DOI: 10.1148/rg.262055126
RadioGraphics 2006;26:581-586
© RSNA, 2006
Best Cases from the AFIP
Dysplasia Epiphysealis Hemimelica of the Patella1
Cyrillo R. Araujo, Jr, MD,
Simone Montandon, MD,
Cristiano Montandon, MD,
Kim-Ir-Sen S. Teixeira, MD, PhD,
Frederico B. Moraes, MD and
Marise A. R. Moreira, MD, PhD
1 From the Departments of Diagnostic Imaging (C.R.A., S.M., C.M., K.S.T.), Orthopedics (F.B.M.), and Pathology (M.A.R.M.), Hospital das Clinicas, 1a Av s/n, Setor Universitario, Campus I, Universidade Federal de Goias, 74605-020 Goiania, Goias, Brazil. Received May 31, 2005; revision requested June 30 and received July 28; accepted July 29. All authors have no financial relationships to disclose.
Address correspondence to C.R.A. (e-mail: radiologia{at}brturbo.com).
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History
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A 6-year-old boy developed progressive pain and swelling of the right knee over several months. There was no history of fever, trauma, or other joint abnormality. Physical examination revealed tenderness on palpation, mild restriction in the range of motion, tissue swelling, and mild warmth. One month earlier, radiography was performed and did not show any joint abnormality. Laboratory results were normal except for an increased hemosedimentation rate. The initial suspected diagnosis was juvenile chronic arthritis.
The patient remained symptomatic 5 months after initial evaluation despite medical therapy. At that time, radiographs revealed a knee joint effusion with irregular ossification and enlargement of the patella. The diagnosis of an infectious arthritis was suggested, and the case was referred to the orthopedic service.
Two months later, at examination, the patient presented with right knee tenderness, decrease in the range of motion, tissue swelling, and mild warmth. In addition, bilateral genu valgum, quadriceps hypotrophy, and joint effusion were noted. A firm protuberance was also palpated on the anterior aspect of the right knee. There was no limb-length discrepancy. At this time, knee radiography showed an enlarged right patella with increasing areas of irregular bone opacity (Fig 1), and biopsy was recommended. The biopsy was performed, but not enough tissue was obtained for a diagnosis to be made.
One year and 2 months after the first visit, radiography showed a marked increase in the size of the patella with osseous proliferation. A second biopsy was performed, and a diagnosis of a benign osteocartilaginous tumor such as an osteochondroma was made. After a conference between members of the pathology and radiology departments, the diagnosis of dysplasia epiphysealis hemimelica (DEH) of the patella was proposed. One month later, a partial patellectomy was performed.
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Imaging Findings
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Consecutive radiographic studies of the right knee showed progressive enlargement and irregularity of the patella associated with osseous proliferation. The two sets of radiographs are shown and were obtained about 7 months apart. The initial radiographic study, in the lateral projection (Fig 1), showed an enlarged patella with sclerosis and irregularity. A second examination showed a marked increase in the size of the patella with extensive osseous proliferation (Fig 2).
Computed tomographic (CT) scans obtained with soft-tissue (Fig 3a) and bone (Fig 3b) windows showed expansion of the medial ossification center of the patella (Fig 3a). Expansion rather than cortical and medullary continuity of the lesion could be best depicted on the bone window images (Fig 3b). A large joint effusion was also noted (Fig 3a).
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Figure 3a. CT scans obtained with soft-tissue (a) and bone (b) windows show an osteochondral tumor expanding the medial ossification center of the patella (arrow). Note the large joint effusion (arrowheads in a). The lateral ossification center of the patella is present and is slightly displaced (arrowhead in b).
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Figure 3b. CT scans obtained with soft-tissue (a) and bone (b) windows show an osteochondral tumor expanding the medial ossification center of the patella (arrow). Note the large joint effusion (arrowheads in a). The lateral ossification center of the patella is present and is slightly displaced (arrowhead in b).
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Magnetic resonance (MR) imaging was performed in the sagittal plane for intermediate-weighted images (Fig 4a) and in the axial plane for T1-weighted images (Fig 4b). A detailed evaluation of the findings revealed a 3.5-cm (anteroposterior) x 6-cm (mediolateral) x 8.5-cm (craniocaudal) mass arising from the medial ossification center of the patella (Fig 4b); the mass had heterogeneous signal intensity with all MR imaging sequences. On the axial views, the lateral ossification center appeared to be normal and displaced (Fig 4b). The intermediate signal intensity on the T1- and intermediate-weighted images represented the cartilaginous content of the lesion, which was similar in appearance to the epiphyseal cartilage of the distal femur (Fig 4a).
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Figure 4a. Sagittal intermediate-weighted (a) and axial T1-weighted (b) MR images show the osteochondral tumor expanding the medial ossification center of the patella (arrow in b). The lateral ossification center is present and is slightly displaced (arrowhead in b). The areas of low signal intensity within the lesion indicate regions of calcification or ossification that have expanded since the initial radiographic studies. The intermediate signal intensity within the lesion on the intermediate- and T1-weighted images represents the cartilaginous content of the lesion; this cartilaginous content is similar in appearance to the epiphyseal cartilage of the distal femur (arrows in a).
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Figure 4b. Sagittal intermediate-weighted (a) and axial T1-weighted (b) MR images show the osteochondral tumor expanding the medial ossification center of the patella (arrow in b). The lateral ossification center is present and is slightly displaced (arrowhead in b). The areas of low signal intensity within the lesion indicate regions of calcification or ossification that have expanded since the initial radiographic studies. The intermediate signal intensity within the lesion on the intermediate- and T1-weighted images represents the cartilaginous content of the lesion; this cartilaginous content is similar in appearance to the epiphyseal cartilage of the distal femur (arrows in a).
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On the basis of these findings and the signal intensity characteristics, the impression was that the patellar lesion likely represented an osteochondroma of the medial ossification center.
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Pathologic Evaluation
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One month after his last visit, the patient underwent surgery. The surgeon was able to excise the lesion together with the medial ossification center of the patella (Fig 5a), preserving its lateral center (not seen in Fig 5). At gross pathologic analysis, the surgical specimen consisted of a segment of tissue measuring 10 x 6 x 5 cm, which was grayish-white, of firm consistency, and covered with a whitish cartilaginous cap (Fig 5b). On cutting, there was spongy bone in the middle of the lesion, surrounded by whitish tissue of cartilaginous aspect.
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Figure 5a. (a) Photograph obtained during surgery shows the whitish bright lesion with a lobulated contour (arrows) in the medial aspect of the knee. (b) Photograph obtained after excision shows the osteochondral tumor with its whitish cartilaginous cap, which is better seen after excision.
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Figure 5b. (a) Photograph obtained during surgery shows the whitish bright lesion with a lobulated contour (arrows) in the medial aspect of the knee. (b) Photograph obtained after excision shows the osteochondral tumor with its whitish cartilaginous cap, which is better seen after excision.
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At low power, microscopic sections through the lesion showed areas of an osteochondroma. The chondrocytes had an orderly arrangement in the cartilaginous cap, and there was maturation into trabecular-appearing bone (Fig 6a). At high power, the lesion was moderately cellular, containing chondrocytes with irregular nuclei (Fig 6b). Mitoses were absent.
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Figure 6a. (a) Low-power photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows areas of normal bone (arrow), which are indicative of an osteochondroma. (b) High-power photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows areas of abundant enchondral calcification (arrows), which are indicative of an osteochondroma. There is no evidence of malignancy.
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Figure 6b. (a) Low-power photomicrograph (original magnification, x100; hematoxylin-eosin stain) shows areas of normal bone (arrow), which are indicative of an osteochondroma. (b) High-power photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows areas of abundant enchondral calcification (arrows), which are indicative of an osteochondroma. There is no evidence of malignancy.
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The histologic diagnosis was a benign osteocartilaginous lesion or an osteochondroma. The case was discussed during a radiologic-pathologic conference, and the findings were best interpreted as being compatible with the diagnosis of DEH.
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Discussion
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DEH is a rare developmental bone dysplasia characterized by an osteocartilaginous tumor arising from an epiphysis (1). Historically, DEH has been referred to by many names. Mouchet and Berlot (2) originally described it as a "tarsomegalie" in 1926. Trevor (3) described this entity in 1950 and used the name tarsoepiphyseal aclasis. Subsequently, Fairbank (4) coined the most frequently used term dysplasia epiphysealis hemimelica in 1956. Therefore, this abnormality is also commonly referred to as Trevor-Fairbank disease. This entity was mostly described in epiphyses and also occurs in sesamoid bones, such as the patella.
This disorder affects epiphyses in children, usually in the lower limb, predominantly the knee and ankle. The lesion is characteristically hemimelic, involving either the medial or lateral aspect of the ossification center, with the former site affected twice as frequently as the latter (1,5).
The general prevalence has been reported as 1 in 1,000,000, and the etiology is unknown. This disease is nonhereditary. Most patients are first seen between the ages of 2 and 14 years, and the condition is three times more common in boys (6,7).
Cases are classified into localized, classic, or generalized types. The localized form affects a single bone, usually in the hindfoot or ankle. The classic form affects more than one area in a single lower extremity, particularly about the knee and ankle, and accounts for more than two-thirds of cases. In the generalized or severe form, the whole lower limb is involved, from pelvis to foot (8,9).
Typically, the initial presentation is painless, asymmetric, and firm swelling due to cartilaginous overgrowth on one side of the joint in a lower extremity. Other signs include limb wasting, valgus or varus deformity, and sometimes limb-length discrepancy (5).
The most common sites in order of decreasing frequency are the distal femur, proximal tibia, talus, tarsal navicular, and first cuneiform. Both upper extremity involvement and bilateral involvement by the disease have been reported but are exceedingly rare (10–12).
As for involvement of the patella, primary tumors of this bone seem to be rare; however, there are some scarce references to an osteochondroma involving the patella in the German (13), French (14), and Russian (15) literature. The only reported case in the English literature seems to be the one described by Enriquez et al (16) in 1981.
Radiologic findings are often characteristic. Radiography typically shows an irregular mass with focal ossification arising from one side of the affected epiphysis or sesamoid bone. The lesions may be single or multiple, enlarge with skeletal growth, and may be associated with joint deformity. With maturation, the lesion ossifies and becomes confluent with the underlying bone. Premature closure of the physis with resultant deformity and occasional limb discrepancy may also be seen. Articular surface irregularity may lead to early secondary osteoarthritis. There may also be secondary involvement of the metaphysis, resulting in undertubulation of bone (1,5). In our patient, the osteochondroma arose from the medial ossification center of the patella, expanding it and displacing the lateral one, as was well demonstrated in radiologic studies and the surgical specimen.
CT helps in definition of the anatomic relations between the mass and the bone, such as cortical and medullary bone continuity (1); however, in some cases of epiphyseal or sesamoid bone involvement, this continuity may not be readily apparent and rather one may observe expansion of the entire bone. In our patient, CT was important to show the expansion of the medial ossification center of the patella. CT can also provide information about the extent of the lesion, but the relationship in planes other than the axial and the articular surfaces are better evaluated with MR imaging.
It is well known that MR imaging is accurate in identifying the lesion and determining its anatomic relations (5,17). It shows the extent of the osteochondral tumor, providing the status of the patellar surface and soft-tissue changes. MR imaging is also important to reveal the signal intensity of the lesion and its continuity with the primary site, as well as secondary changes in menisci, tendons, ligaments, and muscle. Gadolinium contrast material may play a role in cases of a complication or a rapidly growing osteochondroma. In our patient, the MR imaging signal intensities were well demonstrated and consistent with cartilaginous and osseous tissue (Fig 4).
At pathologic analysis, the lesion is a lobulated mass with a cartilaginous cap (Fig 5b) protruding from the epiphysis or, as in our patient, from the patella. Sometimes, the lesion cannot be differentiated from the normal epiphysis.
Histologically, the epiphyseal lesion is a benign osteochondroma, consisting of a base of normal bone and hyaline cartilage with abundant enchondral ossification. The basic pathologic process appears to be abnormal cartilage proliferation in an epiphysis, sesamoid bone, or tarsal and carpal bones with associated enchondral ossification. Malignant transformation has not been reported in DEH, and surveillance is performed basically to assess the progression of the disease (1,18).
The differential diagnoses include myositis ossificans; infection; chronic infantile neurologic, cutaneous, and articular (CINCA) syndrome; tumoral calcinosis; synovial osteochondromatosis; and vascular or parasitic calcification (5).
Normally, biopsy is not necessary because of the diagnostic radiologic features. However, given the fact that our patient presented with this entity in an unusual location and had some differential diagnoses that could change the management, biopsy was performed.
The treatment options are simple observation or surgical excision. Surgery should be undertaken if the lesion is causing pain or deformity or interfering with function. It is suggested that early surgical excision be performed before functional disability is present to prevent degenerative changes in the affected joint. The deformity can be treated with excision of the mass and corrective osteotomy (19).
The recurrence rate of the deformity is reported to be high (19). In our patient, the surgeon was able to excise the entire lesion within the medial ossification center of the patella, mobilizing the tendons and inserting them into the lateral ossification center, which was found to be free of the disease, therefore preserving the function of the patellofemoral joint. The patient is now being followed up at our institution, and his knee appears to be normal 1 year after the resection, without any complaints. The patellofemoral joint was reestablished and seems to be stable and well developed.
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Conclusions
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DEH is an uncommon disease representing an osteochondroma arising from one or more epiphyses. We have described a case of DEH of the patella in a 6-year-old boy who was treated surgically, emphasizing the imaging findings and performing pathologic correlation.
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Footnotes
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Abbreviations: DEH = dysplasia epiphysealis hemimelica
Editor’s Note.—Everyone who has taken the course in radiologic pathology at the Armed Forces Institute of Pathology (AFIP) remembers bringing beautifully illustrated cases for accession to the Institute. In recent years, the staff of the Department of Radiologic Pathology has judged the "best cases" by organ system, and recognition is given to the winners on the last day of the class. With each issue of RadioGraphics, one or more of these cases are published, written by the winning resident. Radiologic-pathologic correlation is emphasized, and the causes of the imaging signs of various diseases are illustrated.
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References
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- Kuo RS, Bellemore MC, Monsell FP, Frawley K, Kozlowski K. Dysplasia epiphysealis hemimelica: clinical features and management. J Pediatr Orthop 1998;18(4):543–548.[CrossRef][Medline]
- Mouchet A, Berlot J. La tarsomegalie. J Radiol Electrol 1926;10:289–293.
- Trevor D. Tarso-epiphysial aclasis: a congenital error of epiphysial development. J Bone Joint Surg Br 1950;32-B(2):204–213.
- Fairbank TJ. Dysplasia epiphysialis hemimelica (tarso-ephiphysial aclasis). J Bone Joint Surg Br 1956;38-B(1):237–257.
- Lang IM, Azouz EM. MRI appearances of dysplasia epiphysealis hemimelica of the knee. Skeletal Radiol 1997;26(4):226–229.[CrossRef][Medline]
- Shinozaki T, Ohfuchi T, Watanabe H, Aoki J, Fukuda T, Takagishi K. Dysplasia epiphysealis hemimelica of the proximal tibia showing epiphyseal osteochondroma in an adult. Clin Imaging 1999;23(3):168–171.[CrossRef][Medline]
- Wynne-Davies R, Hall CM, Apley AG. Dysplasia epiphysealis hemimelica. In: Wynne-Davies R, Hall CM, Apley AG, eds. Atlas of skeletal dysplasias. New York, NY: Churchill Livingstone, 1985; 539–543.
- Azouz EM, Slomic AM, Marton D, Rigault P, Finidori G. The variable manifestations of dysplasia epiphysealis hemimelica. Pediatr Radiol 1985; 15(1):44–49.[CrossRef][Medline]
- Murphey MD, Choi JJ, Kransdorf MJ, Flemming DJ, Gannon FH. Imaging of osteochondroma: variants and complications with radiologic-pathologic correlation. RadioGraphics 2000;20(5): 1407–1434.[Abstract/Free Full Text]
- Azouz EM, Slomic AM, Archambault H. Upper extremity involvement in Trevor disease. J Can Assoc Radiol 1984;35(2):209–211.[Medline]
- Takeuchi H, Ito K, Ogino T, Hasegawa T, Kita-mura M, Ishii S. A case of osteocartilaginous mass involving the coronoid process of the ulna: solitary osteochondroma or dysplasia epiphysealis hemimelica? J Shoulder Elbow Surg 2003;12(5):510–513.[CrossRef][Medline]
- Merzoug V, Wicard P, Dubousset J, Kalifa G. Bilateral dysplasia epiphysealis hemimelica: report of two cases. Pediatr Radiol 2002;32(6):431–434.[CrossRef][Medline]
- Maurer HJ. Symmetrical osteocartilaginous exostoses (osteochondroma) of the patella [in German]. Fortschr Geb Rontgenstr Nuklearmed 1963;98:771–772.[Medline]
- Louis R, Pouye I, Conty RC, Quenum C, Ouiminga RM. Voluminous osteochondroma of the knee cap: patellectomy [in French]. Bull Soc Med Afr Noire Lang Fr 1968;13(3):722–729.[Medline]
- Sadykhov AG. Osteochondroma of the patella [in Russian]. Ortop Travmatol Protez 1962;23:77–78.[Medline]
- Enriquez J, Quiles M, Torres C. A unique case of dysplasia epiphysealis hemimelica of the patella. Clin Orthop Relat Res 1981;160:168–171.
- Peduto AJ, Frawley KJ, Bellemore MC, Kuo RS, Foster SL, Onikul E. MR imaging of dysplasia epiphysealis hemimelica: bony and soft-tissue abnormalities. AJR Am J Roentgenol 1999;172(3): 819–823.[Abstract/Free Full Text]
- Lin YH, Chou YJ, Yeh LR, Chen CKH, Pan HB, Yang CF. Dysplasia epiphysealis hemimelica or Trevor’s disease: a case report. Chin J Radiol 2001;26(5):215–220.
- Keret D, Spatz DK, Caro PA, Mason DE. Dysplasia epiphysealis hemimelica: diagnosis and treatment. J Pediatr Orthop 1992;12(3):365–372.[Medline]
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History
Imaging Findings
