摘要:

The current state of knowledge on the structure and function of the macromolecules of articular cartilage is summarized. This highly hydrated tissue is composed of relatively few cells embedded in an extracellular matrix. The matrix consists of a fibrillar meshwork composed of mainly cross-linked type II collagen molecules, but with small amounts of type XI and IX collagen. The interstices of this meshwork are filled with the proteoglycan aggrecan bound, with link proteins, to chains of hyaluronan to form proteoglycan aggregates. The tissue also contains the small proteoglycans decorin, biglycan, and fibromodulin. The adhesion protein type VI collagen surrounds the chondrocytes and, in the extracellular matrix, binds to hyaluronan and other matrix molecules, probably to organize the matrix into higher ordered structures. The organization of these macromolecular structures with the water of the tissues endows articular cartilage with its characteristic mechanical properties.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Molecules derived from cartilage are present in body fluids where they act as markers of the degradation or synthesis of specific components of the extracellular matrix of this shock-absorbing tissue. In joint fluid, the level of a marker molecule can be used to detect changes taking place in the cartilaginous tissues within that joint. In blood or urine, on the other hand, the level can be used to identify systemic changes or abnormalities affecting most or all the cartilages in the body. These specific markers of metabolic processes already have proved useful in identifying increased catabolic as well as anabolic activities in articular cartilage following traumatic knee joint injury. The markers are potentially useful for monitoring disease activity, identifying osteoarthritis in its preradiological stages, examining responses of the cartilaginous tissues to treatment and evaluating long-term prognosis. Markers should prove most useful in prospective studies aimed at identifying early changes in cartilage metabolism in humans who are at high risk of developing posttraumatic osteoarthritis.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Exercise places widely varying biomechanical and physiologic demands upon articular cartilage. Intermittent compression tends to stimulate chondrocyte biosynthesis, which is the basis for articular cartilage adaptation. Joint motion without compression causes articular cartilage thinning, and static loading causes decreased chondrocyte biosynthesis. In vivo canine studies have demonstrated, however, that although moderate levels of running stimulate adaptation, strenuous levels can cause detrimental articular cartilage changes. Prospective studies evaluating the effect of exercise upon articular cartilage in humans have documented increased asymptomatic knee osteophytes in runners. There seem to be activity thresholds below and above which the effects are minimal or destructive, respectively. Between these thresholds, articular cartilage seems to adapt mechanically to the loads placed upon it by exercise. The adaptive ability of articular cartilage may be compromised in the injured or aged joint.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Many imaging modalities are currently used to evaluate articular cartilage. Despite the fact that conventional radiography allows only indirect assessment of cartilage, it remains the primary modality for cartilage evaluation in acute and chronic articular disorders. Compared with newer modalities, arthrography has a very limited role in cartilage evaluation. Computed tomography performed after intraarticular injection of contrast material (CT arthro-tomography) is an excellent method for evaluating complex articular anatomy and pathology. More recently, due to its superior soft tissue contrast and multiplanar capability, MRI has made a significant impact in the imaging of the musculoskeletal system. The role of MRI in the assessment of articular cartilage is developing, but it is clear that MRI at present is the best noninvasive method for evaluating articular cartilage. With further technologic improvement, the role of MR in evaluating chondral abnormalities should become larger and better defined.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Articular cartilage is a versatile structure that provides a near fric-tionless surface while resisting compression and shear forces and distributing stress. Damage to the joint surface of the knee may result in both short- and long-term disability. Arthroscopy and magnetic resonance imaging allow better identification of injuries to the hyaline cartilage and subchondral bone. Chondral and osteochondral fractures, loss of the menisci, and recurrent instability appear to contribute to the deterioration of the knee joint surfaces. Prevention of this deterioration is critical since there are no reliable methods available at the present time to restore the articular cartilage of the knee. Correction of the mechanical axis and elimination of pathologic laxity are fundamental issues that must be recognized and addressed. Treatment of chronic chondral injuries with arthroscopic debridement and abrasion arthroplasty provide somewhat unpredictable and incomplete, symptomatic relief in selected patients. Auto-geneic and allogeneic tissue as well as synthetic materials have been used to repair the articular surface with the hope of decreasing friction and preventing progressive erosion. Osteochondral allograft transplantation has achieved limited early success with the associated inherent risk of disease transmission. Periosteal resurfacing and carbon fiber implantation are promising experimental techniques that require further research and development. Prosthetic arthroplasty is a reproducible, end-stage reconstructive procedure that cannot be applied to a young, athletic population.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The fresh osteochondral allograft is an established procedure for reconstructing joint surface defects, especially in the knee. The best results are obtained in young patients who have posttraumatic joint surface defects before the onset of secondary degenerative changes. Fresh tissue is preferred because of its potentially greater chondrocyte viability as compared to frozen, irradiated, or cryopreserved tissue. Donor selection is based on the same criteria as multiple organ donation. The ideal donor is younger than 30 years of age, and the donor joint must not be damaged. Transplantation should be performed within 24 h of graft procurement. Menisci may be included in the allograft. Malalignment should be corrected by osteotomy so that the resultant biome-chanical axis passes through the nonallografted compartment. Immunological factors are less important than biomechanics in determining the outcome. Success rates as high as 79% may be achieved in properly selected patients. This article reviews patient selection, graft procurement, surgical technique, postoperative care, immunological factors, and results in fresh osteochondral allografting.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Since the first description of osteochondritis dissecans, there has been an unfortunate tendency in the scientific literature to include all age groups, whether the epiphysis is closed or open, in the same article. Juvenile osteochondritis dissecans (JOCD) is distinct from osteochondritis dissecans (OCD), which occurs after the femoral epiphysis is closed. JOCD is not a osteochondral fracture, an accessory center of ossification, hereditary dysplasia, or osteonecrosis. JOCD has a vastly more favorable prognosis than does OCD and, by definition, presents prior to the closing of the adjacent epiphysis. The etiology of JOCD is a stress failure syndrome of subchondral bone, related to a cumulative exercise dose administered over months or years to the immature knee. The goal of treatment of JOCD is to obtain healing of the lesion prior to closing of the epiphysis, when the prognosis becomes poor. In most cases, this healing can be obtained by activity restriction alone. When this is not successful, aggressive steps must be taken to promote lesion healing. Preservation of joint surface congruity and orthopticity must be perfect to avoid the inexorable arthrosis if treatment fails.

ISSN:1062-8592    

出版商:OVID    

年代:1994

数据来源: OVID