■ Feature Article

Osteoid Osteoma: A Diagnosis for Radicular

Pain of Extremities
MOHAMAD H. EBRAHIMZADEH, MD; HOSEIN AHMADZADEH-CHABOCK, MD; ALI REZA EBRAHIMZADEH, PHD

abstract
Full article available online at OrthoSuperSite.com/view.asp?rID=44679

Osteoid osteoma is a benign tumor commonly found in young patients. The most inter-
esting feature of the tumor is its peculiar obvious pain. The intensity of pain produced
by osteoid osteoma is unproportionate to its nature and size. Much has been written
about the mechanism of this symptom of the tumor and the specific characteristics of
the pain that can be misleading when appearing as radicular pain especially when
some subtle neurologic signs and symptoms accompany the pain.

In this article, 12 patients who were referred to our clinic with radicular pain and
neurological signs and symptoms months after initiation of symptoms between 2000
and 2008 are presented. Of these 12 patients, most were first thought to have root
compression disease before being referred to our hospital.

Precise history taking and special attention to physical examinations led to a suspicion
of osteoid osteoma. Plain radiographs, computed tomography, and bone scans indi-
cated osteoid osteoma, and excisional biopsy confirmed its diagnosis.

Osteoid osteoma should always be considered in young patients with radicular pain,
even with subtle neurological signs and symptoms.

Drs Ebrahimzadeh (Mohamad) and Ahmadzadeh-Chabock are from the Mashad Orthopedic Re-
search Center, and Dr Ebrahimzadeh (Ali) is from the Department on Anatomy, Mashad University of
Medical Sciences, Mashad, Iran.
Drs Ebrahimzadeh (Mohamad), Ahmadzadeh-Chabock, and Ebrahimzadeh (Ali) have no relevant
financial relationships to disclose.
Correspondence should be addressed to: Mohamad H. Ebrahimzadeh, MD, Mashad Orthopedic Re-
search Center, Ghaem Hospital, Ahmad abad St, Mashad, Khorasan, Iran (ebrahimzadehmh@mums.ac.ir).
doi: 10.3928/01477447-20090922-23

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 ■ Feature Article

O
steoid osteoma is a benign tumor, of rich fibrovascular stroma, prominent aged as neurological patients with suspected
although some researchers believe osteoblasts, and osteoid tissue. This nidus nerve root compression disease.
that it is a tumor-like lesion and frequently is surrounded by reactive scle-
not a true neoplasia. It occurs 2 to 3 times rotic bone.5,6 RESULTS
as often in boys as in girls. Osteoid osteoma The natural history of the tumor is usu- Twelve of 41 patients (29.26%) with
has the greatest incidence in the second and ally spontaneous resolution over an average osteoid osteoma between 2000 and 2008
third decades of life (10-25 years).1 It is a of 6 years (range, 2-15 years) but NSAIDs who had radicular pain are presented in
relatively common tumor although some appear to speed the resolution, shortening this article.
reports of painless osteoid osteoma exist in the duration of symptoms to an average of In 9 patients, the tumor was located in
the literature, especially in childhood.2 The 33 months (range, 30-40 months).7 the femur. In 1 patient the tumor was in
characteristic feature of the tumor is its spe- Twelve cases of osteoid osteoma with the upper border of the acetabulum, 1 in
cific pattern of pain. The pain is vague, in- radicular pain that initially diverted the di- the humerus, and 1 in the olecranon fossa.
termittent, and nocturnal initially but grad- agnosis to spinal disorders are presented. There was a mean interval of 12.28 months
ually becomes continuous and intense in between the onset of symptoms and dis-
nature. The pain continues throughout the MATERIAL AND METHODS tinct diagnosis (range, 5-24 months).
day but is worse at rest, especially at night In this retrospective study, 12 patients All of the patients had radicular pain
and is markedly relieved by nonsteroidal with final diagnoses of osteoid osteoma with pain in the vicinity of the tumor ori-
anti-inflammatory drugs (NSAIDs).1,3 Pain were initially referred to our institution gin. Patients with osteoid osteoma in the
usually is present for several months before with radicular pain in the extremities. femur reported radicular pain from the
radiographic findings, and the interval be- These 12 patients were out of a larger buttock or hip region to below the knee,
tween symptoms and correct diagnosis is group of 41 patients with diagnoses of and in 2 cases the pain continued to the
seldom ⬍6 months.1,3 osteoid osteoma referred to our institution foot (Figures 1-3). The patient with the
Radiographs show a nidus of various between 2000 and 2008. There were 8 tumor in the acetabular margin also pre-
sizes but ⬍2 cm in diameter. It is sur- males and 4 females (M/F=2) with a mean sented with a limp and reported radicular
rounded by a variable amount of sclerosis age of 19.08 years (range, 11-22 years). pain from the hip to the knee. The patient
depending on tumor location. When it is Patients referred to our clinic with neuro- with osteoid osteoma in the humerus pre-
in its most common site (cortical lesion), logical manifestations who were suspected sented with radicular pain from the dorsal
there is abundant fusiform sclerosis sur- of having osteoid osteoma after bone scan aspect of the arm to the dorsal region of
rounding the nidus, which is found less and computed tomography (CT) underwent the forearm ending at the wrist.
in subperiosteal and cancellous osteoid surgical excision. Osteoid osteoma was then The olecranon fossa lesion presented
osteomas.3,4 There is a predilection for verified on histologic examination. All pa- with radicular pain from the anterolateral
lower extremities, especially the femur tients reported intense radicular pain before of the arm and forearm to the wrist. One
and tibia.3,5,6 Nidus histologically consists admission, many of whom had been man- patient with a tumor in the distal femur had
accompanying knee effusion in addition to
radicular pain from the thigh to the leg. All
of the patients had point tenderness at the
origin of the lesion (Table 1). Six of 10 pa-
tients who had a tumor in the femur or ac-
etabulum on physical examination showed
quadriceps atrophy and mild weakness, and
in 1 patient straight-leg rising was positive,
suggesting disk herniation (Figures 4-6).
In all but 1 patient who received as-
pirin or NSAIDs, pain resolution was
significant. In 11 of 12 patients, electro-
diagnostic tests (electromyography, nerve
conduction velocity) showed some abnor-
1 2
malities compatible with root irritation in
Figure 1: Case 2. An unremarkable radiograph of an 11-year-old boy with a 7-month history of radicular
pain from the groin to the medial knee. Figure 2: Case 2. T99 bone scan shows increased uptake in the
3 patients, which made the condition more
proximal femur. obscure.

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 OSTEOID OSTEOMA | EBRAHIMZADEH ET AL

All patients had plain radiographs of ed with locked intramedullary nailing and ameter is ⬍2 cm with a distinct surround-
the suspected site (tenderness was the the fracture went on to complete union. No ing reactive sclerosis that is more appar-
main marker) in which only 6 patients infections occurred postoperatively. ent in cortical lesions. Pain is predominant
showed abnormal findings, suggesting os- and the most interesting symptom of the
teoid osteoma, including cortical thicken- DISCUSSION tumor. Although intramedullary tumors
ing sclerosis and central lucency. Osteoid osteoma is a benign tumor produce pain when they invade the richly
In all patients bone scan with techne- commonly found in young patients. Its di- innervated periosteum, it is common for
tium 99m was performed. In 11 patients
it showed increased uptake with double
density sign. Computed tomography scan
with thin slices showed the typical nidus
in all 12 patients (Table 2). Excision was
planned. All 12 patients underwent sur-
gery and histological examination con-
firmed osteoid osteoma.
A mean of 3.3-year follow-up (range, 1-
5 years) was considered. In 10 patients com-
plete resolution of symptoms was evident.
Two patients continued to have symp-
toms, but to a lesser degree. On a numeri-
cal scale pain decreased from 8 to 3 in 1
patient and from 9 to 5 in the other pa-
tient. The pain gradually disappeared with
NSAIDs in approximately 6 months.
In 1 patient with osteoid osteoma of the
femoral diaphysis after resection of the tu-
mor, a diaphyseal femoral fracture occurred
while cycling at 3 months postoperatively. 3
The diaphyseal femoral fracture was treat- Figure 3: Case 2. CT scan revealed the nidus.

Table 1
Clinical Features of the Patients

Patient No./ Duration of

Sex/Age, y Symptoms, mo Location Pain Characteristics
1/M/22 8 Lesser trochanter Radicular pain from groin to medial of the knee
2/M/11 7 Proximal femur Radicular pain from groin to medial of the knee
3/M/21 5 Proximal femur Radicular pain from buttock to dorsal of the calf
4/F/17 13 Proximal femur Radicular pain from groin to below the knee
5/M/17 20 Proximal femur Radicular pain from groin to dorsal of the foot
6/M/19 24 Femoral shaft Radicular pain from buttock to dorsolateral of the foot
7/F/20 24 Femoral shaft Raducular pain from groin to medial of the knee
8/M/18 6 Proximal femur Radicular pain from dorsal of the thigh to anterolateral of the calf and
to dorsolateral of the foot
9/M/22 8 Proximal & distal femur Radicular pain from groin to the knee, medial of the calf and medial
of the foot
10/F/22 5 Upper border of the acetabulum Radicular pain from groin to medial of the knee
11/M/20 12 Humeral shaft Radicular pain from dorsal elbow to dorsal of forearm ending at the wrist
12/F/20 15 Olecranon fossa Radicular pain from anterolateral arm and forearm ending at the wrist

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 ■ Feature Article

4 5 6
Figure 4: Case 1. A 22-year-old woman with an 8-month history of radicular pain in the anterior thigh, unremarkable radiograph, radiolucency in the lesser trochanter.
Figure 5: Case 1. Normal MRI of the lumbosacral spine for disk herniation. Figure 6: Case 1. T99 bone scan revealed the lesion in the lesser trochanter.

Table 2
Physical and Paraclinical Findings of the Patients

Technetium
99m Bone Scan
Positive Physical Response to Electrodiagnostic Electrodiagnostic
Patient Findings NSAIDs Evaluation Evaluation CT Scan Plain Radiographs
1 Point tender- Good response to Normal EMG, NCV Increased uptake Showed the nidus Nothing diagnostic
ness, quadriceps aspirin
atrophy
2 Point tender- Good response to Increased uptake Showed the nidus Peritrochanteric os-
ness, quadriceps aspirin teoporosis, nothing
atrophy diagnostic
3 Point tenderness Good response to Increased uptake Showed the nidus Nothing diagnostic
aspirin
4 Point tender- Good response to Abnormal EMG, Increased uptake Showed the nidus Suspected nidus in
ness, quadriceps aspirin NCV lesser trochanter
atrophy
5 Point tenderness, Good response to Normal EMG, NCV Increased uptake Showed the nidus Sclerosis in intertro-
quadriceps atro- aspirin chanteric line
phy, calf atrophy
6 Point tenderness Good response to Increased uptake Showed the nidus Nothing diagnostic
aspirin
7 Point tenderness, Good response to Abnormal EMG, Increased uptake Showed the nidus Cortical thickening
Limping positive aspirin NCV
SLR at 50⬚
8 Point tender- Good response to Normal EMG, NCV Increased uptake Showed the nidus Nothing diagnostic
ness, quadriceps aspirin
atrophy
9 Point tenderness, Good response to Normal EMG, NCV Increased uptake Showed the nidus Nothing diagnostic
knee effusion aspirin
10 Point tenderness, No response to Normal EMG, NCV Normal uptake Showed the nidus Sclerosis lesion in
quadriceps atro- NSAIDs upper border of the
phy, limping acetabulum
11 Point tenderness, Good response to Normal EMG, NCV Increased uptake Showed the nidus Cortical thickening
weak extension aspirin
of the wrist and
fingers
12 Point tenderness Good response to Abnormal EMG, Increased uptake Showed the nidus Sclerosis in olecra-
aspirin NCV non fossa
Abbreviations: CT, computed tomography; EMG, electromyography; NCV, nerve conduction velocity; NSAIDs, nonsteroidal anti-inflammatory drugs.

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 OSTEOID OSTEOMA | EBRAHIMZADEH ET AL

large tumors to be asymptomatic even un- arteries supplying the nidus and assumed
til late in the tumor course. Intense pain these changes as support for Jaffe’s hy-
produced by a small lesion is an odd con- pothesis of intravascular pressure. Schul-
spicuous feature of osteoid osteoma.1-4,8,9 man and Dorfman17 using a specific silver
Although pain with its distinct char- stain demonstrated nerve fibers accompa-
acteristic is usually felt where the lesion nying blood vessels and arteriols within
is located, referred and radicular pain is the nidus. Nerve fibers appeared to be un-
not uncommon and when accompanying myelinated. They also illustrated similar
muscle wasting and weak deep tendon nerve fibers in fibrous tissue surrounding
reflex (knee jerk and ankle jerk), osteoid the nidus. They suggested that increased
osteoma can be a diagnostic dilemma.3,10 vascular pressure stimulates afferent
Many hypothesis have been proposed nerves in close proximity to blood ves-
for the mechanism of this peerless pain sels that could be a part of the autonomic
pattern. World et al and Greco et al dem- system and thus could be the pathway for
onstrated increased concentration of pros- pain perception.
taglandin E2 in the nidus of osteoid osteo- Halperin et al18 and Esquerdo et al19 also
ma, which reaches as high as 100 to 1000 in 2 different studies found unmyelinated fi-
times that of normal bone.11-13 bers generally surrounding small arterioles
Mungo et al7 proposed that both cy- even near the center of nidus. De chadare-
clooxygenase-1 (Cox-1) and cyclooxy- vian et al5 and Sherman and McFarland20
genase-2 (Cox-2) enzymes are highly ex- failed to demonstrate unmyelinated nerve 7
pressed in osteoblasts in osteoid osteoma. fibers in nidus itself but showed their exis- Figure 7: An algorithm for diagnosis of a young
They concluded that the high production tence in the fibrous zone around the nidus. patient with radicular pain resulting from osteoid
osteoma.
of prostaglandins by osteoid osteoma is It is proposed that these nerve fibers can be
likely to be mediated by cyclooxygenase stimulated by increased vascular pressure the posterior aspect of the upper third of
enzymes. They could not detect Cox-2 in or direct irritation. These autonomic nerve the tibia can radiculate up the thigh to the
other tumors and in surrounding host bone fibers with their spinal origin can account hip.1,3 McCauley et al22 reported 2 patients
while Cox-1 could be detected in other tu- for radicular symptoms, and localization of with ankle pain referred from osteoid os-
mors and host bone. They concluded that the pain and sensory finding remote from teoma in the proximal tibia.
Cox-2 is the main mediator for prosta- the tumor origin can be explained in a simi- Radicular pain combined with muscle
glandin synthesis and thus selective Cox-2 lar manner.2,5,11,15,19,21 wasting (as much as 48% of cases) and
inhibitors can be used safely to treat oste- In addition to the above hypothesis for weak deep tendon reflexes (as much as
oid osteomas conservatively.7 the source and reason for radicular pain of 34% of cases) strongly simulates spinal
Haseqawa et al14 showed nerve fibers osteoid osteoma, a local informatory pro- root compression and disk herniations.3
in the fibrous zone around the nidus of os- cess may cause local point tenderness and There are reported cases of neurologic
teoid osteoma but did not detect nerve fi- adjacent nerve irritation, which produces symptoms even with the straight leg ris-
bers in other tumors, while prostaglandin radicular pain in the involved nerve. ing test.3
E2 could be detected in other tumors as On rare occasions when osteoid oste-
well. They concluded that the presence of oma presented as a painless tumor, nerve CONCLUSION
nerve fibers alone might play a more im- fibers could not be found.17 Although the When treating a young patient with
portant role in pain perception in osteoid characteristic pain is usually felt in the vi- radicular pain even with subtle neuro-
osteoma than the effect of prostaglandin cinity of tumor origin, referred and radic- logic abnormalities (sensory deficit, weak
E2 on the nerves. ular pain is a familiar feature of the pain. deep tendon reflex, and muscle atrophy),
When Jaffe15 observed prominent ar- More than 26% of our patients with osteoid nature of the pain (nocturnal or worse at
teriols and hypervascularization with osteoma had radial pain patterns, therefore rest) and response of the pain to NSAIDs
abundant autonomous vascular supply of osteoid osteoma should be suspected in a while seeking point tenderness suggesting
osteoid osteoma, he suspected blood pres- young patient with radicular pain. Tumors osteoid osteoma, can help avoid a misdi-
sure inside the rigid wall to be responsible in the femur can present with a radicular agnosis. Premature magnetic resonance
for pain. Aszódi16 later observed charac- or referred pain from the buttock or groin imaging of the spine or electrodiagnostic
teristic features of arteriosclerosis in small to the knee and calf. Osteoid osteoma in test results may be misleading.

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 ■ Feature Article

Plain radiographs of the point of ten- Dev Pathol. 2007; 10(5):358-368. Ikata T, Hizawa K. Mechanism of pain in
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RN, Puzas JE, Schwarz EM. Cox-1 and cox- ing of osteoid osteomas. Arch Orthop Un-
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