Keywords
knee joint - diagnosis - electrical impedance plethysmography - osteoarthritis
Introduction
Osteoarthritis is a common pathological condition affecting knee joints. In Asia,
especially in India, knee joint osteoarthritis (OA) is a common disability of weight-bearing
joints due to socio-religious reasons and way of life. People generally sit on the
floor in a squatting posture for most of the time for routine work and when using
the toilet. In Western countries, hip joint osteoarthritis is a common cause of disability.[1]
[2] Obesity, trauma, genetic factors, race, etc., have been suggested as risk factors
for the genesis of OA.[3]
[4] It generally affects the elderly population and is more common and severe in women
than in men. Several reasons, such as anatomic differences in hip structures, previous
trauma, and genetic and hormonal issues have been proposed for female knee joint agony.
The anatomic differences between males and females that may play a role include narrower
femurs, thinner patellae, larger quadriceps angles, and differences in tibial condylar
size.[5] Also, the effect of menopause, i.e., paucity of estrogen may be a contributing factor.[6]
Knee joint articular cartilage is an avascular, aneuronic, and metabolically active
tissue composed of extracellular matrix (collagen and proteoglycans) and sparsely
distributed cells.[7] In normal articular cartilage, tissue fluid represents 65 to 80% of the total weight.[8] Inorganic ions such as sodium, calcium, chloride, and potassium are also found in
the fluid phase and have a fixed charge density.[9] Articular cartilage also exhibits creep and stress-relaxation responses during motion.[10] During the normal articulation of the knee, joint loading displaces the ionic synovial
fluid to the sides, causing changes in the electrical conductivity.[11] Degeneration of avascular hyaline porous cartilage is due to various etiological
factors (aging, mechanical stresses, etc.) that generate lesions in the articular
matrix, that is, pits, crevices, and micro cleft formation.[12]
[13] During the process of degradation, several proteolytic enzymes and kinins are released
by chondrocytes, altering the viscous and biochemical properties of synovial fluid.[14] Inflammatory processes further enhance the degradation process of the cartilage
matrix and the severity of OA.
Early detection of KJO may help in the initiation of early interventions and therapeutic
methodologies, which may control the progression and severity of the disease. Late-stage
diagnosis of OA when occurs when the disease progresses to a severe stage, then interventions
and therapeutic approaches may not be very useful due to the unique nature of the
structural properties of the synovial cavity articular cartilage. Several invasive
and noninvasive diagnostic methodologies for detection have been developed or in the
process of development, but they cannot diagnose early OA reliably, economically,
and simply. Well-known techniques such as X-ray,[15] computed tomography,[16] magnetic resonance imaging (MRI),[17] and arthroscopy and arthrography[18] are used for the diagnosis of KJO. Ultrasonography is relatively safe, inexpensive,
and less time-consuming. However, the ultrasound technique is exceedingly dependent
on the operator and its inability to assess deeper articular structures due to acoustic
shadowing.[18] However, these techniques have limitations and generally fail to detect early onset
KJO. There is a need for a new detection methodology for the early diagnosis of osteoarthritis,
so patients with a high risk of osteoarthritis progression can be provided early treatment
interventions.
Bera[19] and Naranjo-Hernández[20] suggested that biological cells, containing intracellular fluids (ICF), cell membranes
with or without cell walls, are suspended in the extracellular fluids (ECF) and during
excitation show a frequency-dependent behavior to an alternating electrical signal.
Under alternating electrical excitation, biological cells and tissues produce a complex
bioelectrical impedance or electrical bioimpedance.[21] The bioelectrical impedance plethysmograph (BIP) diagnostic measurement technique
is a complete, noninvasive, safe, simple, compact, and cost-effective diagnostic technique
that can provide a useful methodology and fits very well the economically weaker sections
of the population. In the present study, we used BIA for the diagnosis of knee OA.
It is an easy, non-invasive, and relatively inexpensive technique that can be performed
in almost any subject because it is portable. We suggest that, along with KL grade
distribution scale measurement, the BIP approach has a clear potential to complement
the OA diagnostic chain and make radiographic knee OA grading more objective.
Experimental Procedure
Study Design
Description of BIP
Bioelectrical impedance measurements are based on Ohm's law: Current in a circuit
is directly proportional to voltage and inversely proportional to the resistance in
a DC circuit or impedance in an alternating current (AC) circuit. Two electrodes are
used to apply AC into the body or body segment. The voltage signal from the surface
of the body is measured in terms of impedance using the additional two electrodes.[22]
Electrode System
-
In an albino rat study: 2–3 mm thick single silver wire electrodes
-
In a bull calf study: Braided silver mesh wire current electrode (width: 1.5 cm and
thickness: 4 mm) and reactant (recording) electrode (width: 8 mm and thickness: 2–4 mm).
-
In a human study: The width of current electrodes (width: 12 mm and thickness: 2–3 mm)
and reactant/recording electrodes (width: 8 mm and thickness: 2–3 mm). The width of
current electrodes was kept more to provide enhanced depth penetration of the current
in the synovial cavity. The distance between the current and reactant electrodes was
∼2 cm.
To confirm that the variations, which we observed by BIP technique, were due to alterations
in knee synovial cavity, two preliminary experiments on animals (albino rats and bull
calves) and human volunteers' were performed and pilot study results validated our
contention that the impedance of the knee joint varies in animal studies and records
do reflect some components of the synovial fluid and the AC.
Animal Studies
-
i. Albino rat knee joint study: A detailed experimental study was performed on five
male albino rats weighing between 150 and 200 g. Animals were anesthetized and all
muscles around the knee joint were removed. Silver wire electrodes were tied around
the knee joint for the impedance was measured by BIP (specification: 4 mA and 50 kHz),
and the basal value of the rat's knee joints was recorded and an impedance of 4–6
Ω was obtained. Subsequently, a tuberculin syringe was inserted into the synovial cavity
of the rat to ensure that the movements of the joint were restricted. The synovial
fluid was then removed from the knee joint cavity, and normal saline solution was
gently perfused into the knee joint cavity of rats. Again, the impedance values were
monitored on the BIP. Impedance changes were again observed and found to be in the
order of –10 ohms.
-
ii. Bull calve knee joint study: Freshly amputated knee joints of three bull calves
(age: 1–2 y) were obtained from a local slaughterhouse. Bull calve experiments were
performed in a neutral environment. Resistance to electrical resistance of the knee
joints of bull calves was measured before and after stripping of the skin and muscle
layers. Four braided band silver electrodes were tied after applying a silicone conductive
gel around the knee joint capsule above and below the lower end of the femur and proximal
end of the tibia. The current and impedance electrode distances were kept at a distance
of 2 cm, whereas the pickup electrodes were kept as close as possible to the knee
joint capsule. The base value of electrical impedance was measured by BIP (specification:
4 mA and 50 kHz) to detect the current status in the synovial cavity of the knee joints
before and after the stripping of the joint capsule. To measure the variations in
the interior milieu properties, 5 mL of normal saline was injected using a 10 mL syringe
by slowly injecting into the synovial cavity of the bull calves knee joint. After
some time, the fluid inside the joint cavity was aspirated by inserting the same syringe.
A marked variation in the impedance was observed in the bull knee joint before and
after saline injection in the synovial cavity, that is from 534 Ω to 210 Ω in the
repeated experiments. This indicates that saline causes an increase in the conductivity
inside the synovial cavity and decreases the impedance of the joint.
Human volunteer pilot study: In five clinically normal male human volunteers, knee
joints (age: 40–50 years) were selected for a human pilot study to measure electrical
impedance using the BIP technique ([Fig. 1]). A 30-minute adaptation and acclimatization period was provided to eliminate localized
muscular effects and equilibrate ionic imbalances. Two thick cotton cuffs containing
braided silver wire mesh band electrodes were mounted above and below the knee joint
after proper cleaning with a rectified spirit of the knee joint capsule and its surrounding
areas (lower extremity of femur and upper extremity of tibia). An electrocardiogram
(ECG) gel was applied to the silver wire electrodes before wrapping around the leg.
Normal Subjects showed regular minor fluctuations in the basal recording. To understand
the reason behind these minor fluctuations, a pressure cuff was placed around the
mid-thigh region and the blood supply to the knee joint was occluded. The recording
was again performed during occlusion, still, minute changes were observed before and
after occlusion in basal values, suggesting that basal resistive values of electrical
impedance will not be affected by minor pulsatile blood flow pulses and will not be
able to modify the loading variations.
Fig. 1 Schematic representation of setup for knee joint.
The results of the above-mentioned animal and human pilot studies confirm that the
BIP can be extended for the assessment of osteoarthritic subjects. Hence, the BIP
technique has been used to measure the intrinsic properties of the synovial cavity
of osteoarthritic human subjects.
Configuration of braided silver wire band electrode in human subjects: width of current
electrodes (width: 12 mm and thickness 2–3 mm) and reactant/recording electrodes (width:
8 mm and thickness 2–3 mm). The width of the current electrodes was maintained to
enhance the depth penetration of the current in the synovial cavity. The distance
between the current and reactant electrodes was ∼2 cm ([Fig. 2]).
Fig. 2 Position of electrodes in the knee joint capsule.
Clinical Study of Normal and Osteoarthritic Human Subjects
Clinical investigation on osteoarthritic subjects, 15 healthy and 15 clinically diagnosed
osteoarthritic volunteer knee joints were studied by impedance plethysmography. Anthropometric
measurements of the legs were performed to predict the approximate impedance of the
knee joint using computer analyses.
Human subjects (normal subjects age: 45 ± 5.78 and knee joint OA subjects 57.5 ± 2.34
y) leg volume constituents were skin, muscle, bones, and blood. Bodyweight (normal
[55 ± 7.83], KJO subjects [68 ± 9.52]).
Subjects Selection
-
Normal control group (NCG): 15 male normal volunteers (age: 40–50 y) before induction
were clinically assessed for no symptoms of knee joint disease on radiography or any
other ailment of the knee joint.
-
Knee joint osteoarthritic group (KOG): 15 male patient volunteers (age: 50–65 y) Clinically
diagnosed (symptomatologically and radiographically) was selected for the knee joint
OA study. OA patients were obtained from different hospitals in Delhi (India).
Experimental Protocol of Clinical Subjects
Subjects of both groups (NCG and KOG) were asked to relax for 20 to 30 minutes to
eliminate localized muscular effects and equilibrate ionic imbalances. To avoid any
motion artifacts, all subjects in the NCG and KOG groups were asked to sit on a 2.5
m long, width 1.5 m, and height 1.5 m wooden table with their legs stretched longitudinally
on the table. A wooden plank (length: 2 m width, 1.5 m length) fixed on the back of
the wall was used to support the hips and spinal region of the subjects with the knee
fully flexed on the wooden table (90° angle) to provide support to the back. Thick
fabric cotton fixed E1 and I1 and E2 and I2 electrodes after applying sufficient electrode
jelly were wrapped around the knee joint on the surface of skin joint capsule upper
and lower ends of the proximal tibia and lower extremities of the femur, as close
as possible. Velcro was used to tie the electrodes around the knee region. Impedance
variations due to two loadings were measured by a 4 mA constant current source of
50 kHz by BIP for 5 minutes. After the initial basal recording of electrical signals,
loading regimen (compressive and tractive loading) experiments were performed under
the supervision of trained technicians.
Static and Dynamic Loadings in NCG and KOG in BIP
Two types of loadings protocols were used for NCG and KOG subjects in the experimental
protocol for assessing and recording the changes in the synovial joint capsule. Changes
in the impedance were recorded during the application of the load and relaxation phases.
-
(a) Traction loading: Extension of the knee joint by applying a load of 10 kg on the
ankle: Pulling (traction-loading) was applied by a halter tied and fixed around the
lower tibial extremity and ankle via a cord running over a low friction pulley and
10 kg of the load was applied, and the responses of traction forces were recorded
after 10 minutes (stabilization time; [Fig. 3]).
-
(b) Compression loading: Pushing (compressive) loading was applied through a 10 × 4
inch flat wooden plank pressed against the sole of the foot using an electric jack
(Pilot Q-HY-1500L 12 V, USA). The force is transmitted along the longitudinal axis
of the leg. A compressive force of varying magnitude from 10 kg was applied and released
after 2 minutes and monitored and recorded ([Fig. 4]).
Fig. 3 Subjects position with traction halter knee Joint (10 kg load).
Fig. 4 Dynamic load and resting potential response of normal and osteoarthritis knee joints.
To ascertain that variations were due to tissue pathophysiology, anthropometric measurements
of the two legs were taken to predict the approximate impedance of the knee joint
by computer analysis. In addition, in every regimen phase, recordings were performed
until a consistent waveform pattern of 1 minute was obtained. The subjects' rectilinear
graphical recordings were analyzed by directly measuring the area bounded by an irregular
curve using a mathematical polar planimeter instrument (Crosby Steam Gage & Valve
Co.. Boston, USA). Planimeter only helps in the measurement of surface area on a recording
sheet to calculate the area for the assessment of changes in normal and OA subjects.
Only the resistive component of the impedance by the BIP was measured and utilized
for the assessment of the status of the interior milieu of the knee joint synovial
cavity. Basal values were obtained by dividing the value of the balance point value
to eliminate subject bias due to complicated contours and knee dimensions during normalized
resistance fluctuations. Variations in waveform amplitude change and the area under
the curve following loading and recovery states were calculated using a planimeter.
In addition, the area of deviations in waveform recording on the rectilinear recorder
below the baseline as well as above the baseline was considered positive and added
to the cumulative total. For standardization, the fluctuations that fall within a
time domain, four times the time duration of the wave corresponding to the loading
as determined from zero-crossing were included in the fluctuations. Thereafter, smaller
waves were neglected. Balance point assessment of resistive components divided by
mean basal values (quotient) provided the resistive value, which helps to eliminate
subject bias due to complicated contours and knee dimensions. In our study, the highest
waveform amplitudes obtained during the initial and loading recovery phases were measured
using a planimeter. During planimeter measurement, the areas for deviations below
the baseline and above the baseline were considered positive and added to the cumulative
total. For standardization, fluctuations that fell four times during the waveform
due to the loading from zero-crossing were included, and smaller waves were neglected.
Statistical Analysis of Data
Statistical analysis of data was performed using the Microsoft Excel Spreadsheet for
mean, mode, median analysis, and paired Student's t-test to assess the significance obtained. Resistance (capacitance) and waves (cm2/15 seconds from planimeter obtained from the rectilinear recorder and bioelectrical
impedance plethysmograph of knee joint used for the calculation. Healthy and OA subjects
data were used for analysis standard Deviation and p-value. The clinically relevant difference data between basal (resting) and loading
(tractive and compressive) was studied and recorded. Based on this assumption, independent
Student's t-test, 5% level of and test strength of 0.90, at given strength of population of 30
normal and OA subjects were calculated by analysis of variance (ANOVA). A paired t-test (basal-loading) was used to analyze the outcome at 12 months. A two-tailed (α = 0.5)
(p < 0.05) was considered statistically significant.
Results
The study was done to measure electrical impedance variations of normal and OA subjects
at resting (basal) and loading conditions by noninvasive BIP technique to confirm
that bioelectrical impedance plethysmographic method can detect properties of internal
synovial cavity material changes by surface electrodes for diagnosing OA. The results
of the above-mentioned animal and human pilot studies confirmed that the bioelectrical
impedance technique can be extended for the assessment of osteoarthritic subjects.
Normal subjects showed regular minor fluctuations in the basal recording.
To confirm that the variations we observed by our BIP technique were from the knee
joint synovial cavity, two preliminary experiments on animals (albino rats and bull
calves) and human volunteers were performed. The pilot study results validated our
contention that the impedance of the knee joint varies in animal studies and records
do reflect some components of the synovial fluid and the AC. Hence, the BIP technique
has been for the measurements of intrinsic properties of the synovial cavity of osteoarthritic
human subjects.
Tetra-polar electrodes were used to measure electrical impedance plethysmography signals
around the knees of subjects in the normal knee and KJO subjects by providing an input
current of 4 mA 50 kHz by the BIP instrument. Measurement and data recordings were
assessed using two inner electrodes in the display system in the machine to show the
values in ohms (Ω) and variations in the waveform in rectilinear recorder and calculated
by a planimeter.
[Table 1] presents the resistive data and base value (resting recording) of all normal and
showed an average of 219.37 ± 12.48 Ω, whereas osteoarthritic subjects showed 278.68 ± 18.67 Ω
measured after the stabilization of subjects in the laboratory environment, i.e.,
after 30 minutes for 5-minute assessment. The compressive loading was 219.47 ± 22.34
to 994.63 ± 218 Ω when compared with OA subjects, i.e., ∼4 times increased in comparison
with normal healthy knee joint subjects and tractive loading showed a reactant value
of 378.79 + 78.46 Ω in normal subjects compared with 767.38 + 130.67 Ω in KJO subjects.
Table 1
Mean variation of impedance responses *Ω+ in compressive and tractive loadings of
normal and osteoarthritis subjects
|
S. No.
|
Loading regimen
|
Healthy subjects
*Ω+
|
Osteoarthritic subjects
*Ω+
|
p-Value
|
|
1
|
In traction position (10 kg load)
|
378.79 + 78.46
|
767.38 + 130.67
|
< 0.001
|
|
2
|
In compression position (10 kg load)
|
219.47 +22.34
|
994.63 + 218.48
|
< 0.001
|
[Table 2] shows the mean average area measurements results obtained by planimeter (surface
area covered by waveform for 15 seconds in cm2) value of the knee joint in compressive loading of the leg (10 Kg) after planimeter
calculation showed amplitude area: cm2/15 seconds; 34.14 ± 09.19 and 201.56 ± 46.26 in the KJO subjects. The tractive loading
of the leg (10 Kg) demonstrated a mean area value of 164.67 ± 34.61 in comparison
to normal subjects' assessment value of 67.00 ± 25.26 in cm2 for 15 seconds.
Table 2
Surface area measured by the planimeter (cm2/15 seconds) at basal level and during tractive and compressive loadings and recorded
on the rectilinear recorder by BEP
|
S. No.
|
Loading regiment protocol
|
Normal knee joint (n = 30)
|
Osteoarthritic knee joint (n = 30)
|
p-Value
|
|
1
|
Compressive loading of the leg (10 Kg)
|
34.14 ± 09.19
|
201 0.56 ± 46.26
|
< 0 001
|
|
2
|
Tractive loading of leg (10 Kg)
|
67.00 ± 25.26
|
164.67 ± 34.61
|
< 0.001
|
Discussion
The objective of this study was to develop a non-invasive, simple, and cost-effective
diagnostic methodology for slowing the progress of disabling joint disorder, so active
movable life continues for a long time. Several diagnostic techniques have been developed
to diagnose the load-bearing synovial joint properties (radiography, arthrography,
MRI, ultrasound sonography, and optical coherence tomography). These detection methodologies
have several limitations and cannot provide an on-time reliable diagnosis. Due to
the complexity of joint disorders and their prevalence, several studies have been
conducted to understand their genesis, etiology, and physiopathology as well as its
diagnosis and remedial therapies. Du et al found that almost a quarter of patients
with OA on radiographic images do not complain about the symptoms of the disability.[23] Because of several discrepancies in the diagnosis of KJO, researchers are now focusing
more on prevention and treatment in the early stages of the disease.[24]
Early detection of OA is necessary because a literature survey showed that advanced
degradation of hyaline AC is untreatable. Load-bearing AC is a dynamically active
avascular aneural tissue and depends on the surrounding materials (synovial fluid).
If the OA disease process is detected at early stages, then the progress of degradation
can be prolonged, giving more years of a good life. Several conventional and non-conventional
diagnostic techniques such as arthrography, MRI, ultrasound sonography, and optical
coherence tomography (OCT) are available. It is found that present diagnostic methodologies
are not able to detect OA perfectly and have several shortcomings and cannot be used
and efficiently further limit their use in some way. The present diagnostic tools
are not compact (movement difficulty) or expensive. In addition, they cannot detect
OA at the early stages of development. OA is most prevalent in developing and poor
countries in Asia and Africa, where economic conditions and health services are in
poor shape. A literature survey revealed that the BIP technique can be used to understand
load-bearing joints. AC degeneration and degradation can be simply, safely and efficiently
measured by bioelectrical impedance plethysmography and has received immense support
for studying movable joint pathophysiology.[25]
[26]
[27]
[28]
Therefore, the present study was conducted to measure electrical impedance variations
of normal and OA subjects at resting (basal) and loading conditions by noninvasive
BIP technique for the early onset of OA. To confirm that the bioelectrical impedance
plethysmographic method was used to measure the internal properties of the synovial
cavity by surface electrodes for diagnosing OA, we performed two important preliminary
experiments on animals (albino rats and bull calves) and human volunteers. Pilot studies
indicated that the impedance of the knee joint varies in animal studies and records
do reflect some components of the synovial fluid, and the ACs and BIP technique can
be used for the measurement of intrinsic properties of the synovial cavity of humans.
In our normal volunteers, the pilot study showed minute cardiac pulsatile blood flow
oscillations in waveform recording but minor pulsatile fluctuations were not altered
during cartilaginous stresses/loading measurements. In addition, a human control study
showed similar reactant values before and after occlusion. Hence, as the biophysical
assumptions postulated earlier, a human pilot study confirmed the efficacy of measurement
by BIP of the knee joint and due to alterations in the environment of the synovial
cavity (articular cartilage/synovial fluid) rather than by other tissue structures
and intervening variables. Resistance measurement and frequency waveform recording
showed significant differences between normal and osteoarthritic subjects. Resistance
assessment showed p-value of < 0.001 ([Table 1], [Fig. 5]). Rectilinear chart recorder waveform analysis showed p < 0.001 in compression and traction loading regimen ([Fig. 6]).
Fig. 5 Bar graphs showing mean values of resistance obtained on display board (ohms).
Fig. 6 Bar graphs showing mean values of waveform recording on rectilinear recorder measured
by Planimeter (cm2/15 seconds) at basal level and during tractive and compressive loadings and recorded
on the rectilinear recorder by bioelectrical plethysmograph.
Loadings of joints provide significant variations; during compressive loading, stimulation
produced more variations than tractive loading regimens situation. This variation
may be due to different flow properties of the fluid in intrinsic contents of the
synovial cavity. A significant value of (p < 0.001) was observed in both regimens.
KJO subjects showed an ∼60% increase in the waveform during the compressive phase
of loading compared with the normal subject's knee joint. However, tractive loading
showed an ∼30% increase in OA in the waveform frequency to stress change compared
with normal subjects. Percentage comparison of compressive and tractive loadings showed
marked differences in both groups of subjects. The difference in the waveform observed
in BIP recording in compressive and tractive loading may be due to different environments
developed in stress conditions and the flow of conducting fluids in and out of the
corroded channels of the articulating surfaces. The osteoarthritic group of subjects
showed large and high-wave amplitude (oscillation) during loading in the stress phase,
it does reflect a resistive waveform pattern compared with normal subjects.
The results sometimes observed intersection of basal values of the electrical impedance
between healthy control and osteoarthritic subjects, suggesting that basal impedance
reflects the bulk resistance component of the tissue was examined and it is governed
by the anthropometric dimensions of the structure. In addition, in our study, only
the resistive component of the impedance was utilized for the assessment, because
resistive alterations provide the actual effect of loading regimen on the knee joint,
and it helps to eliminate subject bias on account of complicated contours and knee
dimensions. All waveform amplitude frequencies obtained during initial, loadings,
and recovery phases were measured by a planimeter, and the areas for deviations below
the baseline and above the baseline were considered positive and added to the cumulative
total. For standardization of values, fluctuations that fall four times during the
waveform due to the loading from zero-crossing were included, and smaller waves were
neglected. However, numerous bioimpedance studies have been performed to evaluate
the internal physiopathology of the body noninvasively using surface electrodes. However,
a literature survey showed that there are very few studies have assessed the OA noninvasively
by BIP.
Distefano et al studied the effect of pneumatic tourniquet on limb circulation during
ischemia and swelling by electrical impedance plethysmography (EIP) and found that
EIP is an accurate, noninvasive, and simple method to record the increasing periods
of a tourniquet and evaluate preventative measures as well as treatment.[29] Alvarenga et al compared human OA with normal healthy knee subjects and found a
significant difference between them (p < 0.01) and suggested bioelectrical impedance can be used to diagnose and determine
the inflammatory pathological conditions of the knee joint.[30] Later on, Neves et al studied OA and showed that bioimpedance is a sensitive technique
to assess the physiological changes associated with OA and suggested that the BIS
technique can provide a noninvasive evaluation of the diagnosis of knee OA.[31] In our study, the main emphasis was to understand that whether BIP methodology could
measure the impedance in the knee joint. In addition, a major question was whether
the variations were due to changes within the synovial cavity or due to configurational
changes in the muscle and other structures in the joint. These structures can affect
the impedance changes during the recording of the changes in the synovial cavity,
but during the loading regimen, the intervening variables changes obtained were in
the articular region. Animal studies of rat and bull knee joints validated our view.
These results indicated that the changes observed in our BIP study for the electrical
impedance assessment of the synovial cavity were due to the flow of synovial fluid
mobile ions into the porous charged matrix of the AC, which produced a change in the
conductance due to the flow of the fluid.[32]
[33]
[34]
[35] Our study recorded oscillatory type of response in all arthritic patients during
the entire phase of recording, but normal healthy joint subjects showed only low-amplitude
pulsatile blood flow during the resting phase of recording. We believe that oscillations
in OA subjects may be due to transport delays in intra- and extracellular fluid mobilization
in the articular membrane. Earlier studies also showed that corrosion and degradation
of AC interrupt the free flow of synovial fluid ions in OA cartilage, causing the
change in the conductivity of the region.[28]
[36] Assessment procedure done by us using electrical impedance detection diagnostic
technique can display its scientific efficacy, and sensitivity in comparison to other
sophisticated diagnostic technologies is presented. It is suggested that BIP can be
used along with other diagnostic technologies for the detection and diagnosis of various
ailments.
Conclusions
The results of the present study indicate that the BIP methodology of diagnosis can
measure impedance variations. This technique can be used to reflect the degenerative
conditions of the knee joints before the detection of the disease by other clinical
methodologies and the analysis of data suggests that extracellular AC matrix resistance
and reactance components can evaluate the intensity of KJO. Overall, the BIP detection
technique may provide an alternative noninvasive method for the diagnosis of KJO.
BIP is a simple, safe, and cost-effective diagnostic method. The results of this study
and experimental data confirm that the proposed method of bioelectrical impedance
evaluation, when used for the diagnosis of the knee, is a valid and reliable method
to determine the pathological conditions of the knee joint. In addition, the cost-effectiveness
of BIP technology may help reduce the health burden of knee OA. The articular cartilage
of the joint is a dynamic tissue that responds to changes in loading conditions. It
is well accepted that regular loading of AC within physiological limits throughout
life is necessary to maintain normal joint homeostasis. The bioelectrical impedance
of the knee was assessed using tetrapolar silver band electrodes. A constant current
of 3 mA at 20 kHz was generated by BIP. Impedance was measured by balancing the resistive
and responsive components on a rectilinear recorder. Normal and clinically diagnosed
KJO subjects were studied in compressive and traction phases and showed significant
differences in the properties of electrical signals.
