PHYSIOCHEMICAL AND CYTOLOGICAL CHARACTERISTICS OF SYNOVIAL FLUID IN THE CARPAL JOINT OF MIXED-BREED GOATS
The carpal joint in goats is subject
to diseases such as caprine arthritis encephalitis, leading to pain and
a reduction in movement. Due to the scarce records of normal
parameters, the aim of the present study was to assess the
physiochemical and cytological make up of the synovial fluid in the
carpal joint of 44 mixed-breed goat without joint disease. The
following physiochemical characteristics were assessed: volume (0.94mL
± 0.26 mL), color (colorless to yellow), turbidity (46.50% were
limpid), mucin precipitation (firm coagulant in limpid solution) and
concentration of total proteins (1.95 ± 0.87 mg/dL). Cytological
assessment consisted of global and differential leukocyte counts. The
mean global count was 48.02 ± 24.47 cells/µL. The differential count
was 25.07 ± 15.86 lymphocytes/µL and 16.31 ± 12.63 large mononucleated
cells/µL. It is suggested that the parameter values obtained in the
present study may be considered normal for synovial fluid in the carpal
joint of adult mixed-breed goats.
KEY WORDS: Carpus, goat, joint, synovia.
CARACTERÍSTICAS FÍSICO-QUÍMICAS E CITOLÓGICAS DO LÍQUIDO SINOVIAL DA ARTICULAÇÃO DO CARPO DE CAPRINOS MESTIÇOS
A articulação do carpo dos caprinos é
alvo de enfermidades, como a artrite-encefalite caprina, levando à dor
e à redução dos movimentos. Devido à falta de registro de parâmetros
normais, este estudo avaliou a constituição físico-química e citológica
do líquido sinovial da articulação do carpo de 44 caprinos sem raça
definida, que não apresentavam doença articular. Os parâmetros
físico-químicos avaliados foram volume (0,94 mL ± 0,26 mL), cor
(incolor a amarelo), turbidez (46,50% apresentaram-se límpidas),
precipitado de mucina (coágulo firme em solução límpida) e concentração
de proteínas (1,95 ± 0,87 mg/dL). Os dados citológicos corresponderam
às contagens global e diferencial de leucócitos. A contagem global
média encontrada foi de 48,02 ± 24,47 células/µL e contagem diferencial
com 25,07 ± 15,86 linfócitos/µL e 16,31 ± 12,63 grandes células
mononucleadas/µL. Sugere-se que os valores obtidos nesta pesquisa sejam
considerados parâmetros normais para o líquido sinovial do carpo de
caprinos adultos sem raça definida.
PALAVRAS-CHAVES: Articulação, caprino, carpo, sinóvia.
Synovial fluid is a dialysate of
plasma that also contains substances secreted from the joint tissue
itself, including relatively high amounts of hyaluronic acid (PARRY,
1999). The main function of synovial fluid is to lubricate and nourish
the joint cartilage, which has no blood vessels, lymph vessels or
nerves (PARRY, 1999). Analysis of synovial fluid is performed in order
to identify cytological and physiochemical abnormalities in suppurative
and non-suppurative inflammatory conditions, hemorrhages, malignant
tumors or infectious diseases. The abnormalities are used together with
clinical and historical signs to determine the treatment and prognosis.
Evaluations in series assist in the assessment of the response to
therapy. The removal of accumulated fluid and inflammatory products
from the distended joint capsule may relieve symptoms (KIEHL, 1997).
One of the advantages of a synovial fluid exam is the ease of
execution, as it can be performed with a minimum of equipment in a
short space of time (PARRY, 1999). Woodard et al.
(1982) reported that the main clinical abnormality in caprine arthritis
encephalitis (CAE) in specimens of various ages (including six weeks of
age) was the occurrence of hygroma. While this lesion is not specific
to CAE, the frequency of hygromas was greater and the lesions more
severe than that expected in goat populations unaffected by this
As in other organic fluids, the assessment of synovial fluid may be
divided into three categories, according to BOON (1997): physical
(color, volume, turbidity), chemical (concentration of total proteins
and formation of mucin precipitate) and cytological (nucleated cell
count and swab analysis). A number of studies report the analysis of
synovial fluid in dogs (BOON, 1997; PARRY, 1999), humans (SUGIUCHI et al.,
2005; BRANNAN & JERRARD, 2006) and horses (VAN PELT, 1974) in
either normal or pathological conditions. Laboratory findings
determined a large number of mononucleated cells in the synovial fluid.
Therefore, analysis of this fluid can assist in the diagnosis in
distinguishing arthritis caused by CAE from other inflammatory joint
diseases caused by bacteria or mycoplasmas, in which polymorphonuclear
leukocytes are the predominant cells (WOODARD et al., 1982).
Synovial fluid in goats has been analyzed in the presence of arthritis encephalitis (WOODARD et al.,
1982). However, the scarcity of studies on normal values of synovial
fluid components in the carpal joint of goats hampers the
interpretation of results.
Thus, the aim of the present study was to contribute toward knowledge
on normal physiochemical and cytological characteristics of synovial
fluid of the carpus in adult goats.
Forty-four male mixed-breed goats
were used. The animals had the following characteristics: age between
six and 18 months; no history of joint disease; obtained from the
Buíque Municipal Slaughterhouse, state of Pernambuco, Brazil; with
negative serological evaluation for lentivirus as determined by the
agar-gel immunodiffusion test (Biovetech®).
Synovial fluid collection was performed on the carpal joint, from the
right and left antimeres, in the antebrachiocarpal and mediocarpal
portions of the joint, using a 25x8 hypodermic needle and 5-mL
disposable syringe. Immediately following collection, the samples were
homogenized, stored in a recipient with thermal isolation and promptly
sent to the laboratory for analysis.
The synovial fluid from each joint was aspirated until completely
drained for the evaluation of volume, color and turbidity. The
concentration of total proteins was determined by refractometry,
following the procedure described by MAHAFFEY (1992), after the
addition of a 10% EDTA solution.
Analysis of the quality of the mucin precipitate was determined by the
addition of 0.1mL of 7N glacial acetic acid to 4 mL of distilled water
in a test tube. The resulting solution (2.5%) was gently added to a
0.5-mL aliquot of synovial fluid, with care taken so that the sample
did not come into contact with the wall of the test tube. The
interpretation of the result was performed based on the criterion
recommended by VAN PELT (1974): normal = firm coagulant in limpid
solution; regular = soft coagulant in slightly turbid, yellowish
solution; poor = small, friable mass in turbid, light yellow fluid; and
very poor = few flakes in turbid, light to dark yellow fluid.
For the cytological analysis, EDTA was added to the synovial fluid
samples. Global nucleated cell counts were performed with a Neubauer
hemocytometer (BOON, 1987). Swabs of synovial fluid were stained with
Rapid Panoptic and analyzed under an optical microscope Olympus BX50®.
Nucleated cells were classified as neutrophils, eosynophils,
lymphocytes and large mononucleated cells.
All variables, except the categorical variables (color, turbidity,
quality of mucin precipitate) and percentages obtained in the
differential leukocyte count were analyzed for normality and
homogeneity of variance and transformed, when necessary, prior to the
statistical analysis. Regarding the variables investigated to determine
possible significant differences between the right and left antimeres,
multivariate analysis of variance (MANOVA) was used for volume,
concentration of proteins and global count of nucleated cells.
Univariate analysis of variance (ANOVA) was then applied in order to
explain any differences detected by MANOVA. The remaining variables
were compared using the chi-square test. Volume, concentration of total
proteins, global count of nucleated cells and percentage values of the
differential count of nucleated cells (leukocytes) were submitted to
the “bootstrap” re-sampling method with 1000 replications in order to
establish the most reliable parameters, with a 95% confidence interval.
RESULTS AND DISCUSSION
The samples analyzed were viscous and had a mean volume of 0.94 ± 0.26 mL (Table 1
VAN PELT (1974) reports that the total volume of synovial fluid
aspirated from any joint varies in proportion to joint size and its
communication with another joint. SUGIUCHI et al
(2005) and BRANNAN & JERRARD (2006) state that viscosity is reduced
in inflammatory states due to the reduction in hyaluronic acid polymers
by lysosomal enzymes produced primarily by neutrophils as well as cells
from the capsule and synovial cartilage. Variation in volume and
composition of synovial fluid indicates a pathological alteration,
especially inflammatory processes. In studies carried out on dogs,
sample volumes ranged from 0.01 to 1 mL and from 0.20 to 1 mL for each
The color of the synovial fluid samples in the present study ranged
from colorless to dark yellow: 41.90% colorless, 30.20% dark yellow and
27.00% light yellow. Regarding turbidity, 46.50% of the samples were
classified as limpid, 41.90% were semi-turbid and 11.60% were turbid (Table 1
According to BRANNAN & JERRARD (2006), turbidity is generally
related to the leukocyte count, with higher counts correlated to
greater turbidity. Normal synovial fluid is limpid and its coloration
ranges from colorless to light yellow (BOON, 1997). According to
WILKINS (1993), an increase in turbidity suggests an increase in white
blood cell count and a change in color indicates either a hemorrhage or
iatrogenic contamination by blood at the time of collection.
Mean protein value in the present study was 1.95 ± 0.87 g/dL (Table 1
The concentration of proteins in synovial fluid is generally low and
few studies report these values. However, a study carried out on dogs
by FERNANDEZ et al
PARRY, 1999) reports a normal protein concentration between 1.80 and
4.80 g/dL. According to BANKS (1992), proteins with low molecular
weight, which are immunologically and electrophoretically identical to
plasma proteins, are found in low concentrations in synovial fluid.
KOLB (1984) states that the amount of proteins in synovial fluid is
approximately 1% and made up mainly of albumin, globulins and mucin.
Higher protein values occur during inflammatory processes, along with
the presence of larger proteins in the synovial fluid, such as
The quality of the mucin precipitate in all samples analyzed was
considered normal, based on the VAN PELT (1974) classification– firm
coagulant in a limpid solution (Figure 1
; Table 1
The mucin precipitate test indicates both quality and concentration of
hyaluronic acid (BOON, 1997) and it is a reliable indicator of the
polymerization of hyaluronic acid in synovial fluid and a qualitative
measure of its concentration in normal and pathological synovial fluid
(VAN PELT, 1974). According to SUGIUCHI et al
(2005), in the presence of inflammation, enzymes in the synovial fluid
break down the hyaluronate molecules, thereby increasing the volume of
synovial fluid and reducing its viscosity.
Regarding the cytological analysis, the mean global nucleated cell count was 48.02 ± 24.47 cells/µL (Table 2
According to PARRY (1999), the nucleated cell count in normal synovial
fluid varies according to the joint. A number of studies have
established parameters for healthy joints, which generally have an
overall count of less than 3000 cells/µL. According to BRANNAN &
JERRARD (2006), the global cell count is an important exam for the
classification of both inflammatory and non-inflammatory processes in
joints. A study carried out by MARTINS et al
(2007) on the femoropatellar joint of horses found a correlation
between viscosity and leukocyte count, in which the animals with no
alteration in viscosity had leukocyte counts below 250 cells/µL and
therefore had no joint inflammation. This corroborates the findings of
the present study regarding global white blood cell count and viscosity
of the synovial fluid in the carpal joint of goats, in which 100% of
the samples had global cell counts below 250 cells/µL.
In the differential leukocyte count (Figure 2
there was a predominance of lymphocytes over the other cell types
encountered, representing 59.50% of the total, with values ranging from
0 to 53 cells/µL. The count of large mononucleated cells was 35.80%,
ranging from 0 to 44 cells/µL (Table 2
The other leukocytes had low frequencies, such as neutrophils, which
had constant values of 1 cell/µL. According to PARRY (1999), large
mononucleated cells have a phagocytic potential and their origin is
unknown; they may be derived from blood monocytes, tissue macrophages
or cells from the synovial membrane.
The author found neutrophils at percentages below 5%, an absence of
eosinophils, variable lymphocyte values (mean of 44%) and large
mononucleated cells in a considerably variable proportion. These
findings are similar to those obtained in the present study on the
carpal joint of goats.
In inflammatory processes in joints, synovial fluid generally has a very poor quality mucin precipitate (FERNANDEZ et al
1983) as well as an increased concentration of total proteins (VAN
PELT, 1974) and a nucleated cell count between 4000 and 370,000
cells/µL (NELSON & COUTO, 1994). In degenerative joint disease,
there is a slight increase in the volume of the synovial fluid and a
reduction in its viscosity (WILKINS, 1993).
This research enhances data of characteristics of ovine synovial fluid.
According to VAN PELT (1962), once normal physiochemical and
cytological characteristics of the synovial fluid are known, these data
may be employed to assess different types of arthritis as well as
establish an early diagnosis and prognosis, determine the joint
response to anti-arthritis and local and systemic anti-bacterial
therapies, clarify the etiology and assist in the classification of
diverse disease types.
It is suggested that the synovial fluid of the carpal joint of adult
mixed-breed goats must have as volume 0.94 ± 0.26 mL; total protein
1.95 ± 0.87 mg/dL and it must be colorless, limpid, with firm mucin
precipitate in limpid solution. Cytological characteristics as number
of global nucleated cells of 48.02 ± 24.47 cells/µL; number of
lymphocytes 25.07 ± 15.86 cells/µL and large mononucleated cells 16.31
± 12.63 cells/µL may be considered normal for the synovial fluid of the
carpal joint of this specie.
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