| dc.description.abstract | This study aimed at evaluating the clinical, radiographic, pathological, light and
electron microscopic features of osteoarthritis of the hip joint in adult dogs in
Kenya. Thirty-six adult German shepherd dogs were used [15 female (41.6 %)
and 21 (58.3 %) male]. The mean weight of the animals was 27.3 kgs (range: 18.3
- 44.3 kgs). The mean age was 9.3 years (range: 5-17 years). History, visual
inspection and clinical examination for lameness were used to classify the dogs as
normal, with mild or severe osteoarthritis; assigned numbers 1, 2 and 3,
respectively.
Dogs were classified as clinically normal when they exhibited normal
conformation of the hindlimbs, normal gait and posture, good muscle cover of the
hindlimbs and no clinical signs of hindlimb lameness. Dogs with mild lameness
exhibited slight muscle atrophy, pain on flexion and extension of the hip joint,
limited range of joint motion and mild lameness attributable to the hip joint. Dogs
with severe hindlimb lameness had a history of prolonged lameness of the
hindquarters, severe muscle atrophy and change in conformation of the hindlimbs,
crepitus and pain on flexion and extension of the hip joints and decubital wounds
on the paws of affected hindlimbs.
Standard pelvic ventrodorsal radiography was performed with the dogs under
deep sedation or general anesthesia. The radiographs were evaluated based on
subjective radiographic features of each joint and further classified into four broad
categories. Grade 0 had C-shaped acetabulum, dorsal rim rounded and distinct
femoral neck. Grade I had shallow acetabulum or marked dorsal rim attenuation,
moderately osteophytic acetabular margin, rounded femoral head and minimal
osteophytes on the femoral neck. Grade 2 had shallow acetabulum or marked
dorsal rim attenuation, moderately osteophytic acetabular margin, flattened
femoral head and shortened femoral neck with osteophytes. Grade 3 had flat
acetabulum, severely osteophytic acetabular margin, markedly flattened or
irregular femoral head and severely shortened femoral neck with osteophytes.
Thirty-two animals were euthanised by intravenous injection of pentobarbitone
sodium (EuthatalR Rhone Meriux Ltd, Dublin). The muscles on the femur and
pelvis were dissected and the femur disarticulated at the stifle joint. A band saw
was used to cut the pubis, the ischium and the ilium to isolate the femoral head
and acetabulum. The joint capsule was then incised, exposing the joint cavity.
Sixty-fourhip joints were evaluated for pathological changes.
The integrity of ligamentum capitis femoris was determined by visual inspection
of each joint. The ligament was severed at its attachment to the fovea capitis and
the acetabulum, and its volume (in milliliters) determined by a water displacement
technique. The data was compared based on radiographic grades of osteoarthritis.
The color, relative thickness, texture and villous hypertrophy of synovial
membrane were determined and recorded for each joint. Synovial membrane
samples were collected, fixed in 10% formalin solution and routinely processed.
5 urn thick sections were prepared and stained with hematoxylin and eosin and
examined with a light microscope. Samples were classified according to
previously described criteria.
Zero (0) score had normal tissue. Score one (1) had mild synovitis, which
revealed focally thick synovium with plumper hypertrophied cells, sometimes
producing a small-localized thickening (plaque) or villous extension. Score two
(2) was defined as synovial proliferation which involved 50% to 75% of the
surface examined. Villi were longer and more common, sometimes also lined by
hyperplastic synovium. Capillary neovascularization and mild mononuclear cells
infiltrates were sometimes observed in the adjacent collagenous stroma. Score
three (3) had synovial proliferation involving the entire surface. Villous
proliferation varied from numerous small structures to a mixture of small and
large, stout villi. Lymphocyte infiltrates were heavier with focal aggregation in
some cases. In score four (4), at times islands of cartilage from the eroded
articularsurface were embedded in the synovium.
Gross pathological changes on articular cartilage were used to classify the extent
of hip osteoarthritis in the study. Slabs of cartilage from the femoral head and
neck were cut using a band saw. The slabs were fixed in 10% formalin for 7-14
days and decalcified in 10% nitric acid for 3-4 weeks. The decalcified slabs were
trimmed and embedded in paraffin wax. Sections, 5 urn thick, were prepared and
stained with either hematoxylin and eosin or Safranin-O-Fast Green. Twenty-two
representative samples of articular cartilage sections were examined with a light
microscope and graded according to previously described criteria.
Articular cartilage and synovial membrane samples collected from 4 dogs (8
joints) were immersed in 3 % glutaraldehyde in 0.1M cacodylate buffer (pH 7.2)
and fixed for 4 hours at 40 C. After the material was washed with buffer, it was
postfixed in 1 % osmium tetroxide for one hour at 4 0 C and then soaked for one
hour in 0.5 % uranyl acetate. The samples were dehydrated in a graded series of
ethanol and embedded in plastic. Semi-thin sections were stained in toluidine blue
and examined with a light microscope for orientation of special areas of interest to
be obtained for ultrastructural study. Gray to silver thin sections were picked up
on copper-coated 200 mesh grids and stained in 2 % uranyl acetate and lead
citrate. Electron micrographs were taken with transmission electron microscope
(JEOL 1010, GMBH, Germany). The morphology of chondrocytes and
synoviocytes was qualitatively evaluated to outline their response in chronic
synovitis and osteoarthritis.
Fourteen (38.9 %) dogs were clinically normal, while 22 (61.1 %) had either mild
or severe hindlimb lameness attributable to the hip joint. Of the 22 animals with
hindlimb lameness, six (16.7 %) had mild, while 16 (44.4 %) had severe and
debilitating lameness that required euthanasia.
Thirty-seven (51.4 %) hip joints had normal radiographic features and were
assigned grade o. On the other hand, 11 (15.3 %) hip jo ints were graded 1, 8 (11.1
%) hip joints were graded 2, while 16 (22.2 %) hip joints were graded 3.
Ligamentum capitis femoris was intact in 46 (71.9 %) joints but was missing in
18 (28.1 %) of the 64 hip joints. The mean volume of ligamentum capitis femoris
for grade 0 hip joints was 0.82 ± 0.3462 mls, while the mean for grade 1 hip joints
was 0.65 ± 0.2544 mIs. The mean volume of ligamentum capitis femoris for grade
2 hip joints was 0.31 ± 0.5551 mIs, while all the hip joints with radiographic
grade 3 had no intact ligamentum capitis femoris, with mean volume of 0 mls.
There were significant differences (p < 0.05) between the mean volume of
ligamentum capitis femoris among the four radiographic grades of osteoarthritis.
There was an inverse correlation (r =-0.75) between the mean volume of
ligamentum capitis femoris and the radiographic grades of osteoarthritis of the hip
joints. The mean volume of ligamentum capitis femoris decreased (from 0.82 mls
in normal hip joints) with increasing severity of radiographic grade of
osteoarthritis (to 0 rnls in severe osteoarthritis).
Synovial membrane from 27 normal hip joints (48.2 %) had normal size, color
and no gross pathological changes. In contrast, synovial membrane from 29
osteoarthritic hip joints (51.8 %) had either synovial hyperplasia, gross
thickening, discoloration and irregular shape and cartilaginous or bone
transformation. From the severely inflamed samples, osteochondromatosis (joint
mouse) was observed in 12 hip joints (21.4 %) either as free floating within the
joint cavity or embedded within the synovial membrane. Nine hip joints had white
colored, firm masses (the largest was 1.5 x 1.0 em; the smaller masses were
approximately 0.1 x 0.2 em in diameter) within the joint cavity. Cartilage and
bone tissue was demonstrated by light microscopic examination of a
representative sample.
Twenty-two (34.4 %) of the 64 hip joints had normal anatomical appearance,
while 11 (17.2 %) had gross pathological signs of mild osteoarthritis. Seven (l0.9
%) hip joints had gross pathological signs of moderate osteoarthritis, while 24
(37.5 %) hip joints had gross pathological signs of severe osteoarthritis.
Electron rrucroscopy of synovial tissue revealed extensive fibrosis and
preponderance for electron dense deposits indicative of calcification, synoviocyte
metaplasia, capillary vascularization and various stages of cell degeneration.
Chondrocyte proliferation, degeneration, and eventual death were encountered in
articular cartilage tissue. These observations were noted in clinically and
radigraphically normal animals as well as in those with severe osteoarthritis.
These changes could be related to age and severe synovitis associated with
osteoarthritis.
This study has documented the clinical, radiographic and pathological features of
naturally occurring hip dysplasia and osteoarthritis in adult dogs. The data is
useful in predicting the likelihood of dogs to develop hip osteoarthritis and to
determine the clinical severity of the disease. Clinical examination and ventrodorsal
pelvic radiography are none-invasive diagnostic aids for the determination
of the existence and severity of this condition. Thus, the data is useful in judicial
management and control of canine hip dysplasia and osteoarthritis. Further, the
data could be used for future studies to determine the prevalence of hip
osteoarthritis and the impact of current measures to control the incidence of
canine hip dysplasia in Kenya | en |
