Osteochondral Cores Research Articles

Comparative study of depth-dependent characteristics of equine and human osteochondral tissue from the medial and lateral femoral condyles

Articular cartilage defects are common after joint injuries. When left untreated, the biomechanical protective function of cartilage is gradually lost, making the joint more susceptible to further damage, causing progressive loss of joint function and eventually osteoarthritis (OA). In the process of translating promising tissue-engineering cartilage repair approaches from bench to bedside, pre-clinical animal models including mice, rabbits, goats, and horses, are widely used. The equine species is becoming an increasingly popular model for the in vivo evaluation of regenerative orthopaedic approaches. As there is also an increasing body of evidence suggesting that successful lasting tissue reconstruction requires an implant that mimics natural tissue organization, it is imperative that depth-dependent characteristics of equine osteochondral tissue are known, to assess to what extent they resemble those in humans. Therefore, osteochondral cores (4-8 mm) were obtained from the medial and lateral femoral condyles of equine and human donors. Cores were processed for histology and for biochemical quantification of DNA, glycosaminoglycan (GAG) and collagen content. Equine and human osteochondral tissues possess similar geometrical (thickness) and organizational (GAG, collagen and DNA distribution with depth) features. These comparable trends further underscore the validity of the equine model for the evaluation of regenerative approaches for articular cartilage.

Relationship between cartilage and subchondral bone lesions in repetitive impact trauma-induced equine osteoarthritis

To correlate degenerative changes in cartilage and subchondral bone in the third carpal bone (C3) of Standardbred racehorses with naturally occurring repetitive trauma-induced osteoarthritis. Fifteen C3, collected from Standardbred horses postmortem, were assessed for cartilage lesions by visual inspection and divided into Control (CO), Early Osteoarthritis (EOA) and Advanced Osteoarthritis (AOA) groups. Two osteochondral cores were harvested from corresponding dorsal sites on each bone and scanned with a micro-computed tomography (CT) instrument. 2D images were assembled into 3D reconstructions that were used to quantify architectural parameters from selected regions of interest, including bone mineral density and bone volume fraction. 2D images, illustrating the most severe lesion per core, were scored for architectural appearance by blinded observers. Thin sections of paraffin-embedded decalcified cores stained with Safranin O-Fast Green, matched to the micro-CT images, were scored using a modified Mankin scoring system. Subchondral bone pits with deep focal areas of porosity were seen more frequently in AOA than EOA but never in CO. Articular cartilage damage was seen in association with a reduction in bone mineral and loss of bone tissue. Histological analyses revealed significant numbers of microcracks in the calcified cartilage of EOA and AOA groups and a progressive increase in the score compared with CO bones. The data reveal corresponding, progressive degenerative changes in articular cartilage and subchondral bone, including striking focal resorptive lesions, in the third carpal bone of racehorses subjected to repetitive, high impact trauma.

Osteochondral Autograft Transfer for Treatment of Osteochondritis Dissecans of the Caudocentral Humeral Head in Dogs

To establish whether osteochondral autograft transfer (OAT) procedures for osteochondritis dissecans (OCD) of the canine caudocentral humeral head would restore articular contour, resurface osteochondral defects, and resolve lameness in dogs with OCD. Case series. Dogs (n=14) with caudocentral humeral head OCD (16 shoulders). After arthroscopic assessment, the humeral head was exposed by arthrotomy. The OCD lesion was debrided and OATS(™) instrumentation used for resurfacing the defect with osteochondral core grafts collected from the stifle. Recipient sockets were created to maximally resurface articular lesions. Outcomes measures included clinical, radiographic, and arthroscopic examination at 12-18 weeks and clinical examination at 12-46 months (mean, 30.8 months) postoperatively. Resurfacing of the humeral head was achieved in all dogs. Subjectively, lameness resolved in 9 of 16 limbs by 5-6 weeks postoperatively, and in 13 limbs by 12-18 weeks. Radiographically, all autografts were maintained. On second-look arthroscopy, the grafted section was intact, resilient on probing, satisfactorily conformed to the adjacent articular contour, and grossly appeared consistent with hyaline or fibrocartilage depending on the graft source. Of 12 limbs available for 12-46 months reevaluation, none were considered lame and mild discomfort on shoulder manipulation was recorded for only 1 joint. OAT procedures are technically feasible in the caudocentral aspect of the canine humeral head. Articular contour reconstruction, resurfacing of osteochondral defects, and amelioration or resolution of short-term lameness may be achieved.

Cartilage viability and catabolism in the intact porcine knee following transarticular impact loading with and without articular fracture

Posttraumatic arthritis commonly develops following articular fracture. The objective of this study was to develop a closed joint model of transarticular impact with and without creation of an articular fracture that maintains the physiologic environment during loading. Fresh intact porcine knees were preloaded and impacted at 294 J via a drop track. Osteochondral cores were obtained from the medial and lateral aspects of the femoral condyles and tibial plateau. Chondrocyte viability was assessed at days 0, 3, and 5 postimpact in sham, impacted nonfractured, and impacted fractured joints. Total matrix metalloproteinase (MMP) activity, aggrecanase (ADAMTS-4) activity, and sulfated glycosaminoglycan (S-GAG) release were measured in culture media from days 3 and 5 posttrauma. No differences were observed in chondrocyte viability of impacted nonfractured joints (95.9 ± 6.9%) when compared to sham joints (93.8 ± 7.7%). In impacted fractured joints, viability of the fractured edge was 40.5 ± 27.6% and significantly lower than all other sites, including cartilage adjacent to the fractured edge (p < 0.001). MMP and aggrecanase activity and S-GAG release were significantly increased in specimens from the fractured edge. This study showed that joint impact resulting in articular fracture significantly decreased chondrocyte viability, increased production of MMPs and aggrecanases, and enhanced S-GAG release, whereas the same level of impact without fracture did not cause such changes.

Optical Coherence Tomography Detection of Subclinical Traumatic Cartilage Injury

Posttraumatic arthritis is a major cause of disability. Current clinical imaging modalities are unable to reliably evaluate articular cartilage damage before surface breakdown, when potentially reversible changes are occurring. Optical coherence tomography (OCT) is a nondestructive imaging technology that can detect degenerative changes in articular cartilage with an intact surface. This study tests the hypothesis that OCT detects acute articular cartilage injury after impact at energy levels resulting in chondrocyte death and microstructural changes, but insufficient to produce macroscopic surface damage. Bovine osteochondral cores underwent OCT imaging and were divided into a control with no impact or were subjected to low (0.175 J) or moderate (0.35 J) energy impact. Cores were reimaged with OCT after impact and the OCT signal intensity quantified. A ratio of the superficial to deep layer intensities was calculated and compared before and after impact. Chondrocyte viability was determined 1 day after impact followed by histology and polarized microscopy. Macroscopic changes to the articular surface were not observed after low and moderate impact. The OCT signal intensity ratio demonstrated a 27% increase (P = 0.006) after low impact and a 38% increase (P = 0.001) after moderate impact. Cell death increased by 150% (P < 0.001) and 200% (P < 0.001) after low and moderate energy impacts, respectively. When compared with unimpacted controls, both Mankin histology and David-Vaudey polarized microscopy scores increased (P = 0.036 and P = 0.002, respectively) after moderate energy impact. This study shows that OCT detects acute cartilage changes after impact injury at levels insufficient to cause visible damage to the articular surface but sufficient to cause chondrocyte death and microscopic matrix damage. This finding supports the use of OCT to detect microstructural subsurface cartilage damage that is poorly visualized with conventional imaging.

Evaluation of chondrocyte death in canine osteochondral explants exposed to a 0.5% solution of bupivacaine

To evaluate chondrocyte death in canine articular cartilage exposed in vitro to bupivacaine with and without methylparaben and to compare viability for cartilage with intact or mechanically debrided surfaces. Both glenohumeral joints from 10 adult canine cadavers. 10 osteochondral cores were harvested from each of the 20 humeral heads; synovium and 1 core from each joint were examined to verify joint health, and the other 9 cores were exposed to canine chondrocyte culture medium (CCCM), a 0.5% solution of bupivacaine, or 0.5% solution of bupivacaine with methylparaben for 5, 15, or 30 minutes. For the superficial zone of surface-intact chondrocytes, bupivacaine with methylparaben caused a significantly higher percentage of chondrocyte death at 5 minutes (47.7%) than did bupivacaine (23.6%) or CCCM (25.4%). Bupivacaine (53.8%) and bupivacaine with methylparaben (62.5%) caused a significantly higher percentage of chondrocyte death at 30 minutes than did CCCM (20.0%). For the superficial zone of chondrocytes with debrided surfaces, bupivacaine with methylparaben caused a significantly higher percentage of chondrocyte death at 30 minutes (59%) than it did at 5 minutes (37.7%). Bupivacaine with methylparaben caused a significantly higher percentage of chondrocyte death at 30 minutes (59.0%) than did CCCM (28.9%). For middle and deep zones of chondrocytes, treatment solution and surface debridement had minimal effects on percentage of chondrocyte death. Bupivacaine and bupivacaine with methylparaben were cytotoxic to canine articular chondrocytes in vitro. Intra-articular administration of bupivacaine is not recommended for clinical use until additional studies are conducted.

Assessing degeneration of human articular cartilage with ultra-short echo time (UTE) T2* mapping

To examine the sensitivity of ultra-short echo time (UTE) T(2)* mapping to collagen matrix degeneration in human articular cartilage. Magnetic resonance imaging (MRI) UTE-T(2)* maps and standard T(2) maps were acquired on four human tibial plateau explants. Thirty-three osteochondral cores were harvested for polarized light microscopy (PLM), and composition analyses. Collagen matrix integrity was evaluated from PLM and histological images. Matrix integrity and composition was compared to standard T(2) values and UTE-T(2)* values on a spatially registered basis. UTE-T(2)* values varied with matrix degeneration (P=0.008) and were lower in severely degraded cartilage compared to healthy tissue (P=0.012). A trend for higher UTE-T(2)* values in healthy tissue compared to mildly degenerate tissue (P=0.051) was detected. Standard T(2) values were not found to vary with matrix degeneration (P=0.13) but tended to be higher in severely degraded cartilage compared to healthy tissue. UTE-T(2)* value variations were independent of type-II collagen and glycosaminoglycan contents. UTE-T(2)* mapping of deep cartilage, adjacent to subchondral bone, was more robust than standard T(2) mapping in this zone. UTE-T(2)* mapping of articular cartilage is sensitive to matrix degeneration and detects short-T(2) signal, particularly in deep tissue, that is not well captured by standard T(2) mapping. Correlation of UTE-T(2)* values and PLM indices supports the hypothesis that both may be sensitive to collagen microstructure. Further exploration of UTE-T(2)* mapping as a non-invasive tool to detect early articular cartilage degeneration is warranted.

Mapping of donor and recipient site properties for osteochondral graft reconstruction of subchondral cystic lesions in the equine stifle joint

To improve osteochondral graft reconstruction of subchondral cystic lesions in the medial and lateral femoral condyles by matching the material properties of donor and recipient sites. To measure biomechanical and biochemical parameters that influence the function and healing of osteochondral grafts used to reconstruct subchondral cystic lesions. Suitable donor sites are available within the stifle joint for reconstructing the femoral condyles, despite considerable regional property variation. Fifty-six osteochondral cores were harvested from 6 distal femurs for initial studies that determined subchondral bone modulus of elasticity and ultimate stress. In a second study, 28 osteochondral cores were harvested from 6 distal femurs to measure cartilage aggregate modulus, thickness and sulphated glycosaminoglycan (sGAG) content. Using micro-CT imaging, subchondral bone mineral density and bone volume fraction were also measured. In both studies 2-dimensional contour plots using a bicubic interpolation method and normalised data were generated to allow visual comparison of joint surface characteristics. Statistical comparisons between donor and recipient site raw data were made using an ANOVA for repeated measures with a post hoc Tukey test. Material properties of cartilage and bone vary considerably over the surface of the stifle joint but the central region of the medial condyle, where subchondral cystic lesions freqdently occur, typically demonstrated bone strength and modulus values of the highest observed. Cartilage thickness and aggregate modulus were highest in the medial femoral condyle and axial aspect of the lateral condyle. Material properties of the grafts from the trochlear groove and axial aspect of the lateral trochlear ridge were the closest match for those found in the medial condyle, whereas properties of the lateral condyle were most similar to those found in the trochlear groove and axial aspect of the medial trochlear ridge.

Progressive Chondrocyte Death After Impact Injury Indicates a Need for Chondroprotective Therapy

Background Impact injury to articular cartilage can lead to posttraumatic osteoarthritis. Hypotheses This study tests the hypotheses that (1) chondrocyte injury occurs after impact at energies insufficient to fracture the cartilage surface, and that (2) cartilage injury patterns vary with impact energy, time after injury, and cartilage thickness. Study Design Controlled laboratory study. Methods Fresh bovine osteochondral cores were randomly divided into 5 groups: (1) control, (2) 0.35 J, (3) 0.71 J, (4) 1.07 J, and (5) 1.43 J impact energies. Cores were subjected to computer-controlled impact loading and full-thickness sections were then prepared and incubated in Dulbecco’s Modified Eagle’s Medium/F12 at 37°C. Adjacent sections were harvested 1 and 4 days after impact for viability staining and fluorescent imaging. The area of dead and living chondrocytes was quantified using custom image analysis software and reported as a percentage of total cartilage area. Results The highest impact energy fractured the cartilage in all cores (1.43 J, n = 17). Seventy-three percent and 64% of the osteochondral cores remained intact after lower energy impacts of 0.71 J and 1.07 J, respectively. At lower energy levels, fractured cores were thinner (P <.01) than those remaining intact. In cores remaining intact after impact injury, chondrocyte death increased with increasing impact energy (P <.05) and with greater time after impact (P <.05). A progressive increase in dead cells near the bone/cartilage interface and at the articular surface was observed. Conclusion These data showing progressive chondrocyte death after impact injury at energies insufficient to fracture the cartilage surface demonstrate a potential need for early chondroprotective therapy. Clinical Relevance These data show that efforts to reduce chondrocyte morbidity after joint injury may be a useful strategy to delay or prevent the onset of posttraumatic osteoarthritis.

Optical coherence tomography grading correlates with MRI T2 mapping and extracellular matrix content

Optical coherence tomography (OCT) and T2 mapping are emerging clinical imaging technologies with potential to detect subsurface changes in cartilage retaining a macroscopically intact articular surface. This study tests the hypothesis that OCT correlates with magnetic resonance imaging (MRI) T2 values, and that OCT signal is sensitive to cartilage matrix degeneration. Forty-five osteochondral cores were harvested from five human tibial plateau explants after MRI T2 mapping. Cores underwent OCT imaging and were graded as follows: A, obvious birefringence; B, no birefringence; C, subsurface voids and/or irregular surface. Extracellular matrix content was determined and cores underwent histologic and polarized light microscopy (PLM) evaluation. Grade B and C cores had 25% higher superficial T2 values (p = 0.047) and 50% higher deep T2 values (p = 0.012) than grade A cores. Grade B and C cores had 36% higher glycosaminoglycan (GAG) content compared to grade A cores (p = 0.009). Histology and PLM demonstrated increased surface irregularity and structural disorganization with increasing OCT grade. OCT grade and T2 value increased with increasing collagen disorganization, suggesting that MRI T2 mapping and OCT are sensitive to changes in collagen structure. Our results demonstrate the ability of OCT and T2 mapping to detect early cartilage degeneration in clinically normal appearing cartilage.

Early Clinical Experience with Osteochondral Autograft Transfer for Treatment of Osteochondritis Dissecans of the Medial Humeral Condyle in Dogs

To establish whether osteochondral autograft transfer (OAT) procedures for osteochondritis dissecans (OCD) of the canine elbow would restore articular contour, resurface osteochondral defects with hyaline cartilage, and resolve lameness in the short term. Case series. Dogs (n=27) with medial humeral condylar OCD. After arthroscopic assessment, the medial humeral condyle was exposed by arthrotomy. Medial coronoid disease (MCD) was managed by subtotal coronoid ostectomy, then the OCD lesion debrided and OATS instrumentation used for resurfacing the defect with osteochondral core grafts collected from the stifle. Recipient sockets were created to maximally resurface OCD lesions. Six elbows also had proximal ulnar osteotomy. Outcomes measures included subjective clinical, radiographic, and arthroscopic examination at 12-18 weeks. Of 33 treated elbows, 30 also had MCD. Accurate reconstruction of the medial humeral condylar surface was achieved in all joints. Lameness resolved in 3-13 weeks in 26 of 31 limbs with follow-up. Arthroscopic outcomes for elbows with concomitant MCD but without proximal ulnar osteotomy were variable (14/24 good, 5/24 intermediate, 5/24 poor). Short-term outcome for OCD without MCD (n=2) and when proximal ulnar osteotomy (n=5) was performed were positive. Long-term assessments of 7 dogs suggested minimal donor site morbidity. OAT procedures are technically feasible in the canine elbow. In elbows with concurrent MCD, proximal ulnar osteotomy may improve likelihood of positive clinical outcome. OAT procedures warrant further evaluation as a treatment option for selected cases of OCD involving the canine medial humeral condyle.

Increased hydraulic conductance of human articular cartilage and subchondral bone plate with progression of osteoarthritis

Osteoarthritis (OA) is characterized by progressive degeneration of articular cartilage and remodeling of the subchondral bone plate, comprising calcified cartilage and underlying subchondral bone. Calcified cartilage remodeling due to upward invasion by vascular canals or to calcified cartilage erosion may contribute to biomechanical alteration of the osteochondral tissue and its subchondral bone plate component. The study hypothesis was that hydraulic conductance of osteochondral tissue and subchondral bone plate increases with structural changes indicative of increasing stages of OA. Osteochondral cores were harvested from the knees of cadaveric tissue donors and from discarded fragments from patients with OA undergoing knee surgery. The osteochondral cores from tissue donors were macroscopically normal, and the cores from patients with OA had partial-thickness or full-thickness erosion to bone. The cores were perfusion-tested to determine the hydraulic conductance, or ease of fluid flow, in their native state and after enzymatic removal of cartilage. Adjacent portions were analyzed by 3-dimensional histology for calcified cartilage, subchondral bone, and subchondral bone plate thickness and vascular canal density. Hydraulic conductance of native osteochondral tissue and subchondral bone plate was higher (2,700-fold and 3-fold, respectively) in fully eroded samples than in normal samples. The calcified cartilage layer was thicker (1.5-fold) in partially eroded samples than in normal samples but thinner and incomplete in fully eroded samples. Subchondral bone plate vascularity was altered with increasing stages of OA. During joint loading, increased hydraulic conductance of the osteochondral tissue and subchondral bone plate could have deleterious biomechanical consequences for cartilage. Increased fluid exudation from overlying and opposing cartilage, increased fluid depressurization, and increased cartilage tissue strains could lead to chondrocyte death and cartilage damage.

Shear deformation kinematics during cartilage articulation: effect of lubrication, degeneration, and stress relaxation.

During joint articulation, the biomechanical behavior of cartilage not only facilitates load-bearing and low-friction, but also provides regulatory cues to chondrocytes. Elucidation of cartilage kinematics under combined compression and shearing conditions clarifies these cues in health and disease. The objectives of this study were to elucidate the effects of lubricant, tissue degeneration, and stress relaxation duration on cartilage shear kinematics during articulation. Human osteochondral cores with normal and mildly degenerate surface structures were isolated. Paired blocks from each core were apposed, compressed, allowed to stress relax for 5 or 60 min, and shear tested with a micro-scale video microscopy system using phosphate-buffered saline (PBS) or synovial fluid as lubricant. During applied lateral motion, local and overall shear strain (Exz) of articular cartilage were determined. The applied lateral displacement at which Exz reached 50% of the peak (Deltax(1/2)) was also determined. Quantitatively, surface Exz increased at the onset of lateral motion and peaked just as surfaces detached and slid. With continued lateral motion, surface Exz was maintained. After short stress relaxation, effects of lubrication on Exz and Deltax(1/2) were not apparent. With prolonged stress relaxation, Exz and Deltax(1/2) near the articular surface increased markedly when PBS was used as lubricant. Similar patterns were observed for overall Exz and Deltax(1/2). With degeneration, surface Exz was consistently higher for all cases after the onset of lateral motion. Thus, cartilage shear kinematics is markedly affected by lubricant, cartilage degeneration, and loading duration. Changes in these factors may be involved in the pathogenesis of osteoarthritis.

Biomechanics of cartilage articulation: Effects of lubrication and degeneration on shear deformation

To characterize cartilage shear strain during articulation, and the effects of lubrication and degeneration. Human osteochondral cores from lateral femoral condyles, characterized as normal or mildly degenerated based on surface structure, were selected. Under video microscopy, pairs of osteochondral blocks from each core were apposed, compressed 15%, and subjected to relative lateral motion with synovial fluid (SF) or phosphate buffered saline (PBS) as lubricant. When cartilage surfaces began to slide steadily, shear strain (Exz) and modulus (G) overall in the full tissue thickness and also as a function of depth from the surface were determined. In normal tissue with SF as lubricant, Exz was highest (0.056) near the articular surface and diminished monotonically with depth, with an overall average Exz of 0.028. In degenerated cartilage with SF as lubricant, Exz near the surface (0.28) was 5-fold that of normal cartilage and localized there, with an overall E(xz) of 0.041. With PBS as lubricant, Exz values near the articular surface were approximately 50% higher than those observed with SF, and overall Exz was 0.045 and 0.062 in normal and degenerated tissue, respectively. Near the articular surface, G was lower with degeneration (0.06 MPa, versus 0.18 MPa in normal cartilage). In both normal and degenerated cartilage, G increased with tissue depth to 3-4 MPa, with an overall G of 0.26-0.32 MPa. During articulation, peak cartilage shear is highest near the articular surface and decreases markedly with depth. With degeneration and diminished lubrication, the markedly increased cartilage shear near the articular surface may contribute to progressive cartilage deterioration and osteoarthritis.

Optimizing CO2 normalizes pH and enhances chondrocyte viability during cold storage

Fresh osteochondral allografts are an important treatment option for the repair of full-thickness articular cartilage defects. Viable chondrocytes within the transplanted tissue are considered important to maintaining matrix integrity. The purpose of this study is to determine whether an increase in pH decreases chondrocyte viability during cold storage and whether equilibration of Dulbecco's modified Eagle's medium (DMEM) in 5% CO(2) normalizes pH and increases chondrocyte survival during storage at 4 degrees C. Freshly isolated bovine articular chondrocytes cultured in alginate beads were stored for up to 5 days at 4 degrees C or 37 degrees C in DMEM exposed to ambient air or in DMEM equilibrated with 5% CO(2). Chondrocyte viability was determined by flow cytometry. Physiologic pH was maintained when DMEM was equilibrated with 5% CO(2), while pH increased in ambient air. After 5 days of storage at 4 degrees C, chondrocyte necrosis was higher when stored in ambient air than if equilibrated with 5% CO(2). No decrease in chondrocyte viability was observed with storage at 37 degrees C. In addition, chondrocyte viability in bovine cartilage osteochondral cores was examined after storage for 14 days at 4 degrees C in DMEM with and without HEPES, and with and without 5% CO(2). Under these conditions, the superficial layer of chondrocytes was more viable when stored in DMEM with HEPES or DMEM equilibrated with 5% CO(2) than when stored in DMEM in ambient air. This data shows that an increase in pH decreased bovine chondrocyte viability when refrigerated at 4 degrees C in DMEM, and that optimization of CO(2) normalized pH and improved chondrocyte viability during cold storage in DMEM.

Lidocaine Exhibits Dose- and Time-Dependent Cytotoxic Effects on Bovine Articular Chondrocytes in Vitro

Background Intra-articular lidocaine is commonly used. Purpose This study was conducted to determine whether short-term exposures to 1% and 2% lidocaine are toxic to articular chondrocytes, whether this is due to pH, and whether an intact articular surface is protective. Study Design Controlled laboratory study. Methods Fresh bovine articular chondrocytes in alginate bead cultures were treated with 1% or 2% lidocaine or buffered saline (pH 7.4, 7.0, and 5.0) for 15, 30, or 60 minutes. Chondrocytes were then analyzed for viability by flow cytometry 1 hour, 1 day, and 1 week later. Bovine osteochondral cores with and without the superficial 1 mm of cartilage removed were submerged in either 0.9% saline (pH 7.4) or in 1% or 2% lidocaine for 30 minutes and assessed for viability using fluorescent microscopy. Results Chondrocyte viability decreased after just 15-minute exposures to 1% lidocaine. Longer exposures to 1% and 2% lidocaine further reduced chondrocyte viability. Chondrotoxicity of 2% lidocaine was greater than 1% lidocaine. There was no difference in chondrocyte viability after exposures to saline solutions of pH 7.4, 7.0, or 5.0. An intact articular surface did not affect lidocaine's chondrotoxic effects. Conclusion Results show dose- and time-dependent cytotoxic effects of lidocaine on bovine articular chondrocytes. Reduction of pH alone did not decrease chondrocyte viability, and the intact articular surface was not protective. Clinical Relevance Although lidocaine chondrotoxicity was less than previously reported with bupivacaine, these observations suggest that local anesthetics as a class of drugs may negatively affect articular cartilage.

In Vitro Exposure to 0.5% Bupivacaine Is Cytotoxic to Bovine Articular Chondrocytes

Intra-articular use of 0.5% bupivacaine is common in arthroscopic surgery. This study was conducted to test the hypotheses that (1) 0.5% bupivacaine is toxic to articular chondrocytes, and (2) the intact articular surface protects chondrocytes from the effects of short-term exposure to 0.5% bupivacaine. Freshly isolated bovine articular chondrocytes were prepared into alginate bead cultures and were treated with 0.5% bupivacaine solution or 0.9% saline for 15, 30 or 60 minutes, washed, and returned to growth media. Chondrocytes were recovered from alginate 1 hour, 1 day, and 1 week after bupivacaine exposure; they were fluorescently labeled to identify apoptotic and dead cells and were analyzed by flow cytometry. Twelve osteochondral cores were harvested from bovine knees. The superficial 1 mm of cartilage was removed from 6 cores (top-off). Intact and top-off cores were submerged in 0.9% saline or 0.5% bupivacaine solution for 30 minutes and then maintained in chondrocyte growth media for 24 hours. Live-cell/dead-cell fluorescent imaging was assessed using confocal microscopy. Greater than 99% chondrocyte death/apoptosis was observed in all bupivacaine-exposed alginate bead cultures compared with 20% cell death in saline-treated controls (P < .05). Osteochondral cores with intact surfaces treated with 0.5% bupivacaine showed 42% dead chondrocytes. When the articular surface was removed, 0.5% bupivacaine resulted in increased cell death, with 75% dead chondrocytes (P < .05). Results show that 0.5% bupivacaine solution is cytotoxic to bovine articular chondrocytes and articular cartilage in vitro after only 15 to 30 minutes' exposure. The intact bovine articular surface has some chondroprotective effects. Because healthy chondrocytes are important for maintenance of the cartilage matrix, chondrocyte loss may contribute to cartilage degeneration. This study shows a cytotoxic effect of 0.5% bupivacaine solution on bovine articular chondrocytes in vitro. Although these results cannot be directly extrapolated to the clinical setting, the data suggest that caution should be exercised in the intra-articular use of 0.5% bupivacaine.

The treatment of osteochondral lesions using a combination of autologous chondrocyte implantation and autograft

In this study a combination of autologous chondrocyte implantation (ACI) and the osteochondral autograft transfer system (OATS) was used and evaluated as a treatment option for the repair of large areas of degenerative articular cartilage. We present the results at three years post-operatively. Osteochondral cores were used to restore the contour of articular cartilage in 13 patients with large lesions of the lateral femoral condyle (n = 5), medial femoral condyle (n = 7) and patella (n = 1). Autologous cultured chondrocytes were injected underneath a periosteal patch covering the cores. After one year, the patients had a significant improvement in their symptoms and after three years this level of improvement was maintained in ten of the 13 patients. Arthroscopic examination revealed that the osteochondral cores became well integrated with the surrounding cartilage. We conclude that the hybrid ACI/OATS technique provides a promising surgical approach for the treatment of patients with large degenerative osteochondral defects.

Indentation testing of human cartilage: sensitivity to articular surface degeneration.

To determine, for clinical indentation testing of human articular cartilage, the effects of aging and degeneration on indentation stiffness and traditional indices of cartilage degeneration; the relationship between indentation stiffness and indices of degeneration; and the sensitivity and specificity of indentation stiffness to cartilage degeneration. Osteochondral cores from femoral condyles of cadaveric human donors were harvested. Samples were distributed into experimental groups based on donor age (young [20-39 years], middle [40-59 years], and old [>/=60 years]), and a macroscopic articular surface appearance that was either normal or mildly degenerate, without deep erosion. Samples were analyzed for indentation stiffness, cartilage thickness, India ink staining (quantitated as the reflected light score), and Mankin-Shapiro histopathology score. Indentation stiffness, India ink staining, and the histopathology score each varied markedly between normal-sample and degenerate-sample groups but varied relatively little between normal samples obtained from different age groups. A decrease in indentation stiffness (softening) correlated with a decrease in the reflectance score and an increase in the overall histopathology score, especially the surface irregularity component of the histopathology score. Receiver operating characteristic analysis suggested that the indentation testing could accurately detect cartilage degeneration as indicated by macroscopic appearance, India ink staining, and histopathology score. The indentation stiffness of the normal to mildly degenerate samples tested in this study was sensitive to mild degeneration at the articular surface and was insensitive to changes associated with normal aging or to slight variations in cartilage thickness. This suggests that indentation testing may be a useful clinical tool for the evaluation of early-stage degenerative changes in articular cartilage.

Depth-dependent confined compression modulus of full-thickness bovine articular cartilage.

The objective of this study was to determine the equilibrium confined compression modulus of bovine articular cartilage as it varies with depth from the articular surface. Osteochondral samples were compressed by 8, 16, 24, and 32% of the cartilage thickness and allowed to equilibrate. Intratissue displacement within the cartilage was measured with use of fluorescently labeled chondrocyte nuclei as intrinsic, fiducial markers. Axial strain was then calculated in nine sequential 125 microns thick cartilage layers comprising the superficial 1,125 microns and in a 250 microns thick layer of cartilage adjacent to the cartilage-bone interface. Adjacent osteochondral cores were also tested in confined compression to determine the equilibrium stresses required to achieve the same levels of compression. Stress-strain data for each layer of each sample were fit to a finite deformation stress-strain relation to determine the equilibrium confined compression modulus in each tissue layer. The compressive modulus increased significantly with depth from the articular surface and ranged from 0.079 +/- 0.039 MPa in the superficial layer to 1.14 +/- 0.44 MPa in the ninth layer. The deepest layer 250 microns thick, had a modulus of 2.10 +/- 2.69 MPa. These moduli were markedly different from the apparent "homogeneous" modulus for full-thickness cartilage (0.38 +/- 0.12 MPa) and ranged from 21 to 560% of that value. The relatively low moduli and the compression-induced stiffening of the superficial layers suggest that these layers greatly affect the biomechanical behavior of cartilage, such as during confined compression testing. The delineation of the depth-dependent modulus provides a basis for detailed study of the relationship between the composition, structure, and function of cartilage in such processes as aging, repair, and degeneration.