Osteochondroma

By admin On Feb 15, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Osteochondroma

Osteochondroma

Frank J. Frassica MD

Basics

Description

An osteochondroma is a common
developmental abnormality of the peripheral growth plate that results
in a lobulated outgrowth of cartilage and bone from the metaphysis.
- Appears as a cartilage-capped bony projection from the metaphysis of long bones
- Can occur in any bone that develops from enchondral ossification
- Most commonly occurs in:
  - Long bones, usually the proximal or distal femur, proximal tibia, pelvis, or scapula
  - 10–25-year-old persons (stops growing at skeletal maturity)
Growth of the lesions parallels that of the patient.
Classification:
- Solitary osteochondroma (nonheritable)
- Multiple hereditary exostoses (autosomal dominant):
  - Osteochondromatosis
  - Diaphyseal aclasis
Synonym: Osteocartilaginous exostosis

Epidemiology

Incidence

No substantial difference in frequency between males and females

Prevalence

This most common benign bone lesion comprises 40% of all benign bone tumors (1,2).

Risk Factors

Genetics

Multiple hereditary exostoses often is inherited in an autosomal dominant manner.
To date, 3 different genetic mutations have been isolated:
- EXT 1
- EXT 2
- EXT 3

Etiology

The cause of an osteochondroma most likely is a detached portion of the growth plate that grows on the surface of the bone.

Diagnosis

Signs and Symptoms

Symptoms result from pressure on adjacent nerves and muscle and from local irritation.
- Hard, painless, fixed mass
- Associated symptoms of tissue or nerve irritation
The skeletal deformity is secondary to undergrowth of the affected bones, with narrower bones being affected more seriously.
- Therefore, the tibia and radius grow longer than the ulna and fibula.
- This phenomenon produces valgus at the knee, ankle, and elbow in some patients.

Physical Exam

Note any hard, painless, fixed mass in
the metaphyseal region of the fastest growing bones; the region around
the knee is the most common.
Height in most patients falls in the low-normal range.
Group findings occur in 4 major categories:
- Local impingement, which may include peroneal palsy and soreness of the muscles about the knee
- Valgus at knee, ankle, elbow, and wrist (variable)
- Limb-length inequality
- ROM may be limited secondary to the presence of the osteochondroma.
Physical examination and radiography should confirm the diagnosis.

Tests

Lab

Blood tests are not altered by this condition.

Imaging

Radiography:
- Plain films typically depict a compact pedunculated or sessile protuberance of bone.
- The well-defined lesion projects from the metaphysis.
CT scans are helpful in locations that are difficult to image, such as the scapula, pelvis, and proximal femur.
MRI scans can be used when a suspicion of malignancy is present.
- The size of the cartilage cap can be measured (a cap >1 cm is worrisome for malignancy).
- Symptomatic bursae can be detected with MRI.
- MRI can detect soft-tissue masses.

Pathological Findings

Normal hyaline cartilage undergoes normal enchondral ossification, occurring on the end of a stalk or ridge of bone.

Differential Diagnosis

Surface chondrosarcoma
Parosteal osteosarcoma
Periosteal chondroma

Treatment

General Measures

Local measures or analgesics are indicated for minor aches.
Medical treatment:
- The lesion may be left untreated unless it is symptomatic.
- It should be followed clinically, because
  a 1–10% risk of malignant transformation to chondrosarcoma is present
  in persons with multiple hereditary exostoses (1,2).

Activity

Activity is allowed as tolerated.

Special Therapy

Physical Therapy

Not usually necessary

Medication

Tylenol or NSAIDs may be used by the patient with occasional symptoms.

Surgery

Surgical resection of symptomatic lesions is successful with minimal morbidity.
In patients with the multiple hereditary
exostoses form of the disorder, new lesions may form in multiple areas,
and they may grow.
Osteotomies and physeal stapling may be done for angular disturbances.

P.291

Follow-up

Prognosis

The prognosis is good.
The chance of recurrence after excision of a solitary lesion is very small.
The risk of malignant transformation of isolated osteochondromas is even lower.
Patients with multiple hereditary exostoses have a 1–10% risk of malignant transformation (1,2).

Complications

Fracture may occur during the first 3 months after removal of an osteochondroma.
Vascular or neurologic injury during surgery may occur if the osteochondroma is associated closely with these structures.
Occasionally, the stalk may fracture.

Patient Monitoring

Patients should be followed regularly (for 1–2 years)
for angular disturbances, limb-length inequality, or serious problems
from pressure of lesion so they can be treated in a timely fashion
before more complex intervention is needed.

References

1. Dorfman HD, Czerniak B. Benign cartilage lesions. In: Bone Tumors. St. Louis: Mosby, 1998:253–352.

2. McCarthy EF, Frassica FJ. Primary bone tumors. In: Pathology of Bone and Joint Disorders: With Clinical and Radiographic Correlation. Philadelphia: WB Saunders, 1998:195–275.

Miscellaneous

Codes

ICD9-CM

756.4 Osteochondroma

Patient Teaching

Reassure the patient about the benign nature of the lesions.
Teach adults to be alert for growth or new onset of pain in osteochondroma, which may be a sign of a malignant transformation.

FAQ

Q: Is it necessary to remove all osteochondromas?

A: In general, if the patient is asymptomatic, surgical removal is not necessary.

Q: What is the risk of malignant degeneration, and are the resultant cancers treatable?

A:
The risk of malignancy in an isolated osteochondroma is extremely low,
and the prognosis for the resulting low-grade chondrosarcomas is
excellent.

Q: How are patients with multiple hereditary exostoses followed to check for malignant degeneration?

A:
Patients are queried about new masses or pain. Plain radiographs, CTS,
or MRIs can be used to monitor exostosis in the axial skeleton or large
lesions in the extremities.