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Computed tomography of osteoid osteoma
CT: THE JOURNAL
COMPUTED
TOMOGRAPHY
OF COMPUTED
KEY WORDS:
Computed tomography; Osteoid osteoma; Acetabulum; Knee; Spine
Osteoid osteoma is a benign tumor of bone. It usually presents with skeletal pain that is often worse at night, and may be relieved substantially with aspirin. In its classic form, the radiographic diagnosis presents no significant problem when a radiolucent nidus surrounded by a zone of osteosclerosis is demonstrated. In most patients, this is usually achieved fairly easily with conventional radiography when the lesion is located in the metaphysis or diaphysis of the long bones of the extremities. However, when osteoid osteoma occurs in anatomic regions containing curvilinear and overlapping bony surfaces-such as the spine and pelvis-it may not be possible to visualize the osteoid osteoma on conventional radiography and tomography studies. Diagnosis of osteoid osteoma in this group of patients
From the Department of Radiology, New York University Medical Center, New York, New York. Address reprint requests to: Hossein Firooznia, MD, Department of Radiology, New York University Medical Center, 560 First Avenue, New York, New York 10016. Received November 1984. 0 1985 by Elsevier Science Publishing Co., Inc 52 Vanderbilt Ave., New York, NY 10017 0149-936X/851$3.30
1985: 9265-268
265
OF OSTEOID OSTEOMA
HOSSEIN FIROOZNIA, MD, MAHVASH AND CORNELIA GOLIMBU, MD
Computed tomography revealed a radiolucent nidus with Q surrounding zone of osteosclerosis in 17 patients with osteoid osteoma. Plain films did not reveal any abnormality in 5 patients. COnVentiOnQl tomography was negative in 3 patients. Computed tomography is the modality of choice for detection of osteoid osteoma when the lesion is deep-seated or when it occurs in complex anatomic regions with curvilinear and overlapping surfaces, such QS acetabulum, knee, and spine.
TOMOGRAPHY
RAFII,
MD,
may be delayed for several months, possibly leading to inappropriate medical and surgical treatment. Computed tomography (CT) is particularly useful in this group of patients. It provides information that leads to a timely diagnosis and facilitates surgical resection. MATERIALS
AND METHODS
There were 17 patients (5 female, 12 male) ranging in age from 8 to 26 years (mean age, 21 years). Diagnosis of osteoid osteoma was verified histologically in 16 patients. One patient, with a clinical and radiographic diagnosis of osteoid osteoma, but without histologic verification, is being followed. The lesion occurred in the following locations: metaphysis or diaphysis of long bones, 12 patients; spine, 2 patients; acetabulum, 2 patients: and knee, 1 patient. Conventional radiography and CT studies were performed in 17 patients, conventional tomography in 3 patients, and radionuclide (“gmTc-MDP) bone scanning in 6 patients. The CT studies were performed on a GE 8800 CT/T or GE 9800 CT/T units (14 patients) or a Phillips Tomoscan 310 unit (3 patients). The CT slices were 3 to 5 mm thick and spaced consecutively. Intravenous contrast medium consisting of a 30% solution of diatrizoate meglumine (Reno-M-DIP, Squibb, Princeton, N.J.), in the form of a drip infusion, 2 mL per pound of body weight, was utilized in 4 patients. Conventional tomography was performed with a Phillips Polytome unit, utiizing hypocycloidal motion. The tomography cuts were obtained at !&mm intervals. RESULTS Conventional radiography revealed a radiolucent nidus with a surrounding zone of osteosclerosis in 10 patients. In 4 patients in this group, an area of calcification was noted in the nidus. In 5 patients (2 spine, 2 acetabulae, 1 knee) no significant abnor-
266
FIROOZNIA
ET AL.
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL.
9 NO.
3
FIGURE 1. A CT scan through the proximal epiphysis and metaphysis of the nidus tibia. A radiolucent containing calcification is noted in the right tibia. Note surrounding osteosclerosis the nidus.
CT scan FIGURE 2. A through the roof of the acetabulum. The cortex of the
anterior wall of the left acetabulum is displaced anteriorly by a bubble-like expanThere is sion (nidus). marked edema and swelling of the adjacent soft tissues.
malities were detected. In 2 patients (1 proximal fearea of osmur, 1 distal tibia), only a questionable teosclerosis was noted. Bone scanning revealed a focal area of increased tracer uptake in all 6 patients in whom it was performed. Conventional tomography in 3 patients (1 acetabulum, 1 knee, 1 spine) did not reveal the characteristic finding of osteoid osteoma and was not helpful in diagnosis. The CT studies revealed a focal area of radiolucency (nidus) surrounded by various degrees of sclerotic reactive changes in all patients. The sclerotic reaction was less marked in lesions occurring in the trabecular bone of the metaphysis and epiphysis. Calcification within the nidus was noted in 6 lesions. Soft tissue swelling was noted in 2 deep-seated lesions and in 13 lesions that were located at, or close to, the outer cortex of bone. In 2 deep-seated lesions, no soft tissue swelling was noted. Postoperative CT examinations were performed in 3 patients. Computed tomography confirmed ab-
sence of the nidus following surgical resection in 2 patients. In one patient with consistent complaint following surgery, a radiolucent nidus, moderately smaller than the one present prior to surgery, was found. This was thought to be either due to incomplete surgical resection or emergence of a new nidus.
DISCUSSION Osteoid osteomas occur most commonly in the second and third decades of life. They are most commonly located in the long bones of the lower extremities. In our experience, approximately 15% to 20% occur in the remainder of the skeleton. According to Jackson et al. (1) and Price et al. (Z), the spinal column is involved in about 10% of the cases. The lumbar and cervical vertebrae are more frequently involved than the thoracic and sacral vertebrae. The lesion most frequently affects the
TULY 1985
FIGURE 3. (A,B) These CT scans through the femoral neck and intertrochanteric region demonstrate osteosclerosis of the cortex of the left femur anteriorly associated with an intra- and subcortical nidus, calcification in the nidus, and marked swelling of the adjacent soft tissues.
OSTEOID
OSTEOMA
267
A
posterior arch (neural arch), rather than the body of the vertebrae. In the posterior arch, the laminae are most frequently involved, followed by the articulating facets and pedicles (3). The radiographic manifestations of osteoid osteoma consist of a radiolucent nidus, which may contain an area of calcification, and a surrounding zone of reactive osteosclerosis (z-7). The nidus is usually less than 10 mm in diameter (2). In our experience, the intensity and extent of osteosclerosis
in osteoid osteoma-indeed the reactive changes occurring in most other lesions of bone-depend most importantly on the anatomic location of the lesion. That is, the ability of the host bone to react-trabecular bone versus cortical bone-is the most important factor. Thus, an osteoid osteoma occurring in the diaphysis of a long bone, particularly in a growing adolescent, may exhibit a larger and more intense area of osteosclerosis. On the other hand, when an osteoid osteoma arises in the sub-
268
FIROOZNIA
ET AL.
stance of trabecular bone, for example the epiphysis of a long bone, only a mild osteosclerosis may be present. The radiographic diagnosis of osteoid osteoma is dependent upon visualization of the nidus and the surrounding osteosclerosis. This is accomplished by conventional radiography and tomography in most osteoid osteomas of the extremities. In these cases it is possible to project the suspected area of the skeleton free from the adjacent bony surfaces. However, as occurred in five patients in this series, it may not always be possible to visualize the lesion on conventional radiography studies. This may occur when the lesion is in a deep-seated location (Figure l), or when complex curvilinear and overlapping bony surfaces are present, as in acetabulum (Figure 2) or spine. By virtue of its cross-sectional imaging capability, CT overcomes these difficulties and demonstrates these lesions free from overlapping by the adjacent bony structures. Furthermore, CT usually reveals unexpectedly large soft tissue swelling surrounding these lesions (Figures 2 and 3). Intravenous contrast medium administration in four patients in this series led to a more pronounced delineation of the soft tissue swelling. We noticed no significant enhancement of the soft tissue structures within the nidus. Radionuclide bone scanning is a very sensitive but nonspecific procedure that almost always reveals a focal area of increased tracer concentration in patients with osteoid osteoma (8). We believe it should only be used for localization purposes in patients with persistent and diffuse or referred pain, and in patients in whom no definite abnormalities are noted on conventional radiography. The localization of the abnormality is also helpful in developing a tailored CT examination of the involved area. Another application of radionuclide scanning is in intraoperative scintimetry. A complete surgical resection of the nidus can be facilitated through intraoperative bone scintimetry without recourse to block resection (8, 9). This is particularly applicable to regions where relatively extensive block resection is not advisable, such as the spine and articular surfaces. In our experience, CT is most helpful in diagnosis of deep-seated osteoid osteomas and where there is significant overlapping of the bony surfaces. As for other bone lesions CT is particularly helpful in osteoid osteomas situated in the inner portion of the metaphysis and epiphysis of the femur and tibia, and in osteoid osteoma of the spine, scapula, pelvic bones (acetabulum, sacrum), talus, and OS calcis. Also, by demonstrating the precise three-dimensional position of the lesion, CT is helpful in plan-
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL. 9 NO. 3
ning the surgical approach, particularly in deepseated and complex anatomic regions. It is also helpful for assessing the adequacy of the surgical resection and detecting a persistent or recurrent nidus.
REFERENCES 1. Jackson RP, Reckling FW, Mautz FA: Osteoid osteoma and osteoblastoma: Similar histologic lesions histories. Clin Orthop 1977;128:303-13.
with different
natural
2. Price HI, Batnitzky S, Levine E, Rosenthal SJ: The computed tomographic findings in benign disease of the vertebral column. Radiographics 1984;4:2,283-313. 3. Gamba LJ, Martinez S, Appe J, et al.: Computed tomography of axial skeletal osteoid osteoma. AJR 1984;142:769-72. 4. Omojola MF, Cockshott NP, Beatty EG: Osteoid osteoma: An evaluation of diagnostic modalities. Clin Radio1 1981;32:199204. 5. Swee RG, McLeod RA, Beabout tion, diagnosis, and localization.
JW: Osteoid osteoma: DetecRadiology 1979;130:117-23.
6. Wedge JH, Chang ST, McFayden DV: Computed tomography Iocalizationof spinal osteoid osteoma. Spine 1981;6:423-7.
in
7. Jaffe HL: Osteoid osteoma: A benign osteoblastic tumor composed of osteoid and atypical bone. Arch Surg 1935;31:709-28. 8. Ghelman B, Thompson FM, Arnold WD: Intra-operative radioactive localization of osteoid osteoma. J Bone Joint Surg 1981;63A:8267. 9. O’Brien TM, Murray TE, Malone LA, et al.: Osteoid osteoma: excision with scintimetric guidance. Radiology 1984;153:543-4.
CONTINUING MEDICAL EDUCATION QUESTIONS 1. Osteoid osteoma is more likely to be associated with
intense osteosclerosis when it occurs in: a. Epiphysis
of long bones.
b. Diaphysis of long bones in growing adolescents. c. Both a and b. d. Neither a or b. 2. Computed tomography is most helpful:
a. When the lesion is deep-seated. b. In lesions of the cartex of the diaphysis of long bones. C. In anatomic regions where curvilinear and overlapping bony surfaces exist. d. a and c. 3. Osteoid osteoma of the spine commonly occurs in: a. The body of the vertebra. b. The neural arch. c. Equally in a and b. d. Neither a or b. 4. Persistence or recurrence of pain following osteoid osteoma may be due to: a. Failure of surgery to resect the nidus.
b. Emergence of a new nidus. c. Both a and b. d. Neither a or b.
surgery for
COMPUTED
TOMOGRAPHY
OF COMPUTED
KEY WORDS:
Computed tomography; Osteoid osteoma; Acetabulum; Knee; Spine
Osteoid osteoma is a benign tumor of bone. It usually presents with skeletal pain that is often worse at night, and may be relieved substantially with aspirin. In its classic form, the radiographic diagnosis presents no significant problem when a radiolucent nidus surrounded by a zone of osteosclerosis is demonstrated. In most patients, this is usually achieved fairly easily with conventional radiography when the lesion is located in the metaphysis or diaphysis of the long bones of the extremities. However, when osteoid osteoma occurs in anatomic regions containing curvilinear and overlapping bony surfaces-such as the spine and pelvis-it may not be possible to visualize the osteoid osteoma on conventional radiography and tomography studies. Diagnosis of osteoid osteoma in this group of patients
From the Department of Radiology, New York University Medical Center, New York, New York. Address reprint requests to: Hossein Firooznia, MD, Department of Radiology, New York University Medical Center, 560 First Avenue, New York, New York 10016. Received November 1984. 0 1985 by Elsevier Science Publishing Co., Inc 52 Vanderbilt Ave., New York, NY 10017 0149-936X/851$3.30
1985: 9265-268
265
OF OSTEOID OSTEOMA
HOSSEIN FIROOZNIA, MD, MAHVASH AND CORNELIA GOLIMBU, MD
Computed tomography revealed a radiolucent nidus with Q surrounding zone of osteosclerosis in 17 patients with osteoid osteoma. Plain films did not reveal any abnormality in 5 patients. COnVentiOnQl tomography was negative in 3 patients. Computed tomography is the modality of choice for detection of osteoid osteoma when the lesion is deep-seated or when it occurs in complex anatomic regions with curvilinear and overlapping surfaces, such QS acetabulum, knee, and spine.
TOMOGRAPHY
RAFII,
MD,
may be delayed for several months, possibly leading to inappropriate medical and surgical treatment. Computed tomography (CT) is particularly useful in this group of patients. It provides information that leads to a timely diagnosis and facilitates surgical resection. MATERIALS
AND METHODS
There were 17 patients (5 female, 12 male) ranging in age from 8 to 26 years (mean age, 21 years). Diagnosis of osteoid osteoma was verified histologically in 16 patients. One patient, with a clinical and radiographic diagnosis of osteoid osteoma, but without histologic verification, is being followed. The lesion occurred in the following locations: metaphysis or diaphysis of long bones, 12 patients; spine, 2 patients; acetabulum, 2 patients: and knee, 1 patient. Conventional radiography and CT studies were performed in 17 patients, conventional tomography in 3 patients, and radionuclide (“gmTc-MDP) bone scanning in 6 patients. The CT studies were performed on a GE 8800 CT/T or GE 9800 CT/T units (14 patients) or a Phillips Tomoscan 310 unit (3 patients). The CT slices were 3 to 5 mm thick and spaced consecutively. Intravenous contrast medium consisting of a 30% solution of diatrizoate meglumine (Reno-M-DIP, Squibb, Princeton, N.J.), in the form of a drip infusion, 2 mL per pound of body weight, was utilized in 4 patients. Conventional tomography was performed with a Phillips Polytome unit, utiizing hypocycloidal motion. The tomography cuts were obtained at !&mm intervals. RESULTS Conventional radiography revealed a radiolucent nidus with a surrounding zone of osteosclerosis in 10 patients. In 4 patients in this group, an area of calcification was noted in the nidus. In 5 patients (2 spine, 2 acetabulae, 1 knee) no significant abnor-
266
FIROOZNIA
ET AL.
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL.
9 NO.
3
FIGURE 1. A CT scan through the proximal epiphysis and metaphysis of the nidus tibia. A radiolucent containing calcification is noted in the right tibia. Note surrounding osteosclerosis the nidus.
CT scan FIGURE 2. A through the roof of the acetabulum. The cortex of the
anterior wall of the left acetabulum is displaced anteriorly by a bubble-like expanThere is sion (nidus). marked edema and swelling of the adjacent soft tissues.
malities were detected. In 2 patients (1 proximal fearea of osmur, 1 distal tibia), only a questionable teosclerosis was noted. Bone scanning revealed a focal area of increased tracer uptake in all 6 patients in whom it was performed. Conventional tomography in 3 patients (1 acetabulum, 1 knee, 1 spine) did not reveal the characteristic finding of osteoid osteoma and was not helpful in diagnosis. The CT studies revealed a focal area of radiolucency (nidus) surrounded by various degrees of sclerotic reactive changes in all patients. The sclerotic reaction was less marked in lesions occurring in the trabecular bone of the metaphysis and epiphysis. Calcification within the nidus was noted in 6 lesions. Soft tissue swelling was noted in 2 deep-seated lesions and in 13 lesions that were located at, or close to, the outer cortex of bone. In 2 deep-seated lesions, no soft tissue swelling was noted. Postoperative CT examinations were performed in 3 patients. Computed tomography confirmed ab-
sence of the nidus following surgical resection in 2 patients. In one patient with consistent complaint following surgery, a radiolucent nidus, moderately smaller than the one present prior to surgery, was found. This was thought to be either due to incomplete surgical resection or emergence of a new nidus.
DISCUSSION Osteoid osteomas occur most commonly in the second and third decades of life. They are most commonly located in the long bones of the lower extremities. In our experience, approximately 15% to 20% occur in the remainder of the skeleton. According to Jackson et al. (1) and Price et al. (Z), the spinal column is involved in about 10% of the cases. The lumbar and cervical vertebrae are more frequently involved than the thoracic and sacral vertebrae. The lesion most frequently affects the
TULY 1985
FIGURE 3. (A,B) These CT scans through the femoral neck and intertrochanteric region demonstrate osteosclerosis of the cortex of the left femur anteriorly associated with an intra- and subcortical nidus, calcification in the nidus, and marked swelling of the adjacent soft tissues.
OSTEOID
OSTEOMA
267
A
posterior arch (neural arch), rather than the body of the vertebrae. In the posterior arch, the laminae are most frequently involved, followed by the articulating facets and pedicles (3). The radiographic manifestations of osteoid osteoma consist of a radiolucent nidus, which may contain an area of calcification, and a surrounding zone of reactive osteosclerosis (z-7). The nidus is usually less than 10 mm in diameter (2). In our experience, the intensity and extent of osteosclerosis
in osteoid osteoma-indeed the reactive changes occurring in most other lesions of bone-depend most importantly on the anatomic location of the lesion. That is, the ability of the host bone to react-trabecular bone versus cortical bone-is the most important factor. Thus, an osteoid osteoma occurring in the diaphysis of a long bone, particularly in a growing adolescent, may exhibit a larger and more intense area of osteosclerosis. On the other hand, when an osteoid osteoma arises in the sub-
268
FIROOZNIA
ET AL.
stance of trabecular bone, for example the epiphysis of a long bone, only a mild osteosclerosis may be present. The radiographic diagnosis of osteoid osteoma is dependent upon visualization of the nidus and the surrounding osteosclerosis. This is accomplished by conventional radiography and tomography in most osteoid osteomas of the extremities. In these cases it is possible to project the suspected area of the skeleton free from the adjacent bony surfaces. However, as occurred in five patients in this series, it may not always be possible to visualize the lesion on conventional radiography studies. This may occur when the lesion is in a deep-seated location (Figure l), or when complex curvilinear and overlapping bony surfaces are present, as in acetabulum (Figure 2) or spine. By virtue of its cross-sectional imaging capability, CT overcomes these difficulties and demonstrates these lesions free from overlapping by the adjacent bony structures. Furthermore, CT usually reveals unexpectedly large soft tissue swelling surrounding these lesions (Figures 2 and 3). Intravenous contrast medium administration in four patients in this series led to a more pronounced delineation of the soft tissue swelling. We noticed no significant enhancement of the soft tissue structures within the nidus. Radionuclide bone scanning is a very sensitive but nonspecific procedure that almost always reveals a focal area of increased tracer concentration in patients with osteoid osteoma (8). We believe it should only be used for localization purposes in patients with persistent and diffuse or referred pain, and in patients in whom no definite abnormalities are noted on conventional radiography. The localization of the abnormality is also helpful in developing a tailored CT examination of the involved area. Another application of radionuclide scanning is in intraoperative scintimetry. A complete surgical resection of the nidus can be facilitated through intraoperative bone scintimetry without recourse to block resection (8, 9). This is particularly applicable to regions where relatively extensive block resection is not advisable, such as the spine and articular surfaces. In our experience, CT is most helpful in diagnosis of deep-seated osteoid osteomas and where there is significant overlapping of the bony surfaces. As for other bone lesions CT is particularly helpful in osteoid osteomas situated in the inner portion of the metaphysis and epiphysis of the femur and tibia, and in osteoid osteoma of the spine, scapula, pelvic bones (acetabulum, sacrum), talus, and OS calcis. Also, by demonstrating the precise three-dimensional position of the lesion, CT is helpful in plan-
CT: THE JOURNAL
OF COMPUTED
TOMOGRAPHY
VOL. 9 NO. 3
ning the surgical approach, particularly in deepseated and complex anatomic regions. It is also helpful for assessing the adequacy of the surgical resection and detecting a persistent or recurrent nidus.
REFERENCES 1. Jackson RP, Reckling FW, Mautz FA: Osteoid osteoma and osteoblastoma: Similar histologic lesions histories. Clin Orthop 1977;128:303-13.
with different
natural
2. Price HI, Batnitzky S, Levine E, Rosenthal SJ: The computed tomographic findings in benign disease of the vertebral column. Radiographics 1984;4:2,283-313. 3. Gamba LJ, Martinez S, Appe J, et al.: Computed tomography of axial skeletal osteoid osteoma. AJR 1984;142:769-72. 4. Omojola MF, Cockshott NP, Beatty EG: Osteoid osteoma: An evaluation of diagnostic modalities. Clin Radio1 1981;32:199204. 5. Swee RG, McLeod RA, Beabout tion, diagnosis, and localization.
JW: Osteoid osteoma: DetecRadiology 1979;130:117-23.
6. Wedge JH, Chang ST, McFayden DV: Computed tomography Iocalizationof spinal osteoid osteoma. Spine 1981;6:423-7.
in
7. Jaffe HL: Osteoid osteoma: A benign osteoblastic tumor composed of osteoid and atypical bone. Arch Surg 1935;31:709-28. 8. Ghelman B, Thompson FM, Arnold WD: Intra-operative radioactive localization of osteoid osteoma. J Bone Joint Surg 1981;63A:8267. 9. O’Brien TM, Murray TE, Malone LA, et al.: Osteoid osteoma: excision with scintimetric guidance. Radiology 1984;153:543-4.
CONTINUING MEDICAL EDUCATION QUESTIONS 1. Osteoid osteoma is more likely to be associated with
intense osteosclerosis when it occurs in: a. Epiphysis
of long bones.
b. Diaphysis of long bones in growing adolescents. c. Both a and b. d. Neither a or b. 2. Computed tomography is most helpful:
a. When the lesion is deep-seated. b. In lesions of the cartex of the diaphysis of long bones. C. In anatomic regions where curvilinear and overlapping bony surfaces exist. d. a and c. 3. Osteoid osteoma of the spine commonly occurs in: a. The body of the vertebra. b. The neural arch. c. Equally in a and b. d. Neither a or b. 4. Persistence or recurrence of pain following osteoid osteoma may be due to: a. Failure of surgery to resect the nidus.
b. Emergence of a new nidus. c. Both a and b. d. Neither a or b.
surgery for