Pigmented villonodular disease of joints is a rare entity, mostly occurring in the knee and foot. The principal treatment is surgical excision which is most often successful in these sites but leads to problems at other locations, especially the hip.

The objective of this study was to evaluate the biomechanical properties of newly formed cartilaginous tissue synthesized from isolated chondrocytes. Cartilage from articular joints of lambs was either digested in collagenase to isolated chondrocytes or cut into discs that were devitalized by multiple freeze-thaw cycles. Isolated cells were incubated in suspension culture in the presence of devitalized cartilage matrix for 3 weeks. Multiple chondrocyte/matrix constructs were assembled with fibrin glue and implanted subcutaneously in nude mice for up to 6 weeks. Testing methods were devised to quantify integration of cartilage pieces and mechanical properties of constructs. These studies showed monotonic increase with time in tensile strength, fracture strain, fracture energy, and tensile modulus to values 5-10% of normal articular cartilage by 6 weeks in vivo. Histological analysis indicated that chondrocytes grown on dead cartilage matrix produced new matrix that integrated individual cartilage pieces with mechanically functional tissue.

Three-dimensional mapping of cartilage thickness shows great promise for the accurate measurement of focal cartilage defects, though improvement is needed. The Noyes grading scale is consistent with histological Mankin grading of cartilage lesions, though enhancement of MR grading scales is needed, and warranted, based on the signal intensity information available from clinical MRI. Integration of these two analyses-focal defect measurement and signal intensity analysis-could potentially result in a valuable clinical tool for early osteoarthritis diagnosis and longitudinal tracking.

Non-ossifying fibroma of bone (NOF) is a common entity, more frequently found in male children and consisting of a solitary eccentric, lytic expanded lesion in the metaphysis of a long bone. The disorder is benign and most often asymptomatic but may result in a fracture requiring therapy. Of some importance is to distinguish NOF from another very similar but smaller lesion, fibrous cortical defect, which is almost always asymptomatic and eccentrically located. Even more striking is a very rarely encountered lesion known as Jaffe-Campanacci syndrome, which also occurs in children who present with typical non-ossifying fibromatous tumors but in multiple sites. In addition, these patients have some systemic and dermal findings resembling those seen in patients with Type 1 neurofibromatosis.