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Shape of wear particles found in human knee joints and their relationship to osteoarthritis

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Shape of wear particles found in human knee joints and their relationship to osteoarthritis

Abstract

To analyse and compare the shape of wear particles found in healthy and osteoarthritic human knee joints for monitoring the progress of osteoarthritis, the long-term prognosis and to evaluate therapeutic regimens. Joint particles from seven patients with normal cartilage in all compartments of the knee joint, 12 patients with fibrillation of less than half the cartilage thickness (grade 1), seven patients with fibrillation of more than half the cartilage thickness (grade 2) and four patients with erosions down to bone (grade 3) were analysed. A total of 565 particles were extracted from synovial fluid samples by ferrography and analysed in a scanning electron microscope. A number of numerical descriptors, i.e. boundary fractal dimension, shape factor, convexity and elongation, were calculated for each particle image and correlated to the degree of osteoarthritis using non-parametric tests. Experiments demonstrated that there were significant differences between the numerical descriptors calculated for wear particles from healthy and osteoarthritic knee joints (P < 0.01), suggesting that the particle shape can be used as an indicator of the joint condition. In particular, the fractal dimension of the particle boundary was shown to correlate directly with the degree of osteoarthritis. Numerical analysis of the shape of wear particles found in human knee joints may provide a reliable means for the assessment of cartilage repair after surgical or conservative treatment of osteoarthritis.
British Journal of Rheumatology 1998;37:978–984
SHAPE OF WEAR PARTICLES FOUND IN HUMAN KNEE JOINTS AND THEIR
RELATIONSHIP TO OSTEOARTHRITIS
M. S. KUSTER, P. PODSIADLO* and G. W. STACHOWIAK*
Klinik fu
¨
r Orthopa
¨
dische Chirurgie, Kantonsspital, 9007 St Gallen, Switzerland and *Tribology Laboratory, Department of
Mechanical and Materials Engineering, The University of Western Australia, Nedlands, WA 6907, Australia
SUMMARY
Objective. To analyse and compare the shape of wear particles found in healthy and osteoarthritic human knee joints for
monitoring the progress of osteoarthritis, the long-term prognosis and to evaluate therapeutic regimens.
Method. Joint particles from seven patients with normal cartilage in all compartments of the knee joint, 12 patients with
fibrillation of less than half the cartilage thickness (grade 1), seven patients with fibrillation of more than half the cartilage
thickness (grade 2) and four patients with erosions down to bone (grade 3) were analysed. A total of 565 particles were
extracted from synovial fluid samples by ferrography and analysed in a scanning electron microscope. A number of numerical
descriptors, i.e. boundary fractal dimension, shape factor, convexity and elongation, were calculated for each particle image
and correlated to the degree of osteoarthritis using non-parametric tests.
Results. Experiments demonstrated that there were significant dierences between the numerical descriptors calculated for
wear particles from healthy and osteoarthritic knee joints (P < 0.01), suggesting that the particle shape can be used as an
indicator of the joint condition. In particular, the fractal dimension of the particle boundary was shown to correlate directly
with the degree of osteoarthritis.
Conclusion. Numerical analysis of the shape of wear particles found in human knee joints may provide a reliable means for
the assessment of cartilage repair after surgical or conservative treatment of osteoarthritis.
K : Wear particles, Numerical descriptors, Synovial joints, Osteoarthritis, Ferrography.
S studies revealed that radiological features do of ferrography to the analysis of wear particles present
in synovial fluid. This early analysis of particles, how-not permit a confident prediction of the status of
articular cartilage. Plain radiographs, in general, signi- ever, was based on a subjective visual classification.
Recently, fractal methods have been applied to charac-ficantly underestimate the extent of cartilage damage
[13]. The osteoarthritic deterioration of the joint terize the complexity of wear particles generated in
synovial joints [9–11]. In the present study, the hypo-cartilage begins long before a radiological diagnosis
can be made. Our inability to diagnose the disease thesis that numerical descriptions of wear particles can
be used to detect early osteoarthritic changes and toduring the pre-radiological stages is a reflection of the
paucity of methods available for monitoring the joint improve further the understanding of wear mechanisms
in synovial joints was investigated.cartilage in vivo. Although magnetic resonance imaging
improved, to some extent, the diagnosis of
osteoarthritis (OA), it underestimates, due to a limited
MATERIAL AND METHODS
resolution, the degeneration of cartilage as compared
Thirty patients undergoing arthroscopy were selected
to arthroscopy [1]. Arthroscopy still appears to be the
for the study. The mean age was 43 yr, ranging from
most sensitive diagnostic tool in the evaluation of OA
16 to 79 yr. During arthroscopy, the degree of OA in
[1, 4]. At present, there are no practical less invasive
the patient’s knee joints was assessed. Articular cartil-
tests available to detect early OA. There is a clear need
age lesions were graded on a three-point scale, accord-
for a better assessment of disease progress, long-term
ing to the most severe lesion found—grade 1 OA:
prognosis and for the evaluation of therapeutic
cartilage lesion exhibiting fibrillations or fissures with
regimens.
less than half the cartilage thickness; grade 2 OA:
OA is a heterogeneous group of conditions which
cartilage showing fibrillation or fissures with more than
are associated with defective integrity of articular cartil-
half the cartilage thickness; grade 3 OA: severe cartilage
age, in addition to related changes in the underlying
erosion down to the bone.
bone and the joint margins [5]. It was found that the
Samples from seven healthy joints with a normal
destruction of articular cartilage accelerated by the
cartilage in all three compartments, 12 patients with a
wear processes occurring in synovial joints would result
grade 1 OA, seven patients with a grade 2 OA and
in distinct wear particles, which can be captured and
four patients with a grade 3 OA were analysed.
identified by scanning electron microscopy (SEM ) [6 ].
A standing antero-posterior, a lateral and axial
Evans et al. [68] were the first to apply the technique
X-ray at 30° of the knee joint were taken on the day
of admission. The radiological degree of OA in these
patients’ knee joints was assessed for each compart-
Submitted 15 December 1997; revised version accepted 12 May
ment according to the grading system of Kellgren and
1998.
Lawrence [12]. Arthroscopic and radiological findings
Correspondence to: M. Kuster, Klinik fu
¨
r Orthopa
¨
dische
Chirurgie, Kantonsspital, CH 9007 St Gallen, Switzerland.
for each compartment are shown in Table I. Twelve
© 1998 British Society for Rheumatology
978
KUSTER ET AL.: WEAR PARTICLE SHAPE IN KNEE OA 979
TABLE I
Arthroscopic and radiological findings of the medial, lateral and patello-femoral compartment for each patient. The arthroscopic lesions are
graded on a three-point scale and the radiological degree of osteoarthritis is graded on a four-point scale ( Kellgren and Lawrence)
Medial Lateral Patello-femoral
Arthroscopy Rx Arthroscopy Rx Arthroscopy Rx Eusion Meniscal lesion
0 000000 0
0 000000 X
0 00000X X
0 00000X 0
0 000010 0
0 000000 0
0 000000 0
0 000100 X
1 000100 0
0 01010X X
0 010000 0
1 100000 0
0 000110 X
1 00010X X
1 010100 X
0 000100 X
0 000110 0
1 11101X X
0 00110X X
0 000200 0
2 21001X X
0 000220 0
1 010210 0
2 100100 0
2 100010 0
2 00000X 0
3 311330 0
3 100110 X
0 000320 0
1 132320 0
X = eusion or meniscal lesion evident.
joints had a meniscus lesion which was addressed at a slow rate by a pump. The fluid flows by gravity
along the slide and within the non-wetting barrierduring arthroscopy. Two of the healthy joints had a
medial meniscus lesion; six of the grade 1 osteoarthritic painted on the slide. The slide was mounted at a slight
angle above a magnet. Magnetized wear particles sus-joints had a medial, one had a lateral and one had
both types of meniscus lesions. One of the grade 2 pended in the fluid were attracted to the surface of the
slide by the magnetic field. Since the distance of theosteoarthritic joints had a lateral meniscus lesion. For
the grade 3 osteoarthritic joints, there was one joint slide from the magnetic pole was slightly greater at
the entry than at the exit, the strength of the magneticwith a medial meniscus lesion.
Prior to arthroscopy, a sample of synovial fluid was field increased as the particles passed downwards.
Magnetized particles of uniform susceptibility wereaspirated from the lateral suprapatellar border of each
joint. At least 2 ml of fluid were extracted from each deposited on the slide according to their size along the
length of the flow path. Each ferrogram was carbonof eight joints having an eusion. Of these eight
patients, six were suering from meniscal lesions, one coated and examined by SEM (JEOL 6400) in a
secondary electron mode. The number of wear particleshad an anterior cruciate ligament rupture and one
patient had a flare of OA. For the remaining joints, no analysed varied between 15 and 23 for each individual
ferrogram. An accelerating voltage of 5 kV was usedeusion was evident. In these cases, 10 ml of a physio-
logical saline were injected rst into the joint. The knee to avoid alterations of the particle boundary [11]. The
SEM images were digitized in a computer-based system,was flexed and extended 10 times to wash all knee
compartments uniformly, and the washing was aspir- consisting of a SCION video interface, an IBM-compat-
ible PC and the ImageSlave program. The digitizedated with a needle prior to arthroscopy. The synovial
fluid or washing, containing wear particles, was pro- images were transmitted to a Power Macintosh com-
puterforfurtherprocessing.Theimageswerethencessed in order to magnetize the cartilaginous and
osseous particles as described in detail by Kirk and filtered to compensate for electronic noise, transformed
into binary images and analysed by specially developedStachowiak [9]. The ferrographic technique is based
on magnetic precipitation of particles from suspensions. software. The numerical parameters calculated for each
particle were length, area, boundary fractal dimension,A glass slide with a non-wetting barrier painted on one
surface was used to constrain the flow of fluid delivered shape factor, convexity and elongation.
BRITISH JOURNAL OF RHEUMATOLOGY VOL. 37 NO. 9980
$
The boundary fractal dimension. In the present study,
a modified Richardson plot technique was used [10].
The boundary fractal dimension is directly related
to the complexity of the particle boundary, i.e. a
more complex particle boundary shows a higher
fractal dimension.
$
The shape factor is defined as 4parea/perimeter2 and
it also provides a quantitative measure of the particle
boundary irregularity, i.e. a more complex particle
shows a lower shape factor.
$
Convexity is defined as the ratio of convex perimeter
to perimeter, i.e. the convex perimeter equals the
length of a taut string stretched around the particle
boundary. This parameter provides a measure of the
convexity of the particle shape. A more convex
particle shows a higher convexity.
$
Elongation is defined as the ratio of fibre length to
F. 2.Elongated, rod-shaped cartilage particle from a knee joint
width and provides a measure of the stretching of
with osteoarthritis grade 1.
the particle shape. A more stretched-out particle
shape exhibits a higher elongation.
Calculation details of shape factor, elongation and
convexity are given in Russ [13]. The numerical para-
meters calculated from the boundaries of wear particles
used in this study were analysed statistically by the
non-parametric Mann–Whitney–Wilcoxon and mul-
tiple comparison test [14].
RESULTS
Visual analysis
Visual analysis of wear particles conducted in the
study was performed by an investigator unaware of
arthroscopic and radiological findings. Several types
of particles were identified.
Lamellar particles (Fig. 1). Their appearance was
flat with a smooth surface morphology. These particles
F. 3.Chunky wear particle originating from the deep cartilage
were thought to originate from the lamina splendens.
zone.
Rod-shaped particles (Fig. 2). These were elongated
particles which were most abundant in joints with the
early stages of OA, i.e. grade 1.
surface. Their origin was thought to be from the deep
Chunky particles (Fig. 3). These were large and
cartilage zone.
irregularly shaped with a cleavage or spongy type of
Osseous particles (Fig. 4). These originated from the
subchondral bone which implied that the cartilage was
F. 1.Lamellar, leaf-like wear particle from a healthy knee joint. F. 4. Osseous particle from a patient with osteoarthritis grade 3.
KUSTER ET AL.: WEAR PARTICLE SHAPE IN KNEE OA 981
completely worn o in some places. Their morphology elongation factor calculated for wear particles obtained
from grade 1 OA was significantly greater comparedresembled the trabecular structure of bone.
Other particles found on ferrograms could not be to healthy joints. The shape factor calculated for
particles from grade 1 and grade 3 osteoarthritic jointsclassified within the cartilage or the subchondral bone.
They were thought to originate from meniscal lesions was significantly smaller than that for particles
obtained from healthy joints.(Fig. 5) or from the synovial layer. The meniscus
fragments were recognized by their appearance, which In order to examine the dierences between the
dierent grades of OA, a multiple comparison analysiswas consistent with the fibroblastic form described by
Hotchkiss et al. [15]. Since in the present study erbium was performed. The analysis showed that there was a
trend (P < 0.3) for wear particles from grade 3chloride was used to magnetize the cartilage particles
for ferrography, some erbium chloride crystals were osteoarthritic joints to exhibit higher fractal dimensions
and lower convexities than particles obtained fromfound on each ferrogram. They were easily recognized
by their characteristic shape and also by energy dispers- grade 2 or grade 1 osteoarthritic joints. However,
there was no significant dierence between the shapeive X-ray analysis of their chemical composition. The
meniscus fragments and crystal particles were excluded of particles obtained from grade 1 and grade 2
osteoarthritic joints.from further analysis.
It needs to be realized that for some particles the
DISCUSSION
visual dierentiation between lamellar, rod-shaped and
chunky particles might be dicult. This diculty arises Articular cartilage consists mainly of hydrated
proteoglycan gel reinforced by a three-dimensionaldue to the fact that wear particles can exhibit similar
morphology, which makes their dierentiation dicult network of collagen fibrils. The cartilage is uniquely
adapted for a low-friction articulation and load trans-for a human observer. Numerical analysis of wear
particles was, therefore, used to eliminate this diculty. mission across the joint to the underlying bone. The
structure of articular cartilage has been divided into
distinct histological zones with varying cell size, shape,Numerical analysis
In this study, altogether 565 particles were analysed. density and collagen fibre alignment. These zones have
been separated into the superficial or tangential zoneMean values of particle boundary numerical
descriptors calculated from the populations of particles including the lamina splendens, the transitional or
middle zone, the radial or deep zone, the tide markfrom healthy, and grade 1, 2 and 3 osteoarthritic joints
are shown in Table II. It can be seen that numerical and the calcified zone. Based on electron microscopy
studies of bovine cartilage, Jeery et al. [16 ] proposeddescriptors for particles obtained from healthy joints
exhibit a smaller range of values than the same a three-dimensional model of the architecture of artic-
ular cartilage collagen. It was found that in the calcifieddescriptors calculated for particles obtained from
osteoarthritic knee joints. and deep zones, the fibrils are arranged in vertical
bundles with adjacent bundles closely interconnectedStatistical analysis revealed the following significant
dierences (P < 0.01) between the particles obtained by bridging fibrils. In the middle and superficial zones,
the collagen is arranged in a series of closely packedfrom healthy and osteoarthritic knee joints (Table II ).
Wear particles from osteoarthritic knee joints (grades layers or leaves without bridging fibrils. The leaves
themselves are composed of a meshwork of fibrils. The1, 2 and 3) were significantly longer and exhibited a
larger area. The boundary fractal dimension was uppermost layer, the lamina splendens, lacks the fibril-
lar structure of the deeper layers. The wear particlessignificantly higher for particles obtained from
osteoarthritic knee joints (grades 1, 2 and 3). The from a healthy joint with intact lamina splendens must,
therefore, exhibit thin, smooth, leaf-like surfaces with
a simple structure. This has been confirmed by numer-
ical analysis of the shape of the particles obtained from
healthy joints. The area of these particles was signifi-
cantly smaller and the fractal dimension calculated
indicated a less complex boundary compared to
the particles obtained from osteoarthritic joints. In
osteoarthritic lesions, in grade 1 osteoarthritic joints,
the lamina splendens is broken o, revealing the super-
ficial and middle zones where the collagen is arranged
in a series of closely packed layers or leaves without
bridging fibrils. When these leaves break up, fibrillation
is visible during arthroscopy. Thus, wear particles
originating from the superficial and middle zones
exhibit the rode shape as illustrated in Fig. 2. Statistical
analysis of the numerical data obtained from the wear
particles from grade 1 OA joints revealed a significantly
greater elongation factor compared to particles found
F. 5.Particle originating from a meniscal lesion.
in normal joints. In the deep and calcified zones, the
BRITISH JOURNAL OF RHEUMATOLOGY VOL. 37 NO. 9982
TABLE II
Quantitative analysis of wear particles
Healthy OA grade 1 OA grade 2 OA grade 3
Parameter (130 particles) (223 particles) (135 particles) (77 particles)
Area (mm2 ) 542.6 2389.8* 1120.5* 1040.9*
(Range) (60.3–3447.9) (57.0–24 009.8) (63.1–13 895.9) (29.2–12 502.2)
Length (mm) 37.6 66.6* 51.7* 50.7*
(Range) (13.6–97.4) (11.4–268.3) (11.3–228.0) (7.8–179.3)
Convexity 0.77 0.75 0.75 0.73*
(Range) (0.35–0.93) (0.36–0.92) (0.43–0.91) (0.43–0.91)
Elongation 3.53 4.08* 3.99 4.0
(Range) (1.79–12.16) (1.63–14.73) (1.67–15.97) (2.12–14.09)
Shape factor 0.43 0.38* 0.38 0.36*
(Range) (0.06–0.66) (0.04–0.77) (0.06–0.71) (0.08–0.65)
Fractal dimension 1.053 1.068* 1.069* 1.077*
(Range) (1.023–1.1) (1.0181.206) (1.023–1.154) (1.018–1.208)
*Significant dierences compared to healthy joints (P < 0.01).
F. 6.Model of the dierent grades of osteoarthritis. Typical wear particles from the lamina splendens in healthy joints, from the tangential
and middle zone in grade 1, from the deep and calcified zone in grade 2, and from the subchondral bone in grade 3 osteoarthritis are shown.
fibrils are arranged in vertical bundles with adjacent wear particles in the synovial fluid indicates that the
lesion must extend to the subchondral bone. Thesebundles closely interconnected by bridging fibrils.
Thus, wear particles originating from the deeper zones particles show a trabecular structure, which again
exhibits a more complex appearance than the smoothof the cartilage must be torn o a solid network of
collagen. For this reason, they are bigger, chunkier particles from the uppermost layer. It seems that the
histological model of bovine cartilage originally pro-and reveal a more rugged and complex structure, which
was confirmed by the significantly increased fractal posed by Jeery et al. [16 ] provides an excellent guide
in the analysis of wear particles. The data obtained indimension of these particles. The presence of osseous
KUSTER ET AL.: WEAR PARTICLE SHAPE IN KNEE OA 983
this work further support the three-dimensional colla- Despite these problems, SEM examination of wear
particles, combined with the numerical analysis of theirgen model of human cartilage and give an insight into
the wear process occurring in normal and osteoarthritic shape, may provide a good test for the assessment of
cartilage repair after surgical or conservative treatmentknee joints. This model is illustrated schematically
in Fig. 6. of OA.
Ferrography was applied to synovial fluid extracted
A
from human knee joints for the first time by Evans
et al. [7]. It was suggested that ferrography analysis
The authors wish to thank Mrs Maria Kuster for
may even be more sensitive than arthroscopy in the
her help in collecting the SEM images of the particles,
detection of cartilage damage. However, in studies
Dr Ludwig Hauswirth for his artwork in Fig. 6, and
conducted so far, particle analysis was mostly descrip-
Dr Hanna Engeler for her help and suggestions in
tive and during arthroscopy the severity of cartilage
preparing the synovial fluids. Help from the Klinik
damage was not assessed. The present study showed
fu
¨
r Orthopa
¨
dische Chirurgie in St Gallen, Switzerland,
that subtle changes occurring in the shape of the
the Australian Research Council and the Department
cartilage wear particles are reflected in changes occur-
of Mechanical and Materials Engineering, University
ring in numerical descriptors such as elongation factor,
of Western Australia, in this project is greatly
fractal dimension, convexity and shape factor. These
appreciated.
subtle changes were impossible to detect by visual
R
analysis. Furthermore, the numerical description of
wear particles is objective and not subject to a bias of
1. Blackburn WD, Bernreuter WK, Rominger M et al.
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... 7,9 Studies of extracted synovial fluid from healthy and osteoarthritic human knees have observed changes in cartilage particle number and physical descriptors such as size and roughness correlated with grade of disease. 10,11 In lapine, canine, and equine in vivo studies, injection of cartilage particles into the knee joint led to rapid development of synovitis followed by gradual onset of fibrotic synovium thickening and decreased cartilage thickness, similar to traditional animal models of OA such as ACL transection or meniscal release. [12][13][14] Our group has also demonstrated that small CWP (<10 µm diameter) both attach to the cell membrane and are phagocytosed, and stimulate proteinase activity, cellular proliferation, collagen synthesis, and nitric oxide production in bovine FLS monolayer cultures. ...
... Once cartilage begins to degrade, the release of wear particles into the synovial fluid and their attachment to the synovial intima. 8,10,11 Unlike chemical mediators commonly associated with the disease such as pro-inflammatory cytokines, the cellular response to this physical factor of the OA environment has not been widely studied. The present work demonstrates that JOURNAL OF ORTHOPAEDIC RESEARCH ® SEPTEMBER 2019 treatment of FLS monolayers with CWP increased proliferation and release of pro-inflammatory mediators, chemokines, cytokines, and MMPs. ...
... Previous work has characterized CWP from human synovial fluid aspirates that range in size from 5-100 µm diameter, 24 and correlate varying shape and surface properties to OA disease stage. 10,11,25 The present work employed a Coulter Counter to isolate and characterize a well-defined distribution of relatively small particles generated by manual abrasion, that represented the lower end of this physiologic range. Previous work in the juvenile bovine model has shown that this size particle interacts directly with FLS by both attachments to the cell surface and phagocytosis. ...
Article
The synovium plays a key role in the development of osteoarthritis, as evidenced by pathological changes to the tissue observed in both early and late stages of the disease. One such change is the attachment of cartilage wear particles to the synovial intima. While this phenomenon has been well observed clinically, little is known of the biological effects that such particles have on resident cells in the synovium. The present work investigates the hypothesis that cartilage wear particles elicit a pro‐inflammatory response in diseased and healthy human fibroblast‐like synoviocytes, like that induced by key cytokines in osteoarthritis. Fibroblast‐like synoviocytes from 15 osteoarthritic human donors and a subset of 3 non‐osteoarthritic donors were exposed to cartilage wear particles, interleukin‐1α or tumor necrosis factor‐α for 6 days and analyzed for proliferation, matrix production, and release of pro‐inflammatory mediators and degradative enzymes. Wear particles significantly increased proliferation and release of nitric oxide, interleukin‐6 and ‐8, and matrix metalloproteinase‐9, ‐10, and ‐13 in osteoarthritic synoviocytes, mirroring the effects of both cytokines, with similar trends in non‐osteoarthritic cells. These results suggest that cartilage wear particles are a relevant physical factor in the osteoarthritic environment, perpetuating the pro‐inflammatory and pro‐degradative cascade by modulating synoviocyte behavior at early and late stages of the disease. Future work points to therapeutic strategies for slowing disease progression that target cell‐particle interactions. This article is protected by copyright. All rights reserved.
... Another method of determining cartilage wear is to measure the size, shape and/or number of wear particles, which has been performed in vivo and in vitro. Kuster et al. (1998) collected wear particles from the knees of patients by joint lavage. SEM images of the particles were used to determine that wear particles from healthy and osteoarthritic cartilage are different in shape due to the distinct arrangement of collagen fibers in different zones of cartilage. ...
Article
Many material properties of articular cartilage are anisotropic, particularly in the superficial zone where collagen fibers have a preferential direction. However, the anisotropy of cartilage wear had not been previously investigated. The objective of this study was to evaluate the anisotropy of cartilage material behavior in an in vitro wear test. The wear and coefficient of friction of bovine condylar cartilage were measured with loading in directions parallel (longitudinal) and orthogonal (transverse) to the collagen fiber orientation at the articular surface. An accelerated cartilage wear test was performed against a T316 stainless-steel plate in a solution of phosphate buffered saline with protease inhibitors. A constant load of 160 N was maintained for 14000 cycles of reciprocal sliding motion at 4 mm/s velocity and a travel distance of 18 mm in each direction. The contact pressure during the wear test was approximately 2 MPa, which is in the range of that reported in the human knee and hip joint. Wear was measured by biochemically quantifying the glycosaminoglycans (GAGs) and collagen that was released from the tissue during the wear test. Collagen damage was evaluated with collagen hybridizing peptide (CHP), while visualization of the tissue composition after the wear test was provided with histologic analysis. Results demonstrated that wear in the transverse direction released about twice as many GAGs than in the longitudinal direction, but that no significant differences were seen in the amount of collagen released from the specimens. Specimens worn in the transverse direction had a higher intensity of CHP stain than those worn in the longitudinal direction, suggesting more collagen damage from wear in the transverse direction. No anisotropy in friction was detected at any point in the wear test. Histologic and CHP images demonstrate that the GAG loss and collagen damage extended through much of the depth of the cartilage tissue, particularly for wear in the transverse direction. These results highlight distinct differences between cartilage wear and the wear of traditional engineering materials, and suggest that further study on cartilage wear is warranted. A potential clinical implication of these results is that orienting osteochondral grafts such that the direction of wear is aligned with the primary fiber direction at the articular surface may optimize the life of the graft.
... The success of analytical ferrography in condition monitoring of engineering systems triggered few feasibility studies in the fields of life sciences and medicine, mainly in hip and knee joint applications, already in the 1980s [81]. These included erythrocyte and white blood cell separation [82][83][84][85], bacterial tracking [84][85][86] and monitoring the wear of either natural diarthrodial joints [81,[87][88][89][90][91][92][93][94][95][96] or artificial joints [87,88,91,97]. In those studies, Er 3+ was the magnetizing agent. ...
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Metallic biomaterials are used in medical devices in humans more than any other family of materials. The corrosion resistance of an implant material affects its functionality and durability and is a prime factor governing biocompatibility. The fundamental paradigm of metallic biomaterials, except biodegradable metals, has been “the more corrosion resistant, the more biocompatible.” The body environment is harsh and raises several challenges with respect to corrosion control. In this invited review paper, the body environment is analysed in detail and the possible effects of the corrosion of different biomaterials on biocompatibility are discussed. Then, the kinetics of corrosion, passivity, its breakdown and regeneration in vivo are conferred. Next, the mostly used metallic biomaterials and their corrosion performance are reviewed. These biomaterials include stainless steels, cobalt-chromium alloys, titanium and its alloys, Nitinol shape memory alloy, dental amalgams, gold, metallic glasses and biodegradable metals. Then, the principles of implant failure, retrieval and failure analysis are highlighted, followed by description of the most common corrosion processes in vivo. Finally, approaches to control the corrosion of metallic biomaterials are highlighted.
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Volume 18 addresses friction and wear from a systems perspective, while providing a detailed understanding of why it occurs and how to control it. It explains the basic theory of friction and wear, and offers valuable insight on the forces, mechanisms, and interactions that are involved. It examines common wear scenarios, including wear by particles or fluids, rolling-contact wear, sliding wear, impact wear, and both chemical and environmentally assisted wear. It also covers operational wear, addressing several cases, including tool and die wear, bearing wear, engine wear, turbine wear, pump wear, and seal wear. In addition, the volume provides information on lubricants and lubrication, coatings, surface treatments and modifications, and the tribology of irons and steels, cobalt-base alloys, titanium, aluminum alloys and composites, cemented carbides, ceramics, polymers, and polymer composites. It also introduces the topic of condition monitoring, addressing wear particle analysis, vibroacoustic monitoring, and motor current signature analysis. For information on the print version of Volume 18, ISBN 978-1-62708-141-2, follow this link.
Article
Cartilage wear particles are released into the synovial fluid by mechanical and chemical degradation of the articular surfaces during osteoarthritis and attach to the synovial membrane. Accumulation of wear particles could alter key tissue-level mechanical properties of the synovium, hindering its characteristically low-friction interactions with underlying articular surfaces in the synovial joint. The present study employs a custom loading device to further the characterization of native synovium friction properties, while investigating the hypothesis that attachment of cartilage wear particles increases friction coefficient. Juvenile bovine synovium demonstrated characteristically low friction coefficients in sliding contact with glass, in agreement with historical measurements. Friction coefficient increased with higher normal load in saline, while lubrication with native synovial fluid maintained low friction coefficients at higher loads. Cartilage wear particles generated from juvenile bovine cartilage attached directly to synovium explants in static culture, with incorporation onto the tissue denoted by cell migration onto the particle surface. In dilute synovial fluid mimicking the decreased lubricating properties during osteoarthritis, wear particle attachment significantly increased friction coefficient against glass, and native cartilage and synovium. In addition to providing a novel characterization of synovial joint tribology this work highlights a potential mechanism for cartilage wear particles to perpetuate the degradative environment of osteoarthritis by modulating tissue-level properties of the synovium that could impact macroscopic wear as well as mechanical stimuli transmitted to resident cells.
Article
The surface topographies of wear debris found in human knees were collected at the nano-scale in their hydrated status using atomic force microscopy (AFM) and characterised quantitatively. As a result, the spatial (Scl37) and functional (Spk) parameters were identified as potential early OA indicators to separate wear debris generated in normal knees from those in mild OA condition. The selected key hybrid parameter, Sdq, revealed significance in discriminating wear particles in the severe OA from those in the other conditions (i.e., normal and mild OA). The other selected parameters including the commonly used amplitude parameter Sa can help distinguish wear debris in normal and severe OA conditions. The 3D characterisations of wear debris provide a new approach for OA assessment.
Article
Objective: Osteoarthritis is a progressive joint disease characterized by cartilage degradation and synovial inflammation. Presence of cartilage fragments in the joint due to degradation of cartilage is thought to be associated with local inflammatory response and progressive osteoarthritic process. Understanding the mechanism by which cartilage fragments elicit this destructive process should aid in designing novel therapeutic approaches. Therefore, objective of current study is to establish an in vitro model to examine the cross-talk between chondrocytes and cartilage fragments-stimulated macrophages. Design: Cartilage fragments were prepared from femoral head cartilages of mice and analyzed using a scanning electron microscope and particle size analyzer. Bone marrow-derived macrophages were co-cultured with cartilage fragments and chondrocytes using transwell co-culture system. Macrophage inflammatory mediators in supernatant of cultures were determined by ELISA and gene expression of macrophages and chondrocyte were quantified by qRT-PCR. Results: Shapes of cartilage fragments were irregular with sizes ranged between 0.54 and 55 μm. Macrophages cultured with cartilage fragments released significantly higher concentrations of TNF-α, IL-6, and NO than those of mock and control. Consistently, gene expressions of TNF-α, IL-6, and MMP-9 were significantly increased in stimulated macrophages. The elevation in production of pro-inflammatory molecules in stimulated macrophages cultures were coincident with an increase in gene expression of chondrocyte MMP-13, iNOS, and IL-6. Conclusion: We developed an in vitro co-culture model to study the impact of stimulation of macrophage by cartilage fragments on the expression of chondrocyte carbolic factors. Our results revealed that cartilage fragments triggered macrophages inflammatory response that enhanced the production of chondrocyte catabolic factors.
Article
Osteoarthritis is a degenerative joint disease that affects millions of people worldwide. The aims of this study were (1) to quantitatively characterise the boundary and surface features of wear particles present in the synovial fluid of patients, (2) to select key numerical parameters that describe distinctive particle features and enable osteoarthritis assessment and (3) to develop a model to assess osteoarthritis conditions using comprehensive wear debris information. Discriminant analysis was used to statistically group particles based on differences in their numerical parameters. The analysis methods agreed with the clinical osteoarthritis grades in 63%, 50% and 61% of particles for no osteoarthritis, mild osteoarthritis and severe osteoarthritis, respectively. This study has revealed particle features specific to different osteoarthritis grades and provided further understanding of the cartilage degradation process through wear particle analysis - the technique that has the potential to be developed as an objective and minimally invasive method for osteoarthritis diagnosis.
Article
Objective: Arthroscopy with lavage and synovectomy can remove tissue debris from the joint space and the synovial lining to provide pain relief to patients with osteoarthritis (OA). Here, we developed an in vitro model to study the interaction of cartilage wear particles with fibroblast-like synoviocytes (FLS) to better understand the interplay of cartilage particulates with cytokines on cells of the synovium. Method: In this study sub-10?m cartilage particles or 1?m latex particles were co-cultured with FLS ? 10 ng/mL interleukin-1? (IL-1 ?) or tumor necrosis factor- ? (TNF-?). Samples were analyzed for DNA, glycosaminoglycan (GAG), and collagen and media samples were analyzed for media GAG, nitric oxide (NO) and prostaglandin-E2 (PGE2). The nature of the physical interaction between the particles and FLS was determined by microscopy. Results: Both latex and cartilage particles could be phagocytosed by FLS. Cartilage particles were internalized and attached to the surface of both dense monolayers and individual cells. Co-culture of FLS with cartilage particulates resulted in a significant increase in cell sheet DNA and collagen content as well as NO and PGE2 synthesis compared to control and latex treated groups. Conclusion: The proliferative response of FLS to cartilage wear particles resulted in an overall increase in ECM content, analogous to the thickening of the synovial lining observed in OA patients. Understanding how cartilage particles interface with the synovium may provide insight into how this interaction contributes to OA progression and may guide the role of lavage and synovectomy for degenerative disease.
Chapter
Synovial joints are created to enable movement among articulating bones. During movement, mechanical loading is transmitted across the joint, inducing mechanical stresses among all joint components such as articular cartilage, bone, meniscus, and ligaments. Articular cartilage plays critical roles in enabling motion in the synovial joint. Hyaline is the most common articular cartilage, whereas fibrocartilage is present in the semilunar meniscus of the knee, the temporomandibular joint of the jaw, and the intervertebral disk. The natural design of hyaline cartilage and fibrocartilage provides extraordinarily low friction and little wear under normal healthy conditions. However, molecular and ultrastructural structures of articular cartilage and meniscus can be destructed in diseases such as osteoarthritis and rheumatoid arthritis. For the purpose of this review, articular cartilage is discussed to represent hyaline cartilage, whereas knee meniscus is discussed as a representative of hyaline cartilage.
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Although conventional radiography is the method most frequently used for monitoring progression of osteoarthritis, it may not show osteoarthritic changes of the knee until late in the disease, and it may show involvement of only one or two compartments in patients who have tricompartmental disease. We compared radiography, CT, and MR imaging for assessing the extent and severity of osteoarthritis of the knee in 20 patients. Radiography included posteroanterior weight-bearing, true lateral, and sunrise patellar projections. Axial CT scans were reformatted in sagittal and coronal planes. MR imaging consisted of spin-echo (600-800/20; 2000/60, 120 [TR/TE]), and gradient-echo (600/30, theta = 30 degrees) sequences. The severity of osteoarthritic changes was graded from 0 to 3. MR frequently showed tricompartmental cartilage loss when radiography and CT showed only bicompartmental involvement in the medial and patellofemoral compartments. In the lateral compartment, MR showed a higher prevalence of cartilage loss (60%) than radiography (35%) and CT (25%) did. In the medial compartment, CT and MR showed osteophytes in 100% of the knees, whereas radiography showed osteophytes in only 60%. Notably, radiography often failed to show osteophytes in the posterior medial femoral condyle. On MR images, meniscal degeneration or tears were found in all 20 knees studied. Partial and complete tears of the anterior cruciate ligament were found in three and seven patients, respectively. MR is more sensitive than radiography and CT for assessing the extent and severity of osteoarthritic changes and frequently shows tricompartmental disease in patients in whom radiography and CT show only bicompartmental involvement. MR imaging is unique for evaluating meniscal and ligamentous disease related to osteoarthritis.
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The three-dimensional architecture of bovine articular cartilage collagen and its relationship to split lines has been studied with scanning electron microscopy. In the middle and superficial zones, collagen was organised in a layered or leaf-like manner. The orientation was vertical in the intermediate zone, curving to become horizontal and parallel to the articular surface in the superficial zone. Each leaf consisted of a fine network of collagen fibrils. Adjacent leaves merged or were closely linked by bridging fibrils and were arranged according to the split-line pattern. The surface layer (lamina splendens) was morphologically distinct. Although ordered, the overall collagen structure was different in each plane (anisotropic) a property described in previous morphological and biophysical studies. As all components of the articular cartilage matrix interact closely, the three-dimensional organisation of collagen is important when considering cartilage function and the processes of cartilage growth, injury and repair.
Is the fractal dimension, of a particle's projected boundary less than the fractal dimension of the sectioned boundary of the same particle? This question has been posed by several researchers, and Russ (1991) argues that it is less, using a computer simulation to validate this opinion. In this paper, a series of real metallic particles are examined as projections and sections, using techniques outlined in a previous paper by Hamblin and Stachowiak (1993). Isotropic and anisotropic particles are examined, and in almost every case a substantial decrease in dimension was found when viewed as a projection. The appearance of bimodal Richardson plots is questioned with respect to assigning 'textural' and 'structural' fractal dimensions.
Article
For the purposes of classification, it should be specified whether osteoarthritis (OA) of the knee is of unknown origin (idiopathic, primary) or is related to a known medical condition or event (secondary). Clinical criteria for the classification of idiopathic OA of the knee were developed through a multicenter study group. Comparison diagnoses included rheumatoid arthritis and other painful conditions of the knee, exclusive of referred or paraarticular pain. Variables from the medical history, physical examination, laboratory tests, and radiographs were used to develop sets of criteria that serve different investigative purposes. In contrast to prior criteria, these proposed criteria utilize classification trees, or algorithms.
Article
We examined the relationship between articular cartilage degeneration, as visualized arthroscopically, and joint space narrowing (JSN) in standing anteroposterior knee radiographs of 161 patients with chronic knee pain. The majority of these patients had radiographic findings of mild osteoarthritis. Twenty-five (33%) of the 76 patients in the series whose radiographs showed tibiofemoral JSN had grossly normal articular cartilage in both tibiofemoral compartments at arthroscopy (false-positive). The specificity of medial JSN for the presence of medial compartment articular cartilage degeneration was 0.61, i.e., only 61% of patients with normal (grade 0) medial compartment cartilage had a normal medial joint space. Of 22 patients with greater than 50% medial JSN, 9 (41%) had normal articular cartilage in the medial compartment at arthroscopy. Of 6 patients with greater than 50% lateral JSN, 3 (50%) had normal lateral compartment articular cartilage at arthroscopy. Among 36 patients with greater than 25% JSN who had neither medial nor lateral compartment articular cartilage degeneration, JSN was associated with articular cartilage degeneration in the patellofemoral compartment in 8 (22%), with meniscus degeneration in 18 (50%), and with both in 8 (22%). Thus, in these patients with chronic knee pain, radiographic evidence of JSN in the tibiofemoral compartment did not permit confident prediction of the status of the articular cartilage.
Article
The technique of ferrography has been applied to the analysis of wear particles in human synovial fluid aspirates. A number of discrete, identifiable classes of wear particles were found, including particles indicative of cutting wear and rubbing wear. The spectrum of particles varied among different groups of patients, suggesting an eventual diagnostic use for this method.
Article
Cytologic analysis of filtered synovial lavage was compared with the independent arthroscopic findings in 70 patients with knee pain secondary to injury. Correlation existed between the arthroscopic evaluation of the articular surfaces and the presence of cartilaginous fragments and their microscopic features. Study of the filtered lavage was carried out without knowledge of the patient's clinical status or arthroscopic findings. Patients with unblemished articular surfaces and normal menisci demonstrated essentially no fragments in the synovial lavage. Minimal fibrillation of the articular surface with normal menisci was associated with few cartilage fragments per sample. Patients with moderate to severe fibrillation of the articular surface requiring a surface altering procedure, demonstrated significantly more fragments per sample. Chondrocyte nuclei were visible in these fragments, often arranged in multicellular clusters. Isolated lesions of the meniscus were associated with cartilage fragments that did not contain chondrocyte nuclei. Microscopic analysis of synovial lavage may serve as a useful diagnostic adjunct in the evaluation of the painful knee and the study of the pathogenic role of cartilage fragments is osteoarthrosis.