M u s c u l o s k e l e t a l I m a g i n g • C l i n i c a l Pe r s p e c t i ve La Rocca Vieira et al. MRI of Cortical Desmoid
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Musculoskeletal Imaging Clinical Perspective
MRI Features of Cortical Desmoid in Acute Knee Trauma Renata La Rocca Vieira1 Jenny T. Bencardino1 Zehava Sadka Rosenberg1 George Nomikos 2
OBJECTIVE. The purpose of this study was to describe the MRI features of cortical desmoids associated with acute trauma. CONCLUSION. Marrow edema, periostitis, and adjacent soft-tissue edema can be seen in cases of cortical desmoid associated with acute trauma.
La Rocca Vieira R, Bencardino JT, Rosenberg ZS, Nomikos G
ortical desmoids, also known in the medical literature as distal femoral cortical irregularities, are benign self-limiting fibrous or fibroosseous lesions that most frequently occur in the medial supracondylar femur (Fig. 1). They are most prevalent among boys 10–15 years old and are believed to be tug lesions secondary to traction injury at the insertion of the adductor magnus aponeurosis or at the origin of the medial head of the gastrocnemius tendon [1–4]. Although it has been considered a chronic and repetitive injury, this process also may be related to an episode of acute knee trauma, not well recalled by physically active children. The purposes of this study were to describe the MRI features of cortical desmoid of the medial supracondylar femur associated with acute knee trauma and to review the literature on this entity.
Keywords: cortical desmoid, distal femoral cortical irregularities, femur, knee, MRI, trauma DOI:10.2214/AJR.10.4815 Received April 16, 2010; accepted after revision June 16, 2010. 1 Department of Radiology, New York University Hospital for Joint Diseases, 301 E 17th St., 6th Fl., New York, NY 10003-3899. Address correspondence to R. La Rocca Vieira (
[email protected]). 2 Department of Radiology, Georgetown University Hospital, Washington, DC.
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Materials and Methods Institutional review board approval for this retrospective study was obtained with waiver of informed consent. In a 1-year period we collected images from 11 1.5-T MRI examinations of 11 patients (six boys, five girls; age range, 9–16 years; mean, 14.9 years) with a clinical history of acute knee trauma within 4 weeks before MRI and findings consistent with a cortical desmoid in the medial supracondylar femur. Cortical desmoid was defined as a focal intracortical defect of the medial supracondylar femur at the site of origin of the medial head of the gastrocnemius tendon or the site of insertion of the adductor magnus tendon. The MRI studies were retrospectively reviewed in consensus by two musculoskeletal radiologists with 12 and 25 years of experience. The patients’ medical records were reviewed.
All patients underwent MRI with a 1.5-T system (Magneton Vision, Siemens Healthcare; Signa, GE Healthcare). The MRI protocol consisted of axial proton density (TR/TE, 2,000/32), axial T2-weighted fat-suppressed (3,800/56), coronal proton density (2,300/12), coronal fat-suppressed T2-weighted (2,400/56), sagittal proton density (2,900/21), and sagittal fat-suppressed T2-weighted (2,750/56) images of the knee. All MRI sections were obtained with a slice thickness of 3–4 mm, field of view of 14–16 cm, and matrix size of 256 × 256. Eleven cortical desmoids were characterized on the basis of the following MRI findings: size and signal characteristics of the cortical irregularity in the medial supracondylar femur, presence of associated periosteal or subperiosteal edema and medial supracondylar marrow edema, and relations between the cortical irregularity and the origin of the medial head of the gastrocnemius tendon and the adductor magnus tendon insertion. The presence of associated traumatic injuries of the menisci, ligaments, extensor mechanisms, and bone was evaluated.
Results All 11 patients (Table 1) had a history of substantial acute trauma and knee pain within 4 weeks before MRI. The size range of the cortical desmoids was 8–12 mm (Figs. 2–4). In all cases, the defects were predominantly hypointense or isointense on proton density– weighted images and hyperintense on T2weighted fat-suppressed images. Nine of the 11 patients had associated bone marrow edema centered in the posteromedial femoral metaphysis or epiphysis. All patients had periostitis, swelling, and edema at the origin of the medial head of the gastrocnemius tendon (Figs. 2 and 3). One patient had additional
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MRI of Cortical Desmoid
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Fig. 1—12-year-old boy with knee pain. A and B, Anteroposterior (A) and lateral (B) radiographs of knee show cortical desmoid. Defect with surrounding sclerosis is evident in medial supracondylar femur (arrow, A). Cortical bone overgrowth (arrow, B) also is present.
swelling at the insertion of the adductor magnus tendon. Other associated signs of trauma were found in eight patients, including injury to the extensor mechanism (four patients), anterior cruciate ligament sprain (two patients), medial meniscal abnormality (one partial peripheral tear, one parameniscal cyst), and incomplete fracture of the distal femur (one patient). Two of the 11 patients were referred from the community to our institutions for biopsy because of suspected osteogenic sarcoma. However, the typical location and MRI findings helped to characterize the lesions as acute cortical desmoids. The patients were treated conservatively, and medical follow-
up 6 months after clinical treatment showed interval resolution of knee pain. Discussion The entity cortical desmoid has been described by a variety of names used interchangeably, including distal femoral cortical irregularity, periosteal desmoid, juxtacortical desmoid, and avulsive cortical irregularity [5]. Adding to the confusion, the term desmoid implies an aggressive lesion. Cortical desmoids are self-limiting reactive fibroosseous lesions considered to be a variant of fibrous cortical defect, which has benign biologic and clinical behavior [6, 7]. Cortical desmoids are most prevalent among boys 10–15 years
TABLE 1: MRI Characteristics of Cortical Desmoids in Patients With Clinical History of Acute Trauma (n = 11) Characteristic Size
Result 8–10 mm
Signal characteristics Proton density–weighted images
Hypointense, isointense
T2-weighted fat-saturated images
Hyperintense
Prevalence of findings (%) Periosteal and subperiosteal edema
100 (11)
Bone marrow edema
81.8 (9)
Abnormality of medial head of gastrocnemius
100 (10)
Abnormality of adductor magnus Note—Values in parentheses are numbers of patients.
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old [1–4]. Although the lesions usually are asymptomatic, swelling and pain can be present [5]. Although our patients had symptoms, we cannot clearly attribute the symptoms to the presence of the desmoids because of the presence of associated posttraumatic findings, including injuries to the extensor mechanism, anterior cruciate ligament, and menisci. Cortical desmoids are believed to result from excessive metaphysial cortical remodeling, typically seen in the distal supracondylar femur. They are present in the growing skeleton from mid childhood through late adolescence. They can be bilateral and are typically larger in the dominant extremity [2]. The pathogenesis of cortical desmoids may be a combination of excessive metaphysial cutback, the posterior and medial aspect of the distal femur growing more rapidly than any other physis in the body, and mechanical pull at the medial head of gastrocnemius origin, producing a defect with subsequent fibrous repair [2]. Craigen et al. [8] reviewed the cases of seven children with knee pain over the medial femoral condyle and radiologic findings compatible with desmoids of the medial distal femur. In five patients who underwent biopsy, histologic changes were consistent with musculotendinous avulsion. Histologically, cortical desmoids are produced by increased osteoclastic activity with resorption of the cortical surface. The defects are typically filled with a cellular to dense desmoplastic proliferating reparative fibrous tissue [2]. The diagnosis of cortical desmoid traditionally has been based on findings on conventional radiographs. On radiographs, cortical desmoid appears as an irregularity or defect along the posterior cortex of the femur [9]. Resnick and Greenway [10] classified cortical desmoids on the basis of morphologic appearance as concave or proliferative. Suh et al. [9] later introduced a classification that included concave, convex, and divergent shapes. They found that regardless of differences in shape, on MR images all cortical desmoids were situated at the origin of the medial gastrocnemius tendon. Those authors proposed that the different shapes of desmoids reflected varying responses to mechanical traction at this site. Cortical desmoids classically appear on MR images as an area of cortical irregularity along the posteromedial aspect of the distal femur. They are hypointense on T1-weighted images and hyperintense on T2-weighted images. On both types of images, the lesions have a dark rim at or near the sites of
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La Rocca Vieira et al.
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Fig. 2—13-year-old girl with cortical desmoid and history of acute trauma. A–C, Axial T2-weighted fat-suppressed (A), sagittal proton density–weighted fat-suppressed (B), and proton density–weighted (C) MR images show hyperintense wellmarginated juxtacortical lesion (open arrow) associated with bone marrow edema and periostitis. Intratendinous and peritendinous T2 hyperintensity at origin of medial head of gastrocnemius tendon (solid arrow) also is present. Bone marrow contusion of medial femoral condyle and joint effusion are evident.
the bony attachment of the medial head of the gastrocnemius muscle [9, 11]. MRI can provide additional information regarding associated soft-tissue and osseous abnormalities, as found in our series. At MRI, all of our patients had periostitis and swelling and soft-tissue edema at the origin of the medial head of the gastrocnemius tendon. Most of these patients also had bone
Fig. 3—16-year-old boy with cortical desmoid and history of acute trauma. Sagittal fat-suppressed proton density–weighted (A) and axial T2*-weighted gradient-echo (B) MR images show hyperintense well-marginated juxtacortical lesion (open arrow, B) associated with metaphysial marrow edema (asterisk, A) in medial supracondylar femur. Adjacent edema at origin of medial head of gastrocnemius tendon (arrowhead, A; solid arrow) also is present.
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marrow edema and associated traumatic injuries, including extensor mechanism and medial meniscal abnormalities and anterior cruciate ligament sprain and incomplete fracture of the distal femur. The presence of associated pathologic changes suggests that trauma with hyperflexion of the knee and valgus force may contribute to distraction of the posteromedial aspect of the knee.
In two of our patients, the diagnosis of malignant tumor was initially entertained in part because of the presence of extensive associated marrow and soft-tissue edema. We believe, however, that familiarity with the typical location and signal characteristics of cortical desmoids and the possible associated MRI features should aid in differentiating cortical desmoids from true malignant tumors. The
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MRI of Cortical Desmoid Fig. 4—14-year-old female ballet dancer with cortical desmoid and history of acute trauma and posterior knee pain. A, Sagittal proton density–weighted MR image shows hyperintense well-marginated juxtacortical lesion (arrow) with adjacent bone marrow edema. B, Sagittal proton density–weighted image of knee obtained 9 months before incident for evaluation of chronic knee pain shows same well-marginated juxtacortical lesion (arrow) as in A but no bone marrow edema. Hypothesized diagnosis is cortical desmoid associated with acute trauma superimposed on previous cortical irregularity.
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typical radiographic appearance and the age of the patient may be most important with respect to this differentiation. As a routine, we do not advocate repeating imaging if the typical features are present. The presence of marrow edema, periostitis, and intratendinous or peritendinous edema of
the adjacent medial head of gastrocnemius and adductor magnus tendons in many of these lesions supports the notion that desmoids can undergo acute remodeling in the setting of a recent traumatic event likely related to traction at the origin of the medial gastrocnemius tendon and that cortical desmoids lacking marrow
edema (Fig. 5) are likely related to a healed traction injury. It is important to bear in mind that many of these patients are active children who may continue to aggravate the initial insult through repetitive trauma. The differential diagnosis of cortical desmoid includes fibrous cortical defect, posterior
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Fig. 5—14-year-old girl with cortical desmoid and no history of acute trauma. A–C, Sagittal proton density–weighted (A), sagittal proton density–weighted fat-suppressed (B), and axial T2-weighted fat-suppressed (C) images show wellmarginated juxtacortical lesion (open arrow) at superomedial aspect of distal femur. Adjacent bone marrow edema, periostitis, and edema at origin of medial head of gastrocnemius muscle are absent. Posterior femoral stripe (solid arrows, C) is evident.
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La Rocca Vieira et al. Fig. 6—Differential diagnosis. A, 13-year-old boy with incidental finding of fibrous cortical defect and history of discoid meniscus. Oblique coronal proton density–weighted fatsuppressed image shows cortically based, welldefined lesion (arrow) along medial margin of distal femoral diaphysis with no associated bone marrow edema. B, 13-year-old boy with posterior distal femoral stripe and history of anterior knee pain. Oblique sagittal T2-weighted fat-suppressed MR image shows highsignal-intensity stripe (arrow) along posterior surface of distal femoral metaphysis.
distal femoral stripes, and parosteal osteosarcoma. Fibrous cortical defects, believed by some authors [6, 7] to be a variant of desmoid lesions, can be seen elsewhere in the skeleton and are part of a spectrum of conditions, including nonossifying fibroma, fibroxanthoma, and fibrous histiocytoma. These lesions likely are divergent manifestations of a single entity based on size, morphologic features, timing, and location. The histologic characteristics are a whorled storiform (straw mat–like) spindle cell pattern, giant cells, xanthoma cells, and occasionally, hemosiderin pigment [2]. The MRI characteristics of a fibrous cortical defect in the distal femur can be indistinguishable from those of a cortical desmoid except for the location of the former, which may not necessarily be the origin of the medial head of the gastrocnemius tendon (Fig. 6). Posterior distal femoral stripes, a normal finding on MR images of all skeletally immature patients, should not be confused with cortical desmoids. Although both occur in the distal metaphysis, posterior distal femoral stripes and desmoids are likely unrelated. Cortical desmoids occur only at the site of tendon attachments. They are also more focal than metaphysial stripes and are commonly seen along the medial aspect of the distal femur. Femoral stripes represent normal fibrovascular tissue between the periosteum and bone and are distributed along the entire posterior portion of the distal femur on transverse and oblique sagittal images. The
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high signal intensity of posterior femoral stripes is likely due to the presence of highly vascular subperiosteal loose fibrous tissue [12] (Fig. 6). Osteogenic sarcoma, particularly the parosteal variant, can occur in the posteromedial supracondylar femoral fossa. Osteogenic sarcoma in this location, however, is typically found in older patients and has aggressive features such as cortical destruction and soft-tissue mass. Our study had several limitations, including the retrospective design, small patient sample, lack of correlation with histopathologic findings, lack of a control group, and lack of imaging follow-up. In addition, the readers were not blinded to history of trauma or information about the patient’s sports activities. We conclude that bone marrow edema, periostitis, and edema and swelling of the adjacent soft tissues are frequent MRI findings in patients with cortical desmoids in the medial supracondylar femur in association with acute knee trauma. We hypothesize that cortical desmoids with bone marrow edema, periostitis, and soft-tissue swelling likely represent an acute stage of remodeling after tendon traction injury.
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