Abstract
The surgical treatment of knee articular focal lesions may offer heterogeneous clinical results. Osteochondritis dissecans (OCD) lesions showed to heal better than degenerative lesions (DL) but the underlying biological reasons are unknown. We evaluated the basal histological and immunohistochemical characteristics of these lesions analyzing a series of osteochondral fragments from young patients with similar age but presenting different etiology. Osteochondral tissue samples were stained with Safranin O and graded using a histological score. Markers of mesenchymal progenitor cells (CD146), osteoclasts (tartrate-resistant acid phosphatase, TRAP), and vessels (CD34) were evaluated. Histological score showed a higher degeneration of both cartilage and bone compartments in OCD compared to DL fragments. Only CD146-positive cells were found at the same percentage in cartilage compartment of both DL and OCD patients. By contrast, in the bone compartment a significantly higher percentage of CD146, TRAP, and CD34 markers was found in OCD compared to DL patients. These data showed distinct histological characteristics of osteochondral focal lesions located in the same anatomical region but having a different etiology. The higher percentages of these markers in OCD than in DL, mainly associated with a high bone turnover, could help to explain the higher clinical healing potential of OCD patients.
Highlights
Focal defects of the knee articular defect surface are diagnosed in 5–10% of patients undergoing knee arthroscopy [1]
When osteochondral lesions were analyzed on Safranin O stained sections (Figure 1(a)), the histological score revealed higher degenerated areas in Osteochondritis dissecans (OCD) compared to degenerative lesions (DL) (p < 0.0001; Figure 1(b), total score)
The main finding of this study is that the osteochondral tissue from focal lesions, located in the same anatomical region and in patients with similar age and BMI, presented distinct histological and biologic characteristics according to the etiology, which could explain the different healing potential and the different clinical results reported in the literature treating OCD and DL with osteochondral scaffolds
Summary
Focal defects of the knee articular defect surface are diagnosed in 5–10% of patients undergoing knee arthroscopy [1] Irrespective of their etiology, these lesions contribute to disability, impairing the quality of life mainly by limiting patients’ social activities, and premature development of osteoarthritis (OA) [2, 3]. Treatment options directed to the recruitment of bone marrow cells to obtain potential cartilage precursors have been developed to allow stem cells migration from the marrow cavity to the fibrin clot of the defect [4] These treatment options such as abrasion, drilling, and microfracture produce predominantly a fibrous repair tissue which lacks the biomechanical and viscoelastic characteristics of normal hyaline cartilage [2, 6]. The subchondral bone is involved in the etiopathological process
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