Abstract
Background
The use of intraoperative CT navigation to manage osteoid osteoma is not common. We report our experience managing osteoid osteoma in the appendicular skeleton using an intraoperative AIRO CT navigation system.
Materials & methods
Between May 2013 and December 2022, 59 patients underwent Navigation-assisted excision of osteoid osteoma in the appendicular skeleton. Our primary study outcome was to assess for recurrence of the tumour with recurrence of symptoms. For our secondary outcomes, we evaluated the complications associated with the procedure and evaluated the histological slides of all patients to see for the presence of nidus.
Results
Of the 58 patients available for review, no patient had a lesion recurrence, and all were symptom-free at an average follow-up of 45.6 months (6–100). Two patients (3.5%) had a superficial infection managed conservatively, and 43 patients (74.1%) had the presence of nidus in curetted samples. No patient developed a pathological fracture after the procedure.
Conclusion
Using intraoperative CT navigation to manage osteoid osteoma in the appendicular skeleton is safe, minimally invasive, and effective in completely removing the nidus with a negligible complication rate. The absence of nidus on histology should not be a concern to clinicians once thorough burring and verification of excision of nidus has been confirmed intra-operatively.
Study design
Retrospective Case Series.
Level of evidence
Level IV.
Keywords: Osteoid osteoma, CT navigation, Nidus, Localization, Intraoperative, Array
1. Introduction
Isolation of the nidus, followed by complete excision has been the mainstay of successful treatment in osteoid osteoma (OO).1,2 While non-operative treatment has seldom been attempted, eradicating the nidus has been associated with favourable results.2, 3, 4 Many techniques are being used to excise the nidus. Minimally invasive techniques using fluoroscopic guidance5 are routinely used but usually result in increased removal of bone. Open methods of en-bloc removal of the nidus or curettage are also associated with increased removal of bone. Fluoroscopic guidance would be ideal in cases where the nidus is clearly visible, but in most cases, the nidus is located in anatomical regions that are difficult to access.6 Percutaneous techniques are common in practice nowadays, mainly involving radiofrequency ablation (RFA), and Computerised Tomography (CT)-Navigation guided excision.7, 8, 9 Percutaneous techniques have the advantage of minimal incision coupled with adequate removal of the tumour, thereby not compromising the inherent strength and integrity of the bone.
RFA is commonly used to managing OO, with favourable results, but is associated with about 8% complications, mainly involving soft-tissue burns.10 RFA is also relatively contraindicated in lesions close to the skin9. In recent times, intraoperative CT Navigation is also commonly employed to manage such lesions percutaneously.6,9 One of the advantages of intraoperative CT Navigation, is real time-imaging followed by verification of adequate excision after removal of the nidus. There are also concerns, regarding the histological presence of nidus, after excision using this technique, and its relation to functional outcomes. We hypothesized that intraoperative CT navigation guided surgeons to excise the lesion adequately with minimal complications. We retrospectively analyzed the outcomes of all cases of OO in the appendicular skeleton managed in our institution since the installation of the intraoperative CT scan in 2013. The primary outcome of our study was to analyse the adequacy of the excision of nidus, and the relief of symptoms after surgery. The secondary outcomes of our study were to analyse the complications related to the procedure, and to evaluate the presence of histological nidus in the curetted sample.
2. Materials and methods
In December 2012, the Brain Lab Intraoperative AIRO CT system was installed in our institution. Following that, between May 2013 and December 2022, 59 patients – 33 males and 26 females – underwent Navigation-assisted excision of OO in the appendicular skeleton. All these patients formed our study group. Osteoid osteomas in the axial skeleton were excluded from our study. Our series's mean age of patients was 24 years (14–46). All patients underwent a pre-operative CT scan to visualise the nidus to confirm the diagnosis of osteoid osteoma. Clinicoradiological co-relation with symptoms of night pain and imaging was used to confirm the diagnosis of OO in all cases. The location of the lesion was predominantly in the femur (56.8%) followed by the tibia (24.1%) (Table 1). All patients who underwent treatment had been discussed in a multidisciplinary meeting involving radiologists and pathologists.11
Table 1.
Characteristics of patients in our cohort (n = 59), list of complications and presence of nidus on histology.
| Mean age (in years) | 24 (14–46) |
|---|---|
| Gender (M:F) | 33:26 (56%:44%) |
| Site of Location of Lesion | Femur – (33) 56.8% |
| Tibia – (14) 24.1% | |
| Humerus – (3) 5% | |
| Talus – (3) 5% | |
| Calcaneum – (3) 5% | |
| Ulna – (1) 1.6% | |
| Cuboid – (1) 1.6% | |
| Navicular – (1) 1.6% | |
| Complications | Oncological related |
| Recurrence - Nil | |
| Non-oncological related | |
| Superficial Infection – 2 (3.5%) | |
| Presence of nidus on histology | 43 patients (74.1%) |
3. Surgical technique
All patients underwent the following standard surgical procedure. Regional anaesthesia was preferred in all cases. The entire limb was painted and draped. In cases involving the tibia and the foot, a tourniquet was used. The BrainLab Airo Mobile Intraoperative CT scanner system is an imaging platform used to obtain a high-resolution CT scan of a patient while undergoing surgery intraoperatively.12 In the distal portion of the involved bone, a drill is made, and the reference array is fixed before registration of the images. Pre-operative scanning of the desired anatomical portion is performed. The lesion is then skin-marked using a guide array to assess the proposed trajectory to isolate the nidus [Fig. 1]. Once the nidus is visualized on the scan in all three-dimensional planes, incision is made over the skin. Percutaneous passage of the guide array is done to locate the nidus on the bone. Then, a drill is made surrounding the nidus, removing the lesion using a curette. The material removed is sent for histological examination. The underlying bone is then burred completely using a high-speed burr (60,000 RPM). A repeat CT scan is done to confirm complete removal of the nidus, and is also checked in real-time with the array [Fig. 2]. Post-Surgery, full-weight bearing assisted mobilisation was initiated from the next day.
Fig. 1.
Osteoid osteoma with characteristic nidus in the talus (a), managed by CT-navigation guided excision. Note the array marked for guide (b). Localization of the nidus on 3-dimensional planes using the guide array (c,d and e).
Fig. 2.
Pre-excision (a) and Post-excision (b) scans showing confirmation of nidus removal. Histology sample of curetted specimen showing characteristic nidus (c).
To assess our primary outcome, we assessed all patients for any signs of recurrence of pain and symptoms. For our secondary outcomes, we evaluated the complications associated with the procedure and evaluated the histological slides of all patients to see for the presence of nidus. All patients were assessed retrospectively from a prospectively collected database.
4. Results
Of the 59 patients in our study, 58 were available for follow-up. One patient was lost to follow-up. At a mean follow-up of 45.6 months (6–100), 57 patients had complete relief of pain post-surgery and no recurrence of symptoms [Fig. 3]. One patient who had an OO in the medial aspect of the proximal femur excised, had intermittent pain around the thigh even at one year post-surgery. Suspecting recurrence or a residual lesion, a SPECT-CT scan was done, which showed no evidence of the lesion. He was diagnosed to have a labral tear in the hip, for which he underwent arthroscopic surgery, leading to a favourable recovery. No patient had a recurrence of the lesion and symptoms.
Fig. 3.
Osteoid osteoma in the posterior aspect of proximal tibia seen on Imaging (X-rays, Ct Scan and PET Scan) (a,b,c,d,e). Post-excision, radiographs taken at 1 year follow-up (f,g). The patient is completely symptom-free.
Two patients (3.5%) developed wound healing problems at the site of incision. One patient had superficial infection, and another had superficial skin necrosis. Both healed well with dressings and antibiotics. No other complication was noted in any other patient.
Analysis of the histopathological samples of curetted bone, showed the nidus in samples from 43 patients (74.1%) [Fig. 2]. The remaining 15 patients did not show the characteristic nidus on histology.
5. Discussion
Our study shows favourable results while using intraoperative CT Navigation for excision of OO with the removal of nidus and relief of symptoms in all patients with a minimal complication rate. Percutaneous technique ensured minimal morbidity, and early mobilisation for all our patients. All patients in our study had complete relief of symptoms due to the nidus and returned to performing normal activities. Only 74.1% of patients had the presence of nidus using this technique on histology, but as complete burring was done, any residual lesion was completely removed, resulting in complete relief of symptoms.
Complete removal of the nidus after isolation is the key to successful outcomes for OO treatment.2,4,13,14 Various minimally invasive techniques are being practised nowadays, including RFA, laser ablation, cryo-ablation, and magnetic resonance-guided ultrasound therapy.13 RFA, though commonly used with success, is associated with risks when used near important neurovascular structures15 and is contraindicated when the lesion is near the superficial skin9. Another disadvantage of these procedures is the minimal recurrence rate involved and the time involved for the procedure.15 In our series, there was no recurrence in any of the cases, thereby showing the efficacy of this technique. One significant advantage apart from real-time imaging intraoperatively, is the re-scan which is done after curettage and burring in each case, which allows the surgeon to know if any residual lesion is remaining. Confirmation of adequate excision of the tumour is one of the significant advantages of this technique, as shown in this systematic review16 analysing the role of intraoperative CT scan in improving outcomes. The rate of revision surgeries has been significantly reduced.
After localization, various methods have been performed to remove the lesion. High-speed burring is a commonly used technique.17,18 Burring under CT navigation is beneficial on two fronts. Precise location is achieved, thereby enabling the surgeon to make a minimal incision to access the lesion. Also, re-imaging after burring can help the surgeon go back and perform another curettage if needed. Another advantage of this technique is that since the precise location is achieved, adequate minimal curettage and bone removal is sufficient in most cases, as seen in our series. Thus, we feel use of CT navigation intraoperatively has more advantages than conventional open surgery. A comparative study of 23 patients, between conventional surgery and CT-guided mini-incision surgery for OO, demonstrated that the latter had a short hospital stay, smaller bone defects, shorter surgical time, and a 0% recurrence rate.17 Only percutaneous drilling and nidus removal after CT localization also hold the risk of removing increased bone, thereby risking increased chances of fracture, especially in the proximal femur. In a study of 44 cases of OO in the proximal femur managed using percutaneous drilling, the authors reported complications in 12.5% of cases.19 Two patients had proximal femoral fracture, apart from a patient who had a lesion recurrence. In our series, 18 cases (31%) were located in the proximal femur. We had no case of fracture and also no recurrence. One of the probable reasons could be the real-time imaging and probe navigation, which is possible intra-operatively, to check for adequacy of bone removal, also ensuring that the nidus has been removed completely [Fig. 4]. Thereby, repeated drilling and burring can be avoided, thereby preventing the weakening of the bone.
Fig. 4.
Presence of nidus (a,b) which was isolated, and excised and confirmed by intraoperative scans (c,d). The green arrow is representative of the array used to check the anatomical location intended to be assessed.
The presence of nidus in histopathology and its association with outcomes is an important point of concern for clinicians.20,21 In our study, only in 74.1% of patients showed the presence of nidus on histology. Similar results of 75%20 and 77%21 of patients showing nidus on histology were reported by two different studies. However, even in the remaining 15 patients, they showed no evidence of recurrence of symptoms and were pain-free. Adlan et al., in their analysis of 88 histology samples of patients of OO managed with RFA, demonstrated better pain relief in patients who had nidus compared to those who did not show the characteristic nidus, significantly reducing the need for re-interventions.20 However, it must be noted that the authors employed RFA, where there are limitations with using burr, which we employed in all cases. There is always a close balance between ensuring that the nidus has been completely removed by repeated burring compared to removing excess bone, thereby damaging bone integrity. This is important in preventing a pathological fracture or adding additional stability to the bone.22 In the upper limb, reconstruction is mostly not needed,23 however in the lower limb, especially the proximal femur, there may be a need for providing additional stability after removal of bone. The use of high-speed burr and repeat scanning with navigation helps on two fronts. First, the tumour is completely burred out, and verification with the guide array can be done to confirm the location on the bone. Secondly, a repeat burring can be done if any residual lesion is seen. Nine cases (15.5%) necessitated repeat burring in our series. No patient in our series had a recurrence of pain or symptoms.
Apart from being minimally invasive, intraoperative CT navigation helps in localization and provides intraoperative verification of the OO lesion in the bone. Our series shows that confirmation of the location and verification after burring for any residual lesion are important advantages in preventing recurrences and re-interventions. Adequate burring and confirmation of nidus removal intraoperatively by scans are sufficient in removing the tumour and making the patient symptom-free [Fig. 5]. For these reasons, this modality is our treatment of choice in managing OO.
Fig. 5.
Osteoid Osteoma in the femur shaft (a,b), managed with Navigation guided excision. Radiographs taken post-surgery (c,d). Note the minimal amount of bone removed to clear the nidus.
6. Limitations of our study
Our study is not without limitations. Single-center results and the retrospective nature of our study are limitations. Still, our sample size (58 patients) is one of the largest series from a single centre managing such cases using this technique. We have not assessed the radiation dose involved to patients compared with similar techniques like RFA, and we intend to do that in a prospective, multi-center, comparative study in the near future. The correlation of the size of the nidus with the presence of the nidus on histology was not analyzed, as few cases in the earlier years did not have the exact size of the nidus in the data.
7. Conclusion
Our results show that intraoperative CT navigation is a safe, minimally invasive, and effective technique for managing OO. With complete pain relief and negligible complication rate, lesions can be easily excised completely. The absence of nidus on histology should not be a concern to clinicians once thorough burring and verification of excision of nidus has been confirmed intra-operatively.
Conflict of interest
The authors declare no conflict of interest.
The study was performed following the ethical standards in the 1964 Declaration of Helsinki.
Funding statement
This study was funded by Ganga Orthopaedic Research & Education Foundation (GOREF)
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Informed consent
All participants were informed regarding the use of their Images, and consent was obtained for their use in anonymity.
The study was performed in accordance with the ethical standards in the 1964 Declaration of Helsinki.
Ethics approval
Institutional Review Board approval was obtained for this study and the same has been attached in the Supplementary documents.
Availability of data and materials
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Use of AI assistance in manuscript writing
No use of AI or AI-assisted modules were used in writing this manuscript.
Funding statement
This study was funded by Ganga Orthopaedic Research & Education Foundation (GOREF)
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Informed consent
All participants were informed regarding the use of their Images, and consent was obtained for their use in anonymity.
CRediT authorship contribution statement
Raja Bhaskara Rajasekaran: Project administration. Venkatadass Krishnamoorthy: Supervision. Pushpa Bhari Thippeswamy: Methodology.
Declaration of competing interest
The authors declare that they have no conflict of interest.
Acknowledgements
We would like to acknowledge and thank all physician assistants who assisted in data procurement and tabulation of results.
Abbreviations
- OO
Osteoid Osteoma
- CT
Computerised Tomography
- RFA
Radiofrequency ablation
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.