The Synovial fluid is viscous and whose viscosity changes as a function of shear stress and time, which is normally found in joints, tendon sheaths, and fluid-filled sacs in the joints [7, 8]. The synovial fluid contains 3 layers of synoviocytes which is loonnective tissue of fat, collagen and blood vessels and grows as layers that surround fluid filled spaces. During joint disease affected condition the synovium and surrounding muscles, ligaments and tendons weaken . In Rheumatoid arthritis (RA) with and without joint effusion, Spondyloarthropathy (SpA) with and without joint effusion and Osteoarthritis (OA) with and without joint effusion there is a variation in Mean lining thickness, Max lining thickness, Vascularity etc., of the synovial lining.
The Psoriatic arthritis, ankylosing spondylitis and undifferentiated spondyloarthropathy are few other interrelated groups of chronic inflammatory diseases [3, 4]. The internal surface of the synovial membrane is smooth, moist, glistening, and pink. Synovial tissue has shown an arrangement of internal surface cells, subintimal cell, connective tissue fibers, ground substance, nerves, blood vessels and lymphatics . Resistance to joint motion comes from the stretching of surrounding soft tissue and frictional resistance of the joint parts that must slide across each other. Synovial fluid level decrease is associated with joint diseases; Long tern patterns of variation have some prognostic value in human joint diseases patients .
The electrical property of synovial tissue can be obtained by measuring the developed voltage due to applied electrical signal. The synovial fluid level varies from normal patient to arthritis patient as disease prolongs due to weakening of synovium and surrounding muscle tissues. The synovial fluid density increases and WBC count increases across joint affected region. These weakening of muscle tissues can be observed in terms of variation in voltage drop due to applied high frequency electrical signal.
The system used to measure voltage drop is diverged in to two parts as input section and output section. The function of input section is providing high frequency current signal to synovial joint region. The function of output circuit is to pick the response in synovial joint region of the synovial tissue to electrical signal .
2. Material & Methods
The passive electrical property of the synovial tissue to oppose the flow of current flowing through it gives rise to the prediction of presence of the joint diseases. There is a large difference in conductivity of each tissue between the liquid tissues flowing through the blood vessels to the myelin sheaths as insulator in axons of the nerve cells. The electrical property of the tissue can be altered by applying signal with varying frequency.
The electrical bio impedance value of the normal joint region is less and conductivity is more. This weakening of muscle tissues can be observed in terms of variation in voltage drop due to applied high frequency electrical signal. Synovial fluid volume density is equally distributed in normal joint region but under joint disease affected condition synovial fluid volume density is non uniform. The fluid volume density is very high in joint region for joint disease (arthritis) affected patient.
The electrical bio impedance value of high fluid density region is more due to reduction in movement of charges leading to conductivity [2, 4]. The electrical bio impedance value is measured in terms of voltage drop as resistance increases voltage drop increases according to Ohm’s law. The normal and disease affected condition can be identified by measuring the voltage drop across the joint region. For normal patient joint region fluid density is less leading to more conductivity and similarly for arthritis affected patients joint region fluid density is large leading to less conductivity as shown in Fig. 1. If conductivity is more resistance or bio impedance is less leading to less voltage drop. If conductivity is less resistance is high leading to large voltage drop [11, 12].
Fig. 1.Synovial fluid during normal and arthritis affected condition
The input section contains two metal surface electrodes 1 and 2 as shown in Fig. 2, voltage to current converter, Isolation transformer, Signal amplifier, high frequency signal generator and regulated power supply. Output section contains two metal surface electrodes 3 and 4  as shown in Fig. 3, Analog to Digital converter, PIC Microcontroller, LCD interfacing and display.
Fig. 2.Input section block diagram
Fig. 3.Output section block diagram
The patient is isolated from high voltage 50Hz frequency signal by providing two transformers in input section one 230V/6V step down transformer and the other is 6V/6V isolation transformer after amplification stage in the input circuit. In output section patient isolation is achieved by using 6V long lasting battery for all devices in the output circuit.
3. Results and Discussion
The experiment has been conducted based on two categories, Normal male and female patients with different ages and arthritis affected male and female patients. During experimental analysis of first category we observed voltage drop across joint region ranges from 1.32 V to 2.45 V as shown in Table 1. Similarly under analysis of disease affected patient’s voltage drop we observed voltage drops ranges from 2.78 V to 3.75 V as shown in Table 1. These experimental data confirms that young age patients have less voltage drop than old age patients for both normal male and female patients as shown in Figs. 5, 6, Figs. 8 and 9. Also voltage drop was high for advance stage arthritis patient than initial stage arthritis patient rather than age and gender as shown in Figs. 7 and 8. The overall voltage drop variation for normal and diseases affected male and female patients are as shown in Fig. 4.
Table 1.Type of patients and its corresponding grade value for different group patients
Fig. 4.Graph showing grade variation with respect to age
Fig. 5.Graph showing grade variation with respect to age for male patients
Fig. 6.Graph showing grade variation with respect to age for normal male patients
Fig. 7.Graph showing grade variation with respect to age for disease affected male patients
Fig. 8.Graph showing grade variation with respect to age for female patients
Fig. 9.Graph showing grade variation with respect to age for normal female patients
Fig. 10.Graph showing grade variation with respect to age for disease affected female patients
To analyze the performance of the designed non invasive arthritis diagnosis system comparative study has been made with the conventional methods outcome. The 100 patients under the research are all diagnosed by conventional method and tested with non invasive system. The results of both methods were tabulated and analyzed. During these comparative analyze as shown in Table 2 we obtained approximately 93% of positive outcome. Based on the measured grade value for different group of patients the positive accuracy and error percentage value has been calculated by comparing with results obtained with conventional methods as shown in Table 2.
Table 2.Positive accuracy and error percentage value for different patient
The group 1 positive accuracy is around 93.33% and error is around 6.67% because out of 15 patients 14 were diagnosed correctly. Similarly for group 2 to group 6 the positive accuracy and error percentages are tabulated in Table 2. The normal and disease affected male patients positive accuracy is around 92.85% and for female the positive accuracy is around 93.10%. The overall positive accuracy inclusive of male and female is around 93% and error percentage is around 7%.
5. Summary and Conclusion
Based on observations made during current research on 100 normal and disease affected patients we conclude that voltage drop increases uniformly as age increases for normal patient category. For arthritis affected patients synovial fluid density increases based on disease condition rather than age and gender. This result indicates that synovial fluid density increases uniformly as age increases for normal patients and for arthritis patient synovial fluid volume change depends on arthritis disease level. Finally we confirm that designed non invasive system can be used for diagnosis of joint disease like arthritis.