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Harvard Medical School Beth Israel Deaconess Medical Center Boston, MA 02215
I would like to make a few comments regarding the recent article by Bui-Mansfield et al. entitled "Osteochondritis dissecans of the tibial plafond" [1].
The word "osteochondritis," implying a primary inflammatory process of bone and cartilage, is misleading. If the etiology were unknown, the term osteochondrosis, with its nonspecific suffix, might be more appropriate. This terminology would preserve the OCD acronym. However, as pointed out by Bui-Mansfield et al. [1], the cause of this entity is almost always injury. Even the word "dissecans," from the word "dissect," is inappropriate except when the subchondral fragment is loose or separates.
More satisfactory terms might be subchondral fracture, osteochondral fracture (OCF), or bruise. I believe that when symptoms of pain appear gradually the etiology is usually a stress reaction and, eventually, a stress fracture. The injury theory is in keeping with the increased incidence of OCF in the more injury-prone weight-bearing joints of men.
It also explains the appearance of OCF in relationship to specific stresses such as the capitellum in adolescent baseball pitchers and tennis players and the humeral head in large four-legged animals, particularly in artificially fattened pigs or calves [2]. Osteonecrosis (avascular necrosis) may some have similar imaging appearances, and perhaps some of these lesions are a combination of injury and osteonecrosis [2]. It is now known that some instances of focal bone marrow edema, once thought to represent spontaneous osteonecrosis in the knee or the hip, can represent insufficiency stress fractures [3].
OCF has a predilection for occurring in growing bones, and most cases occur on the convex surface of joints—talar dome, femoral condyle, femoral head (Legg-Calvé-Perthes), distal metatarsal (Freiberg), carpal lunate (Kienböck), tarsal navicular (Köhler), capitellum (Panner), and humeral head. The unusual occurrence of OCF on the concave surfaces of joints such as the tibial plafond [1] or the glenoid [4, 5] often warrants case reports.
Why is OCF more likely to affect convex joint surfaces? Perhaps it is because the biomechanical transmission of forces across joints is more concentrated on convex surfaces [1]. It is even possible that incidence of subchondral injury is similar on the convex and concave surfaces, but the greater cartilaginous surface on the circumferential convex surface results in a more tenuous blood supply and secondary foci of osteonecrosis [3].
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