AGE RELATED ANATOMICAL CHANGES IN ARTICULAR CARTILAGE OF HIP JOINT OF BUFFALO (Bubalus bubalis)
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Date
2021-08-06
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PVNRTVU, HYDERABAD
Abstract
“Age related anatomical changes in articular cartilage of hip joint of Buffalo
(Bubalus bubalis)” was conducted to study in detail the anatomical features of
articular cartilage in twenty four intact hip joints of apparently healthy buffaloes
procured from GHMC Abbattoir, Hyderabad. Proximal epiphysis of femur and intact
acetabulum were taken afresh and divided into four groups viz., Group I (prenatal),
Group II (Birth - 3yrs), Group III (3 – 6 yrs) and Group IV (6 yrs and above). Gross
and morphometric details like thickness of femoral head and acetabular AC, width of
acetabular AC, average diameter and depth of acetabular cavity coupled with
microscopic and SEM features of AC in fresh tissue samples were studied by H & E,
Van Gieson‟s, Masson‟s trichrome and Safranin „O‟ stains and SEM facility at Ruska
labs respectively.
Morphological features of AC of femoral head and acetabulum revealed that
both articular surfaces were covered by a strip of AC made up of hyaline cartilage
adjacent to sub-chondral bone in post-natal groups, whereas in prenatal stage entire
proximal epiphysis of femoral head and acetabulum was purely hyaline cartilage since
AC was not yet differentiated. In post-natal groups (II, III and IV) a layer of mature
AC covered the hemispherical femoral head entirely and also the lunate part of
acetabulum.
Femoral head AC blended peripherally with epiphyseal cartilage and covered
the surface of the neck merging into cartilaginous structure of the trochanter.
Thickness of femoral head AC reduced marginally with advancing age in various
points of articular surface of femoral head viz., lateral surface, at neck and at
midpoint. It was 1.89 mm, 1.38 mm and 1.49 mm thick in Gr-II which reduced to 1.64
mm, 1.37 mm and 1.36 mm in Gr-IV respectively. As age advanced, average length
and width of femoral head increased fivefold from 2.83 and 2.43 cm in Gr-I (prenatal)
to nearly 10.77 and 9.43 cm in Gr-IV (postnatal) specimens respectively. Surface of
AC in young specimens was shiny pink in color in fresh state, whereas aged
specimens it showed signs of yellowish discoloration and few indentations around the
neck.
Acetabular AC in post natal groups was continuous on antero-lateral and
caudo-lateral aspects i.e., towards ilium and ischium respectively, whereas at medial
part i.e., towards pubis it was separated on either side. Mean AC thickness of
acetabulum at three points showed slight variation. Overall average width of
acetabular AC increased with age viz., 23.85 mm to 28.95 mm in Gr- IV, whereas the
dimensions of acetabulum like the diameter and depth revealed a steady increase with
advancing age. In Gr-I thickness and width were 0.35 cm and 0.4 cm, which
increased up to 5.38 cm and 4.11 cm in Gr – IV respectively. Irregular erosions
towards centre of acetabulum were seen on AC surface in aged specimens of groups
III and IV.
Microscopic features of articular surface of femoral head in prenatal stage (Gr-
I) was smooth and made up of hyaline cartilage. Increased cellularity was observed
with slight eosinophila of matrix towards the surface. Superficial zone showed
tangentially oriented flat and elongated, oval chondrocytes with dense nuclei
randomly arranged in close proximity. Cartilage canals of different shapes were seen
in deeper zone.
In post-natal specimens from Gr-II onwards, femoral head AC was clearly
seen over sub-chondral bone and its matrix comprised four zones viz., superficial zone
accounting to 5 – 10 % of total AC thickness (TAT), second zone was almost 50 % to
60% of TAT followed by third zone, which was 20 to 30 % of TAT. Innermost
calcified zone accounted to 10% of TAT. A clear tide mark separated deeper and
calcified zones in femoral head AC in post natal specimens. Cellular profile of
femoral head AC in post natal groups showed spindle shaped chondrocytes arranged
tangentially to surface in first zone followed by a wide second zone with polymorphic
chondrocytes in isogenous groups. Deeper third zone had cell nests oriented
perpendicular to surface. Calcified zone was adjacent to irregularly outlined clear
tidemark separating it from deeper zone. It consisted atrophied chondrocytes in
moderate ICM. Age related changes were seen in femoral head AC, such as in Gr-IV
there was decrease in number of chondrocytes within mid zone and large single
chondrocytes adjacent to sub-chondral zone in pyknotic state.
Microscopic features of acetabular AC showed that it was entirely
cartilaginous in prenatal stage of Gr-I since AC was not yet differentiated. Articular
surface was smooth with numerous chondrocytes in random arrangement in second
zone. Large chondrocytes were in homogenous cartilage matrix in mid zone amongst
cartilage canals. Acetabular AC was appreciable in all post-natal groups since it was
clearly differentiated from underlying sub-chondral bone. Ligamentous tissue of
acetabular labrum infiltrated into the AC on one side in specimens of groups II, III
and IV. Deeper zone closer to tide mark showed larger chondrocytes in isogenous
groups and calcified zone showed atrophied chondrocytes with few areas of
calcification. In group III and IV specimens of five and half and eight years old
surface of acetabular AC was uneven in outline. Second zone showed slightly large
and oval chondrocytes in lacunae and deeper zone above the calcified part consisted
elongated chondrocytes arranged in perpendicular columns. Acetabular labrum
blended with AC of acetabulum at one side invaded by bundles of collagen.
Superficial zone was devoid of chondrocytes in AC of Gr-IV specimens.
Scanning electron microscopic features of articular surface of femoral head
AC in Gr-I revealed a continuous surface without any break with longitudinal folds
and numerous tightly packed chondrocytes, which were unidirectional and protruding
outwards, separated by fine grooves. At much higher magnification uniformly
dispersed chondrocytes protruded as hemispherical, irregular or spindle-shaped
elongations, whose size ranged from 6.01 μm to maximum 8.39 μm.
In Gr-II and III specimens AC surface of femoral head under SEM was
smoother with few erythrocytes on surface. Protrusion of chondrocytes along with
numerous minute debris of synovial fluid secretions was seen. At the junction of AC
and sub-chondral bone cartilage matrix was smoother and osseous part comprised
collagen fibres. Femoral head AC surface in specimens of Group III and IV revealed
an uneven outline with deeply located cells and remnants of synovial fluid. Few cells
were surrounded by a furrow caused by collapse of pericellular matrix. In group IV
cross sectional SEM AC surface of femur showed finely cracked up longitudinal
fissures with empty lacunae.
Scanning electron microscopic features of prenatal stage of group I acetabular
articular surface showed evenly outlined surface with fine longitudinal fissures and
numerous chondrocytes along with few erythrocytes. AC was not yet differentiated at
this stage.
Whereas the AC surface of acetabulum in Gr-II consisted of pit like lacunae at
the junction with sub-chondral bone. On higher magnification surface was uneven
showing erosion like areas. In group III specimens cross sectional SEM features
displayed chondrocytes in pairs of two or more in tiny pit like elliptical lacunae with
minute secretions in few places. In the last group viz., Gr-IV the AC surface was
uneven and mostly devoid of cells with large inter-cellular matrix and in few places
granularity and patches of wear were noticed. Rough elevations giving an irregular
appearance to AC along with few protruding cells were a feature in this group. Subchondral
bone in post natal groups in SEM displayed thick bony trabaculae with wide
spaces in between.