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

Cartilage repair with osteochondral autografts in sheep: effect of biophysical stimulation with pulsed electromagnetic fields

The effect of pulsed electromagnetic fields (PEMFs) on the integration of osteochondral autografts was evaluated in sheep. After osteochondral grafts were performed, the animals were treated with PEMFs for 6 h/day or sham-treated. Six animals were sacrificed at 1 month. Fourteen animals were treated for 2 months and sacrificed at 6 months. At 1 month, the osteogenic activity at the transplant-host subchondral bone interface was increased in PEMF-treated animals compared to controls. Articular cartilage was healthy in controls and stimulated animals. At 6 months, complete resorption was observed in four control grafts only. Cyst-like resorption areas were more frequent within the graft of sham-treated animals versus PEMF-treated. The average volume of the cysts was not significantly different between the two groups; nevertheless, analysis of the variance of the volumes demonstrated a significant difference. The histological score showed no significant differences between controls and stimulated animals, but the percentage of surface covered by fibrous tissue was higher in the control group than in the stimulated one. Interleukin-1 and tumor necrosis factor-alpha concentration in the synovial fluid was significantly lower, and transforming growth factor-beta1 was significantly higher, in PEMF-treated animals compared to controls. One month after osteochondral graft implantation, we observed larger bone formation in PEMF-treated grafts which favors early graft stabilization. In the long term, PEMF exposure limited the bone resorption in subchondral bone; furthermore, the cytokine profile in the synovial fluid was indicative of a more favorable articular environment for the graft.

Can microfracture produce repair tissue in acetabular chondral defects?

PURPOSE

The purpose of this study was to investigate percent fill and repair grade of microfractured lesions of the acetabulum.

METHODS

Nine patients underwent revision hip arthroscopy for a variety of procedures after undergoing microfracture for treatment of a full-thickness chondral defect of the acetabulum at primary arthroscopy. The size of the chondral defect was measured during primary arthroscopy, and the percent fill of the defect and repair grade were noted at revision hip arthroscopy.

RESULTS

Mean time from primary arthroscopy to revision was 20 months (range, 10 to 36 months). The average percent fill of the acetabular chondral lesions at second-look was 91% (range, 25% to 100%). Eight of the patients had grade 1 or 2 repair product at second-look. The 1 patient with 25% fill and grade 4 repair product had diffuse osteoarthritis on the femur and acetabulum at primary microfracture. One patient required total hip arthroplasty 66 months after the index microfracture.

CONCLUSIONS

In this study, 8 of 9 patients had 95% to 100% coverage of an isolated acetabular chondral lesion or acetabular lesion associated with a femoral head lesion, with grade 1 or 2 appearance of the repair product at an average of 20 months follow-up. One patient who had diffuse osteoarthritis failed, with only 25% coverage with a grade IV appearance of the repair product 10 months after index arthroscopy.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

In-situ engineering of cartilage repair: a pre-clinical in-vivo exploration of a novel system

This investigation explores a new cartilage repair technique that uses a novel method to secure a non-woven multifilamentous scaffold in the defect site after microfracture. The hypothesis is that a scaffold provides a larger surface area for attachment and proliferation of the mesenchymal stem cells that migrate from the bone marrow. Two in-vivo studies were undertaken in an ovine model. The first study, which lasted for 8 weeks, aimed to compare the new technique with microfracture. Chondral defects, 7 mm in diameter, were created in both femoral medial condyles of five ewes. One defect was treated with the new technique while the contralateral knee was treated with microfracture alone. The results revealed that the quantity of repair tissue was significantly greater in the defects treated with the new system. The second study had two time points, 3 and 6 months, and used 13 ewes. In this study, both defects were treated with the new technique but one received additional subchondral drilling in order to stimulate extra tissue growth. The majority of the implants had good tissue induction, filling 50-100 per cent of the defect volume, while the compressive modulus of the repairs was in the range of 40-70 per cent of that for the surrounding cartilage. In addition, hyaline-like cartilage was seen in all the repairs which had the additional drilling of the subchondral bone.

Synovial fluid recruits human mesenchymal progenitors from subchondral spongious bone marrow

Microfracture is a frequently used reparative technique that induces a healing response in articular cartilage defects. Penetration of the subchondral bone leads to blood clot formation, allows multipotent mesenchymal cells to access the defect and, subsequently, leads to cartilaginous repair tissue. The aim of our study was to analyze the chemotactic recruitment of human subchondral spongious bone marrow-derived cells by synovial fluid (SF) from normal donors (ND), patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Subchondral spongious bone marrow-derived mesenchymal progenitors were isolated from bone cylinders after high tibial osteotomy and analyzed for the presence of stem cell-related cell surface antigens by flow cytometry. Recruitment of subchondral progenitors by normal SF and SF from donors with degenerated joint diseases was documented by using a modified Boyden chamber chemotaxis assay. The chemotaxis assay demonstrated that synovial fluid has the potential to recruit mesenchymal progenitors in vitro. SF from normal donors and patients with OA showed no difference in the potential to stimulate cell migration. SF obtained from RA donors showed significantly reduced cell recruitment compared to SF derived from OA patients (p = 0.0054) and normal donors (p < 0.0001). The chemotactic activity of SF obtained from normal donors and from patients with degenerative joint diseases suggests that SF may be actively involved in the migration of progenitors in cartilage defects after microfracture.

IL-1ra/IGF-1 gene therapy modulates repair of microfractured chondral defects

Repair of cartilage defects involves sequential participation of specific hormones and growth factors with potential impairment by inflammatory cytokines. We explored an in vivo gene therapy treatment to supply adenoviral vectors carrying the genes of interleukin-1 receptor antagonist protein (IL-1ra) and insulinlike growth factor-1 (IGF-1), hoping to enhance repair of full-thickness equine chondral defects treated with microfracture. We asked whether our treatment could (1) increase proteoglycan and Type II collagen content in the repair tissue, (2) improve the macroscopic and histomorphometric aspect of the repair tissue, and (3) induce prolonged and increased IL-1ra and IGF-1 production in treated joints. Twelve horses had full-thickness chondral defects created in their carpus and stifle followed by microfracture. Joints were injected with either equine IL-1ra/IGF-1 adenoviral preparation or Gey's balanced salt solution. Sixteen weeks later, defect healing was evaluated macroscopically, histologically, histochemically, and biochemically. Production of IL-1ra and IGF-1 was measured by enzyme-linked immunosorbent assay and radioimmunoassay. We found increased proteoglycan content in treated defects along with augmented Type II collagen associated with substantial transgene expression of IL-1ra during the first 3 weeks. These data suggest in vivo gene therapy can improve biologic processes associated with chondral defect repair.

Chitosan-glycerol phosphate/blood implants increase cell recruitment, transient vascularization and subchondral bone remodeling in drilled cartilage defects

OBJECTIVE

Marrow-stimulation techniques are used by surgeons to repair cartilage lesions although consistent regeneration of hyaline cartilage is rare. We have shown previously that autologous blood can be mixed with a polymer solution containing chitosan in a glycerol phosphate (GP) buffer (chitosan-GP), and that implantation of this polymer/blood composite onto marrow-stimulated chondral defects in rabbit and sheep leads to the synthesis of more chondral repair tissue with greater hyaline character compared to marrow-stimulation alone. In the current study, we examined the modulation of cell recruitment and repair tissue characteristics at early post-surgical time points (from day 1 to 56) in a rabbit model to elucidate potential mechanisms behind this improved repair outcome.

DESIGN

Thirty-three skeletally mature New Zealand White rabbits underwent bilateral arthrotomies, with each trochlea receiving a cartilage defect (3.5 mm x 4.5mm) bearing four microdrill holes (0.9 mm diameter, approximately 4 mm deep) into the subchondral bone. One defect per rabbit was treated with a chitosan-GP/blood implant, while the other defect was left as a microdrilled control. Repair tissues were stained by histochemistry, for collagen types I, II, and X by immunohistochemistry and analyzed using quantitative stereological tools.

RESULTS

Histological analyses demonstrated that control defects followed a typical healing sequence observed previously in marrow-stimulation animal models while chitosan-GP/blood implants led to three significant modifications in the healing sequence at early stages: (1) increased inflammatory and marrow-derived stromal cell recruitment to the microdrill holes, (2) increased vascularization of the provisional repair tissue in the microdrill holes, and (3) increased intramembranous bone formation and subchondral bone remodeling (BR).

CONCLUSIONS

These results suggest that the greater levels of provisional tissue vascularization and BR activity are main factors supporting improved cartilage repair when chitosan-GP/blood implants are applied to marrow-stimulated cartilage lesions.

Effects of calcified cartilage on healing of chondral defects treated with microfracture in horses

BACKGROUND

Microfracture of full-thickness articular defects has been shown to significantly enhance the amount of repair tissue. However, there is a suggestion that leaving calcified cartilage inhibits this repair response.

HYPOTHESIS

Removal of the calcified cartilage with retention of subchondral bone enhances the amount of attachment of the repair tissue compared with retention of the calcified cartilage layer.

STUDY DESIGN

Controlled laboratory study.

METHODS

There were 1-cm(2) articular cartilage defects made in 12 skeletally mature horses on the axial weightbearing portion of both medial femoral condyles. Using a custom measuring device and direct arthroscopic observation of the subchondral bone beneath the calcified cartilage layer, the authors removed the calcified cartilage from 1 defect of each horse. The repair was assessed with arthroscopy, clinical examination, radiographic and magnetic resonance imaging examinations, biopsy at 4 months, gross and histopathologic examinations at 12 months, as well as mRNA and immunohistochemical evaluations.

RESULTS

Removal of calcified cartilage with retention of the subchondral bone plate increased the overall repair tissue as assessed by arthroscopic (4 months) and gross evaluation (12 months). An increase in the level of the subchondral bone was also observed with removal of the calcified cartilage layer. The clinical pain, radiographic examinations, magnetic resonance imaging evaluations, histologic character, matrix proteins, or mRNA expression do not appear to differ based on level of defect debridement.

CLINICAL RELEVANCE

Removal of the calcified cartilage layer appears to provide optimal amount and attachment of repair tissue. Therefore, close arthroscopic visualization is recommended for debridement of clinical lesions to ensure removal of the calcified cartilage layer.

Results after microfracture of full-thickness chondral defects in different compartments in the knee

OBJECTIVE

To determine if the clinical results after microfracture of full-thickness cartilage lesions deteriorate over a period of 36 months.

METHODS

Between 1999 and 2002 85 patients (mean age 39.5 years) with full-thickness cartilage lesions underwent the microfracture procedure and were evaluated preoperatively and 6, 18 and 36 months after surgery. Exclusion criteria were meniscal pathologies, axial malpositioning and ligament instabilities. Baseline clinical scores were compared with follow-up data by paired Wilcoxon-tests for the modified Cincinnati knee and the International Cartilage Repair Society (ICRS)-score. The effects of the lesion localization and Magnetic resonance imaging (MRI) parameters were evaluated using the Pearson correlation and independent samples tests.

RESULTS

Both scores revealed significant improvement 18 months after microfracture (P<0.0001). Within the second 18 months after surgery there was a significant deterioration in the ICRS-score (P<0.0001). The best results could be observed in chondral lesions of the femoral condyles. Defects in other areas of the knee deteriorated between 18 and 36 months after microfracture. MRI 36 months after surgery revealed best defect filling in lesions on the femoral condyles with significant difference in the other areas (P<0.02). The Pearson coefficient of correlation between defect filling and ICRS-score was 0.84 and significant at the 0.01 level.

CONCLUSIONS

Microfracture is a minimal invasive method with good short-term results in the treatment of small cartilage defects. A deterioration of the results starts 18 months after surgery and is most evident in the ICRS-score. The best prognostic factors have young patients with defects on the femoral condyles.

Microfracture and bone morphogenetic protein 7 (BMP-7) synergistically stimulate articular cartilage repair

OBJECTIVE

Microfracture is used to treat articular cartilage injuries, but leads to the formation of fibrocartilage rather than native hyaline articular cartilage. Since bone morphogenetic protein 7 (BMP-7) induces cartilage differentiation, we hypothesized that the addition of the morphogen would improve the repair tissue generated by microfracture. We determined the effects of these two treatments alone and in combination on the quality and quantity of repair tissue formed in a model of full-thickness articular cartilage injury in adolescent rabbits.

DESIGN

Full-thickness defects were made in the articular cartilage of the patellar grooves of forty, 15-week-old rabbits. Eight animals were then assigned to (1) no further treatment (control), (2) microfracture, (3) BMP-7, (4) microfracture with BMP-7 in a collagen sponge (combination treatment), and (5) microfracture with a collagen sponge. Animals were sacrificed after 24 weeks at 39 weeks of age. The extent of healing was quantitated by determining the thickness and the surface area of the repair tissue. The quality of the repair tissue was determined by grading specimens using the International Cartilage Repair Society Visual Histological Assessment Scale.

RESULTS

Compared to controls, BMP-7 alone increased the amount of repair tissue without affecting the quality of repair tissue. Microfracture improved both the quantity and surface smoothness of repair tissue. Compared to either single treatment, the combination of microfracture and BMP-7 increased both the quality and quantity of repair tissue.

CONCLUSIONS

Microfracture and BMP-7 act synergistically to stimulate cartilage repair, leading to larger amounts of repair tissue that more closely resembles native hyaline articular cartilage.

Repair of chronic osteochondral defects in the rat. A bone marrow-stimulating procedure enhanced by cultured allogenic bone marrow mesenchymal stromal cells

Bone marrow mesenchymal stromal cells were aspirated from immature male green fluorescent protein transgenic rats and cultured in a monolayer. Four weeks after the creation of the osteochondral defect, the rats were divided into three groups of 18: the control group, treated with an intra-articular injection of phosphate-buffered saline only; the drilling group, treated with an intra-articular injection of phosphate-buffered saline with a bone marrow-stimulating procedure; and the bone marrow mesenchymal stromal cells group, treated with an intra-articular injection of bone marrow mesenchymal stromal cells plus a bone marrow-stimulating procedure. The rats were then killed at 4, 8 and 12 weeks after treatment and examined. The histological scores were significantly better in the bone marrow mesenchymal stromal cells group than in the control and drilling groups at all time points (p < 0.05). The fluorescence of the green fluorescent protein-positive cells could be observed in specimens four weeks after treatment.

The treatment of articular cartilage defects using the microfracture technique

Chondral defects of the articular surface pose a challenging problem to the orthopedic surgeon. The goal of surgery is to alleviate pain, maximize function, and prevent degenerative changes in the future. A number of techniques have been described to treat these lesions. When considering the treatment options for chondral defects, the surgeon must consider the size, depth, location, and chronicity of the lesion. In addition, the overall alignment of the joint must be evaluated. Prior to treating chondral defects, it is important to understand the indications and contraindications for the microfracture technique. When indicated, the microfracture technique has many advantages over other surgical options. This technique is relatively easy to perform, cost effective, and has low patient morbidity. In addition, the microfracture technique does not burn any long-term bridges, enabling the surgeon to choose a different procedure to revise the chondral defect if the microfracture fails. It is important to understand the mechanism of healing by microfracture, including the effects of the local environment. The postoperative protocol used after the procedure may be as important as the surgery itself. Understanding the science behind the microfracture procedure will lead to better surgical technique and improved outcomes.

Chondral resurfacing of articular cartilage defects in the knee with the microfracture technique. Surgical technique

BACKGROUND

Microfracture is a frequently used technique for the repair of articular cartilage lesions of the knee. Despite the popularity of the technique, prospective information about the clinical results after microfracture is still limited. The purpose of our study was to identify the factors that affect the clinical outcome from this cartilage repair technique.

METHODS

Forty-eight symptomatic patients with isolated full-thickness articular cartilage defects of the femur in a stable knee were treated with the microfracture technique. Prospective evaluation of patient outcome was performed for a minimum follow-up of twenty-four months with a combination of validated outcome scores, subjective clinical rating, and cartilage-sensitive magnetic resonance imaging.

RESULTS

At the time of the latest follow-up, knee function was rated good to excellent for thirty-two patients (67%), fair for twelve patients (25%), and poor for four (8%). Significant increases in the activities of daily living scores, International Knee Documentation Committee scores, and the physical component score of the Short Form-36 were demonstrated after microfracture (p < 0.05). A lower body-mass index correlated with higher scores for the activities of daily living and SF-36 physical component, with the worst results for patients with a body-mass index of >30 kg/m(2). Significant improvement in the activities of daily living score was more frequent with a preoperative duration of symptoms of less than twelve months (p < 0.05). Magnetic resonance imaging in twenty-four knees demonstrated good repair-tissue fill in the defect in thirteen patients (54%), moderate fill in seven (29%), and poor fill in four patients (17%). The fill grade correlated with the knee function scores. All knees with good fill demonstrated improved knee function, whereas poor fill grade was associated with limited improvement and decreasing functional scores after twenty-four months.

CONCLUSIONS

Microfracture repair of articular cartilage lesions in the knee results in significant functional improvement at a minimum follow-up of two years. The best short-term results are observed with good fill grade, low body-mass index, and a short duration of preoperative symptoms. A high body-mass index adversely affects short-term outcome, and a poor fill grade is associated with limited short-term durability.

High-impact athletics after knee articular cartilage repair: a prospective evaluation of the microfracture technique

BACKGROUND

Knee articular cartilage injuries in athletes present a therapeutic challenge and have been identified as an important cause of permanent disability because of the high mechanical joint stresses in athletes.

PURPOSE

To determine whether microfracture treatment of knee articular cartilage injuries can return athletes to high-impact sports and to identify the factors that affect the ability to return to athletic activity.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty-two athletes who regularly participated in high-impact, pivoting sports before articular cartilage injury were treated with microfracture for single articular cartilage lesions of the knee. Functional outcome was prospectively evaluated with a minimum 2-year follow-up by subjective rating, activity-based outcome scores, and the ability for postoperative participation in high-impact, pivoting sports.

RESULTS

At last follow-up, 66% of athletes reported good or excellent results. Activity of daily living, Marx activity rating scale, and Tegner activity scores increased significantly after microfracture. After an initial improvement, score decreases were observed in 47% of athletes. Forty-four percent of athletes were able to regularly participate in high-impact, pivoting sports, 57% of these at the preoperative level. Return to high-impact sports was significantly higher in athletes with age <40 years, lesion size <200 mm(2), preoperative symptoms <12 months, and no prior surgical intervention.

CONCLUSION

Microfracture is an effective first-line treatment to return young athletes with short symptomatic intervals and small articular cartilage lesions of the knee back to high-impact athletics.

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

REASONS FOR PERFORMING STUDY

To improve osteochondral graft reconstruction of subchondral cystic lesions in the medial and lateral femoral condyles by matching the material properties of donor and recipient sites.

OBJECTIVES

To measure biomechanical and biochemical parameters that influence the function and healing of osteochondral grafts used to reconstruct subchondral cystic lesions.

HYPOTHESIS

Suitable donor sites are available within the stifle joint for reconstructing the femoral condyles, despite considerable regional property variation.

METHODS

Fifty-six osteochondral cores were harvested from 6 distal femurs for initial studies that determined subchondral bone modulus of elasticity and ultimate stress. In a second study, 28 osteochondral cores were harvested from 6 distal femurs to measure cartilage aggregate modulus, thickness and sulphated glycosaminoglycan (sGAG) content. Using micro-CT imaging, subchondral bone mineral density and bone volume fraction were also measured. In both studies 2-dimensional contour plots using a bicubic interpolation method and normalised data were generated to allow visual comparison of joint surface characteristics. Statistical comparisons between donor and recipient site raw data were made using an ANOVA for repeated measures with a post hoc Tukey test.

RESULTS

Material properties of cartilage and bone vary considerably over the surface of the stifle joint but the central region of the medial condyle, where subchondral cystic lesions freqdently occur, typically demonstrated bone strength and modulus values of the highest observed. Cartilage thickness and aggregate modulus were highest in the medial femoral condyle and axial aspect of the lateral condyle.

CONCLUSIONS

Material properties of the grafts from the trochlear groove and axial aspect of the lateral trochlear ridge were the closest match for those found in the medial condyle, whereas properties of the lateral condyle were most similar to those found in the trochlear groove and axial aspect of the medial trochlear ridge.

Diagnosis and Treatment of Ligamentous and Meniscal Injuries in the Equine Stifle

The accuracy of the diagnosis of ligamentous and meniscal injuries in the equine stifle has improved significantly in the last 20 years. There are, however, significant limitations in the diagnosis of stifle injuries because of the size and anatomy of the equine stifle. Treatment of soft tissue injuries to the equine stifle has been empirical,with only a few large case studies for specific conditions of stifle ligaments and menisci and only retrospective case studies of the outcome of treatment. This article describes the diagnosis and treatment of ligamentous and meniscal injuries in the equine stifle using information from the author's own experience and from reports in the scientific literature.

Future Directions in Treatment of Joint Disease in Horses

Osteoarthritis is one of the most economically important diseases facing equine practitioners. The loss of use associated with joint disease is a leading problem in the equine industry. Although osteoarthritis in all species is believed to be a multifactorial disease that is not well understood, significant advances are being made. This article presents areas of research that are relatively well developed but have not made it to commercialization or routine clinical practice and looks at new applications being investigated for peo-ple that may have an equine application.

Chitosan-glycerol phosphate/blood implants improve hyaline cartilage repair in ovine microfracture defects

BACKGROUND

Microfracture is a surgical procedure that is used to treat focal articular cartilage defects. Although joint function improves following microfracture, the procedure elicits incomplete repair. As blood clot formation in the microfracture defect is an essential initiating event in microfracture therapy, we hypothesized that the repair would be improved if the microfracture defect were filled with a blood clot that was stabilized by the incorporation of a thrombogenic and adhesive polymer, specifically, chitosan. The objectives of the present study were to evaluate (1) blood clot adhesion in fresh microfracture defects and (2) the quality of the repair, at six months postoperatively, of microfracture defects that had been treated with or without chitosan-glycerol phosphate/blood clot implants, using a sheep model.

METHODS

In eighteen sheep, two 1-cm2 full-thickness chondral defects were created in the distal part of the femur and treated with microfracture; one defect was made in the medial femoral condyle, and the other defect was made in the trochlea. In four sheep, microfracture defects were created bilaterally; the microfracture defects in one knee received no further treatment, and the microfracture defects in the contralateral knee were filled with chitosan-glycerol phosphate/autologous whole blood and the implants were allowed to solidify. Fresh defects in these four sheep were collected at one hour postoperatively to compare the retention of the chitosan-glycerol phosphate/blood clot with that of the normal clot and to define the histologic characteristics of these fresh defects. In the other fourteen sheep, microfracture defects were made in only one knee and either were left untreated (control group; six sheep) or were treated with chitosan-glycerol phosphate/blood implant (treatment group; eight sheep), and the quality of repair was assessed histologically, histomorphometrically, and biochemically at six months postoperatively.

RESULTS

In the defects that were examined one hour postoperatively, chitosan-glycerol phosphate/blood clots showed increased adhesion to the walls of the defects as compared with the blood clots in the untreated microfracture defects. After histological processing, all blood clots in the control microfracture defects had been lost, whereas chitosanglycerol phosphate/blood clot adhered to and was partly retained on the surfaces of the defect. At six months, defects that had been treated with chitosan-glycerol phosphate/blood were filled with significantly more hyaline repair tissue (p < 0.05) compared with control defects. Repair tissue from medial femoral condyle defects that had been treated with chitosan-glycerol phosphate/blood contained more cells and more collagen compared with control defects and showed complete restoration of glycosaminoglycan levels.

CONCLUSIONS

Solidification of a chitosan-glycerol phosphate/blood implant in microfracture defects improved cartilage repair compared with microfracture alone by increasing the amount of tissue and improving its biochemical composition and cellular organization.

A treatment algorithm for the management of articular cartilage defects

The clinical consequences of articular cartilage defects of the knee are pain, swelling, mechanical symptoms, athletic and functional disability, and osteoarthritis. Full thickness articular cartilage defects have a poor capacity to heal. The challenge to restore the articular cartilage surface is multidimensional, faced by basic scientists in the laboratory and orthopedic surgeons in the operating room. This article provides an overview of the contemporary treatment options available for the restoration of articular cartilage defects of the knee.

Evaluation of subchondral bone mineral density associated with articular cartilage structure and integrity in healthy equine joints with different functional demands

OBJECTIVE

To determine and correlate subchondral bone mineral density and overlying cartilage structure and tensile integrity in mature healthy equine stifle (low magnitude loading) and metacarpophalangeal (high magnitude loading) joints.

ANIMALS

8 healthy horses, 2 to 3 years of age.

PROCEDURE

Osteochondral samples were acquired from the medial femoral condyle (FC) and medial trochlear ridge (TR) of the stifle joint and from the dorsal (MC3D) and palmar (MC3P) aspects of the distal medial third metacarpal condyles of the metacarpophalangeal joint. Articular cartilage surface fibrillation (evaluated via India ink staining) and tensile biomechanical properties were determined. The volumetric bone mineral density (vBMD) of the underlying subchondral plate was assessed via dual-energy x-ray absorptiometry.

RESULTS

Cartilage staining (fibrillation), tensile moduli, tensile strength, and vBMD were greater in the MC3D and MC3P locations, compared with the FC and TR locations, whereas tensile strain at failure was less in MC3D and MC3P locations than FC and TR locations. Cartilage tensile moduli correlated positively with vBMD, whereas cartilage staining and tensile strain at failure correlated negatively with vBMD.

CONCLUSIONS AND CLINICAL RELEVANCE

In areas of high joint loading, the subchondral bone had high vBMD and the articular cartilage surface layer had high tensile stiffness but signs of structural wear (fibrillation and low failure strain). The site-dependent variations and relationships in this study support the concept that articular cartilage and subchondral bone normally adapt to physiologic loading in a coordinated way.

Results of microfracture in the treatment of articular cartilage defects of the talus

BACKGROUND

The microfracture technique has been used successfully for the treatment of cartilage defects in the knee. The purpose of this study was to evaluate the microfracture technique in the treatment of osteochondral and degenerative chondral defects of the talus.

METHODS

In a prospective study, 30 ankles in 30 consecutive patients (17 men and 13 women; average age, 41 years; range 20 to 74 years were treated with arthroscopic microfracture. Twenty patients had osteochondral defects and 10 had degenerative chondral defects. Patients were evaluated with clinical examination and MRI preoperatively and at 3, 6, 12, and 24 months postoperatively.

RESULTS

At a mean followup of 2 years (range 22 to 27 months), 29 patients were available for follow-up. The results for all ankles according to the Hannover Scoring System were 45% excellent, 38% good, and 17% satisfactory. Results in patients older than 50 years were not inferior to those in younger patients. Visual Analog Score revealed an average of 8 +/- 2 for pain (preoperatively 3 +/- 2; p < or = 0.001), 8 +/- 2 for function (preoperatively 3 +/- 2; p < or = 0.001) and 8 +/- 2 for satisfaction (preoperatively 2 +/- 2; p < or = 0.001). MRI and arthroscopic assessment suggested the presence of cartilage in the microfractured area.

CONCLUSIONS

At short-term followup, the microfracture technique appeared to repair severe cartilage damage with a good functional outcome. Age was not shown to be a limiting factor.

Marrow stimulation and chondrocyte transplantation using a collagen matrix for cartilage repair

OBJECTIVE

The purpose of the study was to determine whether the implantation of a scaffold would facilitate cartilage repair after microfracture in sheep over a period of 12 months. Furthermore, we investigated the effect of additional autologous cell augmentation of the implanted constructs.

METHODS

Two chondral defects were produced in the medial femoral condyle of sheep without penetrating the subchondral bone. Twenty-seven sheep were divided into the following groups: seven served as untreated controls (Group 1), microfracture was created in 20 animals, seven of them without further treatment (Group 2), in six sheep the defects were additionally covered with a porcine collagen matrix (Group 3), and in seven animals the matrix was augmented with cultured autologous chondrocytes (Group 4). After 4 (11 sheep) and 12 months (16 sheep), the filling of the defects, tissue types, and semiquantitative scores were determined.

RESULTS

The untreated defects revealed the least amount of defect fill. Defects treated with microfractures achieved better defect fill, while the additional use of the matrix did not increase the defect fill. The largest quantity of reparative tissue was found in the cell-augmented group. Semiquantitative scores were best in the cell-augmented group.

CONCLUSION

Microfracture treatment was observed to enhance the healing response. The implantation of a cell-seeded matrix further improved the outcome. The implantation of a collagen matrix alone did not enhance repair. Autologous cell implantation appears to be a very important aspect of the tissue engineering approach to cartilage defects.

Influence of oxygen on the proliferation and metabolism of adipose derived adult stem cells

Articular cartilage is an avascular connective tissue that exhibits little intrinsic capacity for repair. Articular cartilage exists in a reduced oxygen ( approximately 5%) environment in vivo; therefore, oxygen tension may be an important factor that regulates the metabolism of chondrocyte progenitors. A number of recent studies have developed tissue engineering approaches for promoting cartilage repair using undifferentiated progenitor cells seeded on biomaterial scaffolds, but little is known about how oxygen might influence these engineered tissues. Human adipose-derived adult stem (hADAS) cells isolated from the stroma of subcutaneous fat were suspended in alginate beads and cultured in control or chondrogenic media in either low oxygen (5%) or atmospheric oxygen tension (20%) for up to 14 days. Under chondrogenic conditions, low oxygen tension significantly inhibited the proliferation of hADAS cells, but induced a two-fold increase in the rate of protein synthesis and a three-fold increase in total collagen synthesis. Low oxygen tension also increased glycosaminoglycan synthesis at certain timepoints. Immunohistochemical analysis showed significant production of cartilage-associated matrix molecules, including collagen type II and chondroitin-4-sulfate. These findings suggest oxygen tension may play an important role in regulating the proliferation and metabolism of hADAS cells as they undergo chondrogenesis, and the exogenous control of oxygen tension may provide a means of increasing the overall accumulation of matrix macromolecules in tissue-engineered cartilage.

Cartilage regeneration using mesenchymal stem cells and a three-dimensional poly-lactic-glycolic acid (PLGA) scaffold

Cartilage engineered from mesenchymal stem cells (MSCs) requires a scaffold to keep the cells in the cartilage defect and to act as a support for inducing hyaline cartilage formation. We developed a novel three-dimensional special poly-lactic-glycolic acid (PLGA) scaffold that provided structural support and stimulated repair. Three-dimensional PLGA scaffolds seeded with cultured MSCs were transplanted into large defects in rabbit knees and analyzed histologically at 4 and 12 weeks after the operation. Our findings showed that in the engineered cartilage with the PLGA scaffold, the defects were filled with smooth, shiny white tissue macroscopically and hyaline-like cartilage histologically at 12 weeks after the transplantation. The structure of the novel PLGA scaffolds provided architectural support for the differentiation of progenitor cells and demonstrated successful induction of in vivo chondrogenesis.

Arthroscopic microfracture treatment for osteonecrosis of the knee

PURPOSE

This study evaluated the results of arthroscopic subchondral microfracture performed on patients with spontaneous osteonecrosis (ON) (group 1) or secondary ON (group 2) of the knee joint.

TYPE OF STUDY

Retrospective clinical study.

METHODS

Group 1 included 26 patients (mean age, 48 years) who had spontaneous ON. Group 2 included 15 patients (mean age, 32 years) with ON secondary to inflammatory disease or steroid therapy. Seventy-six percent of the chondral defects were located in the medial femoral condyle. The average defect sizes in group 1 was 162 mm2 and in group 2 was 362 mm2. After debridement of the necrotic tissues, multiple perforations were placed into the subchondral bone to obtain revascularization.

RESULTS

There was an increase in the average Lysholm scores from 57 to 90 in group 1 after 27 months of mean follow-up (P < .05); 71% of patients could participate in strenuous sports with no or minimal limitation. The mean activity level in group 1 according to Cincinnati Knee Rating System was 6 preoperatively and 13.54 postoperatively. For group 2, the average scores showed significant improvement and patient satisfaction after surgery (preoperative and postoperative average Lysholm scores were 41 and 75, respectively, with mean follow-up of 37 months). Average activity level in group 2 increased from 2.67 to 11.73. Control magnetic resonance imaging scans of the cases revealed the continuity of normal cartilage with cartilage-like tissue in the treated areas. However, an increase of the size of ON in the subchondral bone was detected in 27% of the knees.

CONCLUSIONS

The microfracture technique is safe, simple, and cost-effective, and may be an alternative procedure for treatment of ON of the knee, especially in young patients, before possible subsequent replacement surgery.

LEVEL OF EVIDENCE

Level IV.

Repair of articular cartilage defects treated by microfracture and a three-dimensional collagen matrix

The objective of our study was to evaluate the behavior of ovine chondrocytes and bone marrow stromal cells (BMSC) on a matrix comprising type-I, -II, and -III collagen in vitro, and the healing of chondral defects in an ovine model treated with the matrix, either unseeded or seeded with autologous chondrocytes, combined with microfracture treatment. For in vitro investigation, ovine chondrocytes and BMSC were seeded on the matrix and cultured at different time points. Histological analysis, immunohistochemistry, biochemical assays for glycosaminoglycans, and real-time quantitative PCR for collagens were performed. The animal study described here included 22 chondral defects in 11 sheep, divided into four treatment groups. Group A: microfracture and collagen matrix seeded with chondrocytes; B: microfracture and unseeded matrices; C: microfracture; D: untreated defects. All animals were sacrificed 16 weeks after implantation, and a histomorphometrical and qualitative evaluation of the defects was performed. The in vitro investigation revealed viable cells up to 3 weeks; chondrocytes had a predominantly round morphology, produced glycosaminoglycans, and expressed both collagen markers, whereas BMSC stained positive for antibodies against type-II collagen; however, no mRNA for type-II collagen was amplified. All treatment groups of the animal model showed better defect filling compared to untreated knees. The cell-seeded group had the greatest quantity of repair tissue and the largest quantity of hyaline-like tissue. Although the collagen matrix is an adequate environment for BMSC in vitro, the additionally implanted unseeded collagen matrix did not increase the repair response after microfracture in chondral defects. Only the matrices seeded with autologous cells in combination with microfracture were able to facilitate the regeneration of hyaline-like cartilage.

Chondral defect repair after the microfracture procedure: a nonhuman primate model

BACKGROUND

The extent and time course of chondral defect healing after microfracture in humans are not well described. Although most physicians recommend a period of activity and weightbearing restriction to protect the healing cartilage, there are limited data on which to base decisions regarding the duration of such restrictions.

HYPOTHESIS

Evaluation of the status of chondral defect repair at different time points after microfracture in a primate model may provide a rationale for postoperative activity recommendations.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Full-thickness chondral defects created on the femoral condyles and trochlea of 12 cynomolgus macaques were treated with microfracture and evaluated by gross and histologic examination at 6 and 12 weeks.

RESULTS

At 6 weeks, there was limited chondral repair and ongoing resorption of subchondral bone. By 12 weeks, the defects were completely filled and showed more mature cartilage and bone repair.

CONCLUSION

In the primate animal model, significant improvements in the extent and quality of cartilage repair were observed from the 6- to 12-week time points after microfracture.

CLINICAL RELEVANCE

The poor status of the defect repair at 6 weeks and the ongoing healing observed from the 6- to 12-week time points may indicate that the repair is vulnerable during this initial postoperative period. Assuming the goal of postoperative weightbearing and activity restriction in patients after microfracture is to protect immature repair tissue, this study lends support to extending such recommendations longer than 6 weeks.

Cartilage restoration, part 2: techniques, outcomes, and future directions

In part 1 of this 2-part Current Concepts article, the authors reviewed the basic science of normal articular and meniscal cartilage and its response to injury. They reviewed the historical perspectives and basic science behind these various methods and presented a rationale for patient evaluation, treatment selection, and timing. In part 2, the authors review the specific indications for the treatment of chondral injuries and describe the techniques and outcomes of the various treatment options, including palliative, reparative, and restorative procedures. In addition, they will examine specific complex clinical scenarios emphasizing treatment options of comorbid conditions including ligament instability, meniscal deficiency, and malalignment. A limited review of the application of these techniques in joints other than the knee will also be presented. A conceptual algorithm is developed to assist in clinical decision making.

Arthroscopic findings in horses with subtle radiographic evidence of osteochondral lesions of the medial femoral condyle: 15 cases (1995–2002)

OBJECTIVE

To determine arthroscopic findings in lame horses with subtle radiographic lesions of the medial femoral condyle.

DESIGN

Retrospective study.

ANIMALS

15 horses examined because of lameness that had subtle radiographic evidence of osteochondral lesions involving the medial femoral condyle in at least 1 joint.

PROCEDURE

Medical records were reviewed, and results of physical examination, radiography, and arthroscopy were recorded. Follow-up information was obtained through reexamination of the horses or telephone conversations with the referring veterinarians, owners, or trainers.

RESULTS

Lameness severity ranged from grade 1 to 3 on a scale from 0 to 5. Radiography and arthroscopy were performed on 28 stifle joints. The 4 unaffected joints in 4 horses with unilateral hind limb lameness that underwent bilateral arthroscopy had no radiographic lesions, but 2 of the 4 had arthroscopic lesions. Of the remaining 24 joints, 20 had radiographic evidence of flattening of the apex of the medial femoral condyle and 4 had minimal subchondral lucency. Lesions were identified arthroscopically in 18 of the 20 joints with flattening of the condyle and in all 4 joints with subchondral lucency. Treatment consisted of abrasion arthroplasty or microfracture. Seven of the 9 horses with focal cartilage lesions and 2 of the 6 horses with generalized cartilage lesions were reportedly sound without any evidence of joint effusion at the time of final follow-up.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that horses with hind limb lameness and subtle radiographic lesions of the medial femoral condyle are likely to have arthroscopically apparent cartilage lesions and subchondral bone defects.

[Microfracture technique for treatment of osteochondral and degenerative chondral lesions of the talus. 2-year results of a prospective study]

The microfracture technique has become an established method for the treatment of chondral lesions in the knee. The aim of this study was to determine its usefulness in the treatment of osteochondral (OCL) and degenerative chondral lesions (DCL) of the talus. In a prospective study, 32 patients with an osteochondral lesion (22 patients) or degenerative chondral lesion (10 patients) were operated arthroscopically and treated with the microfracture technique. All patients were evaluated preoperatively as well as 3, 6, 12, and 24 months postoperatively with the Hannover scoring system and a visual analog score (VAS). MRI scans were performed at all points. Statistical analyses were performed using the Wilcoxon sign rank-sum test with a level of significance of p < or = 0.05. At a mean follow-up of 2 years (range: 22-27 months), 23 patients (14 OCL, 9 DCL) were available for follow-up. The average age of the 17 male and 15 female patients at the time of operation was 39 years (range: 16-74 years). The results according to the Hannover scoring system were 43% excellent, 35% good, and 22% satisfactory with 93% excellent or good results for OCL. Older patients (>50 years, n=8) had slightly better results than younger patients. VAS revealed an average of 7.84 (preoperative: 3.53) for pain, 7.85 for function (preoperative; 3.38), and 7.78 for satisfaction (preoperative: 2.41). MRI and arthroscopic assessment showed a visible regeneration of the cartilage in the microfractured area. In a short-term follow-up, the microfracture technique has proven to restore severe cartilage damage with a good functional outcome. Age is not a limiting factor. However, longer-term results remain to be evaluated.

Chondrocyte survival and material properties of hypothermically stored cartilage: an evaluation of tissue used for osteochondral allograft transplantation

BACKGROUND

There is little information available on the material properties of hypothermically stored allograft specimens used to repair osteochondral defects.

PURPOSE

To analyze the effect of hypothermic storage on the material properties of fresh knee specimens over a 60-day interval.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve sheep knee condyles were isolated. The femoral and tibial condyles and the patella were stored in a nutritive medium containing Dulbecco's Modified Eagle's Medium for 1, 8, 15, 29, 45, or 60 days. Total chondrocyte density, chondrocyte viability, matrix proteoglycan content, matrix water content, and matrix dynamic modulus of elasticity were determined.

RESULTS

Mean chondrocyte viability decreased significantly over the storage interval: 100% (day 1), 98.2% (day 8), *80.2% (day 15), *80.6% (day 29), *64.6% (day 45), and *51.6% (day 60) (* P < 0.05). Qualitative analysis demonstrated a preponderance of nonviable chondrocytes in the superficial cartilage layer. Significant decreases in matrix proteoglycan were observed in day 15 through day 60 specimens (P < 0.05). The matrix dynamic modulus significantly decreased from day 1 through day 60 (P < 0.05).

CONCLUSION

The material properties of hypothermically stored knee condyles progressively decline over 60 days.

CLINICAL RELEVANCE

This observed decline may have significant ramifications on long-term graft survival following stored-allograft implantation.

Cylindrical press-fit osteochondral allografts for resurfacing the equine metatarsophalangeal joint

OBJECTIVE

To investigate the feasibility of resurfacing the equine fetlock joint using cylindrical, orthotopic, press-fit, osteochondral allografts.

STUDY DESIGN

Experimental study.

ANIMALS

Ten mature, mixed-breed horses.

METHODS

Cylindrical, osteochondral grafts (6.5-mm diameter) were harvested aseptically from cadaveric equine metatarsophalangeal joints. Allografts were transplanted into 6 horses; 4 horses were sham operated. The surgical approach involved creation of a bone block at the origin of the medial collateral ligament and luxation of the metatarsophalangeal joint. Grafts were placed into the medial and lateral metatarsal condyles. Radiographs were taken at 8 and 25 weeks, and lameness was evaluated at 25 weeks. Horses were killed at 25 weeks. Analyses included gross evaluation, microradiography, paravital staining, light microscopy, and cartilage biochemistry.

RESULTS

No complications occurred that could be attributed to the surgical procedure. Graft congruency with the surrounding articular cartilage was fair to excellent. Two horses were sound at 25 weeks. Most grafts had more than 90% articular cartilage coverage, and histologic and microradiographic analysis revealed good graft incorporation and articular cartilage survival. Sulphated glycosaminoglycan concentration was decreased in grafted tissue.

CONCLUSIONS

We attribute the viability of osteochondral allografts in the equine fetlock to adequate congruency, stable graft fixation, and the use of orthotopic tissue. Host response to the allograft bone tissue did not affect cartilage viability.

CLINICAL RELEVANCE

Before clinical use, improvements to instrumentation are required that would decrease damage to grafts and minimize technique-associated incongruencies of the articular surface at the time of grafting. Larger grafts would also likely be required to resurface a greater surface area.

Outcomes of microfracture for traumatic chondral defects of the knee: average 11-year follow-up

PURPOSE

In this study, we measured functional outcomes of patients treated arthroscopically with microfracture for full-thickness traumatic defects of the knee.

TYPE OF STUDY

A case series of patients with 7 to 17 years' follow-up.

METHODS

Between 1981 and 1991, a total of 72 patients (75 knees) met the following inclusion criteria: (1) traumatic full-thickness chondral defect, (2) no meniscus or ligament injury, and (3) age 45 years and younger (range, 13 to 45 years). Seventy-one knees (95%) were available for final follow-up (range, 7 to 17 years). All patients completed self-administered questionnaires preoperatively and postoperatively.

RESULTS

The following results were significant at the P <.05 level. Significant improvement was recorded for both Lysholm (scale 1 to 100; preoperative, 59; final follow-up, 89) and Tegner (1 to 10; preoperative, 3; final follow-up, 6) scores. At final follow-up, the SF-36 and WOMAC scores showed good to excellent results. At 7 years after surgery, 80% of the patients rated themselves as "improved." Multivariate analysis revealed that age was a predictor of functional improvement.

CONCLUSIONS

Over the 7- to 17-year follow-up period (average, 11.3 years), patients 45 years and younger who underwent the microfracture procedure for full-thickness chondral defects, without associated meniscus or ligament pathology, showed statistically significant improvement in function and indicated that they had less pain.

Changes in subchondral bone in cartilage resurfacing--an experimental study in sheep using different types of osteochondral grafts

OBJECTIVE

This article addresses the subchondral bone integrity in cartilage resurfacing by comparing fresh, untreated auto-, xeno-, and photooxidized osteochondral allo- and xenografts. Photooxidation was expected to improve mechanical stability of the osteochondral grafts through an improved linkage of the collagen fibers within the bone matrix.

DESIGN

Untreated auto- and xenografts and with photooxidation pretreated allo- and xenografts were surgically implanted in femoral condyles of sheep (n=40). After 2, 6, 12 and 18 months results were evaluated histologically using non-decalcified bone embedded in acrylic resin. Qualitative evaluation was performed with emphasis on bone matrix, biomechanical stability of graft anchorage, formation of cystic lesions, and bone resorption and formation. Quantitative evaluation of the total subchondral bone area was conducted histomorphometrically. Statistical analysis (factorial ANOVA test) was used to compare differences between groups with respect to the percentage of bone matrix and fibrous tissue per section.

RESULTS

Subchondral bone resorption was fastest in untreated, fresh autografts, followed by photooxidized allografts, untreated, fresh xenografts and last pretreated photooxidized xenografts. Cystic lesions were seen in all types of grafts, but were most pronounced at 6 months in autografts and least in photooxidized grafts. Cyst-like lesions had subsided substantially in the untreated auto- and photooxidized xenografts, if no graft dislocation occurred during the healing period. Mononuclear cell infiltration and an increase in the presence of multinuclear cells were observed at 2 months, mostly in untreated autografts, followed by photooxidized allo- and untreated xenografts. They were much higher in numbers compared to photooxidized grafts, at least in the early specimens at 2 months. Graft stability was linked to the rate of bone resorption.

CONCLUSION

Substantial resorption of the subchondral bone, involving the development of cyst-like lesions, lead to dislocation and finally to cartilage matrix degradation of the grafts. The process of photooxidation decreased the speed of bone resorption in osteochondral grafts and, thus, improved graft stability and cartilage survival. These results suggest that the remodeling of the subchondral bone of the host and the graft within the first 6 months is an important factor in graft stability and overall results of cartilage resurfacing.

MR imaging of cartilage repair procedures

It is becoming increasingly important for the radiologist to evaluate the appearance and outcome of cartilage repair procedures. MR imaging is currently the best method for such evaluation but it is necessary to use cartilage-specific sequences and to modify those sequences when necessary to minimize artifacts from retained metal within the joint. This article reviews the surgical technique of the more commonly performed cartilage repair procedures, currently recommended techniques for the MR imaging evaluation of articular cartilage and cartilage repair procedures, and the MR imaging appearance of cartilage repair procedures and of the most frequently encountered complications following such procedures.

Early events in cartilage repair after subchondral bone microfracture

The current study investigated healing of large full-thickness articular cartilage defects during the first 8 weeks with and without penetration of the subchondral bone using microfracture in an established equine model of cartilage healing. Chondral defects in the weightbearing portion of the medial femoral condyle were made bilaterally; one defect in each horse was microfractured whereas the contralateral leg served as the control. The expression of cartilage extracellular matrix components (Types I and II collagen and aggrecan) was evaluated using histologic techniques, reverse transcription coupled polymerase chain reaction, in situ hybridization, and immunohistochemistry. This study confirms an increase in Type II collagen mRNA expression in repair tissue as early as 6 weeks after microfracture. Although other matrix mRNA and protein levels changed in concentration and tissue location over the course of the study, no significant differences were seen in microfractured defects. Although the microfracture techniques appear to improve clinical functionality, volume of repair tissue, and augment Type II collagen content, aggrecan content is less than ideal. Therefore, methods to enhance key matrix components such as aggrecan after microfracture may additionally improve repair tissue observed after the procedure.

Managing chronic arthritis

Many compounds are being investigated for the control of symptoms of osteoarthritis in people and animals. Ideally, treatment should include analgesia, inflammation control, and chondroprotection. With further progress in this area, combination therapies tailored to the needs of the individual animal should enable us to maximize efficacy and minimize side effects. Only a few of the newer therapies and pharmaceutic agents have been investigated in the horse, however. With more rigorous investigation, they may be determined to be ineffective or unsafe. Meanwhile, as much information should be gathered from manufacturers as possible so as to ensure that appropriate recommendations are made.