Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ligamentous knee injuries are nowadays more often seen in the office of the family physician, mainly because of an increase in recreational sports injuries. With the help of a questionnaire one can obtain a reliable impression of the injury pattern. The clinical examination is performed in a standardized way, so even in acute ligamentous injuries a correct diagnosis can be obtained at the first examination. The diagnosis of an instability is made with an accurate clinical examination; in case of marginal cooperation of the patient the examination is performed under anesthesia. Depending on the findings, the definitive operation will follow at the same time. In case of a big hemarthrosis we recommend an a.-p. and a lateral X-ray of the knee joint for exclusion of a bony injury before proceeding with the clinical examination. An arthroscopy is indicated in effusions of unclear origin, in the suspicion of meniscal or cartilaginous damage, in a stable knee with hemarthrosis and before definitive stabilization of complex injuries to exclude further damage to other intraarticular structures. Acute ACL ruptures are only operated on in case of bony avulsion fractures, in persons very active in sport and in case of relevant concomitant injuries. Medical collateral injuries without an ACL rupture are usually treated conservatively, except if there is an additional peripheral tear of the meniscus. PCL injuries are seldom operated, except if there is a complex concomitant instability. We aim for an early reconstruction within two weeks after the accident.
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PMID:[Complex internal knee lesions--diagnosis, indications and timing]. 821 48

In this investigation the complex multi-bundle structure of the cruciate ligaments and their interaction with the tibiofemoral joint was modeled analytically by representing the different regions of the cruciates with ligament elements. A sensitivity analysis was then performed to describe the effect that variations of the model input parameters had on the model variables (outputs). The effect that the cruciate ligament bundles had in controlling joint kinematics was dependent on knee flexion angle, and the load applied to the tibiofemoral joint. For passive range of knee motion with the thigh in the horizontal plane (a common rehabilitation activity), all cruciate ligament bundles were strained with the joint positioned between 0 and 10 deg of knee flexion, between 10 and 50 deg only the anterior bundle of the posterior cruciate ligament A-PCL was strained, and from 50 to 90 deg both the anteromedial portion of the anterior cruciate ligament A-ACL and the A-PCL were strained. This finding indicates that a strain distribution about a transverse cross section of the cruciates exists, and demonstrates the importance of differentiating between the strained and unstrained (unloaded) states of these ligaments. The strain value of a cruciate ligament bundle was an indication of how the bundle controls joint kinematics, while the unstrained values describe how much the ligament bundle must deform before it becomes strained and a restraint to tibiofemoral joint motion. In response to anterior and posterior directed loads, applied parallel to the tibial plateau, the respective, ACL and PCL load values were larger in magnitude. The sensitivity of the model outputs to the input parameters was highly dependent on knee flexion angle. The geometrical input parameters of the model (including the ligament insertion site locations and articular surface geometry) had the most pronounced effect on the model output quantities, while the stiffness and initial strain conditions of the ligament bundles had less of an effect on the model outputs. When loaded, the strain values of the ligament bundles were sensitive to the ligament insertion site position. The greatest sensitivity of the model outputs was the femoral insertion of the ACL; supporting clinical impressions and previous experimental findings. Changes in the anterior-posterior dimension of the femoral articular surface did not produce a substantial effect on the model outputs, while changes in the proximal-distal dimension created a large effect; similar results were found for the tibial surface dimensions. These findings indicate that rigid body contact between the articular surfaces may not be a realistic assumption particularly with application to the prediction of tibiofemoral compressive loading and the force/strain values of the cruciate ligament elements. This also has important implications for the design and clinical application of total knee replacements (that function as rigid bodies), particularly those that spare the PCL.
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PMID:A sagittal plane model of the knee and cruciate ligaments with application of a sensitivity analysis. 873 89

The hypothesis of a proprioceptive mechanism arising from mechanoreceptors in the cruciate ligaments and with efferences to the thigh muscles is investigated in an animal model. Electromyographic (EMG) studies of the quadriceps and hamstrings muscles were performed in six sheep anesthetized by intravenous injection of chloralose on applying static and dynamic shear forces to isolated fascicle bundles in the anterior (ACL) and posterior (PCL) cruciate ligaments at 200 to 500 N and 50 to 200 N/sec, respectively. With the help of an external fixator, the knee joint position was varied at 25 to 150 degrees. The relative preload of the anteromedial and posterolateral fascicles in the ACL and the anterior and posterior fascicles in the PCL induced by variation of the joint angle was measured with the help of strain gages. By static and dynamic loading of the anteromedial group of the ACL, EMG activity in the hamstrings increases significantly to 159 +/- 22 and 257 +/- 46 microV seconds, respectively (p < 0.001), with a simultaneous suppression of the quadriceps activity. Static and dynamic loading of the posterolateral ACL group results in a significant excitation of the quadriceps with mean potentials of 142 +/- 29 and 173 +/- 23 microV seconds, respectively (p < 0.001). Mechanical shear applied both to the anterior and posterior fascicles of the PCL induces a significant activation of the ipsilateral quadriceps muscles with a simultaneous inhibition of the hamstrings (p < 0.001). The quality of mechanical loading, i.e., static or dynamic shear, determines the degree of muscular recruitment significantly (p < 0.01). The joint angle contributes to a modulation in the quantitative EMG excitation. Linear regression analysis of the integrated EMG potential values and the amount of passive preload induced by the respective joint position results in a close correlation (r = + 0.78 to + 0.86). The results lead to the conclusion that a proprioceptive mechanism exists that arises from the cruciate ligaments and influences the tone in the thigh muscles. The degree of muscle excitation on mechanical ligament loading is modulated by the amount of preload in the ACL and PCL and the quality of load applied.
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PMID:Proprioceptive mechanisms in the cruciate ligaments: an electromyographic study on reflex activity in the thigh muscles. 881 Sep 68

This article presents the minimum 2-year results (range, 24 to 48 months) of 20 arthroscopically assisted combined anterior cruciate ligament/posterior cruciate ligament (ACL/PCL) reconstructions, evaluated preoperatively and postoperatively using the Tegner, Lysholm, and Hospital for Special Surgery knee ligament rating scales, and the KT 1000 knee ligament arthrometer (Medmetric Corp, San Diego, CA). There were 16 men or boys, 4 women or girls; 9 right, 11 left; 10 acute, and 10 chronic knee injuries. Ligament injuries included 1 ACL/PCL tear, 2 ACL/PCL/medial collateral ligament (MCL)/posterior lateral corner tears. 7 ACL/PCL/MCL tears, and 10 ACL/PCL/posterior lateral corner tears. ACLs were reconstructed using autograft or allograft patellar tendons. PCLs were reconstructed using allograft Achilles tendon, or autograft patellar tendon. MCL tears were successfully treated with bracing. Posterior lateral instability was successfully treated with long head of the biceps femoris tendon tenodesis. Tegner, Lysholm, and Hospital for Special Surgery knee ligament rating scales significantly improved preoperatively to postoperatively (P = .0001). Corrected anterior KT 1000 measurements improved from preoperative to postoperative status (P = .0078).
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PMID:Arthroscopically assisted combined anterior and posterior cruciate ligament reconstruction. 883 23

A model of the knee in the sagittal plane was developed to study the forces in the ligaments induced by isometric contractions of the extensor and flexor muscles. The geometry of the distal femur was obtained from cadaver data. The tibial plateau and patellar facet were modeled as flat surfaces. Eleven elastic elements were used to describe the mechanical behavior of the anterior and posterior cruciate ligaments (ACL and PCL), the medial and lateral collateral ligaments (MCL and LCL), and the posterior capsule. The model knee was actuated by 11 musculotendinous units, each muscle represented by a Hill-type contractile element, a series-elastic element, and a parallel-elastic element. Tendon was assumed to be elastic. The response of the model to anterior-posterior drawer suggests that the geometrical and mechanical properties of the model ligaments approximate the behavior of real ligaments in the intact knee. Calculations for a simulated quadriceps leg raise indicate further that the two-dimensional model reproduces the response of the three-dimensional knee under similar conditions of loading and constraint. During maximum isometric contractions of the quadriceps, the model ACL is loaded from full extension to 80 degrees C of flexion; the model PCL is loaded at 70 degrees of flexion and greater. For maximum isometric extension, ACL forces in the range 0-20 degrees of flexion depend most heavily upon the force-length properties of the quadriceps. At flexion angles greater than 20 degrees, cruciate ligament forces are determined by the geometry of the articulating surfaces of the bones. During isolated contractions of the hamstrings and gastrocnemius muscles, the model ACL is loaded from full extension to 10 degrees of flexion; the model PCL is loaded at all flexion angles greater than 10 degrees. Isolated contractions of the flexor muscles cannot unload the ACL near full extension, as the behavior of the ACL in this region is governed by the shapes of the bones. At 10 degrees of flexion or greater, the overall pattern of PCL force is explained by the force length properties of the hamstrings and by the geometrical arrangement of the flexor muscles about the knee.
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PMID:A musculoskeletal model of the knee for evaluating ligament forces during isometric contractions. 900 37

Growth factors have the potential to enhance native repair responses in ligamentous and meniscal lesions. However, methods for applying these cytokines to sites of injury for extended periods are lacking. We suggest that local transfer of genes that encode the relevant healing factors merits investigation as a potential solution to this problem. In the present study, different viral vectors and liposomes are evaluated for their ability to deliver genes to cells of ligamentous and meniscal origin. The ACL, PCL, MCL, semitendinosus tendon, patellar tendon, and menisci were harvested from New Zealand white rabbits. Cells grown from these tissues were then investigated for their susceptibility to genetic alteration by these vectors. Based upon the ability of these vectors to convert cells in culture to a lacZ(+) phenotype, adenovirus was the most effective vector in short-term experiments. However, expression was transient. Although retrovirus gave lower initial transduction efficiencies, the percentage of transduced cells could be increased by the use of the selectable marker gene neo(r). Cells infected with adeno-associated virus containing the neor-gene could also be selected in this way. Liposomes showed low efficiency of gene transfer and expression. In an in vivo marker study, we injected adenovirus into the rabbit patellar tendon. Transduced cells could be observed preferentially in the subsynovial layer at a declining frequency over a 6-week period. The allogeneous transplantation of retrovirally transduced fibroblasts into the patellar tendon resulted in a greater number of transduced cells. Although the number of lacZ(+) cells declined with time, positive cells were still present 6 weeks after transplantation. Furthermore, the transplanted cells, unlike cells transduced in situ with adenovirus, migrated from the injection site and integrated into the crimp of the tendon.
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PMID:[Virally mediated gene transfer in the patellar tendon. An experimental study in rabbits]. 929 43

A sagittal-plane model of the knee is used to predict and explain the relationships between the forces developed by the muscles, the external loads applied to the leg, and the forces induced in the cruciate ligaments during isometric exercises. The geometry of the model bones is adapted from cadaver data. Eleven elastic elements describe the geometric and mechanical properties of the cruciate ligaments, the collateral ligaments, and the posterior capsule. The model is actuated by 11 musculotendinous units, each unit represented as a three-element muscle in series with tendon. For isolated contractions of the quadriceps, ACL force increases as quadriceps force increases for all flexion angles between 0 and 80 degrees; the ACL is unloaded at flexion angles greater than 80 degrees. When quadriceps force is held constant, ACL force decreases monotonically as knee-flexion angle increases. The relationship between ACL force, quadriceps force, and knee-flexion angle is explained by the geometry of the knee-extensor mechanism and by the changing orientation of the ACL in the sagittal plane. For isolated contractions of the hamstrings, PCL force increases as hamstrings force increases for all flexion angles greater than 10 degrees; the PCL is unloaded at flexion angles less than 10 degrees. When hamstrings force is held constant, PCL force increases monotonically with increasing knee flexion. The relationship between PCL force, hamstrings force, and knee-flexion angle is explained by the geometry of the hamstrings and by the changing orientation of the PCL in the sagittal plane. At nearly all knee-flexion angles, hamstrings co-contraction is an effective means of reducing ACL force. Hamstrings co-contraction cannot protect the ACL near full extension of the knee because these muscles meet the tibia at small angles near full extension, and so cannot apply a sufficiently large posterior shear force to the leg. Moving the restraining force closer to the knee-flexion axis decreases ACL force; varying the orientation of the restraining force has only a small effect on cruciate-ligament loading.
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PMID:Dependence of cruciate-ligament loading on muscle forces and external load. 939 68

Simultaneous ACL and PCL ruptures are rare but serious injuries resulting in distinct instability of the knee joint followed by an early degenerative arthritis. This combined trauma, which is often accompanied by additional ligament lesions, originates from a knee dislocation. While the conservative treatment of this complex instability is abandoned, the operative procedures are not yet standardised. The timing of the cruciate ligament reconstruction depends on the additional injuries, but generally the postprimary treatment is performed. Autografts and allografts, which can be also combined, are available for the reconstruction of the cruciate ligaments. The arthroscopic assisted operation starts with the drilling of all tibial and femoral tunnels using standard ACL and PCL arthroscopic instruments. The PCL is positioned after the graft has been transported into the joint through an anterolateral port, the ACL graft is positioned through the tibial drill hole and both are anchored first on the femoral and then on the tibial site i.e. with interference screws. In the postoperative rehabilitation neither immobilisation nor brace are used and progressive range of motion is allowed. The arthroscopic assisted reconstructions of the ACL and increasingly of the PCL are becoming standard procedures, but the technically difficult combined ACL/PCL reconstruction is restricted to a small number of arthroscopists. The first clinical results demonstrate, that the arthroscopic operation is comparable to the open reconstruction.
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PMID:[Combined anterior cruciate ligament and posterior cruciate ligament injury--technique and results of simultaneous arthroscopic reconstruction]. 981 62

The aim of this study was to test the hypothesis that the coupled features of passive knee flexion are guided by articular contact and by the isometric fascicles of the ACL, PCL and MCL. A three-dimensional mathematical model of the knee was developed, in which the articular surfaces in the lateral and medial compartments and the isometric fascicles in the ACL, PCL and MCL were represented as five constraints in a one degree-of-freedom parallel spatial mechanism. Mechanism analysis techniques were used to predict the path of motion of the tibia relative to the femur. Using a set of anatomical parameters obtained from a cadaver specimen, the model predicts coupled internal rotation and ab/adduction with flexion. These predictions correspond well to measurements of the cadaver specimen's motion. The model also predicts posterior translation of contact on the tibia with flexion. Although this is a well-known feature of passive knee flexion, the model predicts more translation than has been reported from experiments in the literature. Modelling of uncertainty in the anatomical parameters demonstrated that the discrepancy between theoretical predictions and experimental measurement can be attributed to parameter sensitivity of the model. This study shows that the ligaments and articular surfaces work together to guide passive knee motion. A principal implication of the work is that both articular surface geometry and ligament geometry must be preserved or replicated by surgical reconstruction and replacement procedures to ensure normal knee kinematics and by extension, mechanics.
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PMID:Ligaments and articular contact guide passive knee flexion. 988 45

Ten anterior and posterior cruciate ligaments (ACL and PCL) harvested from adult sheep were investigated under light microscopy for data on the frequency and localisation of neural structures. Serial sections of 25 microns thickness were stained with a modified gold chloride technique. Receptors were classified according to their histological structure. Topographic distribution and frequency within the ligament texture were determined with the help of computerized image analysis. Three distinct neural structures could be identified: Ruffini endings, Ruffini corpuscles of the Golgi tendon organ-like type and Pacinian corpuscles. Golgi tendon organs were not found. In total, 274 and 238 neural structures were present in the 10 ACL and 10 PCL, respectively. Pacinian receptors were the most common structures, with a mean frequency of 13.6 +/- 5.3 (ACL) and 12.4 +/- 5.1 (PCL), followed by Ruffini endings with 8.9 +/- 3.2 (ACL) and 7.8 +/- 2.9 (PCL), whereas Ruffini corpuscles had the lowest frequency with a mean value of 4.9 +/- 2.1 (ACL) and 3.4 +/- 1.1 (PCL). The majority of the neural structures were located in the subsynovial sheath or closely associated with endotenon structures. The tibial and femoral insertion areas had a significantly increased receptor density compared with the midpart of the ACL and PCL (P < 0.001), where only 19.3% and 23.7% of the receptors were located. These results emphasise the complex sensory structure of the cruciate ligaments and provide a valid morphological basis for further neurophysiological investigations.
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PMID:Proprioception of the cruciate ligaments: receptor mapping in an animal model. 993 92


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