Letter to the Editor: Strategic use of cone-beam CT in modern spine surgery

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TO THE EDITOR: We read with great interest the article by Dr. Costa and colleagues1 (Costa F, Tosi G, Attuati L, et al: Radiation exposure in spine surgery using an image-guided system based on intraoperative cone-beam computed tomography: analysis of 107 consecutive cases. J Neurosurg Spine 25:654–659, November 2016). The authors concluded that the O-arm system (Medtronic, Inc.) exposes patients to a higher radiation dose than does standard fluoroscopy. However, we respectfully would like to offer a different opinion regarding the issue of radiation safety in using the O-arm system.

First, there was a mismatch between the number of patients described in the abstract (n = 107) and in the Results (n = 108; 2 cases had 1 scan, 99 cases had 2, and 7 cases had 3 scans). In other words, 91.6% (99/108) of the patients were scanned twice, and 6.5% (7/108) were scanned 3 times with the O-arm. These multiple O-arm scans, which were conducted in more than 98% of the patients in the current series, inevitably increased the dose of radiation exposure and might be avoided. For instance, the final-check scan (i.e., prior to the patient leaving the operating room) is usually used only for confirmation and often can be omitted.

Using O-arm scans and navigation for screw placement has the most merit in spine surgery involving multiple segments, such as deformity and minimally invasive spine surgery, because it requires only 1 O-arm scan to register the navigation for all screws. The current study calculated that a single O-arm scan exposed the patient to 2.52 mSv. In conventional fluoroscopy-guided percutaneous screw placement, the radiation dose to the patient greatly depends on the number of fluoroscopies taken and thus is subject to the individual operator's technique. The more segments of fluoroscopic guidance used in spine surgery, the higher the radiation exposure in the patient.

A meta-analysis estimated that the average dose of fluoroscopic radiation exposure in a patient who had a 1-level (i.e., 4 screws) minimally invasive transforaminal lumbar interbody fusion (TLIF) procedure would be 1.58 mSv.2–7 There were few data in the literature on the exposure in patients in whom 2-level minimally invasive TLIF (i.e., 6 screws) was performed using fluoroscopy, which is also commonly encountered in spine practice. However, it can be deduced from the above to be 2.37 mSv (1.58/4*6). Thus, there is actually little difference in exposure to radiation in the patient between using the O-arm and fluoroscopy when placing 6 percutaneous screws. One O-arm scan is usually adequate to navigate screw insertion in up to 5 or 6 vertebral segments of the thoracolumbar spine. Therefore, fluoroscopy is likely to involve more radiation exposure in the patient than the O-arm when 4 or more vertebral segments are targeted.

There have been no guidelines regarding radiation safety for patients who undergo spine surgery. The issue of radiation has drawn increasing attention as minimally invasive spine surgery has become prevalent, because image guidance is particularly useful for percutaneous screw insertion. We commend the authors for addressing the patients' dosage of radiation exposure per O-arm scan in the thoracolumbar spine. Moreover, when using the O-arm with navigation, the radiation exposure of surgeons, anesthesiologists, and nurses is essentially zero, compared to that during fluoroscopic guidance. This advantage should be highlighted and is especially critical for staff working in high-volume spine centers. Because the patients' risk of radiation exposure remains unknown, and the effective dose of fluoroscopic guidance is seldom reported, further investigations are needed to ascertain a balance between fluoroscopy and O-arm in these spine surgeries.

References

  • 1

    Costa FTosi GAttuati LCardia AOrtolina AGrimaldi M: Radiation exposure in spine surgery using an image-guided system based on intraoperative cone-beam computed tomography: analysis of 107 consecutive cases. J Neurosurg Spine 25:6546592016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Kim CHLee CHKim KP: How high are radiation-related risks in minimally invasive transforaminal lumbar interbody fusion compared with traditional open surgery?: A meta-analysis and dose estimates of ionizing radiation. Clin Spine Surg 29:52592016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Lee KHYue WMYeo WSoeharno HTan SB: Clinical and radiological outcomes of open versus minimally invasive transforaminal lumbar interbody fusion. Eur Spine J 21:226522702012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Ntoukas VMüller A: Minimally invasive approach versus traditional open approach for one level posterior lumbar interbody fusion. Minim Invasive Neurosurg 53:21242010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Peng CWYue WMPoh SYYeo WTan SB: Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion. Spine (Phila Pa 1976) 34:138513892009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Seng CSiddiqui MAWong KPZhang KYeo WTan SB: Five-year outcomes of minimally invasive versus open transforaminal lumbar interbody fusion: a matched-pair comparison study. Spine (Phila Pa 1976) 38:204920552013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Wang JZhou YZhang ZFLi CQZheng WJLiu J: Comparison of one-level minimally invasive and open transforaminal lumbar interbody fusion in degenerative and isthmic spondylolisthesis grades 1 and 2. Eur Spine J 19:178017842010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

Disclosures

The authors report no conflict of interest.

Response

We kindly thank Chang et al. for their considerations regarding our paper. In particular, I appreciate the different opinions and topics analyzed that are a source of discussion.

Regarding the mismatch of the number of patients described in the text, I have double-checked the series presented in the paper. I apologize for this error: in fact, the series consisted of 107 cases, and in the Results section there was an error in the number of cases in which 2 scans were obtained. The correct number is 98, and not 99 as previously written.

As a matter of fact, radiation safety is a crucial matter in spine surgery, and there can be differences in analyzing evaluations. On one hand, we have the patient's perspective, whereas on the other hand we have the surgical staff's perspective.

For patients, it is essential to obtain an acceptable balance between the safety of screw placement and radiation exposure. Image-guided systems (IGSs) based on intraoperative imaging (such as the O-arm system) provide excellent results regarding accuracy, achieving up to 99.2%,1 which is significantly higher than the accuracy of a standard fluoroscopic technique, referenced as 90.3%.3 Analyzing the results regarding radiation exposure in this study or in similar papers4 shows that the main doses for patients, using an IGS that is based on intraoperative CT scans, may vary from 5.15 mSv to 5.69 mSv, which is higher than in other fluoroscopic techniques. However, as stated by Chang et al., the doses reached in the conventional fluoroscopic technique depend on various factors, such as the number of levels and the experience of the surgeon.

In fact, as underlined in the Discussion, and as suggested by Chang et al., doses with the O-arm system may be optimized, with a significant reduction in the final dose. In particular, considering that the accuracy of screw placement reaches more than 99%, a control scan can usually be avoided and considered only when faced with cases in which there is doubt. Moreover, by using collimation or minimizing the parameters of the device, as demonstrated by Su et al.,5 it is possible to reduce the doses further, thus obtaining a radiation exposure that is acceptable and comparable to standard fluoroscopy.

Analyzing the impact of radiation exposure with regard to the surgical staff, our study showed that the final dose is negligible, as with an IGS. Obviously this is a crucial point, especially for staff working in high-volume spine centers. In fact, with this system the radiation dose remains below the recommendations of the International Commission on Radiological Protection.2

In conclusion, in our experience the O-arm system represents a valuable tool for modern spine surgery, granting an acceptable balance between effectiveness of procedure and radiation safety, for both the patients and the surgical teams. Considering that it is widespread over the world (more than 1000 devices), I think that its use should be optimized and regulated, especially with regard to the use of a control scan and better dose collimation. Further studies may suggest a greater indication and role for the use of these devices in spine surgery.

References

  • 1

    Costa FDorelli GOrtolina ACardia AAttuati LTomei M: Computed tomography-based image-guided system in spinal surgery: state of the art through 10 years of experience. Neurosurgery 11:Suppl 259682015

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    International Commission on Radiological Protection: The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103 OttawaICRP2007

    • Search Google Scholar
    • Export Citation
  • 3

    Kosmopoulos VSchizas C: Pedicle screw placement accuracy: a meta-analysis. Spine (Phila Pa 1976) 32:E111E1202007

  • 4

    Mendelsohn DStrelzow JDea NFord NLBatke JPennington A: Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation. Spine J 16:3433542016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Su AWLuo TDMcIntosh ALSchueler BAWinkler JAStans AA: Switching to a pediatric dose O-arm protocol in spine surgery significantly reduced patient radiation exposure. J Pediatr Orthop 36:6216262016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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Article Information

INCLUDE WHEN CITING Published online January 13, 2017; DOI: 10.3171/2016.9.SPINE161054.

© AANS, except where prohibited by US copyright law.

Headings

References

  • 1

    Costa FTosi GAttuati LCardia AOrtolina AGrimaldi M: Radiation exposure in spine surgery using an image-guided system based on intraoperative cone-beam computed tomography: analysis of 107 consecutive cases. J Neurosurg Spine 25:6546592016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Kim CHLee CHKim KP: How high are radiation-related risks in minimally invasive transforaminal lumbar interbody fusion compared with traditional open surgery?: A meta-analysis and dose estimates of ionizing radiation. Clin Spine Surg 29:52592016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Lee KHYue WMYeo WSoeharno HTan SB: Clinical and radiological outcomes of open versus minimally invasive transforaminal lumbar interbody fusion. Eur Spine J 21:226522702012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Ntoukas VMüller A: Minimally invasive approach versus traditional open approach for one level posterior lumbar interbody fusion. Minim Invasive Neurosurg 53:21242010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Peng CWYue WMPoh SYYeo WTan SB: Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion. Spine (Phila Pa 1976) 34:138513892009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Seng CSiddiqui MAWong KPZhang KYeo WTan SB: Five-year outcomes of minimally invasive versus open transforaminal lumbar interbody fusion: a matched-pair comparison study. Spine (Phila Pa 1976) 38:204920552013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Wang JZhou YZhang ZFLi CQZheng WJLiu J: Comparison of one-level minimally invasive and open transforaminal lumbar interbody fusion in degenerative and isthmic spondylolisthesis grades 1 and 2. Eur Spine J 19:178017842010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 1

    Costa FDorelli GOrtolina ACardia AAttuati LTomei M: Computed tomography-based image-guided system in spinal surgery: state of the art through 10 years of experience. Neurosurgery 11:Suppl 259682015

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    International Commission on Radiological Protection: The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103 OttawaICRP2007

    • Search Google Scholar
    • Export Citation
  • 3

    Kosmopoulos VSchizas C: Pedicle screw placement accuracy: a meta-analysis. Spine (Phila Pa 1976) 32:E111E1202007

  • 4

    Mendelsohn DStrelzow JDea NFord NLBatke JPennington A: Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation. Spine J 16:3433542016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Su AWLuo TDMcIntosh ALSchueler BAWinkler JAStans AA: Switching to a pediatric dose O-arm protocol in spine surgery significantly reduced patient radiation exposure. J Pediatr Orthop 36:6216262016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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