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The surgical learning curve and accuracy of minimally invasive lumbar pedicle screw placement using CT based computer-assisted navigation plus continuous electromyography monitoring - a retrospective review of 627 screws in 150 patients.

Wood MJ, McMillen J - Int J Spine Surg (2014)

Bottom Line: With increased experience with the technique, rates of intraoperative pedicle screw malposition were found to decrease from 5.1% of screws in the first fifty patients, to 2.0% in the last 50 patients.Only one screw was suboptimally placed at the end of surgery, which did not result in a neurological deficit.Pedicle screw placement accuracy continues to improve as the surgeon becomes more experienced with the technique.

View Article: PubMed Central - PubMed

Affiliation: Mater Misericordiae Private Hospital, South Brisbane, Queensland, Australia.

ABSTRACT

Objective: This study retrospectively assessed the accuracy of placement of lumbar pedicle screws placed by a single surgeon using a minimally-invasive, intra-operative CT-based computer navigated technique in combination with continuous electromyography (EMG) monitoring. The rates of incorrectly positioned screws were reviewed in the context of the surgeon's experience and learning curve.

Methods: Data was retrospectively reviewed from all consecutive minimally invasive lumbar fusions performed by the primary author over a period of over 4 years from April 2008 until October 2012. All cases that had utilized computer-assisted intra-operative CT-based image guidance and continuous EMG monitoring to guide percutaneous pedicle screw placement were analysed for the rates of malposition of the pedicle screws. Pedicle screw malposition was defined as having occurred if the screw trajectory was adjusted intraoperatively due to positive EMG responses, or due to breach of the pedicle cortex by more than 2mm on intraoperative CT imaging performed at the end of the instrumentation procedure. Further analysis of the data was undertaken to determine if the rates of malposition changed with the surgeon's experience with the technique.

Results: Six hundred and twenty-seven pedicle screws were placed in one hundred and fifty patients. The overall rate of intraoperative malposition and subsequent adjustment of pedicle screw placement was 3.8% (24 of 627 screws). Screw malposition was detected by intraoperative CT imaging. Warning of potential screw misplacement was provided by use of the EMG monitoring. With increased experience with the technique, rates of intraoperative pedicle screw malposition were found to decrease from 5.1% of screws in the first fifty patients, to 2.0% in the last 50 patients. Only one screw was suboptimally placed at the end of surgery, which did not result in a neurological deficit.

Conclusion: The use of CT-based computer-assisted navigation in combination with continuous EMG monitoring during percutaneous transpedicular screw placement results in very low rates of malposition and neural injury that compare favourably with previously reported rates. Pedicle screw placement accuracy continues to improve as the surgeon becomes more experienced with the technique.

No MeSH data available.


Related in: MedlinePlus

Intraoperative CT imaging after L5-S1 TLIF, demonstrating an inferior breach of the cortex of the S1 pedicle by <2mm.
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Figure 0002: Intraoperative CT imaging after L5-S1 TLIF, demonstrating an inferior breach of the cortex of the S1 pedicle by <2mm.

Mentions: It is recognized that pedicle wall breaches, especially medial breaches which are most likely to be associated with neural encroachment due to the close relationship of the nerve root to the medial and inferomedial aspects of the pedicle, are less likely to be appreciated with plain radiography than with CT imaging.1, 22, 26 We assessed our pedicle screw placement based on the system initially described by Gertzbein and Robbins, 12, 16 who considered that there is a margin of 4mm adjacent to the pedicle that can be violated safely without impinging on the spinal cord or cauda equina. With the use of the intraoperative CT system, radiological assessment of screw position in three anatomical planes could be performed immediately after placement of the pedicle screws, before the patient was removed from the operating theatre (Figure 2). This affords the opportunity to revise any screws judged to be misplaced without the cost and inconvenience of a second operation. This is a significant advantage over the use of conventional postoperative CT imaging. Our reoperation rate in this series was zero.


The surgical learning curve and accuracy of minimally invasive lumbar pedicle screw placement using CT based computer-assisted navigation plus continuous electromyography monitoring - a retrospective review of 627 screws in 150 patients.

Wood MJ, McMillen J - Int J Spine Surg (2014)

Intraoperative CT imaging after L5-S1 TLIF, demonstrating an inferior breach of the cortex of the S1 pedicle by <2mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4325487&req=5

Figure 0002: Intraoperative CT imaging after L5-S1 TLIF, demonstrating an inferior breach of the cortex of the S1 pedicle by <2mm.
Mentions: It is recognized that pedicle wall breaches, especially medial breaches which are most likely to be associated with neural encroachment due to the close relationship of the nerve root to the medial and inferomedial aspects of the pedicle, are less likely to be appreciated with plain radiography than with CT imaging.1, 22, 26 We assessed our pedicle screw placement based on the system initially described by Gertzbein and Robbins, 12, 16 who considered that there is a margin of 4mm adjacent to the pedicle that can be violated safely without impinging on the spinal cord or cauda equina. With the use of the intraoperative CT system, radiological assessment of screw position in three anatomical planes could be performed immediately after placement of the pedicle screws, before the patient was removed from the operating theatre (Figure 2). This affords the opportunity to revise any screws judged to be misplaced without the cost and inconvenience of a second operation. This is a significant advantage over the use of conventional postoperative CT imaging. Our reoperation rate in this series was zero.

Bottom Line: With increased experience with the technique, rates of intraoperative pedicle screw malposition were found to decrease from 5.1% of screws in the first fifty patients, to 2.0% in the last 50 patients.Only one screw was suboptimally placed at the end of surgery, which did not result in a neurological deficit.Pedicle screw placement accuracy continues to improve as the surgeon becomes more experienced with the technique.

View Article: PubMed Central - PubMed

Affiliation: Mater Misericordiae Private Hospital, South Brisbane, Queensland, Australia.

ABSTRACT

Objective: This study retrospectively assessed the accuracy of placement of lumbar pedicle screws placed by a single surgeon using a minimally-invasive, intra-operative CT-based computer navigated technique in combination with continuous electromyography (EMG) monitoring. The rates of incorrectly positioned screws were reviewed in the context of the surgeon's experience and learning curve.

Methods: Data was retrospectively reviewed from all consecutive minimally invasive lumbar fusions performed by the primary author over a period of over 4 years from April 2008 until October 2012. All cases that had utilized computer-assisted intra-operative CT-based image guidance and continuous EMG monitoring to guide percutaneous pedicle screw placement were analysed for the rates of malposition of the pedicle screws. Pedicle screw malposition was defined as having occurred if the screw trajectory was adjusted intraoperatively due to positive EMG responses, or due to breach of the pedicle cortex by more than 2mm on intraoperative CT imaging performed at the end of the instrumentation procedure. Further analysis of the data was undertaken to determine if the rates of malposition changed with the surgeon's experience with the technique.

Results: Six hundred and twenty-seven pedicle screws were placed in one hundred and fifty patients. The overall rate of intraoperative malposition and subsequent adjustment of pedicle screw placement was 3.8% (24 of 627 screws). Screw malposition was detected by intraoperative CT imaging. Warning of potential screw misplacement was provided by use of the EMG monitoring. With increased experience with the technique, rates of intraoperative pedicle screw malposition were found to decrease from 5.1% of screws in the first fifty patients, to 2.0% in the last 50 patients. Only one screw was suboptimally placed at the end of surgery, which did not result in a neurological deficit.

Conclusion: The use of CT-based computer-assisted navigation in combination with continuous EMG monitoring during percutaneous transpedicular screw placement results in very low rates of malposition and neural injury that compare favourably with previously reported rates. Pedicle screw placement accuracy continues to improve as the surgeon becomes more experienced with the technique.

No MeSH data available.


Related in: MedlinePlus