Correspondence Address: Dr. Pradhyumn P Rathi Row House No. 1, Shamail Complex, Balaji Nagar, Bhayander West, Thane - 401 101, Maharashtra India
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There are only few reports of the advantages of three-dimensional (3D) computed tomography based navigation system being used for spinal tumor excision. A 33 year old male presented in the clinic with mid-back ache with change in posture. Radiology suggested an osteoid osteoma involving the superior articular process of the D11 vertebra. Accurate localization and complete extirpation of the lesion were performed using a translaminar approach with O-arm Navigation. 3D navigation with the O-arm system provided an easy and accurate localization of the lesion, reducing the risk of instability subsequently and avoiding instrumented stabilization. This technique also provided for histopathological confirmation of the diagnosis.
Computer-assisted spinal surgeries were mainly restricted to pedicle screw placements. However, there were only few reports of the advantages of three-dimensional (3D) computed tomography (CT)-based navigation system being used for spinal tumor excision.
A 33-year-old male presented in the clinic with mid-back ache for 7 months. It was a dull aching continuous pain radiating to the left side of the chest without any claudication, associated with change in posture with drooping of the shoulder to the left side, progressively increased to the point of causing difficulty in daily activities. Pain was aggravated at night and relieved by taking nonsteroidal anti-inflammatory drugs (NSAIDS). The patient had no other comorbidities.
On clinical examination, he had dorsolumbar scoliosis with convexity to the right, tenderness, and paraspinal spasm in that region. The scoliosis was partially corrected on bending forward.
His back visual analog scale (VAS) score was 8 with Oswestry Disability Index 40%. No significant abnormality was detected on neurological examination.
Radiographs of the dorsolumbar spine suggested sclerosis in the D10 and D11 facet joint on the left side with scoliosis with convexity to the right [Figure 1].
Figure 1: X-ray full length showing the scoliosis with convexity to the right
Pre- and post-contrast magnetic resonance imaging of the dorsolumbar spine was performed. The dynamic evaluation was performed with contact using time-intensity curves and correlated with plain CT. There was a well-defined lytic lesion seen involving the superior articular process of the D11 vertebra measuring 11 mm × 11 mm × 9 mm being hypointense on T2 [Figure 2] and mildly hyperintense on T1 with central sclerosis on CT scan scalloping the inferior articular process of the D10 vertebra. It showed rapid early uptake of contrast on arterial phase with slow washout [Figure 3]. These findings favored a diagnosis of osteoid osteoma.
Figure 2: A well defined lytic lesion seen involving the superior articular process of the D11 vertebra measuring 11 mm × 11 mm × 9 mm being hypointense on T2
The patient was positioned prone on the Trios Modular Spinal Surgery Table System with the Wilson Plus Radiolucent Frame (Mizuho OSI, Tokyo, Japan).
After taking safe surgical precautions, a single two-dimensional fluoroscopy image was taken from the O-arm (Medtronic, Memphis, TN, USA) to mark the incision and a stab incision was made cranially to attach the reference probe to the spinous process, extending caudally to the dorsolumbar region.
Subsequent dissection was performed to reach the left D10 D11 facet joint. With the surgical site draped and the O-arm centered, the operating personnel was allowed to exit the operating room along with the anesthesiologist who induced an apnea. With O-arm setting changed to minimize the radiation dose, a CT scan was taken within 15 s. While the personnel entered the room, the O-arm reconstructed the data into 3D images.
The navigation system used was StealthStation S8 (Medtronic, TN, USA). The basic data used for navigation consisted of preoperative CT data, which were transferred and recorded on the system computer and reconstructed into three-dimensional (3D) images.
After registering the navigation, 1.5 mm ball-tipped reference probe, the accuracy of the images was verified by point merging and surface merging. The lesion was identified and accurately localized with the probe. Under neurosurgical microscope OPMI Pentero 900 (Zeiss, Oberkochen, Germany) careful drilling was initiated with 3-mm diamond tip MIDAS Navidrill (Medtronic, TN, USA) in the left D10 lamina till the lesion wall was reached as identified with the probe. The lesion was extirpated en masse from the D11 articular process. Further, drilling was done in the walls of the articular process taking care not to breach the pedicle and keeping the dura safe.
Adequacy of extirpation was checked using the Navigation probe [Figure 4], [Figure 5], [Figure 6], [Figure 7] and Video 1]. Surgical wound was closed. The patient walked 4 h after the surgery. In 2 days, the back VAS improved to 3, and he was discharged home.
Figure 4: Adequacy of superior extirpation was checked using the navigation probe
At 1 month after surgery, he did not complain of back pain or radiation, his ODI was 2%. His scoliosis had improved.
Osteoid osteoma, first described by Jaffe in 1935, is a benign bone tumor involving the axial skeleton in 10% of patients with 75% located in the posterior elements and 7% in the vertebral body., It is characterized by focal or radicular nocturnal pain typically relieved by NSAIDS and painful scoliosis. Plain radiograph may not be always confirmatory; however, triphasic scintigraphy and CT scan help make the radiological diagnosis of osteoid osteomas.,,
Pathologically, it is characterized by the formation of a small nidus of variably calcified osteoid tissue in the stroma of loose vascular connective tissue, surrounded by a margin of dense sclerotic bone.
Treatment of an osteoid osteoma involves complete intralesional excision of the nidus, either by surgical or radiological intervention. However, intra-operative localization of the nidus may be difficult and may involve extensive resection of the adjacent normal bone structure leading to possible risk of fracture and extended period of healing, instability requiring stabilization, or inadvertent neurovascular injury.
Techniques to improve the accuracy of intraoperative localization of the nidus include radionuclide localization with a gamma probe,,,,, intraoperative CT-guided localization,,,,, or a combination of scintigraphy and computer navigation.
A scintillation gamma probe is used to detect the99 mTc-oxidronate concentrating nidus during surgery. However, wide surgical removal of the affected bone was recommended.,,, which in spine, resulted in fusion after en bloc excision.,
CT-guided percutaneous resection uses a drill inside a trocar for lesions in extremities and spine.,,, However, the results were less successful in the spine. Assoun et al. treated 24 patients (23 in extremities and 1 in the spine) by percutaneous CT-guided resection with failure in the only patient with a spinal lesion. Twenty Sans et al. treated 38 patients, of which 2 (in spine) failed, requiring a secondary procedure. Apart from a high failure rate, CT-guided percutaneous resection of osteoid osteomas in the spine has other limitations such as difficulty in accurately localizing the drill tip, because of the scattering of metal instruments, resulting in malpositioned and inadequate drilling with increased risk of accidental dural and spinal cord injury, increased risk of infection due to substandard sterility precautions in radiological suite. Infection occurred in two cases in the series by Sans et al. Hence, Ozaki et al. and Assoun et al. concluded that percutaneous CT-guided resection of osteoid osteomas with spinal localization is not advisable.,
CT-guided percutaneous radiofrequency thermal ablation,, first successfully reported by Osti and Sebben, and laser photocoagulation are minimally invasive procedures described for the treatment of osteoid osteomas located in the extremities and spine. Proximity to neural structures makes this modality conflicting. Samaha et al. in their three cases considered it to be an effective and safe modality to treat lesions adjacent to neural structures However, heating the tip of a needle to 90°C for 4–6 min in a nidus situated adjacent to neural structures inevitably risks thermal damage to the neural structures. Hadjipavlou et al. questioned its safety when the nidus is adjacent to the neural elements. Vanderschueren et al. reported a recurrence in 2 of their 4 cases that had spinal osteoid osteomas. Van Royen et al. (2 out of 5 were failures) concluded that this technique is not as reliable for spinal procedures as it is for extremities. Risk of injury to adjacent neural structures, inconsistent results in the spine and lack of histologic confirmation of diagnosis do not make it the ideal procedure for treating osteoid osteomas in the spine.
The importance of obtaining tissue for histologic diagnosis is emphasized by Sans et al. where six cases had a histologically different diagnosis.
Laser photocoagulation and radiofrequency ablation do not permit histologic confirmation, and the indications for their use should be carefully weighed.
Van Royen et al. used CT-based computer navigation system (Brain LAB) and radionuclide localization with a gamma probe to accurately localize the nidus with successful outcome in all 5 cases. Intraoperatively, the authors found it difficult to identify and match the affected vertebral body preoperative CT scan, which was facilitated by the gamma probe.
Rajasekaran et al. used a fluoroscopy-based computer navigation system (Siremobil Iso-C 3D–Vector vision) in four cases where fluoroscopic images acquired intraoperatively, were reformatted to give real-time multiplanar images to enable accurate localization of the lesions the spine. A repeat intraoperative scan after excision confirms the adequacy of excision.
Mori et al. successfully treated their two cases of osteoid osteomas located adjacent to the facet joints by complete and pin-point removal of the nidus located close to the facet joint without excessive removal of the bone and possible damage of nearby neurovascular structures through navigation guidance by making a translaminar tunnel to reach the nidus using a high-speed drill.
Nagashima et al. recently described a case with an osteoid osteoma of the C2 pedicle successfully treated by using a conventional CT-based navigation system, but with extensive exposure of the entire posterior compartment of the affected vertebra.
Campos et al. used video-assisted thoracoscopic surgery with 3D navigation for osteoid osteoma resection in a thoracic vertebra. The authors reported that the O-arm provided better localization for complete resection.
With intraoperative navigation systems, radiation exposure has been a significant shortcoming, especially in spinal surgeries. Radiation exposure during fluoroscopy-assisted pedicle screws insertion can be as high as 10 folds greater compared with radiation exposure during nonspinal procedures. The radiation produced by one spin of the O-arm is comparable with the radiation produced by a CT scan or by the C-arm when used for a prolonged period. Exposure from an intraoperative thoracic CT scan with the O-arm was less than the exposure from fluoroscopy when pedicle screws were inserted using the freehand technique. The radiation dose with the O-arm depends on the machine protocol (KV and mAs) and the cumulative exposure dose will depend on the number of spins performed.
Krokidis et al. reported the successful use of a novel CT-based navigation system to accurately ablate with only minimal radiation exposure in a pediatric patient.
The effective dose to the patient can be reduced using collimation or by minimizing the parameters of the device, as demonstrated by Su et al. who by changing the O-arm setting to pediatric protocol of 80 kV/80 mAs with no adjustment for level or weight, minimized the effective radiation dose to the patient (0.65 vs. 4.65 mSv in standard mode; P < 0.0001) using this device. These doses are absolutely consistent with the ICRP recommendation for occupational radiation exposure, which proposes a limit of 2 mSv per year.
A long-term follow-up is required to evaluate for recurrence. Case series with more number of patients is required to make this a standardized treatment for such lesions.
3D navigation with the O-arm system provided an easy and accurate localization of the lesion, reducing the risk of iatrogenic instability and subsequent instrumented stabilization, thereby reducing the hospital stay and cost of treatment. A complete extirpation of the tumor mass by precise drilling under direct vision of the operating microscope reduced the risk of fracture, instability, or injury to the adjacent neural structure. A verification O-arm spin confirmed complete tumor excision and a low dose protocol of the O-arm significantly reduced the radiation exposure to the patient. This technique also provided for histopathological confirmation the diagnosis.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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