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At least 523 records · Page 29Linked to original sources

PubMed2003

Electromyographic analysis of a modified maneuver for quadriceps femoris muscle setting with co-contraction of the hamstrings.

A "quadriceps femoris muscle setting" is isometric quadriceps femoris exercise which can be widely used in early knee rehabilitation. However this exercise cannot obtain enough co-contraction of the hamstrings. Isolated quadriceps femoris contraction in knee extension imposes severe strain to anterior cruciate ligament. We succeeded in developing a simple training maneuver that is effective in obtaining co-contraction of the hamstrings--a modified maneuver for the quadriceps femoris muscle setting with the contralateral lower limb raised (MQS). In this study, we analyzed the effect of this maneuver by EMG quantification. Twenty-eight healthy young adult men performed sequential trials consisting of normal quadriceps femoris muscle setting (NQS) and MQS. Electromyographic activity was recorded from surface electrodes on the gluteus maximus, vastus medialis, rectus femoris, vastus lateralis, semitendinosus and biceps femoris (long head), and normalized to values derived from maximal isometric trials. The % maximal voluntary isometric contraction (%MVIC) of the vastus medialis, vastus lateralis and rectus femoris did not vary in the each maneuver. However, the %MVIC of the hamstrings varied significantly in the MQS. This study suggests that effective co-contraction of the hamstrings can be obtained in MQS by adjusting the load to the raised lower limb.

Adult↗

PubMed2005

Kynurenic acid, an endogenous constituent of rheumatoid arthritis synovial fluid, inhibits proliferation of synoviocytes in vitro.

Kynurenic acid is an antagonist of ionotropic glutamate receptors. It has been found that glutamate antagonists inhibit proliferation of different human tumor cells. Since the hyperplasia of synovial fibroblasts is one of the most striking features of inflammatory arthritis, the main goals of this study were detection and quantification of kynurenic acid in synovial fluid obtained from patients with rheumatoid arthritis, and determination of its effect on proliferation of synoviocytes in vitro. Presence of kynurenic acid was determined by HPLC in all 58 samples of synovial fluid. The mean concentration was 15.89 pmol/ml. Kynurenic acid inhibited synoviocyte proliferation with the IC50 value of 5.9 mM. In subthreshold concentration of 0.3 mM it enhanced antiproliferative action of celecoxib and nimesulide. In conclusion, the presence of kynurenic acid in synovial fluid was documented in patients with rheumatoid arthritis. Its potential role as an endogenous substance, controlling synoviocyte proliferation can be suggested.

Animals↗

PubMed2003

Biomechanical evaluation of the motor function of the thumb.

An experimental apparatus was developed to measure force production of a digit at various points of force application along the digit and in any direction within the transverse plane of the longitudinal axis of the digit. Eight normal subjects with asymptomatic hands were tested. Maximum voluntary isometric contraction forces were measured at the interphalangeal joint of the thumb in 16 directions that were evenly distributed within 360 degrees. Peak forces measured in all directions were used to create polar plots and to construct force envelopes using cubic spline interpolation. The areas of the force envelope and force quadrants were then calculated. The force produced by the thumb was dependent on the direction of force application. The highest force, 104.8 +/- 14.2 N, was generated in flexion, while the lowest force was generated in extension. The forces in extension, abduction and adduction were 24.8%, 57.2%, and 46.2% of the flexion force, respectively. Relatively high forces were generated in the directions of flexion combined with abduction, and flexion combined with adduction. The area of the entire force envelope was found to be 12,142 +/- 3,149 N-N. The percentage quadrant areas, relative to the total force envelope area, for extension-adduction, extension-abduction, flexion-abduction, and flexion-adduction were 7.8%, 11.4%, 39.3%, and 41.4%, respectively. The percentage quadrant areas for extension, abduction, flexion, and adduction were 4.9%, 23.6%, 52.7%, and 18.8%, respectively. The current study provides a more advanced and comprehensive method for quantification and investigation of the motor function of the thumb, which has potential in clinical applications for diagnosis of hand disorders, evaluation of deterioration or improvement of hand motor function, and guidance of therapeutic and surgical intervention.

Adult↗

PubMed1989

Distribution of activity within the cat's peroneus longus muscle when activated in different ways via the central nervous system.

We have studied whether a mechanically homogenous muscle (all units giving joint-torques in the same direction) would display different distributions of activity in response to different types of activation via the central nervous system. In adult cats anaesthetized with pentobarbitone, long-lasting contractions were evoked in m. peroneus longus (PerL), a mixed ankle dorsiflexor muscle. The contractions were elicited by continuous repetitive stimulation of: (1) the superficial peroneal nerve (NP, flexion reflex); and (2) the contralateral motor cortex (MC). During these contractions, isometric force was monitored and fine-wire electromyographic recordings (EMG) were simultaneously obtained from anterior and posterior portions of the PerL. The relative degree of activation in anterior vs posterior muscle portions was quantified by measuring, at various force levels: (1) the average spike amplitude (Spike); and (2) the total number of spikes per unit time (Count; 0.5-s measurement periods). For both types of stimulation (MC and NP), the results indicated that activation was more effective for posterior than for anterior muscle portions: the Spike-measurements were typically higher in posterior than in anterior PerL and, for MC-elicited contractions, this was true for the Count-measurements as well. With respect to both types of EMG-quantification (Spike and Count), the 'posterior bias' of activity was significantly more pronounced for the cortically evoked contractions than for those elicited via stimulation of the peroneal nerve. As it is known that anterior and posterior PerL portions tend to be innervated by rostral and caudal motoneurones, respectively, these findings indicate that different inputs to the PerL motoneurone pool may differ significantly with respect to the intraspinal spatial distribution of synaptic effects among the motoneurones. The results were discussed in relation to the organization of task-related recruitment schemes.

Animals↗

PubMedDate not supplied

Quantification of the perfusion of the anterior cruciate ligament and the effects of stress and injury to supporting structures.

The perfusion of the normal ACL was quantitated using the hydrogen washout technique in a canine model. This was compared to the perfusion of the synovium in the suprapatellar pouch. Changes in the ACL perfusion were quantitated after the application of anterior stress, division of the infrapatellar fat pad, and dissection of the synovium enveloping the ACL. The ACL is relatively hypovascular, with one-half the blood flow of the synovium of the suprapatellar pouch. Application of an anterior stress diminishes the blood flow to the ACL to one-fifth of the baseline value, an effect which is reversible. Division of the infrapatellar fat pad causes a two-fold decrease in perfusion to the ACL, whereas dissection of the enveloping synovium results in a complete cessation of blood flow.

Animals↗

PubMed2003

Classification of calcaneal fractures by spiral computed tomography: implications for surgical treatment.

The purpose of this study was to evaluate spiral computed tomography and multislice CT (SCT/MSCT) with multiplanar reconstructions (MPR) in the classification of calcaneal fractures according to a modified CT classification and to quantify fragment displacement to guide surgical treatment. Forty-eight calcaneal fractures were examined by spiral CT (1- to 2-mm slice thickness, pitch=1.5) with multiplanar reconstructions (MPR). Fractures were grouped according to a modified Munich classification scheme, differentiating six categories of fractures by joint involvement, number of fragments in the posterior facet, and the presence and extent of displacement. A qualitative and quantitative statement was made for the presence of clinical relevant displacement of the posterior articular facet (A: >2 mm), widening of the heel (B: crossing fibular reference line), reduction in calcaneal height (C: >10%), and axis shift of the calcaneocuboid angle (D: >10 degrees ). Treatment recommendations resulting from the CT classification were retrospectively compared with the treatment given by examining the patients' files. There were 10 extra-articular and 38 intra-articular fractures; 8 were in class I (extra-articular, nondisplaced), 2 in class II (extra-articular, displaced), 1 in class III (intra-articular, nondisplaced), 20 in class IV (two fragments), 9 in class V (three fragments), and 8 in class VI (>4 fragments), one of the latter being uncertain; 34 showed displacement of the articular facet, 35 widening of the heel, 35 reduction in calcaneal height, and 20 a shift of the axis. In 94% of the cases the procedure recommended by the Munich system of classification was followed; there was disagreement in 1 case in class I and 1 in class IV. Spiral CT allowed fracture classification and quantification of relevant displacement of fragments by radiologists. The implemented recommendations for treatment were adopted by surgeons in most cases.

Adolescent↗

PubMed1997

Macrophage-colony stimulating factor (M-CSF) is increased in the synovial-like membrane of the periprosthetic tissues in the aseptic loosening of total hip replacement (THR).

The aim of the study was to assess the eventual presence, cellular localization and extent of expression of the osteoclast activating cytokine M-CSF (CSF-1) in the periprosthetic tissues around loose total hip replacement (THR). Synovial-like membrane was obtained from the implant-to-bone interface and pseudocapsule from ten total hip revisions performed for aseptic loosening and compared to ten hip synovial tissue samples obtained from ten patients who had primary THR for osteoarthritis. Avidin-biotinperoxidase complex (ABC) and alkaline phosphatase-anti-alkaline phosphatase (APAAP) methods were used for staining and VIDAS image analysis for quantification. M-CSF was mainly produced by macrophages, which often contained wear particles, but also by some fibroblasts and vascular endothelial cells. The number of cells containing (per one mm2 tissue) clearly increased in the interface (1585 +/- 212; p < 0.01) and pseudocapsular (1456 +/- 248; p < 0.01) tissue compared to synovial tissue (543 +/- 118). The present findings suggest, that inflammatory foreign-body type of response enhances expression of M-CSF in cases of aseptic loosening of THR. M-CSF produced in the synovial-like membrane in the implant-bone interface may contribute to activation of osteoclasts in periprosthetic bone and thus to loosening.

Adult↗

PubMed2006

A laterally positioned concave trochlear groove prevents patellar dislocation.

Patellofemoral instability is a disabling condition that occurs in adolescence. Recurrence after patellar dislocation has been reported in 2-50% of patients. We compared the distal femur in patients with patellofemoral instability with distal femura of a healthy cohort using mathematical quantification of two-dimensional shape variation at the same position in different knees. One hundred eight computed tomography scans from 54 patients with patellofemoral instability were compared with 197 computed tomography scans from 102 subjects with normal knees. We used principal components analysis to quantify variation in shape of the trochlear groove as it allows comparison of knees with patellofemoral instability to healthy knees. We found that subjects who had dislocated their patella had a flattened trochlear groove, whereas normal knees had a more concave groove. The position of the trochlear groove was more medial in patients with patellofemoral instability compared with normal knees. Groove position was more important than shape when predicting which patellae were likely to dislocate.

Adolescent↗

PubMed2000

Effects of shear stress on articular chondrocyte metabolism.

The articular cartilage of diarthrodial joints experiences a variety of stresses, strains and pressures that result from normal activities of daily living. In normal cartilage, the extracellular matrix exists as a highly organized composite of specialized macromolecules that distributes loads at the bony ends. The chondrocyte response to mechanical loading is recognized as an integral component in the maintenance of articular cartilage matrix homeostasis. With inappropriate mechanical loading of the joint, as occurs with traumatic injury, ligament instability, bony malalignment or excessive weight bearing, the cartilage exhibits manifestations characteristic of osteoarthritis. Breakdown of cartilage in osteoarthritis involves degradation of the extracellular matrix macromolecules and decreased expression of chondrocyte proteins necessary for normal joint function. Osteoarthritic cartilage often exhibits increased amounts of type I collagen and synthesis of proteoglycans characteristic of immature cartilage. The shift in cartilage phenotype in response to altered load yields a matrix that fails to support normal joint function. Mathematical modeling and experimental studies in animal models confirm an association between altered loading of diarthrotic joints and arthritic changes. Both types of studies implicate shear forces as a critical component in the destructive profile. The severity of cartilage destruction in response to altered loads appears linked to expression of biological factors influencing matrix integrity and cellular metabolism. Determining how shear stress alters chondrocyte metabolism is fundamental to understanding how to limit matrix destruction and stimulate cartilage repair and regeneration. At present, the precise biochemical and molecular mechanisms by which shear forces alter chondrocyte metabolism from a normal to a degenerative phenotype remain unclear. The results presented here address the hypothesis that articular chondrocyte metabolism is modulated by direct effects of shear forces that act on the cell through mechanotransduction processes. The purpose of this work is to develop critical knowledge regarding the basic mechanisms by which mechanical loading modulates cartilage metabolism in health and disease. This presentation will describe the effects of using fluid induced shear stress as a model system for stimulation of articular chondrocytes in vitro. The fluid induced shear stress was applied using a cone viscometer system to stimulate all the cells uniformly under conditions of minimal turbulence. The experiments were carried using high-density primary monolayer cultures of normal and osteoarthritic human and normal bovine articular chondrocytes. The analysis of the cellular response included quantification of cytokine release, matrix metalloproteinase expression and activation of intracellular signaling pathways. The data presented here show that articular chondrocytes exhibit a dose- and time-dependent response to shear stress that results in the release of soluble mediators and extracellular matrix macromolecules. The data suggest that the chondrocyte response to mechanical stimulation contributes to the maintenance of articular cartilage homeostasis in vivo.

Adult↗

PubMed2004

Quantification of T(2) relaxation changes in articular cartilage with in situ mechanical loading of the knee.

PURPOSE: To devise a method for producing in vivo MRI images of the knee under physiologically significant loading, and to compare and evaluate the changes in cartilage characteristics before and during in situ compression of the knee. MATERIAL AND METHODS: A total of 26 asymptomatic subjects were imaged on a 1.5 Tesla Philips Intera scanner using a commercially available knee coil. Routine anatomical images were followed by T(2) map acquisition. These scans were repeated following in situ compression of the knee using a MR compatible loading jig. RESULTS: Following loading to body weight, several regions of femoral cartilage show early alteration of T(2) relaxation time, most significantly in the medial and lateral peripheral zones. There were no significant changes in the tibial cartilage. CONCLUSIONS: The results establish the feasibility of measuring changes on MRI with in situ axial loading.

Adult↗

PubMed1983

Quantification of intersegmental reactions during rapid swing motion.

A simple mathematical model was developed to quantify the non-muscular reactions between two adjacent segments undergoing rapid free-segment motion. Newtonian equations of motion were used to simulate the trajectories of the two segments using the input parameters of linear acceleration and muscular moment acting only about the proximal end of the proximal link. The intersegmental muscular force and moment were mathematically considered to be zero, and no constraints were placed on the motion of the two segments. The motion of the thigh and shank during the swing phase of running was simulated by the model and compared to the real motion obtained from cinematographic records. The simulation demonstrated that proximal thigh motion has a significant effect on the distal shank motion. Depending on the initial conditions, intersegmental reactions alone can produce large increases in distal segment speed. The role of the knee musculature in preventing these reactions during the swing phase of running was inferred.

Biomechanical Phenomena↗

PubMed2002

The contribution of coating microstructure to degradation and particle release in hydroxyapatite coated prostheses.

Plasma-sprayed coatings of hydroxyapatite powder are widely used on hip replacements. Commercially, they are supplied by a large number of companies and thus offer different coating design philosophies. This study focuses on a retrieved prosthetic stem that exhibited coating loss on the femoral stem occurring concurrently with third-body wear. The purpose of the research was to establish possible links between the coating microstructure and the clinical findings. A coated stem and cup were sectioned and the cross section was prepared to reveal the coating microstructure. Characterization included X-ray diffraction, FTIR spectroscopy, and crystalline particle quantification within the coating. It was found that the coating has a high amorphous content that provides fast resorption. The amount of crystalline particles increased on the distal location of the stem, the threads of the acetabular shell, and was generally higher on the cup. Accelerated degradation illustrated how the coating may be a particle-generating source by preferential dissolution of the amorphous phase, possibly allowing liberation of crystalline areas and other particulates at the substrate-coating interface. Such particles mainly include the less soluble hydroxyapatide formed from unmelted particles in the plasma or recrystallisation in the coating, but may also include entrapped grit lodged in the substrate during the roughening process. This study accents the importance of coating microstructure in understanding coating resorption.

Coated Materials, Biocompatible↗

PubMed2003

Reliability of stabilised commercial dynamometers for measuring hip abduction strength: a pilot study.

BACKGROUND: Reliable quantification of hip abductor strength in a clinical setting is challenging. OBJECTIVES: To examine the intrarater and interrater reliability of three commonly used commercial dynamometers in the measurement of hip abduction. METHODS: Supine gravity minimised measures of unilateral hip abduction strength were recorded in 10 women (mean (SD) age 23.5 (1.9) years) using three different commercially available dynameters. Measurements were repeated over a three day period with a different device used on each day. RESULTS: Intrarater reliability ranged from 0.880 to 0.958 across the three devices, and measures of interrater reliability ranged from 0.899 to 0.948. CONCLUSION: Commercially available dynamometers can be used to quantify hip abduction strength with good to excellent reliability. A previously undescribed method of quantifying hip abduction strength in a clinical setting using readily available instrumentation is presented.

Adult↗

PubMed1987

Lachman test evaluated. Quantification of a clinical observation.

The Lachman test has become recognized as the most reliable noninvasive clinical method for determining the integrity of the anterior cruciate ligament. The original description provided for the test is reported as either positive or negative. The purpose of this study is to present a clinical grading system for positive examinations. The criteria are as follows: Grade I, proprioceptive appreciation of a positive test; Grade II, visible anterior translation of the tibia; Grade III, passive subluxation of the tibia with the patient supine; and Grade IV, ability of the patient with a cruciate-deficient knee to actively sublux the proximal tibia. Seventy-five patients with arthroscopically documented complete anterior cruciate ligament tears were examined clinically and graded using the above criteria. In addition, all patients had arthrometric examinations to measure the amount of anterior subluxation of the tibia in millimeters. A one-way analysis of variance followed by Scheffe multiple comparisons demonstrated the mean measurements of anterior displacement of the tibia in each laxity group to be significantly different.

Adolescent↗

PubMed2002

Cyclosporin A inhibition of aggrecanase-mediated proteoglycan catabolism in articular cartilage.

OBJECTIVE: To determine the effect of cyclosporin A (CSA) on aggrecanase- and matrix metalloproteinase (MMP)-mediated catabolism of proteoglycan (aggrecan) in articular cartilage explants stimulated with interleukin-1 (IL-1) in a culture system that mimics early pathologic processes associated with arthritic disease. METHODS: Proteoglycan (glycosaminoglycan) and lactate quantification, Western immunoblot analyses of aggrecan degradation products, reverse transcription-polymerase chain reaction analyses of aggrecanase-1, aggrecanase-2 (ADAM-TS4, ADAM-TS5, respectively), MMP-1, MMP-3, MMP-13, tissue inhibitor of metalloproteinases 1 (TIMP-1), TIMP-2, and TIMP-3 messenger RNA (mRNA) expression in articular cartilage explant cultures, and electrophoretic mobility shift assay analysis of nuclear factor of activated T cells (NF-AT) transcription factor activation were used. RESULTS: CSA inhibited, in a dose-dependent and noncytotoxic manner, aggrecanase-mediated proteoglycan catabolism and loss from IL-1-stimulated cartilage explants. There was no evidence of MMP-mediated aggrecan catabolism in this in vitro model. Treatment of articular cartilage explant cultures with 10 ng/ml of IL-1alpha up-regulated the expression of mRNA for ADAM-TS4, ADAM-TS5, MMP-1, MMP-3, and MMP-13. The expression of ADAM-TS4, ADAM-TS5, and MMP-13 was abrogated by the inclusion of 10 microM CSA in the culture medium. NF-AT activation was observed in chondrocytes but could not be inhibited by preincubation with 10 microM CSA. CONCLUSION: CSA can inhibit IL-1-induced aggrecanase-mediated proteoglycan catabolism in articular cartilage explants maintained in culture for 4 days, thus demonstrating molecular mechanisms whereby CSA may be an effective therapy for degenerative joint disease.

Aggrecans↗

PubMed1990

Quantitative assessment of full range-of-motion isometric lumbar extension strength.

The purpose of this study was to evaluate the reliability and variability of repeated measurements of isometric (IM) lumbar extension (LB EXT) strength made at different joint angles. Fifty-six men (age, 29.4 +/- 10.7 years) and 80 women (age, 24.3 +/- 9.1 years) completed IM LB EXT strength tests on 3 separate days (D1, D2, and D3). On D1 and D2, subjects completed two tests (T1 and T2) separated by a 20- to 30-minute rest interval. For each test, IM LB EXT strength was measured at 72, 60, 48, 36, 24, 12, and 0 degrees of lumbar extension. Mean IM strength values, within-day reliability coefficients, and test variability over the seven angles improved from D1 to D2 (D1: mean, 160.0 to 304.1 N.m, r = 0.78 to 0.96, SEE = 37.6 to 46.9 N.m; D2: mean, 176.3 to 329.1 N.m, r = 0.94 to 0.98, SEE = 29.0 to 34.4 N.m). Mean strength values leveled off by D3 (174.5 to 317.0 N.m). The most reliable test results showed that the IM LB EXT strength curves were linear and descending from flexion to extension and ranged from 235.8 +/- 85.2 to 464.9 +/- 150.7 N.m for men (extension to flexion) and from 134.6 +/- 53.2 to 237.3 +/- 71.9 N.m for women. Lumbar extension strength was clearly greatest in full flexion, which is in contrast to previously reported results. One practice test was required to attain the most accurate and reliable results. These data indicate that repeated measures of IM LB EXT strength are highly reliable and can be used for the quantification of IM LB EXT strength through a range of motion.

Adult↗

PubMed1994

Isokinetic evaluation of muscular performance: implications for muscle testing and rehabilitation.

Interfacing of microprocessors with isokinetic dynamometers has enabled the rapid quantification of many parameters of muscle function including peak torque, angle-specific torque, work, power, torque acceleration energy, and various endurance indexes, and the measurements with these devices can be made isometrically at various angular positions and isokinetically (concentrically or eccentrically) with a large scale of angular speeds. Many of these parameters, however, lack evidence of validity, reproducibility, and/or clinical relevance. Peak torque has been and still is the most properly studied isokinetic strength testing parameter and its use can be recommended for research and clinical purposes. Concerning testing of muscular endurance, the absolute endurance parameters (for example, work performed during the last five repetitions and total work in a 25-repetition test with a speed of 240 degrees/s) are the best for use. Many internal and external factors in the isokinetic testing procedure can have an undesirable effect on the test result. However, through proper education and strict adherence to the test instructions, it is possible to successfully control the confounding variables. In scientific work, isokinetic devices have greatly expanded the possibilities for studying dynamic muscle function. There is also little doubt about their usefulness in documenting the progress of muscular rehabilitation. A disadvantage of isokinetic devices is that isokinetic movement seldom occurs in actual human performance tasks and that the isokinetic training effect is, therefore, quite (although not completely) specific to that type of movement. In addition, being normally an isolated joint exercise, isokinetic training can produce large loads on the involved joints and may, therefore, under certain conditions be dangerous for healing tissues.

Biomechanical Phenomena↗

PubMed1999

Guidance-based quantification of arm impairment following brain injury: a pilot study.

This paper reports the design and preliminary testing of a device for evaluating arm impairment after brain injury. The assisted rehabilitation and measurement (ARM) Guide is capable of mechanically guiding reaching and retrieval movements across the workspace and of measuring constraint forces and range of motion during guidance. We tested the device on four hemiplegic brain-injured individuals and four unimpaired control subjects. During guided movement, the brain-injured subjects generated distinct spatial patterns of constraint force with their impaired arms that were consistent with the standard flexion and extension "synergies" described in the clinical literature. In addition, the impaired arms exhibited well-defined workspace deficits as measured by the ARM Guide. These results suggest that constraint force and range of motion measurements during mechanically guided movement may prove useful for precise monitoring of arm impairment and of the effects of treatment techniques targeted at abnormal synergies and workspace deficits.

Adult↗