Introduction

Osteochondromas are benign tumours of bone and cartilage. They frequently grow outwards from bone near the growth plate (metaphysis) and can be palpated. They most commonly occur on the knee, proximal femur or the humerus, but can occur in any bone.

Although not always symptomatic they can impinge nerves and vessels. They typically present in childhood and continue to grow until skeletal growth stops. Any osteochondroma that continues to grow after skeletal maturity should be removed due to an increased risk of malignancy.
Most osteochondromas do not require treatment. If there is impingement on any local structures they can be removed surgically.
They are often discovered incidentally when the bone is x-rayed for another reason (e.g. after trauma).
It is important to differentiate them from malignant bone tumours.
Most osteochondromas are solitary, but some individuals have multiple lesions. This is known as multiple osteochondromatosis – aka multiple hereditary exxotoses (MHE)

Epidemiology & Aetiology

  • Usually present in 2nd decade
  • M>F

Pathology

  • Probably the result of a piece of metaphysics in the wrong place or growing in the wrong direction
  • MHE:
    • Caused by a defect in the EXT gene
    • Often a strong Fix of MHE
    • Can cause short stature
  • Most commonly found around the knee or proximal humerus

Presentation

  • Often incidental
  • If close to joints:
    • May cause decreased ROM
    • May cause pain as  muscles and tendons slide over them
  • In MHE – can cause overall reduced growth and deformity
  • Can cause angular deformity if they affect a particularly integral part of the growth plate
    • In the upper limb, deformity can be severe
  • May cause a palpable lump – usually non-tender – unless there are inflamed overlying structures

Diagnosis

  • Is usually made with X-ray
    • Most bony tumours have specific radiographic features that can be distinguished on x-ray. A good radiologist should be able to give a diagnosis for many types of tumour based off the x-ray alone
  • Features of non-malignant bone lesions, including osteochondroma on x-ray include:
    • Well circumscribed border between normal and abnormal bone
    • No destruction of bone cortex
    • Does not extend into local soft tissues
    • Bony spur or prominences often grow away from the joint
  • Tumour in the scapula and pelvis can be particularly difficult to differentiate with x-ray and are more likely to require CT evaluation
  • Reduced growth in MHE
  • Check local lymph nodes – any inflamed nodes suggest a more dangerous cause (malignant bone lesion) and warrant further investigation
  • Consider CT or MRI if there is any concern about soft tissue involvement or impingement

Management

  • Most bony tumours in children require orthopaedic FU and investigation
    • The except may be a well defined osteochondromas found incidentally on an x-ray for another cause
    • Any symptomatic bony lesion, or any doubt about the diagnosis requires orthopaedic follow-up
  • If it is not causing any pain, or other localised issues, can usually be managed conservatively
    • May have annual x-ray to assess the extent of growth
  • Indications for surgical excision
    • Deformity
    • Aggravation of local soft tissue structure
    • Increase in size after skeletal maturity
    • Lesion in the spine, pelvis, scapula, proximal femur
  • Small risk of recurrence after excision
  • Small risk of malignant transformation
    • Usually to chondrosarcoma
    • Usually occurs in adulthood – and often heralded by the onset of pain and increasing size of the lesion
    • Lesion of the spine, pelvis, scapula and proximal femur are particularly prone to this – hence their indication for surgical management

Differential Diagnosis

References

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