Quantitative study of the quadriceps muscles and trochlear groove geometry related to instability of the patellofemoral joint

This was a quantitative study of the major anatomical structures associated with instability of the patellofemoral joint: the quadriceps muscles and the femoral trochlear groove. The attachments of the muscles to the patella, their lines of action, and their relative sizes (physiological cross-sectional areas) were found. On the basis of the physiological cross-sectional areas, it was estimated that the central muscles-the rectus femoris and vastus intermedius-contributed 35% of the quadriceps strength, with 40% from the vastus lateralis and 25% from the vastus medialis. The vastus lateralis had the most variable results, with the ratio of the lateralis to the medialis ranging from 0.90 to 2.18; this may be associated with patellar instability. Both the long and oblique parts of the vastus medialis were more oblique than the corresponding parts of the vastus lateralis. Photographic "skyline" views of the trochlear groove produced data on the sulcus angle and ratio of depth to width. The data showed that the trochlear groove did not deepen in the area contacted by the patella with progressive knee flexion (p > 0.53), contrary to popular belief. These data are useful for objective analysis of patellofemoral stability and related surgical interventions.

Quantitative measurement of patellofemoral joint stability: force-displacement behavior of the human patella in vitro

Patellofemoral joint instability is a common clinical problem. However, little quantitative data are available describing the stability characteristics of this joint. We measured the stability of the patella against both lateral and medial displacements across a range of knee flexion angles while the quadriceps were loaded physiologically. For eight fresh-frozen knee specimens a materials testing machine was used to displace the patella 10 mm laterally and 10 mm medially while measuring the required force, with 175 N quadriceps tension. The patella was connected via a ball-bearing patellar mounting 10 mm deep to the anterior surface to allow natural tilt and other rotations. Patellar force-displacement behavior was tested at flexion angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. Significant differences were found between the lateral and medial restraining forces at 10 mm displacement. For lateral displacement, the restraining force was least at 20 degrees of knee flexion (74 N at 10 mm displacement), rising to 125 N at 0 degrees and 90 degrees of knee flexion. The restraining force increased progressively with knee flexion for medial patellar displacement, from 147 N at 0 degrees to 238 N at 90 degrees. With quadriceps tension, the patella was more resistant to medial than lateral displacement. Our finding that lateral patellar displacement occurred at the lowest restraining force when the knee was flexed 20 degrees agrees with clinical experience of patellar instability.

Lateral force-displacement behaviour of the human patella and its variation with knee flexion--a biomechanical study in vitro

This study measured the patellar lateral force-displacement behaviour at a range of knee flexion angles in normal human cadaver specimens. The knee extensor muscles were loaded in proportion to their physiological cross-sectional areas, the tensions being applied in physiological directions along the separate quadriceps muscles. Knee extension was blocked at a range of knee flexion angles from 0 to 90 degrees, and patellar lateral displacement versus force characteristics were measured. This experiment was repeated with three total muscle forces, 20, 175 and 350 N, which were held constant at all flexion angles. It was shown that similar stability variation was obtained with the different total muscle loads, and also the forces required to produce a range of patellar displacements (1.5, 9 mm) were examined. A 5 mm lateral patellar displacement required a constant displacing force (i.e. the patella had constant lateral stability) up to 60 degrees knee flexion, and then a significant increase at 90 degrees. The results were related to surgical and anatomical observations.

Permeability and swelling studies on free films containing inulin in combination with different polymethacrylates aimed for colonic drug delivery

The aim of this study was to assess some permeability and swelling characteristics of free films prepared by combination of inulin as a bacterially degradable system and time- or pH-dependent polymers as a coating formulation for colonic drug delivery. Different free films were prepared by casting and solvent evaporation method. Formulations containing inulin with Eudragit RS, Eudragit RL, Eudragit RS-Eudragit RL, Eudragit FS and Eudragit RS-Eudragit S with different ratios of inulin were prepared. After preparation, free films were evaluated by water vapor transmission test, swelling experiment and permeability to indomethacin and theophylline in different media. Formulations containing Eudragit FS had high resistance to water vapor permeation; but were unable to protect premature swelling and drug release in simulated small intestine media. Also, combination of Eudragit RS and Eudragit S had no suitable characteristics for colon delivery. However, Eudragit RS and Eudragit RL in combination with inulin made free films which had more swelling and permeation of drug in the colonic medium rather than the other media. It was shown that formulations containing sustained release polymethacrylates in combination with inulin have more potential as a coating system for specific colon delivery compared with pH-dependent polymers.

The contribution of the medial retinaculum and quadriceps muscles to patellar lateral stability--an in-vitro study

Patellofemoral joint stability is a result of the restraining effects of the quadriceps muscles, the retinacular structures, and engagement of the bones. The role and significance of these mechanisms in restraining patellar lateral displacement was investigated in this study by measuring the force needed to cause 5 mm lateral displacement (i.e. the mechanical stability, or 'stabilising force') of the patella. Six cadaver knees had 175 N quadriceps load distributed among three muscle groups. With a force ratio matching the muscles physiological cross sectional areas, no significant change occurred in the patellar stabilising force between 0 and 60 degrees knee flexion, but a significant increase occurred between 60 and 90 degrees, presumably reflecting the contribution of the femoral groove. Variation of the quadriceps force distribution changed the stability significantly. Relaxing the vastus lateralis increased the patellar lateral stabilising force 52+/-8%, while relaxing vastus medialis reduced the stabilising force 47+/-9%. The minimum stabilising force was at 30 degrees knee flexion. Transection of the medial retinaculum reduced the lateral stabilising force 34% in the extended knee. This effect disappeared by 45 degrees knee flexion. It was concluded that the quadriceps muscles had a significant and consistent effect across the whole range of knee flexion, but the contribution of the medial retinaculum was restricted to extended knee postures.

Mobilization of antioxidant vitamin pools and hemodynamic function after myocardial infarction

BACKGROUND

Although most previous studies have attempted to correlate plasma concentrations of vitamins with specific cardiovascular end points, metabolic considerations suggest that changes in myocardial tissue and storage organs may be better indicators of myocardial oxidative stress.

METHODS AND RESULTS

Rats fed commercial chow or a diet enriched with vitamin E for 2 weeks were subjected to either a surgical myocardial infarction (MI) or a sham procedure. Rats were hemodynamically assessed 16 weeks after surgery, and their heart, liver, kidney, and plasma were analyzed for antioxidant vitamins E (tocopherol) and A (retinol and total retinyl esters). At 16 weeks, MI rats on a control diet showed depressed peak systolic and elevated diastolic pressures in both right and left ventricles compared with their sham controls. Plasma concentrations of vitamins E and A in MI rats were not different from sham controls fed the same diet. However, concentrations of vitamin E in left ventricle and liver and of vitamin A in liver (retinol) and kidney (retinyl esters) were decreased in rats with MI compared with the sham controls. Vitamin E supplementation improved hemodynamic function in rats with MI and increased plasma, myocardial, liver, and kidney concentrations of vitamin E. The vitamin E diet also prevented the loss of total retinyl esters from the kidney but not of retinol from the liver in MI rats.

CONCLUSIONS

Dietary supplements of vitamin E can sustain better cardiac function subsequent to MI. Antioxidant vitamin levels in the myocardium or in storage organs and not in plasma may be better indicators of myocardial oxidative stress.

Oxidative stress in congestive heart failure

Heart failure is considered to be a complex clinical syndrome, with alterations in the multiple neurohumoral systems and subcellular cardiac sites that correlate with abnormal cardiac function. Strong evidence for the role of oxidative stress in the pathogenesis of heart failure has been provided by studies on experimental animals as well as humans. This concept is gaining more acceptance due to the fact that during heart failure, changes in different neurohormones, cytokines, nitric oxide, and activated inflammatory cells are closely linked to oxidative stress at the cellular and molecular levels. The present article provides a simple description of oxygen free radicals as well as the antioxidant defense system. Evidence for the role of oxidative stress in the pathogenesis of heart failure is reviewed in a concise manner.

Real-time simulation of the nonlinear visco-elastic deformations of soft tissues

PURPOSE

Mass-spring-damper (MSD) models are often used for real-time surgery simulation due to their fast response and fairly realistic deformation replication. An improved real time simulation model of soft tissue deformation due to a laparoscopic surgical indenter was developed and tested.

METHOD

The mechanical realization of conventional MSD models was improved using nonlinear springs and nodal dampers, while their high computational efficiency was maintained using an adapted implicit integration algorithm. New practical algorithms for model parameter tuning, collision detection, and simulation were incorporated.

RESULTS

The model was able to replicate complex biological soft tissue mechanical properties under large deformations, i.e., the nonlinear and viscoelastic behaviors. The simulated response of the model after tuning of its parameters to the experimental data of a deer liver sample, closely tracked the reference data with high correlation and maximum relative differences of less than 5 and 10%, for the tuning and testing data sets respectively. Finally, implementation of the proposed model and algorithms in a graphical environment resulted in a real-time simulation with update rates of 150 Hz for interactive deformation and haptic manipulation, and 30 Hz for visual rendering.

CONCLUSION

The proposed real time simulation model of soft tissue deformation due to a laparoscopic surgical indenter was efficient, realistic, and accurate in ex vivo testing. This model is a suitable candidate for testing in vivo during laparoscopic surgery.

Oxidative stress and functional deficit in diabetic cardiomyopathy

When the equilibrium between free-radical production and cellular antioxidant defences is disturbed in favour of more free radicals, it causes oxidative stress which can promote cellular injury. Oxidative stress has been suggested to play a role in the pathogenesis of diabetic cardiomyopathy. In streptozotocin-induced diabetes, there is a decrease in antioxidant enzyme activities and an increase in myocardial lipid peroxidation. Probucol, an antioxidant, was found to improve cardiac function which may have been due to an increase in myocardial antioxidant enzyme activities and a decrease in lipid peroxidation in the diabetic animals. Some of the beneficial effects of probucol may also be due to an improvement in plasma insulin levels and a decrease in the plasma glucose. The diabetic state is also associated with endothelial dysfunction, retinopathy, neuropathy and renopathy. Some of these secondary complications may also be mediated by oxidative stress. It is suggested that diabetic cardiomyopathy is associated with an antioxidant deficit and that antioxidant therapy may be useful in improving cardiac function in diabetes.

A systematic review of the effect of foot orthoses and shoe characteristics on balance in healthy older subjects

BACKGROUND

Foot orthoses are used to optimize lower extremity function and can improve postural stability by enhancing the afferent somatosensory feedback available to the central nervous system.

OBJECTIVE

The aim of this review was to evaluate the effect of foot orthoses on balance control in older subjects.

STUDY DESIGN

Systematic review.

METHODS

The search strategy was based on the Population Intervention Comparison Outcome method. A search was performed in PubMed, Science Direct, Google Scholar, and ISI Web of Knowledge databases by using selected keywords. A total of 22 articles were selected for final evaluation.

RESULTS

The results demonstrated that older people should be advised to wear thin, hard-soled footwear with high collars to reduce the risk of falling. The findings for insoles demonstrated an increase in balance control via vibratory or magnetic insoles, but textured insoles do not appear to be beneficial for balance improvement.

CONCLUSION

Foot orthoses improve postural stability via a somatosensory or biomechanical effect. Use of footwear with the proper features can be an appropriate intervention in order to increase the balance in the older population and reduce falls.

CLINICAL RELEVANCE

Loss of balance is an important factor in increasing the risk of falling in older subjects. Foot orthoses can improve functional measures of stability in older adults. In this review, results from studies suggest a number of recommendations regarding the optimal footwear for older people to reduce the risk of falling.

Heart Sounds Separation From Lung Sounds Using Independent Component Analysis

Heart beat is an unavoidable source of interference during lung sound recording. This disturbance is more significant at low and medium breathing flow rates. Removing heart sounds (HS) from lung sound recordings or vice versa is a challenging task but of great interest for respiratory specialists and cardiologists. In this study, to separate the two signals, a novel HS separation method based on Independent Component Analysis (ICA) is developed. This method applies an ICA algorithm to the spectrograms of two simultaneous lung sound recordings obtained at two different locations on the chest and yields the independent spectrograms of the separated signals. Then, by implementing the Inverse Short Time Fourier Transform (ISTFT), the separated signals are reconstructed in the time domain. The method was applied to data of two healthy subjects. Analysis of the results as well as subjective inspections indicate the efficiency of the proposed method in terms of HS separation from lung sounds.

Trunk muscles strength and endurance in chronic low back pain patients with and without clinical instability

OBJECTIVES

Previous research has shown inconsistent findings regarding muscle endurance in chronic low back pain (CLBP). Questions also remain about muscle endurance in patients with clinical instability. The aim of this study was to investigate trunk muscles strength and endurance in CLBP patients with and without clinical instability.

METHODS

32 CLBP patients (15 with and 17 without clinical instability) and 39 matched healthy subjects participated in this study. The standing extension test was performed to assess the strength and endurance of the lumbar extensors while recording their electromyographic activity. The patients' disability was evaluated using the Oswestry and Roland-Morris Disability Questionnaires.

RESULTS

Patients with clinical instability showed lower maximal voluntary exertion (MVE) and higher time to fatigue (TTF) compared to healthy subjects (P=0.000 and P=0.008, respectively) and patients without instability (P=0.002 and P=0.02, respectively). There was no difference in these variables between patients without instability and healthy controls. A negative relationship between MVE and TTF and a positive correlation between disability and pain intensity were seen.

CONCLUSION

Strength training of trunk extensor muscles can be considered as part of the treatment protocol for CLBP patients with clinical instability. Although patients without instability suffered from pain or disability, they showed more similarity to healthy subjects in terms of trunk muscles strength and endurance.

Micromechanics of brain white matter tissue: A fiber-reinforced hyperelastic model using embedded element technique

A transverse-plane hyperelastic micromechanical model of brain white matter tissue was developed using the embedded element technique (EET). The model consisted of a histology-informed probabilistic distribution of axonal fibers embedded within an extracellular matrix, both described using the generalized Ogden hyperelastic material model. A correcting method, based on the strain energy density function, was formulated to resolve the stiffness redundancy problem of the EET in large deformation regime. The model was then used to predict the homogenized tissue behavior and the associated localized responses of the axonal fibers under quasi-static, transverse, large deformations. Results indicated that with a sufficiently large representative volume element (RVE) and fine mesh, the statistically randomized microstructure implemented in the RVE exhibits directional independency in transverse plane, and the model predictions for the overall and local tissue responses, characterized by the normalized strain energy density and Cauchy and von Mises stresses, are independent from the modeling parameters. Comparison of the responses of the probabilistic model with that of a simple uniform RVE revealed that only the first one is capable of representing the localized behavior of the tissue constituents. The validity test of the model predictions for the corona radiata against experimental data from the literature indicated a very close agreement. In comparison with the conventional direct meshing method, the model provided almost the same results after correcting the stiffness redundancy, however, with much less computational cost and facilitated geometrical modeling, meshing, and boundary conditions imposing. It was concluded that the EET can be used effectively for detailed probabilistic micromechanical modeling of the white matter in order to provide more accurate predictions for the axonal responses, which are of great importance when simulating the brain trauma or tumor growth.

Effect of vibration on postural control and gait of elderly subjects: a systematic review

BACKGROUND AND AIM

Gait and balance disorders are common in the elderly populations, and their prevalence increases with age. This systematic review was performed to summarize the current evidence for subthreshold vibration interventions on postural control and gait in elderly.

METHOD

A review of intervention studies including the following words in the title/abstract: insole, foot and ankle appliances, vibration, noise and elderly related to balance and gait. Databases searched included PubMed, ISI Web of Knowledge, Ovid, Scopus, and Google Scholar. Fifteen articles were selected for final evaluation. The procedure was followed using the preferred reporting items for systematic reviews and meta-analysis method.

RESULTS

There was reduction in center of pressure velocity and displacement especially with eyes closed using vibration in healthy elderly subjects and this effect was greater in elderly faller and patients with more balance deficiency. Vibration programme training increased speed of walking, cadence, step time and length in stroke subjects. The vibratory insoles significantly improved performance on the Timed Up and Go and Functional Reach tests in older people.

CONCLUSION

Vibration was effective on balance improvement in elderly subject especially elderly with more balance deficiency and it can improve gait parameters in patients with greater baseline variability.

The effects of trochlear groove geometry on patellofemoral joint stability-a computer model study

The effect of the variation in the femoral groove geometry on patellofemoral joint stability was studied using a two-dimensional transverse plane model with deformable articular surfaces. The femoral and patellar bony structures were modelled as rigid bodies with their profiles expressed by splines. The articular cartilage was discretized into compression springs, distributed along the femoral and patellar profiles, based on the rigid-body spring model. The medial and lateral retinacula were modelled as linear tensile springs, and the quadriceps muscles and patellar tendon as strings with known tension. The anatomical data were obtained from the transverse plane magnetic resonance images of a normal knee flexed at 20° and from the literature. A dynamic analysis approach was employed to solve the governing equations of the model, i.e. three static equilibrium equations of the patella and a constraint equation for each cartilage spring, explicitly. The results of the model suggest that alteration of the sulcus angle from 139° to 169° causes a lateral shift and tilt of less than 3 mm and 4°. This effect increased slightly with increasing total quadriceps force, however, to significantly more than 7 mm and 18° respectively when the medial retinaculum was released. It was suggested that this might be the combined effect of the medial retinaculum deficiency and trochlear dysplasia that is responsible for patellar subluxation and, particularly, dislocation disorders.

Design and development of a hand robotic rehabilitation device for post stroke patients

Robot-mediated rehabilitation is a rapidly advancing discipline that seeks to develop improved treatment procedures using new technologies, e.g., robotics, coupled with modern theories in neuroscience and rehabilitation. A robotic device was designed and developed for rehabilitation of upper limbs of post stroke patients. A novel force feedback bimanual working mode provided real-time dynamic sensation of the paretic hand. Results of the preliminary clinical tests revealed a quantitative evaluation of the patient's level of paresis and disability.

The efficiency of mechanical orthoses in affecting parameters associated with daily living in spinal cord injury patients: a literature review

OBJECTIVE

The most simple and common approach in providing standing and walking by subjects with spinal cord injury (SCI) is the use of mechanical orthoses. These include traditional orthoses, medial linkage orthoses (MLOs) and reciprocating gait orthoses (RGOs). Independence, energy expenditure, gait parameters, system reliability and cosmesis are important factors in orthotic design. The aim of this review was to compare the evidence of existing mechanical orthoses to that of other types regarding these factors.

METHODS

The preferred reporting items for systematic reviews and meta-analyses (PRISMA) method was used by an experience researcher based on selected keywords and their composition and an electronic search was performed in well-known databases.

RESULTS

Twenty articles were selected for final evaluation. Many were case studies, and also had limited and heterogeneous sample sizes with different instruments used for evaluation. The results of the analysis demonstrated that independence and cosmesis are improved when using MLOs, but gait parameters, energy expenditure and stability are all improved when using RGOs.

CONCLUSION

Those mechanical orthoses which have reciprocal motion and congruency between the anatomical and orthotic joints have been shown to provide positive effects on patient lifestyles. However, further improvement is needed to more effectively meet the needs of SCI patients.

IMPLICATIONS FOR REHABILITATION

The most simple and traditional approach to enable standing and walking by people with SCI is use of purely mechanical orthoses. The most important factors that increase rejection rates of orthoses in paraplegia patients are excessive energy expenditure and increased applied force on upper limb joints. Improvement of the structure of mechanical orthoses is needed to improve independence, energy expenditure, and gait parameters, and is an important approach to improve ambulatory function in subjects with paraplegia.

State of the art review on design and manufacture of hybrid biomedical materials: Hip and knee prostheses

The trend in biomaterials development has now headed for tailoring the properties and making hybrid materials to achieve the optimal performance metrics in a product. Modern manufacturing processes along with advanced computational techniques enable systematical fabrication of new biomaterials by design strategy. Functionally graded materials as a recent group of hybrid materials have found numerous applications in biomedical area, particularly for making orthopedic prostheses. This article, therefore, seeks to address the following research questions: (RQ1) What is the desired structure of orthopedic hybrid materials? (RQ2) What is the contribution of the literature in the development of hybrid materials in the field of orthopedic research? (RQ3) Which type of manufacturing approaches is prevalently used to build these materials for knee and hip implants? (RQ4) Is there any inadequacy in the methods applied?

Design and evaluation of a novel triaxial isometric trunk muscle strength measurement system

Maximal strength measurements of the trunk have been used to evaluate the maximum functional capacity of muscles and the potential mechanical overload or overuse of the lumbar spine tissues in order to estimate the risk of developing musculoskeletal injuries. A new triaxial isometric trunk strength measurement system was designed and developed in the present study, and its reliability and performance was investigated. The system consisted of three main revolute joints, equipped with torque sensors, which intersect at L5—S1 and adjustment facilities to fit the body anthropometry and to accommodate both symmetric and asymmetric postures in both seated and standing positions. The dynamics of the system was formulated to resolve validly the moment generated by trunk muscles in the three anatomic planes. The optimal gain and offset of the system were obtained using deadweights based on the least-squares linear regression analysis. The R2 results of calibration for all loading courses of all joints were higher than 0.99, which indicated an excellent linear correlation. The results of the validation analysis of the regression model suggested that the mean absolute error and the r.m.s. error were less than 2 per cent of the applied load. The maximum value of the minimum detectable change was found to be 1.63 N m for the sagittal plane torque measurement, 0.8 per cent of the full-scale load. The trial-to-trial variability analysis of the device using deadweights provided intra-class correlation coefficients of higher than 0.99, suggesting excellent reliability. The cross-talk analysis of the device indicated maximum cross-talks of 1.7 per cent and 3.4 per cent when the system was subjected to flexion—extension and lateral bending torques respectively. The trial-to-trial variability of the system during in-vivo strength measurement tests resulted in good to excellent reliability, with intra-class correlation coefficients ranging from 0.69 to 0.91. The results of the maximum voluntary isometric torques exertion measurements for 30 subjects indicated good agreement with the previously published data in the literature. The extensive capabilities and high reliability of the system are promising for more comprehensive investigations on the trunk biomechanics in future, e.g. isometric strength measurement at symmetric and asymmetric postures, muscle endurance, and recruitment pattern analysis.

A triple-jaw actuated and sensorized instrument for grasping large organs during minimally invasive robotic surgery

BACKGROUND

Secure grasping and effective manipulation of delicate large organs during robotic surgery operations needs especially designed instruments that can enclose a large amount of tissue and feed back the pinch forces.

METHODS

A large organ triple-jaw grasper was instrumented using practical force sensory and actuating systems. A force tracking scheme was proposed to facilitate auto-grasping of large organs during robotic teleoperation surgery. An on-site force commanding/reflecting mechanism was also implemented to use the device as an independent hand-held robotic instrument. The efficacy of the robotic grasper was examined in phantom tests.

RESULTS

The instrument grasped large soft objects effectively and safely with accurately measured and controlled pinch forces. Furthermore, it could characterize the overall mechanical behavior of the grasping objects.

CONCLUSIONS

The instrument designed provides a potential solution for the safe and effective grasping and manipulation of large abdominal organs, either as a hand-held device, or in a teleoperation framework.