Osteoid Osteoma

Definition

  • Small (< 1cm diameter of central nidus), solitary, benign, painful bone-forming tumours

Epidemiology

  • Relatively common
  • 10% of all primary bone tumours
  • Classically children & adolescents
  • Aged 5-25 years
  • M:F – 2:1
  • Most common site is lower extremity long bones (60-70%) usually near diaphysis
    • Femur 30%
      • Femoral neck & Intertrochanteric area most common femoral location
    • Tibia 25%
    • Foot 10%
      • Talus & Calcaneum most common in foot
    • Humerus 10%
    • Forearm 3%
    • Hand 10%
      • Scaphoid most common in wrist
    • Spine
      • Can occur in spine (Osteoblastoma more commonly) in posterior elements
  • Not infrequently located at the site of previous trauma
    • ? pathogenesis associated with trauma

Clinical Features

  • Characteristic pain
    • Intense, unrelenting
    • Chronic pain months/ years
    • Nocturnal
      • Due to prostaglandin production
    • Relieved by aspirin (narcotics often unhelpful)
  • Local swelling
    • Exquisitely tender
  • Mild Leucocytosis may be present
  • If intra-articular/ juxta-articular may present as synovitis of joint
  • Spinal lesions will show irritative scoliosis often

Radiology

Osteoid Osteoma, ct of an osteoid osteoma of the fibula
CT of an osteoid osteoma of the fibula. Image by Hellerhoff, Wikimedia Commons, CC BY-SA 3.0.

X-ray

  • Cortical location in long bone
    • Central lucent zone (Nidus)
    • Increased surrounding bone density with sclerosis
    • Fusiform shaped
    • May obscure nidus
    • Marked periosteal reaction may be present
    • Subperiosteal location = marked sclerosis
    • Endosteal location moderate sclerosis
    • Subarticular location = often no sclerosis
    • Nidus can be obscured by the surrounding sclerosis
  • Medullary
    • Four features (~ 50% show all 4)
      • Sharply round or ovoid
      • < 1cm
      • Homogenous dense centre
      • 1mm peripheral radiolucent zone
  • Differential on XR includes
    • Stress fracture
    • Osteomyelitis

CT Scan

  • Demonstrates nidus better
  • Location in cortex clearer
  • Thin sections 1-2mm
  • Low attenuation nidus
  • Central mineralisation
  • Surrounding endosteal & periosteal sclerosis

Bone Scan

  • Help with diagnosis & localisation of the tumour
  • Extensive ↑ uptake
  • Avidly take up the isotope due to osteoblastic activity in nidus
  • Also develops intense surrounding reaction
  • Can help localise intraoperatively

Pathology

Gross

  • Well demarcated cherry red nidus with gritty consistency
  • Surrounding dense bone with periosteal reaction & thickening

Microscopic

Histology of an osteoid osteoma nidus showing osteoid trabeculae and osteoblasts
Histology of an osteoid osteoma nidus showing osteoid trabeculae and osteoblasts. Image by Nephron, Wikimedia Commons, CC BY-SA 3.0.
  • Maze of small spicules of immature bone
  • Haphazard
  • Delicate trabeculae of osteoid
  • Rimmed by numerous osteoblasts
  • Enclosed in vascular spindle cell stroma
  • Numerous vascular channels & capillary network
  • Rich nerve fibres
  • Giant cells may be present
  • More mature lesions stroma sparsely cellular with intervening vascular spaces
  • No chondroid elements

Differential Diagnosis

Treatment

  • Generally remove the nidus
    • (May heal spontaneously but takes long time)
  • En Bloc Excision
    • Gold standard
    • Ensures all of lesion excised
    • Weakens bone
    • Need graft & protection
    • Send for intraoperative FFS & XR
  • “Burr Down” Technique
    • Excellent results
    • Intraoperative CT guidance
    • Direct incision over lesion
    • Shave cortex off with high speed burr to reactive bone
    • Scoop nidus out once hit hypervascular zone & sent for FFS
    • Burr 2mm zone out
    • Can leave strong reactive bone behind
  • Percutaneous Guided Reaming
    • CT-guided in XR suite
    • Doesn’t produce tissue for histology
  • Radiofrequency Ablation
    • CT-guided
    • No tissue for histology
    • Death occurs by thermal ablation
    • Uncertain results
  • Methods of localisation include
    • Image Intensifier
    • CT-guidance
    • Radioisotope probe
    • Intraop tetracycline fluorescence
  • If complete excision performed then recurrence very rare
  • However incomplete excision not uncommon & often leads to recurrence & failure of pain relief

OsteoBlastoma

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.