AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

An osteochondroma is a cartilage covered bony excrescence (exostosis) that arises from a surface of a bone. Osteochondromas are the most common bone tumors in children, they 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 are never diagnosed. Hereditary multiple exostoses (HME) 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 in his lecture on the principles of surgery in 1786. In 1814, Boyer published the first description of a family with HME. This was followed by Guy's description of a second family in 1825.

Most osteochondromas, solitary or multiple, arise from tubular bones and are metaphyseal in location. Multiple epiphyseal dysplasia and dysplasia epiphysealis hemimelica (DEH), or Trevor disease, are also autosomal dominant conditions in which the chondromas arise from the epiphysis and cause joint problems.

Patients with HME may have 2 to 100s of osteochondromas. 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. Recent advances have added to the understanding of the molecular and genetic basis of HME.

Pathophysiology

Solitary osteochondromas

Solitary osteochondromas are a relatively frequent finding and regarded as true tumors or growth disturbances. They develop in parts of the skeleton that develop from endochondral ossification and thus are closely linked to physes.

They vary considerably in size; the average lesion arising from tubular bones 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 occurs usually, but not invariably, in a direction away from the joint, forming an excrescence that continues to grow until the growth plate closes and until 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

HME is an autosomal dominant condition associated with short stature, multiple osteochondromas, asymmetric growth at the knees and ankles, which may lead to deformities. The leg-length inequality is usually about 4 cm, and the risk of malignant degeneration is 1-20%.

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.

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 et al described in a mother and son. This appeared to be the same condition as that in the family reported by Hensinger et al. The osteochondromata are confined to carpotarsal bones. Maroteaux et al has 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 forwarded 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 that allows 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. 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 persists in chondrogenesis as they are transformed into the proliferative layer of the metaphyseal periosteum. Recently, clonal karyotypic abnormalities have been documented in osteochondromas. Studies indicate that the cartilaginous portion of the osteochondroma have a clonal or neoplastic origin.

Porter and Simpson believe that the osteal portion of the osteochondroma provides only a supportive stroma, which is supported by the fact that ablation of the cartilage cap alone is followed by cessation of growth of the osteochondroma. Currently, however, no molecular or immunohistochemical data supports this observation.

Genetic basis of disease

HME is an autosomal dominant disorder with near-complete penetrance and is genetically heterogeneous that has been associated with mutations in at least 3 different genes termed 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.

The 3 EXT loci have recently been mapped: EXT1 is in chromosomal regions 8q23-q24, EXT2 is on 11p11-p12, and EXT3 is on chromosome arm 19p. 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 both sporadic and inherited exostoses, chromosomal deletions are present surrounding the EXT1 and EXT2 loci. Additionally, the EXT-like genes are located at sites of tumor suppressor genes in neoplasia; EXTL1 has been localized to 1p36, which is often a site of deletion in tumors. EXTL3 may be a breast cancer locus.

A number of studies have further clarified the role tumor suppression and have shown loss of heterozygosity at the EXT loci in the cartilaginous cap of osteochondromas and tissue from chondrosarcomas. Further, clonal karyotypic anomalies have also 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. 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.

Frequency

United States

A solitary osteochondroma is the most common skeletal tumor in childhood and occurs in approximately 1 in 200 children. However, the true prevalence of solitary osteochondromas is not known because many asymptomatic lesions are never diagnosed.

A recent study from the state of Washington revealed that about 1 person in 50,000 is likely to have the condition. In the families studied, 90% had a family history of HME.

International

There is no data to suggest that the international frequency of osteochondromas internationally is different from that in the United States.

Mortality/Morbidity

Morbidity and mortality are primarily related to the complications associated with osteochondromas (see Complications of osteochondromas in Clinical Details).

Race

• HME is more frequently found in whites than in persons of other races and affects 0.9-2 individuals per 100,000 population.
• A higher incidence has been described in isolated communities, such as the Chamorros of Guam or the Ojibway Indian community of Pauingassi in Manitoba, Canada. These populations have a prevalence of 100 or 1310 cases per 100,000 population, respectively.

Sex

• Solitary osteochondromas are more prevalent in males than in females.
• Although HME (diaphyseal achalasia) was previously thought to have a male predominance, it now appears to affect both sexes equally.
• DEH occurs more commonly in males than in females.

Age

• Solitary osteochondromas typically occurs in the first to third decades.
• HME usually appears in childhood (2-10 y), and most are discovered by age 4 years.

Clinical Details

Physical findings

Solitary osteochondromas

Osteochondromas can occur at any time from birth to 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. The estimates of the risk of malignant transformation (usually chondrosarcomas) vary, with a range of 1-25%.

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 have multiple osteochondromas varying from 2 to 100s. 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 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, both 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, most with heights 0.5-1.0 standard deviations below the mean. About 36.8% of affected men and 44.2% of affected women have been observed to have heights 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 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 both urinary and intestinal obstruction.

The severity of forearm involvement in HME has been linked to the overall severity of the disease. Taniguchi categorized patients into 3 groups: (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 of diagnosis.

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 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 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 to 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.

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 decade and fifth decades of life.

The risk of superimposed malignant transformation varies among families, reflecting genetic heterogeneity that predisposes them to malignant degeneration. A case can be made for a careful follow-up of patients with HME because of this risk.

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

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 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 osteochondromas

Complications of osteochondromas include fractures, bony deformities, neurologic and vascular injuries, bursa formation, and malignant transformation. Recent advances have added to the understanding of the molecular and genetic basis 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. Both aneurysms and false aneurysms have been described. Vascular complications occur more commonly in the popliteal artery with osteochondromas affecting the knee.

Neurologic 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 and become 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 and appears more common in HME than in other conditions. The complicating tumor is usually a chondrosarcoma and generally of low grade.

Appreciable morbidity is related to resection of osteochondromas and corrective surgery on osseous deformity associated with osteochondromas. 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 Examination

Plain 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.

CT is particularly useful in the assessment of osteochondromas in the pelvis, shoulder, or spine. With spiral and multisection CT, 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.

MRI is useful for assessing continuity of the cortical and medullary bone in an osteochondroma with the parent bone. Cartilage in the cap has high signal intensity on T2-weighted spin-echo MRI. 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, 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 and aneurysm and pseudoaneurysm formation. Angiography is not universally used in the diagnosis of sarcomatous transformation, but it is highly useful for tracing the malignant character and true extent of the lesion.

Limitations of Techniques

None of the imaging techniques described are reliable in differentiating a benign osteochondroma from 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, neurologic involvement or information about bursa inflammation. Plain radiographs may also be not sufficient in providing images of osteochondromas involving complex bones such as the spinal column.

Ultrasonography can provide information on the cartilage cap but not the underlying bone in an osteochondroma. Ultrasonography remains operator dependent.

With CT, radiation burden in the young, particularly when several examinations may be required in the workup of HME or sarcomatous transformation.

Angiography is invasive and poses risks of anaphylaxis and renal toxicity from the iodinated contrast material.

MRI is expensive with 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 a 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 (FDG) positron emission tomography (PET) is limited. The procedure is expensive and has limited availability.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Other Problems to be Considered

Metaphyseal spurs

• Hyperparathyroidism
• Short-rib polydactyly syndrome type II
• Short-rib polydactyly syndrome type III
• Spur-limbed dwarfism
• Adenosine deaminase deficiency - Associated with irregularity of metaphyseal end of long bones, splayed metaphyses, metaphyseal spurs perpendicular to long axis of bones, short and wide ribs, cup-shaped at costochondral junctions, bone-within-a-bone appearance of vertebrae and osteoporosis, among other skeletal abnormalities
• Copper deficiency - Associated with osteoporosis, irregularity and cupping of the provisional zone of calcification, sickle-shaped spur formation continuous with the provisional zone of calcification, multiple fractures, subperiosteal hemorrhage, subperiosteal elation and calcification, and delayed skeletal growth
• Iso-Kikuchi syndrome - Associated with asymmetric upper limb anomalies, hypoplastic thumb, triphalangeal thumb, long and slender metacarpals, hypoplastic carpal bones, fusion of the radius and ulna, and subungual spur
• Fibrodysplasia ossificans progressiva - Associated with microdactyly, small vertebrae, and ossification of ligamentous insertions producing pseudo-exostoses, and spiking and flaring of metaphyses
• Hypophosphatasia - Associated with a variety of prenatal and postnatal skeletal abnormalities (Spurs [eg, Bowdler spur] in the mid portion of long bones are a known association.)
• Menkes disease - Associated with bilateral metaphyseal spurring of long bones in infancy, flaring of the ribs, osteoporosis, fractures and diaphyseal periosteal reaction of the long bones, thickening of the scapulae and clavicles, and CNS abnormalities

Exostoses/osteochondromas

• Fetal alcohol syndrome - Multisystemic disorder associated with bilateral tibial
• Turner syndrome - Associated with exostosis of tibia
• Tuberous sclerosis - Described association with both exostoses and exostosis of long bones
• Radiation-induced osteochondromas
• Traumatic bony injury/fractures
• Acrodysostosis - Associated with brachycephaly, hypoplastic facial bones, thick calvarium, peripheral dysostosis, epiphyseal and vertebral stippling and exostoses of proximal tibia
• Osteochondromatosis, carpotarsal dominant - Associated with osteochondromata of carpal and tarsal bones, cuboid, calcaneum, metacarpals, metatarsals, fibulae and tibiae
• Chondroectodermal dysplasia - Associated with short ribs, bowed femur, trident iliac wings, bowed humerus and exostosis of the medial aspect of the distal metaphysis of the humerus in the newborn
• TRP II (LGS) - Associated with multiple exostoses and redundant skin folds (The presence of exostoses differentiate TRP II from trichorhinophalangeal syndrome type I [TRP I].)
• Bizarre parosteal osteochondromatous proliferation (BPOP) - Also known as the Nora lesion, benign process that can be confused with osteochondromas and occasionally misinterpreted as a malignant process (Radiologically, calcific masses are attached to the underlying cortex without interruption of the latter. The original report described lesions confined to the small bones of the hands and feet, but subsequent reports have included the skull, maxilla, and long bones [eg, tibia, femur]).

Spurs seen as normal anatomic variants

• Cervical spine - Development of spurlike process from posterior neural arch
• Olecranon - Spurs usually seen in the young
• Radius - Spur located in distal radius in adolescents
• Metacarpals/metatarsals - Spur distal end of the bones associated with accessory ossification centers
• Phalanges - Spurs that affect the proximal phalanges in the fingers and medial aspects of terminal phalanges in the toes
• Ribs - Spurs that may affect any rib
• Acetabulum - Spurlike superior lip
• Sacroiliac joints - Spur inferior aspect of the joint
• Obturator foramen - Spurs in the obturator foramen arising from the pubis, usually seen in the elderly
• Ileum - Spurring of muscle attachments, usually seen in the elderly
• Patella - Spurs on the medial aspect
• Fibula - Tug lesion at both ends of the soleus muscle producing a fibular spur and the soleal line
• Calcaneum - Transient developmental spur in infants
• Navicular bone - Spurlike process projecting posteriorly
• Humerus - Upper metaphyseal spurs seen in young adults and adolescents (A supracondylar process is a vestigial structure associated with symptoms and occurs in about 1% of the European population. The axis of the process is directed distally.)
• Tibia - Spur tibial plateau in the absence of osteoarthritis that possibly represents attachment of the anterior cruciate ligament (A small spur may be present on the medial tibial metaphyses; it probably represents a tug lesion produced by the tibial collateral ligament.)

RADIOGRAPH

Section 4 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

The 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 arise from the surface of the bones 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 towards 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 distal femoral metaphysis, proximal humeral metaphysis, tibia, and 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 particularly prone to painful bursa (not visible on plain radiographs) and fracture. An osteochondroma of the sesamoid bone of the hallux has been described, but is extremely rare. Osteochondromas arising from the pelvis are commonly large 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 it can cause a pneumothorax/hemothorax (rare) that may be evident on a plain radiograph. When the small bones of the hand 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.

HME is characterized by multiple osteochondromas typically involving 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 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 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 Confidence

Plain radiography remains the primary modality for imaging osseous pathology. Experience with bone radiography extends over 100 hundred years. The normal variants are well defined. The diagnosis 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, better storage and link-up to distant facilities.

Osteochondromas arising from complex areas can be clarified by means of planar tomography.

False Positives/Negatives

The list of differential diagnoses for osteochondromas is extensive. Osteoma, osteophyte, enthesophyte, heterotopic ossification such as (eg, myositis ossificans), and parosteal osteosarcoma 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 HME.

False-negative and 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 SCAN

Section 5 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

CT 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 Confidence

CT is an excellent modality for depicting bone detail in skeletal lesions and calcification within surrounding cartilage and soft tissue. One major disadvantage of CT is that it provides no information about the metabolic activity of bone lesions.

False Positives/Negatives

The increasing size of osteochondromas due to bursitis is a known complication, and a false-positive diagnosis of malignant transformation has been reported with both CT and MRI. Therefore, ultrasonographic evaluation is always recommended for the evaluation of enlarging solitary osteochondromas.

MRI

Section 6 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

MRI is useful for assessing continuity of the cortical and medullary bone in an osteochondroma with the parent bone. Cartilage in the cap has high signal intensity on T2-weighted spin-echo MRI. 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, 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 have shown that MRI improves the accuracy of diagnosing low-grade chondrosarcomas. MRIs 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 MRIs, muscle impingement is depicted as increased signal intensity within the muscle.

Degree of Confidence

MRI is useful in that it allows the depiction of the continuity of the cortical and medullary bone in an osteochondroma with the parent bone. 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 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/Negatives

Both CT 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.

ULTRASOUND

Section 7 of 12  

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• MRI
• Ultrasound
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• Intervention
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• References

Findings

Ultrasonography can be applied to analyze the cartilaginous cap. The cartilage 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. The sonographic measurements proved accurate, with a mean measurement error of less than 2 mm for cartilage 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, aneurysm, and pseudoaneurysm formation.

Degree of Confidence

The detection rate and measurement accuracy of cartilage cap with sonography is comparable to those of MRI and higher than those of CT. The high sensitivity and specificity of ultrasonography in peripheral vascular pathology is well established.

False Positives/Negatives

Ultrasonography remains operator dependent and can be labor intensive. Sonograms 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 MEDICINE

Section 8 of 12  

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• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Scintigraphy with bone-seeking isotopes is an effective method of imaging osteochondromas that are metabolically active. Thallium Tl 201 scintigraphy is useful in differentiating malignant transformation from benign osteochondroma in HME.

Aoki and associates have shown that FDG PET could be an objective and quantitative adjunct in differential diagnosis and grading of chondrosarcomas.

Degree of Confidence

A normal isotopic bone scan virtually excludes the diagnosis of malignant transformation.

False Positives/Negatives

A 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 osteochondroma from malignant chondrosarcomas.

ANGIOGRAPHY

Section 9 of 12  

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• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Vascular 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 Confidence

Angiography remains the criterion standard in depicting vascular pathology and is an essential part of vascular intervention.

False Positives/Negatives

False-negative angiograms are possible both in true as well as false aneurysms because laminated thrombus may lie along the wall and partially fill the aneurysm. In such cases, a sonogram may prove invaluable.

INTERVENTION

Section 10 of 12  

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• Introduction
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• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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. The procedure is not without risk, as there is an appreciable risk to the neurovascular structures because of 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 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 fibula 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 HME are amenable to surgery. Increasing 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 osteochondromata 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 sequel to the radial overgrowth. 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. Most chondrosarcomas developing in the setting of an osteochondroma are low grade and can be treated with wide excision.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Osteochondroma and osteochondromatosis. Plain radiograph of the cervical spine shows a solitary osteochondroma of the posterior elements of C6.
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Media file 2:  Osteochondroma and osteochondromatosis. Radiographs of both hands of 36-year-old man show multiple osteochondromata involving the radii right distal fibula, metacarpals, and phalanges. Note the large osteochondroma involving the terminal phalanx of the right index finger.
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Media file 3:  Osteochondroma and osteochondromatosis. Plain radiograph of the pelvis in a 41-year-old woman shows multiple osteochondromas affecting the left transverse process of L5, iliac blades, superior pubic rami, ischial spines, and femoral necks. Note the modeling deformity of the femoral necks and the narrowing of the pelvic inlet as a result of osteochondromata. Several reports have described osteochondromas interfering with normal vaginal birth in pregnancy and leading to a higher rate of Cesarean deliveries.
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Media file 4:  Osteochondroma and osteochondromatosis. Multiple osteochondromatosis. Plain radiograph of the lower limbs of an 10-year-old boy with a family history of hereditary multiple exostoses shows widening of the lower femoral metaphyses and osteochondroma involving the upper fibulae and tibia.
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Media file 5:  Osteochondroma and osteochondromatosis. Solitary osteochondroma. Radiograph of 24-year-old woman who presented with a hard, palpable mass on the medial aspect of the upper calf. A bulbous pedunculated osteochondroma arising from the medial side of the upper tibial diaphysis and pointing away from the metaphysis is noted. The patient reported no history of hereditary multiple exostoses.
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Media file 6:  Osteochondroma and osteochondromatosis. Multiple osteochondromatosis. Fractures of the lower tibia and fibula as a complication of hereditary multiple exostoses. Note the osteochondromata involving the calcaneum and the upper and lower portions of the tibia and fibula.
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Media file 7:  Osteochondroma and osteochondromatosis. Multiple osteochondromatosis. Radiograph of the pelvis in a 28-year-old woman known to have hereditary multiple exostoses who presented with a painful swelling of the left buttock. Note the multiple osteochondromata and fragmentation of the osteochondroma arising from the left anterior iliac crest (see Image 8).
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Media file 8:  Osteochondroma and osteochondromatosis. Multiple osteochondromatosis. Nonenhanced axial CT scan through the pelvis in the same patient in Image 7. Note the fragmentation of the osteochondroma and the considerable soft tissue mass. Histology of the resected specimen revealed a low-grade chondrosarcoma.
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Media type:  CT

Media file 9:  Osteochondroma and osteochondromatosis. Osteochondroma with malignant degeneration. Plain radiograph of the pelvis in a 68-year-old woman who presented with a painful lump over the left greater trochanter. Note the sclerotic exostosis arising from the left greater trochanter. Left, technetium Tc 99m diphosphonate scintigram shows intense activity in the region of the left greater trochanter. Right, At surgery, the lesion was diagnosed low-grade chondrosarcoma superimposed on an osteochondroma.
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Media type:  Image

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

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