Particular imaging features and customized thermal ... - Springer Link

Skeletal Radiol (2011) 40:1523–1530 DOI 10.1007/s00256-011-1133-3

SCIENTIFIC ARTICLE

Particular imaging features and customized thermal ablation treatment for intramedullary osteoid osteoma in pediatric patients Piergiorgio Falappa & Maria Carmen Garganese & Alessandro Crocoli & Renato Maria Toniolo & Antonio Lembo & Fabio Marconi & Andrea Campana & Rita De Vito & Gianclaudio Ciofetta & Antonio Leone

Received: 28 October 2010 / Revised: 21 January 2011 / Accepted: 13 February 2011 / Published online: 15 March 2011 # ISS 2011

Abstract Objective To report on the particular imaging features and high success rate of cold mode radio-frequency thermal ablation (RFTA) as the treatment of choice for intramedullary osteoid osteoma.

P. Falappa (*) : A. Crocoli : F. Marconi Vascular and Interventional Radiology Unit, Pediatric Hospital Bambino Gesù, Piazza S. Onofrio 4, 00165 Rome, Italy e-mail: [email protected] M. C. Garganese : G. Ciofetta Nuclear Medicine Unit, Pediatric Hospital Bambino Gesù, Piazza S. Onofrio 4, 00165 Rome, Italy R. M. Toniolo : A. Lembo Traumatology Unit, Pediatric Hospital Bambino Gesù, Piazza S. Onofrio 4, 00165 Rome, Italy A. Campana Rheumatology Unit, Pediatric Hospital Bambino Gesù, Piazza S. Onofrio 4, 00165 Rome, Italy R. De Vito Pathology Unit, Pediatric Hospital Bambino Gesù, Piazza S. Onofrio 4, 00165 Rome, Italy A. Leone Department of Bioimaging and Radiological Sciences, Catholic University, School of Medicine, Largo A. Gemelli, 1 00168 Rome, Italy

Materials and methods The study population consisted of 51 patients (39 males, 12 females; mean age 7.2 years; 11 patients under 6 years of age, including 7 males and 4 females) who underwent RFTA for osteoid osteoma and were retrospectively observed. The affected sites were the tibia (n=22, 43%), femur (n=13, 25%), pelvis (n=5, 10%), anklebone (n=3, 6%), humerus (n=2, 4%), sacrum (n=2, 4%), heel, radium, patella ,and rib (n=1, 2%), respectively. Three patients had tibial intramedullary osteoid osteoma (14% of the tibial lesions, 6% of all cases). Cold mode RFTA was performed for these three patients to obtain a large ablation area without positioning two probes. The noncooled mode was used to treat cortical and subperiosteal lesions. Results Following RFTA, all patients were pain-free and in good clinical condition. In the intramedullary osteoid osteoma group, no recurrences were observed during the 24-month follow-up period, but one patient, who was affected by cortical osteoid osteoma, required two RFTA treatments to heal completely. Conclusion Children less than 6 years of age with recurrent nocturnal pain and limb swelling should be investigated for intramedullary osteoid osteoma. Once confirmed, CT-guided RFTA should be the first treatment for intramedullary osteoid osteomas because of the high success rate and reduced invasivity, especially with cold mode RFTA. The outcome is related to the disappearance of pain, and the efficacy may be checked shortly after treatment with MR imaging to evaluate the absence of lesion in the ablation area. Keywords Intramedullary osteoid osteoma . Osteoid osteoma . Treatment . Radio-frequency thermal ablation

1524

Introduction In 1966, Edeiken et al. [1] categorized three types of osteoid osteoma based on radiographic localization of the nidus: cortical (defined as located within the cortex), subperiosteal (defined as located on the external aspect of the cortex, surrounded by periosteal reaction), and intramedullary (defined as located within the medullary bone). Intramedullary (also referred to as cancellous) osteoid osteoma is relatively infrequent. To our knowledge, only four cases have been illustrated in the English literature [2– 5], and another three cases in the French literature [6, 7]. Kaiser et al. [8] and Klein et al. [9] reported but did not illustrate 2/38 and 6/67 intramedullary osteoid osteomas, respectively. The intramedullary lesion consistently shows little or no reactive bone formation about the nidus. This gives the lesion a different overall appearance than the more common cortical lesion, in that it does not appear as sclerotic [10]. Until recently, surgical excision was the primary treatment, but less invasive techniques have recently been developed to overcome the problems caused by the possibly difficult surgical access and to minimize the risk of post-operative complications, which may cause prolonged bed confinement. In the last few decades, the use of several minimally invasive treatments (e.g., drill trepanation with or without ethanol injection, cryoablation, and laser photocoagulation) has been reported [11, 12]. More recently, computed tomography (CT)-guided percutaneous radio-frequency thermal ablation (RFTA) proved to be less invasive than surgery and maintained similar success rates [12–15]. Rosenthal et al. [16], reporting their experience with technical success, complications, and long-term clinical success of CT-guided percutaneous RFTA in a group of 263 patients with suspected osteoid osteoma, concluded that RFTA can be considered the treatment of choice for most osteoid osteomas located in the appendicular skeleton and pelvis. Vanderschueren et al. [17], retrospectively evaluating 95 consecutive patients with osteoid osteoma treated with RFTA, suggested that young age is a risk factor for treatment failure that is difficult to explain. Rosenthal et al. [16] reported no statistically significant relation between patient age and clinical outcome, although patients with successful results were somewhat younger and had slightly smaller lesions. However, data are scant in the literature about RFTA treatment for pediatric patients affected by intramedullary osteoid osteoma. In their study of 23 children with osteoid osteoma, Donkol et al. [18] assessed the safety and efficacy of CT-guided RFTA. The authors achieved technical success in 21 children. Inaccurate needle placement and development of hyperthermia were respectively found to be the cause for treatment failure in two children. Pain recurrence was observed in two patients, and hyperthermia in

Skeletal Radiol (2011) 40:1523–1530

other two. Nevertheless, CT-guided RFTA was shown to be an effective and safe minimally invasive procedure for the treatment of osteoid osteoma in children. The efficacy and feasibility of RFTA have also been shown in infants younger than 1 year, as recently reported by Ekstrom et al. [2] and Virayavanich and co-workers [4]. In this study, we report on the particular imaging features and high success rate of cold mode radio-frequency thermal ablation (RFTA) as the treatment of choice for intramedullary osteoid osteoma.

Materials and methods We retrospectively studied 51 patients (39 males, 12 females; mean age 7.2 years; 11 patients under 6 years of age including 7 males and 4 females) who underwent RFTA for osteoid osteoma from April 2004 to January 2009. Informed parental consent was previously obtained for each patient. The affected sites were the tibia (n=22, 43%), femur (n=13, 25%), pelvis (n=5, 10%), anklebone (n=3, 6%), humerus (n=2, 4%), sacrum (n=2, 4%), heel, radium, patella, and rib (n=1, 2%), respectively. Three patients had tibial intramedullary osteoid osteoma (14% of the tibial lesions, 6% of all cases). Cold mode RFTA was performed for these three patients. The noncooled mode was used to treat cortical and subperiosteal lesions. Computed tomography (CT)-guided percutaneous RFTA was performed by an interventional radiologist under general anesthesia in an aseptic CT room. A CT-guided needle biopsy was performed first (11 G needle, Trap DrillHS Hospital Service; Aprilia, LT, Italy). Next, the RFTA was done under CT guidance using the Cool-Tip (7–10 mm exposed tip probe) RF ablation system® (Covidien; Boulder, CO, USA). The “cool-mode” was performed by flushing the single probe with cold water, and RFTA was delivered for 6 min with an output of 10 W. Since there was impedance control, no target temperature was planned prior to performing the procedure, and the different final temperatures obtained were 47, 55, and 40°C, respectively. All cortical and subperiosteal osteoid osteomas underwent the same procedure using a noncooled RF ablation system with target temperature of 90°C delivered in 6 min and developed RF output of 3–4 W. Intramedullary osteoid osteoma group This group comprised three patients: one female and two males, aged 16 months to 6 years (Table 1). All of these patients were admitted to our hospital for tibial swelling, severe recurrent nocturnal pain, and limping. The clinical conditions were otherwise normal, and the blood tests, including inflammation markers, were all within the normal


1525

Table 1 Intramedullary osteoid osteoma group. Size of the necrosis areas at post-RFTA MR imaging checks Patient no./agea (months)/sex

Measured size at 1 m follow-up (mm)




1/37/F 2/70/M 3/16/M

18×14×12 15×10×9 16×12×10

11×8×6 8×6×4 10×5×4

N.V. N.V. N.V.

N.D. N.D. N.D.

N.V. Not valuable, N.D. not detectable a

Age at the time of RFTA

limits. Radiographic examination, CT scans, MR imaging, and three-phase bone scintigraphy were performed on all three patients. The patients were scheduled for RFTA, and in the same session before the procedure, the CT-guided bone biopsy was acquired. Anteroposterior and lateral radiographs of the tibia were performed at 12 months after RFTA on all of these patients. They also underwent MR examination at 1, 3, 12, and 18 months after RFTA. All MR examinations were performed on a 1.5-Tesla unit (Intera, Philips Medical Systems, Best, The Netherlands) utilizing T1-weighted spin echo (SE), and spectral presaturation inversion recovery (SPIR) sequences in the axial as well as coronal or sagittal oblique planes. Additional sagittal T2-weighted fast field echo (FFE) and post-gadolinium coronal T1-weighted fat-suppressed sequences were obtained for one patient.

Fig. 1 A 3-year-old girl with swelling of the distal left tibia associated with hobbling and complaining of persistent nocturnal pain. a Lateral radiograph and b sagittal multiplanar CT reconstruction show a tibial cortical sclerosis (white arrows) associated with an elongated intramedullary lytic lesion with a thin sclerotic rim (Ø 1.3 x 0.6 x 0.6 cm) (black arrow). c Subsequent threephase bone scintigraphy shows a focal area with an intense uptake in the distal inner diaphysis of the left tibia (black arrow). d Axial CT scan showing the cooled probe tip inserted into the intramedullary nidus. e Coronal T2weighted spectral presaturation with inversion recovery (SPIR) MR image and f corresponding T1-weighted spin echo (SE) image, performed 18 months after RF ablation, show the absence of cortical sclerosis and edema with no evidence of intramedullary nidus (arrow)

Figures 1, 2, 3, 4 show the three cases with complete pre- and post-operationimaging.

Results In this study, we observed 51 patients (39 males and 12 females, mean age 12.2 years, range from 16 months to 19 years). The age range distribution of patients was 11 younger than 6 years (7 males and 4 females) and 40 older than 6 years. The localizations of the lesions were as follows: 22 (43%) in the tibia, 13 (25%) in the femur, 5 (10%) in the pelvis, 3 (6%) in the anklebone, 2 (4%) in the humerus, 2 (4%) in the sacrum, 1 (2%) in the heel, 1 (2%) in the radium, 1 (2%) in the patella, and 1 (2%) in the rib. Of all the osteoid osteoma patients, 42 (82%) were cortical, 6

1526


Fig. 2 A 6-year-old boy with distal left tibia swelling. The child was limping and complained of severe nocturnal pain. a Anteroposterior radiograph and b coronal multiplanar CT reconstruction show an intramedullary lytic lesion with a sclerotic rim (Ø 1.2 x 0.4 x 0.5 cm) (arrow) associated with very thick cortical bone sclerosis (arrowhead). c Axial CT scan showing the cooled probe tip inserted into the intramedullary nidus. d Histological section of the excised biopsy specimen shows the central nidus formed of irregular trabeculae of osteoid and immature woven bone. e Sagittal T1-weighted SE MR image, performed 3 months post-treatment, shows the area of necrosis caused by the RFTA with the entire nidus included within the ablation area (arrow). f Anteroposterior radiograph of the tibia, performed 12 months later, shows absence of cortical sclerosis

(12%) were subperiosteal, and 3 were tibial intramedullary (14% of the tibial lesions, 6% of all cases). Mean measurements for subperiosteal and cortical osteoid osteomas were 7.6 x 6.2 x 6.1 mm and 7.3 x 6.8 x 6.1 mm respectively. Specimens were considered diagnostic for osteoid osteoma in 29 out of 48 patients (60.4%). In these cases, intermixture of osteoid, newly formed bone with highly vascular supporting stroma was evident. No post-operative complications were reported, and the mean hospital stay was 4 days. One patient with a cortical osteoid osteoma of the right femur required a supplementary RF treatment to completely heal the lesion. Intramedullary osteoid osteoma group Intramedullary nidus was always found to be larger and more elongated than the round-shaped niduses in cortical or subperiosteal localizations. Measurements of intramedullary osteoid osteoma nidus were 13 x 6 x 6 mm, 12 x 5 x 4 mm, and 13 x 5 x 4 mm respectively. Specimens were diagnostic for osteoid osteoma in two of these three patients (Fig. 2d). No post-operative complications were reported, mean hospital stay was 4 days and no recurrences were observed. MR examinations allowed the detection of temporal marrow signal change after RFTA showing progressive reduction in size of the necrosis areas at 1 and 3 month checks. There was no

detection of the same area 18 months after treatment (Fig. 4, Table 1). Radiographic examinations performed 12 months after RFTA showed a reduction of the cortical sclerosis and mild visualization of the needle tract. Clinical follow-ups after 6, 18, and 24 months were unremarkable.

Discussion Osteoid osteoma is a benign and painful bone-forming tumor that occurs most frequently during childhood and adolescence. Ninety percent of the cases reported are seen before the age of 25; the occurrence is rare under the age of 5 and over the age of 40 [19, 20]. It is typically a small lesion (less than 1.5 cm) and has a specific architecture: an inner part, the so-called “nidus” formed by osteoid tissue, that is surrounded by a sclerotic reactive rim [21]. There is a male prevalence, with most larger series reporting a ratio of male to female patients approximately 1.6:1 to 4:1 [10]. The tumor represents 2.5% of all pediatric neoplasms and 10% of all infantile benign lesions [10, 22, 23]. Osteoid osteoma may occur in virtually any bone, although there is a strong predilection for the long bones of the arms and legs with 50% or more of lesions occurring in the cortex of the femoral or tibial diaphysis [10]. Despite their benign nature and small size, these tumors usually need to be treated because they often cause pain that is described as severe, sharp, and typically, worst at night [18]. The pain mediation is


1527

Fig. 3 A 16-month-old boy with limping and persistent pain in the left tibial diaphysis. Previous imaging examinations (radiographs, CT, and MR imaging) had been performed elsewhere, and the reports suggested left leg osteomyelitis. These images were reviewed. a Coronal T2-weighted SE MR image and b sagittal multiplanar CT reconstruction show an intramedullary lesion (Ø1.3 x 0.4 x 0.5 cm) surrounded by a sclerotic area (arrow), and a very thick cortical bone sclerosis (arrowhead). These findings are suggestive for intramedul-

lary osteoid osteoma, which was confirmed by a three-phase bone scintigraphy (not shown). c Axial CT scan showing the cooled probe tip inserted into the intramedullary nidus. d Sagittal T1-weighted SPIR image and e corresponding coronal fast field echo (FFE) MR images, performed 1 month post-treatment, show the area of necrosis caused by RFTA (arrow). The whole of the nidus was shown to have been included within the ablation area

thought to be caused by the presence of nerve fibers in the reactive zone, both around and inside the nidus [24, 25] as well as the excessive production of prostaglandins, which causes local vasodilatation and inflammatory response

[26]. Nonsteroidal anti-inflammatory drugs can temporarily relieve the tumor-related pain. The frequency of cortical and subperiosteal osteoid osteomas peaks in the second decade, but the frequency

Fig. 4 Same case described in Fig. 3. a Sagittal T1-weighted MR image, obtained 1 month after RFTA, demonstrates ovoidal hypointense area with major axis parallel to medullary canal with a thin edge corresponding to ablation area (arrow). b Sagittal T2-weighted SPIR MR image, performed 3 months after procedure, shows

hyperintense and smaller area as result of treatment (arrow). c, d Sagittal T1-weighted MR images obtained c 12 and d 18 months after RFTA demonstrate progressive reduction (c) and disappearance (d) of previously reported hypointense treated area with normal cortical bone

1528

of the intramedullary forms peaks in the first decade [10]. Although 3–8% of the reported patients are younger than 6 years, the incidence of intramedullary forms seems to be higher in patients younger than 6 years [20], and the long bones of arms and legs are typically involved. In more than 50% of cases, the femoral or tibial diaphysis are involved, which is in agreement with our results (35/51 patients, 68%). According to the literature, the intramedullary localization is rare [7], but we observed it in 3 of 51 cases (6%). Additionally in patients younger than 6 years, the intramedullary localization results were even more frequent (3 of 11 patients, 27%). This suggests that intramedullary localization is more common than has been reported. Of the seven cases of intramedullary osteoid osteomas reported in the literature, four cases were localized in the tibia [5–7], which is similar to the three children in our series. Thus, any child less than 6 years old who presents with recurrent nocturnal pain, tibial swelling, and the normal inflammation markers should be evaluated for the presence of an intramedullary osteoid osteoma, even if a nidus is not clearly detected with the radiographic examination. Regarding the intramedullary localization, there is little data in the literature about this form and its related treatment: two intramedullary lesions were reported in the French literature in 1997 [6, 7]. Similar to our patients, these cases were younger than 3 years (18 months and 30 months), and the lesions were located in the distal tibia. Another case of intramedullary lesion in a patient under 3 years of age was described in 2007 [5]. Lastly, two more cases of intramedullary osteoid osteoma were reported: a 15-year-old child in 1999 [7] and a 17-year-old boy in 1985 [3]. All of the above cases were treated by surgery, but recently, two cases of children younger than 1 year affected by intramedullary osteoid osteoma who were successfully treated with RFTA were described [2, 4]. Both papers reported cases of patients treated with RFTA under 12 months of age. Nevertheless, they showed important differences with our series. Viravanych et al. [4] reported on a patient with osteoid osteoma who was treated with conventional RFTA with noncooled probe. With no success after the first session, the treatment was repeated twice. Ekstrom et al. [2] also described a case of a child who underwent RFTA for osteoid osteoma without mentioning any of the performed technical features. In this respect, the unusual intramedullary localization may also present a diagnostic challenge because the typical radiographic lesion located within the cortex of a long bone, with a central lucent zone (i.e., nidus), and sclerosis of the surrounding bone tissue may be absent [9, 27]. The three cases in our series had an intramedullary osteoid osteoma and a localized cortical sclerotic reaction. However, trabecular sclerosis surrounding the nidus was seen only in two cases. Further information can be obtained using bone


scintigraphy, CT or MR imaging. Bone scintigraphy has 100% sensitivity for osteoid osteoma detection [28]: high focal signal is usually shown on the angiographic and blood-pool images. The late-phase skeletal images show well-localized, focal, and marked uptake. Characteristically, the intense uptake into the nidus is surrounded by a less marked but still high uptake in the reactive bone [29, 30]. This pattern is most commonly observed in the long bone lesions of the appendicular skeleton [31]. CT scans generally show a small, hypodense nidus surrounded by reactive sclerosis [32], when localized in the cortical or subperiosteal bone. MR imaging can barely detect the nidus, and the intramedullary soft tissue changes may produce a misleadingly aggressive appearance [33]. Typically, an intermediate signal is seen on T1-weighted images, and a high-intensity signal is seen on T2-weighted images. A low-intensity signal within the nidus on T2 images suggests calcification. Furthermore, prolonged enhancement within the lesion has been reported for dynamic MR compared with the arterial one [32]. Treatment options for osteoid osteoma include prolonged administration of nonsteroidal anti-inflammatory drug (NSAID) and surgical excision, which was considered an elective treatment in the past decades. However, RFTA has proven to be an effective method for the treatment of many malignant and benign tumors and was also successfully used for the treatment of osteoid osteoma. The first description of this procedure was reported for a fourpatient series in 1992 [34], and since then many series have been mushrooming in literature because of the excellent reported results with high technical and clinical success rates [13–16]. Minimally invasive procedures, high success rate, and low incidence of complications compared to surgical excision are non-negligible factors that define RFTA as the primary treatment for osteoid osteoma in the pediatric population [15, 16, 18]. The choice of noninvasive treatment is always preferred for children and infants [4]. RFTA requires a very short hospitalization and allows the child to return to a normal routine shortly after the procedure. The efficacy of RFTA after long-term follow-up and in pediatric patients has been reported in the literature [12–16, 19]; the success rate can reach 100%, once the operator has become familiar with the technique. However, all of these reports describe the use of a noncooled tip. The novelty of our approach is represented by the choice of a cold probe-tip (7 or 10 mm of diameter) for the selective and very effective treatment of the intramedullary lesions in children. A single cooled RF tip causes a larger ablation area (about twice the length of the exposed probe-tip) compared to the noncooled tip device. Using this method, tissues that were closer to the noncooled probe burned and charred, as a result of high local temperatures. This limited the


thermal effect to a smaller radius of tissue around the probe. To ablate larger lesions, multiple passes were sometimes necessary. As a solution, a novel probe was developed with a cooling mechanism consisting of continuous water circulation through the tip. Thus, the local temperature both at and around the tip is kept at circulating water temperature; the adjacent tissue is heated but not burned, allowing ablation of tissue in a larger radius than with the noncooled RF tips. For this reason, gross lesions with an elongated shape may be easily included within the radiofrequency ablation area [15]. In our series, the “cool-mode” was used by flushing the probe with cold water to attain an adequately large ablation area. We considered this approach easier and less invasive than positioning the probe twice for a complete treatment of a large and elongated lesion, as the intramedullary osteoid osteoma appears to be [15]. Furthermore, the cooled-tip probe was highly effective and safe for the treatment of pediatric intramedullary osteoid osteoma, theoretically with no adverse events. Treatment efficacy may be confirmed by MR imaging, as temporal bone marrow signal changes due to therapy can determine the extent and adequacy of the post-RFTA necrosis area and, at the same time, allow the user to verify the correct probe position in relation to the complete nidus inclusion within the ablated area [35–38]. Furthermore, we found that, compared to noncooled devices, tip-cooled probes deliver larger zones of marrow MR imaging signal alterations, as previously reported by Cantwell et al. [36]. Another advantage of RFTA is the absence of cutaneous scars [15]; indeed, in our patients we never recorded hyperthermia, during or after RFTA. In conclusion, based on our results, we suggest that a child with persistent nocturnal tibial pain and local swelling but normal inflammation markers values should be investigated with radiography for suspected osteoid osteoma. Whenever radiological cortical sclerosis is present, a bone scintigraphy should be performed to confirm the diagnosis. Otherwise, patients with classic clinical symptoms should be evaluated by CT scans and scheduled for biopsy. CT-guided RFTA can certainly be the first-line treatment in pediatric patients because of its low invasivity and low complication rate. When used in the cool mode, its localization was very effective in the intramedullary osteoid osteoma. Successful treatment is confirmed by pain disappearance and MR imaging. Conflict of interest The authors declare that there is no conflict of interest.

References 1. Edeiken J, De Palma AF, Hodes PJ. Osteoid osteoma (roentgenographic emphasis). Clin Orthop Relat Res. 1966;49:201–6.

1529 2. Ekstrom W, Soderlund V, Brosjo O. Osteoid osteoma in a 1-yearold boy—a case report. Acta Orthop. 2006;77(4):686–8. 3. Steiner M, Grana WA. Intramedullary osteoid osteoma of lateral femoral condyle. Orthopedics. 1985;8(9):1176–8. 4. Virayavanich W, Singh R, O'Donnell RJ, Horvai AE, Goldsby RE, Link TM. Osteoid osteoma of the femur in a 7-month-old infant treated with radiofrequency ablation. Skeletal Radiol. 2010;39(11):1145–9. 5. Halanski MA, Mann DC. Case report: unusual tibia intramedullary osteoid osteoma in a two-year-old. Iowa Orthop J. 2007;25:66–8. 6. Jawish R, Kassab F, Kairallah S, Rizk R. Osteoid osteoma of the intramedullary diaphyse in children. Rev Chir Orthop Reparatrice Appar Mot. 1997;83(1):74–7. 7. Essadki B, Moujtahid M, Zryouil B. Medullary osteoid osteoma. A pathogenic discussion. Rev Chir Orthop Reparatrice Appar Mot. 1999;85(5):491–3. 8. Kayser F, Resnick D, Haghighi P, et al. Evidence of the subperiosteal origin of osteoid osteomas in tubular bones: analysis by CT and MR imaging. AJR Am J Roentgenol. 1998;170:609–14. 9. Klein MH, Shankman S. Osteoid osteoma. Radiologic and pathological correlation. Skeletal Radiol. 1992;21:23–31. 10. Kransdorf MJ, Murphey MD. Osseous tumors. In: Davies AM, Sundaram M, James SL, editors. Imaging of bone tumors and tumor-like lesions. Techniques and applications. Berlin Heidelberg: Springer-Verlag; 2009. p. 251–304. 11. Sans N, Galy-Fourcade D, Assoun J, et al. Osteoid osteoma: CTguided percutaneous resection and follow-up in 38 patients. Radiology. 1999;212:687–92. 12. Woertler K, Vestring T, Boettner F, Winkelmann W, Heindel W, Lindner N. Osteoid osteoma: CT-guided percutaneous radiofrequency ablation and follow-up in 47 patients. J Vasc Interv Radiol. 2001;12:717–22. 13. Mahnken AH, Tacke JA, Wildberger JE, Günter RW. Radiofrequency ablation of osteoid osteoma: initial results with a bipolar ablation device. J Vasc Interv Radiol. 2006;17:1465–70. 14. Rosenthal DI, Hornicek FJ, Wolfe MW, Jennings LC, Gebhardt MC, Mankin HJ. Percutaneous radiofrequency coagulation of osteoid osteoma compared with operative treatment. J Bone Joint Surg Am. 1998;80:815–21. 15. Peyser A, Applbaum Y, Simanovsky N, Safran O, Lamdan R. CTguided radiofrequency ablation of pediatric osteoid osteoma utilizing a water-cooled tip. Am Surg Oncol. 2009;16:2856–61. 16. Rosenthal DI, Hornicek FJ, Torriani M, Gebhardt MC, Mankin HJ. Osteoid osteoma: percutaneous treatment with radiofrequency energy. Radiology. 2003;229(1):171–5. 17. Vanderschueren GM, Taminiau AH, Obermann WR, van den Berg-Huysmans AA, Bloem JL. Osteoid osteoma: factors for increased risk of unsuccessful thermal coagulation. Radiology. 2004;233:757–62. 18. Donkol RH, Al-Nammi A, Moghazi K. Efficacy of percutaneous radiofrequency ablation of osteoid osteoma in children. Pediatr Radiol. 2008;38:180–5. 19. Mirra JM. Osseous tumors of intramedullary origin. In: Mirra JM, editor. Bone tumors: clinical, radiologic, and pathologic correlations. Philadelphia: Lea & Febiger; 1989. p. 248–438. 20. Chai JW, Hong SH, Choi JY, et al. Radiologic diagnosis of osteoid osteoma: from simple to challenging finding. Radiographics. 2010;30(3):737–49. Erratum in: Radiographics. 2010; 30(4):1156. 21. Ghanem I. The management of osteoid osteoma: updated and controversies. Curr Opin Ped. 2006;18:36–41. 22. Orlowski JP, Mercer RD. Osteoid osteoma, including pronounced overgrowth and deformity of bones. Clin Orthop. 1975;110:223– 38. 23. Unni KK. Osteoid osteoma. In: Unni KK, editor. Dahlin’s bone tumors. General aspects and data on 11,087 cases. 5th ed. Philadelphia: Lippincott-Raven; 1996. p. 117–20.

1530 24. Hasegawa T, Hirose T, Sakamoto R, Seki K, Ikata T, Hizawa K. Mechanism of pain in osteoid osteomas: an immunohistochemical study. Histopathology. 1993;22:487–91. 25. Greco F, Tamburrelli F, Laudati A, La Cara A, Di Trapani G. Nerve fibres in osteoid osteoma. Ital J Orthop Traumatol. 1988;14:91–4. 26. Ciabattoni G, Tamburrelli F, Greco F. Increased prostacyclin biosynthesis in patients with osteoid osteoma. Eicosanoids. 1991;4:165–7. 27. Greenspan A. Benign bone-forming lesions—osteoma, osteoid osteoma, and osteoblastoma- clinical, imaging, pathological, and differential considerations. Skeletal Radiol. 1993;22:485–500. 28. Lisbona R, Rosenthall L. Role of radionuclide imaging in osteoid osteoma. AJR. 1979;132(1):77–80. 29. Helms CA. Osteoid osteoma. The double density sing. Clin Orthop Relat Res. 1987;222:167–73. 30. Helms CA, Hettner RS, Vogler 3rd JB. Osteoid osteoma radionuclide diagnosis. Radiology. 1984;151(3):779–84. 31. Roach PJ, Connolly LP, Zurakowski D, Treves ST. Osteoid osteoma: comparative utility of high-resolution planar and pinhole magnification scintigraphy. Pediatr Radiol. 1996;26(3):222–5.

Skeletal Radiol (2011) 40:1523–1530 32. Azouz EM. Magnetic resonance imaging of benign bone lesions: cysts and tumors. Top Magn Reson Imaging. 2002;13:219–29. 33. Assoun J, Richardi G, Railhac JJ, et al. Osteoid osteoma—MRimaging versus CT. Radiology. 1994;191:217–23. 34. Rosenthal D, Alexender A, Rosemberg A, Springfield D. Ablation of osteoid osteoma with a percutaneously placed electrode: a new procedure. Radiology. 1992;183:29–33. 35. Aschoff AJ, Merkle EM, Emancipator SN, Petersilge CA, Duerk JL, Lewin JS. Femur: MR imaging-guided radio-frequency ablation in a porcine model—feasibility study. Radiology. 2002;225(2):471–8. 36. Cantwell CP, Kerr J, O’Byrne J, Eustache S. MRI features after radiofrequency ablation of osteoid osteoma with cooled probes and impedance-control energy delivery. AJR Am J Roentgenol. 2006;186:1220–7. 37. Cioni R, Armillota M, Bargellini I, Zampa V, Cappelli C, Vagli P, et al. CT-guided ablation of osteoid osteoma: long term results. Eur Radiol. 2004;14:1203–8. 38. Zampa V, Bargellini I, Ortori S, Faggioni L, Cioni R, Bartolozzi C. Osteoid osteoma in atypical locations: the added value of dynamic gadolinium-enhanced MR imaging. Eur Radiol. 2009;71:527–35.