dr james c wittig, orthopedic oncologist, new york, new jersey
Patient Education
Osteochondroma

General Information

  • Osteochondroma is an outgrowth of medullary and cortical bone
  • A portion of the cartilaginous growth plate grows outward instead of longitudinally and forms the osteochondroma/exostosis (like a branch on a tree)
  • It consists of bone covered with cartilaginous cap (exostosis)
  • May be secondary to a growth plate injury (Node of Ranvier injured)
  • Osteochondromas are benign, non-neoplastic conditions
  • Hamartomatous anomaly
  • It can occur as a solitary lesion or as multiple exostoses associated with a hereditary condition known as Multiple Hereditary Exostoses (MHE)
  • Radiation exposure can also be a cause of multiple osteochondromas
  • Solitary Osteochondromas are the most common benign bone tumors and constitute 35% of all benign bone tumors and 10% of all bone tumors overall

There are 2 forms

  • Pedunculated (with a stalk)
  • Sessile (flat without a stalk)
  • Osteochondromas likely arise from displaced cartilage through periosteal defect and grow at right angles to normal growth plate
  • Lesions have self-limited growth that ceases after skeletal maturity
  • Due to endochondral ossification, cartilage cap diminishes in thickness as age increases

Osteochondroma -(most common benign neoplasm of bone that leads to biopsy)

Types:

  • Solitary Osetocartilaginous Exostosis
  • Hereditary Multiple Exostoses (HME)

Radiographic Subtypes:

  • Pedunculated
  • Sessile
Multiple Heredity Exostoses (MHE)

Clinical Data:

  • Male predominance (3:1)
  • Autosomal Dominant inheritance
  • There is variability in size and number of ostechondromas (variable penetrance)
  • Any portion of the skeleton preformed in cartilage may be involved
  • Evident during childhood
  • MHE may be bilaterally symmetric
  • One side may predominate
  • There is a higher incidence of malignant transformation (10-20%) of osteochondromas that
  • develop in MHE. Most commonly a secondary low grade chondrosarcoma develops.

Clinical Presentation

Signs/Symptoms:

  • Hard swelling for many years
  • Symptoms dependent on location/size
  • May cause mechanical symptoms from compression of adjacent structures such as tendons,
  • nerve or blood vessels
  • An overlying bursa may form and result in a bursitis
  • Rare vascular injuries and arterial aneurysms from adjacent osteochondromas
  • Malignant Transformation: Solitary osteochondroma <1%
  • Prevalence:
  • Male>Female 1.8:1

Age:

  • Usually presents clinically by the third decade of life

Sites:

  • Appendicular skeleton: Femur (30%) Tibia (20%) Humerus (2-%) Hand and Foot (10%)
  • Pelvis (5%) Scapula (4%)
  • Surface of metaphyseal portions of long tubular bones
  • Knee area 35% of cases

Radiographic Presentation

Plain X-rays:

  • Projects from bone with narrow (pedunculated) to broad (sessile) stalk
  • Corticomedullary continuity: Medullary bone continuous with that of osteochondroma and cortex blends with that of osteochondroma
  • Calcification in cartilaginous cap ("Ring and Arc" and stippled calcifications)
  • Lobular growth pattern
  • Long bones: arise from metaphysis, grows away from epiphysis toward diaphysis,
  • May be associated with failure of tubulation in Multiple Hereditary Exostosis
  • Flat bones: tend to be larger and sessile, variable appearance
  • Cartilage cap thickness is visualized best on MRI, not XR
  • Bursa may exist external to cartilage cap (seen on MRI)
Roll over the images for more information
Plain X-Ray:  Osteochondroma of Proximal Tibia Proximal Fibula Osteochondroma: Cortical-Medullary Continuity; Ring and Arc Calcifications
MRI of Proximal Fibula Osteochondroma Demonstrates Continuity of Medullary Canal of Fibula with Osteochondroma MRI Demonstrates Stalk and Continuity with Underlying Fibula; Thin Cartilaginous Cap
Intraoperative Photograph: Lobular Growth Specimen
Specimen Plain Xray/MRI: Distal Femur Sessile Osteochondroma
Plain Xray/MRI: Distal Femur Sessile Osteochondroma - (arrow) The Cartilage Cap Xay/MRI: Distal Femur Osteochondroma
Xay/MRI: Distal Femur Osteochondroma Gross Specimen Distal Femur Osteochondroma
Osteochondroma of Proximal Femur (Even though this was a large tumor, the cartilage cap was very thin) X-ray: Left Proximal Femur Osteochondroma
MRI: Left proximal Femur Osteochondroma Cortical Medullary Continuity and Thin Cartilage Cap Area between arrows: cartilage cap (approximately 1 cm thickness)
CT Scan: Left Proximal Femur Osteochondroma ross Specimen: Left Proximal Femur Osteochondroma
ross Specimen: Left Proximal Femur Osteochondroma

Osteochondroma Vs. Secondary Chondrosarcoma

The cartilaginous cap deserves the most attention when differentiating a benign osteochondroma from a secondary chondrosarcoma that arose from a pre-existing osteochondroma

In adults, the cartilaginous cap regresses and becomes thin due to enchondral ossificastion of the majority of the cap.

Malignant transformation is suggested by:

  • Cartilaginous cap thickness greater than 2cm
  • Cortical destruction
  • Backgrowth of the cartilaginous cap into the stalk or medullary canal
  • Lysis of calcifications in cap
Osteochondroma: Cartilage Cap

Radiographs

  • Chondroid Calcification in cap
  • Increasing destruction or change in appearance is worrisome for malignancy

Ultrasound

  • Good for cap and bursae

Bone Scan

  • Increased uptake in the cap

MRI:

  • Best test for evaluating thickness of cap and surrounding bursa
  • Intermediate T1W Images
  • High Intensity T2W Images because of fluid content

CT

  • The cap will appear as soft tissue with calcification
  • Can be difficult to distinguish from muscle

Cap thickness

  • Benign < 1.5cm (0.1 - 3.0cm; Avg. 0.6 - 0.9 cm)
  • Malignant > 1.5 cm (1.5 - 12cm; Ave. 6cm)
Roll over the images for more information
Plain X-ray: Secondary Chondrosarcoma of Proximal Femur MRI: Secondary Chondrosarcoma of Proximal Femur: Thick Cartilage Cap (>2cm)

Pathology

Pathology:

  • Medullary and cortical continuity w/ underlying bone
  • Hyaline Cartilage Cap with lobular growth
  • Cartilage cap involutes after growth

Gross Pathology

  • The osteochondroma is completely covered in periosteum
  • Cut surface shows hyaline composition of cartilage cap

Cap

  • Younger patients thicker cap because of growth hormone
  • Smooth or knobby
  • 2 mm to 1 cm thick

Beneath the cap, calcified cartilage which appear as white deposits are present

Roll over the images for more information
Intraoperative Photograph: Lobular Growth Specimen
Specimen Radiograph:  Osteochondroma Specimen Radiograph:  Osteochondroma

Microscopic Pathology

Roll over the images for more information
Hyaline cartilage cap overlying medullary bone Microscopic Pathology:  Osteochondroma
Cells in Lacunae; Ground Glass Hyaline Cartilage Matrix, Zone of Hypertrophy, Zone of Provisional Calcification; Enchondral Ossification

Treatment

Simple excision:

  • Cosmetic reasons
  • Impingement on tendons, nerves or blood vessels
  • Pain and limitation of motion
  • For multiple exostoses, corrective surgery may be necessary due to secondary deformities

Prognosis

  • Recurrence after excision is rare
  • Rarely, osteochondromas may give rise to malignant chondrosarcoma
    • Solitary osteochondromas 1%-2%
    • Multiple osteochondromas 5%-25%
  • Most common sites to undergo malignant change
    • Scapula, pelvis, ribs, proximal femur
Multiple Heredity Exostoses (MHE)

Clinical Data:

  • Male predominance (3:1)
  • AD inheritance
  • Variability in size and number
  • Any portion of the skeleton preformed in cartilage may be involved
  • Present in childhood
  • May be bilaterally symmetric
  • One side may predominate
  • Increased incidence of malignant transformation (10-20%)
  • Radiographically characterized by multiple osteochondromas and undertubulation of bones
  • (Erlenmeyer Flask Deformity)
Roll over the images for more information
X-ray: Multiple Hereditary Exostoses of Proximal Femur X-ray: Multiple Hereditary Osteochondromas of Distal Femur and Proximal Tibia/Fibula
X-ray: Multiple Hereditary Osteochondromas of Distal Femur and Proximal Tibia/Fibula X-Ray: Multiple Hereditary Osteochondromas of Distal Fibula
X-Ray: Multiple Hereditary Osteochondromas of Scapula/Proximal Humerus

Subungal Exostosis - Dupuytren Exostosis

  • Osteochondroma Variant
  • Females > Males (2:1)
  • Often painful and associated with trauma and infection
  • Fibrocartilage cap
  • Located away from physis

Dysplasia Episphysealis Hemimelica - Trevor Disease

  • Male predominance (3:1)
  • Very rare < 100 cases
  • Swelling, pain and deformity
  • Usually lower extremity, unilateral
  • 65% multiple done involvement: talus, distal femur, tibia

Dysplasia Episphysealis Hemimelica - Trevor Disease

  • Ankle and knee most common
  • Medial joint 2X lateral
  • Lobular epiphyseal mass
  • Histologically identical to an osteochondroma
  • May produce deformity and secondary osteoarthritis
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