Radiologic diagnosis of osteoid osteoma: from simple to challenging findings

A comprehensive MRI analysis of osteoid osteomas in patients with diverse radiological features across various regions

BACKGROUND

Magnetic resonance imaging (MRI), which does not involve ionizing radiation, is the preferred imaging modality for diagnosing osteoid osteoma (OO), an ailment more common in children and young adults.

PURPOSE

This study aims to perform a literature review and delineate the MRI findings of OO lesions in patients exhibiting varying radiological features across different regions.

MATERIALS AND METHODS

A retrospective study included 63 patients diagnosed with OO through MRI, assessed independently by two blinded radiologists using both standard and dynamic contrast-enhanced MRI techniques. After excluding 7 patients with prior biopsy, surgery, or RFA, the study included 56 patients with 57 lesions.

RESULTS

Of 57 lesions evaluated, 50 were in long, and 7 in flat bones. One patient presented with two separate nidi within the intertrochanteric region. Most of the lesions, 49 (86%), were extra-articular, while 8 (14%) were intra-articular. The nidus was intracortical in 45 (78.9%) patients, intramedullary in 5 (8.8%), subperiosteal in 5 (8.8%), and endosteal in 2 (3.5%). Average nidus diameter was 7.02 ± 2.64 mm (3-12.6 mm). Central nidal calcification was present in 68.4% (n = 39) cases. Contrast enhancement was intense at 90.5%, moderate at 9.5%. Reactive sclerosis around the nidus was severe (50.9%), moderate (22.8%), and mild (26.3%). Bone marrow edema was severe (70.2%), moderate (14.0%), and mild (15.8%). Soft tissue edema was identified in 77.2% of all lesions.

CONCLUSION

To minimize delays in diagnosis and treatment, radiologists should become acquainted with the typical OO MRI findings and the atypical MRI findings that might be mistaken for other conditions.

Intra-articular Osteoid Osteomas: Imaging Manifestations and Mimics

Osteoid osteoma (OO) is the third most prevalent benign bone neoplasm in children. Although it predominantly affects the diaphysis of long bones, OO can assume an intra-articular location in the epiphysis or the intracapsular portions of bones. The most common location of intra-articular OO is the hip joint. The presentation of intra-articular OOs often poses a diagnostic enigma, both from clinical and radiologic perspectives. Initial symptoms are often vague and nonspecific, characterized by joint pain, stiffness, and limited range of motion, which frequently contributes to a delayed diagnosis. Radiographic findings range from normal to a subtle sclerotic focus, which may or may not have a lucent nidus. In contrast to their extra-articular counterparts, intra-articular lesions have distinct features at MRI, including synovitis, joint effusion, and bone marrow edema-like signal intensity. While CT remains the standard for identifying the nidus, even CT may be inadequate in visualizing it in some cases, necessitating the use of bone scintigraphy or fluorine 18-labeled sodium fluoride PET/CT for definitive diagnosis. Radiologists frequently play a pivotal role in suggesting this diagnosis. However, familiarity with the unique imaging attributes of intra-articular OO is key to this endeavor. Awareness of these distinctive imaging findings of intra-articular OO is crucial for avoiding diagnostic delay, ensuring timely intervention, and preventing unnecessary procedures or surgeries resulting from a misdiagnosis. The authors highlight and illustrate the different manifestations of intra-articular OO as compared with the more common extra-articular lesions with respect to clinical presentation and imaging findings. ©RSNA, 2024 Supplemental material is available for this article.

Diagnostic performance and inter-reader reliability of bone reporting and data system (Bone-RADS) on computed tomography

OBJECTIVE

To evaluate the diagnostic performance and inter-reader reliability of the Bone Reporting and Data System (Bone-RADS) for solitary bone lesions on CT.

MATERIALS AND METHODS

This retrospective analysis included 179 patients (mean age, 56 ± 18 years; 94 men) who underwent bone biopsies between March 2005 and September 2021. Patients with solitary bone lesions on CT and sufficient histopathology results were included. Two radiologists categorized the bone lesions using the Bone-RADS (1, benign; 4, malignant). The diagnostic performance of the Bone-RADS was calculated using histopathology results as a standard reference. Inter-reader reliability was calculated.

RESULTS

Bone lesions were categorized into two groups: 103 lucent (pathology: 34 benign, 12 intermediate, 54 malignant, and 3 osteomyelitis) and 76 sclerotic/mixed (pathology: 46 benign, 2 intermediate, 26 malignant, and 2 osteomyelitis) lesions. The Bone-RADS for lucent lesions had sensitivities of 95% and 82%, specificities of 11% and 11%, and accuracies of 57% and 50% for readers 1 and 2, respectively. The Bone-RADS for sclerotic/mixed lesions had sensitivities of 75% and 68%, specificities of 27% and 27%, and accuracies of 45% and 42% for readers 1 and 2, respectively. Inter-reader reliability was moderate to very good (κ = 0.744, overall; 0.565, lucent lesions; and 0.851, sclerotic/mixed lesions).

CONCLUSION

Bone-RADS has a high sensitivity for evaluating malignancy in lucent bone lesions and good inter-reader reliability. However, it has poor specificity and accuracy for both lucent and sclerotic/mixed lesions. A possible explanation is that proposed algorithms heavily depend on clinical features such as pain and history of malignancy.

Case 326: Intra-Articular Osteoid Osteoma

HISTORY

A 15-year-old male patient presented with a 3-week history of inner left thigh pain provoked by activity and experienced occasionally at rest. The patient denied nighttime pain, fever, or chills. Laboratory investigation revealed the following normal values: hemoglobin level of 15.6 g/dL (normal range, 13-16 g/dL), platelet count of 240 × 103/µL (normal range, 140-440 × 103/µL), and total leukocyte count of 7100 cells/µL (normal range, 4500-11 000 cells/µL). The percentage of neutrophils was considered low at 44% (normal range, 54%-62%), and the percentage of eosinophils was slightly high at 3.7% (normal range, 0%-3%). An anteroposterior radiograph of the left hip is shown. Physical therapy was initiated, with no improvement after 2 weeks of therapy. The patient was referred to an orthopedist for further evaluation. At physical examination, the patient endorsed marked left hip pain with hip flexion to 90°, limited internal and external rotation (5° and 15°, respectively), and antalgic gait favoring the left leg. Hip MRI and further serologic analysis were requested for further evaluation. Although the serologic testing was performed at an outside laboratory, the physician reported positive immunoglobulin-G Lyme titers, normal C-reactive protein level, and normal erythrocyte sedimentation rate. Pelvic CT was requested. The patient was prescribed a course of doxycycline (100 mg twice daily for 28 days), with reported resolution of symptoms 2 weeks after initiation of treatment. Three weeks later, the patient presented to our department with recurrent left hip pain, which was similar in severity compared with the initial presentation. A second MRI examination of the left hip was performed 4 months after the initial presentation.

A comparative study assessing the efficacy and safety of radiofrequency ablation versus surgical treatment for osteoid osteoma: retrospective analysis in a single institution

OBJECTIVE

We aim to evaluate the efficacy of CT-guided percutaneous radiofrequency ablation (RFA) and surgical treatment in osteoid osteoma (OO) treated at the Medical University of Graz.

MATERIALS AND METHODS

In a single-institution study, we analysed data from January 2005 to January 2021 of patients with histological/radiological diagnosis of OO. CT and MRI scans were reviewed for typical findings. Means (with SD) and medians (with IQR) were reported for normally and non-normally distributed variables. Differences between groups were assessed using chi-squared tests and t-tests.

RESULTS

One hundred nineteen patients (mean age: 21.6 ± 10.9 years; 63.9% males) with confirmed OO were retrospectively evaluated. 73 and 43 patients underwent RFA and surgery, respectively. In three cases, RFA combined with surgery was performed. Pre-intervention, 103 patients (88.8%) had undergone CT, and 101 had an MRI (87.1%). The nidus was confirmed in 82.5% of cases with CTs (85/103) and 63.4% with MRIs (64/101). The majority of nidi were located cortically (n = 96; 82.8%), most frequently in the femur (38 patients, 33.3%) with a median size of 8.0 mm (IQR: 5.0-12.0 mm). Median symptom duration before treatment was 6.0 (IQR: 4.0-13.0) months. The complication rate was 12.1% (14/116; 15.1% RFA vs. 7.0% surgery; p = 0.196). In total, 11.2% of patients had persistent symptoms after one week with clinical success rates of RFA and surgery, 86.3% and 90.7% (p = 0.647), respectively.

CONCLUSION

Compared to surgical treatment, CT-guided percutaneous RFA is a safe, minimally invasive, reliable, and efficient treatment option for OO.

CRITICAL RELEVANCE STATEMENT

This article critically assesses the diagnosis and treatment of osteoid osteoma, emphasising accurate imaging, and detailing a non-invasive option for effective management.

KEY POINTS

• This study analyses 116 cases of OO at one institution, focusing on symptom persistence, recurrence in short-term follow-up, and complications in two study groups. • Surgery showed higher, though not statistically significant, success despite comparable symptom persistence; CT displayed typical OO features more than MRI, regardless of the intramedullary, cortical and subperiosteal location as well as the site of the affected bone. • CT-guided RFA is an effective therapeutic alternative for OO compared to surgical intervention. In case of atypical OO appearance, RFA is not the first-line treatment.

Bacterial osteomyelitis in pediatric patients: a comprehensive review

Bacterial osteomyelitis, an inflammatory response in the bone caused by microorganisms, typically affects the metaphysis in the skeletally immature. Bacterial osteomyelitis possesses a significant diagnostic challenge in pediatric patients due to its nonspecific clinical presentation. Because the metaphysis is the primary focus of infection in skeletally immature patients, understanding the normal physiologic, maturation process of bones throughout childhood allows to understand the pathophysiology of osteomyelitis. Timely and accurate diagnosis is crucial to initiate appropriate treatment, and prevent long-term sequelae and efforts must be made to isolate the causative organism. The potential causative organism changes according to the age of the patient and underlying medical conditions. Staphylococcus Aureus is the most common isolated bacteria in pediatric pyogenic osteomyelitis whereas Kingella Kingae is the most common causative agent in children aged 6 months to 4 years. Imaging plays a pivotal role in the diagnosis, characterization, evaluation of complications, and follow up of bacterial osteomyelitis. Imaging also plays a pivotal role in the evaluation of potential neoplastic and non-neoplastic mimickers of osteomyelitis. In children, MRI is currently the gold standard imaging modality when suspecting bacterial osteomyelitis, whereas surgical intervention may be required in order to isolate the microorganism, treat complications, and exclude mimickers.

A rare cause of shoulder pain: Osteoid osteoma of the scapular glenoid treated with cryoablation

We report a case of an osteoid osteoma at the scapular glenoid that was treated with cryoablation. The patient presented with shoulder pain with subsequent CT and MRI imaging findings suspicious for an osteoid osteoma. The patient complained of persistent pain despite medical treatment and was referred to interventional radiology for consideration of ablation. CT-guided biopsy confirmed the diagnosis of osteoid osteoma and the patient underwent cryoablation of the lesion in the same session. The patient reported a substantial relief in her pain at a follow-up 4 weeks after the procedure. MRI performed 8 weeks after the procedure also confirmed radiographic remission of the lesion.

Incidental Identification of Osteoid Osteoma of Skull Bone on 68 Ga-PSMA PET/CT

ABSTRACT

An osteoid osteoma (OO) is a benign bone neoplasm, characterized by significant nocturnal pain that usually responds to nonsteroidal anti-inflammatory drugs. It occurs most commonly in the lower extremities and vertebrae. Here, we present a case of carcinoma prostate, who was referred to our department for 68 Ga-PSMA PET/CT scan, and we incidentally found out PSMA-avid OO involving frontal bone of skull, which is a rare finding. To the best of our knowledge, this is the second case in which high PSMA uptake is found in the OO, suggesting a possible PSMA expression related to osteoblastic activity.

Intraoperative cone-beam computed tomography-guided curettage for osteoid osteoma

Recently, cone-beam computed tomography (CBCT)-guided surgeries have been developed for bone and soft tissue tumors. The present study aimed to evaluate the efficacy of CBCT-guided curettage for osteoid osteoma. Our study population included 13 patients who underwent primary curettage for osteoid osteoma using intraoperative CBCT in a hybrid operating room between April 2019 and November 2022. We collected the following data: sex, age, follow-up period, symptom onset to time of surgery, tumor size and location, length of skin incision, operating time, radiation dose, recurrence, postoperative complications, and visual analog scale for pain during the last follow-up. There were 10 male and 3 female patients, and the mean age was 25.0 years (range, 9-49 years). The mean follow-up period was 10.6 months (range, 0.4-24.0 months). The locations of the tumors were the proximal femur in 6 patients, the acetabular region in 2 patients, and the ilium, tibial shaft, calcaneus, cuboid, and talus in 1 patient each. The mean time of symptoms onset to surgery was 18.7 months (range, 2.3-69.9 months). The mean maximum diameter of the tumor was 5.9 mm (range, 3.5-10.0 mm). The mean length of the skin incision was 2.2 cm (range, 1.5-3.5 cm). The mean operating time was 96.9 minutes (range, 64-157 minutes). The mean dose of radiation was 193.2 mGy (range, 16.3-484.0 mGy). No recurrences, postoperative complications, and reoperation were observed in this study. All the patients reported 0 mm on the visual analogue scale for pain on the last follow-up. CBCT-guided curettage for osteoid osteoma was minimally invasive and reliable. This procedure can be effective for the treatment of lesions found in deep locations such as the pelvic bone and proximal femur or an invisible lesion that cannot be detected by regular fluoroscopy.

Percutaneous Cryoablation under Conscious Sedation: A Safe, Effective and Painless Option for the Treatment of Pediatric Osteoid Osteoma

BACKGROUND

Percutaneous CT-guided cryoablation is an emerging technique for treating bone tumors. However, experience with using this procedure for osteoid osteomas in pediatric patients remains limited. Our study aims to assess its technical feasibility, clinical efficacy, and safety in children treated under conscious anesthesia.

METHODS

We conducted a retrospective study of consecutive pediatric patients who underwent CT-guided percutaneous cryoablation for osteoid osteomas at our institution between September 2017 and March 2021. All patients received conscious anesthesia. Data on peri-procedural VAS scores, post-procedural VAS scores, imaging findings, and nonsteroidal anti-inflammatory drug (NSAID) usage rates were collected for each patient. Technical success was defined as proper cryoprobe placement at the nidus center, while clinical success referred to pain relief without NSAID use. Intra- and post-operative complications were also evaluated.

RESULTS

Nine patients underwent CT-guided percutaneous cryoablation for osteoid osteomas under conscious sedation, with a 100% overall success rate with low peri-procedural and median VAS scores (p < 0.01). No complications were observed during or after the procedure.

CONCLUSIONS

CT-guided percutaneous cryoablation of pediatric osteoid osteomas is an effective and safe minimally invasive procedure feasible under conscious anesthesia, holding promise as a valuable treatment option.

Osteoid osteomas of the hip: a well-recognized entity with a proclivity for misdiagnosis

OBJECTIVES

The diagnosis of osteoid osteomas (OO) about the hip can be challenging as presenting symptoms can mimic other, more common, periarticular pathologies. Our aims were to identify the most common misdiagnoses and treatments, mean delay in diagnosis, characteristic imaging features and provide tips for avoiding diagnostic imaging pitfalls for patients with OO of the hip.

METHODS

We identified 33 patients (34 tumors) with OO about the hip who were referred for radiofrequency ablation between 1998 and 2020. Imaging studies reviewed included radiographs (n = 29), CT (n = 34), and MRI (n = 26).

RESULTS

The most common initial diagnoses were femoral neck stress fracture (n = 8), femoroacetabular impingement (FAI) (n = 7), and malignant tumor or infection (n = 4). The mean time from symptom onset to diagnosis of OO was 15 months (range, 0.4-84). The mean time from initial incorrect diagnosis to OO diagnosis was 9 months (range, 0-46).

CONCLUSIONS

The diagnosis of OO of the hip is challenging, with up to 70% of cases initially misdiagnosed as a femoral neck stress fracture, FAI, bone tumor, or other joint pathology in our series. Consideration of OO in the differential diagnosis of hip pain in adolescent patients and awareness of the characteristic imaging findings are critical for making an accurate diagnosis.

KEY POINTS

• The diagnosis of osteoid osteoma of the hip can be challenging, as demonstrated by long delays in time to initial diagnosis and high rates of misdiagnoses which can lead to inappropriate interventions. • Familiarity with the spectrum of imaging features of OO, especially on MRI, is imperative given the increase in the utilization of this modality for the evaluation of young patients with hip pain and FAI. • Consideration of OO in the differential diagnosis of hip pain in adolescent patients and awareness of the characteristic imaging findings, including bone marrow edema and the utility of CT, are critical for making a timely and accurate diagnosis.

Outcomes of Osteoid Osteoma Treated by Percutaneous CT-Guided Radiofrequency Ablation

Introduction Osteoid osteomas are the most frequent true benign bone tumor in the adolescent age group and the third most prevalent benign bone tumor overall. This study was designed to assess the effectiveness of the procedure and correlate it with the analgesia offered because of the significant burden of this illness and new literature supporting the successful outcomes of image-guided percutaneous radiofrequency ablation (RFA) in osteoid osteoma. Methodology  This hospital-based interventional trial was carried out in a tertiary care referral center. Forty-two patients with osteoid osteoma, ranging in age from 9 to 30, were included in the study. The patients received RFA guided by computed tomography (CT), and they were postoperatively monitored at one, two, and four weeks and three, six months, and 12 months. A numerical pain scale (NPS) was used to evaluate the patient's pain both before and after the procedure. The preoperative and postoperative results were contrasted. Results A total of 42 participants were enrolled in the study. Eight (19.05%) women and 34 (80.95%) men made up the group. Complete pain alleviation (NPS=0) was attained in 42.8% and 96.4% of the study group in the first and second weeks post-procedure. Almost all patients began protected weight-bearing at one week, according to their level of pain tolerance. Osteoid osteoma of the talus was a remnant lesion in one patient that required further treatment after two weeks. During the duration of the follow-up, no problems were recorded. Conclusion Percutaneous CT-guided RFA of osteoid osteoma is a safe, minimally invasive procedure and greatly reduces the duration of hospitalization. It has excellent functional outcomes and no known complications.

Intra-articular Lateral Tibial Plateau Osteoid Osteoma: Case Report and Arthroscopic Management

Osteoid osteoma occurs in various locations in the human body, mostly in the metaphysis and diaphysis of long bones. This article describes a rare case of osteoid osteoma occurring in an intra-articular location, specifically in the lateral tibial plateau of a 40-year-old female patient. The challenge of diagnosing such a pathology in an atypical location was tackled in this article as well as different management options. Arthroscopic resection was opted in this case.

Osteoid Osteoma, a Diagnostic Problem: A Series of Atypical and Mimicking Presentations and Review of the Recent Literature

Osteoid osteoma (OO) is a common benign bone tumour, usually affecting young people. Typically, it is localised to the diaphyses or metaphyses of long bones. The classical manifestation includes distinctive night pain, almost always present, responding well to non-steroidal anti-inflammatory drugs, sometimes accompanied by complaints due to physical activity, and a typical picture on additional tests. A characteristic of osteoid osteoma is the presence of a nidus, usually visible on imaging tests. The nidus generally presents as a single, round lytic lesion up to 1 cm in diameter, surrounded by an area of reactive ossification. However, OO is a multifaceted neoplasm, and its diagnosis can cause numerous difficulties. OO can mimic multiple diseases and vice versa, which often leads to a prolonged diagnostic and therapeutic path and associated complications. There are few literature reviews about the differentiation and diagnostic difficulties of osteoid osteoma. Very effective therapies for this tumour are known, such as ablation and resection. Enhanced detection of osteoid osteoma could result in faster diagnosis and less suffering for the patient, avoidance of complications, and reduced costs of incorrect and prolonged treatment.

Update of pediatric bone tumors: osteogenic tumors and osteoclastic giant cell-rich tumors

There are numerous bone tumors in the pediatric population, with imaging playing an essential role in diagnosis and management. Our understanding of certain bone tumors has rapidly evolved over the past decade with advancements in next-generation genetic sequencing techniques. This increased level of understanding has altered the nomenclature, management approach, and prognosis of certain lesions. We provide a detailed update of bone tumors that occur in the pediatric population with emphasis on the recently released nomenclature provided in the 5^th edition of the World Health Organization Classification of Soft Tissue and Bone Tumours.

Benign Bone Lesions Found in Childhood

Benign bone tumors are a wide variety of usually asymptomatic neoplasms, which in most cases are diagnosed due to secondary causes. As such, their real incidence is unknown. In the majority of cases, plain radiographs are enough for diagnosis; more advanced imaging, such as CT scan or MRI is sometimes performed for equivocal lesions. Treatment approach depends on whether the lesion is symptomatic and the risk of further progression, or development of secondary malignancies. When non expectant management is decided, treatment options include minimally invasive methods and surgery.

Intra-articular Osteoid Osteoma of the Olecranon Fossa

Osteoid osteomas are benign primary bone lesions characterized by a central nidus with surrounding reactive sclerosis, classically presenting as worsening nocturnal pain relieved by non-steroidal anti-inflammatory medications (NSAIDs). These most commonly occur in intracortical bone and the diaphysis of long bones. As a rare entity, intra-articular osteoid osteomas present unusually, often resulting in a delayed or incorrect diagnosis. We present a case of an intra-articular osteoid osteoma, emphasizing the importance of MRI in aiding diagnosis in this atypical location.

Metachronous Osteoid Osteoma of the Mid-Diaphysis of the Fibula and Distal Humerus: A Case Report

Osteoid osteomas are mostly solitary. We report a case of metachronous osteoid osteoma of mid-diaphysis of fibula followed by distal humeral osteoid osteoma after a 7-year interval.

Intra- and juxta-articular osteoid osteoma in children and adolescents

BACKGROUND

Osteoid osteoma (OO) is a common benign tumor in children and adolescents, but intra-and juxta-articular OO is rare and difficult to diagnose. The purpose of this study is to investigate the distinctions between intra- and juxta-articular OO, trying to avoid delaying diagnosis and optimize treatment strategies.

METHODS

Thirty patients diagnosed with OO in the intra- and juxta joint at our institution who underwent surgical resection were included. Clinical and epidemiological factors, preoperative radiograph parameters, including computed tomography (CT), magnetic resonance imaging (MRI), and bone scan, were documented. The outcomes of the involved extremity were evaluated at the final follow-up.

RESULTS

Mean age at diagnosis, interval time, and follow-up time was 8.37±3.79 years old, 4.67±5.88 months, 3.57±2.18 years, respectively. Factors identified to be significantly associated with intra- and juxta-articular OO including pain with activity (P=0.004) and abnormal range of motion (P=0.00). The factor of abnormal range of motion (P=0.03) also influenced the existence of complications. Six children had a secondary operation to cure the recurrence.

CONCLUSIONS

It is essential for clinicians and radiologists to be aware of the atypical clinical and radiographic features of intra- and juxta-articular OO, as the delayed diagnosis can lead to unnecessary pain and further complications after surgeries. The pain with activity and abnormal range of motion is helpful to identify the location of OO. The persistently abnormal range of motion also significantly leads to complications. The open surgeries to resect the nidus in juxta-articular OO were effective.

Osteoid Osteoma of the Proximal Femur: Pitfalls in Diagnosis and Performance of Open Surgical Resection

Aims

Proximal femoral osteoid osteoma (OO) is extremely easy to be misdiagnosed or missed. The purpose of this study was to retrospectively analyze the clinical data of patients with proximal femoral OO in order to determine the clinical manifestation and imaging characteristics of the disease, so as to provide help for the preoperative diagnosis and clinical treatment of proximal femoral OO.

Methods

This was a retrospective study involving 35 patients with proximal femoral OO admitted into our hospital from January 2015 to January 2021. The baseline characteristics of the participants included; 24 males and 11 females, aged between 13 and 25 (mean 16.2) years old, and the course of the disease was 1 to 14 (mean 6.3) months. We used previous medical experience records of the patients to analyze for the causes of misdiagnosis. Moreover, we compared the difference between preoperative and postoperative treatment practices in alleviating pain in OO patients and restoring hip function. Follow-ups were carried out regularly, and patients advised to avoid strenuous exercises for 3 months.

Results

We followed up 35 patients (25 intercortical, 4 sub-periosteal, and 6 medullary) for an average of 41.4 months. We found that 15 patients (42.9%) had been misdiagnosed of synovitis, perthes disease, osteomyelitis, intra-articular infection, joint tuberculosis and hip impingement syndrome, whose average time from symptoms to diagnosis were 6.3 months. Postoperative pain score and joint function score improved significantly compared with preoperative, and complications were rare.

Conclusion

Open surgical resection constitutes an effective treatment for proximal femoral OO by accurately and completely removing the nidus. Wrong choice of examination, and the complexity and diversity of clinical manifestations constitutes the main reasons for the misdiagnosis of proximal femoral OO.

Avoiding Misdiagnosis and Missed Diagnosis for Appropriately Treating Spinal Osteoid Osteomas: A Single‐Center Experience

Objectives

To analyze the causes of misdiagnosis and missed diagnosis in spinal osteoid osteoma, and to put forward solutions to improve diagnosis accuracy and treatment efficacy in patients.

Methods

We performed a retrospective cohort study on patients with spinal osteoid osteoma in Beijing Jishuitan Hospital from January 1983 to September 2019. All patients underwent surgery. The outcome measures were the extent of local pain, nocturnal pain, radicular symptoms of extremities after surgery, and reduction or disappearance of lesions on CT after surgery.

Results

Thirty‐seven patients with spinal osteoid osteoma were recruited in the study. A total of 27% were female, and the mean (SD) age at diagnosis was 21.3 (8.7) years. A total of 87.0% of patients presented with nocturnal pain, and 94.7% of patients were responsive to NSAIDS treatment. The mean (SD) time from the initial onset of symptoms to the final diagnosis was 14.7 (12.5) months. Only four of 37 (10.8%) patients were correctly diagnosed with spinal osteoid osteoma on the first visit to the local hospital. CT is associated with a higher diagnosis rate than X‐ray or MRI on the first visit. Surgical navigation was used in 88.9% of patients who underwent curettage resection, and in 10% of patients who underwent en bloc resection. A total of 37 of 37 patients (100%) reported relief of local pain and radicular symptoms of extremities after surgery, and no recurrence of tumors was found during follow‐ups.

Conclusions

Spinal CTs are recommended to be performed if osteoid osteoma is suspected based on clinical manifestation, including nocturnal pain and responsiveness to NSAIDS treatment, to avoid misdiagnosis and missed diagnosis of spinal osteoid osteoma.

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.

Osteoblastoma of the Distal Radius

Osteoblastomas are rare, benign, bone-forming neoplasms that represent less than 1% of all bone tumors and occur mostly in people aged 10 to 30 years. In long bones, the metadiaphyseal region tends to be most commonly affected. However, to the best of our knowledge, only 11 cases have been reported to occur in the distal radius. We present the clinical, radiological, and histopathological findings of an osteoblastoma of the right distal radius in a 42-year-old woman for whom an open excisional biopsy with nidus removal comprised the treatment and produced a good outcome.

CIRSE Standards of Practice on Thermal Ablation of Bone Tumours

Background

Percutaneous thermal ablation is an effective, minimally invasive means of treating a variety of focal benign and malignant osseous lesions. To determine the role of ablation in individual cases, multidisciplinary team (MDT) discussion is required to assess the suitability and feasibility of a thermal ablative approach, to select the most appropriate technique and to set the goals of treatment i.e. curative or palliative.

Purpose

This document will presume the indication for treatment is clear and approved by the MDT and will define the standards required for the performance of each modality. CIRSE Standards of Practice documents are not intended to impose a standard of clinical patient care, but recommend a reasonable approach to, and best practices for, the performance of thermal ablation of bone tumours.

Methods

The writing group was established by the CIRSE Standards of Practice Committee and consisted of five clinicians with internationally recognised expertise in thermal ablation of bone tumours. The writing group reviewed the existing literature on thermal ablation of bone tumours, performing a pragmatic evidence search using PubMed to search for publications in English and relating to human subjects from 2009 to 2019. Selected studies published in 2020 and 2021 during the course of writing these standards were subsequently included. The final recommendations were formulated through consensus.

Results

Recommendations were produced for the performance of thermal ablation of bone tumours taking into account the biologic behaviour of the tumour and the therapeutic intent of the procedure. Recommendations are provided based on lesion characteristics and thermal modality, for the use of tissue monitoring and protection, and for the appropriately timed application of adjunctive procedures such as osseus consolidation and transarterial embolisation.

Results

Percutaneous thermal ablation has an established role in the successful management of bone lesions, with both curative and palliative intent. This Standards of Practice document provides up-to-date recommendations for the safe performance of thermal ablation of bone tumours.

Safe surgical hip dislocation for acetabular osteoid osteoma excision

Excision of acetabular osteoid osteoma is technically difficult. We report osteoid osteoma of the quadrilateral plate in a 9-year-old girl who presented to us with persistent nocturnal pain, limp and restricted hip joint movement. The child was investigated with CT scan, MRI and triple-phase bone scan. The 0.7 cm nidus was located in the central portion of the cancellous bone in the quadrilateral plate, 1.94 cm inferior to the triradiate cartilage. The child was operated on through the safe surgical dislocation of the left hip. The location of the lesion was gauged from the preoperative CT scan measurement data and intraoperative fluoroscopic aid. The nidus with a sclerotic rim was burred down completely. Postoperative X-ray and CT scan revealed complete excision of the tumour, and the patient was pain-free. At 18 months follow-up, the patient is completely asymptomatic and walking normally.

Osteoid Osteoma in an Adult Wheelchair Basketball Player Mimicking Musculoskeletal Shoulder Pain: Red Flag or a Red Herring?

Osteoid osteoma (OO) is a relatively common, benign bone-forming tumour, which mainly occurs on the long tubular bones of the limbs in adolescents. Usually, the OO is classified based on its localisation. Night-time pain is the major symptom of OO, which is commonly relieved using non-steroidal anti-inflammatory drugs, while surgery is required only for those patients with severe pain or in case of failure of previous conservative treatments. Our case report describes a 56-year-old male basketball player who self-referred to our outpatient physical therapy with a shoulder pain complaint. Considering the anamnesis and the physical examination, the physical therapist referred the patient to an orthopaedic surgeon, who suggested a detailed imaging investigation. The peculiarity of this clinical case is the overlapping of two clinical presentations: the symptomatology of the OO and the concurrent mechanical disorder due to a rotator cuff tendinopathy.

Needleless Ablation of Osteoid Osteoma and Osteoblastoma: The Emergent Role of MRgFUS

Osteoblastoma (OB) and osteoid osteoma (OO) are benign bone-forming tumors, with nearly identical basic microscopic features. The main difference is dimension (OO has usually a nidus measuring <2 cm in diameter). In addition, OB is biologically more active than OO, with a tendency to grow in size. Historically, treatments have included surgical resection and analgesics, although invasiveness and poor tolerance have led to the current standard of care moving toward interventional radiology, where radiofrequency ablation (RFA) represents the most diffuse technique. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) has recently emerged as another innovative alternative treatment, providing tumor ablation through a needleless and ionizing radiation-free modality. In addition, this technique has the ability to guarantee a very precise and controlled increase in temperature, delivering small amounts of energy that can accurately destroy only the lesion, avoiding healthy surrounding tissues. The present review focuses on MRgFUS as the less invasive, safe, effective, and durable treatment option for the management of osteoid osteoma and osteoblastoma, including a description of technical details, indications and outcomes.

Osteoid osteoma of the second metatarsal bone diagnosed on MRI: A case report and literature review

Osteoid osteoma is a relatively common benign bone tumor that is most frequently seen on the appendicular skeleton in adolescents and young adults. Here we present the case of a 14-year-old boy presenting with a 10 month history of pain in his left foot which had been misdiagnosed as stress fracture due to its unusual clinical presentation. Magnetic resonance imaging of the left foot revealed a bone lesion with typical features of the osteoid osteoma on the distal part of the second metatarsal bone. The lesion was surgically removed and the diagnosis of osteoid osteoma was confirmed by post-surgical histopathologic examination of the resected section. The patient reported a substantial relief in his pain 4 weeks following the surgical operation.

A Rare Presentation of Osteoid Osteoma in a 77-Year-Old Patient, Treated with Computer Tomography-Guided Percutaneous Radiofrequency Ablation

Osteoid osteoma (OO) is a benign bone forming tumor characterized by small size and a disproportionate amount of pain. They are most commonly seen between the ages of 5 and 30 years; however, they can be seen in the older patient albeit infrequently. The hands and feet are the least common site of OO among the extremity bones. We present a case of an OO in the hand of a 77-year-old man who underwent successful treatment with computed tomography–guided percutaneous radiofrequency ablation. We believe this is the oldest recorded patient in the medical literature with a histologically confirmed OO. The condition should therefore be considered in the differential diagnosis of a painful sclerotic bone lesion in this age group to avoid a delay in diagnosis and subsequent treatment.

Benign Bone-Forming Tumors

Benign bone-forming tumors comprise osteomas, osteoid osteomas, and osteoblastomas. Osteomas affect a wide age range and are usually discovered incidentally. They occur predominantly in the craniofacial skeleton and are classically composed of compact bone. Osteoid osteomas and osteoblastomas are painful lesions occurring in young patients. They are morphologically similar and characterized by FOS gene rearrangement and c-FOS expression at a protein level. Osteoid osteomas are usually smaller than 2 cm in maximum dimension with limited growth potential; osteoblastomas are larger than 2 cm and may be locally aggressive. Histologically both are composed of anastomosing trabeculae of woven bone.

Osteoid osteoma of the foot : Presentation, treatment and outcome of a multicentre cohort

Background

Osteoid osteomas of the foot are rare, with a varying and atypical clinical as well as radiological presentation impeding early diagnosis and treatment. The aim of the present multicentre study was to 1) analyze epidemiological, clinical and radiological findings of patients with foot osteoid osteomas and to 2) deduce a diagnostic algorithm based on the findings.

Methods

A total of 37 patients (25 males, 67.6%, mean age 23.9 years, range 8–57 years) with osteoid osteomas of the foot were retrospectively included, treated between 2000 and 2014 at 6 participating tertiary tumor centres. Radiographic images were analyzed, as were patients’ minor and major complaints, pain relief and recurrence.

Results

Most osteoid osteomas were located in the midfoot (n = 16) and hindfoot (n = 14). Painful lesions were present in all but one patient (97.3%). Symptom duration was similar for hindfoot and midfoot/forefoot (p = 0.331). Cortical lesions required fewer x‑rays for diagnosis than lesions at other sites (p = 0.026). A typical nidus could be detected in only 23/37 of x‑rays (62.2%), compared to 25/29 CT scans (86.2%) and 11/22 MRIs (50%). Aspirin test was positive in 18/20 patients (90%), 31 patients (83.8%) underwent open surgery. Pain relief was achieved in 34/36 patients (outcome unknown in one), whilst pain persisted in two patients with later confirmed recurrence.

Conclusions

As previously reported, CT scans seem to be superior to MRIs towards detection of the typical nidus in foot osteoid osteomas. In patients with unclear pain of the foot and inconclusive x‑rays, osteoid osteoma should be considered as differential diagnosis.

A radiological diagnostic approach to tumours and tumour-like lesions of the calcaneus

OBJECTIVE

The calcaneus is a rare location for the development of primary bone tumours. The purpose of the study is to review the imaging findings in a cohort of patients presenting with tumours and tumour-like lesions of the calcaneus and to develop a more structured approach to the diagnosis of calcaneal lesions.

METHODS

A retrospective study with a collection of 167 cases of calcaneal tumours and tumour-like lesions from our tertiary orthopaedic oncology institution over a period of 13 years. Cases were reviewed by two consultant musculoskeletal radiologists and the location of the lesion within the calcaneus and demographics of the patient were noted for each case. A diagnostic algorithm, which is based on patient age and tumour location, was then extrapolated.

RESULTS

Out of the 167 cases, we identified 24 different calcaneal pathologies which included both tumours and tumour-like lesions. The most common being simple bone cysts (18.3% of cases) and intra-osseous lipoma (15% of cases) sited in the diaphyseal equivalent of the calcaneus. A diagnostic algorithm was formulated, which describes the most common location of the different pathologies including both benign and malignant pathologies, subdivided by age.

CONCLUSION

Our algorithm should help the radiologist narrow down the differential diagnosis when evaluating calcaneal lesions.

ADVANCES IN KNOWLEDGE

This article provides a radiological approach to calcaneal lesions.

Osteoid osteoma of the femoral neck mistaken as a synovial herniation pit

A 36-year-old man presented with 1 year of atraumatic left lateral thigh, groin, and hip pain, and imaging consistent with the diagnosis of femoroacetabular impingement and a labral tear. Imaging concurrently demonstrated a synovial herniation pit. The patient underwent hip arthroscopy, which included femoroplasty, acetabuloplasty, labral debridement, and synovectomy. His pain persisted and further workup confirmed an osteoid osteoma that was mimicking a synovial herniation pit. The osteoid osteoma was treated with radiofrequency ablation. At 18 months follow-up, the patient reported complete resolution of his symptoms. We present the case to highlight distinguishing imaging and clinical findings of these similar-appearing lesions. While neither condition is particularly rare individually, the misidentification of osteoid osteoma as a synovial herniation pit is a unique feature of this case that lead to the patient's protracted clinical course.

CT-guided percutaneous radiofrequency ablation of osteoid osteoma: Our experience in 87 patients

Purpose:

To evaluate the technical and clinical success of radiofrequency ablation of osteoid osteoma and analyze the factors responsible for clinical success. We also tried to investigate the role of follow-up computed tomography (CT) imaging.

Materials and Methods:

This is a prospective study approved by the institute's ethics committee involving 87 patients with appendicular osteoid osteoma. CT-guided radio frequency ablation was performed using a bipolar ablation system. Patients were followed up over 15.4 (4–24) months for pain, and clinical success/failure was determined using established criteria. Patients with clinical failure were taken for repeat ablation. Follow-up CT was obtained at 6 months and correlated with clinical success. Procedural scans were later reviewed for technical success in a blinded manner and correlated with clinical success along with other imaging and patient characteristics.

Results:

Mean pre-procedure visual analog scale (VAS) score was 7.0 ± 0.8. Primary success rate after single session was 86.2%(75/87 patients), and overall success rate after one/two sessions was 96.6%(84/87). No major complications were noted. Technical success rate was 89.7%(78/87). All 9 patients who had a suboptimal needle positioning had recurrence where as three patients had recurrence despite technical success. None of the imaging characteristics or history of prior intervention was significantly associated with clinical success. Follow-up CT showed advanced bone healing in 48 lesions, and was confined to the treatment success group. Alternately, minimal/absent bone healing was seen in all (12) patients of primary treatment failure and 27 patients with treatment success.

Conclusions:

CT-guided percutaneous radio frequency ablation is a safe and highly effective treatment for osteoid osteomas even in recurrent and residual cases. Technical success is the most important parameter affecting the outcome. Post radio frequency ablation CT findings have a good positive but a poor negative predictive value in prognostication.

Arthroscopic removal as an effective treatment option for intra-articular osteoid osteoma of the knee

BACKGROUND

Intra-articular osteoid osteoma (iaOO) can be found in 5.2% up to 10% of cases. They may cause non-specific symptoms, mimicking degenerative or traumatic pathologies. If iaOO is left untreated, it may lead to severe muscle atrophy, tenderness, swelling, and limited range of motion. Therefore, surgical treatment is recommended. The main goal of surgical treatment is complete removal or destruction of iaOO.

AIM

To evaluate the efficiency of arthroscopic removal of iaOO of the knee in our cases and cases available in the literature.

METHODS

Analysis of available hospital records of four patients with iaOO of the knee treated by arthroscopic removal from August 2005 to December 2015 at our Department was performed. All patients had a diagnosis of iaOO confirmed by histopathologic analysis. Additional literature review of cases of iaOO of the knee available on PubMed and Google Scholar was made. All cases of iaOO of the knee treated by arthroscopic or arthroscopically assisted removal were reviewed in order to further evaluate the efficiency of the method.

RESULTS

The average age of patients included in our study was 23.2 (range 16-37) years. The average duration of the symptoms prior to surgery was 14.2 (range 6-24) months. All of the patients had persistent knee pain. Three patients reported worsening of pain during the night, while two reported worsening of pain during activity. Three patients reported alleviation of pain on non-steroidal anti-inflammatory drugs (NSAIDs), while one patient reported partial alleviation of pain on NSAIDs. No intraoperative complications were noted, and the postoperative period was uneventful in all patients. The patients reported immediate pain relief in the postoperative period. No recurrence of the disease was noted in any of the patients during the follow-up period of at least 24 mo. The literature review revealed 14 cases with an average age of 27.6 (range 16-48) years and onset of symptoms 27.7 (range 6-108) months prior to surgery, with recurrence of the disease noted in a single case.

CONCLUSION

Arthroscopic removal is an efficient treatment method that allows excision of iaOO that is neither insufficient nor excessive, thus avoiding disease recurrence while obtaining adequate material for histopathologic analysis.

PET/CT Normal Variants and Pitfalls in Pediatric disorders

18F- Fluoro-deoxyglucose positron emission computed tomography (18F-FDG PET CT) is an established modality used mainly in oncology. Though it has widespread oncologic indications, it is not tumor specific. Apart from the physiological distribution, uptake of FDG may be seen in many benign conditions, including infection and inflammation in children and adults. Performing and acquiring a technically adequate PET CT study may be more challenging in children. Proper preparation and an acceptable imaging protocol will help to avoid re-acquisition and in minimizing the radiation exposure. Sound knowledge of the physiological variants and benign conditions that are specific to the pediatric population will aid in correct interpretation of the PET CT study. It is important that radiologists and Nuclear Medicine physicians who report these studies are well-acquainted with these pitfalls to avoid false positive studies.

Challenges in the Interpretation of MRI Examinations Without Radiographic Correlation: Pearls and Pitfalls to Avoid

As physics introduces more complex and seemingly thorough techniques to evaluate patient symptoms, cross-sectional imaging, especially magnetic resonance imaging (MRI), seems like the modality of choice to best help patients. However, musculoskeletal radiology (MSK) requires not just the excellent soft-tissue contrast provided by MRI but also an evaluation of the aggressiveness of a lesion, a detailed evaluation of osseous anatomy or distribution of disease, and a way to easily identify calcifications and gas in soft tissue in order to make the correct diagnosis. This article will demonstrate, through numerous cases, the importance of radiographs in the full characterization of MSK-related pathology. It will focus on imaging pearls and pitfalls to avoid when radiographs are not available and discuss the findings that can be expected if comparison radiographs were available.

Osteoid Osteoma: An Updated Review of Epidemiology, Pathogenesis, Clinical Presentation, Radiological Features, and Treatment Option

Osteoid osteoma, the third most common benign bone tumor, usually occurs in the cortex of long bones. It consists of a radiolucent nidus surrounded by reactive osteosclerosis. Generally, osteoid osteoma affects young males. Nocturnal pain that eases with salicylates or nonsteroidal anti-inflammatory drugs (NSAID) is the typical clinical presentation. Sometimes, it remains undiagnosed for a long time. Plain radiography and computed tomography are usually sufficient for the diagnosis of osteoid osteoma. Initial treatment includes salicylates and NSAID because the tumor often regresses spontaneously over 2-6 years. Surgical treatment is indicated in case of unresponsive pain to medical therapy, no tolerance of prolonged NSAID therapy due to side effects, and no willingness to activity limitations. Nowadays, minimally invasive techniques have replaced open surgery and are considered the gold standard of surgical treatment. Although cryoablation seems superior in terms of the nerve damage and immunotherapy effect, radiofrequency ablation is the preferred technique.

US Guided Si.La.D. A new technique for minimally invasive pilonidal disease treatment, using ultrasound guided laser ablation

Background: The destruction of the pilonidal sinus with a radial laser probe has been suggested as a safe procedure with good results and low morbidity. Nevertheless, the drawbacks of this technique are: a blind technique, if the sinus has some ramifications or a non-linear development, we cannot be sure for their destruction.Methods: 17 patients (12 men, 5 women) were operated with US guided laser destruction - US guided Si.La.D. Laser destruction of the pathological tissue (cavity, sinus) was performed using a 400 μ radial optical fiber, connected and locked to a radiopaque biopsy needle 14 G, using a 12 MHz linear probe, to introduce and real-time echo guide the fiber in order to achieve laser ablation with 120-140 J /cm of pathological tissueResults: No significant complications were recorded.Conclusion: Real-time echo guided laser ablation of pilonidal sinus and cavities proved to be safe and efficient, providing controlled emission of laser energy only to the pathological tissue, increasing the accuracy of identify the right track to deliver energy, decreasing the risk of traumatic progression of surgical instrument into healthy subcutaneous tissue, accidental progression of the disease and missing in the same time tracts that need to be ablate.

Skull Imaging-Radiographs and CT revisited

Although rare, skull vault lesions include a vast array of pathology encompassing infection, benign, and malignant bone tumors. Given the large range of potential diagnoses, it is crucial to identify imaging features to differentiate one from another, ensuring early diagnosis. Radiographs are still valuable in modern radiology but have largely been superseded by computed tomography (CT) due to its high spatial resolution. Both are especially important in developing countries where access to magnetic resonance imaging (MRI) may be limited.There are currently several publications outlining imaging appearances of skull vault lesions. However, the majority of literature is dated, with the last dedicated textbook published in 1980 (Principles of X-ray diagnosis of the skull). Despite overlapping features, a few lesions have "aunt minnie," type classical characteristics, which we will highlight. Most vault lesions also appear as a spectrum depending on location and the exact stage of the disease. A small subset within each disease entity also has atypical features not widely discussed in the current literature. In this pictorial review, we hope to focus on radiographic and CT imaging appearances to help differentiate between various skull vault lesions.

A Rare Case of Intra-Articluar Osteoid Osteoma of the Elbow Managed With Arthroscopic Excision

Osteoid osteoma (OO) of the elbow is a very rare entity as it typically occurrs in the lower extremity of extra-articular long bones. Hereby, we report a case for a 28-year-old female patient has been diagnosed with a unique presentation of sub-periosteal osteoid osteoma in the intra-articular portion of distal humerus. She underwent arthroscopic excision for the lesion which is considered a reliable minimally invasive management modality. In addition to this, findings of a 1-year follow-up after excision is reported.

Incidental Skeletal Findings on Sodium-fluoride Positron Emission Tomography: A Collection of Benign Tumors

Sodium-fluoride (NaF) positron emission tomography (PET) is a sensitive method to detect altered bone mineralization. Its increasing use in routine clinical practice for metastatic bone disease has also resulted in the detection or characterization of incidental benign bone lesions. A spectrum of NaF PET scan cases with benign bone tumors are presented in this article, including whole body PET bone scan and selected PET/computed tomography (CT), CT, or magnetic resonance imaging (MRI) of the region of interest. The reader will be able to improve their knowledge related to the clinical presentation of these entities, some are rare and recognize based on NaF PET and CT/MRI patterns by reviewing these cases.

Radiologic Mimics of Osteomyelitis and Septic Arthritis: A Pictorial Essay

Various imaging techniques may be employed in the investigation of suspected bone and joint infections. These include ultrasound, radiography, functional imaging such as positron emission tomography (PET) and nuclear scintigraphy, and cross-sectional imaging, including computed tomography (CT) and magnetic resonance imaging (MRI). The cross-sectional modalities represent the imaging workhorse in routine practice. The role of imaging also extends to include assessment of the anatomical extent of infection, potentially associated complications, and treatment response. The imaging appearances of bone and joint infections are heterogeneous and depend on the duration of infection, an individual patient's immune status, and virulence of culprit organisms. To add to the complexity of radiodiagnosis, one of the pitfalls of imaging musculoskeletal infection is the presence of other conditions that can share overlapping imaging features. This includes osteoarthritis, vasculopathy, inflammatory, and even neoplastic processes. Different pathologies may also coexist, for example, diabetic neuropathy and osteomyelitis. This pictorial review aims to highlight potential mimics of osteomyelitis and septic arthritis that are regularly encountered, with emphasis on specific imaging features that may aid the radiologist and clinician in distinguishing an infective from a noninfective aetiology.

Primary Tumors of the Sacrum: Imaging Findings

The diagnosis of sacral neoplasms is often delayed because they tend to remain clinically silent for a long time. Imaging is useful at all stages of managing sacral bone tumors: from the detection of the neoplasm to the long-term follow-up. Radiographs are recommended as the modality of choice to begin the imaging workup of a patient with known or suspected sacral pathology. More sensitive examinations such as computerized tomography (CT), magnetic resonance (MRI), or scintigraphy are often necessary. The morphological features of the lesions on CT and MRI help to orientate the diagnosis. Although some imaging characteristics are helpful to limit the differential diagnosis, an imaging-guided biopsy is often ultimately required to establish a specific diagnosis. Imaging is of paramount importance even in the long-term follow-up in order to assess any residual tumor when surgical resection is incomplete, to assess the efficacy of adjuvant chemotherapy and radiotherapy, and to detect recurrence.