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Early diagnosis and treatment of pre- and early-stage osteoarthritis (OA) is important. However, the cellular and cartilaginous changes occurring during these stages remain unclear. We investigated the histological and immunohistochemical changes over time between pre- and early-stage OA in a rat model of traumatic injury. Thirty-six male rats were divided into two groups, control and OA groups, based on destabilization of the medial meniscus. Histological and immunohistochemical analyses of articular cartilage were performed on days 1, 3, 7, 10, and 14 postoperatively. Cell density of proteins associated with cartilage degradation increased from postoperative day one. On postoperative day three, histological changes, including chondrocyte death, reduced matrix staining, and superficial fibrillation, were observed. Simultaneously, a compensatory increase in matrix staining was observed. The Osteoarthritis Research Society International score increased from postoperative day seven, indicating thinner cartilage. On postoperative day 10, the positive cell density decreased, whereas histological changes progressed with fissuring and matrix loss. The proteoglycan 4-positive cell density increased on postoperative day seven. These findings will help establish an experimental model and clarify the mechanism of the onset and progression of pre- and early-stage traumatic OA., (© 2024. The Author(s).)

Objective: The purpose of this study was to determine the preventive effects of treadmill exercise or physiological loading on disuse atrophy in the rat knee joint cartilage and bone during hindlimb suspension., Design: Twenty male rats were divided into 4 experimental groups, including the control, hindlimb suspension, physiological loading, and treadmill walking groups. Histological changes in the articular cartilage and bone of the tibia were histomorphometrically and immunohistochemically evaluated 4 weeks after the intervention., Results: Compared with the control group, the hindlimb suspension group showed thinning of cartilage thickness, decreased matrix staining, and decreased proportion of noncalcified layers. Cartilage thinning, decreased matrix staining, and decreased noncalcified layers were suppressed in the treadmill walking group. The physiological loading group exhibited no significant suppression of cartilage thinning or decreased noncalcified layers, but the decreased matrix staining was significantly suppressed. No significant prevention of bone mass loss or changes in subchondral bone thickness were detected after physiological loading or treadmill walking., Conclusion: Disuse atrophy of the articular cartilage caused by unloading conditions could be prevented by treadmill walking in rat knee joints., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Objective: This study aimed to clarify physiological reloading on disuse atrophy of the articular cartilage and bone in the rat knee using the hindlimb suspension model., Design: Thirty male rats were divided into 3 experimental groups: control group, hindlimb suspension group, and reloading after hindlimb suspension group. Histological changes in the articular cartilage and bone of the tibia were evaluated by histomorphometrical and immunohistochemical analyses at 2 and 4 weeks after reloading., Results: The thinning and loss of matrix staining in the articular cartilage and the decrease in bone volume induced by hindlimb suspension recovered to the same level as the control group after 2 weeks of reloading. The proportion of the noncalcified and calcified layers of the articular cartilage and the thinning of subchondral bone recovered to the same level as the control group after 4 weeks of reloading., Conclusions: Disuse atrophy of the articular cartilage and bone induced by hindlimb suspension in the tibia of rats was improved by physiological reloading.

Objective: The study aim was to evaluate the histological relationship between osteoarthritis (OA) and articular cartilage in disuse atrophy induced by hindlimb unloading in a post-traumatic OA rat model., Design: Forty male rats were divided into the 4 following experimental groups: control, hindlimb suspension (HS), OA induced by destabilization of the medial meniscus (OA), and OA induction after hindlimb suspension (HS-OA). Histological changes in the articular cartilage of the tibia were evaluated by the Osteoarthritis Research Society International (OARSI) scores and histomorphometrical analyses at 2, 4, and 8 weeks after OA induction., Results: We confirmed that disuse atrophy of the articular cartilage was caused by thinning of the articular cartilage and the decrease in matrix staining for the nonloading period of 4 weeks. The OARSI scores and histomorphological analyses revealed that OA progressed significantly wider and deeper in the HS-OA group than in the OA group over time. In the sham group, disuse atrophy of the articular cartilage recovered at 2 weeks after reloading., Conclusions: This study revealed that OA progressed faster in cartilage atrophy than in normal articular cartilage. Further studies are required for investigating the mechanisms of disuse atrophy of cartilage and its association with OA using the biochemical and immunohistochemical analysis.

Objective: Curcumin monoglucuronide (TBP1901) is highly water soluble and can convert to free form curcumin, which has pharmacological effects, on intravenous administration. This study aimed to investigate the effectiveness of TBP1901 intra-articular injections in an osteoarthritis (OA) rat model., Methods: Sixty-four male Wistar rats (12 weeks old) who underwent destabilized medial meniscus (DMM) surgery were randomly separated into the TBP1901 injection or saline solution (control) injection group. They were sacrificed at 1, 2, 6, or 10 weeks postoperatively (weeks 1, 2, 6, and 10; n = 8 for each group). TBP1901 (30 mg/mL) or saline solution of 50 μL was injected into the knee joints twice a week during weeks 1 and 2 to investigate the effects in the acute phase of posttraumatic (PT) OA or once a week during weeks 6 and 10 to investigate it in the chronic phase of PTOA. Histology, immunohistochemistry, and micro-computed tomography were performed to evaluate the changes in OA., Results: TBP1901 injections significantly reduced synovial inflammation at weeks 1 and 2, and tumor necrosis factor-α expression in the articular cartilage at week 6. The TBP1901 injections also significantly suppressed articular cartilage damage, subchondral bone (SB) plate thickening, SB plate perforation, and osteophyte formation at week 10., Conclusions: TBP1901 intra-articular injections suppressed synovial inflammation in the acute phase of PTOA in DMM rats. In the chronic phase, TBP1901 suppresses articular cartilage damage and regulates SB plate changes.

The pathophysiology of primary osteoarthritis (OA) remains unclear. However, a specific subclassification of OA in relatively younger age groups is likely correlated with a history of articular cartilage damage and ligament avulsion. Surgical animal models of OA of the knee play an important role in understanding the onset and progression of post-traumatic OA and aid in the development of novel therapies for this disease. However, non-surgical models have been recently considered to avoid traumatic inflammation that could affect the evaluation of the intervention. In this study, an intra-articular cartilage lesion rat model induced by in vivo cyclic compressive loading was developed, which allowed researchers to (1) determine the optimal magnitude, speed, and duration of load that could cause focal cartilage damage; (2) assess post-traumatic spatiotemporal pathological changes in chondrocyte vitality; and (3) evaluate the histological expression of destructive or protective molecules that are involved in the adaptation and repair mechanisms against joint compressive loads. This report describes the experimental protocol for this novel cartilage lesion in a rat model.

This study aimed to examine the effects of an episode of in vivo cyclic loading on rat knee articular cartilage (AC) under medium-term observation, while also investigating relevant factors associated with the progression of post-traumatic osteoarthritis (PTOA). Twelve-week-old Wistar rats underwent one episode comprising 60 cycles of 20 N or 50 N dynamic compression on the right knee joint. Spatiotemporal changes in the AC after loading were evaluated using histology and immunohistochemistry at 3 days and 1, 2, 4, and 8 weeks after loading (n = 6 for each condition). Chondrocyte vitality was assessed at 1, 3, 6, and 12 hours after loading (n = 2 for each condition). A localized AC lesion on the lateral femoral condyle was confirmed in all subjects. The surface and intermediate cartilage in the affected area degenerated after loading, but the calcified cartilage remained intact. Expression of type II collagen in the lesion cartilage was upregulated after loading, whereas the superficial lubricin layer was eroded in response to cyclic compression. However, the distribution of superficial lubricin gradually recovered to the normal level 4 weeks after loading-induced injury. We confirmed that 60 repetitions of cyclic loading exceeding 20 N could result in cartilage damage in the rat knee. Endogenous repairs in well-structured joints work well to rebuild protective layers on the lesion cartilage surface, which may be the latent factor delaying the progression of PTOA., (© 2020 Orthopaedic Research Society. Published by Wiley Periodicals LLC.)

This study was aimed at investigating the use of ultrasound parameters obtained non-invasively through soft tissue (ST) to evaluate degeneration in cartilage and subchondral bone (SB) in the human knee. We developed a 3-D ultrasound system and introduced the ratio parameters R cb and R cbT to suppress the attenuation effect in the ST or in both the ST and cartilage. As reference measurements, the grade for cartilage by visual judgment (G sum ) and ultrasound parameters for the cartilage and the SB were directly evaluated under arthroscopy. R cb correlated significantly with G sum (r s  = -0.63) and with the corresponding parameter obtained directly under arthroscopy (r = 0.55). R cbT also correlated significantly with G sum (r s  = -0.46) but was not superior to R cb . R cb is considered to be an efficient parameter that reflects the total degeneration in both the cartilage and SB, including the information on cartilage thickness., (Copyright © 2020 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

We aimed to quantitatively investigate the relationship between amplitude-based pulse-echo ultrasound parameters and early degeneration of the knee articular cartilage. Twenty samples from six human femoral condyles judged as grade 0 or 1 according to International Cartilage Repair Society grading were assessed using a 15-MHz pulsed-ultrasound 3-D scanning system ex vivo. Surface roughness (R q ), average collagen content (A 1 ) and collagen orientation (A 12 ) in the superficial zone of the cartilage were measured via laser microscopy and Fourier transform infrared imaging spectroscopy. Multiple regression analysis with a linear mixed-effects model (LMM) revealed that a time-domain reflection coefficient at the cartilage surface (R c ) had a significant coefficient of determination with R q and A 12 (R LMMm 2 =0.79); however, R c did not correlate with A 1 . Concerning the collagen characteristic in the superficial zone, R c was found to be a sensitive indicator reflecting collagen disorganization, not collagen content, for the early degeneration samples., (Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Background: Osteochondral autologous transfer is one of the repair techniques for cartilage defects of knee with promising knee function recovery. There are no reports including histopathological images concerning human osteochondral tissue after osteochondral autologous transfer. This is the first report to present pathohistological findings of transplanted plugs and host tissues extracted from the human body 3 years after osteochondral autologous transfer. This study aimed to explore the cause factor of chronic pain using histological techniques., Case Presentation: A 67-year-old Japanese man presented with adjusted total knee arthroplasty 3 years after osteochondral autologous transfer. Although in pain, arthroscopic assessment was not severe. The specimens which was gained during total knee arthroplasty were investigated in gross and microscopically using immunohistochemical staining technic. Histological examination revealed that the gap between grafted plugs and host osteochondral tissues was filled with fibrous tissue that stained positive for type I collagen. A degenerative change and some neovascularity were observed in the regenerated tissue and host trabecular bone. Furthermore, cysts and bone marrow edema were observed., Conclusion: Our data suggests that the host osteochondral morbidity around grafted plugs might be related to chronical pain and revision surgery.

We investigated the effect of low-intensity pulsed ultrasound (LIPUS) treatment combined with mesenchymal stromal cell (MSC) injection for cartilage repair and subchondral bone reconstitution for treatment of osteochondral defects. An osteochondral defect was created on both femur grooves of Wistar rats. Four weeks later, bone marrow MSCs were injected into the right knee joint. The rats were divided into two intervention groups: without or with LIPUS irradiation. Cartilage repair was evaluated histologically based on the Wakitani cartilage repair score. Subchondral bone reconstitution was evaluated as bone volume (BV)/tissue volume (TV) by micro-computed tomography analysis. MSC injection improved the cartilage repair score, and LIPUS irradiation improved BV/TV. Combination treatment promoted both cartilage repair and BV/TV improvement. Thus, MSC injection combined with LIPUS irradiation is more effective than either treatment alone in promoting concurrent cartilage repair and subchondral reconstitution., (Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

An understanding of the articular cartilage degenerative process is necessary for the prevention and treatment of joint disease. The present study aimed to examine how long-term immobilization-induced cartilage degeneration is aggravated by remobilization. Sixty 8-week-old male Wistar rats were used in this study. The unilateral knee joint was immobilized using an external fixator for 8 weeks. The rats were killed at 0 and 3 days, and at 1, 2, 4 and 8 weeks after removing the fixator. After the rats were killed, the maximum knee extension angles were measured. Histological sections at the medial mid-condylar region (non-contact, transitional and contact regions of the femur and tibia) were prepared and scored. The cartilage thickness and number of chondrocytes were measured, and CD44 and Col2-3/4c expression levels were assessed immunohistochemically. The histological assessment revealed progressive aggravation of cartilage degeneration in the transitional region, with a decreased number of chondrocytes and CD44-positive chondrocytes as well as poor scoring over time, particularly in the tibia. Cyst formation was confirmed in the transitional region of the tibia at 8 weeks post-remobilization. The cartilage thickness in the transitional region was thicker than that in the contact region, particularly in the tibia. Col2-3/4c expression was observed in the non-contact and transitional regions, and the knee extension angle was recovered. In conclusion, immobilization-induced cartilage degeneration was aggravated by remobilization over time in the transitional region, followed by observations of a decreased number of chondrocytes and morphological disparity between different cartilage regions., (© 2016 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

The repair of articular cartilage is challenging owing to the restriction in the ability of articular cartilage to repair itself. Therefore, cell supplementation therapy is possible cartilage repair method. However, few studies have verified the efficacy and safety of cell supplementation therapy. The current study assessed the effect of exercise on early the phase of cartilage repair following cell supplementation utilizing mesenchymal stromal cell (MSC) intra-articular injection. An osteochondral defect was created on the femoral grooves bilaterally of Wistar rats. Mesenchymal stromal cells that were obtained from male Wistar rats were cultured in monolayer. After 4 weeks, MSCs were injected into the right knee joint and the rats were randomized into an exercise or no-exercise intervention group. The femurs were divided as follows: C group (no exercise without MSC injection); E group (exercise without MSC injection); M group (no exercise with MSC injection); and ME group (exercise with MSC injection). At 2, 4, and 8 weeks after the injection, the femurs were sectioned and histologically graded using the Wakitani cartilage repair scoring system. At 2 weeks after the injection, the total histological scores of the M and ME groups improved significantly compared with those of the C group. Four weeks after the injection, the scores of both the M and ME groups improved significantly. Additionally, the scores in the ME group showed a significant improvement compared to those in the M group. The improvement in the scores of the E, M, and ME groups at 8 weeks were not significantly different. The findings indicate that exercise may enhance cartilage repair after an MSC intra-articular injection. This study highlights the importance of exercise following cell transplantation therapy.

Cell-based therapy has been explored for articular cartilage regeneration. Autologous chondrocyte implantation is a promising cell-based technique for repairing articular cartilage defects. However, there are several issues such as chondrocyte de-differentiation. While numerous studies have been designed to overcome some of these issues, only a few have focused on the thermal environment that can affect chondrocyte metabolism and phenotype. In this study, the effects of different culture temperatures on human chondrocyte metabolism- and phenotype-related gene expression were investigated in 2D and 3D environments. Human chondrocytes were cultured in a monolayer or in a pellet culture system at three different culture temperatures (32°C, 37°C, and 41°C) for 3 days. The results showed that the total RNA level, normalized to the threshold cycle value of internal reference genes, was higher at lower temperatures in both culture systems. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and citrate synthase (CS), which are involved in glycolysis and the citric acid cycle, respectively, were expressed at similar levels at 32°C and 37°C in pellet cultures, but the levels were significantly lower at 41°C. Expression of the chondrogenic markers, collagen type IIA1 (COL2A1) and aggrecan (ACAN), was higher at 37°C than at 32°C and 41°C in both culture systems. However, this phenomenon did not coincide with SRY (sex-determining region Y)-box 9 (SOX9), which is a fundamental transcription factor for chondrogenesis, indicating that a SOX9-independent pathway might be involved in this phenomenon. In conclusion, the expression of chondrocyte metabolism-related genes at 32°C was maintained or enhanced compared to that at 37°C. However, chondrogenesis-related genes were further induced at 37°C in both culture systems. Therefore, manipulating the culture temperature may be an advantageous approach for regulating human chondrocyte metabolic activity and chondrogenesis.

Background: The differences of mechanical and histological properties between cartilage covered by menisci and uncovered by menisci may contribute to the osteoarthritis after meniscectomy and these differences are not fully understood. The purpose of this study is to investigate potential differences in the mechanical and histological properties, and in particular the collagen architecture, of the superficial cartilage layer and subchondral bone between regions covered and uncovered by menisci using immature knee., Methods: Osteochondral plugs were obtained from porcine tibial cartilage that was either covered or uncovered by menisci. Investigation of the thickness, mechanical properties, histology, and water content of the cartilage as well as micro-computed tomography analysis of the subchondral bone was performed to compare these regions. Collagen architecture was also assessed by using scanning electron microscopy., Results: Compared to the cartilage uncovered by menisci, that covered by menisci was thinner and showed a higher deformity to compression loading and higher water content. In the superficial layer of cartilage in the uncovered regions, collagen fibers showed high density, whereas they showed low density in covered regions. Furthermore, subchondral bone architecture varied between the 2 regions, and showed low bone density in covered regions., Conclusions: Cartilage covered by menisci differed from that uncovered in both its mechanical and histological properties, especially with regards to the density of the superficial collagen layer. These regional differences may be related to local mechanical environment in normal condition and indicate that cartilage covered by menisci is tightly guarded by menisci from extreme mechanical loading. Our results indicate that immature cartilage degeneration and subchondral microfracture may occur easily to extreme direct mechanical loading in covered region after meniscectomy.

Recognizing subtle cartilage changes in the preclinical stage of osteoarthritis (OA) is essential for early diagnosis. To this end, the ability of the ultrasound signal intensity to detect macroscopically undetectable cartilage change was investigated. In this study, cartilage of rabbit OA model and human OA samples was examined by macroscopic evaluation, ultrasound signal intensity, histology with Mankin scores, and Fourier transform infrared imaging (FTIRI) analysis. Rabbit OA was induced by anterior cruciate ligament transection and evaluated at 1, 2, 4 and 12 weeks. Twenty human samples were harvested during total knee arthroplasty from OA patients who had macroscopically normal human cartilage (ICRS grade 0) on the lateral femoral condyle. In the animal study, there was no macroscopic OA change at 2 weeks, but histology detected degenerative changes at this time point. Ultrasound signal intensity also detected degeneration at 2 weeks. In human samples, all samples were obtained from macroscopically intact site, however nearly normal (0 ≤ Mankin score <2), early OA (2 ≤ Mankin score <6), and moderate OA (6 ≤ Mankin score <10) samples were actually intermixed. Ultrasound signal intensity was significantly different among these 3 stages and was well correlated with Mankin scores (R = -0.80) and FTIR parameters related to collagen and proteoglycan content in superficial zone. In conclusion, ultrasound can detect microscopic cartilage deterioration when such changes do not exist macroscopically, reflecting superficial histological and biochemical changes.

The aim was to use repeat delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) to estimate glycosaminoglycan (GAG) content in reparative cartilage after osteochondral autogenous transfer (OAT). The study group comprised 7 knees of 7 patients that were examined three times by dGEMRIC, at 3, 6, and 12 months using a 1.5 Tesla MRI system in both OAT operated and nonoperated condyles at 90 min after the injection. The gadolinium diethylene triamine pentaacetic acid (Gd-DTPA)(2-) containing contrast medium (0.2 mmols/kg) was injected intravenously. The mean T1 values of the plug cartilage at 3, 6, and 12 months after OAT was 230 ± 40, 213 ± 31, and 230 ± 23 ms (mean ± SD), respectively. There were differences between the plug and control cartilage at 3 (p < 0.01) and 12 (p < 0.05) months after OAT, but not at 6 months (p = 0.089). No T1 changes were detected between the plug cartilage at the different time points after OAT. The fact that the GAG content of the OAT plugs were maintained for 12-month study period suggest that no major deterioration of load-bearing properties occurs in the cartilage after the OAT., (Copyright © 2011 Orthopaedic Research Society.)

The aim of this study was to determine how alendronate (ALN) alters cartilage degeneration and periarticular bone quality in a rabbit anterior cruciate ligament transection (ACLT) model of osteoarthritis (OA). Thirty rabbits underwent an ACLT on the left knee and a sham operation on the right knee. Fifteen rabbits received weekly subcutaneous injections of ALN (0.14 mg/kg) and 15 rabbits (the control [cont] group) received saline. Animal knees were divided into four groups: cont/sham, cont/ACLT, ALN/sham, and ALN/ACLT. Histological, radiological, and immunohistochemical indices were evaluated for each group. Bone volume ratios by micro-computed tomography showed that ALN prevented periarticular bone loss. Histologically, the cont/ACLT group had significantly worse cartilage damage than the cont/sham group 12 weeks after the surgery. However, the ALN/ACLT group had mild cartilage degeneration compared with that of the ALN/sham group. Immunohistochemical analysis showed that ALN suppressed the expression of matrix metalloproteinase-13, interleukin-1β, type-X collagen, vascular endothelial growth factor, and receptor activator of nuclear factor κB ligand in OA cartilage. ALN had a chondroprotective effect in an experimental rabbit model of OA., (Copyright © 2011 Orthopaedic Research Society.)

Although osteochondral grafting surgery is believed to replace damaged cartilage with healthy-looking normal cartilage, no study focuses on ultrasound quantification of those cartilage immediately after the surgery. It is unknown whether the ultrasound properties of damaged cartilage from trauma or osteonecrosis are same with each other. We have examined ultrasound properties of damaged cartilage, adjacent intact cartilage and plug cartilage during osteochondral grafting surgery for 15 knees of 15 patients, mean age of 43.4 (range, 14-61) years. Results showed that signal intensities of ultrasound (a measure of superficial cartilage integrity) of intact cartilage, damaged cartilage, and plug cartilage were 1.91 (arbitrary unit), 0.40, and 2.13, respectively, in 11 knees of 11 patients of traumatic cartilage lesions. Interval between signals of ultrasound (a parameter related to thickness) were 2.79 (micros), 1.90, and 2.85, respectively. The signal intensity and the interval between signals of plug cartilage were 533% (P < 0.01) and 150% (P < 0.01) of damaged cartilage, respectively. In four knees of four patients of osteonecrosis, the signal intensities of intact cartilage, damaged cartilage, and plug cartilage were 1.25, 0.30, and 1.39, respectively. The interval between signals were 2.36, 2.00, and 2.69, respectively. The signal intensity and the interval between signals of plug cartilage were 463% (P < 0.01) and 135% (P < 0.05) of damaged cartilage. We conclude that ultrasound properties of the damaged cartilage from trauma or osteonecrosis did not differ a lot especially in the late stages of osteonecrosis and that the osteochondral grafting surgery replaced the damaged cartilage with plug cartilage that had greater superficial cartilage integrity and greater thickness parameter immediately after the surgery. Long-term effect of the osteochondral grafting surgery should be verified in further study.

Introduction: There is a lack of data relating the macroscopic appearance of cartilage to its ultrasound properties. The purpose of the present study was to evaluate degenerated cartilage and healthy-looking cartilage using an ultrasound system., Methods: Ultrasound properties--signal intensity (a measure of superficial cartilage integrity), echo duration (a parameter related to the surface irregularity) and the interval between signals (that is, time of flight--which is related to the thickness and ultrasound speed of cartilage)--of 20 knees were measured at seven sites: the lateral femoral condyle (site A, anterior; site B, posterior), the medial condyle (site C), the lateral tibial plateau (site D, center; site E, under the meniscus) and the medial tibial plateau (site F, anterior; site G, posterior). The sites were evaluated macroscopically and classed using the International Cartilage Repair Society (ICRS) grading system., Results: The signal intensity of grade 0 cartilage was significantly greater than the intensities of grade 1, grade 2 or grade 3 cartilage. Signal intensity decreased with increasing ICRS grades. The signal intensity was greater at site B than at site C, site D, site F and site G. The signal intensity of grade 0 was greater at site B than at site E. The echo duration did not differ between the grades and between the sites. The interval between signals of grade 3 was less than the intervals of grade 0, grade 1 or grade 2. The interval between signals at site C was less than the intervals at site A, site B, site D, and site E., Conclusion: Site-specific differences in signal intensity suggest that a superficial collagen network may be maintained in cartilage of the lateral condyle but may deteriorate in cartilage of the medial condyle and the medial tibial plateau in varus knee osteoarthritis. Signal intensity may be helpful to differentiate ICRS grades, especially grade 0 cartilage from grade 1 cartilage.

We previously developed a novel ultrasound assessment system featuring wavelet transform to evaluate the material properties of articular cartilage. We aimed in this study to demonstrate the feasibility of quantitative evaluation of meniscus using ultrasound and to elucidate the relationships between its acoustic, mechanical, and biochemical properties. Meniscal disc specimens from mature pigs were assessed by ultrasound and compression testing, and their correlation was analyzed. A positive correlation was found between the ultrasound signal intensity and apparent Young's modulus (r=0.61). Subsequently, the porcine meniscal discs were treated with various enzymes and then characterized by ultrasound, by compression tests, by biochemical analyses, and by histology and immunohistochemistry. The signal intensity was decreased not by hyaluronidase but by collagenase treatment. Hyaluronidase-treated menisci showed a discrepancy between acoustic and mechanical properties, suggesting that the ultrasound reflection could not detect a reduction in proteoglycan content. Also, ultrasound signal intensity could only reflect superficial layers of the material. Several limitations exist at present, and further studies and improvements of the device are required. However, given the noninvasive nature and the requirement of only small equipment, this ultrasound assessment system will be an instrumental diagnostic tool for meniscal function in both research and clinical fields., (Copyright (c) 2007 Orthopaedic Research Society.)

Purpose: For successful autologous osteochondral transplantation, it is important that the cartilage in an implanted plug provide histologic replacement of damaged cartilage with cartilage that is structurally and mechanically normal. The purpose of this study was to investigate whether the press-fit technique reconstructs the normal hyaline cartilage and provides acoustic stiffness equal to that of normal intact cartilage., Methods: In 36 rabbits an osteochondral plug, 6 mm in diameter, was removed from the right patellar groove and grafted into a recipient hole, 5 mm in diameter, in the left patellar groove. Specimens at 2, 4, 8, 12, 24, and 52 weeks postoperatively were assessed by macroscopic and histologic observation and by use of an ultrasonic system. The ultrasonic acoustic stiffness, acoustic surface irregularity, and acoustic thickness of the implanted cartilage were examined and compared with normal intact cartilage., Results: The gross appearance of the implanted cartilage was glossy, maintained good surface smoothness, and survived well throughout the observation period. The cartilage recovered histologic features of hyaline cartilage. The acoustic stiffness decreased up to 12 weeks and then increased at 24 and 52 weeks after surgery. The acoustic stiffness at 8 or 12 weeks was significantly lower (acoustically softer) than that of control cartilage (P < .001). The acoustic stiffness at 52 weeks was equal to that of the control. The difference in acoustic surface irregularity was not significant. The acoustic thickness at 8 weeks was higher (acoustically thicker) than that of the control (P < .01)., Conclusions: Although the reason acoustically soft cartilage in plugs becomes acoustically stiff and whether the histology of the implanted cartilage had recovered completely remain unclear, the acoustic stiffness recovered to normal control values by 52 weeks postoperatively., Clinical Relevance: Postoperative care for up to 12 weeks should be taken after autologous osteochondral transplantation.

Although grafted osteochondral plugs should ideally have a smooth surface for mosaicplasty, surface incongruity is sometimes evident at the time of surgery. There may be no problem if there is depression of the grafted plugs, but graft protuberance may have an adverse effect. We studied five knees in five patients who had incongruity (protuberance or depression) of grafted osteochondral plugs at the time of mosaicplasty. The mean age at surgery was 36.6 years (range, 15-65 years), and the mean follow-up period was 32.9 months (range, 24-49 months). All patients underwent second-look arthroscopy after a mean post-surgical period of 14.8 months (range, 3-18 months). We divided the cases so that there were two in the protuberant group (P) and three in the depressed group (D). In P, all patients had a catching sensation about 4 months after surgery, and sometimes pain in the knee joint. Second-look arthroscopy revealed fissuring of the plugs and fibrillation around the recipient site. In D, there were no symptoms due to the depressed plugs. Second-look arthroscopy showed that the depressed areas were covered with fibrocartilage-like tissue, and that the joint surface was smooth. In conclusion, our clinical results and second-look arthroscopic evaluation suggest that isolated osteochondral plug depressions of not greater than 1 mm could still promote acceptable cartilage healing leading to good clinical outcomes. However, plug protuberance at mosaicplasty should always be avoided.

Background: There are growing concerns about thermal chondroplasty using radiofrequency energy to treat partial-thickness cartilage defects. However, most studies emphasize effects on chondrocyte viability, and other factors such as mechanical properties are less studied., Hypothesis: Radiofrequency energy may cause significant effects on articular cartilage other than chondrocyte viability., Study Design: Controlled laboratory study., Methods: Human osteoarthritic cartilage samples were obtained from total knee arthroplasty, and monopolar radiofrequency energy was applied using commercially available equipment. Material properties (compressive stiffness, surface roughness, and thickness) just before and after thermal treatment were determined using ultrasound. A series of biochemical analyses were also performed after explant culture of the samples., Results: The cartilage surface became smoother by radiofrequency energy, whereas cartilage stiffness or thickness was not altered significantly. Collagen fibrils, especially in the superficial layers, were converted to denatured form, whereas proteoglycan contents released in the media as well as retained in the tissue remained unchanged. The concentrations of matrix metalloproteinases (MMP-1 and MMP-2) were reduced remarkably., Conclusion: Radiofrequency energy is able to create a smooth cartilage surface and reduce catabolic enzymes at the cost of collagen denaturation and chondrocyte death in the superficial layers. The stiffness of the cartilage is not changed at time zero., Clinical Relevance: Further animal as well as clinical studies will be necessary to fully evaluate the long-term effects of radiofrequency energy.

Purpose: To analyze the mechanical effects of autogenous osteochondral grafting procedures on articular cartilage., Methods: The intensity, duration, and interval (indexes of stiffness, surface irregularity, and thickness) of the cartilage were assessed in a porcine model using an ultrasonic measurement system. In 7 of 12 knees, 6-mm-diameter plugs were harvested from the donor knees and grafted into 5-mm recipient holes at 3 different points per knee (21 plugs). In the remaining 5 knees, 5-mm plugs were harvested and returned to their original position (28 plugs)., Results: No significant differences in the intensity, duration, and interval of the cartilage were observed with the plugs before harvesting and after grafting by the paired t test. The 3 indexes of the 6- and 5-mm plugs that were grafted correlated significantly with those before they were., Conclusions: These results suggest that osteochondral graft surgery does not affect the stiffness, surface irregularity, and thickness of the cartilage of the plugs at time zero.

We investigated quantitative changes over time in ultrasound signal intensity (an index of stiffness), signal duration (an index of surface irregularity), and interval between signals (an index of thickness) of plug cartilage in an animal model of autologous osteochondral grafting. A full-thickness osteochondral plug was surgically removed and replaced in male Japanese white rabbits (n = 22). Specimens obtained at day 0 and weeks 2, 4, 8, 12 and 24 postoperatively were assessed using an ultrasound system and by macroscopic and histological evaluation (modified Mankin's score). Histology revealed that the plug sank until 2 weeks postoperatively, and that newly formed cartilage-like tissue covered the plug, but at 24 weeks the tissue detached. The plug itself survived well throughout the period of observation. Although the signal intensity at the plug site was same as that in the sham operated contralateral knee at day 0, from 2 to 24 weeks postoperatively it was less than that in the sham knee. At 8 weeks, this difference was significant (P < 0.05). Modified Mankin's score revealed early degenerative changes at the site, but macroscopic examination did not. Signal intensity correlated significantly with score (both at day 0 and at the five postoperative time points [P < 0.05, r = -0.91] and as a whole [P < 0.05, r = -0.36]). Signal intensity also significantly correlated with the individual subscores for 'cartilage structure' (P < 0.05, r = -0.32) and 'cartilage cells' (P < 0.05, r = -0.30) from the modified Mankin's score, but not significantly with subscores for 'staining' and 'tidemark'. Signal duration correlated significantly with total score (as a whole [P < 0.05, r = 0.34]), but not significantly with the score for cartilage structure (P = 0.0557, r = 0.29). The interval between signals reflected well the actual thickness of the plug site. The significant relationships between ultrasound signal intensity and scores suggest that early degenerative changes in plug cartilage and cartilage-like tissue, especially in the superficial layer, are detectable by high-frequency ultrasound assessment.