Computed tomography-guided radiofrequency ablation of intra-articular osteoid osteoma: a single centre’s experience

Abstract

Objective: To evaluate safety and efficacy of radiofrequency ablation (RFA) in the treatment of painful intra-articular osteoid osteoma.

Materials and methods: During the last 3 years, 15 patients underwent computed tomography (CT)-guided biopsy and RFA of symptomatic intra-articular osteoid osteoma. In order to assess and sample the nidus, a coaxial bone biopsy system was used. Biopsy was performed and followed by ablation session with osteoid osteoma protocol in all cases. Procedure time (i.e. drilling including local anaesthesia and ablation), amount of scans, the results of biopsy and pain reduction during follow-up period are reported.

Results: Access to the nidus through normal bone, biopsy and electrode insertion was technically feasible in all cases. Median procedure time was 54 min. Histologic verification of osteoid osteoma was performed in all cases. Median amount CT scans, performed to control correct positioning of the drill and precise electrode placement within the nidus was 9. There were no complications or material failure reported in our study. There was no need for protective techniques of the articular cartilage. Pain reduction was significant from the first morning post ablation and complete at the one week and during the follow-up period. No recurrences were noted.

Conclusions: RFA under CT guidance is a safe and efficient technique for the treatment of painful intra-articular osteoid osteoma. Imaging guidance, extra-articular access through normal bone and exact positioning of the needle-electrode inside the nidus facilitate safety of the technique and prevention of damage to the articular cartilage.

Keywords:

• Thermal ablation
• radiofrequency
• clinical trials – thermal ablation
• imaging

Introduction

Osteoid osteoma is a benign inflammatory bone tumour most common in males between 7 and 25 years of age; patients typically complain of pain that worsens at night and is promptly relieved by salicylates [1–3]. The tumour was first reported by Jaffe in 1953 and is composed of the nidus which is bone at various maturity stages within a highly vascular connective tissue stroma; the centre of the nidus represents the most highly mineralised part displaying variation of the mineralisation level [2–4]. Depending on the location and axial imaging findings, osteoid osteoma can be classified into subperiosteal, intracortical, endosteal or intramedullary and intra-articular [3]. Intra-articular osteoid osteoma is the least common type and refers to lesions located within or near a joint [3,5]. Usually, tumour is located within the hip joint and rarer in ankle, elbow, wrist and knee [3,6].

Rosenthal, in 1992, introduced in clinical practice the application of radiofrequency ablation (RFA) with a percutaneous approach for the treatment of osteoid osteoma [7]. Alternatives include laser interstitial therapy (LITT), microwave (MWA), cryoablation (CWA) and High Intensity Focused Ultrasound under MR guidance (MR-guided HIFU) [8–20].

Purpose of our study is to evaluate the safety and efficacy of computed tomography (CT)-guided RFA in the treatment of painful intra-articular osteoid osteoma in a series of consecutive patients.

Materials and methods

All patients and/or their parents were informed about the technique itself as well as possible benefits and complications and they signed a written consent form to the procedure. Authors have no conflict of interest to declare. No industry support was received for this study.

Patient characteristics

We retrospectively evaluated 15 patients who underwent CT-guided biopsy and RFA of an intra-articular lesion with imaging features of osteoid osteoma during the last 3 years. All patients presented to the orthopaedics department complaining of pain (5/15 patients reported classical night pain and 10/15 patients reported joint pain throughout the whole day) and mobility impairment and diagnosis of osteoid osteoma was performed on the basis of imaging findings; following all patients were referred to our department for percutaneous ablation. Involved joints included hip (n = 7), hand (n = 1), elbow (n = 1), wrist (n = 1), ankle (n = 2), foot (n = 1), shoulder (n = 1) and facet joint (n = 1). The demographics, location and size of lesions are listed in Table 1.

Table 1. Demographics, size and location of the lesion.

Patient	Sex	Age (years)	Joint affected	Lesion size (mm)	Pain prior RFA (NVS units)
1	M	15	Hip	10	9/10
2	F	14	Hip	9	8/10
3	M	5	Hip	7	9/10
4	M	14	Hip	5	8/10
5	F	26	Hip	6	9/10
6	M	21	Hip	8	9/10
7	M	19	Facet joint	5	9/10
8	M	21	Wrist	4	8/10
9	M	6	Hip	10	8/10
10	M	17	Foot (PPJ)	4	10/10
11	M	22	Hand	5	10/10
12	M	21	Ankle (Tibio-fibular)	3	9/10
13	M	34	Shoulder	5	10/10
14	F	24	Elbow	10	7/10
15	F	32	Ankle (Talo-calcaneal)	5	9/10

Each patient underwent physical examination and coagulation laboratory tests at least 24 h prior to the percutaneous biopsy and RFA session, whilst in correlation with his/her medical record, evaluation of all imaging studies was performed. Pre-operational imaging included X-rays and CT scan (15/15 patients); in 8/15 patients, there was additional pre-procedural magnetic resonance imaging (MRI). Exclusion criteria for the procedure included untreatable coagulopathy, active, systemic or local infections and patient (or parent) unwilling to consent to the procedure.

Percutaneous biopsy and radiofrequency ablation session

Preoperative antibiosis (a single dose of Piperacillin + Tazobactam) was intravenously (IV) administered 45–60 min prior to the intervention according the instructions of the hospital’s Infections Department. Under local sterility, anaesthesiology care, cardiovascular monitoring and CT-guidance, an access to the lesion of interest was performed through normal bone rather than crossing through the articulation itself. Anaesthesiology care included general anaesthesia or spinal anaesthesia combined with sedation depending on patient’s age and anaesthesiologist’s preference. In all cases, a single dose of dexamethasone (0.2 mg/kg) was IV administered during anaesthesia.

In order to assess and sample the nidus of the lesion suspected to be an intra-articular osteoid osteoma, OnControl Bone Biopsy Coaxial System (Arrow OnControl, Teleflex, Shavano Park, TX) was used; the bone access needle used was 10 Gauge in diameter and 6 or 10 cm in length whilst the coaxial biopsy needle included in the set was 12 gauge in diameter and 10 or 14 cm in length, respectively. The correct needle position inside the lesion was verified with CT scan (Figure 1). Biopsy was performed in all cases. Following, a 17 G diameter/150 mm length/0.5–1 cm active tip monopolar radiofrequency electrode (RF AMICA probe, Hospital Service S.P.A. Rome/Italy) was coaxially inserted into the lesion and ablation was performed with osteoid osteoma protocol (temperature around 90 °C for 6 min) (Figure 2). Procedure time (i.e. drilling including biopsy and ablation), amount of scans, the results of biopsy as well as pain reduction were recorded. Patient remained in the hospital overnight and then discharged; paracetamol was IV administered during the hospital stay (dose depending upon patient’s age and weight). Patients with intra-articular osteoid osteomas in the foot and ankle (3/14) post treatment with RFA were advised of weight-bearing restrictions for 2–3 weeks mainly for prophylactic reasons.

Figure 1. Computed tomography axial scans of a patient with symptomatic intra-articular osteoid osteoma (biopsy proven). (A) White arrow illustrates the nidus (5 mm in diameter) of an intra-articular osteoid osteoma in the tibio-fibular joint. (B) Once inside the nidus, coaxially through the OnControl trocar the bone biopsy needle is inserted for sampling. (C) Post biopsy, the radiofrequency electrode is coaxially inserted and ablation session is performed with osteoid osteoma protocol according the manufacturer’s guidelines. (D) Post-ablation scan illustrating the access through normal bone ending inside the nidus of the osteoid osteoma.

Figure 2. Computed tomography axial scans of a patient with symptomatic intra-articular osteoid osteoma in the hand (biopsy proven). (A) Radio-opaque mesh is placed over the skin for entry point selection. (B) Post biopsy, the radiofrequency electrode is coaxially inserted and ablation session is performed with osteoid osteoma protocol according the manufacturer’s guidelines.

Outcome measures

Pain and mobility were recorded prior and the morning post RFA session with clinical evaluation and an inventory containing a numeric visual scale (NVS). In the same inventory, questions were included concerning the pain itself and its influence upon patient’s activity (sleep, occupation and housework and walking) and mobility impairment.

Follow-up consisted of clinical visits (general, clinical and neurological condition, pain reduction and mobility improvement according to NVS scale) at the week 1 and phone calls at 1st and 6th month as well as at 1 and 2 years. Questions asked during the follow-up period concerned the pain reduction and mobility improvement, and whether the procedure had decreased or totally relieved the symptoms they were treated for.

Results

Access to the nidus through normal bone was feasible in all cases (15/15). Radiofrequency electrode was coaxially inserted within the nidus and ablation was successfully performed in all lesions (technical success rate 100%). Histologic verification of osteoid osteoma was performed in 12/15 cases (80%). Median procedure time was 54 min. Median amount of CT scans, performed to control correct positioning of the drill and precise electrode placement within the nidus was 9. Reactive synovitis was illustrated in 2/8 patients with MRI prior to ablation with osteoid osteoma at the hip joint located in acetabulum; both patients underwent an additional intra-articular injection of corticosteroid immediately post ablation with no need for additional injection during the follow-up period. There were no complications or material failure reported in our study. There was no need for protective techniques of the articular cartilage. Pain reduction was significant from the first morning post ablation and complete (0/10 NVS units) at the first week and during the follow-up period (2 years). Overall mobility improved in 15/15 patients. No recurrences were noted. No clinically significant complications (minor or major) were noted in our study population.

Table 2. Literature review of osteoid osteoma ablation techniques.

Author	Ablation method	Imagingguidance	Number ofpatients	Treatment outcome	Complications
Mahnken [9]	Monopolar RF	CT	17	Primary success rate 83% Secondary success rate 100%	No complications
Mylona [10]	Seven-array expandable RF electrode	CT	23	Primary success rate 91.3% Secondary success rate 100%	No complications
Gangi [12]	Laser ablation	CT	114	Primary success rate 98.2% Secondary success rate 99.1%	1 case of mild reflex sympathetic dystrophy of the wrist that relieved completely after 2 months
Mahnken [13]	Bipolar RF	CT	12	92% success rate	No complications
Dasenbrock [14]	Plasma mediated radiofrequency ablation	CT	3	100% success rate	No complications
Kostrzewa [15]	Microwave ablation	CT	10	100% success rate	No complications
Basile [16]	Microwave ablation	CT	7	100% success rate	No complications
Napoli [17]	MR-guided HIFU	MR	6	100% success rate	No complications
Rosenthal [29]	Monopolar RF	CT	263	Primary success rate 91%	Two anaesthesia-related complications one mild vasomotor instability that spontaneously resolved 1 case of presumed cellulitis treated with oral antibiotics
Whitmore [33]	Cryoablation	ConventionalCT 22/29 Conebeam CT 7/29	29	Short-term clinical success rate 96%	6 cases of minor complication (mild dermal blistering, transient numbness, intermittent weakness and pain)
Current study	Monopolar RF	CT	15	100% success rate	No complications

Discussion

Intra-articular osteoid osteoma is located within or near a joint; it accounts for 10–13% of osteoid osteoma cases and is considered a rare and separate clinical entity with puzzling clinical manifestations since on the one hand, pain is not necessarily worse at night and on the other, there might be prominent joint tenderness and effusion [3,21]. Axial imaging findings of intra-articular osteoid osteomas illustrate minimal or absent reactive cortical thickening which is attributed to the lack of cambium (the inner layer of the periosteum responsible for bone formation but usually absent from joint capsule) [3,22]. The confusing clinical and imaging findings of intra-articular osteoid osteoma often lead to a delayed diagnosis [23].

En block surgical resection of osteoid osteoma is limited by the dissection size (which is disproportionate to the lesion size) and the common need for cortical bone matrix transfer and internal fixation [24,25]. In addition, post resection pain persists in 7–20% of the cases whilst osteomas recur in 7–12%; complications of surgical resection range at 9–28% and include fracture, pain from implants and infection [24,25]. Alternative traditional surgical techniques for osteoid osteoma treatment include marginal resection of the entire nidus, curettage or high speed burr techniques [26]. On the other hand, percutaneous ablative techniques are minimally invasive methods for safe and efficacious destruction of the nidus (Table 2). Up until now, RFA has been thoroughly and extensively studied and is considered the gold standard of percutaneous techniques; on the other hand, in the literature, there are extensive and large series concerning the application of laser for the treatment of osteoid osteoma [8,12,27,28]. Patient series concerning other percutaneous therapies including MWA, CWA and MR-guided HIFU report similar efficacy and safety rates, however, larger and more extensive studies are necessary [13–20]. Comparison of surgical to percutaneous therapies for osteoid osteoma favours the latter in terms of minimum trauma, minimum functional restriction and significantly lower cost [26].

Case-series in the literature advocate performance of percutaneous RFA in intra-articular osteoid osteomas suggesting that although technically challenging to access, these lesions can be effectively treated as well [10]. Motamedi et al. [11] suggest avoiding trans-articular approach, because it is governed by increased risk of infection, electrode cooling and ablation of non-targeted tissue. Rosenthal et al. [29] suggest that cartilage although at risk for thermal damage appears to tolerate well any thermal injury as well as any focal defects created by the ablation entry point. Additionally, experimental studies suggest that the reactive zone plays the role of insulator in terms of reducing the temperature in the surrounding area [30]. Lesion size is an important factor for technical success; Mahnken et al. [9] advocate several needle positions if the lesion size exceeds 1 cm.

According to our study, percutaneous RFA under CT-guidance is a safe and efficacious technique for the treatment of symptomatic intra-articular osteoid osteoma. The success rate reported in our study (both technical and clinical) is in accordance to the excellent results reported by other studies in the literature [9–11,22,27,28]. During the 2 years’ follow-up, patients in our study did not report any clinical findings suggestive of delayed articular cartilage damage; in the literature however, there are case reports of delayed articular cartilage damage post ablation of intra-articular osteoid osteomas or other lesions [8,31]. Imaging guidance, extra-articular access through normal bone and exact positioning of the needle-electrode inside the nidus are factors ensuring avoidance of direct intra-operative cartilage damage. Specifically, for the proximal femoral lesions, the access route was through the greater trochanter, following the natural lines of the Haversian canal system and additionally accessing the nidus through normal bone in a direction that the ablation zone will extend backwards and away from the articulation.

Although not used in our study, articular irrigation with cold fluid can be used as a protective mechanism for the articular cartilage [26]. Recently, Vikinqstad et al. [32] compared the acute histologic and biomechanical effect of RFA and CWA on periarticular structures in a swine model; authors concluded that as far as articular cartilage is concerned, neither RF ablation nor CWA resulted in significant acute architectural changes although long-term outcomes are currently unknown. In our experience, apart from bone integrity, the approach towards the nidus of the osteoid osteoma also plays a significant role. Approach through normal bone in such a way that ablation zone extends away from the articulation as much as possible seems to suffice for cartilage protection.

Limitations of our study include the retrospective nature, the small patient sample and the lack of a control group which will consist of patients undergoing surgical or alternative percutaneous techniques and will be randomised and prospectively compared. Further limitations include the lack of biomechanical laboratory proof concerning the least damage to the articulation and to the weight-bearing capability as opposed to surgical approaches. Moreover, because this is a retrospective study and since, during the follow-up period, there was no pain recurrence and therefore no excuse for MRI imaging, an additional limitation of our study is the lack of post ablation MR imaging verifying the absence of cartilage damage.

Conclusions

RFA under CT guidance and percutaneous approach is a safe and efficient technique for the treatment of painful intra-articular osteoid osteoma. Imaging guidance, extra-articular access through normal bone and exact positioning of the needle-electrode inside the nidus facilitate safety of the technique and prevention of damage to the articular cartilage.

Disclosure statement

The authors report no declarations of interest.