Osteoid osteoma is a benign bone-forming tumor with hallmark of tumor cells directly forming mature bone. Osteoid osteoma accounts for around 5% of all bone tumors and 11% of benign bone tumors with a male predilection. It occurs predominantly in long bones of the appendicular skeleton. According to Musculoskeletal Tumor Society staging system for benign tumors, osteoid osteoma is a stage-2 lesion. It is classified based on location as cortical, cancellous, or subperiosteal. Nocturnal pain is the most common symptom that usually responds to salicyclates and non-steroidal anti-inflammatory medications. CT is the modality of choice not only for diagnosis but also for specifying location of the lesion, i.e. cortical vs sub periosteal or medullary. Non-operative treatment can be considered as an option since the natural history of osteoid osteoma is that of spontaneous healing. Surgical treatment is an option for patients with severe pain and those not responding to NSAIDs. Available surgical procedures include radiofrequency (RF) ablation, CT-guided percutaneous excision and en bloc resection.

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Osteoid osteoma: Contemporary management.

Image-guided percutaneous microwave ablation has been used to treat adult osteoid osteomas but has not been thoroughly evaluated in the pediatric population. To evaluate the technical feasibility and clinical efficacy of microwave ablation to treat osteoid osteomas in pediatric patients. The electronic medical record and imaging archive were reviewed for 24 consecutive patients who had undergone microwave ablation of osteoid osteomas between January 1, 2015, and May 31, 2018, at a single tertiary care pediatric hospital. All patients were diagnosed by clinical and imaging criteria, and referred by a pediatric orthopedic surgeon after failing conservative management with pain medication. The average age of the patients was 13.3 years (range: 3–18 years), and the average size of the osteoid osteoma nidus was 8.8 mm (range: 5–22 mm). Technical success was defined as placement of the microwave antenna at the distal margin of the lesion nidus and achievement of the target ablation temperature. Clinical findings were assessed pre- and post-ablation and clinical success was defined as complete relief of pain without pain medication at 1-month follow-up. The number and severity of complications were also documented. Clinical success was achieved in 100% of patients (24/24), with all reporting complete cessation of pain medication use 1 week after treatment and 0/10 pain at 1 month. There were 4 minor complications (17%) including access site numbness and a minor soft-tissue infection. There were no major complications. Microwave ablation is a technically feasible and clinically effective treatment for pediatric osteoid osteomas.

Microwave ablation of osteoid osteoma: initial experience and efficacy.

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

Although radiofrequency ablation is well validated for treatment of osteoid osteoma, newer technologies, namely cryoablation, have been less thoroughly studied. The purpose is to perform a systematic review and pooled analysis of percutaneous ablation technologies for treatment of osteoid osteoma with subset analysis of intra-articular and spinal tumors. A total of 36 of 79 identified manuscripts met inclusion criteria, comprising 1863 ablations in 1798 patients. Inclusion criteria were (1) retrospective or prospective analysis of thermal ablation of osteoid osteomas in any location, (2) at least 6 months of clinical follow-up, (3) 10 or more patients, (4) patients not included in a second study included in this review, and (5) English language or English translation available. Success rate was defined as all ablations minus technical failures, clinical failures, and recurrences. Subset analysis of intra-articular and spinal tumors was performed. Overall success rate was 91.9% (95% CI 91–93%). Technical failure, clinical failure, and recurrence rates were 0.3%, 2.1%, and 5.6% respectively. Complications were seen in 2.5% (95% CI 1.9–3.3%) patients. There was no significant difference when comparing radiofrequency ablation and cryoablation (p = 0.92). Success rates for intra-articular (radiofrequency ablation) and spinal tumors (radiofrequency and cryoablation) were 97% and 91.6% respectively. Percutaneous ablation of osteoid osteomas was highly successful with low complication rates. Efficacy of radiofrequency ablation and cryoablation is similar, which is consequential because cryoablation is associated with decreased pain, predictable nerve regeneration, and theoretical immunotherapy benefits. Treatment of more challenging intra-articular and spinal lesions demonstrated similarly high success and low complication rates.

Percutaneous thermal ablation for treatment of osteoid osteoma: a systematic review and analysis.

CT-guided radiofrequency ablation (CT-RFA) is considered to be the gold standard for treatment of osteoid osteoma (OO) yet treatment failures (TFs) continue to be reported. This systematic review was conducted to evaluate factors associated with TF, such as ablation time, lesion location, and patient age as well as evaluating how TF has trended over time. Original studies reporting on patients undergoing CT-RFA of OO published between 2002 and 2019 were identified. TF was defined as patients with (1) recurrent or persistent pain +/− (2) imaging evidence of persistent OO. TFs were subdivided into those occurring after the index procedure (primary TF) or those occurring after repeat RFA (secondary TF). Subgroup analysis was performed for TF based on the study date (2002–2010 or 2010–2019), time duration of ablation at 90 °C (6 min or > 6 min), patient age, and tumor location (spinal vs. appendicular). Sixty-nine studies were included for a total of 3023 patients. The global primary TF rate was 8.3% whereas the secondary TF rate was 3.1%. The TF rate reported in studies published after 2011(7%) was about half that during the earlier time period 2002–2010 (14%). There was no statistical difference in TF corrected for age, OO location, or duration of ablation (respectively p = 0.39, 0.13, and 0.23). The global complication rate was 3%, the most frequent being skin burns (n = 24; 0.7%). A decrease in TF observed between 2011–2019 compared to 2002–2010 may reflect improvements in operator technique or advancements in equipment. Duration of ablation, patient age, or location of OO failed to significantly correlate with TF. • CT-guided radiofrequency ablation of osteoid osteomas is a safe technique with a low rate of treatment failure (8.3% failure rate after the primary radiofrequency reducing to 3.1% following a secondary treatment). • The treatment failure rate has decreased over time, possibly due to an improved understanding of the disease process, better technique, and advances in equipment. • Duration of ablation, patient age, or lesion location did not significantly correlate with treatment failure.

CT-guided radiofrequency ablation for osteoid osteomas: a systematic review

Background and purpose Osteoid osteoma is an infrequent but debilitating benign bone lesion which can be successfully managed by percutaneous radiofrequency ablation (RFA). There are few studies investigating the efficacy and follow-up of this treatment. An arbitrary upper limit of 15 mm has been used to differentiate between osteoid osteoma and osteoblastoma with surgery used for lesions above this limit. We aimed to analyse the cases identified from our prospectively maintained database over a ten year period since adoption of this technique in our unit. The primary objectives were to investigate factors which influenced recurrence and the time period at which patients are at risk of this. Basic procedures Consecutive patients with confirmed osteoid osteoma were included. Patient demographics, complications, and recurrence were recorded and multiple regression analysis was performed to investigate causation. Main findings Within a minimum follow up of 21 months (mean 72), a recurrence rate of 16.3% was noted, higher than the published literature. Cox regression analysis to predict chance of recurrence revealed a relationship between larger lucent diameter and recurrence (p = 0.049, CI 95%, hazard ratio 1.33). Conclusions The traditional cut off between osteoid osteoma and osteoblastoma appears less rigidly defined than previously thought and probably represents a progressive scale with larger lesions responding less well to RFA. This study indicates that each millimetre increase represents a ×1.33 chance of recurrence. Clinicians should counsel patients accordingly with lesions approaching the larger limits of this diagnosis.

Sadaf Sohrabi

Papers

Radiofrequency ablation for osteoid osteoma – Recurrence rates and predictive factors