Synthesis of silver @hydroxyapatite nanoparticles based biocomposite and their assessment for viability of Osseointegration for rabbit knee joint anterior cruciate ligament rehabilitation.

In this examination, chitosan-silk fibroin/polyethylene terephthalate (CTS-SF/PET), chitosan-silk fibroin/polyethylene terephthalate/hydroxyapatite (CTS-SF/PET/HAP) and chitosan-silk fibroin/polyethylene terephthalate/Silver @hydroxyapatite (CTS-SF/PET/Ag@HAP) scaffolds were prepared by utilizing the plasma splashing procedure. Field emission scanning electron microscopy (FESEM) results demonstrated that the outside of the PET covered with HAP nanoparticles. The cell viability results demonstrated that the number of Mesenchymal stem cells (MSCs) primarily spread out on CTS-SF/PET/Ag@HAP. RT-PCR results demonstrated that there was an upregulated mRNA articulation of osseous development-related properties in the CTS-SF/PET/Ag@HAP composite. The in vivo rabbit animal assessment scores of the CTS-SF/PET/Ag@HAP composite were significantly better than those of the CTS-SF/PET at 1 to 3 months. Both in-vivo and in-vitro results exhibited in this investigation recommend that the cytocompatibility and osseointegration of CTS-SF/PET/Ag@HAP tendon were fundamentally improved by expanding the multiplication of cells and up-regulating the outflow of tendon development-related properties. In conclusion, the CTS-SF/PET/Ag@HAP tendon is a promising candidate for Anterior Cruciate Ligament (ACL) replacement in the future.

Gait screening of a population of young, healthy athletes by means of a portable, low-cost device unveils hidden left-right asymmetries in both quadriceps and anterior cruciate ligament forces.

OBJECTIVE: The present study reports the on-field screening of a population of young soccer players in the pursuit of alterations in gait using a portable and low-cost gait analysis system composed of a Wii Balance Board and a webcam. RESULTS: Recordings of motion of the lower extremities along with vertical ground reaction force (GRF) were used to quantify coefficients of symmetry for the overall GRF and the forces exerted by the quadriceps femori and acting on the anterior cruciate ligament (ACL). Data show that, in face of a quite homogeneous symmetry of GRF during left and right stance phases of gait, quadriceps and ACL exert and are subjected to left-right asymmetrical forces that might prelude, especially in young athletes, later alterations of gait.

In vivo assessment of the interaction of patellar tendon tibial shaft angle and anterior cruciate ligament elongation during flexion.

A potential cause of non-contact anterior cruciate ligament (ACL) injury is landing on an extended knee. In line with this hypothesis, studies have shown that the ACL is elongated with decreasing knee flexion angle. Furthermore, at low flexion angles the patellar tendon is oriented to increase the anterior shear component of force acting on the tibia. This indicates that knee extension represents a position in which the ACL is taut, and thus may have an increased propensity for injury, particularly in the presence of excessive force acting via the patellar tendon. However, there is very little in vivo data to describe how patellar tendon orientation and ACL elongation interact during flexion. Therefore, this study measured the patellar tendon tibial shaft angle (indicative of the relative magnitude of the shear component of force acting via the patellar tendon) and ACL length in vivo as subjects performed a quasi-static lunge at varying knee flexion angles. Spearman rho rank correlations within each individual revealed that flexion angles were inversely correlated to both ACL length (rho = -0.94 ±â€¯0.07, mean ±â€¯standard deviation, p < 0.05) and patellar tendon tibial shaft angle (rho = -0.99 ±â€¯0.01, p < 0.05). These findings indicate that when the knee is extended, the ACL is both elongated and the patellar tendon tibial shaft angle is increased, resulting in a relative increase in anterior shear force on the tibia acting via the patellar tendon. Therefore, these data support the hypothesis that landing with the knee in extension is a high risk scenario for ACL injury.

In vivo anterior cruciate ligament length pattern assessment secondary to differences in the femoral attachment under loading condition using image-matching techniques.

BACKGROUND: The anterior cruciate ligament is composed of two functional bundles and is crucial for knee function. There is limited understanding of the role of each individual bundle and the influence on length pattern due to difference in bone tunnel position under loading conditions throughout the range of motion. We measured point to point length between the femoral and tibial footprints of the ligament throughout the range of motion in normal knees, under normal loading conditions, and investigated length pattern changes secondary to differences in the femoral footprint. We hypothesized that anteromedial and posterolateral bundles have complementary roles, and the ligament length pattern is influenced by the footprint position. METHODS: We studied the squat movements of six healthy knees and measured point to point footprint distance. The footprint distances were measured after changing them to be 10% lower, 10% shallower, and both 10% lower and shallower than the defined anatomical femoral footprint. RESULTS: Average length changes of 12.0 and 14.1 mm from maximum extension (10°) to deep flexion (150°) were observed when the anteromedial and posterolateral bundles were defined by the default anatomical position. Maximum and minimum length were reached during full extension and flexion for both the anteromedial and posterolateral bundles, respectively. At 10% lower, length increased 2.2 mm over the default value in both the anteromedial and posterolateral lengths. At 10% shallower, decreases of 4.1 mm and 3.9 mm were observed compared with the default anteromedial and posterolateral lengths, respectively. In the 10% lower and 10% shallower position, anteromedial and posterolateral lengths decreased 2.1 mm and 1.9 mm compared with the default value, respectively. CONCLUSIONS: The anteromedial and posterolateral bundles have a complementary role. Femoral footprint position defined in the lower direction leads to stronger tension during extension, while the higher and shallower direction leads to isometry during flexion, and the deeper direction leads to laxity during flexion. The target bone tunnel position is that the anteromedial bundle should not to be too low and too deep to maintain function of bundle with less change in length. In addition, the posterolateral bundle should be somewhat lower and/or deeper than the anteromedial, with the expectation that it will function to induce stronger tension at the extended position. However, we should avoid lower position when we cannot prepare a sufficient diameter of reconstructed bundle to avoid re-injury due to excessive tension.

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

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

Biomechanical Assessment of the Anterolateral Ligament of the Knee: A Secondary Restraint in Simulated Tests of the Pivot Shift and of Anterior Stability.

BACKGROUND: Injury to the lateral capsular tissues of the knee may accompany rupture of the anterior cruciate ligament (ACL). A distinct lateral structure, the anterolateral ligament, has been identified, and reconstruction strategies for this tissue in combination with ACL reconstruction have been proposed. However, the biomechanical function of the anterolateral ligament is not well understood. Thus, this study had two research questions: (1) What is the contribution of the anterolateral ligament to knee stability in the ACL-sectioned knee? (2) Does the anterolateral ligament bear increased load in the absence of the ACL? METHODS: Twelve cadaveric knees from donors who were a mean (and standard deviation) of 43 ± 15 years old at the time of death were loaded using a robotic manipulator to simulate clinical tests of the pivot shift and anterior stability. Motions were recorded with the ACL intact, with the ACL sectioned, and with both the ACL and anterolateral ligament sectioned. In situ loads borne by the ACL and anterolateral ligament in the ACL-intact knee and borne by the anterolateral ligament in the ACL-sectioned knee were determined. RESULTS: Sectioning the anterolateral ligament in the ACL-sectioned knee led to mean increases of 2 to 3 mm in anterior tibial translation in both anterior stability and simulated pivot-shift tests. In the ACL-intact knee, the load borne by the anterolateral ligament was a mean of ≤10.2 N in response to anterior loads and <17 N in response to the simulated pivot shift. In the ACL-sectioned knee, the load borne by the anterolateral ligament increased on average to <55% of the load normally borne by the ACL in the intact knee. However, in the ACL-sectioned knee, the anterolateral ligament engaged only after the tibia translated beyond the physiologic limits of motion of the ACL-intact knee. CONCLUSIONS: The anterolateral ligament is a secondary stabilizer compared with the ACL for the simulated Lachman, anterior drawer, and pivot shift examinations. CLINICAL RELEVANCE: Since the anterolateral ligament engages only during pathologic ranges of tibial translation, there is a limited need for anatomical reconstruction of the anterolateral ligament in a well-functioning ACL-reconstructed knee.

An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 2: Anterolateral Ligament Reconstruction Combined With Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Recent biomechanical studies have demonstrated that an extra-articular lateral knee structure, most recently referred to as the anterolateral ligament (ALL), contributes to overall rotational stability of the knee. However, the effect of anatomic ALL reconstruction (ALLR) in the setting of anterior cruciate ligament (ACL) reconstruction (ACLR) has not been biomechanically investigated or validated. PURPOSE/HYPOTHESIS: The purpose of this study was to investigate the biomechanical function of anatomic ALLR in the setting of a combined ACL and ALL injury. More specifically, this investigation focused on the effect of ALLR on resultant rotatory stability when performed in combination with concomitant ACLR. It was hypothesized that ALLR would significantly reduce internal rotation and axial plane translation laxity during a simulated pivot-shift test compared with isolated ACLR. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen cadaveric knees were evaluated with a 6 degrees of freedom robotic system. Knee kinematics were evaluated with simulated clinical examinations including a simulated pivot-shift test consisting of coupled 10-N·m valgus and 5-N·m internal rotation torques, a 5-N·m internal rotation torque, and an 88-N anterior tibial load. Kinematic differences between ACLR with an intact ALL, ACLR with ALLR, and ACLR with a deficient ALL were compared with the intact state. Single-bundle ACLR tunnels and ALLR tunnels were placed anatomically according to previous quantitative anatomic attachment descriptions. RESULTS: Combined anatomic ALLR and ACLR significantly improved the rotatory stability of the knee compared with isolated ACLR in the face of a concurrent ALL deficiency. During a simulated pivot-shift test, ALLR significantly reduced internal rotation and axial plane tibial translation when compared with ACLR with an ALL deficiency. Isolated ACLR for the treatment of a combined ACL and ALL injury was not able to restore stability of the knee, resulting in a significant increase in residual internal rotation laxity. ALLR did not affect anterior tibial translation; no significant differences were observed between the varying ALL conditions with ACLR except between ACLR with an intact ALL and ACLR with a deficient ALL at 0° of flexion. CONCLUSION: In the face of a combined ACL and ALL deficiency, concurrent ACLR and ALLR significantly improved the rotatory stability of the knee compared with solely reconstructing the ACL. CLINICAL RELEVANCE: Significant increases in residual internal rotation and laxity during the pivot-shift test may exist in both acute and chronic settings of an ACL deficiency and in patients treated with isolated ACLR for a combined ACL and ALL deficiency. For this subset of patients, surgical treatment of the ALL, in addition to ACLR, should be considered to restore knee stability.

An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 1: Secondary Role of the Anterolateral Ligament in the Setting of an Anterior Cruciate Ligament Injury.

BACKGROUND: Recent investigations have described the structural and functional behavior of the anterolateral ligament (ALL) of the knee through pull-apart and isolated sectioning studies. However, the secondary stabilizing role of the ALL in the setting of a complete anterior cruciate ligament (ACL) tear has not been fully defined for common simulated clinical examinations, such as the pivot-shift, anterior drawer, and internal rotation tests. HYPOTHESIS: Combined sectioning of the ALL and ACL would lead to increased internal rotation and increased axial plane translation during a pivot-shift test when compared with isolated sectioning of the ACL. STUDY DESIGN: Controlled laboratory study. METHODS: Ten fresh-frozen human cadaveric knees were subjected to a simulated pivot-shift test with coupled 10-N·m valgus and 5-N·m internal rotation torques from 0° to 60° of knee flexion and a 5-N·m internal rotation torque and an 88-N anterior tibial load, both from 0° to 120° of knee flexion via a 6 degrees of freedom robotic system. Kinematic changes were measured and compared with the intact state for isolated sectioning of the ACL and combined sectioning of the ACL and ALL. RESULTS: Combined sectioning of the ACL and ALL resulted in a significant increase in axial plane tibial translation during a simulated pivot shift at 0°, 15°, 30°, and 60° of knee flexion and a significant increase in internal rotation at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120° when compared with the intact and ACL-deficient states. Based on the model results, ALL sectioning resulted in an additional 2.1 mm (95% CI, 1.4-2.9 mm; P < .001) of axial plane translation during the pivot shift when compared with ACL-only sectioning, when pooling evidence over all flexion angles. Likewise, when subjected to IR torque, the ACL+ALL-deficient state resulted in an additional 3.2° of internal rotation (95% CI, 2.4°-4.1°; P < .001) versus the intact state, and the additional sectioning of the ALL increased internal rotation by 2.7° (95% CI, 1.8°-3.6°; P < .001) versus the ACL-deficient state. CONCLUSION: The results of this study confirm the ALL as an important lateral knee structure that provides rotatory stability to the knee. Specifically, the ALL was a significant secondary stabilizer throughout flexion during an applied internal rotation torque and simulated pivot-shift test in the context of an ACL-deficient knee. CLINICAL RELEVANCE: Residual internal rotation and a positive pivot shift after ACL reconstruction may be attributed to ALL injury. For these patients, surgical treatment of an ALL tear may be considered.

A phenomenological contact model: Understanding the graft-tunnel interaction in anterior cruciate ligament reconstructive surgery.

In this paper, we sought to expand the fidelity of a validated model of the anterior cruciate ligament reconstruction (ACL-R) procedure by incorporating a stick-slip contact model with linear pressure-overclosure relationship at the interface. The suggested model is characterized by three unknown parameters, friction coefficient, shear stress softening and contact stiffness. In the absence of any isolated experiments exploring the graft-tunnel interactions during an aggregate joint load, the calibration data used in this study are derived from a reported biomechanical study. A Bayesian calibration procedure was employed to find the unknown probability distribution function (PDF) of these contact parameters. Initially, the response surface approximations of the predicted graft forces from laxity test simulations was adopted to estimate the likelihood of noisy experimental data reported in the literature. Then, the wide domain of contact parameters was sampled sequentially based on the Marcov Chain Monte Carlo (MCMC) method with acceptance-rejection criteria to search for population of samples in significantly narrower domain of unknown parameters that are associated with the highest occurrence likelihood of noisy experimental data. Our simulations with calibrated contact parameters indicate that pre-tensioning applied at 30° of flexion leads to larger graft force after the joint is fully extended compared to the graft force when the same pre-tensioning force is applied at full extension. Moreover, regardless of the pre-tensioning force, the graft-tunnel contact pressure is larger when the fixation of the graft is performed at full extension, increasing with the pre-tensioning force.

3-D kinematics and neuromuscular signals' integration for post ACL reconstruction recovery assessment.

An intelligent recovery classification and monitoring system (IRCMS) for post Anterior Cruciate Ligament (ACL) reconstruction has been developed in this study. This system provides an objective assessment and monitoring of the rehabilitation progress by integrating 3-D kinematics and neuromuscular signals recorded through wearable motion and electromyography sensors, respectively. The data from a group of healthy and ACL reconstructed subjects were collected for normal/brisk walking (4-6km/h) and single leg balance (eyes open and eyes closed) testing activities. Fuzzy clustering and fuzzy nearest neighbor methods have been used to classify the collected data into different groups for each activity. The classification accuracy of the system is found to be 94.49% for 4 km/h walking speed, 95.41% for 5 km/h walking speed, 96.00% for 6 km/h walking speed, 94.44% for single leg balance testing with eyes open and 95.83% for single leg balance testing with eyes closed. The recovery status of a subject is evaluated based on different activities assessed and the overall assessment is done using Choquet integral fusion technique. Further, biofeedback mechanism has been developed using a visual monitoring system which provides the variations in strength/activation of knee flexors/extensors and 3-D joint kinematics. This integrated system can be used as an assistive tool by sports trainers, coaches and clinicians for monitoring overall progress of athletes' rehabilitation and classifying their recovery stage for multiple activities.

The assessment of postural control and the influence of a secondary task in people with anterior cruciate ligament reconstructed knees using a Nintendo Wii Balance Board.

BACKGROUND: Postural control impairments may persist following anterior cruciate ligament (ACL) reconstruction. The effect of a secondary task on postural control has, however, not been determined. The purpose of this case-control study was to compare postural control in patients following ACL reconstruction with healthy individuals with and without a secondary task. PARTICIPANTS: 45 patients (30 men and 15 women) participated at least 6 months following primary ACL reconstruction surgery. Participants were individually matched by age, gender and sports activity to healthy controls. MATERIALS: Postural control was measured using a Nintendo Wii Balance Board and customised software during static single-leg stance and with the addition of a secondary task. The secondary task required participants to match the movement of an oscillating marker by adducting and abducting their arm. MAIN OUTCOME MEASURES: Centre of pressure (CoP) path length in both medial-lateral and anterior-posterior directions, and CoP total path length. RESULTS: When compared with the control group, the anterior-posterior path length significantly increased in the ACL reconstruction patients' operated (12.3%, p=0.02) and non-operated limbs (12.8%, p=0.02) for the single-task condition, and the non-operated limb (11.5%, p=0.006) for the secondary task condition. The addition of a secondary task significantly increased CoP path lengths in all measures (p<0.001), although the magnitude of the increase was similar in both the ACL reconstruction and control groups. DISCUSSION: ACL reconstruction patients showed a reduced ability in both limbs to control the movement of the body in the anterior-posterior direction. The secondary task affected postural control by comparable amounts in patients after ACL reconstruction and healthy controls. Devices for the objective measurement of postural control, such as the one used in this study, may help clinicians to more accurately identify patients with deficits who may benefit from targeted neuromuscular training programs.

[Functional assessment of the different types of anterior cruciate ligament plasty used at the Xoco General Hospital Arthroscopy Service]. / Valoración funcional de los diferentes tipos de plastía del ligamento cruzado anterior empleados en el Servicio de Artroscopía del Hospital General Xoco.

INTRODUCTION: Currently, anterior cruciate ligament lesions have an increased frequency; their management is predominantly surgical; there are several functional assessment systems. MATERIAL AND METHODS: We used the IKDC (International Knee Documentation Committee) functional assessment in patients who underwent anterior cruciate ligament reconstruction at the Xoco Hospital Arthroscopy Service. RESULTS: A total of 73 patients underwent functional assessment; 43 underwent bone-tendon-bone (BTB) repair with patellar tendon graft and 30 underwent repair with pes anserinus tendon graft (T4). In the former group 39 patients had favorable results and 4 unfavorable results; in the latter group 27 patients had favorable results and 3 unfavorable results. DISCUSSION: The results found do not differ significantly between both groups, something that is in agreement with the reviewed literature. The study should be continued with a larger sample size to eliminate variables and obtain more reliable results.

The effect of connective tissue material uncertainties on knee joint mechanics under isolated loading conditions.

Although variability in connective tissue parameters is widely reported and recognized, systematic examination of the effect of such parametric uncertainties on predictions derived from a full anatomical joint model is lacking. As such, a sensitivity analysis was performed to consider the behavior of a three-dimensional, non-linear, finite element knee model with connective tissue material parameters that varied within a given interval. The model included the coupled mechanics of the tibio-femoral and patello-femoral degrees of freedom. Seven primary connective tissues modeled as non-linear continua, articular cartilages described by a linear elastic model, and menisci modeled as transverse isotropic elastic materials were included. In this study, a multi-factorial global sensitivity analysis is proposed, which can detect the contribution of influential material parameters while maintaining the potential effect of parametric interactions. To illustrate the effect of material uncertainties on model predictions, exemplar loading conditions reported in a number of isolated experimental paradigms were used. Our findings illustrated that the inclusion of material uncertainties in a coupled tibio-femoral and patello-femoral model reveals biomechanical interactions that otherwise would remain unknown. For example, our analysis revealed that the effect of anterior cruciate ligament parameter variations on the patello-femoral kinematic and kinetic response sensitivities was significantly larger, over a range of flexion angles, when compared to variations associated with material parameters of tissues intrinsic to the patello-femoral joint. We argue that the systematic sensitivity framework presented herein will help identify key material uncertainties that merit further research and provide insight on those uncertainties that may not be as relative to a given response.

Assessment of the "functional length" of the three bundles of the anterior cruciate ligament.

The objectives of the present study are to compare "functional length" between the three bundles of the anterior cruciate ligament (ACL) from extension to deep flexion and to perform a sensitivity study on the patterns of "functional length" change due to deviations in insertion site selection. Nine knees of healthy volunteers were examined using a horizontal open magnetic resonance apparatus with the knee at 0 degrees -150 degrees of flexion and created three-dimensional (3D) virtual models of the knee. The femoral and tibial attachment sites of the three ACL bundles were determined, and the distance between the attachment sites was automatically calculated as the "functional length" of each bundle in each position. After changing the attachment sites, computer simulation was performed to investigate in vivo "functional length" changes for the three bundles of the ACL in normal knee kinematics from extension to deep flexion. Three bundles statistically significantly changed in "functional length" during flexion/extension, while they were longest at full extension, and decreased with increasing knee flexion to 100 degrees . They were smallest at flexion of 100 degrees , with increase lengths with flexion deeper than 100 degrees . Deviation of 6 mm of insertion site beyond attachment area caused significant alteration in the pattern of "functional length" change of each bundle, while deviation of 3 mm within attachment area caused no significant difference. The "functional length" of the three ACL bundles was not isometric, not even the antero-medial bundle. The "functional length" might be of major importance in terms of the site of the ACL insertion. The "functional length" of multiple bundles of the ACL and the pattern of their changes are useful for not only graft choice and preparation but also knee angle and initial tension at graft fixation during multiple-bundle ACL reconstruction surgery.

Influence of anterior cruciate ligament bundles on knee kinematics: clinical assessment using computer-assisted navigation.

BACKGROUND: The synergistic functions of the anteromedial and posterolateral bundles of the anterior cruciate ligament in restraining anterior laxity are known. Cadaveric experiments have also suggested different functions of the 2 bundles in controlling a combined rotatory load simulating the pivot shift. HYPOTHESIS: The posterolateral bundle is important in controlling the coupled tibial axial rotation laxity occurring during clinical laxity tests performed in vivo, particularly the pivot-shift maneuver. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Twenty-one patients underwent navigated 2-bundle anterior cruciate ligament reconstruction. The navigation was additionally used to measure the knee kinematics in response to the anterior drawer test (performed at 90 degrees ), Lachman test (performed at 20 degrees of flexion), and pivot-shift test. Two sequential reconstruction protocols were used to assess the contribution of the anteromedial and posterolateral bundles to restraining tibial translations and coupled axial rotation occurring with the manually performed clinical laxity tests. RESULTS: Anterior tibial translation during the anterior drawer test was better restrained by anteromedial bundle reconstruction than by posterolateral bundle reconstruction. Conversely, posterolateral bundle reconstruction better restrained anterior tibial translation during the Lachman test. Both bundles contributed to the control of anterior laxity during the pivot shift. However, the posterolateral bundle was more important than was the anteromedial bundle in controlling the tibial rotational component (posterolateral bundle reconstruction caused a 53% reduction in tibial rotation laxity compared with a 42% reduction with anteromedial bundle reconstruction, P< .0001). CONCLUSION: This study provides objective, in vivo data about how the anteromedial and posterolateral bundles act differentially to stabilize the knee, particularly during the pivot shift. The posterolateral bundle was important in controlling not only anterior laxity toward knee extension but the rotational component of the pivot shift.

Novel method for the quantitative assessment of cell migration: a study on the motility of rabbit anterior cruciate (ACL) and medial collateral ligament (MCL) cells.

A novel method of quantitating cell migration has been proposed for the potential utilization of tissue engineered scaffolds. Applying Alt's conservation law to describe the motion of first passage ACL and MCL cells, we have developed a quantitative method to assess innate differences in the motility of cells from these two ligamentous tissues. In this study, first passage ACL and MCL cells were cultured from four mature New Zealand white rabbits. One side of the cell monolayer was scraped completely away to create a wound model. The cell moved into the cell-free area, and cell density profiles were analyzed at 6 h and 12 h. Values of the random motility coefficient (mu) were then estimated by curve fitting the 6 h and 12 h data to a mathematical model, derived from the conservation law of cell flux. During 6 h of incubation in medium supplemented with 1% FBS, MCL cells (mu(MCL) = 4.63 +/- 0.65 X 10(-6) mm(2)/sec) were significantly (p < 0.05) more mobile than ACL cells (mu(ACL) = 2.51 +/- 0.31 X 10(-6) mm(2)/sec). At 12 h, the MCL cells also appeared to move faster (mu(ACL) = 4.39 +/- 0.63 X 10(-6) mm(2)/sec, mu(MCL) = 6.59 +/- 1.47 X 10(-6) mm(2)/sec), but the difference was not statistically significant (p = 0.18). Exposure of the cells to growth factors PDGF-BB or bFGF for 6 h had no significant effect on the migration of the ACL and MCL cells. However, exposure of the ACL cells (p < 0.05) and the MCL cells (p = 0.19) to 1 ng/mL of PDGFBB for 12 h enhanced their migration. Incubation with a high concentration (100 ng/mL) of PDGF-BB or bFGF at concentrations tested (1 or 100 ng/mL) for 12 h, produced little or no migratory stimulation on these ligament cells. Our findings support the previous qualitative observations made by numerous investigators. The novel methodology developed in this study may provide a basis for tissue engineering, and the results may be applied to tissue reconstruction techniques of the knee ligaments.

Assessment of functional tests after anterior cruciate ligament surgery.

Functional tests are often used to assess knee function after knee ligament injuries. However, the reliability and validity of these tests have not been sufficiently studied. The main purpose of this study was to examine six functional knee tests in order to establish the tests according to functional demands. The functional tests (vertical jump, figure-of-eight, stairs-running, triple jump, stairs hopple, and side jump tests) were evaluated on 35 patients after anterior cruciate ligament reconstruction (mean = 18 months postoperative). Evaluative variables were the Lysholm functional score, thigh atrophy, and knee instability. Factor analysis was used to identify knee tests based on the same basic variables in order to employ the most representative tests. The factor analysis disclosed two factors that reflected diverse functions. The first factor had significant correlation to the Lysholm score (daily life function) and was best represented by the figure-of-eight and stairs-running tests. The second factor was best correlated to the strength/stability function and was best represented by the triple jump test and the new stairs hopple test. Thus, the tests were categorized according to functional demands--daily life function and strength/stability function. The Lysholm functional score was inaccurate in identifying functional problems during strenuous activities.

A quantitative assessment of orthoses for stabilization of the anterior cruciate ligament deficient knee.

Knee braces are used to restore functional stability to joints which have become unstable as a result of the traumatic disruption of the anterior cruciate ligament. A number of quite different designs of knee brace have evolved and are used clinically in the management of these injuries although to the authors' knowledge little quantitative data are available on their relative mechanical characteristics. This paper reports the results of static testing carried out to determine the stiffness characteristics of 24 commonly used braces. The data obtained indicated clear differences between different brace designs with the stiffest having values closely approaching that achieved physiologically in uninjured joints, and the least effective having minimal stiffnesses. It was found that the mechanical performance of any individual brace was determined by three factors: the mechanical characteristics of the individual components from which it was constructed, the structural integrity of its design, and the interaction of the brace with the limb during loading.