OSTEOID OSTEOMA

FREE LANCE RADIOLOGY Basic approach for

continuation of Diagnostic Radiology

education

19 Yr old male with pain in in the dorsal aspect of the medial

aspect of left mid foot . o/e there is pain

over the mentioned part of the left mid

foot .

General considerations/ Incidence /Clinical features

• :

• First described by Henry jaffe ( 1925). Not accepted for several decades and was considered as variant of osteomyelitis .

• 2.6% of all excised bone tumors and 11 % of all benign bone tumors .

• Young patients ( 10 to 25 years) . youngest patient reported was 8 month old patient with lesion in tibia . Male : female ratio is 2:1 .

• Clinical profile : • Pain +_ vasomotor disturbance ( profuse sweating / increased

skin temperature) . Classical description is of gradual onset of increasingly deep / severe / aching pain ( 65% will have night pain relieved by aspirin) . CAN BE CONFUSED WITH : septic arthritis , inflammatory , rheumatoid arthritis so patient may end up with rheumatology opinion.

General considerations /Incidence /Clinical features

• Localized swelling ,point tenderness , limitation of the motion, painful limp, stiffness , weakness of nearby joint , muscle atrophy may be noted. Painful scoliosis (lesion located in the concave side of the curve in thoracic / lumbar spine) . In cervical spine : torticollis / secondary contracture of the sternocleidomastoid muscle may be noted .Lesion in the spinous processs lead to localized pain and spinal stiffness .

• 50% occur in proximal femur / tibia ( predilection for upper end of the femur , particularly the neck / trochanteric region) .In spine : most of the lesions are in neural arch .

Pathological features /Radiologic features/Differential diagnosis /Treatment and prognosis:

• Lesion : Nidus ( reddish brown vascularised tumor <= 10mm) . Significant reactive sclerosis with cortical thickening / solid periosteal reaction encasing the nidus . Nidus is initially uncalcified and with maturity speck of calcification is seen in it . Bone expansion may be noted at the lesion site .

• Three anatomic locations of the osteoid osteoma : Cortical ( most common) , Cancellous ( intramedullary ) Subperiosteal . Histological and radiological appearance varies .

• Well developed lesion has lucent nidus with surrounding florid perifocal reactive sclerosis/appositional periosteal new bone formation ( typical of cortically placed osteoid osteoma ).The sclerosis is maximally seen caudal to the nidus . Nidus size is, <=1cm in diameter . Single roengenographic view may not be sufficient to demonstrate the nidus . central fleck of calcification is seen in the nidus with maturity .

• Intramedullary lesion that are intracapsular provoke much less reactive sclerosis because of low rate of bone production from intracapsular periosteum .

• Spinal osteoma’s are elusive lesions . lumbosacral strain , psychogenic back pain , cervical strain , herniated nucleus pulposus , biomechanical back pain are frequent prior diagnosis .Most spinal lesions are seen in the neural arch . Reactive sclerosis may give appearance of dense ivory pedicle or lamina . This appearance must be differentiated from stress response opposite a unilateral spondylosis,congenital agenesis of the contralateral pedicle , osteoblastoma , osteoblastic metastatic carcinoma .

• Angiography shows vascular blush in the arterial phase persisting late into the venous phase. This definitely differentiates the osteoid osteoma from brodies abscess which shows no such vascular blush in it’s necrotic cavity . On bone scan there is regional increase in the uptake ( double density sign)

Pathological features /Radiologic features/Differential diagnosis /Treatment and prognosis:

D/D AND TREATMENT

• D/D : – Garre’s chronic sclerosing osteomyelitis : This entity has been

disregarded as singular / distinct disease process.– Brodies abscess : Lucent nidus in brodies abscess is >1cm often

close to 2 cm ).Halo rim of sclerosis surrounding the nidus is more thick / irregular . Vascular blush seen in the angiographic phase in the osteoidosteoma is absent in the necrotic core of the osteoid osteoma . Note :Night pain relieved by aspirin is seen in brodies abscess and osteoid osteoma .

– Stress fracture : lesion may mimic osteoid osteoma . Sequential studies over time and images usually demonstrate the healing of the fracture .

• T/T : 1. Natural history of the disease is self limiting .2. Radiotherapy / thermocoagulation 3. Wide enbloc excision of the nidus and

sclerotic bone. (surgery may be delayed unless nidus of adequate size is seen) .

4. Recurrence is rare.

D/D AND TREATMENT

CONVENTIONAL RADIOGRAPHS

SITE OF PAIN

Single view may not be sufficient to demonstrate the roentgen findings of

osteoid osteoma so multiple views may be needed .

MR imaging : Good to demonstrate marrow edema

Dorsal aspect of the medial cuneiform has focal subcentimetre SIZED MR signal

change in the subcortical location. Appreciate significant ill defined marrow

edema

TIW T2W STIR

LONG AXIS CORONAL IMAGES

STIR IMAGE : MRROW EDEMA IN THE MEDIAL CUNIFORM AND ADJACENT SOFT

TISSUE

LONG AXIS SAGITTAL AND SHORT AXIS AXIAL IMAGE

STIR IMAGE

SAGITTAL MR IMAGES

TIW SEQUENCE STIR SEQUENCE

PLAIN CT IMAGE AND CORROBORATIVE MR IMAGE

( SPGR SEQUENCE)PLAIN CT SHOWS DENSE NIDUS ( MATURE CALCIFIED ) . <10mm . Cortical location with sclerosis around it

SPGR SEQUENCE OF MR defines the nidus in cortical location of medial cuneiform

CARRY HOME MESSAGE

1. HISTORY ( pain worse at night )2. CLINICAL EXAMINATION 3. CONVENTIONAL RADIOGRAPH

( multiple views) 4. CT ( for nidus)5. MRI ( for marrow edema)6. ANGIOGRAM ( to differentiate from brodies

abscess)All these modalities play important role to

define the fetaures of osteoid osteoma