Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein

Calcification of the extracellular matrix (ECM) can be physiological or pathological. Physiological calcification occurs in bone when the soft ECM is converted into a rigid material capable of sustaining mechanical force; pathological calcification can occur in arteries and cartilage and other soft tissues. No molecular determinant regulating ECM calcification has yet been identified. A candidate molecule is matrix GLA protein (Mgp), a mineral-binding ECM protein synthesized by vascular smooth-muscle cells and chondrocytes, two cell types that produce an uncalcified ECM. Mice that lack Mgp develop to term but die within two months as a result of arterial calcification which leads to blood-vessel rupture. Chondrocytes that elaborate a typical cartilage matrix can be seen in the affected arteries. Mgp-deficient mice additionally exhibit inappropriate calcification of various cartilages, including the growth plate, which eventually leads to short stature, osteopenia and fractures. These results indicate that ECM calcification must be actively inhibited in soft tissues. To our knowledge, Mgp is the first inhibitor of calcification of arteries and cartilage to be characterized in vivo.

Cell origin and differentiation in the repair of full-thickness defects of articular cartilage

The origin and differentiation of cells in the repair of three-millimeter-diameter, cylindrical, full-thickness drilled defects of articular cartilage were studied histologically in New Zealand White rabbits. The animals were allowed to move freely after the operation. Three hundred and sixty-four individual defects from 122 animals were examined as long as forty-eight weeks postoperatively. In the first few days, fibrinous arcades were established across the defect, from surface edge to surface edge, and this served to orient mesenchymal cell ingrowth along the long axes. The first evidence of synthesis of a cartilage extracellular matrix, as defined by safranin-O staining, appeared at ten days. At two weeks, cartilage was present immediately beneath the surface of collagenous tissue that was rich in flattened fibrocartilaginous cells in virtually all specimens. At three weeks, the sites of almost all of the defects had a well demarcated layer of cartilage containing chondrocytes. An essentially complete repopulation of the defects occurred at six, eight, ten, and twelve weeks, with progressive differentiation of cells to chondroblasts, chondrocytes, and osteoblasts and synthesis of cartilage and bone matrices in their appropriate locations. At twenty-four weeks, both the tidemark and the compact lamellar subchondral bone plate had been re-established. The cancellous woven bone that had formed initially in the depths of the defect was replaced by lamellar, coarse cancellous bone. Autoradiography after labeling with 3H-thymidine and 3H-cytidine demonstrated that chondrocytes from the residual adjacent articular cartilage did not participate in the repopulation of the defect. The repair was mediated wholly by the proliferation and differentiation of mesenchymal cells of the marrow. Intra-articular injections of 3H-thymidine seven days after the operation clearly labeled this mesenchymal cell pool. The label, initially taken up by undifferentiated mesenchymal cells, progressively appeared in fibroblasts, osteoblasts, articular chondroblasts, and chondrocytes, indicating their origin from the primitive mesenchymal cells of the marrow. Early traces of degeneration of the cartilage matrix were seen in many defects at twelve to twenty weeks, with the prevalence and intensity of the degeneration increasing at twenty-four, thirty-six, and forty-eight weeks. Polarized light microscopy demonstrated failure of the newly synthesized repair matrix to become adherent to, and integrated with, the cartilage immediately adjacent to the drill-hole, even when light microscopy had shown apparent continuity of the tissue. In many instances, a clear gap was seen between repair and residual cartilage.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of cytokines in cartilage matrix degeneration in osteoarthritis

Chondrocytes are the single cellular component of hyaline cartilage. Under physiologic conditions, they show steady-state equilibrium between anabolic and catabolic activities that maintains the structural and functional integrity of the cartilage extracellular matrix. Implicit in the loss of cartilage matrix that is associated with osteoarthritis is that there is a disturbance in the regulation of synthetic (anabolic) and resorptive (catabolic) activities of the resident chondrocytes that results in a net loss of cartilage matrix components and deterioration in the structural and functional properties of the cartilage. Multiple mechanisms likely are involved in the disturbance of chondrocyte remodeling activities in OA. They include the development of acquired or age-related alterations in chondrocyte function, the effects of excessive mechanical loading, and the presence of dysregulated cytokine activities. Cytokines are soluble or cell-surface molecules that play an essential role in mediating cell-cell interactions. It is possible to classify the cytokines that regulate cartilage remodeling as catabolic, acting on target cells to increase products that enhance matrix degradation; as anticatabolic, tending to inhibit or antagonize the activity of the catabolic cytokines; and as anabolic, acting on chondrocytes to increase synthetic activity. This review will focus on the role of proinflammatory cytokines and their roles in mediating the increased matrix degradation that characterizes the osteoarthritic cartilage lesion.

Synovitis: a potential predictive factor of structural progression of medial tibiofemoral knee osteoarthritis -- results of a 1 year longitudinal arthroscopic study in 422 patients

OBJECTIVE

To evaluate the prevalence of synovitis in painful medial tibiofemoral knee osteoarthritis (OA) and to evaluate correlation between synovitis and the structural severity and progression of tibiofemoral cartilage damage.

STUDY

Multicenter, longitudinal, 1-year duration.

PATIENTS

Primary painful knee OA (ACR criteria) of the medial tibiofemoral compartment, with pain of the signal knee on at least 30 days in the past 2 months, medial joint space width > or = 2mm, at least 10% of one cartilage surface of the medial compartment affected by superficial fibrillation or worse at baseline arthroscopy. ARTHROSCOPIC PARAMETERS: Knee arthroscopy under local anesthesia was performed and videorecorded at entry and after 1 year. Medial chondropathy was scored by using Societe Francaise d'Arthroscopie (SFA) score (0-100) and reader's overall assessment (VAS score, 100 mm). Progression of medial chondropathy was defined by a change in SFA and VAS scores over 4.5 and 8.0 mm after 1 year, respectively. Medial perimeniscal synovium was scored as normal (few translucent and slender villi, fine vascular network), reactive (proliferation of opaque villi), or inflammatory (hypervascularization and/or proliferation of hypertrophic and hyperemic villi). Medial chondropathy and synovitis were scored by a single reader blind to chronology of paired videotapes.

RESULTS

Four hundred and twenty-two patients were enrolled (mean age: 61 years, females: 59%, body mass index: 31, mean disease duration: 4 years) and completed the 1-year study. Synovial abnormalities were present in 50% of the patients with reactive and inflammatory aspects in 29% and 21% of the patients, respectively. Patients with a reactive or inflammatory medial synovium had a more severe medial chondropathy. The worsening in medial chondropathy after 1 year was statistically more severe in the group of patients with an inflammatory perimeniscal synovial membrane at baseline compared to patients with normal and reactive aspects, with no difference between these two latter groups. The odds ratio for progression in VAS score after 1 year was 3.11 (95% CI [1.07, 5.69]) for patients with inflammatory synovium at baseline compared to patients with normal synovium.

CONCLUSIONS

This study suggests that abnormalities of the medial perimeniscal synovium are a common feature of painful medial knee OA, associated with more severe medial chondropathy. It also suggests that an inflammatory aspect of the medial perimeniscal synovium could be considered as a predictive factor of subsequent increased degradation of medial chondropathy.

The microfracture technique for the treatment of articular cartilage lesions in the knee. A prospective cohort study

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.

A system for grading articular cartilage lesions at arthroscopy

Although there are several different classification systems for the description of articular cartilage damage, each has certain limitations and deficiencies which can lead to confusion. We are proposing a new system which describes articular cartilage abnormalities in simple terms. It is based on four separate and distinct variables: the description of the articular surface, the extent (depth) of involvement, the diameter of the lesion, and the location of the lesion. Although somewhat qualitative and subjective, the system enables the surgeon to record observed articular cartilage changes. We have used this grading as part of our overall knee rating system and have found it helpful in comparing treatment results between our different studies. For research purposes, a point scaling system facilitates computerization and statistical analysis of the data.

Matrix-associated autologous chondrocyte transplantation/implantation (MACT/MACI)--5-year follow-up

Matrix-associated autologous chondrocyte transplantation/implantation (MACT/MACI) is a new operation procedure using a cell seeded collagen matrix for the treatment of localized full-thickness cartilage defects. A prospective clinical investigation was carried out in order to clarify whether this proves suitable and confirms objective and subjective clinical improvement over a period of up to 5 years after operation. Thirty-eight patients with localised cartilage defects were treated with MACT. Within the context of clinical follow-up, these patients were evaluated for up to 5 years after the intervention. Four different scores (Meyers score, Tegner-Lysholm activity score, Lysholm-Gillquist score, ICRS score) as well as the results of six arthroscopies and biopsies obtained from four patients formed the basis of this study. For 15 patients, 5 or more years had elapsed since the operation at the time this study was completed. It was possible to obtain results 5 years postoperatively from 11 (73.3%) of these 15 patients. Overall, we included 25 patients into the evaluation with a 2-year or longer postoperative period. Five years after transplantation 8 out of 11 patients rated the function of their knee as much better or better than before. Three of the four scores showed significant improvement compared to the preoperative value. One score, the Tegner-Lysholm score showed improvement, which, however, did not prove to be significant. The significantly improved results on three scores after 5 years suggest that MACT represents a suitable but cost-intensive alternative in the treatment of local cartilage defects in the knee.

Tissue engineering and cell therapy of cartilage and bone

Trauma and disease of bones and joints, frequently involving structural damage to both the articular cartilage surface and the subchondral bone, result in severe pain and disability for millions of people worldwide and represent major challenges for the orthopedic surgeons. Therapeutic repair of skeletal tissues by tissue engineering has raised the interest of the scientific community, providing very promising results in preclinical animal models and clinical pilot studies. In this review, we discuss this approach. The choice of a proper cell type is addressed. The use of terminally differentiated cells, as in the case of autologous chondrocyte implantation, is compared with the advantages/disadvantages of using more undifferentiated cell types, such as stem cells or early mesenchymal progenitors that retain multi-lineage and self-renewal potentials. The need for proper scaffold matrices is also examined, and we provide a brief overview of their fundamental properties. A description of the natural and biosynthetic materials currently used for reconstruction purposes, either of cartilage or bone, is given. Finally, we highlight the positive aspects and the remaining problems that will drive future research in articular cartilage and bone repair.

The clinical importance of meniscal tears demonstrated by magnetic resonance imaging in osteoarthritis of the knee

BACKGROUND

Meniscal tears are frequently found during magnetic resonance imaging of osteoarthritic knees. However, the prevalence and clinical relevance of these tears have not been determined. This study was designed to investigate the relationship between meniscal tears and osteoarthritis and between such tears and pain in patients with osteoarthritis.

METHODS

Magnetic resonance imaging and plain radiography of the knee were performed in a group of 154 patients with clinical symptoms of knee osteoarthritis and a group of forty-nine age-matched asymptomatic controls. Pain scores (according to a 100-mm visual analog scale) and functional scores (according to the Western Ontario and McMaster University Osteoarthritis Index [WOMAC]) were determined for ninety-one of the patients with symptomatic osteoarthritis. Meniscal tears were defined as tears extending to an articular surface as seen on magnetic resonance imaging.

RESULTS

A medial or lateral meniscal tear was a very common finding in the asymptomatic subjects (prevalence, 76%) but was more common in the patients with symptomatic osteoarthritis (91%) (p < 0.005). In the group with symptomatic osteoarthritis, a higher Kellgren-Lawrence radiographic grade was correlated with a higher frequency of meniscal tears (r = 0.26, p < 0.001), and men had a higher prevalence of meniscal tears than did women (p < 0.01). However, there was no significant difference with regard to the pain or WOMAC score between the patients with and those without a medial or lateral meniscal tear in the osteoarthritic group (p = 0.8 to 0.9 for all comparisons). The power of the study was 80% to detect a difference in the WOMAC scores of 15 points and a difference in the scores on the visual analog scale of 16 mm.

CONCLUSIONS

Meniscal tears are highly prevalent in both asymptomatic and clinically osteoarthritic knees of older individuals. However, osteoarthritic knees with a meniscal tear are not more painful than those without a tear, and the meniscal tears do not affect functional status. These data do not support the routine use of magnetic resonance imaging for the evaluation and management of meniscal tears in patients with osteoarthritis of the knee.

LEVEL OF EVIDENCE

Diagnostic study, Level I-1 (testing of previously developed diagnostic criteria in series of consecutive patients [with universally applied reference "gold" standard]). See p. 2 for complete description of levels of evidence.

Meniscal allograft transplantation: long-term clinical results with radiological and magnetic resonance imaging correlations

Long-term data on the clinical outcome and the fate of the meniscus allograft after transplantation are scarce. In this study we present the clinical, radiological and MRI outcome of the meniscus graft and the articular cartilage after 42 meniscus allograft transplantations in 41 patients with a minimum follow-up of 10 years. A total of 27 medial and 15 lateral meniscal allografts were transplanted. Eleven of the medial allograft procedures were associated with a high tibial osteotomy. The patients were evaluated clinically at the time of transplantation and at the final follow-up using the modified HSS scoring system. The knee injury and osteoarthritis outcome score (KOOS) was used as an evaluation tool for patient-related outcome at the final follow-up. Joint space width narrowing and Fairbank changes were radiological outcome parameters, which were available for 32 patients. Femoral and tibial cartilage degeneration, graft extrusion and signal intensity were scored on MRI scans obtained in 17 patients approximately 1 year after transplantation and at the final follow-up (>10 years). For statistical analysis the patients were divided into three groups: lateral meniscal allograft (LMT), medial meniscal allograft transplantation with a high tibial osteotomy (MMT+HTO) and without (MMT). The modified HSS score revealed a significant improvement in pain and function at the final follow-up for all groups. Further analysis also revealed that an MMT+HTO procedure resulted in a greater improvement at the final follow-up when compared to MMT. Nonetheless, the KOOS scores obtained at the final follow-up revealed the presence of substantial disability and symptoms, in addition to a reduced quality of life. Radiographical analysis revealed no further joint space narrowing in 13/32 knees (41%). Fairbank changes remained stable in 9/32 knees (28%). MRI analysis showed no progression of cartilage degeneration in 6/17 knees (35%). An increased signal intensity of the allograft was present, as was partial graft extrusion in the majority of patients at the final follow-up. Seven cases had to be converted to a total knee arthroplasty during the follow-up; the overall failure rate was 18%. Long-term results after viable meniscus allograft transplantation are encouraging in terms of pain relief and improvement of function. Despite this significant improvement, substantial disability and symptoms were present in all investigated subgroups. Progression of further cartilage degeneration or joint space narrowing was absent in a considerable number of cases, indicating a potential chondroprotective effect. Level of evidence is therapeutic study, Level IV and retrospective analysis of prospectively collected data.

Injectable mesenchymal stem cell therapy for large cartilage defects--a porcine model

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

T2 and T1rho MRI in articular cartilage systems

T2 and T1rho have potential to nondestructively detect cartilage degeneration. However, reports in the literature regarding their diagnostic interpretation are conflicting. In this study, T2 and T1rho were measured at 8.5 T in several systems: 1) Molecular suspensions of collagen and GAG (pure concentration effects): T2 and T1rho demonstrated an exponential decrease with increasing [collagen] and [GAG], with [collagen] dominating. T2 varied from 90 to 35 ms and T1rho from 125 to 55 ms in the range of 15-20% [collagen], indicating that hydration may be a more important contributor to these parameters than previously appreciated. 2) Macromolecules in an unoriented matrix (young bovine cartilage): In collagen matrices (trypsinized cartilage) T2 and T1rho values were consistent with the expected [collagen], suggesting that the matrix per se does not dominate relaxation effects. Collagen/GAG matrices (native cartilage) had 13% lower T2 and 17% lower T1rho than collagen matrices, consistent with their higher macromolecular concentration. Complex matrix degradation (interleukin-1 treatment) showed lower T2 and unchanged T1rho relative to native tissue, consistent with competing effects of concentration and molecular-level changes. In addition, the heterogeneous GAG profile in these samples was not reflected in T2 or T1rho. 3) Macromolecules in an oriented matrix (mature human tissue): An oriented collagen matrix (GAG-depleted human cartilage) showed T2 and T(1rho) variation with depth consistent with 16-21% [collagen] and/or fibril orientation (magic angle effects) seen on polarized light microscopy, suggesting that both hydration and structure comprise important factors. In other human cartilage regions, T2 and T1rho abnormalities were observed unrelated to GAG or collagen orientation differences, demonstrating that hydration and/or molecular-level changes are important. Overall, these studies illustrate that T2 and T1rho are sensitive to biologically meaningful changes in cartilage. However, contrary to some previous reports, they are not specific to any one inherent tissue parameter.

Development and reversal of a proteoglycan aggregation defect in normal canine knee cartilage after immobilization

Healthy adult dogs were studied for a defect in proteoglycan aggregation by immobilizing one limb for varying periods of time. Immobilization for 6 days resulted in a 41% reduction in proteoglycan synthesis by articular cartilage from the restrained knee compared with the contralateral control knee. After 3 weeks of immobilization, proteoglycan aggregation was no longer demonstrable in cartilage from the constrained limb. The aggregation defect was rapidly reversible and aggregates were again normal size 2 weeks after removal of a cast that had been worn for 6 weeks.

Patello-femoral joint mechanics and pathology. 2. Chondromalacia patellae

Two distinct lesions affect the articular cartilage of the patella. Surface degeneration occurs particularly on the odd facet; it is age dependent, often present in youth and it becomes more frequent with increasing age. It probably does not occasion patello-femoral pain in youth, but may predispose to degenerative arthritis in that joint in later years and is regarded as a consequence of habitual disuse. The term "basal degeneration" is used to describe a lesion in which there is a fasciculation of collagen in the middle and deep zones of cartilage without, at first, affecting the surface. It was found astride the ridge separating the medial from the odd facet in twenty-three adolescents who had complained of prolonged patello-femoral pain. They were treated by excision of the disc of affected cartilage, with relief of pain in most cases. The pathogenesis of basal degeneration is related to the functional anatomy of the patella.

Pathologic evidence of degeneration as a primary cause of rotator cuff tear

Histopathologic, histochemical, and morphometric studies were done on 80 medial stumps of torn rotator cuff tendons to clarify the cause of tears. A high prevalence and diffuse distribution of degenerative changes were observed in the rotator cuff tendons including thinning and disorientation of collagen fibers, myxoid degeneration, hyaline degeneration, chondroid metaplasia, calcification, vascularproliferation, and fatty infiltration. No distinct inflammatory reaction was observed. Thinning and disorientation of collagen fibers, myxoid degeneration, and hyaline degeneration were seen in all cases. All changes except vascular proliferation and fatty infiltration were more pronounced in the middle to deep layers of the tendons than in the superficial layer. The collagen fibers were disoriented in the deep layer of the tendons, shown by microscopic image analysis. The frequency and distribution of thinning and disorientation of collagen fibers, myxoid degeneration, and hyaline degeneration suggest that these are early degenerative processes. Chondroid metaplasia and calcification may be chronic pathologic changes that occur after tearing regardless of the type of tear. Preexisting degenerative change in the middle and deep layers of the tendon in association with microtrauma seems to be the main cause of rotator cuff tears.

Light microscopy of Indian ink preparations of fibrillated cartilage

Images

Mesenchymal chondrosarcoma. A clinicopathologic analysis of 35 patients with emphasis on treatment

Almost a quarter of a century has passed since mesenchymal chondrosarcoma, a rare, insufficiently studied and still poorly understood cartilage neoplasm has been described. Based on 35 cases diagnosed and treated at this Cancer Center, this study found 20 males and 15 females with an average age of 26 years (range, 6-70 years). All but five of the tumors arose in the skeleton in the femur, humerus, and ilium in five cases each, while the os calcis (a rare site for any other osseous tumor) gave rise to this tumor in four instances. Pain was the cardinal symptom in 27 patients. The lesional size varied from 4 to 18 cm (average, 9.5 cm). Histologic examination revealed nine of the tumors to be of the small cell undifferentiated types while the others were of the "hemangiopericytomatoid" variant. According to this subclassification, patients with the small cell type of lesions responded to combination chemotherapy and irradiation, as usually do other small cell sarcomas. The addition of surgical resection may be of value especially in the patients with the hemangiopericytomatoid variant. Preliminary results in the treatment of five such patients with evaluable disease suggest that this combined treatment approach is encouraging. Follow-up analysis of all patients revealed a 37.9 months median survival, and 28% to be alive at ten years.

Subchondral bone and cartilage disease: a rediscovered functional unit

The role of subchondral bone in the pathogenesis of cartilage damage has likely been underestimated. Subchondral bone is not only an important shock absorber, but it may also be important for cartilage metabolism. Contrary to many drawings and published reports, the subchondral region is highly vascularized and vulnerable. Its terminal vessels have, in part, direct contact with the deepest hyaline cartilage layer. The perfusion of these vessels accounts for more than 50% of the glucose, oxygen, and water requirements of cartilage. Bony structure, local metabolism, hemodynamics, and vascularization of the subchondral region differ within a single joint and from one joint to another. Owing to these differences, repetitive, chronic overloading or perfusion abnormalities may result in no pathological reaction at all in one joint, while in another joint, these same conditions may lead to osteonecrosis, osteochondritis dissecans, or degenerative changes. According to this common etiological root, similar pathological reactions beginning with marrow edema and necrosis and followed by bone and cartilage fractures, joint deformity, and insufficient healing processes are found in osteonecrosis, osteochondritis dissecans, and degenerative disease as well.

Chitosan-glycerol phosphate/blood implants elicit hyaline cartilage repair integrated with porous subchondral bone in microdrilled rabbit defects

OBJECTIVE

We have previously shown that microfractured ovine defects are repaired with more hyaline cartilage when the defect is treated with in situ-solidified implants of chitosan-glycerol phosphate (chitosan-GP) mixed with autologous whole blood. The objectives of this study were (1) to characterize chitosan-GP/blood clots in vitro, and (2) to develop a rabbit marrow stimulation model in order to determine the effects of the chitosan-GP/blood implant and of debridement on the formation of incipient cartilage repair tissue.

METHODS

Blood clots were characterized by histology and in vitro clot retraction tests. Bilateral 3.5 x 4 mm trochlear defects debrided into the calcified layer were pierced with four microdrill holes and filled with a chitosan-GP/blood implant or allowed to bleed freely as a control. At 1 day post-surgery, initial defects were characterized by histomorphometry (n=3). After 8 weeks of repair, osteochondral repair tissues between or through the drill holes were evaluated by histology, histomorphometry, collagen type II expression, and stereology (n=16).

RESULTS

Chitosan-GP solutions structurally stabilized the blood clots by inhibiting clot retraction. Treatment of drilled defects with chitosan-GP/blood clots led to the formation of a more integrated and hyaline repair tissue above a more porous and vascularized subchondral bone plate compared to drilling alone. Correlation analysis of repair tissue between the drill holes revealed that the absence of calcified cartilage and the presence of a porous subchondral bone plate were predictors of greater repair tissue integration with subchondral bone (P<0.005), and of a higher total O'Driscoll score (P<0.005 and P<0.01, respectively).

CONCLUSIONS

Chitosan-GP/blood implants applied in conjunction with drilling, compared to drilling alone, elicited a more hyaline and integrated repair tissue associated with a porous subchondral bone replete with blood vessels. Concomitant regeneration of a vascularized bone plate during cartilage repair could provide progenitors, anabolic factors and nutrients that aid in the formation of hyaline cartilage.

The problem of chondromalacia patellae

Daily activity subjects the human patella to forces often several times the individual's body weight. Healthy cartilage can adjust to these forces if they are not too excessive, concentrated, or repetitive. Such abnormal stresses most frequently occur with the disturbance of normal patellar mechanical function. Chondromalacia patellae is the result common to a wide variety of unusual traumata. Treatment must be directed primarily not toward the damaged patellar cartilage but toward a correction of the mechanical abnormality causing it. Until proven otherwise, a young female complaining of knee joint pain, particularly if bilateral, should be considered as suffering from a subluxating patella, with or without chondromalacia patellae.

Wrist anatomy: incidence, distribution, and correlation of anatomic variations, tears, and arthrosis

We dissected 393 wrists to evaluate the incidence and distribution of anatomic features, arthrosis, chondromalacia, and soft tissue lesions. The data were then analyzed for any statistically significant associations among the different variables. The most common (73%) lunate morphology had a separate medial facet on its distal surface for the hamate. The capitate had a separate facet for the fourth metacarpal in 86% of the wrists. Fourth metacarpals with a dorsal radial facet, either separate from or connected to the rest of the fourth metacarpal base, were the most common types of fourth metacarpal. Cartilage erosion with exposed subchondral bone was identified in 58% of the wrists. It was most commonly at the proximal pole of the hamate (28%). Tears of the ligaments and/or the triangular fibrocartilage complex were identified in 56% of the wrists. The triangular fibrocartilage complex was found torn in 36% of the wrists. The lunotriquetral interosseous ligament was torn in 36% of the wrists, and the scapholunate interosseous ligament was torn in 28% of the wrists. There was a communication between the proximal wrist joint and the pisotriquetral joint in 88% of the 76 wrists, which were further dissected to assess this issue. Statistical analysis of the data found a significant correlation between the presence of cartilage erosion at the proximal pole of the hamate and the presence of a lunate facet. There was also a significant correlation between the presence of a tear in the scapholunate interosseous ligament and the presence of cartilage erosion in the scaphoid-trapezium-trapezoid joint. Analysis of the paired wrists from 169 cadavers revealed that the same soft tissue tear or combination of tears was present bilaterally in 39% of the pairs. Cartilage erosion was present bilaterally in the same location or locations in 27% of the pairs.