Aims. The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI. Methods. Periprosthetic femoral trabecular bone specimens were obtained from patients suffering from chronic PJI of the hip and knee (n = 20). Microbiological analysis was performed on preoperative joint aspirates and tissue specimens obtained during revision surgery. Microstructural and cellular bone parameters were analyzed in bone specimens by histomorphometry on undecalcified sections complemented by tartrate-resistant acid phosphatase immunohistochemistry. Data were compared with control specimens obtained during primary arthroplasty (n = 20) and aseptic revision (n = 20). Results. PJI specimens exhibited a higher bone volume, thickened trabeculae, and increased osteoid parameters compared to both control groups, suggesting an accelerated bone turnover with sclerotic microstructure. On the cellular level, osteoblast and osteoclast parameters were markedly increased in the PJI cohort. Furthermore, a positive association between serum (CRP) but not synovial (white blood cell (WBC) count) inflammatory markers and osteoclast indices could be detected. Comparison between different pathogens revealed increased osteoclastic bone resorption parameters without a concomitant increase in osteoblasts in bone specimens from patients with Staphylococcus aureus infection, compared to those with detection of Staphylococcus epidermidis and Cutibacterium spp. Conclusion. This study provides insights into the local bone metabolism in chronic PJI, demonstrating osteosclerosis with high bone turnover. The fact that Staphylococcus aureus was associated with distinctly increased osteoclast indices strongly suggests early surgical treatment to prevent periprosthetic bone alterations. Cite this article: Bone Joint Res 2023;12(10):644–653

Introduction. Ascertaining the etiology of hip pain in young patients can be challenging. Osteoid osteoma about the hip has only been described in case reports and small case series in this sub-population. This study assessed the clinical course, radiologic findings, and treatment approaches in a large series of pediatric osteoid osteoma cases about the hip. Potential diagnostic and treatment pitfalls were identified. Methods. A single-center tertiary care departmental database was queried for all cases of osteoid osteoma seen between Jan 1, 2003 and December 31, 2015. Medical records were reviewed to identify those with lesions identified within or around the hip joint. Clinical, demographic, and radiologic data were analyzed. Results. Fifty children and adolescents (56% female, mean age 12.4 years, range 3–19 years) were identified with osteoid osteoma about the hip. The femoral neck was the most common lesion location (38%), and pain in the hip was the most common presenting chief complaint (60%). Night pain (90%) and symptom relief with NSAIDs (88%) were extremely common, though not universally reported. Sclerosis and/or cortical thickening was visible in 58% of radiographs, though a lucent nidus was visible in only 42%. Thirty patients (60%) underwent MRI, 27 of which were available for review, with focal peri-lesional edema as a universal finding. Amongst intracapsular lesions (n=17, 63%), common findings included medial retinacular thickening (33%), synovitis (45%) and effusion (76%). In the 43 patients (48%) who underwent CT, a diagnostic lucent nidus was a universal finding. Initial alternative diagnoses were recorded in 46% of cases, including, in order of decreasing frequency, femoro-acetabular impingement, minor trauma, hip synovitis, ‘growing pain’, stress fracture, and infection. Abnormal hip range of motion, positive impingement signs, and global synovitis on MRI scan were found to be associated with alternative diagnosis. On multivariate regression analysis, only abnormal hip ROM was independently predictive of alternative diagnosis. Delay in diagnosis of >6 months was seen in 43% of patients. Three patients underwent preceding operative procedures for other hip diagnoses, but had persistent hip pain until the osteoid osteoma was treated. Forty-one patients (82%) ultimately underwent radiofrequency ablation (RFA), and 1 open osteoid osteoma resection was performed. Of those who underwent RFA, 93% achieved complete symptom resolution, with 2 of 3 patients without symptom resolution undergoing revision RFA procedure, 1 of which led to symptom resolution. Complications of treatment included 1 case of deep infection along an RFA track, requiring operative debridement, 1 case of transient weakness and paresthesias in the involved extremity, and 1 case of fracture at the RFA site, requiring ORIF. Conclusions. Alternative andelayed diagnoses are common in osteoid osteoma about the hip, with femoro-acetabular impingement representing the most common alternative initial diagnosis in our series. While varying presenting complaints and nonspecific MRI findings may contribute to diagnostic uncertainty, night pain was present in the vast majority of cases and CT scans provided definitive diagnosis in all patients who received them. As increasing numbers of young, active patients are being evaluated for various causes of hip pain, such as femoro-acetabular impingement, osteoid osteoma should not be overlooked in the differential diagnosis of pain about the hip

Aims. Venous tumour thrombus (VTT) is a rare finding in osteosarcoma. Despite the high rate of VTT in osteosarcoma of the pelvis, there are very few descriptions of VTT associated with extrapelvic primary osteosarcoma. We therefore sought to describe the prevalence and presenting features of VTT in osteosarcoma of both the pelvis and the limbs. Methods. Records from a single institution were retrospectively reviewed for 308 patients with osteosarcoma of the pelvis or limb treated between January 2000 and December 2022. Primary lesions were located in an upper limb (n = 40), lower limb (n = 198), or pelvis (n = 70). Preoperative imaging and operative reports were reviewed to identify patients with thrombi in proximity to their primary lesion. Imaging and histopathology were used to determine presence of tumour within the thrombus. Results. Tumours abutted the blood vessels in 131 patients (43%) and encased the vessels in 30 (10%). Any form of venous thrombus was identified in 31 patients (10%). Overall, 21 of these thrombi were determined to be involved with the tumour based on imaging (n = 9) or histopathology (n = 12). The rate of VTT was 25% for pelvic osteosarcoma and 1.7% for limb osteosarcoma. The most common imaging features associated with histopathologically proven VTT were enhancement with contrast (n = 12; 100%), venous enlargement (n = 10; 83%), vessel encasement (n = 8; 66%), and visible intraluminal osteoid matrix (n = 6; 50%). Disease-specific survival (DSS) for patients with VTT was 95% at 12 months (95% CI 0.87 to 1.00), 50% at three years (95% CI 0.31 to 0.80), and 31% at five years (95% CI 0.14 to 0.71). VTT was associated with worse DSS (hazard ratio 2.3 (95% CI 1.11 to 4.84). Conclusion. VTT is rare with osteosarcoma and occurs more commonly in the pelvis than the limbs. Imaging features suggestive of VTT include enhancement with contrast, venous dilation, and vessel encasement. VTT portends a worse prognosis for patients with osteosarcoma, with a similar survivability to metastatic disease. Cite this article: Bone Joint J 2024;106-B(8):865–870

This study was designed to be the first to prospectively evaluate CT-guided radiofrequency ablation for osteoid osteoma in terms of pain control, medication consumption, quality of life and patient function. Over two years, forty patients with symptoms and radiographic findings classic for osteoid osteoma were offered radioablation. Patients were asked to fill out facial, subjective and visual analog pain scales and to undergo the Musculoskeletal Tumour Society 1987 functional assessment. Results show immediate and lasting resolution of symptoms, a sharp drop in drug use and a significant improvement in function thus supporting the role of radioablation as first line therapy. The purpose of this study was to prospectively evaluate the usefulness of radioablation for osteoid osteoma in terms of pain control, analgesic drug consumption, quality of life and patient function. Radioablation appears to be a safe and effective method of treatment for osteoid osteoma. It offers immediate and lasting resolution of symptoms. Results support its role as first line therapy. This is the first study to prospectively measure the outcome of patients treated with CT-guided radiofrequency ablation for osteoid osteoma. The mean follow-up time is 6.93 months (sd: 6.51). All but seven procedures were done under regional anaesthesia. No complications were reported. 50% of core biopsy specimens were diagnostic of osteoid osteoma. The visual analog pain scale showed a value of 2.13(sd: 2.5) pre-op and 0.33(sd: 1.07) at 1 year (p=0.00033). The MSTS score rose from 28.86(sd: 4.68) pre-operatively to 34.06(sd: 1.95) after one year (p=0.000000049). Medication consumption was markedly reduced. All eighteen patients with more than one- year follow-up are drug free. Over two years, forty patients with symptoms and radiographic findings classic for osteoid osteoma who had already received various treatments were offered radioablation. Written consent was obtained and patients were asked to fill out facial, subjective and visual analog pain scales. The Musculoskeletal Tumour Society 1987 functional assessment was performed. This data was collected two weeks prior to treatment and then at two weeks, three months and one year after treatment. The procedure was performed under CT guidance and on a one-day hospital admission basis

Intraarticular osteoid osteomas account for approximately 13% of osteoid osteomas. The hip is the commonest location of intraarticular osteoid osteomas. We present 16 patients with intra-articular osteoid osteomas of the hip treated with RFA. These were 13 men and 3 women, with a mean age of 27 years (range, 16–48 years). Eight osteoid osteomas were located in the femoral head, 6 in the femoral neck, and 2 in the acetabulum. The approximate mean duration of the procedure was 82 min (range, 50–125 min). The mean hospitalization time was 8.7 h (range, 6–12 h). All patients had pain improvement within the first 24 h. Five patients had pain relief within the first 3 days, 9 patients within the first week, and 2 patients within 2 weeks post-procedural. Twelve patients continued to have some restriction of their physical activities up to one month after the operation. All patients returned to their previous status of physical activity within the first 2 to 3 months post-procedural. At the latest follow-up, there were no residual or recurrent symptoms. Five patients complained for mild pain, which was probably due to hip synovitis that resolved within a week. One patient experienced transient paresthesias and pain in the buttock at the site of the trocar and electrode insertion. Intra-articular osteoid osteomas have clinical and imaging features significantly different from those seen in extra-articular lesions. CT-guided percutaneous RFA is a simple minimally invasive, safe and effective method for most intra-articular osteoid osteomas

Purpose: Osteoid osteoma is a benign small-sized painful osteoblastic tumour usually observed in young subjects. The purpose of this work was to study the epidemiological, clinical, radiological, and histological features, focusing on clinical course after treatment and differences by location. Material and methods: We report a retrospective series of 56 osteoid osteomas located in limbs treated over a 25-year period from 1976 to 2001. The tumour involved the femur (n=21), the tibia (n=14), the hand (n=8), the foot (n=7), and the olecranon, the lateral humeral condyle, the humeral neck, and the acetabulum (n=1 each). Pain was the pain symptom, found in all patients. The aspirin test was positive in 82%. The joint locations led to an arthropathy in 87%. The typical nidus aspect was found on 78.5% of the plain x-rays. Computed tomography was performed in 25 patients and scintigraphy in 10. Magnetic resonance imaging was performed in 4. Surgical treatment consisted in en bloc resection (n=48), intra-lesions curettage (n=6), computed tomography-guided percutaneous resection (n=2). Mechanical protection was obtained with a plaster cast (n=21) and osteosynthesis material (n=7). A bone graft was used in 22 patients. Pathology confirmed osteoid osteoma in all patients. Lymphocyte plasma cell infiltrations were observed in seven of the articular localisations. Results: Mean follow-up was 5 years. Complete pain relief was achieved after a single resection in 53 patients and after re-operation of a second resection in the others. For the joint localisations, complete joint movement was recovered in three-quarters of the patients. Postoperative x-rays were performed in all cases. The main early complications were iatrogenic fracture (9%), mainly in patients with a tibial tumour. Late complications included osteoarthritis for the acetabular tumour and two cases of talal degeneration. Conclusion: Osteoid osteoma is an uncommon tumour general easy to recognise. Atypical clinical and radiological presentations are rare. Computed tomography is the key to diagnosis and provides important therapeutic information

We describe 100 consecutive patients with osteoid osteoma. Of the 97 who had operations, 89 were treated by intralesional excision and eight by wide resection. The three remaining patients were not operated on because the osteoid osteoma was almost painless, or was found in the pedicle of the 12th thoracic vertebra at the site of entrance of the artery of Adamkjewicz. The diagnosis was confirmed histologically in all specimens. No local recurrences were observed at a minimum follow-up of one year. All except one patient were mobilised two to four days after surgery. A precise preoperative diagnosis of the lesion is mandatory, based on clinical findings, standard radiographs, thin-section CT and a bone scan. We compared our operative technique with 247 cases in which the percutaneous technique of removal or coagulation of the nidus had been performed. The latter procedure has a less constant rate of primary cure (83% v 100%). Its principal indication appears to be for osteoid osteomas in the proximal femur and the pelvis

Radiofrequency ablation (RFA) is a relatively new technique to produce cell death by radiowaves (460– 480 kHz) caused by an alternating current emitted from the tip of a needle electrode and causing local ions vibration producing heat. In orthopaedic fields RFA has been proposed for the treatment of osteoid osteoma and painful metastases. Methods: 121 patients with a clinical and radiographic accerted osteoid osteoma have been treated with percutaneous radiofrequency ablation at our institutions from 1998 till December 2005. Average age of the patients was 23 years. Preoperative symptoms lasted 10 months on average. The osteoid osteoma was localized at the limbs in 111 cases, at the pelvis in 4 cases and at the spine in 6 cases. Results: At follow up we had 3 cases of recurrences and 2 fair results with a total of 5 unsuccessful cases. The fair results were due to a mistake of radiological indication and one case of ineffectively ablation. We observed 3 cases of skin burns in tibia with superficial infections: 2 cases resolved without treatment while the latter case showed initial bone infection and needed surgical revision. Conclusion: Percutaneous RFA of osteoid osteoma proved to be a successful treatment in more than 95% of the cases with a low complication rate

Study Design. Prospective cohort study. Objective. To assess the safety and efficacy of an intra-operative gamma probe in the surgical treatment of osteoid osteomas and osteoblastomas arising from the spine. Summary of background data. Spinal osteoid osteomas and osteoblastomas are difficult to localise and may present adjacent to neural structures. Complete surgical excision of the nidus is a pre-requisite for curative resection. Methods. All patients with a presumptive diagnosis of osteoid osteoma or osteoblastoma were investigated with plain radiography, computed tomography, magnetic resonance imaging and a technitium bone scan. Nine patients underwent surgical excision. 600 MBq of 99m technitium HMDP was administered intravenously three hours prior to surgery. A sterile cadmium telluride detector connected to a digital counter/ratemeter was used to detect gamma radiation emitted by the tumour intra-operatively to assist with localisation and confirmation of complete excision. Results. Between October 1995 and September 2006, nine patients required surgical excision for seven osteoid osteomas and two osteoblastomas arising from the spine. All patients were between the ages of 9-31 years and presented with back or neck pain. All tumours involved the posterior elements of the spine. Three patients had previous failed treatment including CT-guided radiofrequency ablation and surgical excision. In all cases the counts per second (cps) dropped significantly following excision. Histological examination confirmed complete excision in all cases. The mean follow-up was 4.5 years (range 0.5-11 years). All patients reported disappearance of the characteristic pre-operative pain. Conclusions. The use of an intra-operative gamma probe helps to localise and confirm complete excision of osteoid osteoma and osteoblastoma arising from the spine. Accurate localisation results in safe excision with maximal conservation of surrounding normal bone, whilst minimising operative time, blood loss, hospital stay and risk of recurrence

Study Design: Prospective cohort study. Objective: To assess the safety and efficacy of an intra-operative gamma probe in the surgical treatment of osteoid osteomas and osteoblastomas arising from the spine. Summary of background data: Spinal osteoid osteomas and osteoblastomas are difficult to localise and may present adjacent to neural structures. Complete surgical excision of the nidus is a pre-requisite for curative resection. Methods: All patients with a presumptive diagnosis of osteoid osteoma or osteoblastoma were investigated with plain radiography, computed tomography, magnetic resonance imaging and a technitium bone scan. Nine patients underwent surgical excision. 600 MBq of 99m technitium HMDP was administered intravenously three hours prior to surgery. A sterile cadmium telluride detector connected to a digital counter/ratemeter was used to detect gamma radiation emitted by the tumour intra-operatively to assist with localisation and confirmation of complete excision. Results: Between October 1995 and September 2006, nine patients required surgical excision for seven osteoid osteomas and two osteoblastomas arising from the spine. All patients were between the ages of 9–31 years and presented with back or neck pain. All tumours involved the posterior elements of the spine. Three patients had previous failed treatment including CT-guided radiofrequency ablation and surgical excision. In all cases the counts per second (cps) dropped significantly following excision. For the osteoid osteoma cases, the mean cps dropped from 203.8 (range 60–515) to 72.5 cps (range 10–220) post-excision. For the osteoblastoma cases the mean cps dropped from 373.5 (range 67–680) to 40.5 cps (range 16–65) post-excision. Histological examination confirmed complete excision in all cases. The mean follow-up was 4.5 years (range 0.5 – 11 years). All patients reported disappearance of the characteristic pre-operative pain. Conclusions: The use of an intra-operative gamma probe helps to localise and confirm complete excision of osteoid osteoma and osteoblastoma arising from the spine. Accurate localisation results in safe excision with maximal conservation of surrounding normal bone, whilst minimising operative time, blood loss, hospital stay and risk of recurrence

The recognition, investigation and management of osteoid osteoma has been well documented. Treatment can either be medical or surgical, studies have shown both options to have almost equal long term outcomes. However only surgical treatment involving complete excision of the lesion allows for confirmatory tissue diagnosis of osteoid osteoma especially important in cases where symptoms and signs are atypical. Several methods of surgical treatment with varying degrees of success have been described in literature. Here we describe a surgical techniques for the treatment of osteoid osteoma which enables removal of the lesion in a precise manner using a precision bone graft trephine with minimal excision of bone. This technique will be very useful in the excision of lesions in areas in which excessive excision of bone can lead to an unstable bony structure which can predispose to fracture. To our knowledge this surgical technique in the management of osteoid osteoma has not been described in the literature

Osteoid osteoma is a benign bone-forming lesion, characterized by its small size, its clearly demarcated outline and by the usual presence of a surrounding zone of reactive bone formation. It often poses a diagnostic challenge due to its ambiguous presentation. The aetiology of osteoid osteoma is poorly understood. The previous suggestion that osteoid osteoma was not associated with trauma or infection has been challenged by more recent literature raising the possibility that it could be a reactive or healing response or a phenomenon associated with the revascularisation process. This case report describes an unusual presentation of a post-traumatic osteoid osteoma. Two years following a diaphyseal, spiral tibial fracture treated nonoperatively, the patient developed new pain at the previous fracture site. The pain was constant, relieved by non-steroidal analgesia and not associated with systemic upset. It was initially attributed to other more likely diagnoses such as osteomyelitis and neuropathic pain. Multiple investigations and interventions were undertaken prior to the definitive diagnosis being obtained by surgical excision of the lesion and histological studies five years after the injury and three years following the initiation of the discomfort. In both English and foreign language literature there are only seven case reports that document osteoid osteoma following fracture, these are predominantly in the lower limb with no predominance to operative or nonoperative management. This case report should raise the index of clinical suspicion of osteoid osteoma occurring post fracture

The aim of our study is to present osteoid osteoma as a disease in preschool children. O O is a benign inflammatory process that is characterized from osteoid formation. It appears mainly in the second and third decade of life, while before 5 years of age usually as case reports. The clinical and radiological presentation must be differentiated from trauma, osteomyelitis, malignancy and other benign diseases. We present three patients, aged ranging from 18 months to 4 years old, that were treated surgically for the removal of O O in the tibia and fibula. All patients presented with limping, pain mainly in the night, gradual restriction of activities. The clinical, hematological and radiological investigation revealed the general aspects of the disease. Bone scans were positive in all. CT scan confirmed the diagnosis in all three patients. Surgical treatment was done with fluoroscopic assistance, in order to remove the minimum possible amount of bone. In two patients the lesion was located in the distal metaphysis of the tibia and in one in the distal metaphysis of the fibula. The diagnosis was confirmed with the typical nidus, in pathological specimens. In one patient the lesion was intracortical and in two in the medullary area. Despite the ages of our patients, there were not misleading findings, in the specimens. After surgery the patients were symptoms free, and with 1–4 years follow up, there are no recurrences. We conclude that osteoid osteoma must be included in the differential diagnosis, in cases of pain and limping, in preschool children

Osteoid osteoma is a benign bone tumor usually observed in children and adults, generally in the femur or tibia. Pain relief with aspirin is a classical clinical characteristic. Computed tomography is the exploration of choice providing reliable diagnosis. Cure can be achieved with surgical resection. We present an exceptional case of osteoid osteoma located in the patella

1. A case of osteoid osteoma of the skull is reported, with characteristic clinical, radiological and pathological features. 2. Osteoid osteoma of the skull has not previously been reported

The primary aim of this study was to compare the clinical outcomes of osteoid osteoma (OO) between the group of patients with the presence of nidus on biopsy samples from radiofrequency ablation (RFA) with those without nidus. Secondly, we aimed to examine other factors that may affect the outcomes of OO reflecting our experience as a tertiary orthopaedic oncology centre. We retrospectively reviewed 88 consecutive patients diagnosed with OO treated with RFA between November 2005 and March 2015, consisting of 63 males (72%) and 25 females (28%). Sixty-six patients (75%) had nidus present in their biopsy samples. Patients’ mean age was 17.6 years (4-53). Median duration of follow-up was 12.5 months (6-20.8). Lesions were located in the appendicular skeleton in seventy-nine patients (90%) while nine patients (10%) had an OO in the axial skeleton. Outcomes assessed were based on patients’ pain alleviation (partial, complete, or no pain improvement) and the need for further interventions. Pain improvement in the patient group with nidus in histology sample was significantly better than the group without nidus (OR 7.4, CI 1.35-41.4, p=0.021). The patient group with nidus on biopsy demonstrated less likelihood of having a repeat procedure compared to the group without nidus (OR 0.092, CI 0.016-0.542, p=0.008). Our study showed significantly better outcomes in pain improvement in appendicular lesions compared to the axially located lesions (p = 0.005). Patients with spinal lesions tend to have relatively poor pain relief than those with appendicular or pelvic lesions (p=0.007). Patients with nidus on histology had better pain alleviation compared to patients without nidus. The histological presence of nidus significantly reduces the chance of repeat interventions. The pain alleviation of OO following RFA is better in patients with appendicular lesions than spinal or axially located lesions

Osteoid osteoma is a classically described benign bone tumour. Traditionally, the surgical treatment of choice was excision, but this can have significant morbidity. In recent years, percutaneous Radiofrequency Ablation (RFA) has grown in popularity as an alternative treatment. This study reports the outcomes using this technique in our regional bone tumour unit. Between May 2003 and October 2007, 14 patients (female, n=4; male, n = 10) aged 15 - 32yrs (mean age, 20.4yrs) underwent CT guided radiofrequency ablation treatment. These patients had typical radiograph, CT, MRI or isotope bone scan features of osteoid osteoma and had significant pain symptoms. The protocol for ablation in our institute is heating the tip of the electrode to 90°C for 6 minutes. All patients were subsequently offered follow up in the out-patient clinic. Outcomes were taken from the Scottish Bone Tumour Registry database. 11 patients (78.6%) patients had complete resolution of symptoms after one RF treatment. 3 (21.4%) cases were unsuccessful but 1 of these was due to technical failure. All 3 of the above patients had complete relief of symptoms after one further RF treatment. 1 (7.1%) patient initially had complete relief of symptoms, but suffered a recurrence after 9 months. This patient also had a second curative treatment. Follow up ranged from 3 – 18 months (mean 10 months). Percutaneous RFA for osteoid osteoma is an attractive treatment due to its efficacy and low morbidity. Our results showed a primary success rate of 78%, a secondary success rate of 100% (after one additional procedure) and a recurrence rate of 7.1%. These are comparable to previous reported series. We believe our results add to the growing literature supporting radiofrequency ablation as the treatment of choice for osteoid osteoma

Subperiosteal osteoid osteoma in a juxta-articular site presents a diagnostic challenge. The clinical features of joint stiffness, synovitis, muscle atrophy and local warmth may suggest arthritis rather than osteoid osteoma, while radiographs, bone scans and angiograms may not be diagnostic. We describe four cases of this rare condition

Introduction: Osteoid Osteomas are not uncommon, benign bone tumours which have well-defined clinical, radiological and pathological characteristics. These tumours can potentially affect any bone in the body, but show a predilection for long tubular bones. The clinical presentation can easily be confusing, if the site in question is rare and the presentation atypical. Lesions occurring in the foot often pose particular problems in diagnosis, often leading to delays in treatment. Although there have been accounts of the post traumatic presentations of osteoid osteomas, no direct link has been established between trauma and its incidence. Case Report: A 38 year old gentleman was referred by his GP with an eighteen month history of right midfoot pain after a football injury which forced his right foot into hyperextension and abduction. Initial radiographs after the injury were normal. The pain did not respond to non-steroidal anti-inflammatory drugs (NSAIDs) and there were no nocturnal exacerbations. Examination at presentation showed an antalgic gait with medial mid-foot tenderness centred over the first tarso-metatarsal joint (TMTJ). Repeat radiographs showed mild degenerative changes in the first TMTJ. A bone scan showed a hot spot over the right cuneiform bones. Subsequent computed tomography (CT) showed an osteoid osteoma, with a characteristic central calcific nucleus within the nidus, of the medial border of the lateral cuneiform bone. The osteoma was treated with en-bloc excision and the diagnosis was confirmed by histology. Conclusion: Despite the advances in its treatment, osteoid osteoma of the foot can pose a difficult diagnostic puzzle. This condition should always be kept in mind when faced with persistent, post-traumatic foot pain, even in the absence of roentgenographic findings. In such cases a high index of suspicion and a low threshold for appropriate imaging can lead to the timely diagnosis and treatment of this tumour

Introduction. CT guided percutaneous radiofrequency thermo coagulation is the treatment of choice for osteoid osteomas. Good results with a low complication rate have been shown for spinal lesions. When lesions are within close proximity to neurological structures or if patients have radicular symptoms surgery rather than radiofrequency ablation has been advocated. We present our experience of radiofrequency ablation of spinal osteoid osteomas which are less than 5mm from neurological structures, including those causing radicular symptoms. Methods. Data was collected prospectively on all patients with a spinal osteoid osteoma within 5mm of nerve roots or the spinal cord as measured on CT scanning. There were nine patients, five female and four males. Four were located in the thoracic spine, three in the lumbar spine and two in the cervical spine. The mean distance to the nearest neurological structure was 3mm. Radicular symptoms were present in two patients. The mean number of probe positions used was two. Lesions were heated to 90 degrees for 5 minutes for each probe position. There were two cases of recurrence, both treated successfully with one further procedure each. There were no cases of neurological injury. The two patients with radicular symptoms had full resolution of their symptoms. At a mean follow up of 2 years following treatment all patients are asymptomatic. Conclusion. Radiofrequency ablation can be safely performed to treat osteoid osteomas located within 5mm of neurological structures and has a low rate of recurrence