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PubMed2003

Modelling cartilage mechanobiology.

The growth, maintenance and ossification of cartilage are fundamental to skeletal development and are regulated throughout life by the mechanical cues that are imposed by physical activities. Finite element computer analyses have been used to study the role of local tissue mechanics on endochondral ossification patterns, skeletal morphology and articular cartilage thickness distributions. Using single-phase continuum material representations of cartilage, the results have indicated that local intermittent hydrostatic pressure promotes cartilage maintenance. Cyclic tensile strains (or shear), however, promote cartilage growth and ossification. Because single-phase material models cannot capture fluid exudation in articular cartilage, poroelastic (or biphasic) solid/fluid models are often implemented to study joint mechanics. In the middle and deep layers of articular cartilage where poroelastic analyses predict little fluid exudation, the cartilage phenotype is maintained by cyclic fluid pressure (consistent with the single-phase theory). In superficial articular layers the chondrocytes are exposed to tangential tensile strain in addition to the high fluid pressure. Furthermore, there is fluid exudation and matrix consolidation, leading to cell 'flattening'. As a result, the superficial layer assumes an altered, more fibrous phenotype. These computer model predictions of cartilage mechanobiology are consistent with results of in vitro cell and tissue and molecular biology experiments.

Animals↗
PubMed2006

Micro-anatomical response of cartilage-on-bone to compression: mechanisms of deformation within and beyond the directly loaded matrix.

The biomechanical function of articular cartilage relies crucially on its integration with both the subchondral bone and the wider continuum of cartilage beyond the directly loaded contact region. This study was aimed at visualizing, at the microanatomical level, the deformation response of cartilage including that of the non-directly loaded continuum. Cartilage-on-bone samples from bovine patellae were loaded in static compression until a near-equilibrium deformation was achieved, and then chemically fixed in this deformed state. Full-depth cartilage-bone sections, incorporating the indentation profile and beyond, were studied in their fully hydrated state using differential interference contrast microscopy. Morphometric measurements of the indented profile were used in combination with a force analysis of the tangential layer to investigate the extent to which the applied force is attenuated in moving away from the directly loaded region. This study provides microscopic evidence of a structure-related response in the transitional zone of the cartilage matrix. It is manifested as an intense chevron-type shear discontinuity arising from the constraints provided by both the strain-limiting articular surface and the osteochondral attachment. The discontinuity persists well into the non-directly loaded continuum of cartilage and is proposed as a force attenuation mechanism. The structural and biomechanical analyses presented in this study emphasize the important role of the complex microanatomy of cartilage, highlighting the interconnectivity and optimal recruitment of the load-bearing elements throughout the zonally differentiated cartilage depth.

Animals↗
PubMedDate not supplied

Effect of dimethylsulfoxide on articular cartilage proteoglycan synthesis and degradation, chondrocyte viability, and matrix water content.

OBJECTIVE: To determine the effects of dimethylsulfoxide (DMSO) exposure on cartilage proteoglycan (PG) synthesis, PG degradation, chondrocyte viability, and matrix water content. STUDY DESIGN: Using a cartilage explant culture system, PG synthesis, PG degradation, matrix water content, and chondrocyte viability were determined for cartilage exposed to DMSO daily for selected periods of time. ANIMALS OR SAMPLE POPULATION: Juvenile bovine (calf) carpometacarpal joint cartilage explants. METHODS: PG synthesis: Explants (n = 30/group) were separated into 10 groups based on the time of daily exposure to 10% DMSO. Exposure time was repeated daily for 3 days. The control group was incubated in basal medium alone for 3 days, with daily medium changes. Once all DMSO exposure times were complete for the third day, PG synthesis was determined by analysis of incorporation of radiolabelled sulfate. Cell viability: Explants (n = 3/group) were subjected to an identical DMSO exposure protocol, and examined histologically. The percentage of viable cells/high power field (hpf) was calculated for each group. PG degradation: Explants (n = 21/group) were preincubated with radiolabelled sulfate, then subjected to a similar DMSO exposure protocol. The medium was collected from all explants daily and assayed for PG content. After 3 days, the explants were digested and total labelled PG content determined. Percent of total explant labelled PG content released into the medium daily was determined for each group. Water content: Explants (n = 21/group) were separated into three treatment groups, one of which had no treatments performed, whereas the other two groups were incubated in basal medium for 72 hours, one with, and one without, 10% DMSO. Wet and dry weights were determined, and percent water calculated, for all three groups. Separate 1-way ANOVA were performed, with appropriate post hoc tests (P < .05). RESULTS: PG synthesis was significantly lower than control for all time periods of DMSO exposure except for 1 and 3 hours, and decreased in a time-dependent manner after the 1-hour exposure time. The mean percentage of viable cells/hpf was significantly lower than control for the 1-, 3-, 9-, 12-, and 24-hour treatment groups. There was no significant difference in PG degradation for any group compared with control for the first 2 days of incubation. All groups except the 24-hour group had a significantly higher degradation compared with control for the third day of incubation. Cartilage exposed to DMSO for 72 hours had a significantly lower water content, and cartilage incubated in basal medium alone for 72 hours had a significantly higher water content than cartilage that received no DMSO and no incubation. CONCLUSIONS: DMSO, in relatively low concentration, is detrimental to articular cartilage PG synthesis in a time-dependent manner. Dehydration of the cartilage and chondrocyte death also occur with increasing time of DMSO exposure. Significant PG degradation occurs on the third day of culture with daily DMSO exposure. CLINICAL RELEVANCE: As a joint lavage solution, DMSO has potentially deleterious effects on the metabolism of chondrocytes.

Administration, Topical↗
PubMed2002

Effect of glucosamine on interleukin-1-conditioned articular cartilage.

Glucosamine inhibits recombinant human interleukin-1 stimulated cartilage degradation in equine cartilage explants. Recently, recombinant equine interleukin-1 has been cloned and purified. Therefore, the objective of this study was to characterise the effects of glucosamine on indices of cartilage degradation in recombinant equine IL-1beta-stimulated equine articular cartilage explants. Cartilage discs were harvested from the weight-bearing region of the articular surface of the antebrachiocarpal and middle carpal joints of horses (age 2-8 years) and cultured under standard conditions. Explants were exposed to recombinant equine interleukin-1beta (reIL-1beta) on Days 1-4 in the presence or absence of glucosamine (0.25, 2.5 or 25 mg/ml), with appropriate controls. Nitric oxide, prostaglandin E2, sulphated proteoglycan, stromelysin and gelatinase/collagenase activity released into conditioned media and total tissue proteoglycan content were measured as indicators of cartilage catabolism. Glucosamine inhibited cartilage catabolic responses in a dose dependent manner that was statistically significant at a dose of 0.25 mg/ml for stromelysin activity and 2.5 mg/ml for collagenase/gelatinase activity. At 25 mg/ml glucosamine also prevented IL-1beta-induced increases in nitric oxide production, prostaglandin E2 and proteoglycan release to media. Glucosamine prevents equine articular cartilage degradation experimentally induced by reIL-1beta in vitro. These data provide further support for the use of glucosamine in treatment or prevention of cartilage loss in athletic horses.

Animals↗
PubMed2006

Dynamic response of immature bovine articular cartilage in tension and compression, and nonlinear viscoelastic modeling of the tensile response.

Very limited information is currently available on the constitutive modeling of the tensile response of articular cartilage and its dynamic modulus at various loading frequencies. The objectives of this study were to (1) formulate and experimentally validate a constitutive model for the intrinsic viscoelasticity of cartilage in tension, (2) confirm the hypothesis that energy dissipation in tension is less than in compression at various loading frequencies, and (3) test the hypothesis that the dynamic modulus of cartilage in unconfined compression is dependent upon the dynamic tensile modulus. Experiment 1: Immature bovine articular cartilage samples were tested in tensile stress relaxation and cyclical loading. A proposed reduced relaxation function was fitted to the stress-relaxation response and the resulting material coefficients were used to predict the response to cyclical loading. Adjoining tissue samples were tested in unconfined compression stress relaxation and cyclical loading. Experiment 2: Tensile stress relaxation experiments were performed at varying strains to explore the strain-dependence of the viscoelastic response. The proposed relaxation function successfully fit the experimental tensile stress-relaxation response, with R2 = 0.970+/-0.019 at 1% strain and R2 = 0.992+/-0.007 at 2% strain. The predicted cyclical response agreed well with experimental measurements, particularly for the dynamic modulus at various frequencies. The relaxation function, measured from 2% to 10% strain, was found to be strain dependent, indicating that cartilage is nonlinearly viscoelastic in tension. Under dynamic loading, the tensile modulus at 10 Hz was approximately 2.3 times the value of the equilibrium modulus. In contrast, the dynamic stiffening ratio in unconfined compression was approximately 24. The energy dissipation in tension was found to be significantly smaller than in compression (dynamic phase angle of 16.7+/-7.4 deg versus 53.5+/-12.8 deg at 10(-3) Hz). A very strong linear correlation was observed between the dynamic tensile and dynamic compressive moduli at various frequencies (R2 = 0.908+/-0.100). The tensile response of cartilage is nonlinearly viscoelastic, with the relaxation response varying with strain. A proposed constitutive relation for the tensile response was successfully validated. The frequency response of the tensile modulus of cartilage was reported for the first time. Results emphasize that fluid-flow dependent viscoelasticity dominates the compressive response of cartilage, whereas intrinsic solid matrix viscoelasticity dominates the tensile response. Yet the dynamic compressive modulus of cartilage is critically dependent upon elevated values of the dynamic tensile modulus.

Animals↗
PubMed2004

Correlation and sex differences between ankle and knee cartilage morphology determined by quantitative magnetic resonance imaging.

OBJECTIVE: To study the correlation between ankle and knee cartilage morphology to test the hypothesis that knee joint cartilage loss in gonarthritis can be estimated retrospectively using quantitative MRI analysis of the knee and ankle and established regression equations; and to test the hypothesis that sex differences in joint surface area are larger in the knee than the ankle, which may explain the greater incidence of knee osteoarthritis in elderly women than in elderly men. METHODS: Sagittal MR images (3D FLASH WE) of the knee and hind foot were acquired in 29 healthy subjects (14 women, 15 men; mean (SD) age, 25 (3) years), with no signs joint disease. Cartilage volume, thickness, and joint surface area were determined in the knee, ankle, and subtalar joint. RESULTS: Knee cartilage volumes and joint surface areas showed only moderate correlations with those of the ankle and subtalar joint (r = 0.33 to 0.81). The correlations of cartilage thickness between the two joints were weaker still (r = -0.05 to 0.53). Sex differences in cartilage morphology at the knee and the ankle were similar, with surface areas being -17.5% to -23.5% lower in women than in men. CONCLUSIONS: Only moderate correlations in cartilage morphology of healthy subjects were found between knee and ankle. It is therefore impractical to estimate knee joint cartilage loss a posteriori in cross sectional studies by measuring the hind foot and then applying a scaling factor. Sex differences in cartilage morphology do not explain differences in osteoarthritis incidence between men and women in the knee and ankle.

Adult↗
PubMed2005

Factors influencing longitudinal change in knee cartilage volume measured from magnetic resonance imaging in healthy men.

OBJECTIVE: To determine whether the amount of joint cartilage in healthy, middle aged men is stable or changes over time, and what factors may influence this. METHODS: In a cohort study, 28 healthy men (70% of the original cohort; mean (SD) age, 51.9 (12.8) years) had baseline knee magnetic resonance imaging (MRI) of their dominant knee and repeat MRI of the same knee approximately 2.0 years later. Knee cartilage volume was measured at baseline and follow up. Risk factors assessed at baseline, including sex hormones and metabolic bone markers, were tested for their association with change in knee cartilage volume over time. RESULTS: Mean (SD) reduction in tibial cartilage volume per year was 162 (93) microl. This represented a 2.8% reduction in total tibial articular cartilage per year (95% confidence interval, 0.2% to 5.5%). Tibial cartilage loss was associated with serum free testosterone level, independently of age, body mass index, baseline tibial cartilage volume tibial plateau area, and total bone mineral content. Overall, testosterone accounted for 14.5% (partial r2) of the variation in change in tibial cartilage volume. There was a trend towards a positive association between tibial cartilage loss and urinary N-telopeptide cross-links of type I collagen (Ntx) (p = 0.057). CONCLUSIONS: Further studies will be required to determine whether hormonal manipulation or treatment with antiresorptive drugs will reduce the risk of knee osteoarthritis in men in later life.

Adult↗
PubMed1979

Chemical composition of human femoral and head cartilage: influence of topographical position and fibrillation.

Topographical variations in the composition of cartilage have been described in post-mortem femoral head cartilage. Weight bearing cartilage of the superior region was considerably thicker and had a higher glycosaminoglycan content and lower water and collagen content than cartilage at the periphery and below the fovea. These topographical variations in composition may result both from variations in thickness of the cartilage and from regional areas of degeneration. The composition of cartilage at different depths and with different surface characteristics from different areas of the femoral head was measured. Fibrillated cartilage both from the inferior and superior perifoveal areas had a reduced glycosaminoglycan content and higher water content than intact post-mortem specimens. Cartilage adjacent to fibrillated areas from the superior region did not differ in composition from intact areas of cartilage from the zenith of the femoral head.

Cartilage, Articular↗
PubMed1981

Metabolism of human femoral head cartilage in osteoarthrosis and subcapital fracture.

The cell density and incorporation of 35SO4 and 3H-glycine into human articular cartilage from 8 osteoarthrotic and 7 normal (subcapital fracture) femoral heads were studied. It was found that osteoarthrotic cartilage incorporates on a per cell basis about twice as much 35SO4 and 2--5 times as much 3H-glycine as normal cartilage. There was no relationship between the intensity of incorporation and either the location of the cartilage (weight-bearing versus non weight-bearing areas) in normal cartilage or the degree of damage (normal-like, fibrillated, and ulcerated) in osteoarthrotic articular cartilage. In the latter tissue the increased synthetic capacity of the cells seems to be a diffuse rather than a localised process, for it was also found in cartilage from peripheral osteophytes. Histo-autoradiographic studies showed that the osteoarthrotic chondrocytes are metabolically hyperactive all over the femoral head, including wedge-shaped margins of the zone of exposed bone. These results support the hypothesis that much of the articular cartilage from osteoarthrotic femoral heads is of an immature chondroblastic type. It is suggested that de-novo synthesis of articular cartilage occurs during the process of regional remodelling of the femoral head, which would account for the observed hyperactivity.

Aged↗
PubMed1994

Humoral immune response against minor collagens type IX and XI in patients with cartilage graft resorption after reconstructive surgery.

OBJECTIVES: The humoral immune response against a broad spectrum of cartilage antigens (cellular and matrix antigens) was studied in a group of patients who showed resorption and/or rejection of transplanted cartilage in nasal surgery. METHODS: Sera were obtained from patients with successful and unsuccessful cartilage grafting in the nose, from age and sex-matched healthy donors and from patients with rheumatoid arthritis. Antibodies to cartilage components were analysed by the following methods: (1) indirect immunofluorescence on cartilage sections, (2) ELISA using cultured human chondrocytes, isolated chondrocyte membranes and purified collagens type I, II, III, VI, IX and XI, and (3) immunoblotting with purified collagens and chondrocyte cell membranes. RESULTS: In the cartilage grafting group showing resorption problems, levels of anti-collagen antibodies were significantly higher against native collagen types IX (p < 0.002) and XI (p < 0.002) compared with the non-resorption group and the normal donors. Both transplantation groups revealed elevated reactivities against isolated chondrocytes in the ELISA. In contrast, no reactivity was detectable against collagens type II, III, and VI and chondrocyte cell membranes by both ELISA and immunoblotting. CONCLUSIONS: These data demonstrate for the first time the existence of a humoral immune response, primarily directed against the so called 'minor cartilage collagens', in patients showing cartilage resorption. Autoreactivities to collagen which are typical of inflammatory rheumatic diseases may also play an important role in the repeated failure of cartilage grafting.

Adult↗
PubMed1996

Influence of interleukin 1 beta on tenascin distribution in human normal and osteoarthritic cartilage: a quantitative immunohistochemical study.

OBJECTIVE: To determine the influence of IL-1 beta on the presence and the distribution of tenascin in matrix of human normal and osteoarthritic cartilage explants. METHODS: Cartilage was grown in organotypic culture with or without IL-1 beta (10 ng ml1). Tenascin antigen was detected on cryopreserved cartilage sections by immunohistochemical techniques with a monoclonal antibody directed against all tenascin isoforms (BC-4), and then quantified by video imaging densitometry. RESULTS: Tenascin was present in normal cartilage explants and increased in osteoarthritic cartilage explants. Treatment of normal and osteoarthritic cartilage explants with IL-1 beta (10 ng ml-1) induced an increase in tenascin content, which was particularly high in normal cartilage and predominated in the superficial layers of damaged cartilage. There was no obvious correlation between proteoglycan loss and presence of tenascin. CONCLUSIONS: In human normal and osteoarthritic cartilage explants, the presence and the distribution of tenascin are influenced by IL-1 beta.

Aged↗
PubMed2001

Vascular endothelial growth factor in articular cartilage of healthy and osteoarthritic human knee joints.

OBJECTIVE: To determine the levels of vascular endothelial growth factor (VEGF) mRNA and protein expression in normal and osteoarthritic (OA) human articular cartilage, and whether VEGF expression alters during the progression of OA. METHODS: Sections from normal and OA human knee cartilage were immunotained with a polyclonal antibody recognising VEGF. In addition, total RNA was isolated from normal and osteoarthritic human knee cartilage and analysed by reverse transcriptase-polymerase chain reaction (RT-PCR) for VEGF mRNA expression. RESULTS: VEGF was found to be present in normal and OA human knee cartilage in all cartilage layers. A significant increase of VEGF immunopositive chondrocytes to up to approximately 82% was detected in severe OA cartilage compared with normal articular cartilage (approximately 56% of immunopositive chondrocytes). RT-PCR analysis showed the expression of VEGF also on the mRNA level. CONCLUSIONS: VEGF is expressed by articular chondrocytes in normal and OA human knee cartilage. The percentage of VEGF immunopositive chondrocytes significantly increases in late stages of the disease. The VEGF transcript levels encoding all four isoforms shows a big variability in samples from different donors, suggesting a distinct regulation of the expression of the four VEGF isoforms in normal and OA cartilage.

Cartilage, Articular↗
PubMed2002

Interleukin 17 synergises with tumour necrosis factor alpha to induce cartilage destruction in vitro.

BACKGROUND: Interleukin 17 (IL17) is produced by activated T cells and has been implicated in the development of bone lesions and cartilage degradation in rheumatoid arthritis (RA). OBJECTIVE: To determine whether IL17, alone or together with tumour necrosis factor alpha (TNFalpha), induces cartilage destruction in vitro. METHODS: Fetal mouse metatarsals stripped of endogenous osteoclast precursors were used to study the effect of IL17 on cartilage degradation independently of osteoclastic resorption. Cartilage destruction was analysed histologically by Alcian blue staining. RESULTS: IL17 alone, up to 100 ng/ml, had no effect on the cartilage of fetal mouse metatarsals. IL17 (>/=0.1 ng/ml), however, induced severe cartilage degradation when given together with TNFalpha (>/=1 ng/ml). The cytokine combination decreased Alcian blue staining, a marker of proteoglycans, throughout the metatarsals and induced loss of the proliferating and early hypertrophic chondrocyte zones. TNFalpha alone also decreased Alcian blue staining, but not as dramatically as the cytokine combination. In addition, it did not induce loss of chondrocyte zones. Treatment with inhibitors of matrix metalloproteinase (MMP) activity and nitric oxide synthesis showed that MMP activity played a part in cartilage degradation, whereas nitric oxide production did not. CONCLUSIONS: IL17, together with TNFalpha, induced cartilage degradation in fetal mouse metatarsals in vitro. IL17 may, therefore, participate in the development of cartilage destruction associated with RA by enhancing the effects of TNFalpha and may provide a potential therapeutic target.

Animals↗
PubMed2002

Mechano-electrochemical properties of articular cartilage: their inhomogeneities and anisotropies.

In this chapter, the recent advances in cartilage biomechanics and electromechanics are reviewed and summarized. Our emphasis is on the new experimental techniques in cartilage mechanical testing, new experimental and theoretical findings in cartilage biomechanics and electromechanics, and emerging theories and computational modeling of articular cartilage. The charged nature and depth-dependent inhomogeneity in mechano-electrochemical properties of articular cartilage are examined, and their importance in the normal and/or pathological structure-function relationships with cartilage is discussed, along with their pathophysiological implications. Developments in theoretical and computational models of articular cartilage are summarized, and their application in cartilage biomechanics and biology is reviewed. Future directions in cartilage biomechanics and mechano-biology research are proposed.

Anisotropy↗
PubMed1991

Knee hyaline cartilage evaluated with MR imaging: a cadaveric study involving multiple imaging sequences and intraarticular injection of gadolinium and saline solution.

Magnetic resonance (MR) imaging of cadaveric knees was performed to determine optimal sequences for visualization of hyaline cartilage. Six fresh-frozen cadaveric knees were imaged with a 1.5-T imager by means of standard and hybrid fat suppression (HFS) spin-echo techniques, with and without intraarticular injection of saline solution and gadopentetate dimeglumine. The knees then were sectioned at 4-mm intervals. Both the real and the imaged cartilage thicknesses were measured. Areas of cartilage thinning and focal defects seen in the cadaveric sections were most accurately matched, in both the presence and the absence of intraarticular saline solution simulating joint fluid, by images obtained with the T1-weighted HFS sequences. Accurate imaging of hyaline cartilage thickness with differentiation of cartilage from fluid was possible routinely. Standard and HFS spin-echo images obtained after intraarticular injection of gadopentetate dimeglumine depicted cartilage less accurately than HFS sequences either with or without saline injection. MR imaging with T1-weighted HFS sequences provided superior visualization of cartilage, enabling accurate measurements of cartilage thickness and differentiation of cartilage from saline solution simulating joint fluid.

Cartilage, Articular↗
PubMed1994

Value of laryngeal cartilage sclerosis as a predictor of outcome in patients with stage T3 glottic cancer treated with radiation therapy.

PURPOSE: To determine whether sclerosis of the laryngeal cartilages was a predictor of a poor outcome in patients with stage T3 glottic cancer treated with radiation therapy. MATERIALS AND METHODS: Thirty-three patients with stage T3 glottic cancer underwent computed tomography (CT) before radiation therapy. Twenty-two patients underwent posttreatment CT. The presence of cartilage sclerosis, cartilage erosion, marrow invasion, and cartilage necrosis was determined. RESULTS: Nineteen of the 33 patients had cartilage sclerosis at CT. Seventeen patients had sclerosis of a single laryngeal cartilage (14 arytenoid, two cricoid, and one thyroid), and two had sclerosis of adjacent laryngeal cartilages (arytenoid and cricoid in both cases). Of the 17 patients with isolated laryngeal cartilage sclerosis, disease was controlled with radiation therapy alone in 15 and with salvage laryngectomy in two. Both patients with cricoid and arytenoid sclerosis died of their original cancer despite undergoing early salvage laryngectomy. Of the 14 patients without sclerosis, eight had no evidence of disease, two died of their disease, and four died of intercurrent disease. CONCLUSION: T3 glottic cancer with isolated laryngeal cartilage sclerosis can be cured with radiation therapy.

Glottis↗
PubMed1996

Effects of compression and recovery on bovine articular cartilage: appearance on MR images.

PURPOSE: To determine the influence of compression and decompression on bovine articular cartilage as it appears on magnetic resonance (MR) images. MATERIALS AND METHODS: Consecutive spin-echo MR images (repetition time msec/echo time msec = 800/33) of normal bovine cartilage were obtained with increasing increments of pressure, to a maximum of 4.14 MPa (600 psi); this was followed by consecutive MR imaging after release of the pressure. RESULTS: Before compression, cartilage showed a laminated appearance. After incremental pressure, cartilage thickness progressively decreased; a short T2, low-signal-intensity lamina became thicker and more distinct at the articular surface; signal intensity of the deep cartilage zone initially was high and then gradually decreased; and at maximum pressure, the cartilage showed uniform low signal intensity. After release of pressure, signal intensity changes in the cartilage were sequentially reversed from those observed with compression. Image resolution and echo time influenced the appearance of these findings, particularly the low-signal-intensity line at the cartilage interface. CONCLUSION: The varying appearance and signal intensity characteristics of cartilage under pressure are hypothesized to result from a combination of net water loss and alteration in collagen orientational structure.

Animals↗
PubMed2006

Biomechanical modeling and design optimization of cartilage myringoplasty using finite element analysis.

The purpose of this study was to determine the acoustic transfer characteristics of cartilage for optimal cartilage myringoplasty. In order to do so, we developed a cartilage plate/tympanic membrane-coupled model using finite element analysis. Cartilage specimens of the tragus were obtained from fresh human cadavers, and the parameters of the tragus were determined by curve fitting and cross-calibration. A cartilage plate was used to repair an eardrum perforation, and the new coupled tympanic membrane-cartilage complex was loaded into our 3-dimensional biomechanical model of the middle ear for analysis. Our results show that first the beta-damping value of the cartilage plate depends on frequency. The value of beta damping was close to 3 x 10(-4) s at lower frequencies and 5 x 10(-6) s at higher frequencies. Secondly, reducing cartilage thickness leads to an improvement of its acoustic transfer qualities. From an acoustics point of view, the 0.1- to 0.2-mm cartilage plate seems to be most preferable with regard to tympanic membrane vibration. Furthermore, thicknesses of 0.2 mm at lower frequencies and 0.1 mm at higher frequencies were regarded as good compromises between sufficient mechanical stability and low acoustic transfer loss.

Biomechanical Phenomena↗