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Background: The aims of this study were to describe a lateral extra-articular tenodesis (LET) using no additional hardware and compare the tibiofemoral kinematics of anterior cruciate ligament (ACL) reconstruction augmented with either the LET or a standard anatomic anterolateral ligament (ALL) reconstruction using intra-tunnel fixation., Methods: Ten cadaveric knees were mounted on a robotic testing system and underwent a kinematic assessment of anterior tibial translation and internal tibial rotation under a simulated pivot-shift in the following states: ACL-intact, ACL-sectioned, ACL-sectioned/anterolateral complex (ALC)-sectioned, ACL-reconstructed/ALC-sectioned, ACL-reconstructed/ALL-reconstructed, and ACL-reconstructed/LET. For the LET, an iliotibial autograft was passed under the fibular collateral ligament and secured to the femur with the pull sutures of the ACL reconstruction femoral cortical suspensory fixation device, positioned at the distal ridge of Kaplan's fibers., Results: Anterior tibial translation was restored to normal by ACL reconstruction without meaningful benefit of augmentation with LET or ALL. ACL reconstruction restored internal tibial rotation close to normal between 0° and 30°, but increased internal tibial rotation persisted between 45° and 90°. Augmentation of ACL reconstruction with the LET reduced internal rotation close to normal between 45° and 90°, whereas increased internal rotation persisted after ALL reconstruction., Conclusion: ACL reconstruction and LET are complementary in controlling tibiofemoral kinematics of knees with a combined ACL and ALC injury: ACL reconstruction restored native tibiofemoral kinematics except for internal rotation at flexion greater than 30°. The increased internal rotation at flexion greater than 30° was restored to normal with an LET, but not with an ALL reconstruction., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The ten fresh-frozen human cadaveric knees and the equipment and disposables for the all-inside ACL reconstruction were provided by Arthrex. This study was funded in part by the Departments of Orthopaedics and Sports Medicine of the University of Washington School of Medicine and Seattle Children’s Hospital. Dr. Schmale has received grants from SIGN Fracture Care Int and Arthrex, outside the submitted work. For the remaining authors none were declared., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: We aimed to quantify the sensitivity in biomechanical response and stability of the intact and anterior cruciate ligament deficient (ACL-D) joints at mid-to-late stance periods of gait to the alterations in activation of gastrocnemii (Gas) muscles., Methods: A validated kinematics-driven musculoskeletal finite-element model of the lower extremity is used to compute knee joint response and stability under reported kinetics-kinematics of healthy subjects. Activation in Gas is altered under prescribed gait data at the mid-to-late stance of gait and associated changes in remaining muscle forces/contact forces/areas/ACL force and joint stability are computed in both intact and ACL-D joints., Results: In the intact joint, the anterior-tibial-translation (ATT) as well as ACL and joint contact forces follow variations in Gas forces. Both the stability and ATT of an ACL-D joint are restored to the near-intact levels when the activity in Gas is reduced. Knee joint instability, excessive ATT as well as larger peak articular contact stresses with a posterior shift in contact areas are estimated under greater Gas forces., Conclusions: ACL-D joint is unstable with ATT > 10 mm under larger activities in Gas. Gas is an ACL-antagonist while hamstrings and soleus are ACL-agonists. The near-intact joint stability and ATT of an ACL-D joint can be restored at a lower activation in Gas; or in other words, when activation in ACL-antagonist muscles drops compared with that in ACL-agonist muscles. Results could help analyze the gait of ACL-D copers and non-copers and provide better understanding towards improved preventive, diagnostic, and treatment approaches., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: Injuries of the anterolateral ligament (ALL) are fairly common in patients with ruptures of the anterior cruciate ligament (ACL). Before considering repair or reconstruction of the ALL, the lack of knowledge with regard to the biomechanical behavior of this ligament must be considered. The purpose of this study was to analyze the strain of the ALL induced by tibial internal rotation at different flexion angles and find out the strain distribution features., Methods: The ALLs of ten fresh-frozen cadaver knees were dissected. All specimens underwent tibial internal rotation from 0° to 25° at 30°, 60°, 90°, and 120° of knee flexion. Strain distribution of the ALL during internal rotation was recorded by digital image correlation (DIC). The overall strain and sub-regional strain were measured., Results: The strain of the ALL increased with increasing tibial internal rotation. With 25° of internal rotation, the overall strain at each flexion angle was 12.89 ± 2.73% (30°), 15.32 ± 2.50% (60°), 18.94 ± 2.34% (90°), and 20.10 ± 3.27% (120°). The sub-regional strain was significantly different at all flexion angles. The strain of the distal 1/3 of the ALL was the greatest, followed by the middle 1/3, while the proximal 1/3 was the smallest (all P < 0.001)., Conclusion: The ALL resisted internal rotation of the tibia by becoming more tense with increasing rotation. A significantly high strain was observed in the distal portion near the tibial insertion site of the ALL, which may suggest that this region is prone to injury with excessive internal rotation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Purpose: Anterior cruciate ligament (ACL) ruptures are common and are frequently reconstructed using a patellar tendon (PT) autograft. Unfortunately, the time course of PT healing after ACL reconstruction is not particularly well understood. Thus, the primary objective of this study was to use shear wave elastography (SWE) to evaluate the extent to which shear wave speed (SWS) is associated with time after ACL reconstruction., Methods: Longitudinal SWE images were acquired from lateral, central, and medial regions of the PT from two groups: 30 patients who had undergone ACL reconstruction with a PT autograft within the preceding 40 months, and 30 age-matched asymptomatic control subjects. SWE images were acquired at 20° and 90° of passive flexion from both knees. In each subject group, statistical analyses assessed changes in mean SWS with time post-surgery, as well as differences in mean SWS between PT regions and limbs., Results: In the ACL reconstruction patients, mean SWS increased with time post-surgery in the lateral region of the involved knee (p = 0.025) and decreased with time post-surgery in the central region of the contralateral knee (p = 0.022)., Conclusion: The findings suggest that there is an association between the mechanical properties of the PT and time post-surgery in both the involved and contralateral limbs after ACL reconstruction. These changes are likely due to maturation of the donor site tissue and changes in gait/loading patterns following ACL rupture and reconstruction., Level of Evidence: Level II - Prospective Cohort., (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: 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 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.)

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.)

Background: To compare the early postoperative outcomes and complications of double-bundle anterior cruciate ligament (ACL) reconstruction with and without remnant preservation., Methods: The study population comprised 125 consecutive knees that underwent double-bundle ACL reconstruction using hamstring autograft. Among the 125 knees, remnant preservation was indicated for 50 knees, while standard double-bundle reconstruction was performed in the remaining 75 knees. Postoperative evaluations included heel-height difference (HHD) at periodical follow-ups, number of knees requiring arthroscopic debridement due to problematic extension loss within six months, re-injury within one year, graft status upon second-look arthroscopy, and clinical examinations by Lysholm score and KT measurement at one year., Results: All patients could be followed up for a minimum of one year after surgery. When the results obtained from both groups were compared, HHD values were significantly larger in the preservation group at three and six months, and the rate of knees requiring arthroscopic debridement was also higher in this group (12% versus 4.0%). Graft status on second-look arthroscopy was considered to be good for 92% of the knees in the preservation group versus 59% in the non-preservation group. Re-injury rates within one year were 2.0% in the preservation group and 5.3% in the non-preservation group. No significant differences in clinical examinations were found between the groups at one year., Conclusions: Remnant preservation in double-bundle hamstring autograft ACL reconstruction may enhance tissue healing; however, retention of the remnant with its full volume resulted in an increased incidence of postoperative problematic extension loss., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: To properly study knee kinetics, kinematics and the effects of injury and surgical treatment in vitro, the knee should be constrained as little as possible, while imposing physiological loads. A novel dynamic biomechanical knee system (BKS) is presented here. The aim of this study was to test the feasibility and reproducibility of the system and demonstrate its features with an Anterior Cruciate Ligament (ACL) lesion model., Methods: Six goat knees were used in the current study. Flexion and extension simulating gait was imposed by a servo-motor, while normal joint load was applied by two artificial muscles. Intra-class correlation coefficients (ICCs) were assessed for inter-test measures, while paired t-tests were performed for comparison between intact knees and knees with ACL-lesion., Results: The ICC's for inter-test measures based on all six goat knees were excellent: varus/valgus: ICC=0.93; rotation: ICC=0.94 (all p<0.01), and translation in frontal (x)-, side (y)- and upward (z)-direction (ICC=0.90, 0.88 & 0.94) (all p<0.01). A significant increase in joint center movement was found in knees after creating an ACL-lesion (p=0.018): translation increased more than two-fold in frontal (p=0.016), side (p=0.004) and upward (p=0.018) direction., Conclusions: Five degrees of motion were reproducibly assessed in the intact joint, suggesting that the goat knee may find its natural pathway when loaded in the BKS. The novel five-degrees-of-freedom knee system allows a detailed study of the effect of a diversity of defects and surgical treatments on knee biomechanics under physiological loading conditions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: The aim of our study was to evaluate the effects of gender on recovery of knee joint biomechanics over the stance phase of gait after reconstruction of the anterior cruciate ligament (ACL)., Methods: Gait parameters and knee joint kinematics and kinetics were compared in 32 patients (16 male and 16 female) who underwent ACL reconstruction for a unilateral ACL deficiency, with comparison to an age-, height-, and weight-matched Control group. Knee flexion, adduction and tibial rotation angles were measured and knee extension and abduction moment was calculated by inverse dynamics methods., Results: Females exhibited more tibial external rotation, in both the Control and ACL groups (P<0.05), which was not changed after ACL reconstruction. Prior to reconstruction, sagittal plane biomechanics were changed, in both males and females, compared to the Control groups (P<0.05). These abnormal sagittal plane mechanics were recovered at 12months, but not six months post-reconstruction., Conclusions: We identified gender-based differences in tibial rotation that influenced the kinematics and kinetics of the knee over the stance phase of gait, both pre-operatively and post-ACL reconstruction. Evaluation of biomechanical effects of ACL injury, before and after reconstruction, should be separately evaluated for females and males., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Historically, inconsistent and unpredictable results of open primary anterior cruciate ligament (ACL) repair were reported. Recently, however, good results of arthroscopic primary ACL repair of proximal tears have been reported. Purpose of this study was to assess the direct postoperative gap formation and maximum failure load following simulated knee motion after primary ACL repair., Methods: Six matched-paired human cadaveric knees (mean age: 52years, range: 48 to 56years) were used. After primary proximal ACL repair with either suture button fixation or suture anchor fixation, knees were cycled five, 50 and 100 times with a simulated active quadriceps force. Gap formation between the femoral wall and ligament was measured using a digital caliper and maximum failure load was tested., Results: Gap formation after five, 50 and 100cycles of the knee were 0.30mm (±0.23), 0.75mm (±0.55) and 0.97mm (±0.70), respectively, with no significant differences between both fixation techniques. The overall maximum failure load was 243N (±143) with no difference between both techniques. Most common failure mode was slipping of suture from the fixation., Conclusion: Following proximal ACL repair, gap formation of approximately one millimeter was measured after repetitious knee cycling with mean maximum failure load of 243N. These findings are likely to be sufficient for careful early active range of motion (ROM) when extrapolating from other available studies. Future studies with second-look arthroscopy are necessary to assess the gap formation and healing in patients treated with primary repair., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: Women are more likely than men to injure the anterior cruciate ligament (ACL). Human and animal trials have linked circulating estradiol to injury rate and ligament strength. Fewer studies have examined the role of testosterone. The purpose of this study was to determine if male rats with normal testosterone levels would have stronger ACLs than castrated rats., Methods: Eight castrated (group C) and eight normal (group N) 12-week-old, male Sprague-Dawley rats were used for the study. Mean testosterone levels were 0.14ng/mL (95% CI: 0.10 to 0.17) in group C and 3.54ng/mL (95% CI: 1.32 to 5.76) in group N. After euthanasia, ACL cross-sectional area was calculated, and a servohydraulic material testing unit was used to measure ligament properties., Results: Specimens from both groups had similar cross-sectional area, but N specimens showed greater mean load-to-failure (34.5N [95% CI: 31.6 to 37.4] vs 29.2N [95% CI: 27.9 to 30.6]) and ultimate stress (38.7MPa [95% CI: 34.1 to 43.3] vs 31.8MPa [95% CI: 29.8 to 33.8]). Mean energy was 27.7mJ (95% CI: 23.1 to 32.2) in the N group and 23.4mJ (95% CI: 18.2 to 28.6) in the C group., Conclusions: Rats with normal circulating testosterone had higher ACL load-to-failure and ultimate stress, indicating that testosterone may influence ACL strength and the injury rate of the ligament., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: Athletes with anterior cruciate ligament (ACL) injuries usually undergo ACL-reconstruction (ACLR) in order to restore joint stability, so that dynamic maneuvers such as the sidestep cut can be performed. Despite restoration of joint stability after ACLR, many athletes do not return to pre-injury levels and may be at a high risk of a second ACL injury. The purpose of this study was to determine whether or not ACL loading, would increase after ACLR., Methods: One female Division I collegiate athlete performed bilateral unanticipated sidestep cuts both before ACL injury and 27months after ACLR. Musculoskeletal simulations were used to calculate ACL loading during the deceleration phase of the sidestep cuts., Results: Twenty-seven months after ACLR, the athlete demonstrated higher total ACL loading in the ipsilateral limb as well as altered joint kinematics, moments, and quadriceps muscle force production. In the contralateral limb, there were no increases in total ACL loading or muscle force production yet altered lower extremity joint kinematics and moments were present after ACLR., Conclusions: Higher total ACL loading in the ipsilateral limb of this athlete may suggest an increased risk of second ACL injury. The results of this study provide an initial step in understanding the effects of ACLR on the risk of second ACL injury in an elite athlete and suggest that it is important to develop a better understanding of this surgical intervention on knee joint loading, in order to reduce the risk of second ACL injury while performing dynamic maneuvers., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: The aim of this study was to compare the clinical performance and complications between an ACL reconstruction with a remnant-preserving single-bundle technique and a standard single-bundle technique., Methods: A search was performed of RCTs comparing the clinical outcomes and complications of ACL reconstruction with remnant-preserving and standard single-bundle techniques during October 2014. Relevant data were extracted and CONSORT was used to assess the methodological quality. Stata/SE 12.0 was used to perform a meta-analysis of the clinical outcomes., Results: Six RCTs were included, with a total of 378 patients: 190 in the remnant-preservation technique group and 188 patients in standard-technique group. Assessing anterior stability, no difference was found between the groups for the KT arthrometer, negative rate of Lachman, and the pivot shift test. Assessing functional outcome, there was no significant difference in IKCD scores and grades or Lysholm score. In terms of complications, the percentage of tibial tunnel enlargement in the group of the remnant-preservation technique was significantly lower, despite no significant difference in the incidence of cyclops lesions., Conclusions: The outcome of single-bundle ACL reconstruction with the remnant-preservation technique is similar to that with the standard technique in terms of anterior stability and functional recovery of the knee. Remnant preservation in ACL reconstruction decreases the percentage of tibial tunnel enlargement. Level of evidence is II., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Background: The ovine stifle joint is an ideal preclinical model to study knee joint biomechanics. Knowledge of the ovine ligamentous and meniscal loading during normal gait is currently limited., Methods: The in vivo kinematics of the ovine stifle joint (N=4) were measured during "normal" gait using a highly accurate instrumented spatial linkage (ISL, 0.3±0.2mm). These motions were reproduced in vitro using a unique robotic testing platform and the loads carried by the anterior/posterior cruciate ligaments (ACL/PCL), medial/lateral collateral ligaments (MCL/LCL), and medial/lateral menisci (MM/LM) during gait were determined., Results: Considerable inter-subject variability in tissue loads was observed. The load in the ACL was near zero at hoof-strike (0% gait) and reached a peak (100 to 300N) during early-stance (~10% gait). The PCL reached a peak load (200 to 500N) just after hoof-strike (~5% gait) and was mostly unloaded throughout the remainder of stance. Load in the MCL was substantially lower than the cruciate ligaments, reaching a maximum of 50 to 100N near the beginning of stance. The LCL carried a negligible amount of load through the entire gait cycle. There was also a major contribution of the MM and LM to load transfer from the femur to the tibia during normal gait. The total meniscal load reached a maximum average between 350 and 550N during gait., Conclusion: Knowledge of joint function during normal motion is essential for understanding normal and pathologic joint states. The considerable variability in the magnitudes and patterns of tissue loads among animals simulates clinical variability in humans., Level of Evidence: III., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Introduction: Anterior cruciate ligament injuries are closely associated with excessive loading and motion about the off axes of the knee, i.e. tibial rotation and knee varus/valgus. However, it is not clear about the 3-D mechanical actions of the lateral and medial hamstring muscles and their differences in loading the ACL. The purpose of this study was to investigate the change in anterior cruciate ligament strain induced by loading the lateral and medial hamstrings individually., Methods: Seven cadaveric knees were investigated using a custom testing apparatus allowing for six degree-of-freedom tibiofemoral motion induced by individual muscle loading. With major muscles crossing the knee loaded moderately, the medial and lateral hamstrings were loaded independently to 200N along their lines of actions at 0°, 30°, 60° and 90° of knee flexion. The induced strain of the anterior cruciate ligament was measured using a differential variable reluctance transducer. Tibiofemoral kinematics was monitored using a six degrees-of-freedom knee goniometer., Results: Loading the lateral hamstrings induced significantly more anterior cruciate ligament strain reduction (mean 0.764 [SD 0.63] %) than loading the medial hamstrings (mean 0.007 [0.2] %), (P=0.001 and effect size=0.837) across the knee flexion angles., Conclusion: The lateral and medial hamstrings have significantly different effects on anterior cruciate ligament loadings. More effective rehabilitation and training strategies may be developed to strengthen the lateral and medial hamstrings selectively and differentially to reduce anterior cruciate ligament injury and improve post-injury rehabilitation., Clinical Relevance: The lateral and medial hamstrings can potentially be strengthened selectively and differentially as a more focused rehabilitation approach to reduce ACL injury and improve post-injury rehabilitation. Different ACL reconstruction procedures with some of them involving the medial hamstrings can be compared to each other for their effect on ACL loading., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Background: In the past, several studies investigated factors that are prognostic or associated with outcome after anterior cruciate ligament (ACL) reconstruction. A recent review showed that only limited evidence is available for most studied factors, and that insufficient analysis methods were used commonly. Therefore, the aim of this study was to add more weight to the existing evidence, about factors that are associated with a more rapid outcome after ACL reconstruction. The second aim was to use multivariate analysis to study the possible factors independently., Methods: A cohort study was conducted with a follow-up of six months. Before surgery, patient variables were scored. Surgical variables were scored during arthroscopic ACL reconstructions with a single-bundle technique and hamstring autograft. The Lysholm score and subscales of the Knee Injury Osteoarthritis Outcome Score (KOOS) were assessed six months post surgery. A multiple analysis of variance (ANOVA) model was used to identify prognostic factors for outcome., Results: In total, 118 patients were included. Patients, aged ≤30years, with a subjective knee score ≥ six, with normal flexion range of motion (ROM) of the knee, with flexion and extension strength deficit of ≤20%, and those with no previous knee surgery in the same knee at baseline scored significantly higher on outcome after multivariate analysis. No significant effect of surgical factors could be found., Conclusion: Younger age, higher subjective knee score, normal knee flexion, normal knee flexion and extension strength, and no previous knee surgery in the patients' history at baseline are associated with a more rapid recovery after ACL reconstruction., Level of Evidence: Level III, prognostic study., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Purpose: This mechanical study using an in vitro porcine model compared composite interference screw fixation of soft tissue ACL grafts in tibial tunnels., Methods: Forty-eight porcine profundus tendons and tibiae were divided into four groups of 12 closely matched specimens. Equivalent diameter grafts were assigned to each group. Tibial bone tunnels were drilled to 0.5mm greater than graft diameter. Grafts were fixed in tunnels using one 10 × 35 mm composite interference screw designed by four different manufacturers. Maximal insertion torque and perceived within group mechanical testing outcome predictions were recorded. Constructs were potted and loaded into a six degrees of freedom clamp that placed the servohydraulic device tensile loading vector in direct tunnel alignment. Constructs were pre-loaded to 25 N, pre-conditioned between 0 and 50 N for 10 cycles (0.5 Hz), submaximally tested between 50 and 250 N for 500 cycles (one hertz) and load to failure tested at 20mm/min., Results: Statistically significant differences were not observed between groups for displacement during submaximal cyclic loading, yield load, displacement at yield load, stiffness, ultimate load at failure and displacement at ultimate load. One composite screw group displayed a slightly greater proportion of specimens that required use of more than one screw during insertion., Conclusions: Under highly controlled conditions groups displayed comparable fixation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Background: Since the 1980's several artificial ligaments were used for reconstruction of the anterior cruciate ligament (ACL) serving different complications. The aim of this study was to assess the clinical and functional outcomes of primary ACL reconstruction using the Ligament Augmentation Reconstruction System (LARS™) with a minimum follow-up of 10-years. The LARS™ presents a synthetic material consisting of non-absorbing polyethylene terephthalate fibres used for ligament reconstruction., Methods: Outcomes of 18 patients who underwent arthroscopic ACL reconstruction using the LARS™ system between 2000 and 2004 with a minimum follow-up of 10 years were observed. The International Knee Documentation Committee score (IKDC), Visual Analog Scale (VAS), Lysholm score, and Tegner Activity Scale were assessed. Clinical assessment was performed by Lachman testing, assessment of side-to-side difference on KT-2000 testing and plain radiography evaluation of osteoarthritis., Results: There were seven males and 11 females, mean age 29 years (range, 18 to 44 years) and a mean follow-up of 151.5 months. Five patients (27.8%) sustained a re-rupture of the LARS™ system and underwent revision surgery after a mean time of 23 months and four patients (22.2%) presented with a re-rupture. The average IKDC score was 76.60 ± 18.18, the average Lysholm score was 88.00 ± 10.07 and the average Tegner activity score was five at final follow-up., Conclusion: Our results indicate that the LARS™ system should currently not be suggested as a potential graft for primary reconstruction of the ACL. In special cases, however, the LARS™ system can serve as an alternative graft., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Introduction: Meniscal injury has been well documented as a frequent consequence of both acute and chronic ACL deficiency. The purpose of this study was to evaluate the effect of ACL deficiency on meniscal loads in vivo and determine how these loads would change over time after ACL injury., Methods: The in vivo kinematics of the stifle joint of five sheep were measured during normal gait, as well as 4 and 20 weeks after ACL transection. A unique robotic testing platform was then programmed to reproduce all the previously recorded kinematics and the loads carried by medial and lateral menisci during gait were estimated., Results: The results demonstrated a significant increase in both medial and lateral meniscal loads 20 weeks following ACL transection, mainly during mid-stance phase of gait (p = 0.007 and p = 0.003, respectively), with interesting inter-subject variability. A moderate correlation (R(2) ≥ 0.5) between in situ meniscal loads and anterior tibial translations was also detected over time after injury, increased translations post injury generally corresponded to larger meniscal loads., Conclusion: The dramatic increase in meniscal loads long term post ACL transection probably explains the meniscal changes or injuries reported clinically in many chronic ACL-deficient knees., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: This study compared lower extremity EMG activation and sagittal plane kinematics of subjects at a minimum of 2 years post-successful ACL reconstruction and rehabilitation during instrumented single leg hop testing., Methods: Comparisons were made based on subject responses to the following question, "compared to prior to your knee injury how capable are you now in performing sports activities"? Group 1=very capable, Group 2=capable, and Group 3=not capable. In addition to EMG (1000 Hz) and kinematic (60 Hz) data, subjective knee function, internal health locus of control, sports activity characteristics (intensity, frequency) pre-knee injury, and at follow-up were also compared., Results: Group 3 had lower perceived knee function, decreased perceived sports intensity, and more subjects with decreased sports activity intensity by two levels compared to pre-injury values. Perceived function scores, anterior laxity measurements and grades were similar between groups. During single leg hop propulsion and landing Group 1 (very capable) had greater involved lower extremity gluteus maximus and medial hamstring activation amplitudes than Group 3 (not capable). Perceived sports capability was related to better subjective knee function, and higher perceived sports activity intensity., Conclusion: Neuromuscular compensations suggesting a hip bias with increased gluteus maximus and medial hamstring activation were identified at the involved lower extremity among most subjects who perceived high perceived sports capability compared to pre-injury status. These compensations may be related to a permanent neurosensory deficit, and its influence on afferent pathway changes that influence CNS sensorimotor re-organization., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Associations between objective and subjective measures of knee function may facilitate rehabilitation in ACL-patients., Aim: The aim of this study is to investigate if a test-battery of functional and/or muscle outcomes are associated with Knee osteoarthritis outcome score (KOOS) subscales (Sport/Rec and QOL) in ACL-reconstructed patients., Methods: 23 hamstring auto-graft ACL-reconstructed men (mean age: 27.2 standard deviation 7.5 years, BMI: 25.4 standard deviation 3.2 time since surgery: 27 standard deviation 7 months) completed KOOS-questionnaire and an objective test-battery: (i) one-leg maximal jump for distance (OLJD), isometric maximal voluntary contraction (MVC) for (ii) knee extensors and (iii) flexors, and (iv) maximal counter movement jump (CMJ). Sagittal kinematic data were recorded during CMJ using a 6-camera Vicon MX system. Multilevel linear regression analysis was used to determine the strength of associations between KOOS parameters (Sport/Rec and QOL) that a priori were defined as dependent variables and 4 models of independent outcomes from the test-battery., Results: Moderate associations between OLJD and Sport/Rec (r(2)=0.26, p<0.01) and QOL (r(2)=0.26, p<0.01) were observed (Model 1). Adding knee extensor or flexor MVC to the analysis (Model 2) increased the strength of the associations (up to r(2)=0.53, p<0.01, and r(2)=0.31, p=0.02 for Sport/Rec and QOL, respectively). Adding both knee extensor and knee flexor MVC to the analysis (Model 3) did not improve the regression model and only minor increases were observed when including kinematic data of CMJ (Model 4)., Conclusion: Moderate-to-large proportion (31-53%) of the variation in KOOS was explained by OLJD and MVC which may add to design effective future rehabilitation interventions for ACL-patients., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Anterior cruciate ligament (ACL) reconstruction using a single-bundle transtibial technique can achieve good or excellent results in more than 90% of patients, but anatomical and biomechanical studies have questioned its ability to restore knee function. The purpose of this study was to evaluate clinical and tomographic results (patient satisfaction, knee function, and tunnel location) of patients who underwent transportal or transtibial single-bundle ACL reconstruction., Methods: Seventy-one patients with ACL tears were included. Forty-one patients were treated by the single-bundle transportal technique and 30 patients were treated by the single-bundle transtibial technique. Clinical and tomographic data were analyzed in both groups., Results: After a minimum of 2-year period, the transportal group showed more patients with normal clinical tests than the transtibial group (Lachman [p=0.037], pivot shift [0.00], anterior drawer [0.002]; and arthrometer [0.002] tests). Regarding CT evaluation, transportal and transtibial groups obtained the following femoral central tunnel location (mean [SD]), as percentage: 30 (6.5) and 4.2 (6.4) in high-low axis; and 30.9 (5.9) and 33.2 (4.6) in the deep-shallow axis. Values in the tibial side were, respectively: 38 (6.5) and 46.0 (6.8) in the anterior-posterior axis; and 47.2 (2.5) and 46.9 (2.1) in the medial-lateral axis., Conclusion: CT findings showed that the transportal single-bundle technique positions the ACL tunnel closer to the native ACL footprint in both femur and tibia compared with the transtibial single-bundle technique. Moreover, mild asymptomatic instability and extension deficit were observed more often in the transtibial group., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: To compare the ceiling effect of the Lysholm and IKDC subjective scores for assessing functional outcome after ACL reconstruction and evaluated the correlation with the one-leg hop test., Methods: A total of 134 patients who underwent ACL reconstruction between 2007 and 2011 were enrolled in this study. All patients fulfilled the postoperative 6- and 12-month evaluations. The ceiling effect of the Lysholm and IKDC subjective scores was assessed, and the correlations between two scales and one-leg hop test were analysed., Results: For the entire sample, the ceiling effect for the Lysholm score was 14.9% and 30.6% at 6 and 12 months postoperatively. The values for the IKDC subjective score were 5.2% and 17.2%, respectively. In all subjects, the correlation coefficients [95% confidence intervals] between the IKDC subjective score and one-leg hop test at 6 and 12months (r=0.492, [0.34 to 0.62]; r=0.296, [0.12 to 0.46]) were higher than those for the Lysholm score (r=0.355, [0.18 to 0.51]; r=0.241, [0.06 to 0.41]), respectively.(p<0.05)., Conclusion: With regard to evaluating ACL reconstruction outcomes in patients, no significant difference between the IKDC subjective and the Lysholm scores exists in terms of the amount of ceiling effect and the correlation with the LSI. However, the concern that the ceiling effect of the Lysholm score was greater than the IKDC subjective score, should be addressed in assessing the patient's functional status postoperatively., Level of Evidence: III, retrospective comparative study., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Anterior cruciate ligament (ACL) rupture is a common lesion. Current treatment emphasizes arthroscopic ACL reconstruction via a graft, although this approach is associated with potential drawbacks. A new method of dynamic intraligamentary stabilization (DIS) was subjected to biomechanical analysis to determine whether it provides the necessary knee stability for optimal ACL healing., Methods: Six human knees from cadavers were harvested. The patellar tendon, joint capsule and all muscular attachments to the tibia and femur were removed, leaving the collateral and the cruciate ligaments intact. The knees were stabilized and the ACL kinematics analyzed. Anterior-posterior (AP) stability measurements evaluated the knees in the following conditions: (i) intact ACL, (ii) ACL rupture, (iii) ACL rupture with primary stabilization, (iv) primary stabilization after 50 motion cycles, (v) ACL rupture with DIS, and (vi) DIS after 50 motion cycles., Results: After primary suture stabilization, average AP laxity was 3.2 mm, which increased to an average of 11.26 mm after 50 movement cycles. With primary ACL stabilization using DIS, however, average laxity values were consistently lower than those of the intact ligament, increasing from an initial AP laxity of 3.00 mm to just 3.2 mm after 50 movement cycles., Conclusions: Dynamic intraligamentary stabilization established and maintained close contact between the two ends of the ruptured ACL, thus ensuring optimal conditions for potential healing after primary reconstruction. The present ex vivo findings show that the DIS technique is able to restore AP stability of the knee., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Purpose: A prospective randomized study was performed to assess the influence of extra-articular ilio-tibial band tenodesis on the results of arthroscopic anterior cruciate ligament (ACL) reconstruction in patients with advanced-stage chronic anterior laxity of the knee., Methods: Preoperatively, the two constituent groups of our series of 120 patients: group 1 (Kenneth Jones) and group 2 (Kenneth Jones+extra-articular ilio-tibial band tenodesis) were strictly comparable with regard to demographic data, activity level, interval between the injury and the operation, and even objective laxity. Through radiological measurements made by passive dynamic X-rays, we studied the evolution of the objective laxity on the two compartments (medial and lateral) of the knee before the surgery and in review., Results: At 2 years follow-up, there was no significant difference between the two groups in terms of the subjective result, sports, and the overall international knee documentation committee score, however, In terms of objective laxity; Gain laxity obtained after surgery on the lateral compartment, was statistically higher in cases of extra-articular associated plasty (+29%), by cons in cases of intra-articular reconstruction alone, the laxity of the lateral compartment was poorly controlled and has continued to evolve despite the plasty of the ACL., Conclusion: The indication of an associated extra-articular plasty remains very discussed but we plead for an objective criterion with knowing the importance of preoperative objective laxity especially that of the lateral compartment to decide if it necessary, or not, being associated., Level of Evidence: Level I, therapeutic prospective randomized trial., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Purpose: This study identified kinematic and knee energetic variables that reduce the risk of non-contact anterior cruciate ligament (ACL) injury during single-leg landings from increasing vertical heights and horizontal distances., Methods: Nine subjects performed single-leg landings from takeoff platforms with vertical heights of 20, 40, and 60 cm onto a force plate. Subjects also performed single-leg landings from a 40 cm high takeoff platform placed at horizontal distances of 30, 50 and 70 cm from a force plate. Kinematic and kinetic data were measured., Results: Vertical height had a significant and positive effect on peak vertical ground reaction force (VGRF) (p<0.001), peak posterior ground reaction force (PGRF) (p=0.004), knee flexion angle (p=0.0043), trunk flexion angle (p=0.03), knee power (p<0.001) and knee work (p<0.001). There was also a significant and positive effect of horizontal distance on peak PGRF (p<0.001), ankle plantar flexion angle (p=0.008), hip flexion angle (p=0.007), and trunk flexion angle (p=0.001). At increasing vertical height, peak VGRF was significantly correlated to ankle plantar flexion and knee flexion angles (r=-0.77, p=0.02 and r=-0.78, p=0.01, respectively). At increasing horizontal distance, peak PGRF was significantly correlated to ankle plantar flexion angle, knee power and knee work (r=-0.85, p=0.003; r=0.67, p=0.04; and r=0.73, p=0.02, respectively)., Clinical Relevance: A better understanding of the risk factors to non-contact ACL injury during single-leg landings from increasing vertical heights and horizontal distances can aid in the design of injury prevention regimen., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: Full recovery in muscle strength and functional performance may not be achieved after ACL-injury., Aim: The aim of this study is to investigate loading patterns during jumping, muscle function and functional performance in ACL-reconstructed patients and to investigate the origin of between-limb asymmetry by means of a 3-dimensional movement analysis. Design is cross-sectional., Methods: 23 ACL-reconstructed men (27.2±7.5 years, BMI: 25.4±3.2) 27±7 month post-surgery and 25 matched controls (27.2±5.4 years, BMI: 24.1±1.8) were included. Participants performed (i) bilateral and (ii) unilateral counter movement jumps (CMJ). A 3-D movement analysis was performed by a six-camera Vicon MX-system. Subsequently, jump height (JH), knee joint range of motion (ROM), peak and mean sagittal knee moments were analyzed (iii) one-leg maximal jump for distance was performed, and (iv) maximal unilateral isometric knee extensor and flexor strength (MVC) were measured using stabilized dynamometry., Results: No in-between group differences in age or BMI were observed. CMJ: Between-limb asymmetry ratios for ROM differed (p<0.01) between patients and controls in both types of CMJ (96.1% vs. 102.6% and 87.0% vs. 99.9% in bilateral and single-leg CMJs, respectively). Jump for distance: Patients demonstrated greater (p<0.01) asymmetry for jump length (92.9% vs. 98.6%). MVC: Asymmetry in hamstring MVC was greater (p<0.001) for patients than controls (77.4% vs. 101.3%)., Conclusions: ACL-patients showed reduced function of the operated leg~2 years post ACL-reconstruction, especially for hamstring MVC. Hamstrings are important protagonists to the ACL, thus representing a potential risk factor for secondary ACL-rupture and/or osteoarthritis., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Insufficient hip flexibility, a limiting factor for lower extremity rotation, can cause great rotational stress and consequent injury to the knees and ankles. A limited range of motion (ROM) of the hip might be associated with increased risk of non-contact anterior cruciate ligament (ACL) injury. We investigated the association between the risk of non-contact ACL injured student athletes and limitations of hip ROM., Methods: A case-control study was conducted at an orthopaedic clinic in Japan. Cases included all patients with non-contact ACL injury and without known marked alignment abnormalities who visited the orthopaedic clinic during 2000-2008. Controls included all patients with non-ACL sports-related injuries who visited the same clinic in 2000. The adjusted odds ratio of ROM of the hip was evaluated for non-contact ACL injury risk., Results: These cases were 44 ACL cases and 123 controls aged 13-17 years. The odds ratios (ORs) of internal and external rotations of hip ROMs were adjusted for age, sex, BMI, type of sports and hip ROM (flexion, extension, adduction, abduction). The adjusted ORs for a 10° increase of the sum of the right and left internal hip rotations were 0.18 (95% confidence interval [CI], 0.10-0.34, p<0.0001), and 0.23 (95% CI, 0.14-0.39, p<0.0001) for external rotations, and the observed ORs were small., Conclusions: Data obtained from this small sample indicate that limited hip rotation ROMs in young athletes have the possibility of association with increased risk of non-contact ACL injury., Level of Evidence: III - case-control study., (© 2013.)

Background: Quadriceps strength deficits are ubiquitous after anterior cruciate ligament (ACL) injury. Deficits prior to surgery can influence knee function post-operatively. Inhibition contributes to quadriceps strength deficits after an ACL injury. Body mass index, meniscal injury, and sex influence functional outcomes after ACL reconstruction. The purpose of this study is to examine the relationship of pre-operative quadriceps strength and post-operative knee function and to investigate how other pre-operative factors may influence this relationship., Methods: After an ACL injury, subjects received pre-operative rehabilitation and performed quadriceps strength testing. Subjects underwent reconstruction and post-operative rehabilitation. Six months after ACL reconstruction, subjects completed the International Knee Documentation Committee 2000 subjective form (IKDC2000). Linear regression models were developed using IKDC2000 scores at 6 months after ACL reconstruction as the dependent variable., Results: Fifty-five subjects had complete pre-operative data and IKDC2000 scores at 6 months after ACL reconstruction. Pre-operative involved quadriceps strength was a significant predictor for IKDC2000 scores 6 months after ACL reconstruction. Sex, meniscal injury, pre-operative BMI, and pre-operative involved quadriceps activation ratio were not significant predictors in the regression model., Conclusions: Pre-operative quadriceps strength can predict IKDC2000 scores 6 months after ACL reconstruction. Deficits in pre-operative quadriceps strength influence self-reported function 6 months after surgery. Factors that are known to influence quadriceps strength and self-reported outcomes do not influence the relationship between pre-operative quadriceps strength and post-operative IKDC2000 scores., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Introduction: Coactivation of the hamstring muscles during dynamic knee extension may compensate for increased knee joint laxity in anterior cruciate ligament (ACL) deficient subjects. This study examined if antagonist muscle coactivation during maximal dynamic knee extension was elevated in subjects with anterior cruciate ligament (ACL) deficiency compared to age-matched healthy controls., Methods: Electromyography (EMG) and net knee joint moments were recorded during maximal concentric quadriceps and eccentric hamstring contractions, performed in an isokinetic dynamometer (ROM: 90-10°, angular speed: 30°/s). Hamstring antagonist EMG recorded during concentric quadriceps contraction was converted into antagonist moment based on the EMG-moment relationship observed during eccentric agonist contractions., Results: The magnitude of antagonist hamstring EMG was 65.5% higher in ACL deficient subjects compared to healthy controls (p<0.05). Likewise, antagonist hamstring moment expressed in percentage of the measured net extension moment was elevated in ACL deficient subjects (56 ± 8 to 30 ± 6%) compared to controls (36 ± 5 to 19 ± 2%) at 20-50° of knee flexion (0°=full extension) (p<0.05)., Discussion: The results showed a marked increase in hamstring coactivation towards more extended joint positions. Notably, this progressive rise in coactivation was greater in ACL deficient subjects, which may reflect a compensatory strategy to provide stability to the knee joint in the anterior-posterior plane during isolated knee extension. The present study encourages further investigations of hamstring coactivation in ACL deficient subjects., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Introduction: Interference screws used in fixation of anterior cruciate ligament (ACL) hamstring grafts create mechanical hold by forcing the graft into frictional contact with the bone tunnel. We analyzed the resultant graft-tunnel contact pressure using an in vitro model of human cadaver 8mm hamstring grafts., Methods: Contact characteristics were assessed using both pressure sensitive films and a force sensor. Two screw sizes were investigated (8 and 9 mm in an 8mm Sawbone tunnel), both with and without a bone wedge between graft and screw. Separately, time dependent relaxation of contact force was recorded over a one hour epoch and associated tendon water loss was measured. Pullout testing of 8mm tendon grafts from 8mm holes in Sawbone and porcine femora were performed after 1 min and 1h., Results: During screw insertion, measured peak pressures (>40 MPa) exceeded the compressive failure stress of metaphyseal bone by more than an order of magnitude. Using a bone wedge between tendon and screw reduced local peak pressure by 85% but produced also inferior average contact pressure. In all approaches, initially achieved graft contact pressure rapidly decreased to approximately 25% within 30 min. Pullout strength was significantly reduced after 1h in comparison to 1 min in porcine bone as well as Sawbone., Conclusion: Viscoelastic adaptation of the tendon is severe and critically reduces effective graft-bone contact pressure. Consideration of this newly recognized effect may open new and improved approaches for tendon graft fixation., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The ability to quantify in vivo femoro-tibial relations in the knee holds great advantage to further patient care. There is little consensus on the optimal weight-bearing environment and measurement method for MRI assessment of in vivo knee kinematics. This study set out to establish the optimal method of measuring femoro-tibial relations in an upright, weight-bearing environment in normal individuals and those with ACL deficiency. Upright, load bearing, MRI scans of both knees were evaluated by two methods, flexion facet centre (FFC) and femoro-tibial contact point (FTCP), in order to establish femoro-tibial relations in the sagittal plane throughout different angles of knee flexion. A group of healthy volunteers (n=5) and a group with unilateral ACL insufficiency (n=8) were studied. Abnormal femoro-tibial relations were found in all ACL-deficient knees (n=8): the lateral tibial plateau was anteriorly displaced in extension and early flexion and, coupled with smaller changes in the medical compartment, this constitutes internal rotation of the tibia relative to the femur in early flexion. This study found that the FFC measurement technique holds an advantage over the FTCP technique in terms of validity, repeatability and ease of measurements, allowing detection of kinematic changes such as tibial internal rotation in early flexion in ACL-deficient knees in an upright weight-bearing model. We propose that FFC measurement in an upright, weight-bearing position is a reliable and representative tool for the assessment of femoro-tibial movement., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The purposes of this study were to analyze the results of revision ACL reconstruction, and to determine the effects of pre-revision combined injuries, degenerative changes, and post-revision magnetic resonance imaging (MRI) findings on clinical results. Forty patients (41 operations) were enrolled in this study. Clinical results and stabilities were evaluated. Radiological results were evaluated using Fairbank scale. For the subgroup analysis, Fairbank scale and preoperative combined injuries were used. Follow-up MRIs were also available for 31(75.6%) patients and we searched for relations between MRI findings and clinical results. Significant improvements in subjective, objective scores (p<0.0001), and stability (p<0.0001) were observed between pre-revision surgery and final follow-up results. In the subgroup analysis according to the degenerative change, the mild group achieved better clinical results than the severe group (p=0.015 and 0.035, respectively). In the subgroup analysis according to the combined injuries, no significant difference was observed between 2 groups in terms of final follow-up Lysholm and IKDC subjective scores (p=0.083 and 0.085, respectively). No relation was found between clinical or stability results and MRI findings (p=0.26~0.99). Our results show that the severities of combined injuries were not correlated with clinical results, but the severities of degenerative changes were correlated with clinical results and that results were better in the no or mildly degenerated group. We also found that MRI is helpful for evaluating revision ACL, but that no relation was found between clinical or stability results and MRI findings of the graft after revision surgery., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The aim of this study is to evaluate the midterm results of using Ligament Advanced Reinforcement System (LARS) artificial ligament for augmentation of the short (<15 cm length) and small-sized (3-4 mm) diameter for the gracilis and (4-5 mm) for the semitendinosus harvested hamstring tendons in anterior cruciate ligament (ACL) reconstruction, and to assess the knee stability, patient satisfaction and early- and midterm complications following surgery. A total of 112 patients were included in this study and were operated with arthroscopic ACL reconstruction using (augmented hamstring tendon graft with LARS) between January 2004 and December 2006. Assessment before and after the surgery include the history, clinical examination, modified international knee documentation committee score (IKDC), KT1000 measurements for clinical knee stability and osteoarthritis outcome score (KOOS) for patient satisfaction. Clinical results measured by IKDC evaluation, KT1000 and Lysholm scores showed significant postoperative values compared with the preoperative ones. Our findings suggest that at the end of a 5-year follow-up, augmented hamstring tendon graft with LARS artificial ligament is a useful, safe and satisfactory treatment option for ACL reconstruction in deficient knees with short- and small-sized harvested hamstring tendons, especially when an early return to high levels of sport activity is needed., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The objective of this study was to evaluate the effectiveness of hamstring (HT) autografts versus bone-patellar tendon-bone (BPTB) autografts for reconstruction of the anterior cruciate ligament (ACL). We searched the Cochrane Library, MEDLINE, EMBASE and the Chinese Biomedicine Database (CBM) for published randomised clinical trials (RCTs) relevant to ACL reconstruction comparing HT and BPTB autografts. Data analyses were performed with Cochrane Collaboration's RevMan 5.0. A total of 23 reports of 19 randomised controlled trials (RCTs) (1643 patients) met the inclusion criteria. Outcomes favouring BPTB autografts were found in terms of KT-1000 arithmometer values, negative rates of Lachman tests and negative rates of Pivot tests. Outcome measures that favoured HT autografts included anterior knee pain, kneeling pain and extension loss. There was no statistical difference of postoperative graft failure. Overall, postoperative complications of the knee joint were lower for HT autografts than for BPTB autografts, and BPTB autografts were superior to HT autografts in resuming stability of the knee joint, but four-strand HT combined with application of the modern endobutton HT graft-fixation technique could increase knee-joint stability., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Various anterior cruciate ligament (ACL) graft-fixation devices exist. In this in vitro study a comparison of biomechanical characteristics of the cross-pin and button type fixation devices under practical rehabilitation loads was done. Forty bovine knees and hoof extensor tendons were harvested. After disarticulation, the femoral end of an ACL was prepared with either fixation, using the extensor tendon as graft. The mechanical test was either a single load to failure or load to failure after cycling loads. Twenty specimens were loaded to failure at a rate of 1mm/s, remaining specimens were cycled between 50 and 250 N for 1000 cycles then failure tested in a similar manner. Results show that both forms of fixation are able to withstand loads that exceed those observed in performing functional activities. Activity-specific stiffness (loads comparable to walking, jogging and stair descent) was lower than linear stiffness for both endobutton and cross-pin, without prior cycling. After cycling, activity-specific stiffness increased to linear stiffness values for the cross-pin for all activities. Thus, suggesting that the cross-pin provides a more rigid fixation after initial implantation over a wider range of activities, which would theoretically permit a more aggressive rehabilitation protocol and possibly an earlier return to regular activity. In contrast, activity-specific stiffness increased above linear stiffness values for the endobutton only under heavier loads (jogging and stair descent). Dynamic stiffness was higher and displacement lower for cross-pin throughout the cycle test. These results indicate, in ACL reconstruction, that graft complex stiffness should be considered at relevant loads only., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The pivot shift test is the only clinical test which correlates with knee function following rupture of the ACL. A grade is given to the pivot shift in a subjective manner, leading to efforts to quantify the bone movements and correlate them to the grade. However, the dynamic and unconstrained nature of the manoeuvre introduces important kinematic variability. Our main objective was to develop a method to lessen the variability attributable to clinician technique, therefore increasing inter-grade differences. Three different orthopaedic surgeons each performed the pivot shift test on 12 subjects. Knee joint kinematics were recorded using electromagnetic motion capture devices. Inter-clinician variability was quantified and a method was developed to diminish it, using the angular velocity of flexion. This method was then applied to a larger population composed of 127 knees with various degrees of instability, evaluated by one of eight different orthopaedic surgeons. The clinical grades given by the clinicians were in almost perfect agreement (kappa=0.83). Normalization of kinematic parameters using the angular velocity of knee joint flexion produced by the clinicians reduced the intra-clinician variability by 20%, resulting in an intra-class correlation coefficient (ICC) of 0.52, up from 0.41 before normalization. This allowed for more significant differences between the grades of pivot shift. Simple normalisation of pivot shift kinematics using the angular velocity of flexion reduces clinician-related variability and allows for significant differences between the different grades. These results are an important step towards developing an objective measurement tool for the pivot shift phenomenon., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Investigating landing kinetics and neuromuscular control strategies during rapid deceleration movements is a prerequisite to understanding the non-contact mechanism of ACL injury. The purpose of this study was to quantify the effect of knee flexion angle on ground reaction forces, net knee joint moments, muscle co-contraction and lower extremity muscles during an impact-like, deceleration task. Ground reaction forces and knee joint moments were determined from video and force plate records of 10 healthy male subjects performing rapid deceleration single leg landings from a 10.5 cm height with different degrees of knee flexion at landing. Muscle co-contraction was based on muscle moments calculated from an EMG-to-moment processing model. Ground reaction forces and co-contraction indices decreased while knee extensor moments increased significantly with increased degrees of knee flexion at landing (all p<0.005). Higher ground reaction forces when landing in an extended knee position suggests they are a contributing factor in non-contact ACL injuries. Increased knee extensor moments and less co-contraction with flexed knee landings suggest that quadriceps overload may not be the primary cause of non-contact ACL injuries. The results bring into question the counterbalancing role of the hamstrings during dynamic movements. The soleus may be a valuable synergist stabilizing the tibia against anterior translation at landing. Movement strategies that lessen the propagation of reaction forces up the kinetic chain may help prevent non-contact ACL injuries. The relative interaction of all involved thigh and lower leg muscles, not just the quadriceps and hamstrings should be considered when interpreting non-contact ACL injury mechanisms., (Copyright 2010 Elsevier B.V. All rights reserved.)

The purpose of this study was to compare the clinical outcomes of rehabilitation after ACL reconstruction using a water-filled soft brace to those using a hard brace. The method used in this study was a prospective randomised clinical trial including 36 patients wearing a hard brace and 37 patients wearing a water-filled soft brace for 6 weeks after surgery. Preoperative and postoperative (seven examinations) clinical evaluation within a follow-up period of 1 year including effusion status, swelling and range of motion (ROM), IKDC 2000, KT1000 Arthrometer, Lysholm knee scoring scale and Tegner activity score. Mean values are presented with standard deviations. Data was analysed using descriptive statistics and Student's t-test for unpaired samples. Significantly less effusion was found in the soft brace group from 5 days (p=0.002) to 12 weeks (p<0.024) postoperative. Hard brace patients presented with significantly more extension deficit from 5 days (p=0.036) to 12 months (p=0.014) postoperative but no significant difference was detected in complete ROM, laxity or thigh atrophy at any follow-up examination. Patients treated with a soft brace had significantly higher IKDC subjective ratings at 6 weeks (p=0.02) up to 12 months after operation (p=0.002) and rated significantly higher in Tegner activity score (p=0.004) and Lysholm knee scoring scale (p=0.006) 6 and 12 months (p<0.001 for both scores) postoperatively. The water-filled soft brace was superior regarding effusion, swelling, extension deficit and patient-measured midterm outcome. The soft brace presents a safe, easy-to-use and effective alternative to the hard brace., (Copyright 2009 Elsevier B.V. All rights reserved.)

Artificial ligaments for ACL replacement have been widely used in the 1980s and early 1990s in orthopaedic surgery. Synthetic devices have been utilized either as a prosthetic material or as an augmentation for a biological ACL graft substitute. The initial enthusiasm surrounding the introduction of synthetic graft materials stemmed from their lack of donor morbidity, their abundant supply and significant strength of these devices. The disadvantages in long-term follow-up were found to be cross-infections, immunological responses, tunnels osteolysis, femural and tibial fractures, foreign-body synovitis and knee osteoarthritis. A total of 126 patients were treated with artificial ACL substitution with polyethylene terephthalate (PET) synthetic ligaments in our Institute between 1986 and 1990. Of the original group, 51 sportsmen aged 15 to 40 were followed-up at a mean of 19years (range 17.5 to 20.6years) after surgery. Assessment was made with KOOS and IKDC score, Tegner activity scale, clinical examination, KT-1000 arthrometer, and X-ray evaluation. Of the 51 patients followed-up, 27.5% were found to have ruptured their PET ligaments and 100% presented degenerative osteoarthritis at the X-ray evaluation according to Ahlbäck radiological classification of arthritis. The objective evaluation showed functional impairment in 29.4% with an average reduction of 3 points in the Tegner activity scale. The osteoarthritis observed in all patients prompted us to avoid the diffusion of this surgical technique. Although in theory well-conceived, studies have yet to substantiate the function of these augmentation devices or to show clinical better results than those achieved with isolated autograft or allograft ACL substitutes., (Copyright 2009 Elsevier B.V. All rights reserved.)

Proprioception and muscle strength are both reported to influence single-limb stance balance in patients with chronic anterior cruciate ligament (ACL) injuries. However, the effects of these parameters on dynamic stance balance in such patients are currently unknown. This study was undertaken to ascertain whether proprioception, muscle strength, and knee laxity are correlated with dynamic standing balance in patients with ACL deficiency. Ten young men with unilateral ACL deficiency participated in this study. The mean time interval from the injury to the study was 12.8 months. Knee laxity measurements, passive re-positioning (PRP) and threshold for detection of passive motion (TTDPM) proprioception tests, quadriceps and hamstring muscle strength tests, and dynamic single-limb balance tests were performed for both injured and uninjured limbs. Significant differences between the injured and uninjured sides were observed for all test parameters. As independent variables, knee laxity, PRP proprioception, and muscle strength did not correlate with dynamic standing balance for the injured limb. However, a significant positive correlation (P<0.05) between TTDPM proprioception and dynamic single-limb stance balance was observed for the injured limb. To improve dynamic single-limb stance balance in patients with ACL injuries, training in TTDPM proprioceptive ability is recommended as the most important initial approach for such patients.

Background and Purpose: Descent of a ramp has been shown to induce large anterior shear forces on the knee joint. Compensatory muscle responses observed in individuals following an anterior cruciate ligament (ACL) injury are believed to be adopted for the purpose of reducing these forces at the knee, in the absence of the mechanical restraint previously provided by the ACL. As such, examining the kinematics and muscle responses of ACL deficient individuals during ramp descent may provide further insight into strategies used by this population to compensate for anterior shear forces at the knee., Methods: Eight ACL deficient individuals were studied, in comparison to a healthy CONTROL group (N=8), during the descent of a 20 degrees ramp. Kinematics and electromyography were recorded for the injured lower limb of ACLD and matched limb of healthy control individuals., Results: ACLD individuals produced altered knee kinematics at heel contact only. Knee motion through stance and swing were similar to CONTROL individuals. ACLD individuals produced significantly greater vastus lateralis and gastrocnemius total muscle activity, but decreased total biceps femoris activity. No significant differences were observed for the timing of peak muscle activity or the magnitude at this point between ACLD and CONTROL., Discussion and Conclusion: Greater total muscle activity of vastus lateralis implies that greater force contributions from this muscle were used by ACLD in comparison to CONTROL in response to the ramp. These observations reinforce that quadriceps avoidance is not used by ACLD individuals to reduce anterior shear forces at the knee joint. Rather, vastus lateralis may be used to reduce internal tibial rotation in extreme loading situations.

In the absence of anterior cruciate ligament (ACL), secondary restraints such as menisci, ligaments, and tendons restrict anterior knee laxity. Strain detection at these sites could define the contribution of this alternative signalling system to knee proprioception after ACL injury. The hypothesis in this study questions if measurements of anterior tibial translation (ATT) from surface strain gauges on the insertions of the medial collateral ligament (MCL) and the patellar tendon (PT) are sufficiently sensitive and specific to differentiate normal, stable knees from acutely unstable knees due to ACL section. Twelve cats received miniaturized strain gauges on the surface of MCL and PT distal insertions. A purpose-made receiver transformed into measurements any voltage variation obtained during passive knee flexion-extension and anterior tibial translation manoeuvres. Variables under evaluation included first peak latency, normalized amplitude, and slope of voltage along time. Femorotibial displacements were video recorded, digitized, and used as the ATT reference. The proposed system detected significant changes in the slope of the voltage/time signal, with higher specificity and sensitivity during ATT after experimental ACL section. Changes were not significant during flexion or extension. It was found that a pattern of earlier and more intense strain in MCL and PT distal insertions was found during ATT in the ACL deficient knee. Enhanced pattern recognition learning from these structures could be a future target for proprioceptive training after ACL injury.

Rupture of the anterior cruciate ligament (ACL) results in increased tibiofemoral laxity in the knee, thereby ultimately resulting in knee instability and dysfunction. However, ACL rupture does not automatically infer functional impairment and instability as confirmed by the ACL deficient (ACLD) coper, who can resume pre-morbid activity levels. Alternatively, an authentic ACLD non-coper is unable to return to pre-injury levels of activity due to repeated incidents of giving-way. Little is known as to the contributory factors, which allows copers dynamic stability and render non-copers functionally impaired. This systematic literature review aims to examine the evidence presented by relevant trials in order to identify measurement tools, which could differentiate ACLD copers and non-copers. A literature search found nine trials; four adhered to the inclusion criteria of this review. Consensus was achieved within the studies that laxity measurements and IKDC ratings are incapable of distinguishing the functional status of the ACLD patient. Alternatively, Lysholm, KOS-Sport, KOS-ADL and Global Knee Function Rating Scores were regarded as capable of discriminating between ACLD copers and non-copers. Disagreement existed as to the efficacy of the Quadriceps Index and the single leg hop in categorising the ACLD patient according to function level. It was concluded that no single measurement tool is sufficient in determining the functional status of the ACLD individual. Consequently, a collaboration of tests is recommended, specifically incorporating the KOS-Sport, Global Knee Function Rating, hop tests and Quadriceps Index.

We report a case of tibial plateau fracture after previous anterior cruciate ligament (ACL) reconstruction using patellar tendon autograft and bioabsorbable screws 4 years previously. The fracture occurred through the tibial tunnel. The interference screw had undergone complete resorption and the tunnel widening had increased. The resorption of the interference screw did not simultaneously promote and foster the growth of surrounding bone tissue. Therefore, the area of reactive tissue left by the screw resorption in an enlarged bone tunnel may lead to vulnerability of the tibial plateau. Stress risers would occur following ACL reconstruction if either resorption is not complete or bony integration is not complete.

Tibial plateau fractures following anterior cruciate ligament (ACL) reconstruction are extremely rare. This is the first reported case of a tibial plateau fracture following four-strand gracilis-semitendinosus autograft ACL reconstruction. The tibial tunnel alone may behave as a stress riser which can significantly reduce bone strength.

Tibiofemoral instability following total knee replacement has received little attention. However it is a cause of early and late failure and usually requires revision surgery. Several factors may be implicated including improper soft tissue balancing, flexion-extension gap mismatch and acute ligamentous injuries. Meticulous surgical technique and proper prosthetic selection at the primary procedure avoids this complication.

This study evaluates the structural properties of the femur-anterior cruciate ligament (ACL) graft-tibia complex, comparing different graft fixation techniques in sheep knees. Four fixation devices were tested both for femoral fixation (Transfix, absorbable screw, RCI screw and Linx-HT) and tibial fixation (bone plug with metal screw, absorbable screw with staple, RCI screw and cancellous screw with spiked washer). The graft used for ACL reconstruction was fresh ovine doubled Achilles tendon (DAT). Femurs and tibias were tested separately. Two mechanical test series were performed on the specimens: a load-to-failure test and a cyclic loading test. On the femoral side, transcondylar screw showed the greatest fixation strength and stiffness and the lowest elongation at cyclic loading. Tibial fixation complexes seemed to have poorer structural properties in comparison to femoral fixation. Among the tibial fixation devices, absorbable screw with staple fixation showed the greatest strength and stiffness. Spiked washer fixation showed the greatest elongation under cyclic loading.