Partial-thickness Cartilage Defects Research Articles

Evaluation of the Articular Cartilage of the Knee Joint: Value of Adding a T2 Mapping Sequence to a Routine MR Imaging Protocol

To determine whether the addition of a T2 mapping sequence to a routine magnetic resonance (MR) imaging protocol could improve diagnostic performance in the detection of surgically confirmed cartilage lesions within the knee joint at 3.0 T. This prospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. The study group consisted of 150 patients (76 male and 74 female patients with an average age of 41.2 and 41.5 years, respectively) who underwent MR imaging and arthroscopy of the knee joint. MR imaging was performed at 3.0 T by using a routine protocol with the addition of a sagittal T2 mapping sequence. Images from all MR examinations were reviewed in consensus by two radiologists before surgery to determine the presence or absence of cartilage lesions on each articular surface, first by using the routine MR protocol alone and then by using the routine MR protocol with T2 maps. Each articular surface was then evaluated at arthroscopy. Generalized estimating equation models were used to compare the sensitivity and specificity of the routine MR imaging protocol with and without T2 maps in the detection of surgically confirmed cartilage lesions. The sensitivity and specificity in the detection of 351 cartilage lesions were 74.6% and 97.8%, respectively, for the routine MR protocol alone and 88.9% and 93.1% for the routine MR protocol with T2 maps. Differences in sensitivity and specificity were statistically significant (P < .001). The addition of T2 maps to the routine MR imaging protocol significantly improved the sensitivity in the detection of 24 areas of cartilage softening (from 4.2% to 62%, P < .001), 41 areas of cartilage fibrillation (from 20% to 66%, P < .001), and 96 superficial partial-thickness cartilage defects (from 71% to 88%, P = .004). The addition of a T2 mapping sequence to a routine MR protocol at 3.0 T improved sensitivity in the detection of cartilage lesions within the knee joint from 74.6% to 88.9%, with only a small reduction in specificity. The greatest improvement in sensitivity with use of the T2 maps was in the identification of early cartilage degeneration.

The use of type 1 collagen scaffold containing stromal cell-derived factor-1 to create a matrix environment conducive to partial-thickness cartilage defects repair

Despite the presence of cartilage-derived mesenchymal stem cells (C-MSCs) and synovial membrane-derived mesenchymal stem cells (SM-MSCs) populations, partial-thickness cartilage defects, in contrast to the full-thickness defects, are devoid of spontaneous repair capacity. This study aims to create an in situ matrix environment conducive to C-MSCs and SM-MSCs to promote cartilage self-repair. Spontaneous repair with MSCs migration into the defect area was observed in full-thickness defects, but not in partial-thickness defects in rabbit model. Ex vivo and in vitro studies showed that subchondral bone or type 1 collagen (col1) scaffold was more permissive for MSCs adhesion than cartilage or type 2 collagen (col2) scaffold and induced robust stromal cell-derived factors-1 (SDF-1) dependent migration of MSCs. Furthermore, creating a matrix environment with col1 scaffold containing SDF-1 enhanced in situ self-repair of partial-thickness defects in rabbit 6 weeks post-injury. Hence, the inferior self-repair capacity in partial-thickness defects is partially owing to the non-permissive matrix environment. Creating an in situ matrix environment conducive to C-MSCs and SM-MSCs migration and adhesion with col1 scaffold containing SDF-1 can be exploited to improve self-repair capacity of cartilage.

Paper 265: The Intra-articular Location of a Cartilage Defect Influences the Natural History of Cartilage Filling

To investigate the difference in natural history cartilage filling related to the intra-articular location of an experimental induced cartilage defect in the rabbit knee. A partial thickness cartilage defect (? = 4 mm) was induced in both knees of 35 adult New Zealand rabbits at the age of 22 weeks. The animals were randomized to having the defect induced in the patella in either the right or left knee, whereas the other knee had the defect induced in the medial-femur-condyle (MFC). An operating microscope was used to secure the preparation of the defects. The animals were sacrificed at 12 weeks (n=8), 24 weeks (n=9), and 36 weeks (n=18) after surgery. Analysis® software was used in measuring the cartilage height at 7 determined spots in each defect. Cartilage filling was estimated relating the mean cartilage height in each defect to the mean cartilage height of the shoulders of the same defect. Statistical analyses were performed using paired T-test. Twelve weeks after surgery the cartilage filling of patella defects were 32.3%, compared to 16.9% in MFC defects (p<0.05). Twenty-four weeks after surgery the filling of patella defects were 25.0% compared to 8.0% in MFC defects (p<0.05). Thirty-six weeks after surgery the filling of patella defects were 48.8% compared to 20.5% in MFC defects (p<0.05). There was a significant rise in cartilage filling from 24 to 36 weeks post surgery at both locations. The intra-articular location of a partial thickness cartilage defect influences the natural history of cartilage filling of the defect.

Composite System of PLCL Scaffold and Heparin-Based Hydrogel for Regeneration of Partial-Thickness Cartilage Defects

Delivering isolated chondrocytes with matrix is a promising approach to promote the cartilage repair. The present study attempted to combine the advantages of porous scaffold and hydrogel in delivering chondrocytes to partial-thickness cartilage defects. An electrospun, gelatin-incorporated PLCL scaffold mechanically similar to natural cartilage was fabricated, and chondrocytes were seeded using an injectable heparin-based hydrogel for efficient cell seeding. The scaffold/hydrogel composite showed more enhanced expression of chondrogenic genes and production of GAGs than those prepared without hydrogel. In addition, significant cartilage formation showing good integration with surrounding, similar to natural cartilage, was observed by scaffold/hydrogel composite system in partial-thickness defects of rabbit knees while no regeneration was observed in control defects. Although no exogenous chondrogenic factors were added, it was evident that the scaffold/hydrogel composite system was highly effective and better than the scaffold alone system without hydrogel for cartilage regeneration both in vitro and in vivo.

Preliminary Study of 1.5-T MR Arthrography of the Shoulder With 3D Isotropic Intermediate-Weighted Turbo Spin Echo

The purpose of this study was to assess the performance of a near-isotropic 3D turbo spin-echo sequence in comparison with a standard 2D protocol and with arthroscopy in direct 1.5-T MR arthrography of the shoulder. Dilute gadolinium was injected into three cadaver shoulders, and 3D turbo spin-echo and 2D sequences were evaluated with respect to the signal-to-noise and contrast-to-noise ratios of key tissues. In a prospective study, the 3D intermediate-weighted fat-suppressed sequence (reformatted in three planes) was added to shoulder MR arthrography of 43 consecutively registered patients, 13 of whom later underwent arthroscopy. Two radiologists independently graded the 3D and 2D images in separate sessions to visualize normal anatomic features and to detect pathologic changes in the labrum, cartilage, cuff, and glenohumeral ligaments, assigning confidence levels to their readings. One reader repeated the readings of images of 10 patients. Reports of subsequent arthroscopy were available for 13 patients. The sequences performed comparably with respect to signal-to-noise and contrast-to-noise ratios in the cadavers. The 3D images suffered from mildly increased blurring, but the readers were significantly more confident in assessing the proximal biceps tendon and curved portions of the labrum and in their findings of partial tears of the articular side of the supraspinatus tendon and posterior labral tears on the 3D images. A larger number of partial-thickness cartilage defects were found on 2D images. The 3D turbo spin-echo sequence is a promising technique that can be used in shoulder arthrography with image quality and results comparable to those of traditional 2D techniques. Use of the 3D technique may result in greater anatomic detail in evaluating small obliquely oriented structures, including the curved portions of the labrum and the intraarticular portion of the biceps tendon.

Maturation-dependent spontaneous healing of partial thickness cartilage defects in infantile rats

Partial-thickness articular cartilage defects (PTCDs) do not heal spontaneously and are thought to be a predisposing factor for the development of osteoarthritis. Younger and smaller animals have a better healing capacity for many types of injuries including those to articular cartilage. Our aim was to examine the longitudinal histological changes of immature murine articular cartilage after the creation of small PTCDs and to compare them to PTCDs in mature cartilage. Single linear PTCDs were created in 3-week-old and 16-week-old rats in the direction of joint motion. At 6 and 12weeks after PTCD creation, histological changes were examined in the defect sites and surrounding cartilage. Immature cartilage showed a higher repair capability than mature cartilage. Although repaired immature cartilage had fibrocartilage, it exhibited better quality than any PTCD model, except for a fetus model and comparable quality to full-thickness cartilage defects (FTCD) after bone marrow stimulation. Elucidation of the underlining mechanisms that immature cartilage possesses for repairing PTCDs is necessary in order to aid the prevention or develop treatment for osteoarthritis.

The use of de-differentiated chondrocytes delivered by a heparin-based hydrogel to regenerate cartilage in partial-thickness defects

Partial-thickness cartilage defects, with no subchondral bone injury, do not repair spontaneously, thus there is no clinically effective treatment for these lesions. Although the autologous chondrocyte transplantation (ACT) is one of the promising approaches for cartilage repair, it requires in vitro cell expansion to get sufficient cells, but chondrocytes lose their chondrogenic phenotype during expansion by monolayer culture, leading to de-differentiation. In this study, a heparin-based hydrogel was evaluated and optimized to induce cartilage regeneration with de-differentiated chondrocytes. First, re-differentiation of de-differentiated chondrocytes encapsulated in heparin-based hydrogels was characterized in vitro with various polymer concentrations (from 3 to 20 wt.%). Even under a normal cell culture condition (no growth factors or chondrogenic components), efficient re-differentiation of cells was observed with the optimum at 10 wt.% hydrogel, showing the complete re-differentiation within a week. Efficient re-differentiation and cartilage formation of de-differentiated cell/hydrogel construct were also confirmed in vivo by subcutaneous implantation on the back of nude mice. Finally, excellent cartilage regeneration and good integration with surrounding, similar to natural cartilage, was also observed by delivering de-differentiated chondrocytes using the heparin-based hydrogel in partial-thickness defects of rabbit knees whereas no healing was observed for the control defects. These results demonstrate that the heparin-based hydrogel is very efficient for re-differentiation of expanded chondrocytes and cartilage regeneration without using any exogenous inducing factors, thus it could serve as an injectable cell-carrier and scaffold for cartilage repair. Excellent chondrogenic nature of the heparin-based hydrogel might be associated with the hydrogel characteristic that can secure endogenous growth factors secreted from chondrocytes, which then can promote the chondrogenesis, as suggested by the detection of TGF- β1 in both in vitro and in vivo cell/hydrogel constructs.

Posteromedial Elbow Impingement: MRI Findings in Overhead Throwing Athletes and Results of Arthroscopic Treatment (SS-26)

Posteromedial elbow pain as a result of impingement has a reproducible pattern of pathology on MRI in throwing athletes. Arthroscopic debridement, olecranon spur excision, and loose body excision if present allows return to throwing sports, and excellent subjective and objective results. Posteromedial elbow pain in throwing athletes may be the result of valgus extension overlead and UCL insufficiency or due to posteromedial impingement due synovitis or olecranon spurring. An MRI with or without intra-articular contrast is the gold standard imaging modality. To date, no pattern of MRI findings has been reported in the setting of clinical posteromedial elbow impingement. The purpose of this study was to define the MRI pattern and assess the results of arthroscopic treatment. Over an 8 year period, a total of 10 throwing athletes were identified retrospectively, who were diagnosed with posteromedial elbow impingement who had an MRI, and who failed non-operative treatment and ultimately required arthroscopy. Any patients with UCL insufficiency were excluded from the study. Those with a clinical diagnosis of posteromedial elbow impingement underwent an MRI examination using either a standard noncontrast protocol, or a direct MR arthrographic protocol. All MRIs were acquired at 1.5 tesla using a dedicated extremity receiver coil with the patient's affected arm extended while prone on the scanner in a ‘superman' position. All studies included edema sensitive T2 weighted fast spin echo fat suppressed sequences in 3 planes, while the direct MR arthrographic studies included high resolution T1 weighted spin echo fat suppressed images in at least two planes. MRIs were reviewed by a fellowship trained musculoskeletal radiologist blinded to clinical history other than age and gender. Arthroscopic treatment included debridement of posteromedial synovitis, loose body (if present) excision, and excision of any olecranon spur. All patients underwent a physical examination and completion of the Andrews-Carson scale with a minimum follow-up of 12 months (range: 12 - 73). All patients were male with an average age of 21.2 (range: 15 - 34). The dominant arm (right = 9) was affected in all patients. The average length of symptoms prior to surgery was 9 months (range: 5 - 24). At MRI, a reproducible pattern of pathology was noted. All patients had pathology recorded at the articular surfaces of the posterior trochlea and the anterior, medial olecranon, ranging from abnormal edema like signal in the hyaline cartilage (grade 1 chondrosis) to partial thickness cartilage defects and subjacent, subchondral bone marrow edema (grade 2 or 3 chondrosis). Additional MRI findings included joint effusion, synovitis within the posteromedial recess, marginal osteophytes at the trochlea and olecranon, soft tissue edema about the distal, medial triceps insertion, ulnar collateral ligament hypertrophy, and flexor/pronator tendon origin strain. Findings at surgery included posteromedial synovitis and olecranon spurring in all patients, and loose bodies in 3 patients. Based on the Andrews-Carson scale, the subjective and objective outcome was considered excellent in 8 patients and good in 2. Posteromedial elbow pain as a result of impingement has a reproducible pattern of pathology on MRI in throwing athletes. Arthroscopic debridement, olecranon spur excision, and loose body excision if present allows return to throwing sports, and excellent subjective and objective results.

Cell‐based resurfacing of large cartilage defects: Long‐term evaluation of grafts from autologous transgene‐activated periosteal cells in a porcine model of osteoarthritis

To investigate the potential of transgene-activated periosteal cells for permanently resurfacing large partial-thickness cartilage defects. In miniature pigs, autologous periosteal cells stimulated ex vivo by bone morphogenetic protein 2 gene transfer, using liposomes or a combination of adeno-associated virus (AAV) and adenovirus (Ad) vectors, were applied on a bioresorbable scaffold to chondral lesions comprising the entire medial half of the patella. The resulting repair tissue was assessed, 6 and 26 weeks after transplantation, by histochemical and immunohistochemical methods. The biomechanical properties of the repair tissue were characterized by nanoindentation measurements. Implants of unstimulated cells and untreated lesions served as controls. All grafts showed satisfactory integration into the preexisting cartilage. Six weeks after transplantation, AAV/Ad-stimulated periosteal cells had adopted a chondrocyte-like phenotype in all layers; the newly formed matrix was rich in proteoglycans and type II collagen, and its contact stiffness was close to that of healthy hyaline cartilage. Unstimulated periosteal cells and cells activated by liposomal gene transfer formed only fibrocartilaginous repair tissue with minor contact stiffness. However, within 6 months following transplantation, the AAV/Ad-stimulated cells in the superficial zone tended to dedifferentiate, as indicated by a switch from type II to type I collagen synthesis and reduced contact stiffness. In deeper zones, these cells retained their chondrocytic phenotype, coinciding with positive staining for type II collagen in the matrix. Large partial-thickness cartilage defects can be resurfaced efficiently with hyaline-like cartilage formed by transgene-activated periosteal cells. The long-term stability of the cartilage seems to depend on physicobiochemical factors that are active only in deeper zones of the cartilaginous tissue.

Development of Partial-thickness Articular Cartilage Injury in a Rabbit Model

In humans, partial-thickness cartilage lesions frequently result in premature osteoarthritis. While rabbits often are used as a model for partial-thickness cartilage lesions, the natural course of cartilage surrounding such a lesion is largely unknown. We developed a rabbit model of a chronic partial-thickness cartilage defect and asked whether these defects led to (1) deterioration of surrounding cartilage macroscopically and microscopically (increased Mankin score) and (2) disturbances in proteoglycan metabolism. In 55 rabbits, we created a 4-mm-diameter partial-thickness cartilage defect on one medial femoral condyle. The surrounding cartilage was characterized during the course of 26 weeks. Contralateral knees were sham-operated. In experimental knees, we found cartilage softening and fibrillation at 13 and 26 weeks. High Mankin scores observed at 1 week were partially restored at 13 weeks but worsened later and were most pronounced at 26 weeks. Mankin scores in the experimental groups were worse at 1 and 26 weeks when compared with the sham groups. Mankin scores at 26 weeks improved compared with 1 week in the sham groups. Disturbances in proteoglycan metabolism were less evident. In this rabbit model, a partial-thickness cartilage lesion resulted in early markers of degenerative changes resembling the human situation.

Injectable Mesenchymal Stem Cell Therapy for Large Cartilage Defects—A Porcine Model

Current techniques in biological resurfacing of cartilage defects require an open arthrotomy or arthroscopy and involve the direct transplantation of isolated cells and/or scaffolds or whole tissue grafts with chondrogenic potential onto the cartilage defect. Our study investigates the possibility of direct intra-articular injection of mesenchymal stem cells suspended in hyaluronic acid (HA) as an alternative to the much more invasive methods currently available. A partial-thickness (without penetration of the subchondral bone) cartilage defect was created in the medial femoral condyle of an adult minipig. Mesenchymal stem cells from the iliac crest marrow of the same pig harvested in a separate procedure and suspended in 2 milliliters of hylan G-F 20 (Synvisc) were injected intra-articularly after the creation of the defect. This was followed by two more injections of hylan G-F 20 (HA) at weekly intervals. Either saline or HA was injected into the knees of the controls. The pigs were sacrificed at 6 and 12 weeks for morphological and histological analysis. The cell-treated groups showed improved cartilage healing both histologically and morphologically at 6 and 12 weeks compared with both controls. The use of intra-articular injections of mesenchymal stem cells suspended in HA is a viable option for treating large cartilage defects. This would be further explored in clinical trials.

Mechanical properties of hyaline and repair cartilage studied by nanoindentation

Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies.

Cultured articular chondrocytes sheets for partial thickness cartilage defects utilizing temperature-responsive culture dishes

The extracellular matrix (ECM) of articular cartilage has several functions that are unique to joints. Although a technique for transplanting cultured chondrocytes has already been introduced, it is difficult to collect intact ECM when using enzymes to harvest samples. Temperature-responsive culture dishes have already been clinically applied in the fields of myocardial and corneal transplantation. Earlier studies have shown that a sheet of cultured cells with intact ECM and adhesive factors can be harvested using such culture dishes, which allow the surface properties of the dish to be reversibly altered by changing the temperature. Human chondrocytes were subjected to enzymatic digestion and then were seeded in temperature-responsive culture dishes. A sheet of chondrocytes was harvested by only reducing the temperature after the cultured cells reached confluency. A real-time PCR analysis of the chondrocyte sheets confirmed that type II collagen, aggrecan, and fibronectin were present. These results suggested that, although chondrocytes undergo dedifferentiation in a monolayer culture, multilayer chondrocyte sheets grown in a similar environment to that of three-dimensional culture may be able to maintain a normal phenotype. A histological examination suggested that multilayer chondrocyte sheets could thus prevent the loss of proteoglycans because the area covered by the sheets was well stained by safranin-O. The present experiments suggested that temperature-responsive culture dishes are useful for obtaining cultured chondrocytes, which may then be clinically employed as a substitute for periosteal patches because such sheets can be applied without a scaffold.

P234 The intra-articular location of a partial thickness cartilage defect influences the natural history of cartilage filling of the defect

P234 The intra-articular location of a partial thickness cartilage defect influences the natural history of cartilage filling of the defect

Partial-Thickness Articular Cartilage Defects: Evaluation and Treatment

Existing scientific publications regarding evaluation and treatment of partial-thickness articular cartilage defects report conflicting results. Magnetic resonance imaging is an excellent diagnostic evaluation tool. In the community setting, however, using magnetic resonance imaging to evaluate partial-thickness cartilage defects may have variable or low sensitivity and specificity. Today, diagnostic arthroscopy with visual inspection and probing of the entire articular surface may be the gold standard for diagnostic evaluation of partial-thickness cartilage lesions. However, before surgery, nonsurgical treatment is recommended based on the presumptive diagnosis. Mechanical debridement and lavage using a suction oscillating shaver (chondroplasty) is the accepted surgical treatment of choice. However, reported outcomes of mechanical chondroplasty are not so good as might be expected, and basic and clinical research suggests that thermal chondroplasty using radiofrequency energy may prove superior in the future. In addition, basic research suggests that treatments using growth factors may, in the future, expand management options.

Mechanical and Biochemical Effect of Monopolar Radiofrequency Energy on Human Articular Cartilage

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.

MRI of articular cartilage in OA: novel pulse sequences and compositional/functional markers

Osteoarthritis (OA) is a leading cause of disability worldwide. Magnetic resonance imaging (MRI), with its unique ability to image and characterize soft tissue non-invasively, has proven valuable in assessing cartilage in OA. The development of new, fast imaging methods with high contrast show promise to improve the magnetic resonance (MR) evaluation of this disease. In addition to morphologic MRI methods, MRI contrast mechanisms under development may reveal detailed information about the physiology of cartilage. It is anticipated that these and other MRI techniques will play an increasingly important role in assessing the success or failure of therapies for OA. On December 5 and 6, 2002, OMERACT (Outcome Measures in Rheumatology Clinical Trials) and OARSI (Osteoarthritis Research Society International) held a workshop in Bethesda, MD aiming at providing a state-of-the-art review of imaging outcome measures for OA of the knee to help guide scientists and pharmaceutical companies in the use of MRI in multi-site studies of OA. Applications of MRI were initially reviewed by a multidisciplinary, international panel of expert scientists and physicians from academia, the pharmaceutical industry and regulatory agencies. The findings of the panel were then presented to a wider group of participants for open discussion. The following report summarizes the results of these discussions with respect to novel MRI pulse sequences for evaluating articular cartilage of the knee in OA and notes any additional advances that have been made since.

Monopolar Radiofrequency Treatment of Partial-Thickness Cartilage Defects in the Sheep Knee Joint Leads to Extended Cartilage Injury

Background The application of radiofrequency energy to smooth and stabilize the cartilage surface has become increasingly controversial. There is little knowledge on extended-term effects, such as cartilage viability. Purpose To analyze the effect of radiofrequency treatment on artificially created partial-thickness defects in the femoral cartilage of sheep knee joints 24 weeks after surgery. Study Design Controlled laboratory study. Methods Grade II cartilage surface defects on the medial and lateral femoral condyles were artificially created in sheep for in vivo analysis. The cartilage lesions were treated alternately on the lateral or the medial condyle using a monopolar radiofrequency probe. Radiofrequency treatment was performed in a freehand technique until surface smoothing without change of cartilage color was seen. At 24 weeks after surgery, cartilage samples were harvested and were processed for macroscopic and histological evaluation. To analyze the effect of radiofrequency at time zero, samples of sheep femoral condyle cartilage with and without artificially created clefts were treated in vitro with radiofrequency. Evaluation was performed by scanning electron and confocal microscopy. Results At 24 weeks after surgery, grade IV cartilage defects were detected in all radiofrequency-treated samples. The histological findings showed a central ulcer and dead chondrocytes in the radiofrequency-treated regions. The radiofrequency-treated cartilage revealed partial surface irregularities with partial-defect repair. After radiofrequency treatment in vitro, samples at time zero showed smoothing of the artificially created clefts, as seen by scanning electron microscopy. Confocal microscopy showed necrosis of chondrocytes over approximately one fourth of the upper cartilage thickness. Conclusion Even if chondrocyte death is seen only in approximately one fourth of the upper cartilage layers in the sheep femur after in vitro application, radiofrequency treatment can cause damage to cartilage 24 weeks after application. Clinical Relevance Caution is recommended in the application of monopolar radiofrequency energy by visual control to partialthickness cartilage defects. Irregular fronds of chondromalacia may be unattractive but represent viable articular cartilage. Using radiofrequency to obtain a more visually pleasing smooth surface may be counterproductive.

Reparative and degenerative changes in surgically induced articular cartilage defects in the horse during the early post-operative period

Summary This study evaluated early changes in full-thickness (FT) and partial-thickness (PT) articular cartilage defects created by arthroscopic surgery. The defects were of various configurations in a model (horse) that was weight-bearing immediately after surgery. The objectives were to evaluate recellularization and to examine the effect defect configuration had on adjacent cartilage cellularity and proteoglycan content. Thirty-six PT lacerations, FT lacerations, PT scrapes, PT craters, and FT craters were created in the antebrachiocarpal and intercarpal joints of eight adult horses. The configurations were lacerations by knife blade, scrapes by a curette, and craters created by motorized burr. Horses were euthanized one, three, and eight weeks after surgery. Histologic examination was performed using hematoxylin and eosin and safranin-O staining. All FT craters showed evidence of early repair. None of the lacerations showed evidence of early repair. One PT scrape and four PT craters bad fibrous tissue within the defect. All defects had degenerative changes in adjacent cartilage. Craters and scrapes had significantly worse degenerative changes than lacerations. Patients undergoing arthroscopic surgery who will be weight-bearing immediately after surgery should have full thickness crateriform debridement if a healing response is desired. Partial thickness debridement does not show evidence of repair. Degenerative changes in adjacent cartilage occurred in all defects and they are directly proportional to the amount of trauma and instrumentation used at surgery. Full thickness (FT) cartilage defects that penetrate the zone of calcified cartilage rely on hemorrhage from subchondral bone and the resultant fibrin clot to initiate repair. The fibrin clot acts as a matrix for cellular repair that results in formation of fibrous tissue. The quality of repair (i.e. fibrous tissue, fibrocartilage, or hyaline cartilage) relies on metaplasia of fibrous tissue. This mechanism of articular cartilage healing, referred to as extrinsic repair 1,2 occurs after subchondral abrasion with motorized instrumentation; 3,4,5 however, the quality and durability of repair tissue has been questioned. 5,6,7 Partial thickness (PT) cartilage defects do not penetrate the zone of calcified cartilage and do not bleed. Healing of PT defects relies on mitotic activity of chondrocytes and increased metabolic activity adjacent to the defect to create intrinsic repair. 2 Many investigators have shown the inability of PT defects to heal. 3,8,9,10,18 It has recently been shown that PT defects may undergo further degeneration. 3 The fibrin clot and other extrinsic factors released during hemorrhage in FT defects are reported to be important in initiating repair of articular cartilage. 5 Mesenchymal cells from the subchondral bone initiate the recellularization process in FT defects. 11,12,13 If PT defects are to heal with any degree of consistency then a “modified” extrinsic repair must occur or blood clot must attach to the defect and recellularization from synovial cells within the joint must take place. Early reparative changes in articular cartilage of other species have been documented. Most studies investigating articular cartilage healing in the horse are long-term studies evaluating the quality and durability of repair tissue. The purpose of this study was to investigate early recellularization of FT and PT defects created by arthroscopic surgery in articular cartilage located within the same joint surface in a model in which the operated horse was weight-bearing immediately after surgery. The objectives were to evaluate early recellularization and to examine the effect various types of defects had on adjacent cartilage cellularity and proteoglycan content at one, three, and eight weeks after surgery.

The effect of low-level Nd:YAG laser energy on adult articular cartilage in vitro

Reports of laser energy applied to soft tissues in vitro and in vivo suggest both stimulation and inhibition of specific metabolic processes, depending on the type of laser, the energy density (ED) used, the mode of delivery, and type of tissue studied. An earlier in vitro study of Nd:YAG laser irradiation of articular cartilage indicated stimulation of both matrix and DNA synthesis for 6 days following laser exposure. In vivo reports on the ability of Nd:YAG laser energy to stimulate the healing of partial-thickness cartilage defects are conflicting. In the present study, a noncontact continuous-wave Nd:YAG laser beam of varying EDs was applied to full-thickness adult articular cartilage explants maintained in organ culture; the metabolic processes of chondrocyte DNA synthesis and matrix synthesis were followed over 2 weeks. For both canine and bovine cartilage, low-levels of laser energy (ED 51–127 J/cm 2) stimulated matrix synthesis at 6–7 days following laser exposure, with a concomitant decrease in baseline DNA synthesis. By 12–14 days, however, these dose-dependent effects were no longer seen, with no significant differences from control noted for any of the laser energies studied. Histologic analysis of the cartilage explants following laser exposure showed no significant differences in cell number or morphology between sample and control groups; however, a decrease in matrix proteoglycan staining was seen in the highest laser energy group at all time points. These findings indicate that exposure to low-level noncontact Nd:YAG laser energy promotes a significant stimulation of cartilage matrix synthesis. However, a single exposure may not be sufficient to promote a sustained upregulation of cartilage metabolism. Based on the findings of this study, the potential for stimulating cartilage metabolism and repair via noncontact Nd:YAG laser energy applied arthroscopically warrants further study.