JBJS | Early Detection of Osteochondritis Dissecans of the Capitellum in Young Baseball Players. Report of Three Cases*

The Journal of Bone & Joint Surgery, Volume 80, Issue 6

Articles | June 01, 1998

Early Detection of Osteochondritis Dissecans of the Capitellum in Young Baseball Players. Report of Three Cases*

MASATOSHI TAKAHARA, M.D.†; MOTOYUKI SHUNDO, M.D.‡; MAKOTO KONDO, M.D.‡; KATSUNORI SUZUKI, M.D.‡; TOSHIKAZU NAMBU, M.D.‡; TOSHIHIKO OGINO, M.D.†, SAPPORO, JAPAN

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Investigation performed at the Department of Orthopaedic Surgery, Hokkaido University School of Medicine, Sapporo City

The Journal of Bone & Joint Surgery. 1998; 80:892-7

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Introduction

Introduction | Case Reports | Discussion | References

The prevalence of osteochondritis dissecans is high among individuals who have played baseball actively since childhood^1,19, and repetitive throwing is considered to be one of the main etiological factors of this disease^1,4,5,10,25. During the acceleration phase of throwing, the elbow joint may be stressed into a valgus position^17,38,47,49 and the capitellum may be subjected to compression and shear forces^{4,20,21,44,48,50}. However, little is known about the primary changes leading to osteochondritis dissecans. We attempted to detect these changes by examining the elbows of players on youth baseball teams with magnetic resonance imaging and ultrasonography. Forty-four young baseball players who were ten to twelve years old and had not had a previous examination of the elbow were selected for this study.

Magnetic resonance imaging was performed with a 1.5-tesla magnet (Magnetom H15; Siemens Medical Systems, Erlangen, Germany), and coronal and sagittal T1-weighted spin-echo images and sagittal T2-weighted gradient-echo images were made. Anterior and posterior longitudinal ultrasonograms of the capitellum were made with a real-time linear-array scanner (Aloka SSDF-650, Tokyo, Japan) that was equipped with a 7.5-megahertz transducer^27,45 (Figs. 1-A and 1-B).

Three of the forty-four boys were found to have an abnormality of the capitellum. The T1-weighted images of these boys showed low signal intensity in the superficial aspect of the capitellum (Figs. 2-A and 2-B), whereas the T2-weighted images showed no abnormalities and ultrasonography showed localized flattening of the subchondral bone and a normal outline of the articular cartilage (Fig. 1-C). The three boys were advised to stop pitching. Two of the boys stopped pitching and the elbow healed spontaneously, but the other boy continued to pitch and typical osteochondritis dissecans developed. These findings suggest that the abnormalities demonstrated by magnetic resonance imaging and ultrasonography are the early changes leading to osteochondritis dissecans.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

†Department of Orthopaedic Surgery, Yamagata University School of Medicine, Iida-Nishi 2, Yamagata 990-9585, Japan. Please address requests for reprints to Dr. Takahara. E-mail address for Dr. Takahara: mtakahar@med.id.yamagata-u.ac.jp.

‡Departments of Orthopaedic Surgery (M. S., M. K., and K. S.) and Radiology (T. N.), Hokkaido University School of Medicine, Kitaku, Kita-14, Nishi-7, Sapporo 060, Japan.

*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

‡Departments of Orthopaedic Surgery (M. S., M. K., and K. S.) and Radiology (T. N.), Hokkaido University School of Medicine, Kitaku, Kita-14, Nishi-7, Sapporo 060, Japan.

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Figs. 1-A through 1-D: Illustration and ultrasonograms of the capitellum. Fig. 1-A: Line drawing showing the relationship of the humerus and the radial head to the ultrasonographic scanner.

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Fig. 1-B: Anterior longitudinal ultrasonogram of a normal capitellum, showing the subchondral bone of the capitellum as a high-signal-intensity round area (white arrows) and the articular cartilage as a low-signal-intensity round area (black arrows) over the subchondral bone.

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Fig. 1-C: Case 1. Anterior longitudinal ultrasonogram, made at the first examination, showing localized flattening of the subchondral bone (white arrows) and an articular surface with a normal outline (black arrows).

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Fig. 1-D: Case 1. Anterior longitudinal ultrasonogram, made eleven months after the first examination, showing a bone fragment (arrow) that is not displaced from the surrounding bone of the capitellum.

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Case 2. Coronal (Fig. 2-A) and sagittal (Fig. 2-B) T1-weighted magnetic resonance images, made at the first examination, showing a low signal intensity in the superficial aspect of the capitellum.

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Case 2. Coronal (Fig. 2-A) and sagittal (Fig. 2-B) T1-weighted magnetic resonance images, made at the first examination, showing a low signal intensity in the superficial aspect of the capitellum.

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Figs. 3-A through 3-E: Case 1. Fig. 3-A: Anteroposterior radiograph, made at the first examination, with the elbow in extension. The capitellum appears normal.

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Fig. 3-B: Anteroposterior radiograph, made at the first examination, with the elbow in 45 degrees of flexion. There is slight flattening and sclerosis of the lateral surface of the capitellum (arrowhead).

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Fig. 3-C: Anteroposterior radiograph, made four months after the first examination, with the elbow in 45 degrees of flexion. Radiolucent bone (arrowheads) is seen over the flattened sclerotic bone of the superficial aspect of the capitellum.

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Fig. 3-D: Anteroposterior radiograph, made eleven months after the first examination, with the elbow in 45 degrees of flexion. A radiolucent bone fragment (arrow) is seen on the central surface of the capitellum.

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Fig. 3-E: Anteroposterior radiograph, made three years and six months after the first examination, with the elbow in 45 degrees of flexion. The capitellum appears almost normal.

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Figs. 4-A through 4-D: Case 3. Fig. 4-A: Anteroposterior radiograph, made four months after the first examination, with the elbow in extension. The capitellum appears normal.

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Fig. 4-B: Anteroposterior radiograph, made four months after the first examination, with the elbow in 45 degrees of flexion. A small fragment (arrowhead) over the flattened sclerotic bone of the capitellum and fragmentation of the distal part of the medial epicondyle are seen.

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Fig. 4-C: Anteroposterior radiograph, made two years and six months after the first examination, with the elbow in 45 degrees of flexion. Discrete fragments (arrowheads) are seen over the radiolucent zone of the capitellum.

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Fig. 4-D: Lateral radiograph, made four years after the first examination, showing loose bodies (arrow) detached from the capitellum.

Case Reports

Introduction | Case Reports | Discussion | References

CASE 1. A twelve-year-old boy, who had been a member of a baseball team for four years and who pitched with the right hand, had had slight pain in the right elbow joint while pitching for one month before the examination. During the examination, tenderness of the right capitellum was noted. The right elbow could be actively extended to 0 degrees and actively flexed to 150 degrees without pain. Magnetic resonance imaging and ultrasonography showed abnormalities of the capitellum as just described. Anteroposterior radiographs of the elbow were then made immediately. The anteroposterior radiograph made with the elbow extended (an ordinary anteroposterior radiograph of the elbow) showed a normal capitellum before epiphyseal closure (Fig. 3-A). The anteroposterior radiograph made with the elbow in 45 degrees of flexion showed slight flattening and sclerosis of the lateral surface of the capitellum (Fig. 3-B). No abnormalities were evident on any of the images of the left elbow.

The boy followed our advice to stop pitching, and he had no pain in the elbow one month later. Follow-up radiographs were made repeatedly. Four months after the first examination, an anteroposterior radiograph made with the elbow in 45 degrees of flexion showed radiolucent bone over the flattened sclerotic bone (Fig. 3-C). Eleven months after the first examination, an anteroposterior radiograph made with the elbow in 45 degrees of flexion showed a radiolucent bone fragment on the central surface of the capitellum (Fig. 3-D). Anterior longitudinal ultrasonograms of the capitellum made eleven months after the first examination showed a bone fragment that was not displaced from the surrounding bone of the capitellum (Fig. 1-D). Three years and six months after the first examination, an anteroposterior radiograph made with the elbow in 45 degrees of flexion showed an almost normal capitellum (Fig. 3-E).

CASE 2. An eleven-year-old boy, who had played on a baseball team for three years and was a right-handed pitcher, had had slight pain in the right elbow while pitching for five months before the examination. The examination revealed tenderness of the right capitellum and medial epicondyle. The right elbow joint could be actively extended to 7 degrees (hyperextension) and actively flexed to 145 degrees. Magnetic resonance imaging and ultrasonography showed abnormalities, as described. The radiographic findings were the same as those in Case 1. No abnormalities were noted on any of the images of the left elbow.

The patient stopped pitching, as advised. One month later, he had no pain in the elbow. Follow-up anteroposterior radiographs made with the elbow in 45 degrees of flexion demonstrated a radiolucent bone fragment over the flattened sclerotic bone, and ultrasonograms of the capitellum demonstrated a new bone fragment that was not displaced from the underlying bone. The most recent radiograph, made three years and four months after the first examination, showed a normal capitellum.

CASE 3. An eleven-year-old boy, a right-handed pitcher who had been a member of a baseball team for three years, had begun to have slight pain while pitching five months before the examination. The right capitellum and medial epicondyle were noted to be tender during the first examination. The elbow joint could be actively extended to 7 degrees (hyperextension) and actively flexed to 145 degrees. Magnetic resonance imaging and ultrasonography showed the abnormalities described previously.

The patient was advised to stop throwing, but he continued to pitch. Anteroposterior radiographs (Figs. 4-A and 4-B), which were not made until four months after the examination because of the patient's personal circumstances, showed a small fragment over the sclerotic bone of the capitellum and fragmentation of the distal part of the medial epicondyle with the elbow in 45 degrees of flexion (Fig. 4-B). There were no abnormalities on the images of the left elbow. The boy still did not heed our advice to stop pitching and dropped out of the study. However, two years and six months later, he returned to the clinic with severe pain in the elbow. An anteroposterior radiograph made with the elbow in 45 degrees of flexion showed discrete fragments over the radiolucent zone of the capitellum (Fig. 4-C). Typical osteochondritis dissecans of the capitellum was diagnosed, but the boy continued to play baseball as a fielder. Four years after the first examination, a lateral radiograph showed loose bodies that were completely detached from the capitellum (Fig. 4-D); this finding was confirmed with magnetic resonance imaging.

Discussion

Introduction | Case Reports | Discussion | References

A variety of conditions, such as osteochondral fractures^24,28, ossification defects⁶, avascular necrosis¹¹, accessory centers of ossification^23,40, and detachment of fragments, have been reported to be associated with osteochondritis dissecans. Numerous authors have discussed the etiology of the disease^{12,15,39,41,42}. The causes include trauma, ischemia, constitution, and genetic predisposition. Various theories have been proposed in order to explain the pathogenesis of osteochondritis dissecans^{2,3,7-9,14,16,18,22,26,29,30,32,34-37,43,46}; however, little is known about the early changes. In order to clarify the pathogenesis, it is necessary to study the early changes and then to follow them over time. To detect the early changes that may lead to osteochondritis dissecans of the capitellum, we performed magnetic resonance imaging and ultrasonography of the elbows of forty-four male baseball players who were ten to twelve years old; we identified capitellar abnormalities in three of them. One of the three boys did not stop pitching, and typical osteochondritis dissecans developed. Therefore, the results suggest that the abnormalities demonstrated on magnetic resonance imaging and ultrasonography are indeed the early changes leading to osteochondritis dissecans. These images of the early changes are of considerable value for studying the pathogenesis of this disease.

The early changes were a low signal intensity in the superficial aspect of the capitellum on T1-weighted images and no abnormalities on the T2-weighted images. Ultrasonography showed localized flattening of the subchondral bone and a normal outline of the articular cartilage. Anteroposterior radiographs made with the elbow in 45 degrees of flexion showed slight flattening and sclerosis of the superficial aspect of the capitellum. The low signal intensity on the T1-weighted images indicated that there were some pathological conditions in the superficial aspect of the capitellum, such as fracture, sclerosis, inflammation, necrosis, and post-traumatic changes. In most cases of osteochondritis dissecans, T2-weighted images show a high-signal-intensity interface^13,31,33 beneath the fragment, which indicates invasion by the joint fluid beneath the fragment. However, the T2-weighted images of the three boys in our study demonstrated no evidence of fragmentation. This suggests that there is no gap in early osteochondritis dissecans. Localized flattening of the subchondral bone was demonstrated on ultrasonograms and radiographs, while the outline of the articular cartilage appeared normal on the magnetic resonance images and ultrasonograms. These findings lead us to speculate that the early changes associated with osteochondritis dissecans of the capitellum could be impaction fracture or delayed ossification in the surface of the immature epiphyseal nucleus. Additional studies are needed to identify the early pathological changes leading to osteochondritis dissecans.

Follow-up radiographs of the two boys who stopped pitching showed a radiolucent bone fragment over the flattened sclerotic bone of the capitellum, and a similar bone fragment was observed on the ultrasonograms. These findings suggest that new-bone formation may cover the flattened bone and that early osteochondritis dissecans has the potential to heal spontaneously. Typical osteochondritis dissecans of the capitellum developed in the boy who continued to pitch. On the basis of these results, we hypothesized that the new radiolucent bone can be easily broken and detached and that disruption of the fragment could be a critical factor in the development of osteochondritis dissecans of the capitellum.

We speculated that young baseball players on top-level teams could be at higher risk for osteochondritis dissecans because they typically play several games every weekend and there is continuous strenuous training every day to maintain the standard of athletic achievement. Information about the risk of osteochondritis dissecans, and the need to perform regular examinations of the elbows, was given to the managers of the top thirty-two youth baseball teams in Sapporo City in 1991. The managers were asked to invite volunteers who were ten to twelve years old to participate in a study in which the elbow was evaluated with magnetic resonance imaging and ultrasonography. Forty-five volunteers agreed to participate; the failure of the other players to participate was probably due to poor distribution of the information, personal circumstances, or individual decision. One of the participants was excluded from this study because the elbow had been examined before the study began. T2-weighted images of this elbow showed a high-signal-intensity interface beneath the fragment in the capitellum, and a diagnosis of typical osteochondritis dissecans was made. The remaining forty-four participants had not sought previous medical advice regarding the elbow. Twenty-five of the participants were pitchers, ten were catchers, and nine were fielders. Three of the forty-four subjects (three of the twenty-five pitchers) were found to have early osteochondritis dissecans of the capitellum. The reason for this surprisingly high rate of early osteochondritis dissecans was probably the criteria used for selection of the subjects. Additional studies will be necessary to address the prevalence in young baseball players and to identify the group that is at highest risk. We speculated that young boys who have early subclinical osteochondritis dissecans of the capitellum continue to play baseball because their discomfort is not severe enough to warrant medical attention. It is important to detect and treat osteochondritis dissecans early, before the lesion becomes unstable or the bone fragment becomes detached (as is usually seen in patients who have osteochondritis dissecans of the capitellum).

NOTE: The authors thank Kiyoshi Kaneda, M.D., Professor and Chairman, Akio Minami, M.D., Professor, and Hiroyuki Kato, M.D., Department of Orthopaedic Surgery, Hokkaido University School of Medicine, for their assistance in this study.

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