Please confirm topic selection

Are you sure you want to trigger topic in your Anconeus AI algorithm?

Please confirm action

You are done for today with this topic.

Would you like to start learning session with this topic items scheduled for future?

Images
https://upload.orthobullets.com/topic/8012/images/Case B - femur - xray - Parsons_moved.png
https://upload.orthobullets.com/topic/8012/images/Osteoid Osteoma - Xray - proximal fibula_moved.jpg
https://upload.orthobullets.com/topic/8012/images/Osteoid Osteoma - CT scan_moved.jpg
https://upload.orthobullets.com/topic/8012/images/Osteoid Osteoma - Histology_moved.jpg
https://upload.orthobullets.com/topic/8012/images/osteoid17.jpg
  • Summary
    • Osteoid Osteomas are small, benign, osteogenic bone lesions most commonly found in the proximal femur. Patients typically present between ages 5 and 25 with regional pain that is worse at night and improves with NSAIDs.
    • Diagnosis is made radiographically by a characteristic lesion that is less than 1.5 cm in diameter with a sclerotic margin and radiolucent nidus. 
    • High resolution CT scan distinguishes osteoid osteomas from other radiolucent bone lesions
    • Treatment is usually nonoperative with observation and NSAID for pain control. Radiofrequency ablation or surgical resection may be indicated in patients with progressive and severe symptoms.
  • Epidemiology
    • Incidence
      • accounts for 10-14% of all benign bone tumors and 2-3% of all primary bone tumors
      • peak incidence in 2nd decade of life
    • Demographics
      • 2.5:1 male-to-female ratio
      • persons aged 5-25 years (70% present before age of 20)
    • Anatomic location
      • most common
        • lower extremity (>50%)
          • proximal femur > tibia diaphysis
            • usually found within the bone cortex
        • spine (10-15%)
          • thoracic and lumbar regions > cervical and sacral
          • majority involve the posterior elements
          • usually found on the side of concavity in scoliosis
        • hand (5-10%)
          • usually involve scaphoid and proximal phalanx
        • foot (<5%)
          • predominantly involves the talar neck
  • Etiology
    • Pathophysiology
      • pathoanatomy
        • nidus
          • characterized by a central nodule of woven bone and osteoid with osteoblastic rimming
        • reactive zone
          • area of thickened bone and fibrovascular tissue
      • cellular biology
        • pain
          • attributed to increased local concentration of prostaglandin E2 and COX1 & 2 expression
            • explains why pain improved with NSAIDS
          • increased number and size of unmyelinated nerve fibers within the nidus
    • Associated conditions
      • orthopedic manifestations
        • scoliosis with lesion on concave side of the curve
          • thought to result from marked paravertebral muscle spasm
        • growth disturbance
          • epiphyseal involvement could result in elongation of affected limb and resultant limb length discrepancy 
        • flexion contractures
  • Classification
      • Enneking Classification of Benign Lesions
      • Grade
      • Examples
      • Stage 1
      • Latent lesions
      • Enchondroma
      • Non-ossifying fibroma
      • Stage 2
      • Active lesions
      • Osteoid osteoma
      • UBC
      • ABC*
      • Chondroblastoma
      • Chondromyxoid fibroma
      • Giant cell tumor of bone*
      • Stage 3
      • Aggressive lesions
      • Giant cell tumor of bone*
      • ABC*
  • Presentation
    • Symptoms
      • pain
        • constant and progressive
        • worse at night and with drinking ETOH
        • relieved by NSAIDS
        • location may be adjacent to joint and mimic arthritis or within posterior spinal elements and cause scoliosis
      • swelling
        • hand lesions may present with painless swelling
    • Physical exam
      • inspection
        • palpable bone
          • deformity, swelling, erythema, tenderness
        • proximity to a joint
          • effusion, contracture, limp, muscle atrophy
        • spine
          • painful scoliosis due to paravertebral muscle spasm
  • Imaging
    • Radiographs
      • views
        • obtain orthogonal views of affected bone or joint
      • findings
        • intensely reactive bone around a radiolucent nidus
        • because of intensely reactive sclerosis, may be possible to detect nidus only with CT or MRI
    • CT
      • indication
        • considered imaging modality of choice
          • CT provides better contrast between lucent nidus and reactive bone compared to MRI
          • High resolution CT scan specifically best identifies the "vascular groove sign" - linear/serpentine cortical lucencies which represent vascular channels
            • Vascular groove sign can be detected in 80% of cases via high resolution CT
            •  distinguishes osteoid osteomas from other radiolucent bone lesions
            • Imaging modality of choice
        • characteristic findings of the nidus
          • the area of reactive bone sclerosis may be greater than the diameter of the nidus
          • Vascular groove sign (usually 1mm on diameter) 
          • usually < 1.5 cm (otherwise think osteoblastoma)
          • target-shaped/bulls-eye appearance, representing calcified center of the nidus   
            • present 50% of the time
    • Bone scan
      • indications
        • concerning features on radiograph or advanced imaging
      • findings
        • intense area of focal uptake at the nidus
        • low uptake in reactive zone peripherally
          • known as the 'double-density sign'
    • MRI
      • indications
        • usually not recommended as bone marrow edema appreciated on MRI can mask typical features of tumors
        • can be useful in illustrating nidus in cases of intra-articular lesions
      • findings
        • must be interpreted with reference to x-ray or CT scan
  • Studies
    • Histology
      • distinct demarcation between nidus and reactive bone
        • nidus
          • contains uniform osteoid seams of immature osteoid trabeculae (woven bone) with a sharp border of osteoblastic rimming
          • uniform plump osteoblasts have regularly shaped nuclei with abundant cytoplasm
        • reactive zone
          • region surrounding the sclerotic border
        • lesion does not infiltrate the surrounding bone
  • Differentials
    • Long bone osteoid osteomas need to be differentiated from
      • stress fx
      • osteomyelitis
      • Ewing's sarcoma
    • Posterior spinal element lesions need to be differentiated from
      • aneurysmal bone cyst
      • osteoblastoma (see table below)
      • Osteoid osteoma vs. Osteoblastoma
      • Osteoid Osteoma
      • Osteoblastoma
      • Incidence
      • 10% of benign tumors
      • 3% of benign tumors
      • Size
      • < 2 cm (typically <1.5cm)
      • > 2 cm (average, 3.0 - 3.5 cm)
      • Site
      • > 50 % in long bone diaphysis
      • > 35% in posterior elements of the spine
      • Location
      • Proximal femur > tibia diaphysis > phalanges > spine
      • Vertebral column > long bone diaphysis/metaphysis
      • Natural History
      • Self-limited
      • Progressive
      • Histology
      • Benign appearance. No growth potential. Central nidus composed of more organized osteoid and lined by osteoblasts.
      • Benign appearance. Localized growth that is not self-limiting. Central lesion less organized with greater vascularity.
      • Symptoms
      • Nocturnal pain, relieved by NSAIDS. If spine involvement, presents 75% of the time with painful scoliosis with lesion on concave side of curve
      • Dull ache, partial response to NSAIDS. Neurologic symptoms common if spine involvement.
      • Management of Spine lesions
      • Nonsurgical management is indicated as first-line treatment, definitive treatment is percutaneous RFA/surgical resection 
      • Surgery is always indicated as they do not respond to nonsurgical treatment.
  • Treatment
    • Nonoperative
      • clinical observation and NSAID administration
        • indications
          • first line of treatment for most extremity lesions
            • in 50% of patients treated with NSAIDs, lesions burn out and resolve after several years
            • NSAIDS can be effective for limiting pain
            • not ideal for every patient given the harmful effects of NSAIDs (gastritis, AKI, etc)
          • painful spine lesions without scoliosis
      • MR-guided high-intensity focused ultrasound (MR-HIFU)
        • overview
          • based on MR imaging, therapeutic ultrasound energy transferred transcutaneously causing thermal ablation to the periosteal nerves, which penetrates the medullary bone and coagulates the osteoma nidus
        • indications
          • failure of medical management
          • compared with surgery and RFA, MR-HIFU is a non-invasive and non-ionizing treatment option
          • comparable clinical response to RFA 
    • Operative
      • percutaneous radiofrequency ablation
        • indications
          • considered standard of care
            • compared to surgery, RFA allows for access to more challenging anatomic sites, decreases procedure time and hospital stay length, and decreases costs
          • spine lesions
            • RFA can be safe and effective for spinal osteoid osteoma based on motor response testing performed during procedure
            • for lesions close to neurovascular structures, a distance of 1-1.5cm should be kept between probe and sensitive anatomy to prevent damage
          • periarticular lesions
            • safe for periarticular lesions if probe is >1cm away from articular surface, otherwise may risk damage to articular cartilage
        • outcomes
          • 90% of patients are successfully treated with 1-2 sessions of RFA
          • 10-15% recurrence rate
      • surgical resection with curettage
        • indications
          • location of lesion is not amenable to CT-guided percutaneous radiofrequency ablation
            • e.g. close to skin or nerve
          • en bloc resection indicated in spinal disease if osteoid osteoma is associated with fixed spinal deformity or if RFA unsafe due to proximity to dura/nerve roots
          • lesions that reoccur after RFA
          • digital lesions
            • RFA carries risk of thermal skin necrosis and injury to digital neurovascular bundle
        • outcomes
          • 94% success with local excision
          • associated spinal deformity can resolve spontaneously if the lesion is resected within 15 months of onset of deformity
  • Techniques
    • Percutaneous radiofrequency ablation 
      • done under CT guidance
      • radiofrequency electrode inserted into the nidus (cad)
      • probe heated to 90 deg C for 4-6 minutes to produce a 1cm zone of necrosis
    • Surgical resection with curettage
      • successful treatment depends on complete marginal resection of nidus (sclerotic bone is normal and can be left behind)
        • percutaneous approach
        • open approach
  • Complications
    • RFA related complications
      • recurrence: 10-15% recurrence rate
      • cellulitis, thrombophlebitis, skin necrosis
        • increased risk if lesion is <1.0 cm from skin
      • neurovascular damage - increased risk if lesion <1.0-1.5cm from neurovascular bundle
    • Limb length discrepancy
      • elongation of affected limb and resultant limb length discrepancy may occur if osteoid osteoma effects the epiphysis
  • Prognosis
    • Pain from lesions usually resolves after an average of 3 years
    • The lesion spontaneously resolves in 5-7 years
    • overall good prognosis, with extremely rare malignant transformative potential
Card
1 of 31
Question
1 of 22
Private Note