Neonatal osteoblastic tumor with a novel PTBP1::FOSB fusion.

Congenital/neonatal bone neoplasms are extremely rare. We present the case of a patient with a neonatal bone tumor of the fibula that had osteoblastic differentiation and a novel PTBP1::FOSB fusion. FOSB fusions are described in several different tumor types, including osteoid osteoma and osteoblastoma; however, these tumors typically present in the second or third decade of life, with case reports as young as 4 months of age. Our case expands the spectrum of congenital/neonatal bone lesions. The initial radiologic, histologic, and molecular findings supported the decision for close clinical follow-up rather than more aggressive intervention. Since the time of diagnosis, this tumor has undergone radiologic regression without treatment.

Comparative Analysis of Percutaneous Excision and Radiofrequency Ablation for Osteoid Osteoma.

BACKGROUND This retrospective study aims to compare the efficacy of computed tomography-guided percutaneous excision and radiofrequency ablation in the treatment of osteoid osteoma. MATERIAL AND METHODS We evaluated 40 patients with osteoid osteoma who underwent either percutaneous excision or radiofrequency ablation between 2012 and 2015. The cohort consisted of 10 female and 30 male patients, with a mean age of 15.1 years (range: 4-27 years) and a mean follow-up time of 19.02 months (range: 11-39 months). Percutaneous excision was performed in 20 patients, while radiofrequency ablation was performed in the remaining 20 patients. RESULTS The success rates of percutaneous excision and radiofrequency ablation were comparable, with unsuccessful outcomes observed in 10% and 5% of patients, respectively. The reasons for failure in the percutaneous excision group were attributed to a marking error and incomplete excision of the wide-based nidus. Complications were limited to pathological fracture (n=1) and deep infection (n=1) in the percutaneous excision group, while no complications were encountered in the radiofrequency ablation group. CONCLUSIONS Both percutaneous excision and radiofrequency ablation demonstrate high success rates in treating osteoid osteoma. However, radiofrequency ablation offers the advantage of a quicker return to daily activities without the need for activity restrictions or splints. While being a more cost-effective option, percutaneous excision should be considered cautiously to minimize potential complications.

Diagnosis and Management of Craniofacial Osteomas.

IMPORTANCE: Osteoid osteomas are benign bony overgrowths that can occur in any region of the body. However, they have a predilection to occur in the craniofacial region. Because of the rarity of this entity, there is a lack of literature detailing the management and prognosis of craniofacial osteoid osteomas. OBSERVATIONS: Craniofacial osteomas have a predilection to involve the paranasal sinuses, but can also be found within the jaw, skull base, and facial bones. Because of their slow-growing nature, craniofacial osteomas are often incidentally discovered on routine imaging or after they compress nearby structures or distort nearby anatomy. Osteoid osteomas of the face can be treated with resection via various approaches. Recent advancements describe minimally invasive endoscopic techniques and adjuvant therapy with radiofrequency ablation guided by cone biopsy computed tomography. Osteoid osteomas have an excellent prognosis with complete resection. They demonstrate a low incidence of recurrence when compared with other osteoblastic lesions of the craniofacial structures. CONCLUSIONS AND RELEVANCE: Craniofacial osteoid osteomas remain a developing topic within the field of craniofacial surgery. Their removal may be trending toward minimally invasive techniques. However, all treatment modalities appear to result in improved cosmetic outcomes and low recurrence rates.

Computed tomography guided radiofrequency ablation of osteoid osteoma in children: a single center's experience.

OBJECTIVE: To report a single center's experience evaluating the efficacy and safety of computed tomography-guided radiofrequency ablation for the treatment of osteoid osteoma in children. MATERIALS AND METHODS: Institutional database research identified 33 symptomatic patients (≤ 18 years of age; male/female ratio: 21/12, mean age 13.09 ± 3.66) with osteoid osteoma who were treated by CT-guided RFA. Technical and clinical success as well as complication rates were recorded. The duration of the procedure, the number of computed tomography scans and the results of the biopsy were assessed. Pain, prior, the following morning and 1 week, 1/6/12 months after the procedure were compared by means of a numeric visual scale (NVS) questionnaire. RESULTS: Mean lesion size was 8.28 ± 4.24 mm. Mean follow-up was 23.33 ± 17.61 months (range 12-62). Mean pain score prior to radiofrequency ablation was 9.06 ± 0.80 NVS units. On week 1 and 1/6/12 months, all patients were pain-free reporting 0 NVS units (p < 0.05). The mean procedure time was 54 min (range 51-59) and a mean of 7 CT scans were performed during the ablation session. RF electrode was successfully placed in the center of the nidus in all cases. In our study, none of our patient experienced recurrence of the pain, nor complications. CONCLUSION: The present study demonstrates that percutaneous CT-guided radiofrequency ablation constitutes a safe and effective technique for osteoid osteoma treatment in children.

Osteoid Osteoma of the Atlas in a Boy: Clinical and Imaging Features-A Case Report and Review of the Literature.

Osteoid osteoma is a benign osteoblastic tumor, quite uncommon in the spine. We report a case of an osteoid osteoma involving the atlas in a 6-year-old boy, who presented with suboccipital pain and torticollis. Initial radiological findings were ambiguous as magnetic resonance imaging showed mainly edema of upper cervical soft tissues. The subsequent computed tomography depicted a lesion of left lamina of C1. As conservative treatment failed, the lesion was surgically resected and the patient became pain free. To our knowledge, this is the first case of osteoid osteoma involving the atlas associated with abnormal soft tissue reaction reported in literature.

[Osteoid-forming bone tumors : Morphology and current translational cell biology]. / Osteoidbildende Knochentumoren : Morphologie und aktuelle translationale Zellbiologie.

Osteoid osteoma and osteoblastoma are the most important benign osteoid-forming tumors. They grow slowly and are well differentiated. Histologically, the tumor cells show no atypia and no increased mitoses. In typical cases, they can be clearly diagnosed. However, the rare cases on the dividing line between osteoblastoma and osteosarcoma are extremely problematic. In these cases, molecular genetic investigations should contribute to finding the correct diagnosis in the future.Juvenile highly malignant osteosarcoma is the most important malignant osteoid-forming tumor. About 40 years ago, neoadjuvant chemotherapy was introduced for the mostly young patients. This therapy highly significantly improved prognosis. However, a plateau phase was quickly reached and the last several decades have seen no further progress in conventional therapeutic approaches. There is no doubt that further progress can only be achieved on the basis of new molecular genetic and cell biological findings. The target-therapeutic strategies derived from these findings will be discussed in this review.The rare parosteal osteosarcoma and the even rarer periosteal osteosarcoma are mostly not highly malignant tumors that are located on the surface of bone. The parosteal osteosarcoma is usually G1 and the periosteal osteosarcoma G2. Occasionally, the differential diagnosis between a parosteal osteosarcoma and a fibrous dysplasia is difficult. In such rare cases, the detection of GNAS mutations in fibrous dysplasia can prove useful. In contrast to chondromas and chondrosarcomas, periosteal osteosarcomas do not contain IDH1 and IDH2 mutations.

Factors Associated with Osteoid Osteoma Recurrence after CT-Guided Radiofrequency Ablation.

PURPOSE: To identify clinical and imaging variables associated with symptomatic recurrence of osteoid osteomas (OOs) treated with computerized tomography (CT)-guided radiofrequency (RF) ablation. MATERIALS AND METHODS: Seventy-one patients treated with the use of CT-guided RF ablation for OO at a single institution from July 2005 to May 2018 were included in this retrospective cohort analysis. Clinical data, including patient age, sex, race, and clinical outcomes, were collected from institutional electronic health records and telephone follow-up. Imaging variables regarding tumor characteristics were gathered from imaging reports and a blinded review of preprocedural images by an experienced musculoskeletal radiologist. Logistic regression, Cox proportional hazards, and Kaplan-Meier analyses were used to identify variables that are significantly associated with symptomatic recurrence, which was defined as pain occurring > 2 weeks after RF ablation. RESULTS: Ten patients (14.1%) experienced symptomatic recurrence at a median of 21.5 months after RF ablation. Univariable logistic regression classified young age (≤ 13 years), female sex, maximum tumor length, and "eccentricity index" (EI) ≥ 3 as predictive variables significantly associated with symptomatic recurrence. Multivariable logistic regression identified female sex and EI ≥ 3 to be significant predictors for symptomatic recurrence. A multivariable proportional hazards Cox regression of time to recurrence revealed EI ≥ 3 to be the only significant predictor of symptomatic recurrence. CONCLUSIONS: Female patients with OOs with an EI ≥ 3 have a greater risk of symptomatic recurrence following RF ablation. The EI is a useful tool to identify OOs with elongated 3-dimensional morphology, which may warrant more extensive ablation.

Unusual localization and presentation of osteoid osteoma mimicking juvenile spondyloarthritis: a case report.

BACKGROUND: Osteoid osteoma is a painful benign skeletal tumour of unknown aetiology. Most often it occurs in the long bones of extremities and responds well to nonsteroidal anti-inflammatory medications. However, unusual localization and atypical presentation of this tumour might present a diagnostic challenge, especially if symptoms mimic that indicative of juvenile spondyloarthritis. CASE PRESENTATION: A misdiagnosed ten-and-a-half-year-old girl with osteoid osteoma involving the distal phalanx of a little finger is presented. Her initial symptoms were pain and swelling of the little finger resembling dactylitis, while various imaging modalities showed signs of tenosynovitis, indicating a possible development of juvenile spondyloarthritis. Several trials of different non-steroid anti-inflammatory drugs gave no satisfactory results and ultrasound guided triamcinolone-hexacetonide injection provided only a short relief. Finally, almost three years after initial presentation, persistent clinical symptoms warranted repeated imaging that raised suspicion of an osteoid osteoma. Directed treatment with surgical intervention led to almost immediate and complete resolution of her symptoms. CONCLUSIONS: Osteoid osteoma should be suspected in case of a tender swelling of a digit in children and adolescents, regardless of initial imaging findings and clinical presentation. Early diagnosis and treatment of this benign condition can have a substantial impact on quality of life of patients and their families and protect them from many unnecessary diagnostic procedures and treatment.

Multicentric, multifocal, and recurrent osteoid osteoma of the hip: first case report.

BACKGROUND: Osteoid osteoma is a benign bone-forming tumour, which very unfrequently has multifocal or multicentric presentation. We report the first known case of a multicentric, multifocal and recurrent osteoid osteoma treated using radiofrequency ablation. CASE PRESENTATION: A 39-year-old man with two-year history of left hip pain was admitted at our Institution. The pain was more intense during the night and partially relieved by salicylates. Pelvis CT demonstrated two lytic lesions (8 and 7 mm, respectively) with surrounding sclerotic reactive bone, both with a central focal area of high attenuation, located in the femoral neck and along the anterior portion of the acetabulum, respectively. Both lesions had clinical and imaging findings consistent with multicentric osteoid osteoma. Thus, the two lesions were biopsied - with pathologic confirmation of osteoid osteoma - and treated using radiofrequency ablation. Hip pain decreased but did not disappear, actually increasing a few months after treatment. CT and MRI were performed showing a smaller lesion (5 mm) with the same imaging features, surrounded by marrow oedema, along the posterior column of the acetabulum. The lesion was considered suspicious for osteoid osteoma, overlooked on previous examinations. Therefore, a diagnosis of multicentric and multifocal osteoid osteoma was established. The new lesion was again treated with radiofrequency ablation with symptom disappearance. However, hip pain relapsed after 18 months, and CT and MRI showed an osteoid osteoma recurrence on the posterior column of the acetabulum, which was biopsied and successfully treated using radiofrequency ablation. CONCLUSIONS: To our knowledge, this is the first reported case of multicentric, multifocal, recurrent osteoid osteoma. Our case report highlights the importance of considering a diagnosis of multifocal osteoid osteoma when dealing with multifocal lytic lesions of the bone and with pain persistence after treatment. It also emphasises the combined role of CT and MRI in this setting.

Phalangeal Osteoid Osteoma of Thumb.

Osteoid osteomas are typically benign osteoblastic bone tumors. Patients often present in their twenties with progressively increasing pain that is worse at night and relieved with nonsteroidal anti-inflammatory drugs. These lesions rarely occur in the hand or wrist; however, when those are involved, the proximal phalanx is the most common location and the index finger is the most commonly affected digit. Lesions affecting the distal phalanges are least likely to occur and the thumb is least likely to be affected. Osteoid osteomas of the distal phalanges can cause great diagnostic challenges. They often present with atypical radiographic and physical examination findings. Although rare, osteoid osteomas of the distal phalanx can be a major cause of digit enlargement and pain. In a patient with a painful and/or swollen digit, the diagnosis should be considered.

Mini-open excision of osteoid osteoma using intraoperative O-arm/Stealth navigation.

BACKGROUND: Although osteoid osteomas have traditionally been treated by surgical excision, radiofrequency ablation (RFA) has gained favor as a less invasive procedure. However, RFA is contraindicated for osteoid osteomas close to the skin or crucial neurovascular structures, and is not covered by national health insurance in Japan. The aim of the present study was to evaluate the efficacy of surgical excision of osteoid osteomas using intraoperative navigation. METHODS: We performed a retrospective review of five patients with osteoid osteoma who underwent a mini-open excision using O-arm/Stealth navigation at our institution. The osteoid osteomas were excised using a cannulated cutter or curetted out with the assistance of navigation. RESULTS: Complete excision was achieved in all patients, which was confirmed by pathological examination. The mean skin incision was 2.1 cm (range, 1.5 to 3.0 cm) and the mean duration required for setup three-dimensional image was 15 min (range, 12 to 20 min). Although the mean visual analog scale score was 7 (range, 4 to 8) before surgery, all patients experienced relief from their characteristic pain immediately after surgery, with the mean scores of 2.2 (range, 1 to 3) and 0 at 2 days and 4 weeks after surgery, respectively. There was no intra-operative complication related to the navigation and no recurrence was observed during the mean follow-up period of 25 months (range, 13 to 33 months). CONCLUSIONS: Mini-open excision using intraoperative O-arm/Stealth navigation is a safe and accurate procedure for patients with osteoid osteoma, which could cover the limitation of RFA.

Hyperhidrotic Macrodactylism Caused by Osteoid Osteoma: A Case Report and Review of the Literature.

Macrodactylism or macrodactyly is referred to as congenital deformity of fingers or toes, and the corresponding incidence rate is relatively low. In this article, we describe a young male with macrodactylism of the second toe of his right foot. He was suffering from persistent pain, overgrowth, and hyperhidrosis ofthe involved toe. Radiographic examination of the right foot showed a small translucent area surrounded by hyperplasia and sclerotic bone in the second distal phalanx, in addition to increased soft tissue density and volume. Surgical resection of the bone lesion and reduction of the soft tissue bulk were performed. Pathological findings showed osteoblast hyperplasia, which was diagnosed as osteoid osteoma, and noabnormal findings were seen in the skin. Symptoms of pain and hyperhidrosis disappeared postsurgery and did not recur over the subsequent 2-year follow-up. As far as we know, this was a rare case of osteoid osteoma occurring in the toe that resulted in macrodactylism, which was also associated with localized hyperhidrosis.

[An update for the treatment of osteoid osteoma]. / Le point sur le traitement percutané des ostéomes ostéoïdes.

Osteoid osteoma is frequent benign tumor, descripted initially by Bergstrand in 1930 followed by Jaffe in 1935. The painful feature of the osteoid osteoma explains the specific consideration by the medical community for this entity. The debate was focused on pathologic and imaging pattern as well as the treatment modalities. Currently, the treatment options are varied and percutaneous treatment is increasingly used. The radiofrequency is widely validated as efficient method without serious adverse and with low rate of recurrence. We hope through this this work to revue the current knowledge of the treatment of osteoid osteoma.

L'ostéome ostéoïde est une tumeur osseuse bénigne relativement fréquente initialement décrite par Bergstrand en 1930, puis comme une entité propre grâce aux recherches de Jaffe en 1935. Malgré sa bénignité, elle a concentré toute l'attention des radiologues comme des cliniciens car très symptomatique. Dès lors, l'ostéome ostéoïde a fait l'objet de nombreux débats dans la communauté scientifique en particulier concernant son étiologie, ses caractéristiques pathologiques, son bilan d'imagerie et son traitement. C'est sur cette dernière question que les avancées ont été les plus marquantes et c'est ainsi que les possibilités thérapeutiques bien décrites dans la littérature apparaissent variées. Toutefois, les résultats très favorables des traitements percutanés et en particulier de la radiofréquence, de même que le faible taux de récidives et de complications de ces traitements, ont amené de nombreux pays à les considérer comme le meilleur traitement en première intention. A travers cette revue de la littérature et de notre pratique clinique, nous souhaitons rapporter les connaissances actuelles thérapeutiques en perpétuelle progression grâce au progrès technique.

An open-label, prospective, observational study of the efficacy of bisphosphonate therapy for painful osteoid osteoma.

OBJECTIVES: To assess the efficacy of bisphosphonate therapy on bone pain in patients with osteoid osteoma (OO) (main objective), and to describe bisphosphonate-induced changes in nidus mineralisation and regional bone-marrow oedema (BMO). METHODS: A prospective, observational study was conducted from 2011 to 2014. Patients with risk factors for complications of percutaneous or surgical ablation or recurrence after ablation, were offered once monthly intravenous bisphosphonate treatment until significant pain alleviation was achieved. RESULTS: We included 23 patients. The first two patients received pamidronate and the next 21 zoledronic acid (mean, 2.95 infusions per patient). Bisphosphonate therapy was successful in 19 patients (83%), whose mean pain visual analogue scale score decreased by 76.7%; this pain-relieving effect persisted in 17 patients (74%) with a mean follow-up time of 36 months. Computed tomography (CT) demonstrated a mean nidus density increase of 177.7% (p = 0.001). By magnetic resonance imaging (MRI), mean decreases were 38.4% for BMO surface area and 30.3% for signal intensity (p = 0.001 and p = 0.000, respectively). CONCLUSIONS: In 17/23 patients with painful OO managed conservatively with bisphosphonates, long-term final success was achieved. Bisphosphonates may accelerate the spontaneous healing of OO. KEY POINTS: • 19/23 patients with OO managed with bisphosphonates experienced significant pain relief • Pain relief was sustained in 17/23 patients, mean follow-up of 36 months • CT demonstrated a significant increase in nidus mineralisation • MRI demonstrated a significant decrease in bone marrow oedema • Bisphosphonate therapy may accelerate the spontaneous healing of OO.

Technical aspects of osteoid osteoma ablation in children using MR-guided high intensity focussed ultrasound.

BACKGROUND: Osteoid osteoma (OO) is a painful bone tumour occurring in children and young adults. Magnetic resonance imaging-guided high intensity focussed ultrasound (MR-HIFU) allows non-invasive treatment without ionising radiation exposure, in contrast to the current standard of care treatment with radiofrequency ablation (RFA). This report describes technical aspects of MR-HIFU ablation in the first 8 paediatric OO patients treated in a safety and feasibility clinical trial (total enrolment of up to 12 patients). MATERIALS AND METHODS: OO lesions and adjacent periosteum were treated with MR-HIFU ablation in 5-20 sonications (sonication duration = 16-48 s, frequency = 1.2 MHz, acoustic power = 20-160 W). Detailed treatment workflow, patient positioning and coupling strategies, as well as temperature and tissue perfusion changes were summarised and correlated. RESULTS: MR-HIFU ablation was feasible in all eight cases. Ultrasound standoff pads were shaped to conform to extremity contours providing acoustic coupling and aided patient positioning. The energy delivered was 10 ± 7 kJ per treatment, raising maximum temperature to 83 ± 3 °C. Post ablation contrast-enhanced MRI showed ablated volumes ranging 0.46-19.4 cm3 extending further into bone (7 ± 4 mm) than into soft tissue (4 ± 6 mm, p = 0.01, Mann-Whitney). Treatment time ranged 30-86 min for sonication and 160 ± 40 min for anaesthesia. No serious treatment-related adverse events were observed. Complete pain relief with no medication occurred in 7/8 patients within 28 days following treatment. CONCLUSIONS: MR-HIFU ablation of painful OO appears technically feasible in children and it may become a non-invasive and radiation-free alternative for painful OO. Therapy success, efficiency, and applicability may be improved through specialised equipment designed more specifically for extremity bone ablation.

Targetability of osteoid osteomas and bone metastases by MR-guided high intensity focused ultrasound (MRgHIFU).

PURPOSE: To retrospectively evaluate the suitability of MRgHIFU for osteoid osteomas (OOs) and bone metastases in patients who underwent minimally-invasive percutaneous thermal ablation. MATERIALS AND METHODS: One hundred and sixty-seven lesions (115 metastases and 52 OOs) treated percutaneously between October 2014 and June 2017 were retrospectively analyzed. Tumors were located in the spine or sacrum (54), pelvis (43), limbs (50), ribs (17) and sternum (3). Tumor volume, matrix, anatomical environment and need for protection of surrounding structures or consolidation were assessed. Cases were classified into three categories: (a) lesions suitable for MRgHIFU therapy alone; (b) lesions suitable for MRgHIFU if protection of surrounding structures and/or bone consolidation is performed; (c) lesions not suitable for MRgHIFU. RESULTS: Twenty-six (50%) of OOs were classified as suitable for MRgHIFU alone and 17 (32.7%) as suitable for MRgHIFU with hydro-dissection. Matrix of treatable OOs was sclerotic (19), lytic (15) or mixed (9), with mean volume 0.56 cm3. Forty-one (35.7%) of metastases were classified as suitable for MRgHIFU alone and 43 (37.4%) as suitable with hydro-dissection and/or consolidation. Matrix of metastases was sclerotic (13), lytic (37) or mixed (34), with mean volume 71.9 cm3. Mean depth of targetable lesions was 50.9 ± 28.4 mm. 97.7% of pelvic lesions and 94% of peripheral bone lesions were targetable by HIFU. 66.6% of spinal or sacral lesions were considered untreatable. CONCLUSION: MRgHIFU cannot be systematically performed non-invasively on bone tumors. Combination with minimally-invasive thermo-protective techniques may increase the number of eligible cases.

Osteoblastomatosis: an unusual diagnosis and treatment.

Osteoblastomatosis (OBLT), also referred to as multifocal osteoblastoma (OB), is an unusual and recently described entity consisting of multifocal tumors histologically consistent with osteoblastoma and osteoid osteoma (OO) but radiologically mimicking a vascular bone lesion. OBLT treatment is based on aggressive procedures, such as amputation, en bloc resection, and chemotherapy. Only one previously reported case was successfully treated following a multimodal approach consisting of curettage, cryotherapy, intravenous bisphosphonates, and radiofrequency ablation. We present a case of OBLT that may have been cured by CT-guided percutaneous radiofrequency ablation.

Spinal osteoid osteoma progressed to osteoblastoma with paraspinal soft tissue mass: a unique presentation.

Osteoid osteoma and osteoblastoma are rare benign bone-forming tumors with very similar histological features. They are nowadays considered as two distinct entities. Progression of an osteoid osteoma to osteoblastoma is considered very rare with only a few cases reported in the literature. Herein we describe a case of an osteoid osteoma of the thoracic spine in a 29-year-old woman that was initially treated conservatively and progressed to osteoblastoma 5 years following the initial diagnosis. Imaging revealed an increase in the size of the spinal lesion that was surrounded by extensive paraspinal abnormal soft tissue that raised suspicion for sarcomatous transformation. The final diagnosis was established by CT-guided biopsy of both the bone lesion and the paraspinal soft tissue, which excluded malignancy and revealed an osteoblastoma surrounded by plasma cell-rich chronic inflammation. The patient then underwent wide surgical excision of the lesion and paraspinal soft tissue component that confirmed the diagnosis. Follow-up with MRI over the next 12 months was unremarkable, with no signs of recurrence or spinal instability. This unique presentation of an osteoblastoma has not been previously described. This case also demonstrates the importance of follow-up of osteoid osteomas that are treated conservatively.

[Diagnostics and treatment of osteoid osteoma]. / Diagnostik und Therapie des Osteoidosteoms.

BACKGROUND: Osteoid osteoma is the third most common benign bone tumor and typically induces pain that is worse at night. OBJECTIVE: To identify the epidemiological, pathogenetic, histological and radiological characteristics of osteoid osteoma and to present the broad variety of treatment options. MATERIAL AND METHODS: This review article summarizes relevant clinical studies and meta-analyses on this topic. RESULTS: Osteoid osteoma is characterized by a central nidus smaller than 1.5 cm in diameter with surrounding bone sclerosis. In the majority of cases, the tumor occurs in the long bones of the lower extremities and is predominantly manifested in patients aged between 5 and 25 years. Pain is mediated by prostaglandins, which stimulate afferent peripheral nerve fibers. Besides plain radiographs, thin-section computed tomography represents the gold standard of diagnostics but should be complemented by magnetic resonance or nuclear medicine imaging modalities. The conservative treatment consists of long-term therapy with non-steroidal anti-inflammatory drugs. Minimally invasive radiofrequency ablation of the nidus is the current operative treatment of choice. CONCLUSION: Success rates of radiofrequency ablation and other minimally invasive procedures are high while treatment costs and length of hospital stay are low. Thus, open surgical curettage is reserved for rare indications and en bloc excision of the nidus should only be performed in cases of recurrent lesions.

[RARE LOCALIZATION OF OSTEOID OSTEOMA--DISTAL PHALANX OF THE RING FINGER].

With this clinical observation we would like to bring to mind osteoid osteoma as a possible cause of problems of distal phalanx of the fingers. Osteoid osteoma occurs rarely at this location and has atypical presentation. The main symptoms are swelling and redness of the fingertip with nail deformity, while typical night pain may not be present. Unusual clinical and x-ray presentation of tumor in this localization can make diagnosis of osteoid osteoma very difficult. A 20-year-old patient reported pain in the fingertip of his right ring finger persisting for five years. Swelling and redness of the fingertip combined with nail deformity was also present. X-rays showed osteolysis in the base of distal phalanx. Magnetic resonance imaging showed suspicion of osteoid osteoma, which was confirmed by computed tomography (CT). We performed surgical removal of osteoid osteoma in February 2014. The tumor was approached by longitudinal incision on the lateral side of the distal phalanx of the ring finger and the basal part of distal phalanx was cut with a small chisel to enable access to cystic change of the bone. Tumor removal with excochleation was performed and the material thus obtained was sent for histopathologic analysis. After surgery, the ring finger was immobilized in a plaster splint for a three-week period. After removal of immobilization, the patient was referred to physical therapy consisting of individual exercises in order to obtain the full range of motion in all joints of the hands and strengthen hand and forearm muscles. After surgical removal of osteoid osteoma, all symptoms disappeared completely. Histopathologic findings confirmed the diagnosis of osteoid osteoma. After physical therapy, he returned to daily activities without any problems. On regular follow ups at 3, 6 and 12 months after surgery, clinical findings were normal and the patient had no pain or discomforts. Full recovery was shown by the result of the DASH questionnaire three months after the procedure. Preoperative DASH score 54.4 decreased to 0. Distal phalanx of the finger is a very rare localization of osteoid osteoma, and typical night pain may not be present. In addition, appearance on x-rays is not typical. Instead of central enlightenment surrounded with sclerosis, x-rays usually show a lytic lesion. For this reason, it may be difficult to make the diagnosis of osteoid osteoma. The main symptom is permanent pain, swelling and redness of the finger, with nail deformity. The imaging method of choice is CT, which must be performed with thin layers of 1 to 2 mm. Furthermore, cooperation of surgeon and radiologist is extremely important to reach the accurate diagnosis. Many treatment options are described in the literature, such as CT-guided percutaneous thermocoagulation, destruction of lesions with alcohol, or CT-guided radiofrequency ablation. However, due to the proximity of neurovascular structures, tendons and joints, the best method for treatment osteoid osteoma in distal phalanx of the fingers is surgical excision or excochleation. Our conclusion is that one should always bear in mind that osteoid osteoma can be the cause of swelling of distal phalanx of the finger with nail deformity, and pain that alleviated with the use of non-steroidal anti-infl ammatory drugs. Surgical excision or excochleation is the best method for the treatment osteoid osteoma of distal phalanx of the finger.