Osteoid Osteoma
Radiology Cases in Pediatric Emergency Medicine
Volume 4, Case 15
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
     This is a 7-year old male who is seen in the acute 
care clinic with a history of recurrent pain in his left 
thigh for three months.  He has seen his primary care 
physician on two occasions.  Initially, this pain would 
awaken him at night, but it would subside on its own.  
When he saw his primary care physician for this, he 
was told it was growing pains.  He then began to 
complain of pain during the day.  He was given 
acetaminophen without relief.  His primary care 
physician prescribed ibuprofen and this helped to 
relieve the pain.  However, the pain continued to 
worsen and his parents decided to bring him to an 
acute care clinic after he complained of the pain all day 
in school.  There is no history of fever, trauma, or pains 
in other bones or joints.
     Exam:  VS T37.0 (oral), P88, R28, BP 100/50.  He is 
of average height and weight.  He is able to ambulate 
well with a slight non-specific limp to his gait.  He 
complains of some pain while walking.  He continues to 
complain of pain while he is sitting at rest.  He localizes 
his pain by pointing to his proximal thigh.  There is no 
position of comfort that completely relieves him of pain.  
His left hip has a diminished range of motion due to 
moderate tenderness.  There is some tenderness on 
palpation to the hip joint, but it is not severe.  There is 
no tenderness over his mid and distal femur.  His heart, 
lungs, and abdomen are unremarkable.  His other joints 
are unremarkable.  There is no lymphadenopathy.
     Radiographs of his hips are obtained.

View hip radiographs.

     AP (upper image) and frog (lower image) views are 
shown here.  His findings are best seen on the AP view.
     His left hip (right side of the image) shows some 
demineralization of the femoral head.  The joint space 
is slightly widened.  There is slight thickening of the 
medial cortex  of the femoral neck (the calcar).  There 
is a faint oval lucency within the femoral neck.  The 
radiologist suspects an osteoid osteoma.

View pointers on hip radiographs.

     The white outlined arrow points to the lucency within 
the femoral neck (the suspected osteoid osteoma).  The 
gray outlined arrow points to the thickened cortex along 
the calcar.  The vertical white lines measure the width 
of the hip joint space.  The "tear drop" distance 
measures the medial margin of the inferior aspect of the 
acetabulum to the adjacent femoral head.  This 
distance is wider in the left hip compared to the right 
     An ultrasound of the hips is obtained.

View hip ultrasound.

     The image on the left is the right hip.  The image on 
the right is the left hip.  The letter "F" marks the 
proximal femur.  The femoral head is to the left of the 
image.  The number "1" measures the width of the joint 
space in the right hip.  The number "2" measures the 
width of the joint space in the left hip.  The ultrasound 
confirms the presence of a small left hip effusion.
     A CT scan is ordered.

View CT scan. 

     This cut from the CT study is through the lucency 
noted in the femoral neck on the plain radiographs.  The 
arrow points to the osteoid osteoma.
     Our patient's symptoms improve with aspirin.  
Acetaminophen and ibuprofen do not result in 
significant pain relief.  His symptoms later worsen and 
standard doses of aspirin no longer control the pain  as
well.  The lesion is surgically resected.  Following 
surgery, his symptoms resolve.

     Osteoid osteoma is a benign bone tumor most 
commonly found in the 5 to 25 year age group.  The 
male to female ratio is 3 to 1.  The femur and tibia 
account for 50% of cases.  Other common sites include 
the hands, feet, and spine.
     Patients with spinal osteoid osteoma are difficult to 
diagnose since it does not usually reveal itself on plain 
radiographs.  These patients usually present with 
painful scoliosis.  Osteoid osteoma of the spine should 
be considered in young patients with painful scoliosis.
     The pain of osteoid osteoma is described as 
unrelenting and sharp, worse at night.  Classically, the 
pain is relieved by aspirin.  The source of the pain is 
unclear.  Prostaglandins are suspected, however, 
non-steroidal anti-inflammatory agents such as 
ibuprofen do not always relieve the pain as well as 
     The classic radiographic features of osteoid 
osteoma are a well-defined, round (or oval) radiolucent 
lesion with a surrounding radiodense zone (reactive 

View classic appearance.

     Both views show this classic appearance of an 
osteoid osteoma in the proximal left femur (central 
lucency with surrounding sclerosis).  While this 
appearance is classic, osteoid osteoma may have a 
subtle appearance as noted in the first set of 
radiographs.  Other common radiographic appearances 
of osteoid osteoma include dense bone alone or a 
lucency alone.
     It is common for osteoid osteomas to show 
osteopenia and cortical thickening in adjacent bone due 
to reactive sclerosis (as seen in the first patient).  
Intra-articular osteoid osteomas may result in joint 
     It is suspected that osteoid osteoma (and its pain) 
may resolve spontaneously.  This is thought to be due 
to spontaneous involution of the painful lesion.  In some 
instances, aspirin can be used to control the pain until 
spontaneous involution occurs.  However, in most 
instances, the pain intensity worsens and surgical 
resection is chosen.

     Springfield DS.  Bone and Soft Tissue Tumors.  In:  
Morrissy RT (ed).  Lovell and Winter's Pediatric 
Orthopaedics, third edition.  Philadelphia, J.B. Lippincott 
Co., 1990, pp. 323-363.
     Bisset GS.  Case 26:  Osteoid Osteoma.  In:  Siegel 
MJ, Bisset GS, Cleveland RH, et al.  Pediatric Disease 
(Fourth Series) Test and Syllabus.  Reston, Virginia, 
American College of Radiology, 1993, 691-719.

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Web Page Author:
Loren Yamamoto, MD, MPH
Associate Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine