In early passages, the nonreattachment group had a significantly higher expansion potential than the reattachment group. In the evaluation of osteogenic and endothelial differentiation potential, the nonreattachment group showed a higher potential in immunohistochemical/histochemical staining and quantitative real-time polymerase chain reaction analysis as compared with the reattachment group., Conclusion: In the subacute phase, ACL remnant tissue of the nonreattachment group possibly has a higher healing potential than that of the reattachment group., Clinical Relevance: If healing potential differs among the morphologic patterns of ACL remnants, surgeons may expect the healing potential when preserving remnants.

The anterolateral structures of the knee have recently garnered considerable interest regarding their role in rotatory knee instability related to anterior cruciate ligament tears. Isolated anterior cruciate ligament reconstruction may not always restore rotatory stability of the knee. In these patients, additional procedures, such as lateral reconstruction or tenodesis, may be indicated. The anatomy of the anterolateral structures of the knee has been well described. Histologic and anatomic studies have reported conflicting findings regarding the presence of a discrete ligament. The biomechanical role of the anterolateral capsule in restraining internal tibial rotation has been described as negligible. The existing body of research on the anterolateral knee structures provides insight into the composition of the anterolateral complex of the knee.

This study aimed to investigate the biomechanical properties of anterior cruciate ligament (ACL); tibial, femoral articular cartilage; and meniscus in knee joints receiving computer-aided or conventional ACL reconstruction. Three-dimensional (3D) knee joint finite element models were established for healthy volunteers (normal group) and patients receiving computer-aided surgery (CAS) or conventional (traditional surgery [TS]) ACL reconstruction. The stress and stress distribution on the ACL, tibial, femoral articular cartilage, and meniscus were examined after force was applied on the 3D knee joint finite element models. No significant differences were observed in the stress on ACL among normal group, CAS group, and TS group when a femoral backward force was loaded. However, when a vertical force of 350 N was loaded on the knee joints, TS group had significant higher stress on the articular cartilage and meniscus than the other two groups at any flexion angle of 0, 30, 60, and 90 degrees. However, no significant differences were observed between CAS group and normal group. In conclusion, computer-aided ACL reconstruction has advantages over conventional surgery approach in restoring the biomechanical properties of knee joints, thus reducing the risk of damage to the knee joint cartilage and meniscus after ACL reconstruction., Competing Interests: None., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Background: Limited in vivo kinematic information exists on managing meniscal injury during anterior cruciate ligament reconstruction (ACLR)., Hypothesis: Isolated anatomic ACLR restores knee kinematics, whereas ACLR in the presence of medial meniscal injury is associated with altered long-term knee kinematics., Study Design: Cohort study; Level of evidence, 3., Methods: From March 2011 to December 2012, 49 of 57 participants in a clinical trial underwent anatomic ACLR with successful kinematic testing at 24 months after ACLR. Twenty-five patients had associated meniscal tears: medial (n = 11), lateral (n = 9), or bilateral (n = 5). With a dynamic stereo radiography system with superimposed high-resolution computed tomography scans of patient knees, kinematics were measured during downhill running. The initial single-support phase of the gait cycle (0%-10%) was analyzed., Results: Anterior tibial translation (ATT) was the only kinematic outcome between patients' ACLR and contralateral knees that had significant interactions among meniscal groups ( P = .007). There was significant difference in ATT between patients with intact menisci and medial tears ( P = .036) and with medial tears and lateral tears ( P = .025). Patients with intact menisci had no difference in ATT, with a negligible effect size between the ACLR and contralateral knees (mean ± SEM: 13.1 ± 0.7 mm vs 12.6 ± 0.5 mm, P = .24, Cohen d = 0.15, n = 24), while patients with medial meniscal tears had an increase in ATT, with a medium effect size between the ACLR and contralateral knees (15.4 ± 1.0 mm vs 13.2 ± 1.0 mm, P = .024, Cohen d = 0.66, n = 11)., Conclusion: Associated medial meniscal injury in the setting of ACLR leads to increased ATT at 24-month follow-up. Furthermore, isolated anatomic ACLR in the absence of meniscal injury demonstrated no significant difference from native knee kinematics at 24-month follow-up during rigorous "high demand" knee activity with the current sample size. Patients undergoing anatomic ACLR in the presence of medial meniscal injury remained at a higher likelihood of sustaining altered long-term knee kinematics.

Purpose: To evaluate the effect of progressive lesions of the anterior cruciate ligament (ACL) and anterolateral ligament (ALL) on anterior tibial translation (ATT) as evaluated through the Lachman test and internal tibial rotation (ITR) during a dynamic pivot-shift test in a cadaveric model., Methods: A total of 7 specimens were tested using a navigation system (2.2 OrthoPilot ACL navigation system). The anterior stability of the knee was measured through the Lachman test and dynamic rotational stability was measured through the pivot-shift test in 3 different conditions: intact knee; ACL-deficient knee; and finally, ACL- and ALL-deficient knee. The resulting measurements from the navigation system recorded the real-time changes in both translation and internal rotation during the Lachman and pivot-shift maneuvers., Results: Mean ATT was 7.57 ± 0.53 mm in the intact knee, 14 ± 2.44 mm in the ACL-deficient knee, and 14 ± 2.44 mm in the ACL- and ALL-deficient knee. Mean ITR during the pivot-shift test was 10.14° ± 2.26° in the intact knee, 12.14° ± 2.19° in the ACL-deficient knee, and 18.86° ± 2.73° in the ACL- and ALL-deficient knee. There was a statistically significant difference in static ATT between the intact and ACL-deficient knees (P = .039) but no difference through the addition of an ALL lesion (P = .068). For dynamic rotational control testing, there was no significant difference in ATT between groups but a significant difference in ITR was found (F = 25.17, P = .00034)., Conclusions: During the pivot-shift test, a combined lesion of the ACL and ALL has a significant effect on ITR whereas an isolated lesion of the ACL has no effect on either ATT or ITR. During the Lachman test, an isolated lesion of the ACL has a significant effect on ATT but an additional lesion of the ALL does not affect ATT., Clinical Relevance: Dynamic rotational control as tested by the pivot-shift test is greatly influenced by a combined lesion of the ACL and ALL. In clinical cases of a pivot shift, addressing the anterolateral structures may be considered., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: The usefulness of studying posture and its modifications due to locomotor deficiencies of multiple origins has been widely proven in humans. To assess its suitability in the canine species, static posturography and dynamic pedobarography were performed on lame dogs affected with unilateral elbow dysplasia and cranial cruciate ligament rupture by using a pressure platform. With this objective, statokinesiograms and stabilograms, the percentage of pressure distribution between limbs, paw area, mean pressure, and peak pressure, were obtained from lame and sound dogs. These data were compared with Peak Vertical Force values originated from a force platform in the same recording sessions., Results: Significant differences were found in the parameters mentioned above between sound and lame dogs and limbs., Conclusions: Posturography and pedobarography are useful and reliable for the monitoring of fore and hindlimb lameness in dogs, providing a new set of parameters for lameness detection.

Background: Cranial cruciate ligament (CrCL) insufficiency is a degenerative condition that is a common cause of pelvic limb lameness and osteoarthritis in dogs. Surgical therapies developed to treat dogs with naturally occurring CrCL insufficiency aim to address the resultant instability, but the in-vivo alterations in stifle kinematics associated with CrCL insufficiency have not been accurately defined. The objective of this study was to quantify the 3-dimensional femorotibial joint kinematics of dogs with naturally occurring cranial cruciate ligament (CrCL) insufficiency during ambulation. Eighteen client-owned dogs (20-40 kg) with natural unilateral complete CrCL rupture were included. Computed tomographic scans were used to create digital 3-dimensional models of the femur and tibia bilaterally for each dog. Lateral fluoroscopic images were obtained during treadmill walking and 3 complete gait cycles were analyzed. Stifle flexion/extension angle, craniocaudal translation, and internal/external rotation were calculated throughout the gait cycle using a previously described 3D-to-2D image registration process. Results were compared between the pre-operative CrCL-deficient and 6-month post-operative contralateral stifles (control)., Results: CrCL-deficient stifles were maintained in greater flexion throughout the gait cycle. Cranial tibial subluxation was evident in CrCL-deficient stifles at all time points throughout the gait cycle [9.7 mm at mid-stance (P < 0.0001); 2.1 mm at mid-swing (P < 0.0017)], and the magnitude of cranial tibial subluxation was greater at mid-stance phase than at mid-swing phase (P < 0.0001). Greater internal tibial rotation was present in CrCL-deficient stifles during stance phase (P < 0.0022) but no difference in axial rotation was evident during swing phase., Conclusions: Naturally occurring CrCL rupture causes profound craniocaudal translational and axial rotational instability, which is most pronounced during the stance phase of gait. Surgical stabilization techniques should aim to resolve both craniocaudal subluxation and axial rotational instability.

Purpose: Discoid meniscus often causes mechanical problems and needs surgical treatment at an early age. However, many aspects of its morphological development and changes remain unknown. The purpose of this study was to investigate the insertion of the femoral anterior cruciate ligament (ACL) via the behind-ACL approach and the morphology of the lateral femoral condyle to which the ACL attaches to clarify the morphological characteristics of the knee with discoid lateral meniscus (DLM)., Method: Sixty-six patients with meniscus injury who underwent arthroscopic surgery were retrospectively reviewed. Preoperative plane radiographs were reviewed. To evaluate the shape of the femoral condyle, the ratio of the medial and lateral condyles, obliquity of the inter-epicondylar line, and the prominence ratio were assessed. From the arthroscopic observation using the behind-ACL approach, the insertion of the femoral ACL was classified as low, middle, and high based on the height from the deepest area of the articular surface to the direct insertion, including fibrous extension from the joint surface at 90° flexion., Results: Twenty-nine patients had DLM (DLM group), and 37 patients had a semilunar meniscal injury (non-DLM group). The ratio of the lateral femoral condyle, obliquity of the inter-epicondylar line, and prominence ratio in the DLM group were significantly smaller than those in the non-DLM group. On the other hand, no significant difference in the ratio of the medial femoral condyle was observed. Arthroscopic evaluation revealed that the femoral ACL was significantly inserted lower in the DLM group than in the non-DLM group., Conclusion: The femoral ACL with DLM was inserted close to the femoral joint surface with morphological abnormality in the knees with DLM related to hypoplasic of the lateral femoral condyle., (Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.)

The effects of ACL-reconstruction on lower extremity joint mechanics during performance of the Star Excursion Balance Test (SEBT) and Single Leg Hop (SLH) are limited. The purpose of this study was to determine if altered lower extremity mechanics occur during the SEBT and SLH after ACL-reconstruction. One female Division I collegiate athlete performed the SEBT and SLH tasks, bilaterally, both before ACL injury and 27 months after ACL-reconstruction. Maximal reach, hop distances, lower extremity joint kinematics and moments were compared between both time points. Musculoskeletal simulations were used to assess muscle force production during the SEBT and SLH at both time points. Compared to the pre-injury time point, SEBT reach distances were similar in both limbs after ACL-reconstruction except for the max anterior reach distance in the ipsilateral limb. The athlete demonstrated similar hop distances, bilaterally, after ACL-reconstruction compared to the pre-injury time point. Despite normal functional performance during the SEBT and SLH, the athlete exhibited altered lower extremity joint mechanics during both of these tasks. These results suggest that measuring the maximal reach and hop distances for these tasks, in combination with an analysis of the lower extremity joint mechanics that occur after ACL-reconstruction, may help clinicians and researchers to better understand the effects of ACL-reconstruction on the neuromuscular system during the SEBT and SLH.

Purpose: To evaluate and compare the effect of preconditioning according to intraoperative workflow on the elongation behavior of single-side and fully knotted all-inside anterior cruciate ligament (ACL) reconstruction configurations in a biomechanical in vitro study., Methods: Four full construct all-inside ACL reconstruction groups (n = 8 per group) were tested using porcine tibias and bovine tendons. Groups included both an all-inside configuration with one- (group 1) and both-side knotted adjustable loop-length devices (group 2), without and with performing intraoperative preconditioning (group 1-intraoperative preconditioned [IPC], group 2-IPC). Adjustable loop-length devices for control groups were knotted according to test configurations. Intraoperative preconditioning specimens were further precycled for 10 times at 0.5 Hz and manually retensioned before knotting. All groups underwent dynamic cycling in position and force control mode each for 1,000 cycles at 0.75 Hz according to in vitro loading parameters replicating the in vivo ACL environment. Finally, a load-to-failure test at 50 mm/min was performed., Results: Intraoperative preconditioning increases initial graft tension for single- (242 ± 22 N vs 174 ± 13 N; P < .0001) and both-side knotted configurations (225 ± 15 N vs 159 ± 10 N; P < .0001) compared with controls and allows maintained graft tension at higher levels until reaching the end of position-controlled cyclic loading. Furthermore, dynamic elongation is reduced for one- (1.93 ± 0.28 vs 0.76 ± 0.12; P < .0001) and both-side knotted (1.84 ± 0.20 vs 0.96 ± 0.32; P < .0001) configurations by 61% and 47%, respectively. No intergroup (group 1 vs group 2 and group 1-IPC vs group 2-IPC) statistically significant differences could be found between one- and both-side knotted configurations., Conclusions: All-inside ACL reconstruction with preconditioning according to intraoperative workflow leads to a statistically significant improved mechanical behavior and may allow for optimizing initial graft tension and elongation for all-inside ACL reconstruction to reduce knee laxity. A single-side knotted configuration achieves similar stabilization strength to fully knotted constructs., Clinical Relevance: Graft insertion until tunnel docking increases the intratunnel graft portion that may optimize graft incorporation. Eliminating a suture knot stack may improve intraoperative workflow and reduce postoperative knot irritation., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The effectiveness of ACL functional knee braces to reduce meniscal and ACL strain after ACL injury or reconstruction is not well understood. A new dynamic knee tensioning brace system has been designed to apply an active stabilizing force to the knee. The ability of this system to reduce tissue strains is unknown. The purpose of this study was to test the ability of the dynamically tensioned brace to reduce strain in both the ACL and meniscus during rehabilitation activities., Methods: A combined in vivo/in silico/in vitro method was used to study three activities: gait, double leg squat, and single leg squat. Muscle forces and kinematics for each activity were derived through in vivo motion capture and applied to seven cadaveric knee specimens fitted with custom braces. Medial meniscal strain and ACL strain were measured in ACL intact, deficient and reconstructed conditions., Results: The brace lowered peak and average meniscal strain in ACL deficient knees (P < 0.05) by an average of 1.7%. The brace was also found to lower meniscal strain in reconstructed knees (1.1%) and lower ACL strain in ACL intact (1.3%) and reconstructed knees (1.4%) (P < 0.05)., Conclusions: This study supports the use of a brace equipped with a dynamic tensioning system to lower meniscal strain in ACL-deficient knees. Its use may help decrease the risk of subsequent meniscal tears in chronic ACL deficiency or delayed reconstruction. In ACL-intact and reconstructed knees, the brace may be beneficial in injury prophylaxis or in protecting the ACL graft following reconstruction. These results will aid clinicians make informed recommendations for functional brace use in patients with unstable knees., Level of Evidence: II.

Graft tissues within bone tunnels remain mobile for a long time after anterior cruciate ligament (ACL) reconstruction. However, whether the graft-tunnel friction affects the finite element (FE) simulation of the ACL reconstruction is still unclear. Four friction coefficients (from 0 to 0.3) were simulated in the ACL-reconstructed joint model as well as two loading levels of anterior tibial drawer. The graft-tunnel friction did not affect joint kinematics and the maximal principal strain of the graft. By contrast, both the relative graft-tunnel motion and equivalent strain for the bone tunnels were altered, which corresponded to different processes of graft-tunnel integration and bone remodeling, respectively. It implies that the graft-tunnel friction should be defined properly for studying the graft-tunnel integration or bone remodeling after ACL reconstruction using numerical simulation.

Purpose: To determine whether there are differences between adjustable-length loop and fixed-length loop devices in terms of the amount of displacement, temporal pattern of displacement, and ultimate failure load when tested using 4,500 cycles of sinusoidal loading with high loads (100-400 N)., Methods: Two cortical suspension devices with a fixed- or adjustable-length loop were tested. For our comparisons, a 20-mm fixed-length loop device and a fixed-length loop device with the same loop length were used. Comparisons between the devices used both a device-only model (DOM) and a device-bone-soft-tissue graft construct model (CM)., Results: In the DOM, the adjustable-length loop device showed weaker mechanical properties. Mean cumulative peak displacement was 1.91 mm for the adjustable-length loop device and 0.74 mm for the fixed-length loop device (P = .001). The displacement of the adjustable-length loop device increased between 1,000 and 4,500 cycles; in contrast, that of the fixed-length loop device reached a plateau. However, there was never displacement greater than 3 mm. In addition, the adjustable-length loop device showed a weaker ultimate failure load (925 N vs 1,410 N, P = .001). In the CM, the difference in cumulative peak displacement between the 2 groups decreased and did not reach statistical significance. The displacement of both devices showed a similar pattern. In addition, there was no difference in ultimate failure load between the 2 groups., Conclusions: There was no significant difference in terms of total displacement, temporal pattern of displacement, and ultimate failure load between the 2 devices in the CM, which is the more clinically relevant model. Furthermore, even in the DOM, the difference in total displacement was small and did not reach a clinically meaningful level. Therefore, both devices can be used effectively during anterior cruciate ligament reconstruction with soft-tissue graft., Clinical Relevance: Both femoral cortical suspension devices with adjustable- and fixed-length loops can be used with similar mechanical properties during anterior cruciate ligament reconstruction., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this systematic review and meta-analysis was to evaluate the effect of the timing of anterior cruciate ligament (ACL) reconstruction on clinical and stability outcomes by analyzing high-quality studies that assessed timing as a primary objective., Methods: The MEDLINE, EMBASE, and Cochrane database were systematically searched. The inclusion criteria were as follows: (1) English articles, (2) noncomparative study or relevant study reporting clinical and/or stability results, and (3) timing of the ACL reconstruction as a primary objective. Study type, level of evidence, randomization method, exclusion criteria, number of cases, age, sex, timing of ACL reconstruction, follow-up, clinical outcomes, stability outcomes, and other relevant findings were recorded. Statistical analysis of the Lysholm scores and KT-1000 arthrometer measurements after early and delayed ACL reconstruction was performed using R version 3.3.1., Results: Seven articles were included in the final analysis. There were 6 randomized controlled trials and 1 Level II study. Pooled analysis was performed using only Level I studies. All studies assessed the timing of ACL reconstruction as a primary objective. The definition of early ranged broadly from 9 days to 5 months and delayed ranged from 10 weeks to >24 months, and there was an overlap of the time intervals between some studies. The standard timing of the delayed reconstruction was around 10 weeks from injury in the pooled analysis. After pooling of data, clinical result was not statistically different between groups (I 2 : 47%, moderate level of heterogeneity). No statistically significant difference was observed in the KT-1000 arthrometer measurements between groups (I 2 : 76.2%, high level of heterogeneity) either., Conclusion: This systematic review and meta-analysis performed using currently available high-quality literature provides relatively strong evidence that early ACL reconstruction results in good clinical and stability outcomes. Early ACL reconstruction results in comparable clinical and stability outcomes compared with delayed ACL reconstruction., Level of Evidence: Level II, a systematic review and meta-analysis of Level I and II studies., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Background: Following anterior cruciate ligament injury and subsequent reconstruction transverse plane tibiofemoral rotation becomes underconstrained and overconstrained, respectively. Conflicting reports exist on how rotations influence loading at the knee. This investigation aimed to determine the mechanical effects of internal and external tibial rotation offsets on knee kinematics and ligament strains during in vitro simulations of in vivo recorded kinematics., Method: A 6-degree-of-freedom robotic manipulator arm was used to articulate 11 cadaveric tibiofemoral joint specimens through simulations of four athletic tasks produced from in vivo recorded kinematics. These simulations were then repeated with 4° tibial rotation offsets applied to the baseline joint orientation., Findings: Rotational offsets had a significant effect on peak posterior force for female motion simulations (P < 0.01), peak lateral force for most simulated tasks (P < 0.01), and peak anterior force, internal torque, and flexion torque for sidestep cutting tasks (P ≤ 0.01). Rotational offsets did not exhibit statistically significant effects on peak anterior cruciate ligament strain (P > 0.05) or medial collateral ligament strain (P > 0.05) for any task., Interpretation: Transverse plane rotational offsets comparable to those observed in anterior cruciate ligament deficient and reconstructed patients alter knee kinetics without significantly altering anterior cruciate ligament strain. As knee degeneration is attributed to abnormal knee loading profiles, altered transverse plane kinematics may contribute to this. However, altered transverse plane rotations likely play a limited role in anterior cruciate ligament injury risk as physiologic offsets failed to significantly influence anterior cruciate ligament strain during athletic tasks., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The anterior cruciate ligament (ACL) is an important structure maintaining stability of the knee joints. Deficits in physical stability and the proprioceptive capabilities of the knee joints are observed, when the ACL is damaged. Additionally, a unilateral ACL injury can affect bilateral knee proprioception; therefore, proprioception of the ACL may play a key role in stability. Electroacupuncture therapy has a definite effect nerve regeneration. In this study, cynomolgus monkeys were randomly divided into 4 groups: the model control group, intervention of the injured knee with electroacupuncture (IIKE) group, intervention of the bilateral knees with electroacupuncture (IBKE) group, and the blank control group. The unilateral ACL injury model was developed in IIKE and IBKE groups; acupuncture points around the knees underwent intervention similarly in the IIKE and IBKE groups. Then, mRNA and protein expressions of NT-3 and TrkC in the dorsal root ganglion and of growth-associated protein-43 in the ACL increased according to reverse-transcription quantitative polymerase chain reaction and Western blotting results. Decreased incubations and increased amplitudes were found for somatosensory-evoked potentials and motor nerve conduction velocity. The finding indicates that electroacupuncture may play an important role in the recovery of proprioception in the ACL by activating the NT-3/TrkC signalling pathway.