CT-Guided Percutaneous Drilling of Osteoid Osteoma: A Safe, Minimally Invasive and Cost-Effective Method

Abstract

Background

CT-guided percutaneous drill resection (PDR) for osteoid osteoma fell out of vogue with the advent of radiofrequency ablation (RFA). However, the routine use of RFA is offset by its high cost and need for specialized instrumentation.

Aims and objectives

This study is an analysis of our series of patients treated with PDR, to know its efficacy, safety and cost-effectiveness.

Materials and methods

This study is a retrospective analysis of prospectively collected data of 33 patients with a mean age of 10.03 years (2–21 years 13:10 M:F). The proximal femur was the commonest location, followed by shaft femur, tibial shaft, pubic ramus and lateral humeral condyle. Three were recurrences. The procedures were performed by one of four fellowship-trained paediatric orthopaedic surgeons, using a standard protocol with the help of a radiologist. CT-guided drilling was performed under sedation/short general anaesthesia using a guidewire for identification, followed by sequential drilling using a 6.5 mm cannulated drill or a triple ream drill. Patients were hospitalized overnight for pain relief and allowed protected weight bearing as per pain tolerance. They were evaluated weekly for 2 weeks and 3 monthly thereafter.

Results

The mean final follow-up was 19.72 months (6 months to 58 months). All patients had complete resolution of symptoms within 3 days of the procedure. There were no major complications and there were two minor complications (haematoma and cutaneous hypoaesthesia). There were no recurrences till the last follow-up.

Conclusion

This study, one of the first and largest from India about CT-guided PDR, shows that this method can still be safely and effectively used as a primary treatment modality in OO, especially in economically challenged population. It is much more cost-effective than RFA, can be used even for recurrent tumours and can be safely be performed by a general orthopaedic surgeon without any special instrumentation.

Introduction

Osteoid Osteoma is a small, benign, osteogenic, exquisitely painful tumour affecting people younger than 30 years of age, primarily in the immature skeleton [1, 2]. This tumour accounts for around 10% of all benign bone tumours and is most commonly seen in the second decade of life [3]. The characteristic feature of OO is pain, which is nocturnal and is typically relieved by oral NSAID’s [2]. There is usually no outward sign of inflammation or any obvious swelling, leading to many instances of missed and delayed diagnosis.

Any treatment of Osteoid Osteoma should be aimed at removing the entire “nidus” of the tumour with minimal resection of the surrounding normal bone, thus causing minimal weakening of the bone [4]. This is extremely difficult during open surgery due to the technical difficulty in identification and pinpointing of the tumour and the mechanical precariousness of the surrounding bone after resection [5]. Hence, over the years, procedures utilising CT-guided identification of the mass and further ablation have come to the fore [6–8]. One of the first procedures in this regard was CT-guided Percutaneous drill resection (PDR) of the tumour. This procedure, described in the late 1990s and early 2000s, was shown in a few studies to be safe and effective [9, 10]. However, in the last decade or so, this has, for some reason, fallen out of vogue, due to the advent of CT-guided Radiofrequency Ablation (RFA). CT-guided RFA has, over the last few years, emerged as the foremost performed procedure for OO. However, there are still some concerns about its high cost, need for advanced instrumentation and machinery (which may not be available at all places), and chance of incomplete removal [4, 11].

With this scenario, we decided to analyse our cases of osteoid osteoma treated with percutaneous drill resection, to find a locus standi for the same in this era of RFA. We have analysed our results as regards its safety, efficacy, recurrence rates, and cost-effectiveness.

Materials and Methods

This study is a retrospective analysis of prospectively collected data of 33 patients with a mean age of 10.03 years (2–21 years) with 13 females and 20 males. The diagnosis of osteoid osteoma was done based on specific clinical and radiological features. The commonest presenting symptom was pain, which was typically nocturnal, which was relieved by oral NSAIDs in 29/33 patients (89%), followed by wasting in two patients and restriction in motion in two patients. CT scan was performed in all patients, while MRI was performed in four patients. The radiological diagnosis was done based on four distinct diagnostic features: (1) sharp, round, or oval nidus; (2) size less than 2 cm; (3) homogenous dense centre; (4) 1–2 mm peripheral radiolucent zone surrounded by dense sclerotic rim (Fig. 1a, b). The proximal femur was the commonest location, in 18 patients, followed by shaft femur in eight, tibial shaft in five and one each in pubic ramus and lateral humeral condyle. Three were recurrences, with surgical excision performed in two and RFA in one. The patients presented to us at an average of 7 months after onset of symptoms and there was significant delay in diagnosis, with two of the patients were also subjected to empirical AKT prior to presentation.

Fig. 1.

a Anteroposterior radiograph of the hip joint showing a dense sclerotic zone near the inferior border of the femoral neck surrounding a lytic zone which represents the nidus of the osteoid osteoma. b Axial CT scan of the same child showing a homogenous sclerotic rim and a small nidus of the osteoid osteoma

Surgical Protocol

The procedures were performed by one of four experienced fellowship trained paediatric Orthopaedic surgeons, using a standard protocol with the help of a radiologist. Before the child was sedated, a single scout film was performed using a marker ruler placed on the skin in two orthogonal planes for skin marking of the nidus (Fig. 2a). Once the point of entry is identified using this scout film, the incision for entry is marked using a permanent skin marker or scored using a thin hypodermic needle (Fig. 2b). The child’s lower limb (or in one case the upper limb) is securely strapped, so that the position of the limb does not change after anaesthesia and muscle relaxation (Fig. 2c). After sedation or short IV anaesthesia is administered, and sterile painting and draping is done, a needle is inserted till the bone at the point marked (Fig. 2d). The patient is then slid in the CT and the position and direction confirmed and if required changed slightly (Fig. 2e). The patient is slid back out; local anaesthetic is given in the same tract and a small incision of around 1 cm in size taken on both sides of the needle. Subcutaneous tissue, fascia, and periosteum are cut with a sharp stab knife. A 6.5 mm cannulated drill guide wire is then drilled in the bone in the same tract (Fig. 2f). The patient is then slid in the CT chute again and the position of the guide wire is confirmed to be right inside the nidus. Minor adjustments in direction are made if needed. Once the patient is slid out, and if the position of the guidewire is confirmed, drilling is performed over the guide wire using a 6.5 mm cannulated drill bit (Fig. 2g). If necessary, a triple ream drill is also used to achieve complete obliteration of the nidus (Fig. 2h). The bone scrappings and the bone dust on the drill flutes are collected to be sent for histopathological examination. The patient is once again slid into the gantry with the drill in situ to confirm the position of the drill. Once that is seen, a final shot is performed after removing the drill bit and confirming that the entire nidus is removed (Fig. 2i). Hence, a minimum of five to a maximum of nine shoots were necessary in out series. The skin is closed in a single layer with a single or two sutures, compression dressing is given and patient is wheeled out (Fig. 2j). The patient is kept admitted overnight for pain relief and three doses of IV antibiotics. All except one patient was advised immediate weight bearing from the next day as per pain tolerance. In one patient, there was significant drilling with a triple ream drill in the calcar area of the femur, and hence, weight bearing was not allowed for 3 weeks followed by protected weight bearing for 3 more weeks. They were evaluated weekly for 3 weeks till suture removal and 3 monthly thereafter. A check radiograph was performed immediately post-operatively and then at 6 months and then at 1 year (Fig. 3a–e).

Fig. 2.

Stepwise surgical procedure of CT-guided percutaneous drilling in a 12-year old girl with osteoid osteoma over right proximal femur. a Scout film showing a small marker being placed at the level of the lesion. b Corresponding skin marking made over the lateral aspect of the thigh. c Positioning of the child with secure strapping done so as to prevent any movement during the drilling. d Hypodermic needle placed through the skin till the bone. e Axial CT scan confirming the position of the needle. f Clinical and axial CT scan showing positioning of the cannulated drill guide till the nidus. g Clinical and CT scan showing drill bit inserted over the drill guide and passed till the level of the nidus. h Axial CT scan showing triple ream drill passed till the nidus. i CT scan image showing complete obliteration of the nidus at the end of the procedure. j Clinical photograph showing the final size of the incision after closure

Fig. 3.

a Anteroposterior radiograph of the pelvis showing a radiolucent nidus with sclerotic margin near the lateral aspect of the proximal femur. b CT scan images of the same child confirming the same. c Intra-operative images of the same showing the drill bit and complete obliteration of the nidus. d 2 years post-operative Xray showing complete removal of the osteoid osteoma and restoration of the proximal femoral anatomy. e 2 years post-operative clinical photograph showing full painless range of motion

As a rough measurement of cost-effectiveness, we asked the patient about the cost of the procedure and noted it, and also got quotations from three major institutes where RFA is most commonly performed.

Results

The mean final follow-up was 19.2 months (6–58 months). All patients had complete resolution of symptoms within 3 days of the procedure except for one patient who had delayed resolution of pain at around 14 days. This child was the case of recurrence after RFA 2 years back. There was significant amount of sclerotic bone around the osteoid osteoma when we operated on the child and there was some amount of soft-tissue trauma during the procedure and that may probably be the cause of his delayed pain relief. The child eventually had an uneventful recovery and was doing well at 1 year follow-up (Fig. 3a–d). There were no major complications and there were minor complications in only two patients which did not impact the outcome at all. One child had a hematoma which resolved with icing and compression dressing and another patient with OO over the proximal femur had transient hypoesthesia over the lateral femoral cutaneous nerve area. There were no recurrences till the last follow-up. We had sent bone samples in 27 out of 33 patients and could get a confirmatory diagnosis in form of dense sclerotic bone in 18 out of them. The rest were non-specific and non confirmatory.

The cost of the current procedure varied between Rs 20,000 (in a general hospital) to Rs 80,000/- (in a corporate hospital) with a mean of Rs 43,052/-. Three patients had taken an approximate cost quotation for a radiofrequency ablation procedure at three different hospitals—one of which was a charitable hospital. The cost of the procedure varied from Rs. 95,000/- to Rs. 1,71,000/- with an average cost being Rs 1,31,000/-.

Discussion

Osteoid osteoma is a common bone forming, benign tumour commonly seen in the growing skeleton [1, 2]. The treatment of osteoma follows the principle of achieving complete removal of the tumour with minimal weakening of the surrounding bone. To achieve this objective, the existing methods range between two extremes of cost and morbidity. Open en block excision had been attempted in a number of series in the twentieth century. This method has a relatively low cost and has the advantage of not requiring any special instrumentation and getting a very good sample for histopathological confirmation. However, the increased morbidity of the procedure and big incisions, the need for significant resection of bone leading to need for post-operative immobilization, and non-weight bearing and poor intra-operative visualization by vision as well as C-arm led to a search for better and more accurate methods of treatment of OO.

CT-guided procedures came in vogue in the first decade of the twenty-first century in order to solve these problems. These include CT-guided percutaneous drill resection, CT-guided drilling and ethanol injection, and CT-guided radiofrequency ablation (RFA). The advantages of these procedures include very accurate and easy triangulation of the nidus, and very reduced morbidity due to little bone resection and smaller incisions. Over the last few years, there have been a preponderance of papers which have shown the efficacy of CT-guided RFA. Bourgalt et al. [12] showed a series of 87 patients in whom they found a primary efficacy rate of around 90% and secondary cure rate of 98%. Jhankaria et al. [13] in their seminal paper studied their series of 40 patients and could achieve primary and secondary cure rates of 95 and 100%. However, the main issue with this method is the high cost involved in the procedure as well as the need for specialized instrumentation and probes [14]. Another disadvantage is the fact that anatomopathological confirmation is not possible, especially in doubtful cases. There was also a theoretical possibility of physeal damage due to the radiofrequency waves which may prevent this method being used in lesions too close to the physis.

The CT-guided technique of percutaneous drill resection is a time-tested method which had gone out of vogue due to the emergence of the more “advanced” RFA. Over the years, there have been a few articles which showed the benefits of PDR [14, 15]. Engel et al. [14] demonstrated their series of 15 patients where they should a primary cure rate of 95%. This success rate is similar to other methods of percutaneous CT-guided procedures. The resection segment is also very limited due to tomographic guidance for the same. The relapse rates are also comparable to other methods. One other major advantage of the procedure is the possibility of histopathological confirmation of the tumour [15]. Another important benefit of this procedure is tremendous cost-effectiveness as well as the fact that this surgery can be performed using only routine orthopaedic instrumentation [14].

Our study collaborated with other similar studies published from the western world and is probably one of the first and the largest coming out from India describing a series of patients treated with PDR. This study is especially important in Indian setting where many patients come from the economically challenged population and also where there is a dearth of trained interventional radiologists and advanced radiofrequency probes. Our study showed a full cure rate, even in recurrent tumours, with no recurrences till the last follow-up. One of the disadvantages which was described in one study was weakening of the bone due to large diameter drilling and possibility of a fracture. However, one study showed that this drill tract completely healed and recanalised within 1 year of surgery [14]. We also modified our technique to further prevent this complication which can theoretically occur. We have used a specially made drill system with diameters in increments of 1 mm thickness from 3 till 10 mm with guide wires of the different sizes to fit the drill bits. This helps in sequential drilling and thus decreases the stress associated with sudden increments in drill bit diameter.

The cost of the procedure was approximately one-third that of the RFA with all the benefits of the same. We calculated this by the best possible means available at our disposal by getting the quotes for RFA at the hospitals where it was offered. We could not get exact surgical costs, since they were quotations obtained at the time of primary consultations of patients in those hospitals, before they were eventually operated by us. Also there was no actual control group by which we could compare these two values. However, we felt that this facet of the study was worth mentioning, with the proviso that it requires further elucidation in future comparative studies between CT-RFA and CT-PDR.

Our study had a few limitations. It was a retrospective study with no comparative data of other methods used. We have a relatively shorter follow-up of a mean of around 19 months. However, in most of the studies, it has been shown that recurrences occur within the first year after surgery. Hence, we feel that the results after a longer follow-up also would not change.

Thus, we feel that CT-guided percutaneous drill resection of Osteoid osteoma is a safe, efficacious. and cost-effective method of treatment especially in a economically challenged region, which should be continued in spite of the presence of another seemingly “advanced” and more expensive technique which has exactly the same benefits. It may be too early to comment about long-term efficacy of this procedure vis-à-vis CT-guided RFA, for which long term, prospective comparative studies would help in the future.

Author contributions

Concepts: MA, JD, PN, TN. Design: MA,JD. Definition of intellectual content: MA. Literature search: MA. Clinical studies: MA, SV, PN, TN. Experimental studies: SV, PN, TN. Data acquisition: MA, JD, PN, TN. Data analysis: SV, TN. Statistical analysis: SV. Manuscript preparation: MA. Manuscript editing: MA. Manuscript review: MA, SV, JD, HC, PN, TN. Guarantor: MA.

Funding

The authors declare that they or their immediate family members do not have any financial interest in this study.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they or their immediate family do not have any conflict of interest regarding this study.

Ethical standard statement

All procedures performed in the study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individuals included in the study.