TO THE EDITOR:
The "Current Concepts Review. Osteochondritis Dissecans" (78-A: 439—456, March 1996), by Schenck and Goodnight, is an excellent review of osteochondritis dissecans. However, there are three points on which I would like to comment.
The first item, and the simplest to rectify, is a typographical error on page 442 at the end of the first paragraph. The authors stated: "They also thought that a symptomatic patient with a stage-I or II lesion should be allowed to return to sports activities." The word "symptomatic" should read "asymptomatic."
Second, I would like to address the statement on page 443, in the last sentence of the Trauma section: "The role of indirect microtrauma as an etiological factor remains theoretical." I am concerned by this statement for several reasons. There is increasing circumstantial evidence that the nature of juvenile osteochondritis dissecans changes as the amount of exercise that the child receives accumulates. Furthermore, it seems that an earlier entry into organized sports also contributes to an increase in the cumulative amount of the exercise dose. Together, these two factors produce a morphological form of juvenile osteochondritis dissecans in a weight-bearing zone of the femoral condyle, not in the classic position on the lateral side of the medial femoral condyle, as described by Aichroth1. While the lesions of juvenile osteochondritis dissecans described by Aichroth may not be subchondral fractures, the previous three findings are at least circumstantial evidence that the etiology of the lesions of juvenile osteochondritis dissecans in a weight-bearing zone is subchondral fractures.
My third concern is regarding the implication, in the summary on page 452, that both non-operative and arthroscopic treatment is benign. According to that summary: "Children who have a lesion of the knee usually do well irrespective of the method of treatment, and those who have a persistently symptomatic lesion generally respond well to operative arthroscopy if limitation of activity and protected weight-bearing have failed." In 1989, my colleagues and I reported on ninety-two symptomatic knees in seventy-six patients who had juvenile osteochondritis dissecans5. These patients were managed with a non-operative program and had a 50 per cent rate of failure. Of the patients who had a failure, 34 per cent had a detachment of the lesion while under management. This finding hardly represents a benign outcome of this condition. In addition, I know of no long-term studies that support the statement that children "who have a persistently symptomatic lesion generally respond well to operative arthroscopy."
Bernard R. Cahill, M.D.: 303 North William Kumpf Boulevard, Peoria, Illinois 61605
Dr. Schenck and Dr. Goodnight reply:
With respect to indirect microtrauma, we were making direct reference to previous theories held by other investigators1,7,10, who postulated that internal repetitive impingement on the tibial spine, ligamentous laxity, or pressure from the odd facet results in the lesions of osteochondritis dissecans. We were not dismissing the concept that osteochondrotic changes could occur as a stress fracture. Although Carroll and Mubarak6 reported that trauma is an unlikely cause of osteochondritis dissecans, as the affected sites are at specific locations, many authors have agreed that trauma or direct microtrauma may result in the lesions of osteochondritis dissecans3,8,9,11. However, when we discussed indirect trauma, we were referring to the three specific theories1,7,10 that we mentioned and not to Dr. Cahill's theory of stress fractures from overuse2-4.
With respect to Dr. Cahill's comment concerning our final statement, we meant to reiterate that lesions of osteochondritis dissecans in patients who have open growth plates have a more favorable healing response than those in patients who have closed growth plates. As Dr. Cahill noted in his review of osteochondritis dissecans of the knee, physeal closure can be an ominous sign in the treatment of juvenile osteochondritis dissecans3. Osteochondritis dissecans in patients who have open growth plates has a more favorable outcome or chance of healing than that in adult patients. We agree with Dr. Cahill that patients with lesions that necessitate simple excision will, unfortunately, have a poor result.
Robert C. Schenck, Jr., M.D.; Jon Marc Goodnight, M.D.: Department of Orthopaedics, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78284-7774