Osteochondritis dissecans of the humeral capitellum in identical twin baseball players

Osteochondritis dissecans (OCD) is a focal idiopathic alteration of subchondral bone; it has an inherent risk of instability and disruption of adjacent articular cartilage that may result in premature osteoarthritis.7Edmonds E.W. Shea K.G. Osteochondritis dissecans: editorial comment.Clin Orthop Relat Res. 2013; 471: 1105-1106https://doi.org/10.1007/s11999-013-2837-6Crossref PubMed Scopus (54) Google Scholar Occurrence of OCD is common in the elbow and knee joints. OCD of the humeral capitellum generally affects adolescent athletes (eg, baseball players and gymnasts) who engage in repetitive overhead or upper extremity weight-bearing activities.3Bradley J.P. Petrie R.S. Osteochondritis dissecans of the humeral capitellum. Diagnosis and treatment.Clin Sports Med. 2001; 20: 565-590Abstract Full Text Full Text PDF PubMed Scopus (132) Google Scholar,5Cain Jr., E.L. Dugas J.R. Wolf R.S. Andrews J.R. Elbow injuries in throwing athletes: a current concepts review.Am J Sports Med. 2003; 31: 621-635https://doi.org/10.1177/03635465030310042601Crossref PubMed Scopus (295) Google Scholar The prevalence of capitellar OCD in baseball players ranging from 10 to 12 years of age has been reported to be 2.1/1,000.12Matsuura T. Suzue N. Iwame T. Nishio S. Sairyo K. Prevalence of osteochondritis dissecans of the capitellum in young baseball players: results based on ultrasonographic findings.Orthop J Sports Med. 2014; 2 (2325967114545298. https://doi.org/10.1177/2325967114545298)Crossref PubMed Scopus (36) Google Scholar The injury can progress to the separation of a segment of cartilage and subchondral bone, forming a loose body.1Barrie H.J. Osteochondritis dissecans 1887-1987. A centennial look at König's memorable phrase.J Bone Joint Surg Br. 1987; 69: 693-695Crossref PubMed Google Scholar Many etiological theories have been proposed for the onset and progression of OCD, including trauma, diet, rapid growth, anatomic characteristics, lack of blood supply, necrosis of subchondral bone, and heredity.2Bates J.T. Jacobs Jr., J.C. Shea K.G. Oxford J.T. Emerging genetic basis of osteochondritis dissecans.Clin Sports Med. 2014; 33: 199-220https://doi.org/10.1016/j.csm.2013.11.004Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar,6Edmonds E.W. Polousky J. A review of knowledge in osteochondritis dissecans: 123 years of minimal evolution from König to the ROCK study group.Clin Orthop Relat Res. 2013; 471: 1118-1126https://doi.org/10.1007/s11999-012-2290-yCrossref PubMed Scopus (137) Google Scholar,16Polousky J.D. Juvenile osteochondritis dissecans.Sports Med Arthrosc Rev. 2011; 19: 56-63https://doi.org/10.1097/JSA.0b013e31820b94b9Crossref PubMed Scopus (28) Google Scholar,20Ytrehus B. Carlson C.S. Ekman S. Etiology and pathogenesis of osteochondrosis.Vet Pathol. 2007; 44: 429-448https://doi.org/10.1354/vp.44-4-429Crossref PubMed Scopus (269) Google Scholar The exact etiology of OCD of the humeral capitellum is still unclear, but the primary cause is believed to be repetitive trauma to the poorly vascularized capitellum.9Haraldsson S. On osteochondrosis deformas juvenilis capituli humeri including investigation of intra-osseous vasculature in distal humerus.Acta Orthop Scand Suppl. 1959; 38: 1-232PubMed Google Scholar Genetic factors are also thought to play a role in the pathogenesis; however, the genetic basis of OCD remains unknown.2Bates J.T. Jacobs Jr., J.C. Shea K.G. Oxford J.T. Emerging genetic basis of osteochondritis dissecans.Clin Sports Med. 2014; 33: 199-220https://doi.org/10.1016/j.csm.2013.11.004Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar To our knowledge, the unique presentation of OCD affecting male identical twin baseball players, in the absence of syndromic features, has not been reported before. Here, we present 11-year-old identical twin baseball players with almost identical radiographic, computerized tomography, magnetic resonance imaging, ultrasound, and macroscopic findings and clinical course of OCD of the humeral capitellum. The patients were 11-year-old male identical twins who had been actively engaged in baseball for 4 years. The patients practiced baseball four times per week and were right-handed. The clinical history was unremarkable with no medical records or history of previous major trauma to the elbow. They were of similar physique, 147 cm tall, weighing 35 kg, and developmentally normal for their age. Twin A played mainly in the short-stop position. Twin B played mainly in the catcher position. Informed consent was received to report this case. The twins participated in a baseball elbow medical examination held at the beginning of the off-season and were diagnosed with OCD of the humeral capitellum by ultrasonography. Three months before the examination, both twins had experienced elbow pain on throwing during baseball but had no pain on throwing at the time of the examination. During the examination, the range of motion, valgus stress test, and tenderness of the medial epicondyle or humeral capitellum were assessed physically. Twin A had a slight limitation in the range of motion in elbow extension and flexion. Twin B did not indicate any abnormalities in the physical findings. Thereafter, ultrasonography of the medial epicondyle and humeral capitellum revealed similar OCD findings (Fig. 1) and medial epicondyle abnormalities in both twins, who were advised to visit an orthopedic hospital. One month later at the orthopedic hospital, X-ray examination revealed almost the same OCD findings (Fig. 2). The twins were instructed to cease throwing and to visit a doctor every other month. Two months later, the patients were gradually allowed to recommence throwing. After undergoing an X-ray examination 6 months after the first visit (Fig. 3), the patients stopped visiting the hospital. After the last hospital visit, the twins completed the entire baseball season (lasting for six months) without pain in their elbows. Twin A played mainly in the pitcher position, and twin B in the catcher position during the last season. However, when they returned to the orthopedic hospital after the season, they indicated that the OCD had worsened (Fig. 4). They hoped to continue playing baseball and decided to undergo surgery after discussion with their parents. They underwent surgery to transplant the auto osteochondral graft from the unloaded part of the knee joint into the OCD lesion. Twin A had a 9 × 10-mm osteochondral fragment removed, and φ4.5-mm and φ3.5-mm osteochondral grafts were transplanted. Twin B had a 9 × 13-mm osteochondral fragment removed, and two φ4.5-mm osteochondral grafts were transplanted (Fig. 5). A splint was fixed for 2 days after the surgery, and then the range of motion for training was initiated. Two and a half months after the surgery, throwing exercises were gradually started. Four months after the surgery, they were allowed to throw at maximal effort and returned to playing competitively. The twins were able to play baseball without any pain when throwing; there were no abnormal physical findings when they visited the hospital six months after the surgery (Fig. 6). We have documented our experience with 11-year-old identical twin baseball players with almost identical radiographic, computerized tomography, magnetic resonance imaging, ultrasound, and macroscopic findings and clinical course of OCD of the humeral capitellum. OCD of the humeral capitellum has been well described in the dominant arm of Little League baseball pitchers and is thought to be caused by repetitive increased loading of the radiocapitellar joint.4Brown R. Blazina M.E. Kerlan R.K. Carter V.S. Jobe F.W. Carlson G.J. Osteochondritis of the capitellum.J Sports Med. 1974; 2: 27-46Crossref PubMed Scopus (63) Google Scholar This experience with OCD cases of identical twin baseball players suggests that heredity is also an important factor for OCD. The exact etiology of OCD of the capitellum is presently unknown, but repetitive trauma to the poorly vascularized capitellum is believed to be the primary cause.9Haraldsson S. On osteochondrosis deformas juvenilis capituli humeri including investigation of intra-osseous vasculature in distal humerus.Acta Orthop Scand Suppl. 1959; 38: 1-232PubMed Google Scholar It is postulated that the mechanics during pitching places increased valgus stress and compression on the elbow, particularly during late cocking and early acceleration.5Cain Jr., E.L. Dugas J.R. Wolf R.S. Andrews J.R. Elbow injuries in throwing athletes: a current concepts review.Am J Sports Med. 2003; 31: 621-635https://doi.org/10.1177/03635465030310042601Crossref PubMed Scopus (295) Google Scholar Differences in biochemical properties of the radial head and capitellum are also believed to contribute to microtrauma, with the stiffer radial head articulating with the softer lateral capitellar surface causing increased strain.18Schenck Jr., R.C. Athanasiou K.A. Constantinides G. Gomez E. A biomechanical analysis of articular cartilage of the human elbow and a potential relationship to osteochondritis dissecans.Clin Orthop Relat Res. 1994; : 305-312Crossref PubMed Scopus (106) Google Scholar McManama et al reported repetitive trauma from throwing sports as the etiology in half of 14 patients who underwent surgical management for capitellar OCD lesions; however, it remains unclear as to why the other half had OCD lesions.14McManama Jr., G.B. Micheli L.J. Berry M.V. Sohn R.S. The surgical treatment of osteochondritis of the capitellum.Am J Sports Med. 1985; 13: 11-21Crossref PubMed Scopus (91) Google Scholar Therefore, it seems that repetitive microtrauma is not the only cause of OCD. Ischemia has also been implicated as a potential contributor to the progression of OCD because of its vascular anatomy. Haraldsson et al noted that the predominant blood supply was from end-arteries entering posteriorly and passing through compressible epiphyseal cartilage, with no connection to adjacent metaphyseal vessels.9Haraldsson S. On osteochondrosis deformas juvenilis capituli humeri including investigation of intra-osseous vasculature in distal humerus.Acta Orthop Scand Suppl. 1959; 38: 1-232PubMed Google Scholar This tenuous blood supply is at risk of repetitive elbow injury. It is generally accepted that repetitive microtrauma and ischemia are the leading causes of OCD lesions in the capitellum; however, there have been sporadic reports of a genetic link. To date, this predisposition for OCD in certain families has not been linked to any specific gene. Familial OCD is a disease in which articular cartilage on the surface of the knee, ankle, and elbow joints separates from the subchondral bone tissue. Stattin et al reported that this disease is caused by a missense mutation in the agrecan gene, which is a typical cartilage component.19Stattin E.L. Wiklund F. Lindblom K. Onnerfjord P. Jonsson B.A. Tegner Y. et al.A missense mutation in the aggrecan C-type lectin domain disrupts extracellular matrix interactions and causes dominant familial osteochondritis dissecans.Am J Hum Genet. 2010; 12: 126-137https://doi.org/10.1016/j.ajhg.2009.12.018Abstract Full Text Full Text PDF Scopus (108) Google Scholar The identical twin baseball player OCD cases suggest that heredity is one of the most important factors. Although genetic testing was not performed in this case, genetic factors are expected to be elucidated with the development of genetic testing in the future. Several cases of OCD of the humeral capitellum in twins have been reported previously. OCD of the nondominant elbow in fraternal twins was reported by Kenniston et al.10Kenniston J.A. Beredjiklian P.K. Bozentka D.J. Osteochondritis dissecans of the capitellum in fraternal twins: case report.J Hand Surg Am. 2008; 33: 1380-1383https://doi.org/10.1016/j.jhsa.2008.05.008Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar Matsuura et al reported cases of fraternal twins who had been actively engaged in competitive rhythmic gymnastics with similar bilateral OCD of the capitellum.13Matsuura T. Wada K. Suzue N. Iwame T. Fukuta S. Sairyo K. Bilateral osteochondritis dissecans of the capitellum in fraternal twins: a case report.JBJS Case Connect. 2017; 7: e44https://doi.org/10.2152/jmi.67.217Crossref PubMed Scopus (1) Google Scholar Pudas et al reported cases of identical twin ice hockey players.17Pudas T. Koskinen S.K. Hiltunen A. Mattila K.T. Osteochondritis dissecans of the humeral capitellum in identical twins.Acta Radiol Short Rep. 2012; 1 (arsr.2012.120004. https://doi.org/10.1258/arsr.2012.120004)PubMed Google Scholar The twin cases in this study showed very similar image findings and clinical courses compared to those of the twin OCD cases reported in the literature.10Kenniston J.A. Beredjiklian P.K. Bozentka D.J. Osteochondritis dissecans of the capitellum in fraternal twins: case report.J Hand Surg Am. 2008; 33: 1380-1383https://doi.org/10.1016/j.jhsa.2008.05.008Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar,13Matsuura T. Wada K. Suzue N. Iwame T. Fukuta S. Sairyo K. Bilateral osteochondritis dissecans of the capitellum in fraternal twins: a case report.JBJS Case Connect. 2017; 7: e44https://doi.org/10.2152/jmi.67.217Crossref PubMed Scopus (1) Google Scholar,17Pudas T. Koskinen S.K. Hiltunen A. Mattila K.T. Osteochondritis dissecans of the humeral capitellum in identical twins.Acta Radiol Short Rep. 2012; 1 (arsr.2012.120004. https://doi.org/10.1258/arsr.2012.120004)PubMed Google Scholar Genetic factors may account for a large proportion of several potential factors for OCD. Screening using ultrasonography enables early detection and provides an opportunity for successful conservative treatment.11Matsuura T. Iwame T. Iwase J. Sairyo K. Osteochondritis dissecans of the capitellum: review of the literature.J Med Invest. 2020; 67: 217-221https://doi.org/10.2152/jmi.67.217Crossref PubMed Google Scholar Harada et al reported that ultrasonography was useful and reliable (as confirmed by radiographic findings) for detecting elbow injuries.8Harada M. Takahara M. Sasaki J. Mura N. Ito T. Ogino T. Using sonography for the early detection of elbow injuries among young baseball players.Am J Roentgenol. 2006; 187: 1436-1441https://doi.org/10.2214/AJR.05.1086Crossref PubMed Scopus (61) Google Scholar Ultrasonography is very useful for routine examination of OCD because it is noninvasive and cost-effective.15Parker L. Nazarian L.N. Carrino J.A. Morrison W.B. Grimaldi G. Frangos A.J. et al.Musculoskeletal imaging: medicare use, costs, and potential for cost substitution.J Am Coll Radiol. 2008; 5: 182-188https://doi.org/10.1016/j.jacr.2007.07.016Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar Ultrasonographic imaging has been used to diagnose early OCD without elbow pain in baseball elbow medical examinations.11Matsuura T. Iwame T. Iwase J. Sairyo K. Osteochondritis dissecans of the capitellum: review of the literature.J Med Invest. 2020; 67: 217-221https://doi.org/10.2152/jmi.67.217Crossref PubMed Google Scholar Our cases also showed asymptomatic OCD on ultrasonography and were treated conservatively. Unfortunately, continuing baseball after conservative treatment exacerbated the condition of OCD, and surgical treatment was required. However, the period of pitching restrictions was off-season, and it was possible to return to competitive sport four months after the surgery. Early detection of OCD by ultrasonography may have had a positive effect on minimizing the withdrawal period in these cases. We have described the OCD of the capitellum in identical twin baseball players. As these were identical lesions in identical twins, this supports the theory that OCD has a genetic background. For OCD, screening by ultrasonography is considered effective for early detection and provides an opportunity for early treatment.

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