You are in: eMedicine Specialties > Radiology > MUSCULOSKELETAL Osteochondroma and OsteochondromatosisArticle Last Updated: Jul 29, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia Ali Nawaz Khan is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the United States, Royal College of Radiologists, and Royal College of Surgeons of England Coauthor(s): Mohammed Jassim Al-Salman, MBBS, Consulting Radiologist, King Abdul Aziz Medical City, National Guard Hospital; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute Editors: Michael A Bruno, MD, Associate Professor, Departments of Radiology and Medicine, Pennsylvania State University College of Medicine; Director, Radiology Quality Management Services, Milton S Hershey Medical Center, Pennsylvania State University College of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Theodore E Keats, MD, Professor, Departments of Radiology and Orthopedics, University of Virginia School of Medicine; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington Author and Editor Disclosure Synonyms and related keywords: osteochondroma, osteochondromatosis, hereditary multiple exostoses, HME, multiple osteocartilaginous exostoses, diaphyseal achalasia, diaphysial achalasia, multiple hereditary osteochondromata, multiple congenital osteochondromata, diaphyseal aclasis, diaphysial aclasis, chondral osteogenic dysplasia of direction, chondral osteoma, deforming chondrodysplasia, dyschondroplasia exostosing disease, exostotic dysplasia, multiple osteomatoses osteogenic disease, familial bony spurs, metaphyseal spurs, multiple epiphyseal dysplasia, dysplasia epiphysealis hemimelica, Trevor disease, Trevor's disease INTRODUCTIONSection 2 of 12
  BackgroundAn osteochondroma is a cartilage-covered bony excrescence (exostosis) that arises from the surface of a bone. Osteochondromas, which are the most common bone tumors in children, may be solitary or multiple, and they may arise spontaneously or as a result of previous osseous trauma. An osteochondroma can affect any bone preformed in cartilage. The true prevalence of solitary osteochondromas is not known, because many asymptomatic lesions go undiagnosed. Hereditary multiple exostoses (HME), also known as osteochondromatosis, is an inherited, autosomal dominant disorder in which multiple osteochondromas are seen throughout the skeleton. John Hunter was the first to comment on HME and described a patient with the condition in his Lectures on the principles of surgery (1786).1 The first description of a family with HME was published by Boyer, in 1814.2 In 1825, a second family with HME was described.3 Most osteochondromas, solitary or multiple, arise from tubular bones and are metaphyseal in location. Multiple epiphyseal dysplasia and dysplasia epiphysealis hemimelica (DEH), also known as Trevor disease, are autosomal dominant conditions in which the chondromas arise from the epiphysis and cause joint problems. Patients with HME may have anywhere from 2 osteochondromas to hundreds of them. Most solitary osteochondromas are discovered incidentally in children and adolescents. A painless skeletal swelling or a slowly growing mass is the usual mode of presentation. HME leads to abnormalities such as palpable bony masses and limb shortening in the first or second decade of life. Complications of osteochondromas include fractures, bony deformities, neurologic and vascular injuries, bursa formation, and malignant transformation. Advances have added to the understanding of the molecular and genetic bases of HME. PathophysiologySolitary osteochondromas Solitary osteochondromas are a relatively frequent finding and are regarded as true tumors or growth disturbances. They form in parts of the skeleton that develop from endochondral ossification and thus are closely linked to physes. Solitary osteochondromas vary considerably in size; the average lesion arising from a tubular bone is approximately 4 cm. Osteochondromas arising from flat bones tend to be larger. On pathologic sections, the osteochondroma is found to have a cartilaginous cap. Histologically, the cartilaginous cap is identical to the physeal growth plate. During active growth, the cap is composed of hyaline cartilage. The thickness of the cap is correlated with the age of the patient, and the cap decreases in size as patients age. In children and adolescents, the cap may be as thick as 3 cm, whereas in older patients, it may be nonexistent. A thick, cartilaginous cap (>1 cm) in adults should raise the possibility of malignant transformation. Osteochondromas Osteochondromas develop due to a beaked failure of constriction, with cortical overgrowth adjacent to the growth plate. Subsequent eccentric, bony growth from this beak usually, but not invariably, occurs in a direction away from the joint, forming an excrescence that continues to grow until the growth plate closes and growth ceases at puberty. Malignant degeneration occurs in 1-25% of cases and should be suspected if an exostosis rapidly increases in size, especially in an adult. Spontaneous resolution of osteochondromas has been described. Osteochondromas that continue to grow after puberty should raise the possibility of chondrosarcomatous transformation. Hereditary multiple exostoses Hereditary multiple exostoses (HME) is an autosomal dominant condition associated with short stature, multiple osteochondromas, and asymmetrical growth at the knees and ankles; it may lead to deformities.4 The leg-length inequality is usually about 4 cm, and the risk of malignant degeneration is between 1% and 20%. The osteochondromas are located close to the metaphyses, and they may be sessile or pedunculated. The cortex of the lesion is continuous with the cortex of the bone, with a homogeneous continuation of the medulla.5 Dysplasia epiphysealis hemimelica DEH, or Trevor disease, is characterized by osteochondromas arising in the epiphyses and thus involving the joint. The lesions are usually restricted to 1 side of the body, either left or right. Hence, the name hemimelica is used, to reflect involvement of 1 side of the body. There may be multiple lesions in a single limb. DEH usually occurs in infants or young children. DEH primarily involves 1 side of an epiphysis; the medial side is affected twice as often as the lateral side. On macroscopic inspection, the bony lesion is found to be a pedunculated mass closely connected to the epiphysis with a cartilaginous cap. The histologic appearances are similar to those of an osteochondroma. Multiple epiphyseal dysplasia Multiple epiphyseal dysplasia is another autosomal dominant condition characterized by the presence of irregular epiphyseal ossification, with intracapsular or periarticular chondromas of the knees and ankles. Patients with this condition usually present in late childhood. The spine is usually normal. Osteochondromatosis, dominant carpotarsal Osteochondromatosis, dominant carpotarsal, is another autosomal dominant entity, which Maroteaux and colleagues described in a mother and son. This appeared to be the same condition as that in the family reported by Hensinger and coauthors. The osteochondromas are confined to carpotarsal bones. Maroteaux suggested that osteochondromatosis, dominant carpotarsal, is a condition distinct from DEH. Osteochondromatosis, dominant carpotarsal, is usually sporadic. Pathogenesis Osteochondromas develop due to a beaked failure of constriction, with cortical overgrowth adjacent to the growth plate and subsequent eccentric, bony growth from this beak usually away from the joint. The excrescence that forms then continues to grow until the growth plate closes; growth ceases at puberty. Malignant degeneration occurs in 1-25% of cases and should be suspected if an exostosis rapidly increases in size, especially in an adult. Spontaneous resolution of osteochondromas has been described. Osteochondromas that continue to grow after puberty should raise the possibility of chondrosarcomatous transformation. The pathogenesis of HME is poorly understood, but many theories have been put forward to explain its development. The isolation of islets of cartilaginous tissues from the diaphyseal surface of growing cartilage had been hypothesized to cause abnormal osteogenesis. Further theories postulate that osteochondroma formation is related to a defect in the anchoring of germinal cartilage cells to the physis or to the failure of a thin, cortical sleeve of bone acting as a structural constraint, with this failure allowing a spillover of physeal cells onto the metaphysis. The physical-stress theory postulates that focal accumulations of embryonic connective tissue at sites of tendon attachments are converted to hyaline cartilage. Müller supports a clonal etiology and theorizes that osteochondromas result from a primary defect in periosteal differentiation in which ectopic collections of cartilage cells arise from the proliferative layer of the metaphyseal periosteum.6, 7 Multipotent mesenchymal cells in the region of the perichondral groove of Ranvier have also been implicated in the development of osteochondromas. Langenskiöld believes that proliferative interstitial physeal chondrocytes persist in chondrogenesis as they are transformed into the proliferative layer of the metaphyseal periosteum. Porter and Simpson believe that the osteal portion of the osteochondroma provides only a supportive stroma, an idea that is supported by the fact that ablation of the cartilage cap alone is followed by cessation of growth of the osteochondroma.8 Currently, however, no molecular or immunohistochemical data supports this observation. Genetic basis of disease HME is an autosomal dominant disorder with near-complete penetrance. Genetically heterogeneous, it has been associated with mutations in at least 3 different EXT genes. Changes in EXT1 and EXT2 seem to be the most common in HME. Two of the genes are known to function as tumor suppressor genes.9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 The 3 EXT loci have been mapped: EXT1 is in chromosomal regions 8q23-q24, EXT2 is on 11p11-p12, and EXT3 is on chromosome arm 19p.26, 27, 28, 29, 30, 31 Linkage analysis show that the EXT1 and EXT2 loci appear to be altered in most families, whereas EXT3, which has not been fully isolated and characterized, is probably less frequently involved. Epidemiologic analysis of linkage and mutation data indicate that mutations of EXT1 and EXT2 are likely to be responsible respectively for one half and one third of all cases of multiple hereditary exostoses. Further work indicates that in sporadic exostoses and in the inherited ones, chromosomal deletions are present surrounding the EXT1 and EXT2 loci. Additionally, the EXT-like genes are located at sites of tumor suppressor genes in neoplasia32; EXTL1 has been localized to 1p36, which is often a site of deletion in tumors. EXTL3 may be a breast cancer locus.33, 34, 35 Research has shown loss of heterozygosity at the EXT loci in the cartilaginous cap of osteochondromas and in tissue from chondrosarcomas. Further, clonal karyotypic anomalies have been documented in osteochondromas. These studies indicate that the cartilaginous portion of the osteochondroma has a clonal or neoplastic origin. HME has been associated with other genetic syndromes, such as Langer-Giedion syndrome (LGS), or trichorhinophalangeal syndrome type II (TRP II), and DEFECT 11 syndrome.36 Patients with TRP II have a deletion of the EXT1 gene, and they often have associated mental retardation, cone-shaped epiphyses, and atypical facies. DEFECT 11 syndrome involves osteochondromas, enlarged parietal foramina, craniofacial dysostosis, and mental retardation. Patients with this syndrome have deletions of the entire EXT2 gene in chromosomal regions 11p11-p12. FrequencyUnited StatesSolitary osteochondromas are the most common skeletal tumors in childhood, occurring in approximately 1 in 200 children. However, the true prevalence of solitary osteochondromas is not known, because many asymptomatic lesions are never diagnosed. A study from Washington State revealed that about 1 person in 50,000 is likely to have hereditary multiple exostoses (HME). In the families studied, 90% had a family history of HME. InternationalThere are no data to suggest that the international frequency of osteochondromas internationally is different from that in the United States. Mortality/MorbidityMorbidity and mortality are primarily related to the complications associated with osteochondromas (see Complications of Osteochondromas in Clinical Details). Race
Sex
Age
Clinical DetailsPhysical findingsSolitary osteochondromas Osteochondromas can occur at any time between birth and the cessation of growth. Most solitary osteochondromas are discovered in children and adolescents as painless, slow-growing masses. However, depending on the location of the osteochondroma, significant symptoms may occur as a result of complications, such as fracture, bony deformity, mechanical joint problems, and vascular or neurologic compromise. Pain, swelling, and an enlarging soft-tissue mass may herald malignant transformation.37 The estimates of the risk of malignant transformation (usually chondrosarcomas) vary, with a range of 1-25%. Hereditary multiple exostoses Hereditary multiple exostoses (HME) is an autosomal dominant condition associated with short stature, multiple osteochondromas, and asymmetric growth at the knees and ankles, which may lead to deformities. Leg-length inequality is usually about 4 cm, and the risk of malignant degeneration is about 1-20%. Patients with HME can have anywhere from 2 osteochondromas to hundreds of them. Most osteochondromas related to HME are located at the periphery of the most rapidly growing ends of long bones, but they also commonly involve the medial borders of the scapulae, ribs, and iliac crests. Osteochondromas affect the tarsus and carpus less frequently. Skull involvement has been reported only once, and involvement of the facial bones has not been reported. Osteochondromas in HME come to clinical attention during the first decade of life in more than 80% of patients. The most common locations where the bony lumps are discovered are on the tibia and the scapulae. In rare cases, osteochondromas are discovered at birth, but these are usually cases in which a targeted search is made in the context of a positive family history. Several reports have described osteochondromas interfering with normal birth in pregnancy and leading to a higher rate of cesarean deliveries. Osteochondromas tend to grow while the growth plates are open, but growth ceases with skeletal maturity. Rarely, spontaneous resolution of osteochondromas has been reported during childhood and puberty. Recurrence of an exostosis after surgical ablation has been reported, but it is usually attributed to incomplete resection. Most osteochondromas in HME are painless, and the patient's concern may be cosmetic. However, pain may ensue after soft-tissue trauma. Pain is a common presentation with malignant transformation. The formation of a bursal compartment surrounding a large osteochondroma is common. Bursae are particularly common at sites of friction around scapulae and the distal femur. These bursae may become inflamed and painful. Impaired body growth, symmetrical and asymmetrical, is common in HME. The result is short stature, limb-length discrepancies, valgus deformities of the knee and ankle, asymmetry of the pectoral and pelvic girdles, bowing of the radius (with ulnar deviation of the wrist), and subluxation of the radial head. Patients with HME frequently have a short stature, usually with a height 0.5-1.0 standard deviation below the mean. About 36.8% of affected men and 44.2% of affected women have been observed to have a height below the fifth percentile. Limbs are usually involved disproportionately, as compared with the spine. Limb-length inequality of 2 cm or greater has been reported, with a prevalence ranging from 10-50%. Shortening can occur in the femur and/or the tibia; the femur is affected approximately twice as commonly as the tibia. Scoliosis, coxa valga (25%), acetabular dysplasia, and shortening of the metatarsals, metacarpals, and phalanges occur less frequently. Tendons, nerves, or blood vessels may be trapped around osteochondromas, leading to symptoms. Spinal cord compression is a rare complication of HME, and several case reports have appeared in the literature. Visceral injuries and/or luminal obstructions have been described with inwardly growing osteochondromas. These conditions include dysphagia, hemothorax, and urinary and intestinal obstruction.38, 39 The severity of forearm involvement in HME has been linked to the overall severity of the disease. Taniguchi categorized patients into 3 groups40: (1) those with a normal distal forearm, (2) those with involvement of the distal radius or ulna without bone shortening, and (3) those with involvement of the distal radius or ulna with bone shortening. He concluded that an increasing forearm involvement was associated greater severity of the disease process overall and that patients with more osteochondromas, particularly those involving the knee, have an increased valgus deformity and shorter stature. Forearm involvement also leads to an earlier diagnosis.41 The hand is involved in 30-79% patients. The metacarpals and phalanges are affected in most patients, who are usually asymptomatic. Osteochondromas may result in shortening of the metacarpals and phalanges, and brachydactyly may also be seen in the absence of osteochondromas. Osteochondromas affect the forearm (40-60%) more frequently than they do the upper arm. Radial bowing may ensue as a result of disproportionate ulnar shortening with relative radial overgrowth. Radial head subluxation or dislocation may be a sequel to the radial overgrowth. Although this deformity superficially resembles Madelung anomaly, the characteristic relative elongation or dorsal subluxation of the distal ulna seen in Madelung deformity is not present. Femoral anteversion and valgus have been reported with osteochondromas located near the lesser trochanter. Proximal femoral osteochondromas can cause impairment of hip flexion. Rare cases of acetabular dysplasia resulting in subluxation of the hip have been reported. Valgus deformity of the knees occurs in as many as 30% of patients. The fibula may be shortened disproportionately as compared with the tibia, contributing to a consistent valgus deformity. Angular limb deformities are commonly associated with osteochondromas, affecting the proximal tibia (70-98%) or fibula (30-97%). Valgus deformity of the ankle is a common complication (45-54%) attributed to multiple factors, including shortening of the fibula relative to the tibia. Obliquity resulting from a valgus deformity of the ankle may cause medial subluxation of the talus. Neurologic and vascular compromise may affect both extremities. Symptoms of peripheral nerve compression occur in 22.6% of patients. A recognized complication of HME in children is peroneal neuropathy associated with an osteochondroma affecting the proximal fibula. A single report describes ulnar neuropathy from compression by an osteochondroma at the elbow. Vascular compromise secondary to osteochondromas has been reported in 11.3% of patients with HME. The popliteal artery is most frequently involved. Vascular compression, arterial thrombosis, aneurysm, pseudoaneurysm formation, and venous thrombosis are common complications and lead to claudication pain, acute ischemia, and signs of phlebitis.42 Malignant degeneration Malignant degeneration of a benign osteochondroma occurs in 1-25% of patients. The likelihood of such transformation is greater with HME than with other conditions. Most transformations are to a chondrosarcoma, but other sarcomata may complicate the disease. Most patients with this complication present with a painful mass. Rarely, nerve compression can be the presenting complaint. The mean age at diagnosis is reported to be 31 years. Malignant transformation is said to occur only rarely in the first or fifth decade of life. The risk of superimposed malignant transformation varies among families, reflecting genetic heterogeneity that predisposes osteochondromas to malignant degeneration. Because of this risk, a case can be made for a careful follow-up of patients with HME . Growth of an osteochondroma in a mature skeleton should suggest malignancy and must be assessed. Additionally, an osteochondroma with a cartilaginous cap greater than 1 cm in an adult should be carefully assessed, because this finding has also been associated with an increased risk of malignancy. Dysplasia epiphysealis hemimelica Dysplasia epiphysealis hemimelica (DEH), or Trevor disease, usually occurs in infants or young children. The clinical manifestations include pain, swelling, and joint deformity localized to 1 side of the body. The lower limbs are more commonly affected than are the upper limbs. The talus, distal femur, proximal tibia, and distal tibia are the sites typically affected. Approximately 70% of patients have multiple-bone involvement in a single limb. Complications of osteochondromasComplications of osteochondromas include fractures, bony deformities, neurologic and vascular injuries, bursa formation, and malignant transformation. Research advances have added to the understanding of the molecular and genetic bases of HME. A large, pedunculated osteochondroma may be exposed to trauma and fracture. Osseous deformity can affect the tubular bones. This complication is generally associated with large osteochondromas and occurs more frequently with HME than with other conditions. Growth disturbance may also occur; again, this is more common with HME. Morbidity may arise as a result of arterial or venous thrombosis. Aneurysms and false aneurysms have been described. Vascular complications occur more commonly in the popliteal artery with osteochondromas affecting the knee. Neurologic complications occur in 8% of patients. Such complications are mostly related to spinal cord compression or compromise of the nerve roots by spinal osteochondromas. Bursa formation can surround the tip of the osteochondroma. This happens more commonly with large osteochondromas than with small ones. These bursae may become inflamed or infected, becoming symptomatic. Severe DEH is associated with muscle wasting, growth disturbance, and joint deformities. Malignant transformation has been estimated to occur in 1-25% of osteochondromas; this appears to be more common in HME than in other conditions. The complicating tumor is usually a chondrosarcoma and is generally of low grade. Appreciable morbidity is related to resection of osteochondromas and to corrective surgery on osteochondroma-related osseous deformity. Resection should be performed only when the skeleton has matured, unless the lesion is symptomatic. Resection performed in an immature skeleton may result in a severe growth deformity if damage to the epiphyseal plate occurs. Preferred ExaminationPlain radiography remains the examination of choice in the evaluation of osteochondromas, and it may be the only imaging study required. The radiographic appearances of osteochondromas are usually characteristic. Computed tomography (CT) scanning is particularly useful in the assessment of osteochondromas in the pelvis, shoulder, or spine. With spiral and multisection CT scanning, excellent reconstructions can be formatted in various planes without exposing the patient to a further radiation burden. Ultrasonography can be used in the evaluation of the cartilaginous cap and of complications associated with osteochondromas, such as arterial or venous thrombosis, aneurysm and pseudoaneurysm formation, and bursitis. Magnetic resonance imaging (MRI) is useful for assessing continuity of the parent bone with the cortical and medullary bone in an osteochondroma. Cartilage in the cap has high signal intensity on T2-weighted, spin-echo MRI scans. This characteristic allows measurement of the cap, which is an important consideration in malignant transformation. MRI also provides information about inflammation in reactive bursa formation, impingement syndromes, and arterial and venous compromise. This study is the method of choice for evaluating compression of the spinal cord, nerve roots, and peripheral nerves. Arteriography remains the criterion standard for depicting vascular occlusion, as well as aneurysm and pseudoaneurysm formation. Angiography is not universally employed in the diagnosis of sarcomatous transformation, but it is highly useful for tracing the malignant character and true extent of the lesion. Limitations of TechniquesNone of the imaging techniques described are reliable in differentiating a benign osteochondroma from a sarcomatous transformation. Although plain radiographs are an excellent means of depicting osseous pathology, they do not provide reliable information about adjacent soft-tissue compromise (such as tendinous, vascular, or neurologic involvement) or about bursa inflammation. Plain radiographs may also not be sufficient to provide images of osteochondromas involving complex bones, such as the spinal column. Ultrasonography can provide information on the cartilage cap but not on the underlying bone in an osteochondroma. Also, ultrasonography remains operator dependent. With CT scanning, radiation burden in the young may be a disadvantage, particularly when several examinations may be required in the workup of hereditary multiple exostoses (HME) or sarcomatous transformation. Angiography is invasive, and because of the iodinated contrast material used in this procedure, there is a risk of anaphylaxis and renal toxicity. MRI is expensive, has limited availability, and cannot be performed in the claustrophobic patient and in patients with certain types of heart valves, surgical clips, or other ferromagnetic foreign bodies. Radionuclide scanning has high sensitivity but low specificity. It is also expensive and has limited availability. Radionuclides are not reliable in differentiating between a benign osteochondroma and a chondrosarcoma. Experience with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) is limited.43 In addition, the procedure is expensive and has limited availability. DIFFERENTIALSSection 3 of 12
Other Problems to Be ConsideredMetaphyseal spurs
Exostoses/osteochondromas
Spurs seen as normal anatomic variants
RADIOGRAPHSection 4 of 12
FindingsThe plain radiographic appearances of an osteochondroma are those of a pedunculated or sessile bony excrescence with well-defined margins. In adults, the cartilage cap often contains flecks of calcification. Osteochondromas arising from the surface of a bone contain spongiosa and cortex that appear continuous with the parent bone; this is particularly obvious in long bones. The most common site of origin for an osteochondroma is the metaphysis at bony sites of tendon and ligamentous attachments. Osteochondromas usually point away from its point of attachment toward the diaphysis. The metaphysis of the affected tubular bone may be widened. The long tubular bones are affected most frequently. In long bones, osteochondromas are typically located at the metaphysis. The sites of predilection include the distal femoral metaphysis, the proximal humeral metaphysis, the tibia, and the fibula. The small bones of the hands and feet are affected in around 10% of patients. The innominate bone is involved in 5% of patients. The spine is less frequently involved (2%), but it can lead to cord compression. The scapula is affected in 1% of patients. Osteochondromas arise less frequently from flat bones than from long bones. The spine, pelvis, ribs, and scapulae are the bones most commonly affected. A subungual osteochondroma is rare, but it is particularly prone to a painful bursa (not visible on plain radiographs) and fracture. An osteochondroma of the sesamoid bone of the hallux has been described, but it is extremely rare. Osteochondromas arising from the pelvis are commonly large and are typically associated with a soft-tissue mass that may grow outward or inward, displacing adjacent structures. Radiologically differentiating a benign tumor from a sarcoma is problematic in the pelvis, particularly when the mass has a soft-tissue component. Planar tomography is still a cost-effective and useful procedure in depicting bone detail in complex skeletal areas. Typically, osteochondromas arising from the ribs are located at the costochondral junction, where they can cause a pneumothorax/hemothorax (rare) that may be evident on a plain radiograph.38, 39 When the small bones of the hands and feet are affected, the appearances of the osteochondromas are identical to those found in the long bones. Serial radiographs showing an enlarging osteochondroma with irregularity of its margin and accompanied by a soft-tissue mass should alert the clinician to sarcomatous transformation, particularly when the finding is accompanied by pain. Bone erosions and irregularity or scattered calcification are further clues that malignant transformation may have occurred. Hereditary multiple exostoses (HME) is characterized by multiple osteochondromas that typically involve the proximal part of the humerus and the distal and proximal portions of the femur, tibia, and fibula. Often, there are associated defects of bone modeling and bony deformities—in particular, bilateral coxa valga and widening of the proximal femoral metaphysis. Bilateral, progressive changes in the forearm have been linked to the severity of the underlying disease. Radial bowing may ensue as a result of disproportionate ulnar shortening with relative radial overgrowth. Radial-head subluxation or dislocation may be a sequel to the radial overgrowth, with a superficial resemblance to a Madelung anomaly, but the characteristic relative elongation or dorsal subluxation of the distal ulna seen in Madelung deformity is not present. Plain radiographic findings of dysplasia epiphysealis hemimelica (DEH) include irregular ossification occurring to 1 side of the ossifying epiphysis or a carpal or tarsal bone. The adjacent metaphysis may be widened. With progression of disease, a lobulated bony mass protrudes from the epiphysis or the carpal or tarsal bone. Severe disease is associated with muscle wasting, growth disturbance, and joint deformities. Degree of ConfidencePlain radiography remains the primary modality for imaging osseous pathology. Experience with bone radiography extends over 100 years. The normal variants are well defined. The diagnosis of osteochondromas is straightforward, particularly at the common sites in long bones. Plain radiographs are particularly good for diagnosing complications related to osteochondromas, such as fractures, osseous deformity, and growth disturbances. Plain radiography is inexpensive, effective, and universally available. With the advent of digital radiography, the radiation dose can be better regulated, and digital images have the advantage of better sensitivity, better image manipulation, and better storage. In addition, the images can be transmitted to distant facilities. Osteochondromas arising from complex areas can be clarified by means of planar tomography. False Positives/NegativesThe list of differential diagnoses for osteochondromas is extensive. Osteomas, osteophytes, enthesophytes, heterotopic ossification, and parosteal osteosarcomas can all mimic osteochondromas. The list of systemic disorders and developmental anomalies that are accompanied by osteochondromas or osteochondroma-like abnormalities is long, and these may cause confusion with solitary osteochondromas or with hereditary multiple exostoses (HME). False-negative or false-positive diagnosis may occur with malignant transformation. However, problems may arise with resected tumors that appear radiologically aggressive, even with the histologic confirmation of malignancy. CT SCANSection 5 of 12
FindingsCT scanning can provide excellent bone detail of osteochondromas developing in the spine, shoulder, or pelvis, despite the complex nature of these bones. CT myelography is useful in evaluating the size and extent of spinal osteochondromas in patients presenting with compressive myelopathy. Degree of ConfidenceCT scanning is an excellent modality for depicting bone detail in skeletal lesions and calcification within surrounding cartilage and soft tissue. One major disadvantage of CT scanning, however, is that it provides no information about the metabolic activity of bone lesions. False Positives/NegativesAn increase in the size of osteochondromas due to bursitis is a known complication, and a false-positive diagnosis of malignant transformation has been reported with CT scanning and MRI. Therefore, ultrasonographic evaluation is always recommended for the evaluation of enlarging solitary osteochondromas. MRISection 6 of 12
FindingsMRI is useful for assessing the continuity of the parent bone with the cortical and medullary bone in an osteochondroma. Cartilage in the cap has high signal intensity on T2-weighted, spin-echo MRI scans. This characteristic allows measurement of the cap, which is an important consideration in malignant transformation. MRI also provides information about inflammation in reactive bursa formation, impingement syndromes, and arterial and venous compromise. This study is the method of choice for evaluating compression of the spinal cord, nerve roots, and peripheral nerves. De Beuckleer and associates showed that MRI improves accuracy in the diagnosis of low-grade chondrosarcomas.46 MRI scans contribute only to the diagnostic workup of cases in which malignant change is suspected, because osteochondromas have a characteristic appearance on plain radiographs. With chondrosarcomas, the chondroid origin of tumors may be identified with the lobular high signal intensity. Short-tau inversion recovery (STIR) images show peritumoral, soft-tissue edema in 83% of chondrosarcomas. Muscle impingement should be considered in the differential diagnosis of pain in association with osteochondromatosis. On T2-weighted MRI scans, muscle impingement is depicted as increased signal intensity within the muscle. Degree of ConfidenceMRI is useful because it allows the depiction of the continuity of the parent bone with the cortical and medullary bone in an osteochondroma. This is an important prerequisite in differentiating osteochondromas from other surface bone lesions. MRI allows the distinction of muscle impingement, which may be radiographically occult and can be clinically confused with other complications, such as a fracture, bursitis, or malignant degeneration. MRI also improves accuracy in diagnosing low-grade chondrosarcomas. MRI contributes only in cases in which a malignant transformation is suspected. False Positives/NegativesCT scanning and MRI have variable success in differentiating benign osteochondromas from malignant osteochondromas, and false-positive and false-negative studies may result. A false-positive diagnosis can occur with bursal inflammation. ULTRASOUNDSection 7 of 12
FindingsUltrasonography can be applied to analyze the cartilaginous cap of an osteochondroma. The cap appears as a hypoechoic layer covering a hyperechoic underlying bone. Malghem and associates compared ultrasonographic measurements of cap thickness with measurement performed on pathologic specimens in 22 resected exostoses and 2 exostotic chondrosarcomas.47 The ultrasonographic measurements proved accurate, with a mean measurement error of less than 2 mm for cartilaginous caps thinner than 2 cm. Ultrasonography is also valuable in the diagnosis of bursitis and other complications associated with osteochondromas, such as arterial or venous thrombosis, as well as aneurysm and pseudoaneurysm formation. Degree of ConfidenceThe detection rate and measurement accuracy of ultrasonography in the search for and evaluation of cartilaginous caps are comparable to those of MRI and are higher than those of CT. The high sensitivity and specificity of ultrasonography in peripheral vascular pathology is well established. False Positives/NegativesUltrasonography remains operator dependent and can be labor intensive. Ultrasonograms cannot depict the cartilage cap when it is inwardly orientated; however, this is relatively uncommon. False-positive and false-negative results can occur, particularly in cases of deep vein thrombosis in the lower calf. NUCLEAR MEDICINESection 8 of 12
FindingsScintigraphy with bone-seeking isotopes is an effective method of imaging osteochondromas that are metabolically active. Thallium-201 (201Tl) scintigraphy is useful in differentiating malignant transformation from benign osteochondroma in hereditary multiple exostoses (HME). Aoki and associates showed that fluorodeoxyglucose positron emission tomography (FDG-PET) could be an objective and quantitative adjunct in the differential diagnosis and grading of chondrosarcomas.43 Degree of ConfidenceA normal isotopic bone scan virtually excludes the diagnosis of malignant transformation of an osteochondroma. False Positives/NegativesA positive isotopic bone scan does not allow differentiation of the endochondral ossification occurring in a benign osteochondroma from the hyperemia and osteoblastic reaction occurring in a chondrosarcoma. Negative findings of 201Tl scintigraphy may not exclude the possibility of chondrosarcomas, and the utility of this method may be limited. In their article about the role of radionuclide scintigraphy, Hendel and associates concluded that single, standing, planar bone scintigraphy has no value in distinguishing benign osteochondromas from malignant chondrosarcomas.48 ANGIOGRAPHYSection 9 of 12
FindingsVascular complications can occur as a result of osteochondromas, particularly when a bone lesion occurs around the knee. In this situation, arteriography is considered essential in planning surgical treatment. Effective diagnostic imaging is a key to the early operative removal of sarcomas. Angiography has also been used to assess malignant transformation; angiograms may depict neovascularity and the true extent of disease. Degree of ConfidenceAngiography remains the criterion standard in depicting vascular pathology and is an essential part of vascular intervention. False Positives/NegativesFalse-negative angiograms are possible in true aneurysms and in false ones, because a laminated thrombus may lie along the wall and partially fill the aneurysm. In such cases, an ultrasonogram may prove invaluable. INTERVENTIONSection 10 of 12
Solitary osteochondromas can grow large enough to require surgery. Osteochondromas can be chipped with an osteotome. The procedure should be performed only when the skeleton has matured, unless the lesion is symptomatic. If resection is performed in an immature skeleton, care should be taken to avoid damaging the epiphyseal plate, because severe growth deformity may result. Surgical treatment for limb-length discrepancy with appropriately timed epiphysiodesis has been satisfactorily performed in growing patients. Corrective osteotomy is an established procedure to treat valgus deformity at the knee. However, the procedure poses an appreciable risk to the neurovascular structures due to their close anatomic proximity. Supramalleolar osteotomy of the tibia has also been effectively used in the treatment of severe valgus ankle deformity. Growth of osteochondromas may cause tibiofibular diastasis, which can be treated with excision. In advanced cases, excision of the osteochondroma alone may improve symptoms, but it may not correct the ankle deformity. Valgus deformity at the ankle of 15° or more associated with limited shortening of the fibula can be corrected with early medial hemiepiphyseal stapling of the tibia in conjunction with excision of the osteochondroma. When the distal fibular epiphysis is proximal to the distal tibial epiphysis, fibular lengthening has been successfully used to treat severe valgus deformity at the ankle. If symptomatic, most deformities of the forearm associated with hereditary multiple exostoses (HME) are amenable to surgery. Increases in the radial articular angle, progressive ulnar shortening, excessive carpal slippage, loss of pronation, and increased radial bowing with subluxation or dislocation of the radial head are some of the deformities that have been successfully treated with surgery. Resection of the osteochondromas alone may decrease or halt the progression of the osseous deformity, but it does not always provide full correction. Ulnar translocation of the carpals on the distal radius can be corrected with ulnar lengthening, but this does not prevent a persistent, relative ulnar shortening. Radial head subluxation or dislocation may be a sequel to the radial overgrowth, and surgery may be considered to prevent this from occurring. Surgical relocation of the radial head, however, is not consistently successful. Urgent surgery may be required in cases of vascular ischemia in the setting of HME or a solitary osteochondroma.42 Most chondrosarcomas developing in the setting of an osteochondroma are low grade and can be treated with wide excision. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
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