Articular Cartilage Defects

 Properties of Articular Cartilage

·                 lacks blood supply and does not have innervation or lymphatic drainage

·                 varies in thickness from 2 mm to 4 mm and is thickest at periphery of concave surfaces and central portions of convex surfaces

·                 composed of type 2 collagen, water, proteoglycans, and chondrocytes

·                 collagen provides resistance against tensile stresses and transmits vertical loads

·                 water and proteoglycans provide turgor and elasticity and help to limit friction

·                 chondrocytes synthesize the cartilage matrix and control matrix turnover rate

 

Etiology

·                 overt trauma or repeated minor trauma; most commonly from sports injuries

·                 early stage osteoarthritis

·                 genetic degenerative diseases such as osteochondritis dissecans

 

Clinical Features

·                 very similar to symptoms of osteoarthritis (joint line pain with possible effusion, etc.)

·                 often have predisposing factors such as ligament injury, malalignment of the joint (varus/ valgus), obesity, bone deficiency (avascular necrosis, osteochondritis dissecans, ganglion bone cysts), inflammatory arthropathy, and familial osteoarthropathy

·                 may have symptoms of locking or catching related to the torn/displaced cartilage

 

Investigations

·                 arthroscopy to visualize focal pathology and guide treatment strategy

·                 MRI may also be used to visualize the defect

 

Table 21. Outerbridge Classification of Chondral Detects

 

Treatment

·                 arthroscopic lavage and debridement of the joint

·                 marrow stimulation techniques (microfracture, drilling, abrasion arthroplasty)

o       involves creating a site of bleeding where new growth/healing can take place

·                 osteochondral grafts; also known as the OATS procedure or mosaicplasty

o       involves transferring osteochondral fragments from non-weightbearing surface to area of defect

·                 autologous chondrocyte: implantation (ACI)

o       currently only available in the U.S. and Europe

o       involves harvesting patient's cartilage, growing it in culture: medium outside of the patient, then reinserting the newly cultured chondrocytes back to fill the chondral defect

o       osteochondral allograft; only used in limited circumstances when defect is very large