Arthroscopic subchondral bone plate microfracture technique augments healing of large chondral defects in the radial carpal bone and medial femoral condyle of horses

Return to athletic activity after osteochondral allograft transplantation in the knee

BACKGROUND

Fresh-stored osteochondral allografts have been used successfully to resurface large chondral and osteochondral defects of the knee. However, there are limited data available for the return to athletic activity.

PURPOSE

To review the rate of return to athletic activity after osteochondral allograft transplantation in the knee and to identify any potential risk factors for not returning to sport.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Forty-three athletes were treated with fresh-stored osteochondral allograft transplantation for symptomatic large chondral or osteochondral defects of the knee from 2000 to 2010. The average age of the athletes (30 men, 13 women) was 32.9 years (range, 18-49 years). Patients were prospectively evaluated by International Knee Documentation Committee (IKDC), activities of daily living scale of the Knee Injury and Osteoarthritis Outcome Score (KOOS), Marx Activity Rating Scale, and Cincinnati Sports Activity Scale scores. A multivariable regression analysis was performed to identify potential risk factors for failure to return to sport at the preinjury level.

RESULTS

At an average 2.5-year follow-up, limited return to sport was possible in 38 of 43 athletes (88%), with full return to the preinjury level achieved in 34 of 43 athletes (79%). In these 34 athletes, time to return to sport was 9.6 ± 3.0 months. Age ≥25 years (P = .04) and preoperative duration of symptoms greater than 12 months (odds ratio, 37; P = .003) negatively affected the ability to return to sport. In the athletes who returned to their previous level of competition, IKDC (P < .001), KOOS (P = .02), and Marx Activity Rating Scale (P < .001) scores were all significantly greater than in those athletes who did not return to sport.

CONCLUSION

Osteochondral allograft transplantation in an athletic population for chondral and osteochondral defects in the knee allows for a high rate of return to sport. Risk factors for not returning to sport included age ≥25 years and preoperative duration of symptoms ≥12 months.

A functional agarose-hydroxyapatite scaffold for osteochondral interface regeneration

Regeneration of the osteochondral interface is critical for integrative and functional cartilage repair. This study focuses on the design and optimization of a hydrogel-ceramic composite scaffold of agarose and hydroxyapatite (HA) for calcified cartilage formation. The first study objective was to compare the effects of HA on non-hypertrophic and hypertrophic chondrocytes cultured in the composite scaffold. Specifically, cell growth, biosynthesis, hypertrophy, and scaffold mechanical properties were evaluated. Next, the ceramic phase of the scaffold was optimized in terms of particle size (200 nm vs. 25 μm) and dose (0-6 w/v%). It was observed that while deep zone chondrocyte (DZC) biosynthesis and hypertrophy remained unaffected, hypertrophic chondrocytes measured higher matrix deposition and mineralization potential with the addition of HA. Most importantly, higher matrix content translated into significant increases in both compressive and shear mechanical properties. While cell hypertrophy was independent of ceramic size, matrix deposition was higher only with the addition of micron-sized ceramic particles. In addition, the highest matrix content, mechanical properties and mineralization potential were found in scaffolds with 3% micro-HA, which approximates both the mineral aggregate size and content of the native interface. These results demonstrate that the biomimetic hydrogel-ceramic composite is optimal for calcified cartilage formation and is a promising design strategy for osteochondral interface regeneration.

Osteochondral mosaicplasty of the femoral head

Young adults with osteochondral lesions of the femoral head are at risk of rapid progression to symptomatic arthritis of the hip joint. Between January 2008 and July 2009, 10 patients were treated for femoral cartilage damage by a osteochondral mosaicplasty of the femoral head through a trochanteric flap with dislocation of the hip. The consecutive series had the following exclusion criteria: acetabular chondropathy, age above 25 years, and femoral head osteonecrosis. Patients were followed up after surgery using the Oxford-12 score, Harris hip score and the Merle d'Aubigné score, and activity assessed by the UCLA and Devane scores. Radiological evaluation by computed tomographic (CT) arthrography was undertaken in all patients at 6 months and plain radiographs. Mean follow-up was 29.2 months (20-39 months). The Postel Merle d'Aubigné score improved from the pre-operative period to the latest follow-up, from 10.5 points (8-13) to 15.5 points (12-17). Global range of motion increased from 175.4° (140-215) to 210.7° (175-240). All radiological investigations at latest follow-up showed that the autograft plugs were well-incorporated at the site of osteochondroplasty in the femoral head with intact cartilage over them and smooth interfaces between articulating bony surfaces. Osteochondral autograft transplantation may be a new alternative option for osteochondral lesions of the femoral head, but this has to be confirmed with longer follow-up and in a larger number of patients. The results of similar surgery in the knee have been mixed, and in the hip the technique is demanding, requiring familiarity with surgical hip dislocation.

Cartilage repair in the rabbit knee: mosaic plasty resulted in higher degree of tissue filling but affected subchondral bone more than microfracture technique: a blinded, randomized, controlled, long-term follow-up trial in 88 knees

PURPOSE

Discrepancies and variances in outcome following different surgical techniques for cartilage repair are poorly understood. Successful repair relies on proper tissue filling without initiating degenerative processes in the cartilage-bone unit. Consequently, the objective of the current study was to compare two available techniques for cartilage repair, i.e., microfracture technique and mosaic plasty, regarding tissue filling and subchondral bone changes in an experimental model.

METHODS

A 4-mm pure chondral defect was created in the medial femoral condyle of both knees in New Zealand rabbits, aged 22 weeks. A stereomicroscope was used to optimize the preparation of the defects. In one knee (randomized), the defect was treated with microfracture technique whereas in the other with mosaic plasty. The animals were killed at 12, 24 and 36 weeks after surgery. Defect filling, new bone formation above the level of the tidemark and the density of subchondral mineralized tissue were estimated by histomorphometry.

RESULTS

Mosaic plasty resulted in a significantly 34% higher degree of tissue filling than microfracture technique at 36 weeks, SD of mean difference being 34%. Mosaic plasty resulted in significantly more new bone formation and reduced subchondral mineralized tissue density compared to microfracture technique. The differences between the two techniques were apparent mainly at the long-term follow-up.

CONCLUSION

Tissue filling is a limiting factor regarding microfracture technique when compared to mosaic plasty, whereas mosaic plasty resulted in more bone changes than microfracture technique-the implications of the latter remain to be settled. This study underlines the difficulty in predicting outcome in the single case with any of these two techniques, particularly in a long-term perspective.

A review of the treatment methods for cartilage defects

The purpose of this article is to provide a broad review of the literature related to the treatment of cartilage defects and degenerated cartilage in animals with some inferences to the treatment in humans. Methods range from the insertion of osteochondral tissue or cells to the application of radio frequency or insertion of scaffolds and growth factors alone or in combination. Debridement, microfracture, radio frequency, and chondrocyte implantation are all methods normally utilized when treating smaller articular cartilage defects. Scaffolds and mosaicplasty are examples of methods to treat larger defects. This review will cover all major treatment methods currently used to treat articular cartilage defects.

Microfracture in Football (Soccer) Players: A Case Series of Professional Athletes and Systematic Review

BACKGROUND

Little information is available on the results of microfracture in competitive football (soccer) players. We aimed to evaluate the efficacy of this technique to restore joint function to a level that allows return to this popular high-impact sport.

METHODS

This article provides an overview of the basic science and the current published scientific evidence for articular cartilage repair using the microfracture technique in elite football (soccer) athletes. In addition, the senior author documents his results in a case series of professional football (soccer) players treated with microfracture.

RESULTS

Twenty-one professional male soccer players underwent microfracture for knee articular cartilage defects. Nineteen players had isolated cartilage injuries, and 2 players had simultaneous anterior cruciate ligament injuries. Average age of the player was 27 years (range, 18-32 years). Twelve players (57%) had single defects, and 9 (43%) had multiple defects. All players complied with the postoperative rehabilitation program. Twenty players (95%) returned to professional soccer the season following microfracture surgery and continued to play for an average of 5 years (range, 1-13 years). Years of continued play inversely correlated with player age at the time of microfracture (r = -0.41).

CONCLUSION

Articular cartilage repair with the microfracture technique followed by appropriate rehabilitation provides restoration of knee joint function in professional football (soccer) players with a high rate of return to football (soccer) and continued participation under the significant demands of professional football (soccer). Thorough understanding of the technical aspects, rehabilitation, and literature can help to optimize the results of microfracture in the athletic population.

The manangement of knee cartilage defects with modified amic technique: preliminary results

Cartilage defects represent a common problem in orthopaedic practice. The knee is frequently involved and the medial femoral condyle is the most common localization. Predisposing factors are: traumas, inflammatory conditions and biomechanics alterations. Several surgical options are available once correct diagnosis is given and accurate patient evaluation has been performed. The aim of our study was to prospectively evaluate functional results of modified autologous matrix induced chondrogenesis (AMIC) technique in a population of patients affected by focal cartilage defects A population of 17 patients was enrolled in this study. 10 patients were male, mean age at the time of surgery was 39 years, right side was involved in 11 cases. All patients were evaluated with accurate physical exam and complete imaging study. At an average FU of 36 months, mean IKDC score and Lysholm score improved from 32 to 82 and from 38 to 74. 13 patients out of 17 (76.5%) were satisfied or extremely satisfied with their functional result. MRI control showed reduction of the defect area and subchondral oedema in 10 cases (58.8%). AMIC technique is a relatively new option in the treatment of full thickness cartilage lesions. It enhances the advantages of microfractures since the Chondrogide membrane protects and stabilizes the blood plug acting as a matrix for new cartilage formation. First reports on AMIC technique, show comparable results to autologous chondrocyte implantation (ACI) with the advantage of a single stage technique and no donor site morbidity. AMIC technique represents a new option in the treatment of full thickness cartilage defect. It is safe and reliable. Our data are in accordance with previously reported series in literature and confirm the good objective and subjective results of this procedure.

Evaluation of intra-articular mesenchymal stem cells to augment healing of microfractured chondral defects

PURPOSE

This study evaluated intra-articular injection of bone marrow-derived mesenchymal stem cells (BMSCs) to augment healing with microfracture compared with microfracture alone.

METHODS

Ten horses (aged 2.5 to 5 years) had 1-cm2 defects arthroscopically created on both medial femoral condyles of the stifle joint (analogous to the human knee). Defects were debrided to subchondral bone followed by microfracture. One month later, 1 randomly selected medial femorotibial joint in each horse received an intra-articular injection of either 20 × 10(6) BMSCs with 22 mg of hyaluronan or 22 mg of hyaluronan alone. Horses were confined for 4 months, with hand walking commencing at 2 weeks and then increasing in duration and intensity. At 4 months, horses were subjected to strenuous treadmill exercise simulating race training until completion of the study at 12 months. Horses underwent musculoskeletal and radiographic examinations bimonthly and second-look arthroscopy at 6 months. Horses were euthanized 12 months after the defects were made, and the affected joints underwent magnetic resonance imaging and gross, histologic, histomorphometric, immunohistochemical, and biochemical examinations.

RESULTS

Although there was no evidence of any clinically significant improvement in the joints injected with BMSCs, arthroscopic and gross evaluation confirmed a significant increase in repair tissue firmness and a trend for better overall repair tissue quality (cumulative score of all arthroscopic and gross grading criteria) in BMSC-treated joints. Immunohistochemical analysis showed significantly greater levels of aggrecan in repair tissue treated with BMSC injection. There were no other significant treatment effects.

CONCLUSIONS

Although there was no significant difference clinically or histologically in the 2 groups, this study confirms that intra-articular BMSCs enhance cartilage repair quality with increased aggrecan content and tissue firmness.

CLINICAL RELEVANCE

Clinical use of BMSCs in conjunction with microfracture of cartilage defects may be potentially beneficial.

Clinical outcome after microfracture of the knee: a meta-analysis of before/after-data of controlled studies

PURPOSE

The aims of this study were to systematically review the medical literature, in order to find controlled studies about microfracture in the treatment of patients with full-thickness cartilage lesions of the knee, to statistically combine these studies in order to determine a best estimate of the average treatment effect, and to gather information to detect cartilage-specific and patient-specific factors that might have an influence on the clinical outcome.

METHODS

We searched four electronic databases for controlled clinical trials or controlled prospective observational studies. We pooled before/after-data of study arms using the term microfracture.

RESULTS

We calculated an overall best estimate of 1.106, with [0.566; 1.646] as 95% confidence interval of the mean standardized treatment effect for a representative patient population.

CONCLUSIONS

Our meta-analysis revealed a clinically relevant improvement of the postoperative clinical status as compared to the preoperative status. An increase of 22 overall KOOS points may provide a rough estimate for the mean expected treatment effect achieved by microfracturing.

The comparison of equine articular cartilage progenitor cells and bone marrow-derived stromal cells as potential cell sources for cartilage repair in the horse

A chondrocyte progenitor population isolated from the surface zone of articular cartilage presents a promising cell source for cell-based cartilage repair. In this study, equine articular cartilage progenitor cells (ACPCs) and equine bone marrow-derived stromal cells (BMSCs) were compared as potential cell sources for repair. Clonally derived BMSCs and ACPCs demonstrated expression of the cell fate selector gene, Notch-1, and the putative stem cell markers STRO-1, CD90 and CD166. Chondrogenic induction revealed positive labelling for collagen type II and aggrecan. Collagen type X was not detected in ACPC pellets but was observed in all BMSC pellets. In addition, it was observed that BMSCs labelled for Runx2 and matrilin-1 antibodies, whereas ACPC labelling was significantly less or absent. For both cell types, osteogenic induction revealed positive von Kossa staining in addition to positive labelling for osteocalcin. Adipogenic induction revealed a positive result via oil red O staining in both cell types. ACPCs and BMSCs have demonstrated functional equivalence in their multipotent differentiation capacity. Chondrogenic induction of BMSCs resulted in a hypertrophic cartilage (endochondral) phenotype, which can limit cartilage repair as the tissue can undergo mineralisation. ACPCs may therefore be considered superior to BMSCs in producing cartilage capable of functional repair.

Equine Models of Articular Cartilage Repair

Articular cartilage injuries of the knee and ankle are common, and a number of different methods have been developed in an attempt to improve their repair. Clinically, there are 2 distinct aims of cartilage repair: 1) restoration of joint function and 2) prevention or at least delay of the onset of osteoarthritis. These goals can potentially be achieved through replacement of damaged or lost articular cartilage with tissue capable of functioning under normal physiological environments for an extended period, but limitations of the final repair product have long been recognized and still exist today. Screening of potential procedures for human clinical use is done by preclinical studies using animal models. This article reviews equine chondral defect models that have been recently recognized to have specific advantages for translation into human articular cartilage regeneration. Defect models in the femoropatellar, femorotibial, and tibiotalar joints have been developed. The horse provides the closest approximation to humans in terms of articular cartilage and subchondral bone thickness, and it is possible to selectively leave the entire calcified cartilage layer or completely remove it. The defect on the equine medial femoral condyle emulates medial femoral condylar lesions in humans. Other advantages of the equine model include an ability to use an arthroscope to create lesions and perform second-look arthroscopies, the large lesion size allowing for more tissue for evaluation, and the ability to have controlled exercise and test the ability of the repair to cope with athletic exercise as well as institute rehabilitation regimens.

Characterization of subchondral bone repair for marrow-stimulated chondral defects and its relationship to articular cartilage resurfacing

BACKGROUND

Microfracture and drilling are bone marrow-stimulation techniques that initiate cartilage repair by providing access to cell populations in subchondral bone marrow. This study examined the effect of hole depth and of microfracture versus drilling on subchondral bone repair and cartilage repair in full-thickness chondral defects.

HYPOTHESES

Repaired subchondral bone does not reconstitute its native structure and exhibits atypical morphologic features. Drilling deeper induces greater bone remodeling and is related to improved cartilage repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Trochlear cartilage defects debrided of the calcified layer were prepared bilaterally in 16 skeletally mature rabbits. Drill holes were made to a depth of 2 mm or 6 mm and microfracture holes to 2 mm. Animals were sacrificed 3 months postoperatively, and joints were scanned by micro-computed tomography before histoprocessing. Bone repair was assessed with a novel scoring system and by 3-dimentional micro-computed tomography and compared with intact controls. Correlation of subchondral bone features to cartilage repair outcome was performed.

RESULTS

Although surgical holes were partly repaired with mineralized tissue, atypical features such as residual holes, cysts, and bony overgrowth were frequently observed. For all treatment groups, repair led to an average bone volume density similar to that of the controls but the repair bone was more porous and branched as shown by significantly higher bone surface area density and connectivity density. Deeper versus shallower drilling induced a larger region of repairing and remodeling subchondral bone that positively correlated with improved cartilage repair.

CONCLUSION

Incomplete reconstitution of normal bone structure and continued remodeling occurred in chondral defects 3 months after bone marrow stimulation. Deep drilling induced a larger volume of repairing and remodeling bone, which appeared beneficial for chondral repair.

CLINICAL RELEVANCE

Bone marrow stimulation does not reconstitute normal bone structure. Strategies that increase subchondral bone involvement in marrow stimulation could further benefit cartilage repair.

Articular cartilage repair using an intra-articular magnet and synovium-derived cells

The purpose of this study was to investigate the chondrogenic potential of magnetically labeled synovium-derived cells (M-SDCs) and examine whether M-SDCs could repair the articular cartilage using an intra-articular magnet after delivery to the lesion. Synovium-derived cells (SDCs) were cultured from the synovium of a rat knee, and were magnetically labeled with ferumoxides. M-SDCs were examined with a transmission electron microscope. A pellet culture system was used to evaluate the chondrogenic potential of M-SDCs in a magnetic field. In a rat model, allogeneic M-SDCs were injected into the knee after we made an osteochondral defect on the patellar groove and implanted an intra-articular magnet at the bottom of the defect. We histologically examined the defects at 48 h, 4 weeks, 8 weeks, and 12 weeks after treatment. Electron microscopy showed the transfection of ferumoxides into SDCs. The pellet cultures revealed the chondrogenic potential of M-SDCs in a magnetic field. M-SDCs accumulated in the osteochondral defect at 48 h after treatment, and we confirmed the regeneration of the articular cartilage at 4 weeks, 8 weeks, and 12 weeks after treatment using an intra-articular magnet. We demonstrated that articular cartilage defects could be repaired using an intra-articular magnet and M-SDCs. We believe that this system will be useful to repair human articular cartilage defects.

International Cartilage Repair Society (ICRS) Recommended Guidelines for Histological Endpoints for Cartilage Repair Studies in Animal Models and Clinical Trials

Cartilage repair strategies aim to resurface a lesion with osteochondral tissue resembling native cartilage, but a variety of repair tissues are usually observed. Histology is an important structural outcome that could serve as an interim measure of efficacy in randomized controlled clinical studies. The purpose of this article is to propose guidelines for standardized histoprocessing and unbiased evaluation of animal tissues and human biopsies. Methods were compiled from a literature review, and illustrative data were added. In animal models, treatments are usually administered to acute defects created in healthy tissues, and the entire joint can be analyzed at multiple postoperative time points. In human clinical therapy, treatments are applied to developed lesions, and biopsies are obtained, usually from a subset of patients, at a specific time point. In striving to standardize evaluation of structural endpoints in cartilage repair studies, 5 variables should be controlled: 1) location of biopsy/sample section, 2) timing of biopsy/sample recovery, 3) histoprocessing, 4) staining, and 5) blinded evaluation with a proper control group. Histological scores, quantitative histomorphometry of repair tissue thickness, percentage of tissue staining for collagens and glycosaminoglycan, polarized light microscopy for collagen fibril organization, and subchondral bone integration/structure are all relevant outcome measures that can be collected and used to assess the efficacy of novel therapeutics. Standardized histology methods could improve statistical analyses, help interpret and validate noninvasive imaging outcomes, and permit cross-comparison between studies. Currently, there are no suitable substitutes for histology in evaluating repair tissue quality and cartilaginous character.

Preclinical Studies for Cartilage Repair: Recommendations from the International Cartilage Repair Society

Investigational devices for articular cartilage repair or replacement are considered to be significant risk devices by regulatory bodies. Therefore animal models are needed to provide proof of efficacy and safety prior to clinical testing. The financial commitment and regulatory steps needed to bring a new technology to clinical use can be major obstacles, so the implementation of highly predictive animal models is a pressing issue. Until recently, a reductionist approach using acute chondral defects in immature laboratory species, particularly the rabbit, was considered adequate; however, if successful and timely translation from animal models to regulatory approval and clinical use is the goal, a step-wise development using laboratory animals for screening and early development work followed by larger species such as the goat, sheep and horse for late development and pivotal studies is recommended. Such animals must have fully organized and mature cartilage. Both acute and chronic chondral defects can be used but the later are more like the lesions found in patients and may be more predictive. Quantitative and qualitative outcome measures such as macroscopic appearance, histology, biochemistry, functional imaging, and biomechanical testing of cartilage, provide reliable data to support investment decisions and subsequent applications to regulatory bodies for clinical trials. No one model or species can be considered ideal for pivotal studies, but the larger animal species are recommended for pivotal studies. Larger species such as the horse, goat and pig also allow arthroscopic delivery, and press-fit or sutured implant fixation in thick cartilage as well as second look arthroscopies and biopsy procedures.

Generation of hyaline cartilaginous tissue from mouse adult dermal fibroblast culture by defined factors

Repair of cartilage injury with hyaline cartilage continues to be a challenging clinical problem. Because of the limited number of chondrocytes in vivo, coupled with in vitro de-differentiation of chondrocytes into fibrochondrocytes, which secrete type I collagen and have an altered matrix architecture and mechanical function, there is a need for a novel cell source that produces hyaline cartilage. The generation of induced pluripotent stem (iPS) cells has provided a tool for reprogramming dermal fibroblasts to an undifferentiated state by ectopic expression of reprogramming factors. Here, we show that retroviral expression of two reprogramming factors (c-Myc and Klf4) and one chondrogenic factor (SOX9) induces polygonal chondrogenic cells directly from adult dermal fibroblast cultures. Induced cells expressed marker genes for chondrocytes but not fibroblasts, i.e., the promoters of type I collagen genes were extensively methylated. Although some induced cell lines formed tumors when subcutaneously injected into nude mice, other induced cell lines generated stable homogenous hyaline cartilage–like tissue. Further, the doxycycline-inducible induction system demonstrated that induced cells are able to respond to chondrogenic medium by expressing endogenous Sox9 and maintain chondrogenic potential after substantial reduction of transgene expression. Thus, this approach could lead to the preparation of hyaline cartilage directly from skin, without generating iPS cells.

Intraarticular location predicts cartilage filling and subchondral bone changes in a chondral defect

BACKGROUND AND PURPOSE

The natural history of, and predictive factors for outcome of cartilage restoration in chondral defects are poorly understood. We investigated the natural history of cartilage filling subchondral bone changes, comparing defects at two locations in the rabbit knee.

ANIMALS AND METHODS

In New Zealand rabbits aged 22 weeks, a 4-mm pure chondral defect (ICRS grade 3b) was created in the patella of one knee and in the medial femoral condyle of the other. A stereo microscope was used to optimize the preparation of the defects. The animals were killed 12, 24, and 36 weeks after surgery. Defect filling and the density of subchondral mineralized tissue was estimated using Analysis Pro software on micrographed histological sections.

RESULTS

The mean filling of the patellar defects was more than twice that of the medial femoral condylar defects at 24 and 36 weeks of follow-up. There was a statistically significant increase in filling from 24 to 36 weeks after surgery at both locations. The density of subchondral mineralized tissue beneath the defects subsided with time in the patellas, in contrast to the density in the medial femoral condyles, which remained unchanged.

INTERPRETATION

The intraarticular location is a predictive factor for spontaneous filling and subchondral bone changes of chondral defects corresponding to ICRS grade 3b. Disregarding location, the spontaneous filling increased with long-term follow-up. This should be considered when evaluating aspects of cartilage restoration.

2010 Nicolas Andry Award: Multipotent adult stem cells from adipose tissue for musculoskeletal tissue engineering

BACKGROUND

Cell-based therapies such as tissue engineering provide promising therapeutic possibilities to enhance the repair or regeneration of damaged or diseased tissues but are dependent on the availability and controlled manipulation of appropriate cell sources.

QUESTIONS/PURPOSES

The goal of this study was to test the hypothesis that adult subcutaneous fat contains stem cells with multilineage potential and to determine the influence of specific soluble mediators and biomaterial scaffolds on their differentiation into musculoskeletal phenotypes.

METHODS

We reviewed recent studies showing the stem-like characteristics and multipotency of adipose-derived stem cells (ASCs), and their potential application in cell-based therapies in orthopaedics.

RESULTS

Under controlled conditions, ASCs show phenotypic characteristics of various cell types, including chondrocytes, osteoblasts, adipocytes, neuronal cells, or muscle cells. In particular, the chondrogenic differentiation of ASCs can be induced by low oxygen tension, growth factors such as bone morphogenetic protein-6 (BMP-6), or biomaterial scaffolds consisting of native tissue matrices derived from cartilage. Finally, focus is given to the development of a functional biomaterial scaffold that can provide ASC-based constructs with mechanical properties similar to native cartilage.

CONCLUSIONS

Adipose tissue contains an abundant source of multipotent progenitor cells. These cells show cell surface marker profiles and differentiation characteristics that are similar to but distinct from other adult stem cells, such as bone marrow mesenchymal stem cells (MSCs).

CLINICAL RELEVANCE

The availability of an easily accessible and reproducible cell source may greatly facilitate the development of new cell-based therapies for regenerative medicine applications in the musculoskeletal system.

Traumatic osteochondral injury of the femoral head treated by mosaicplasty: a report of two cases

The increased risk of symptomatic progression towards osteoarthritis after chondral damage has led to the development of multiple treatment options for cartilage repair. These procedures have evolved from arthroscopic lavage and debridement, to marrow stimulation techniques, and more recently, to osteochondral autograft and allograft transplants, and autogenous chondrocyte implantation. The success of mosaicplasty procedures in the knee has led to its application to other surfaces, including the talus, tibial plateau, patella, and humeral capitellum. In this report, we present two cases of a chondral defect to the femoral head after a traumatic hip dislocation, treated with an osteochondral autograft (OATS) from the ipsilateral knee, and the inferior femoral head, respectively, combined with a surgical dislocation of the hip. At greater than 1 year and greater than 5 years of follow-up, MRI studies have demonstrated good autograft incorporation with maintenance of articular surface conformity, and both patients clinically continue to have no pain and full active range of motion of their respective hips. In our opinion, treatment of osteochondral defects in the femoral head surface using a surgical dislocation combined with an OATS procedure is a promising approach, as full exposure of the femoral head can be obtained while preserving its vasculature, thus enabling adequate restoration of the articular cartilage surface.

Rehabilitation following microfracture for chondral injury in the knee

Full-thickness chondral defects in the knee are common, and these articular cartilage lesions may present in various clinical settings and at different ages. Articular cartilage defects that extend full thickness to subchondral bone rarely - by providing a suitable environment for new tissue formation and takes advantage of the body's own healing potential. Proper surgical technique and rehabilitation improve the success rate of the microfracture procedure. The goals are to alleviate the pain and disability that can result from chondral lesions and restore joint conformity, thereby preventing late degenerative changes in the joint.

Treatment of articular cartilage lesions of the knee joint using a modified AMIC technique

This study describes a modified AMIC technique consisting of perforations according to Pridie, rather than microfractures, and the covering of the focus of the lesion with a biological collagen patch enriched with bone marrow blood drawn through the knee itself. This technique allows advantages of both the Pridie technique and the in situ proliferation of mesenchymal cells beneath a biological collagen membrane, 'augmented', with bone marrow blood. The collagen membrane forms the roof of a 'biological chamber', and serves to protect and contains the stem cells as they differentiate into chondrocytes, which will form a healthy regenerative cartilage.

Management of articular cartilage defects of the knee

Articular cartilage has a poor intrinsic capacity for healing. The goal of surgical techniques to repair articular cartilage injuries is to achieve the regeneration of organized hyaline cartilage. Microfracture and other bone marrow stimulation techniques involve penetration of the subchondral plate in order to recruit mesenchymal stem cells into the chondral defect. The formation of a stable clot that fills the lesion is of paramount importance to achieve a successful outcome. Mosaicplasty is a viable option with which to address osteochondral lesions of the knee and offers the advantage of transplanting hyaline cartilage. However, limited graft availability and donor site morbidity are concerns. Transplantation of an osteochondral allograft consisting of intact, viable articular cartilage and its underlying subchondral bone offers the ability to address large osteochondral defects of the knee, including those involving an entire compartment. The primary theoretical advantage of autologous chondrocyte implantation is the development of hyaline-like cartilage rather than fibrocartilage in the defect, which presumably leads to better long-term outcomes and longevity of the healing tissue. Use of synthetic scaffolds is a potentially attractive alternative to traditional cartilage procedures as they are readily available and, unlike allogeneic tissue transplants, are associated with no risk of disease transmission. Their efficacy, however, has not been proven clinically.

Augmentation Strategies following the Microfracture Technique for Repair of Focal Chondral Defects

The operative management of focal chondral lesions continues to be problematic for the treating orthopedic surgeon secondary to the limited regenerative capacity of articular cartilage. Although many treatment options are currently available, none fulfills the criteria for an ideal repair solution, including a hyaline repair tissue that completely fills the defect and integrates well with the surrounding normal cartilage. The microfracture technique is an often-utilized, first-line treatment modality for chondral lesions within the knee, resulting in the formation of a fibrocartilaginous repair tissue with inferior biochemical and biomechanical properties compared to normal hyaline cartilage. Although symptomatic improvement has been shown in the short term, concerns about the durability and longevity of the fibrocartilaginous repair have been raised. In response, a number of strategies and techniques for augmentation of the first-generation microfracture procedure have been introduced in an effort to improve repair tissue characteristics and reduce long-term deterioration. Recent experimental approaches utilize modern tissue-engineering technologies including local supplementation of chondrogenic growth factors, hyaluronic acid, or cytokine modulation. Other second-generation microfracture-based techniques use different types of scaffold-guided in situ chondroinduction. The current article presents a comprehensive overview of both the experimental and early clinical results of these developing microfracture augmentation techniques.

Microfracture: Its History and Experience of the Developing Surgeon

Development and implementation of the microfracture technique began in the early 1980s. The surgical goal was to produce "microfractures" in the subchondral bone perpendicular to the surface and to be able to reach all areas of the joint with the instruments. The microfracture technique has been demonstrated to be an effective arthroscopic treatment for full-thickness chondral lesions and joints with degenerative lesions. This technique is cost effective, technically not complicated, has an extremely low rate of associated patient morbidity, and leaves options for further treatment. Patient compliance with rehabilitation, knee alignment, and the depth of the cartilage rim surrounding the lesion are a few of the factors that can affect the outcomes following microfracture.

Microfracture: Basic Science Studies in the Horse

The therapeutic value of microfracture has been demonstrated in clinical patients. The rationale is that focal penetration of the dense subchondral plate exposes cartilage defects to the benefits of cellular and growth factor influx in addition to improving anchorage of the new tissue to the underlying subchondral bone and, to some extent, the surrounding cartilage. While functional outcomes have been reported, there is a paucity of data on the histological, biochemical, and molecular changes in human patients. This paper reviews 4 basic science studies of microfracture using an equine chondral defect model that gave some insight into possible mechanisms of action and also how the microfracture response could be augmented. In study I, microfracture of full-thickness chondral defects in exercised horses significantly increased the repair tissue volume in the defects at both 4 and 12 months. No adverse effects were seen. In study II, an investigation of the healing of full-thickness chondral defects during the first 8 weeks with or without microfracture demonstrated that microfracture significantly increased type II collagen expression as early as 8 weeks after treatment compared to controls; aggrecan expression was progressively increased during the first 8 weeks but was not significantly enhanced by microfracture. In study III, it was demonstrated that removal of the calcified cartilage layer provided optimal amount and attachment of repair tissue, emphasizing that careful removal of calcified layer is critical during debridement prior to microfracture. Study IV assessed the ability of IL-1ra/IGF-1 combination gene therapy to further modulate repair of microfractured chondral defects. The repair tissue in gene therapy-treated joints demonstrated increased proteoglycan and type II collagen content compared to microfracture alone.

Glenohumeral Microfracture

The treatment of symptomatic cartilage lesions in the glenohumeral joint presents a significant challenge due to poor healing characteristics. Diagnosis of glenohumeral chondral defects is not always clear, and while current imaging modalities are good, many lesions require arthroscopy to fully appreciate. Arthroplasty remains an effective treatment in low-demand patients; however, younger, higher demand individuals may be treated with less invasive reparative measures. This paper discusses the diagnosis of glenohumeral chondral pathology and presents the technique, rehabilitation, and available outcomes following microfracture in the shoulder.

Clinical outcomes after microfracture of the glenohumeral joint

BACKGROUND

Microfracture is an effective surgical treatment for isolated, full-thickness cartilage defects with current data focused on applications in the knee. No studies describing clinical outcomes of patients who have undergone microfracture in the shoulder joint have been reported.

HYPOTHESIS

Treatment of glenohumeral joint articular defects using microfracture would demonstrate similar short-term clinical outcomes when compared with other joints.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From March 2001 to August 2007, 16 patients (17 shoulders) who underwent arthroscopic microfracture of the humeral head and/or glenoid surface were retrospectively reviewed. All patients were examined by an independent, blinded examiner and completed surveys containing the Simple Shoulder Test (SST), American Shoulder and Elbow Score (ASES), and visual analog scale (VAS).

RESULTS

Two patients were lost to follow-up, for a follow-up rate of 88%. Three patients went on to subsequent shoulder surgery and were considered to have failed results. The mean age was 37.0 years (range, 18-55 years) with an average follow-up of 27.8 months (range, 12.1-89.2 months). The average size of humeral and glenoid defects was 5.07 cm(2) (range, 1.0-7.84 cm(2)) and 1.66 cm(2) (range, 0.4-3.75 cm(2)), respectively. There was a statistically significant decrease from 5.6 +/- 1.7 to 1.9 +/- 1.4 (P < .01) in VAS after surgery as well as statistically significant improvements (P < .01) in SST (5.7 +/- 2.1 to 10.3 +/- 1.3) and ASES (44.3 +/- 15.3 to 86.3 +/- 10.5). Twelve (92.3%) patients claimed they would have the procedure again.

CONCLUSION

Microfracture of the glenohumeral joint provides a significant improvement in pain relief and shoulder function in patients with isolated, full-thickness chondral injuries. Longer term studies are required to determine if similar results are maintained over time.

Transcriptional comparisons between equine articular repair tissue, neonatal cartilage, cultured chondrocytes and mesenchymal stromal cells

Human and equine cell transplant strategies for cartilage lesions usually result in scar tissue that is similar to what is produced naturally during the repair process. In this study, culture-expanded de-differentiated chondrocytes and primary bone marrow stromal cells at a pre-transplantation time-point were compared along with neonatal cartilage to repair tissue. Transcriptional profiling using a 9413-probeset equine-specific cDNA microarray and targeted real-time quantitative polymerase chain reaction validation were used to characterize relationships between these cell types and repair tissue both broadly and for individual cartilage biomarkers. The greatest divergence in expression was detected for transcripts encoding matrix proteins that typically define the differentiation status of normal articular cartilage and fibrocartilage repair tissue. Expression patterns and gene ontology analyses indicated that while the repair cells were more chondrogenic than bone marrow stromal cells and de-differentiated cultured chondrocytes, steady-state levels of transcripts encoding cartilage biomarkers were substantially lower than the amounts found in neonatal articular cartilage. By characterizing gene expression differences amongst these tissues, we present important targets to monitor when developing improvements to cartilage engineering therapies.

In vivo evaluation of autologous cartilage fragment-loaded scaffolds implanted into equine articular defects and compared with autologous chondrocyte implantation

BACKGROUND

Current autologous chondrocyte implantation (ACI) techniques require 2 surgical procedures: 1 for cell harvest and 1 for reimplantation of cultured cells. A 1-step procedure is more desirable.

PURPOSE

A 1-step surgical procedure using autologous cartilage fragments on a polydioxanone scaffold, or CAIS (cartilage autograft implantation system), in a clinically relevant defect (15-mm diameter) within equine femoral trochlea was compared with a 2-step ACI technique as well as with empty defects and defects with polydioxanone foam scaffolds alone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten skeletally mature horses were used. Articular cartilage from the lateral trochlea of the femur was harvested arthroscopically (n = 5), and chondrocytes were cultured on small intestinal submucosa to produce ACI constructs. The CAIS procedure had cartilage harvested during defect creation to prepare minced cartilage on polydioxanone-reinforced foam. The ACI and CAIS constructs were placed in defects using polydioxanone/polyglycolic acid staples. Defects were examined arthroscopically at 4, 8, and 12 months and with gross, histological, and immunohistochemical examination at 12 months.

RESULTS

Arthroscopic, histologic, and immunohistochemistry results show superiority of both implantation techniques (ACI and CAIS) compared with empty defects and defects with polydioxanone foam alone, with CAIS having the highest score.

CONCLUSION

This is the first demonstration of long-term healing with strenuous exercise using ACI and CAIS in a critically sized defect.

CLINICAL RELEVANCE

Given these results with the CAIS procedure, testing in human patients is the next logical step (a phase 1 human clinical study has proceeded from this work).

Recommendations and treatment outcomes for patellofemoral articular cartilage defects with autologous chondrocyte implantation: prospective evaluation at average 4-year follow-up

BACKGROUND

Reported results of autologous chondrocyte implantation for chondral lesions in the patellofemoral joint have been encouraging when combined with realignment procedures.

PURPOSE

The objective of this study was to examine the clinical results of a patient cohort undergoing autologous chondrocyte implantation of the patellofemoral joint and elucidate characteristics associated with successful implantation.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The cohort included 62 patients who underwent autologous chondrocyte implantation of the PF joint. The mean defect size was 4.2 cm(2) (+/-1.6). The average age was 31.8 years (range, 15.8-49.4), and the average follow-up was 4 years (range, 2-7). Outcomes were assessed via clinical assessment and established outcome scales, including the Lysholm, International Knee Documentation Committee, Knee Injury and Osteoarthritis Outcome Scale (KOOS; includes the 5 categories of Pain, Symptoms, Activities of Daily Living, Sport, and Quality of Life), Tegner, Cincinnati, and Short Form-12.

RESULTS

Mean improvement in the preoperative to postoperative scores was significant for the Lysholm (37-63, P <.001), International Knee Documentation Committee (31-57, P <.001), KOOS Pain (48-71, P <.001), KOOS Symptoms (51-70, P <.001), KOOS Activities of Daily Living (60-80, P <.001), KOOS Sport (25-42, P <.001), KOOS Quality of Life (24-49, P <.001), Short Form-12 Physical (38-41, P <.05), Cincinnati (43-63, P <.005), and Tegner (4-6, P <.05), but not for the Short Form-12 Mental. There was no statistical difference between outcomes in patients with a history of a previous failed cartilage procedure compared with those patients without a prior cartilage procedure (P > .05). Patients undergoing anteromedialization tended toward better outcomes than those without realignment. Forty-four percent of patients needed a subsequent procedure. There were 4 clinical failures (7.7%), which were defined as progression to arthroplasty or conversion to osteochondral allograft transplantation.

CONCLUSION

Autologous chondrocyte implantation is a viable treatment option for chondral defects of the patellofemoral joint. Combined autologous chondrocyte implantation with anteromedialization improves outcomes more than autologous chondrocyte implantation alone. Patients with failed prior cartilage procedures can also expect sustained and clinically meaningful improvement.

Transcriptional profiling differences for articular cartilage and repair tissue in equine joint surface lesions

Background

Full-thickness articular cartilage lesions that reach to the subchondral bone yet are restricted to the chondral compartment usually fill with a fibrocartilage-like repair tissue which is structurally and biomechanically compromised relative to normal articular cartilage. The objective of this study was to evaluate transcriptional differences between chondrocytes of normal articular cartilage and repair tissue cells four months post-microfracture.

Methods

Bilateral one-cm² full-thickness defects were made in the articular surface of both distal femurs of four adult horses followed by subchondral microfracture. Four months postoperatively, repair tissue from the lesion site and grossly normal articular cartilage from within the same femorotibial joint were collected. Total RNA was isolated from the tissue samples, linearly amplified, and applied to a 9,413-probe set equine-specific cDNA microarray. Eight paired comparisons matched by limb and horse were made with a dye-swap experimental design with validation by histological analyses and quantitative real-time polymerase chain reaction (RT-qPCR).

Results

Statistical analyses revealed 3,327 (35.3%) differentially expressed probe sets. Expression of biomarkers typically associated with normal articular cartilage and fibrocartilage repair tissue corroborate earlier studies. Other changes in gene expression previously unassociated with cartilage repair were also revealed and validated by RT-qPCR.

Conclusion

The magnitude of divergence in transcriptional profiles between normal chondrocytes and the cells that populate repair tissue reveal substantial functional differences between these two cell populations. At the four-month postoperative time point, the relative deficiency within repair tissue of gene transcripts which typically define articular cartilage indicate that while cells occupying the lesion might be of mesenchymal origin, they have not recapitulated differentiation to the chondrogenic phenotype of normal articular chondrocytes.

TGF-beta3: A potential biological therapy for enhancing chondrogenesis

BACKGROUND

TGF-beta has been proposed to stimulate chondrogenesis through intracellular pathways involving small mothers against decapentaplegic proteins (Smads).

OBJECTIVE

To examine the use of exogenous TGF-beta3 to promote new hyaline cartilage formation.

METHODS

An overview of in vitro and in vivo evidence on the effects of TGF-beta3 on cartilage regeneration.

RESULTS/CONCLUSION

There is robust in vitro evidence suggesting a positive dose- and time-dependent effect of TGF-beta3 on anabolic chondrogenic gene markers such as alpha1-collagen type II and cartilage oligomeric matrix protein in human mesenchymal stem cells. TGF-beta3 cultured with silk elastin-like polymer scaffold carrier exhibits significantly increased glycosaminoglycan and collagen content. In vivo data showed that TGF-beta3 cultured with ovine mesenchymal stem cells in a chitosan scaffold stimulated the growth of hyaline cartilage that was fully integrated into host cartilage tissue of sheep. We highlight the potential for the clinical enhancement of cartilage formation through the use of TGF-beta3 with a suitable dose and scaffold carrier.

Local delivery of autologous platelet in collagen matrix simulated in situ articular cartilage repair

Bone marrow released by microfracture or full-thickness cartilage defect can initiate the in situ cartilage repair. However, it can only repair small cartilage defects (<2 cm(2)). This study aimed to investigate whether autologous platelet-rich plasma (PRP) transplantation in collagen matrix can improve the in situ bone marrow-initiated cartilage repair. Full-thickness cartilage defects (diameter 4 mm, thickness 3 mm) in the patellar grooves of male New Zealand White rabbits were chosen as a model of in situ cartilage repair. They were treated with bilayer collagen scaffold (group II), PRP and bilayer collagen scaffold (group III), and untreated (group I), respectively (n = 11). The rabbits were sacrificed at 6 and 12 weeks after operation. The repaired tissues were processed for histology and for mechanical test. The results showed that at both 6 and 12 weeks, group III had the largest amounts of cartilage tissue, which restored a larger surface area of the cartilage defects. Moreover, group III had higher histological scores and more glycosaminoglycans (GAGs) content than those in the other two groups (p < 0.05). The Young's modulus of the repaired tissue in group II and group III was higher than that of group I (p < 0.05). Autologous PRP and bilayer collagen matrix stimulated the formation of cartilage tissues. The findings implicated that the combination of PRP with collagen matrix may repair larger cartilage defects that currently require complex autologous chondrocyte implantation (ACI) or osteochondral grafting.

Outcomes of full-thickness articular cartilage injuries of the shoulder treated with microfracture

PURPOSE

The purpose of this study was to determine whether microfracture provides pain relief and improves shoulder function in patients with chondral defects of the glenohumeral joint.

METHODS

Microfracture was performed in glenohumeral joints with full-thickness chondral lesions. Concomitant procedures were performed as indicated. Patients aged 60 years or older and those with complete rotator cuff tears were excluded. We included 31 shoulders in 30 patients in this study. Included were 25 men and 5 women with a mean age of 43 years (range, 19 to 59 years). Of the 31 surgeries, 6 (19%) progressed to another surgery. Subjective data obtained at a minimum of 2 years' follow-up were available in 24 patients (25 shoulders). Patient pain and functional outcomes were measured by use of the American Shoulder and Elbow Surgeons (ASES) score and patient satisfaction. Data were analyzed by use of paired t tests and regression analysis.

RESULTS

The mean follow-up was 47 months (range, 25 to 128 months). The mean pain scores decreased from 3.8 to 1.6 postoperatively (0, no pain; 10, worst pain). The patients' ability to work, activities of daily living, and sports activity significantly improved postoperatively (P < .05). Painless use of the involved arm improved postoperatively (P < .05). The mean ASES score improved by 20 points over the preoperative score (P < .05). Mean satisfaction with surgical outcome was 7.6 of 10. There was no association between age or gender and surgical outcomes. The greatest improvements were seen in patients who had microfracture of isolated lesions of the humerus.

CONCLUSIONS

Failure occurred in 6 of the 31 shoulders (19%). In the remaining patients there was a significant improvement of 20 points (range, -11 to 45 points) in the ASES score compared with preoperatively. In those patients in whom just the humerus was treated, the greatest improvement was seen, with an increase of 32 points (range, 3 to 87 points). There was a negative correlation between the size of the lesion and ASES improvement (r = -0.351, P = .12). Our data showed the greatest improvement for smaller lesions of the humerus with the worst results in patients with bipolar lesions.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Solidification mechanisms of chitosan-glycerol phosphate/blood implant for articular cartilage repair

OBJECTIVE

Chitosan-glycerol phosphate (chitosan-GP) is a unique polymer solution that is mixed with whole blood and solidified over microfractured or drilled articular cartilage defects in order to elicit a more hyaline repair cartilage. For clinical ease-of-use, a faster in situ solidification is preferred. Therefore, we investigated the mechanisms underlying chitosan-GP/blood implant solidification.

METHODS

In vitro solidification of chitosan-GP/blood mixtures, with or without added clotting factors, was evaluated by thromboelastography. Serum was analyzed for the onset of thrombin, platelet, and FXIII activation. In vivo solidification of chitosan-GP/blood mixtures, with and without clotting factors, was evaluated in microdrilled cartilage defects of adult rabbits (N=41 defects).

RESULTS

Chitosan-GP/blood clots solidified in an atypical biphasic manner, with higher initial viscosity and minor platelet activation followed by the development of clot tensile strength concomitant with thrombin generation, burst platelet and FXIII activation. Whole blood and chitosan-GP/blood clots developed a similar final clot tensile strength, while polymer-blood clots showed a unique, sustained platelet factor release and greater resistance to lysis by tissue plasminogen activator. Thrombin, tissue factor (TF), and recombinant human activated factor VII (rhFVIIa) accelerated chitosan-GP/blood solidification in vitro (P<0.05). Pre-application of thrombin or rhFVIIa+TF to the surface of drilled cartilage defects accelerated implant solidification in vivo (P<0.05).

CONCLUSIONS

Chitosan-GP/blood implants solidify through coagulation mechanisms involving thrombin generation, platelet activation and fibrin polymerization, leading to a dual fibrin-polysaccharide clot scaffold that resists lysis and is physically more stable than normal blood clots. Clotting factors have the potential to enhance the practical use, the residency, and therapeutic activity of polymer-blood implants.

Preclinical animal models in single site cartilage defect testing: a systematic review

OBJECTIVE

Review the literature for single site cartilage defect research and evaluate the respective strengths and weaknesses of different preclinical animal models.

METHOD

A literature search for animal models evaluating single site cartilage defects was performed. Variables tabulated and analyzed included animal species, age and number, defect depth and diameter and study duration. Cluster analyses were then used to separate animals with only distal femoral defects into similar groups based on defect dimensions. Representative human studies were included allowing comparison of common clinical lesions to animal models. The suitability of each species for single site cartilage defect research and its relevance to clinical human practice is then discussed.

RESULTS

One hundred thirteen studies relating to single site cartilage defects were reviewed. Cluster analysis included 101 studies and placed the murine, laprine, ovine, canine, porcine and caprine models in group 1. Group 2 contained ovine, canine, porcine, caprine and equine models. Group 3 contained only equine models and humans. Species in each group are similar with regard to defect dimensions. Some species occur in multiple groups reflecting utilization of a variety defect sizes. We report and discuss factors to be considered when selecting a preclinical animal model for single site cartilage defect research.

DISCUSSION

Standardization of study design and outcome parameters would help to compare different studies evaluating various novel therapeutic concepts. Comparison to the human clinical counterpart during study design may help increase the predictive value of preclinical research using animal models and improve the process of developing efficacious therapies.

The efficacy of intra-articular hyaluronan injection after the microfracture technique for the treatment of articular cartilage lesions

BACKGROUND

Although the exact mechanism of action has yet to be elucidated, recent animal studies have demonstrated chondroprotective and anti-inflammatory properties of hyaluronic acid viscosupplementation.

HYPOTHESIS

Intra-articular hyaluronic acid after microfracture improves the quality of the repair leading to a more hyaline-like repair tissue with better defect fill and adjacent area integration.

STUDY DESIGN

Controlled laboratory study.

METHODS

Full-thickness cartilage defects were created in the weightbearing area of the medial femoral condyle in 36 female New Zealand White rabbits. The defects were then treated with surgical microfracture. Eighteen rabbits formed the 3-month cohort and the other 18 formed the 6-month cohort. Within each cohort, 6 rabbits were randomly assigned to receive 3 weekly injections of hyaluronic acid (group A), 5 weekly injections (group B), or control injections of normal saline (group C). At 3 and 6 months postmicrofracture, the animals were sacrificed and the operative knee harvested. Repair tissue was assessed blinded- both grossly, using a modified component of the International Cartilage Repair Society (ICRS) Cartilage Repair Assessment scoring scale, and histologically, using the modified O'Driscoll histological cartilage scoring system. Comparisons were made with respect to gross and histologic findings between treatment groups at each time point. Effects of each treatment type were also evaluated longitudinally by comparing the 3-month results with the 6-month results. Statistical analysis was performed using unpaired Student t tests with significance defined as P < .05.

RESULTS

At 3 months, gross and histologic evaluation of the repair tissue demonstrated that the 3-injection group had significantly better fill of the defects and more normal appearing, hyaline-like tissue than controls (a mean ICRS score of 1.92 vs 1.26; P < .05 and a mean modified O'Driscoll score of 10.3 vs 7.6; P < .02). Specimens treated with 5 weekly injections were not significantly improved compared with controls. At 6 months, the mean gross appearance and histologic scores between the 3 specimen cohorts were not significantly different. However, examination of the entire operative knee demonstrated a significantly greater extent of degenerative changes (synovial inflammation and osteophyte formation) in the control group than in both hyaluronic acid treatment groups (P < .05).

CONCLUSION

Supplementing the microfracture technique with 3 weekly injections of intra-articular hyaluronic acid had a positive effect on the repair tissue that formed within the chondral defect at the early follow-up time point. This improvement was not found for the 3-injection group at 6 months or for the 5-injection group at either time point. Additionally, hyaluronic acid supplementation had a possible chondroprotective and anti-inflammatory effect, limiting the development of degenerative changes within the knee joint.

CLINICAL RELEVANCE

The adjunctive use of hyaluronic acid appears to hold promise in the treatment of chondral injuries and warrants further investigation.

Cartilage regeneration using a novel gelatin–chondroitin–hyaluronan hybrid scaffold containing bFGF-impregnated microspheres

Cartilage engineered from chondrocytes requires a scaffold to keep the cells in the cartilage defect and to act as a support for inducing hyaline cartilage formation on occasion. In this study, we developed a novel three-dimensional special scaffold in combination with a controlled release of bFGF, which provided structural support and stimulated repair. Gelatin microspheres loaded with bFGF (GM-bFGF) showed a fast release at the initial phase (28.23%) and the ultimate accumulated release was 92.9% by day 14. Three-dimensional gelatin-chondroitin-hyaluronan hybrid scaffolds seeded with cultured autologous chondrocytes were transplanted into the defects in rabbit knees and analyzed histologically at 12 and 24 weeks after the operation. Our findings showed that the defects were filled with smooth, shiny white cartilaginous tissue macroscopically and hyaline-like cartilage histologically 24 weeks postoperatively. The present study implied the great potential of the novel scaffold with GM-bFGF as a new way to promote the retention of chondrocytes and it might serve as a desirable cartilaginous tissue scaffolds to enhance the chondrogenesis.

Suture bridge fixation of a femoral condyle traumatic osteochondral defect

Internal fixation of a traumatic osteochondral defect presents a challenge in terms of obtaining anatomic reduction, fixation, and adequate compression for healing. Fixation with countersunk intraarticular screws, Herbert screws, bioabsorbable screws and pins, mini-cancellous screws, and glue tissue adhesive have been reported with varying results. We present an alternative fixation method used in two patients for femoral condylar defects that achieved anatomic reduction with compression via a cruciate-shaped suture bridge construct tied down over a bony bridge. This fixation method allowed early passive range of motion and permitted high-quality MRI for followup of fracture healing and articular cartilage integrity. Arthroscopic examination of one of two patients at 6 months followup showed the gross appearance of a healed, anatomically reduced fracture. With 1 year followup for one patient and 2 years for the other, the patients have resumed activity as tolerated with full, painless range of motion at the knee. Longer-term outcomes are unknown. However, the suture bridge is an alternative means of fixation with encouraging early results for treatment of traumatic osteochondral fragments in the knee.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

T2 mapping in the knee after microfracture at 3.0 T: correlation of global T2 values and clinical outcome - preliminary results

OBJECTIVE

The aim of our study was to correlate global T2 values of microfracture repair tissue (RT) with clinical outcome in the knee joint.

METHODS

We assessed 24 patients treated with microfracture in the knee joint. Magnetic resonance (MR) examinations were performed on a 3T MR unit, T2 relaxation times were obtained with a multi-echo spin-echo technique. T2 maps were obtained using a pixel wise, mono-exponential non-negative least squares fit analysis. Slices covering the cartilage RT were selected and region of interest analysis was done. An individual T2 index was calculated with global mean T2 of the RT and global mean T2 of normal, hyaline cartilage. The Lysholm score and the International Knee Documentation Committee (IKDC) knee evaluation forms were used for the assessment of clinical outcome. Bivariate correlation analysis and a paired, two tailed t test were used for statistics.

RESULTS

Global T2 values of the RT [mean 49.8ms, standards deviation (SD) 7.5] differed significantly (P<0.001) from global T2 values of normal, hyaline cartilage (mean 58.5ms, SD 7.0). The T2 index ranged from 61.3 to 101.5. We found the T2 index to correlate with outcome of the Lysholm score (r(s)=0.641, P<0.001) and the IKDC subjective knee evaluation form (r(s)=0.549, P=0.005), whereas there was no correlation with the IKDC knee form (r(s)=-0.284, P=0.179).

CONCLUSION

These findings indicate that T2 mapping is sensitive to assess RT function and provides additional information to morphologic MRI in the monitoring of microfracture.

[Microfracture technique for the treatment of articular cartilage lesions of the talus]

The microfracture technique is an established method for treating articular cartilage lesions of the talus. Symptomatic chondral or osteochondral lesions of grade II or higher with softening or fraying of the chondral surface or an unstable rim are indications for débridement of the lesion and use of the microfracture technique. In advanced degenerative lesions, the indication must be determined critically. In a prospective study, significant (p<0.001) improvement was observed at a mean follow-up of 5.2 years (range 3.8-6.6 years) in 23 ankles. According to the Hannover scoring system, 87% of the patients were rated as excellent or good. Results for patients older than 50 years were not inferior to those for younger patients. Results for overweight patients were significantly (p=0.03) worse compared with patients of normal weight. Magnetic resonance imaging findings revealed that filling of the defect is accomplished in the majority of cases with an inhomogeneous structure of the cartilage repair tissue and a high incidence of subchondral alterations. The microfracture technique appears to be a reliable method for treating chondral and osteochondral lesions of the talus, with good outcomes in a mid-term follow-up.