Operative and Perioperative Durations in O-Arm vs C-Arm Fluoroscopy for Lumbar Instrumentation

Operative and Perioperative Durations in O-Arm vs C-Arm Fluoroscopy for Lumbar Instrumentation Abstract BACKGROUND Intraoperative 3-dimensional fluoroscopy (eg, O-arm) has been shown to improve accuracy of pedicle screw placement over 2-dimensional fluoroscopy (C-arm), but its effect on surgery duration remains unclear. OBJECTIVE To compare the durations of operative and perioperative times between O-arm and C-arm procedures for degenerative lumbar disorders. METHODS We analyzed 198 patients representing 987 pedicle screws treated in a single center by 4 different surgeons between 2013 and 2015. Accuracy of pedicle screw placement was assessed using the Laine classification on postoperative CT scans. Operative and perioperative durations were prospectively reported on the procedure sheet by anesthesiologists. RESULTS As expected, placement of pedicle screws using O-arm navigation was overall more accurate compared to C-arm fluoroscopy (strictly intrapedicular screws: 549/663 = 82.8% vs 239/324 = 73.8%, P = .008). This benefit did not depend on surgeon individual performance (P = .17). Average operative duration per instrumented level was significantly shorter in the O-arm group (57.3 min vs 66.1 min, P = .02) but also depended on the surgeon, indication, and interbody fusion. However, only surgeon individual performance remained significantly associated with surgery duration in multivariate analysis (P < .001). Similarly, the only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001). CONCLUSION This study shows that O-arm navigation does not independently decrease operative duration, nor increases perioperative time, while improving accuracy of pedicle screw placement. Accuracy, C-arm, Duration, Instrumentation, O-arm, Spine Instrumented procedures of the lumbar spine have drastically increased over the last 20 yr, raising from 77 682 procedures in 1998 to 210 407 procedures in 2008 according to the US national registry.1 In the same period, average hospital charges associated with spinal fusion discharges raised from $24 676 to $81 960.1 Nevertheless, whether this important economic cost is balanced by a clear clinical benefit for patients compared to noninstrumented procedures has recently been questioned.2,3 In this context, ensuring the safety and efficacy of instrumented osteosynthesis is crucial. Several methods are currently used to monitor pedicle screw placement during surgery. Among them, C-arm fluoroscopy is considered as the standard of care but is still associated with a significant number of misplacements: in a large survey including 1236 thoracolumbar screws in 273 consecutive patients, pedicle breaches were identified in 20% of postoperative CT scans, with severe (>4 mm) violations in 3.8% of the cases.4 Other methods for monitoring pedicle screws placement have been proposed, from electrical conductivity measurement systems5 to computer-assisted navigation.6 Computer guidance systems based on intraoperative data acquisition, such as the O-arm system (Medtronic, Dublin, Ireland), ensure a high rate of correct pedicle screw placement. In a large multicenter study, 97.5% of pedicle screws in 353 patients were correctly placed using the O-arm.7 However, whether this benefit regarding pedicle screw placement accuracy comes at a cost in terms of surgery duration and to what extent it depends on the surgeon himself hasnever been assessed. The goal of our study was to compare accuracy and durations between procedures relying on either C-arm or O-arm monitoring taking into account surgeon individual performance. METHODS We conducted a retrospective cohort study in a single adult neurosurgical center. We included all consecutive patients who underwent surgery with instrumented fusion for degenerative lumbar spinal disorders (stenosis, discopathy, spondylolisthesis, scoliosis) between 2012 and 2014. Patients with missing data (n = 15) and patients who already had lumbar surgery (n = 24) were excluded. Observational studies do not require ethics committee approval and patient informed consent at our institution, and therefore these were not sought. Procedures were performed under O-arm or C-arm fluoroscopy according to surgeon preference. Four senior neurosurgeons participated in the study. Medical variables of interest were extracted from patient reports while durations of surgery and anesthesia were obtained from operative reports that were prospectively informed by anesthesiologists. For each patient, accuracy of pedicle screw placement was analyzed on postoperative CT scans or 3-dimensional fluoroscopy reconstructions based on the Laine classification, where Laine 0 is a strictly intrapedicular screw; Laine I is a minor pedicle perforation (0-2 mm); Laine II is a moderate pedicle perforation (2-4 mm); Laine III is a severe pedicle perforation (4-6 mm); Laine IV is a complete extrapedicular trajectory.8 Operative duration was defined as the duration between incision and closure, as reported by the anesthesiologist. To compare procedures, we calculated the surgical duration per instrumented spinal level. Perioperative duration was defined as the time during which the patient was in the operating room minus the duration of the surgery. Univariate analysis was conducted using χ2 tests for categorical variables and analysis of variance for multiple continuous variables. Multivariate analysis was conducted using logistical or linear regression for categorical and continuous variables, respectively. Statistical analysis was performed with SPSS 20 (IBM, Armonk, New York). RESULTS Overall, 198 patients were included in this study: 123 patients were operated under O-arm navigation and 75 patients under C-arm navigation (Table 1). Demographic variables were similar in both groups. Indications differed in that patients with degenerative scoliosis (n = 9) were only operated under O-arm navigation. Each surgeon had a clear preference for 1 system, with 2 surgeons favoring each navigation modality (Table 1). There was no significant difference regarding complications requiring reoperations between the O-arm and C-arm procedures (3 vs 2 infections, 0 vs 1 hematoma, 5 vs 4 adjacent segment disease, 1 vs 1 pseudarthrosis, 3 vs 1 persistent radiculopathy). TABLE 1. Patients Characteristics     O-arm (n = 123)  C-arm (n = 75)  Patient  Age (mean)  64.3 (27-88)  63.9 (26-87)    Sex  M/F = 58/65  M/F = 32/43    ASA (1-2-3)  n = 14-78-12  n = 10-47-8  Indication  Stenosis  56 (45.5%)  32 (42.7%)    Spondylolisthesis  34 (27.6%)  30 (40.0%)    Discopathy  24 (19.5%)  13 (17.3%)    Scoliosis  9 (7.3%)  0  Surgery  Surgeon (A-B-C-D)  n = 27-88-5-3  n = 1-9-54-11    Average nb. of levels  2.9 (2-8)  2.4 (2-5)    Interbody fusion  77 (62.6%)  60 (80%)    MIS  15 (12.2%)  11 (14.7%)      O-arm (n = 123)  C-arm (n = 75)  Patient  Age (mean)  64.3 (27-88)  63.9 (26-87)    Sex  M/F = 58/65  M/F = 32/43    ASA (1-2-3)  n = 14-78-12  n = 10-47-8  Indication  Stenosis  56 (45.5%)  32 (42.7%)    Spondylolisthesis  34 (27.6%)  30 (40.0%)    Discopathy  24 (19.5%)  13 (17.3%)    Scoliosis  9 (7.3%)  0  Surgery  Surgeon (A-B-C-D)  n = 27-88-5-3  n = 1-9-54-11    Average nb. of levels  2.9 (2-8)  2.4 (2-5)    Interbody fusion  77 (62.6%)  60 (80%)    MIS  15 (12.2%)  11 (14.7%)  MIS: minimally invasive surgery; nb: number; ASA: American Society of Anesthesiologists; M: male; F: female. View Large Regarding accuracy of pedicle screws placement, over a total of 987 pedicle screws, O-arm navigation was significantly associated with more strictly intrapedicular (Laine 0) screws (549/623 = 82.8%) than C-arm fluoroscopy (239/324 = 73.8%, P = .008). O-arm procedures were also associated with fewer severe or extrapedicular screws (14/663 = 2.1% vs 17/324 = 5.2%, P = .01; Table 2 and Figure 1A). However, because other confounding factors such as the indication and the surgeon himself can interfere with the accuracy of pedicle screws placement, we conducted a multivariate analysis including indication, surgeon, whether it was an interbody fusion or minimally invasive procedure and concluded that the benefit of O-arm over C-arm navigation persisted independently of the surgeon and indication (Table 2 and Figures 1B and 1C). FIGURE 1. View largeDownload slide O-arm navigation enhances pedicle screw placement accuracy independently of surgeon individual performance and indication. A, Percentage of pedicle screws according to Laine classification: over a total of 987 pedicle screws, O-arm navigation was significantly associated with more strictly intrapedicular (Laine 0) screws (549/623 = 82.8%) than C-arm fluoroscopy (239/324 = 73.8%, P = .008). O-arm procedures were also associated with fewer severe or extrapedicular screws (14/663 = 2.1% vs 17/324 = 5.2%, P = .01). B, In univariate and multivariate analysis, the benefit of O-arm over C-arm navigation persisted independently of the surgeon (P = .45 and P = .17 respectively), and C, indication (P = .40 and P = .44 respectively). FIGURE 1. View largeDownload slide O-arm navigation enhances pedicle screw placement accuracy independently of surgeon individual performance and indication. A, Percentage of pedicle screws according to Laine classification: over a total of 987 pedicle screws, O-arm navigation was significantly associated with more strictly intrapedicular (Laine 0) screws (549/623 = 82.8%) than C-arm fluoroscopy (239/324 = 73.8%, P = .008). O-arm procedures were also associated with fewer severe or extrapedicular screws (14/663 = 2.1% vs 17/324 = 5.2%, P = .01). B, In univariate and multivariate analysis, the benefit of O-arm over C-arm navigation persisted independently of the surgeon (P = .45 and P = .17 respectively), and C, indication (P = .40 and P = .44 respectively). TABLE 2. Accuracy of Pedicle Screws Placement     Accuracy: Laine  Univ  Multiv      0  I  II  III  IV  P  P  Group  O-arm  549  84  16  9  5  .008  .007    C-arm  239  55  13  11  6      Surgeon  A  100  17  7  1  1  .45  .17    B  433  68  10  9  5        C  197  43  9  7  4        D  58  11  3  3  1      Indication  Stenosis  400  65  16  9  6  .40  .44    Discopathy  89  15  1  0  1        Scoliosis  85  12  2  1  0        Spondylo.  214  47  10  10  4      MIS  No  433  87  17  11  4  .22  .99    Yes  59  7  0  0  0      Intersomatic  No  287  48  13  9  6  .53  .89    Yes  498  90  16  11  5          Accuracy: Laine  Univ  Multiv      0  I  II  III  IV  P  P  Group  O-arm  549  84  16  9  5  .008  .007    C-arm  239  55  13  11  6      Surgeon  A  100  17  7  1  1  .45  .17    B  433  68  10  9  5        C  197  43  9  7  4        D  58  11  3  3  1      Indication  Stenosis  400  65  16  9  6  .40  .44    Discopathy  89  15  1  0  1        Scoliosis  85  12  2  1  0        Spondylo.  214  47  10  10  4      MIS  No  433  87  17  11  4  .22  .99    Yes  59  7  0  0  0      Intersomatic  No  287  48  13  9  6  .53  .89    Yes  498  90  16  11  5      MIS: minimally invasive surgery; Univ.: univariate analysis; “Multiv.”: multivariate analysis; Spondylo.: spondylolisthesis. View Large We next analyzed durations of operative and perioperative times to see whether the benefit of O-arm fluoroscopy in terms of accuracy was associated with either longer or shorted durations. In univariate analysis, it seemed that O-arm navigation was associated with shorter operative durations per instrumented spinal level (57.3 min vs 66.1 min, P = .02; Table 3 and Figure 2A). Similarly, interbody fusions (65.5 vs 52.4 min, P = .001) and indication (P < .001) seemed to interfere with surgery duration. However, in multivariate analysis including confounding factors, only surgeon individual performance remained significantly associated with shorter operative durations (P < .001; Table 3 and Figure 2B). To look for an effect of experience in either accuracy of pedicle screw placement or duration of surgery using the O-arm, we plotted these data per surgeon over time, and found no “learning curve” effect (Figure, Supplemental Digital Content). FIGURE 2. View largeDownload slide O-arm navigation does not reduce operative duration independently of surgeon nor increase perioperative duration. A, Although it seemed that O-arm navigation was associated with shorter operative durations per instrumented spinal level (57.3 min vs 66.1 min, P = .02) in univariate analysis, this result was negative in multivariate analysis (P = .36). B, In multivariate analysis, only surgeon individual performance remained significantly associated with shorter operative durations (P < .001). C, O-arm and C-arm navigation were associated with similar perioperative durations (57.4 vs 58.3 min, univariate: P = .78; multivariate: P = .29). D, The only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001) FIGURE 2. View largeDownload slide O-arm navigation does not reduce operative duration independently of surgeon nor increase perioperative duration. A, Although it seemed that O-arm navigation was associated with shorter operative durations per instrumented spinal level (57.3 min vs 66.1 min, P = .02) in univariate analysis, this result was negative in multivariate analysis (P = .36). B, In multivariate analysis, only surgeon individual performance remained significantly associated with shorter operative durations (P < .001). C, O-arm and C-arm navigation were associated with similar perioperative durations (57.4 vs 58.3 min, univariate: P = .78; multivariate: P = .29). D, The only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001) TABLE 3. Operative and Perioperative Durations     Operative duration per instrumented level (min)  Perioperative duration (min)      Mean  Univ.  Multiv.  Mean  Univ.  Multiv.  Group  O-arm  57.3  .02  .36  57.4  .78  .29    C-arm  66.1      58.3      Surgeon  A (O/C-arm)  77.6 (72.6/95.7)  <.001 (< .01)  <.001  63.5 (59.8/76.0)  .001 (.06)  .12    B (O/C-arm)  48.3 (42.0/48.5)      54.1 (55.0/53.8)        C(O/C-arm)  63.0 (61.9/68.0)      52.5 (58.2/51.5)        D (O/C-arm)  75.8 (73.0/76.7)      72.5 (72.7/72.3)      Indication  Stenosis  63.3  <.001  0.51  64.5  <.001  <.001    Discopathy  61.3      47.2        Scoliosis  32.3      75.0        Spondylo.  64.0      54.5      MIS  No  62.9  .06  0.85  60.7  .001  .72    Yes  54.9      46.7      Intersomatic  No  52.4  .001  0.28  63.8  .014  .27    Yes  65.5      55.0          Operative duration per instrumented level (min)  Perioperative duration (min)      Mean  Univ.  Multiv.  Mean  Univ.  Multiv.  Group  O-arm  57.3  .02  .36  57.4  .78  .29    C-arm  66.1      58.3      Surgeon  A (O/C-arm)  77.6 (72.6/95.7)  <.001 (< .01)  <.001  63.5 (59.8/76.0)  .001 (.06)  .12    B (O/C-arm)  48.3 (42.0/48.5)      54.1 (55.0/53.8)        C(O/C-arm)  63.0 (61.9/68.0)      52.5 (58.2/51.5)        D (O/C-arm)  75.8 (73.0/76.7)      72.5 (72.7/72.3)      Indication  Stenosis  63.3  <.001  0.51  64.5  <.001  <.001    Discopathy  61.3      47.2        Scoliosis  32.3      75.0        Spondylo.  64.0      54.5      MIS  No  62.9  .06  0.85  60.7  .001  .72    Yes  54.9      46.7      Intersomatic  No  52.4  .001  0.28  63.8  .014  .27    Yes  65.5      55.0      MIS: minimally invasive surgery; Univ.: univariate analysis; “Multiv.”: multivariate analysis; Spondylo.: spondylolisthesis. View Large Lastly, we compared perioperative durations to see whether installation and uninstallation of the O-arm navigation system had an impact. We showed that both O-arm and C-arm navigation were associated with similar perioperative durations (57.4 vs 58.3 min, P = .78; Figure 2C). Although surgeon, indication, interbody fusion, or minimally invasive procedures seemed to interfere with perioperative durations in univariate analysis, the only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001, Table 3 and Figure 2D). DISCUSSION This study was conducted in order to examine the balance between accuracy and durations when considering O-arm vs C-arm navigation in lumbar instrumentation, taking into account individual performance of the surgeon relative to these 2 former factors. Based on this retrospective study involving 4 surgeons, 198 patients, and 987 pedicle screws, we demonstrated that (1) O-arm navigation is associated with improved accuracy, avoiding severe pedicle perforations and increasing the percentage of strictly intrapedicular screws; (2) O-arm navigation does not independently lead to shorter surgical durations nor to longer perioperative durations; (3) improved accuracy with O-arm navigation does not depend on surgeon individual performance but operative duration does. As with all retrospective studies, these conclusions must be interpreted cautiously. In particular, the fact that each surgeon had a preferred method of navigation could have statistically biased the results. However, it also allowed the surgeon to choose the navigation modality he felt the most comfortable with and therefore corroborates our conclusions regarding accuracy and duration. Because immediate postoperative CT scans as well as operative reports were documented prospectively and systematically for each patient undergoing lumbar instrumentation in our department, biases associated with the retrospective design of the study are minimized, as evidenced by the small number of patients with missing data. Intraoperative 3-dimensional navigation, such as the O-arm and StealthStation® systems (Medtronic), has been associated with enhanced pedicle screw placement accuracy in both open and percutaneous thoracolumbar procedures.7,9,10 Another clear benefit of O-arm navigation is the reduction of radiation exposure to the surgeon,11 while increased exposure to the patient may be compensated by avoiding immediate postoperative CT scans.12,13 Lastly, cost-effectiveness studies demonstrated that O-arm monitoring is overall less costly by reducing reoperation rates and the need for postoperative CT scans.14,15 CONCLUSION The interplay between the navigation system, surgeon indi-vidual performance, and operative and perioperative durations has, to our knowledge, never been examined. Here, we confirm that O-arm navigation improves accuracy independently of surgeon performance and demonstrate that the surgeon is the only independent determinant of operative duration, whereas patient condition drives perioperative duration. Altogether, this study emphasizes the dynamics between innovative tools and individual skills in improving surgical outcomes. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Rajaee SS, Bae HW, Kanim LEA, Delamarter RB. Spinal fusion in the United States: analysis of trends from 1998 to 2008. Spine . 2012; 37( 1): 67- 76. Google Scholar CrossRef Search ADS PubMed  2. Försth P, Ólafsson G, Carlsson T et al.   A randomized, controlled trial of fusion surgery for lumbar spinal stenosis. N Engl J Med . 2016; 374( 15): 1413- 1423. Google Scholar CrossRef Search ADS PubMed  3. Ghogawala Z, Dziura J, Butler WE et al.   Laminectomy plus fusion versus laminectomy alone for lumbar spondylolisthesis. N Engl J Med . 2016; 374( 15): 1424- 1434. Google Scholar CrossRef Search ADS PubMed  4. Nevzati E, Marbacher S, Soleman J et al.   Accuracy of pedicle screw placement in the thoracic and lumbosacral spine using a conventional intraoperative fluoroscopy-guided technique: a national neurosurgical education and training center analysis of 1236 consecutive screws. World Neurosurg . 2014; 82( 5): 866- 71.e1- 2. doi:10.1016/j.wneu.2014.06.023. Google Scholar CrossRef Search ADS PubMed  5. Bolger C, Kelleher MO, McEvoy L et al.   Electrical conductivity measurement: a new technique to detect iatrogenic initial pedicle perforation. Eur Spine J . 2007; 16( 11): 1919- 1924. Google Scholar CrossRef Search ADS PubMed  6. Costa F, Cardia A, Ortolina A, Fabio G, Zerbi A, Fornari M. Spinal navigation: standard preoperative versus intraoperative computed tomography data set acquisition for computer-guidance system: radiological and clinical study in 100 consecutive patients. Spine . 2011; 36( 24): 2094- 2098. Google Scholar CrossRef Search ADS PubMed  7. Van de Kelft E, Costa F, Van der Planken D, Schils F. A prospective multicenter registry on the accuracy of pedicle screw placement in the thoracic, lumbar, and sacral levels with the use of the O-arm imaging system and StealthStation navigation. Spine . 2012; 37( 25): E1580- E1587. Google Scholar CrossRef Search ADS PubMed  8. Laine T, Schlenzka D, Mäkitalo K, Tallroth K, Nolte LP, Visarius H. Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients. Spine . 1997; 22( 11): 1254- 1258. Google Scholar CrossRef Search ADS PubMed  9. Ohba T, Ebata S, Fujita K, Sato H, Haro H. Percutaneous pedicle screw placements: accuracy and rates of cranial facet joint violation using conventional fluoroscopy compared with intraoperative three-dimensional computed tomography computer navigation. Eur Spine J . 2016; 25( 6): 1775- 1780. Google Scholar CrossRef Search ADS PubMed  10. Yson SC, Sembrano JN, Sanders PC, Santos ERG, Ledonio CGT, Polly DW Jr. Comparison of cranial facet joint violation rates between open and percutaneous pedicle screw placement using intraoperative 3-D CT (O-arm) computer navigation. Spine . 2013; 38( 4): E251- E258. Google Scholar CrossRef Search ADS PubMed  11. Abdullah KG, Bishop FS, Lubelski D, Steinmetz MP, Benzel EC, Mroz TE. Radiation exposure to the spine surgeon in lumbar and thoracolumbar fusions with the use of an intraoperative computed tomographic 3-dimensional imaging system. Spine . 2012; 37( 17): E1074- E1078. Google Scholar CrossRef Search ADS PubMed  12. Mendelsohn D, Strelzow J, Dea N et al.   Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation. Spine J . 2016; 16( 3): 343- 354. Google Scholar CrossRef Search ADS PubMed  13. Lange J, Karellas A, Street J et al.   Estimating the effective radiation dose imparted to patients by intraoperative cone-beam computed tomography in thoracolumbar spinal surgery. Spine . 2013; 38( 5): E306- E312. Google Scholar CrossRef Search ADS PubMed  14. Sanborn MR, Thawani JP, Whitmore RG et al.   Cost-effectiveness of confirmatory techniques for the placement of lumbar pedicle screws. Neurosurg Focus . 2012; 33( 1): E12- E18. Google Scholar CrossRef Search ADS PubMed  15. Dea N, Fisher CG, Batke J et al.   Economic evaluation comparing intraoperative cone beam CT-based navigation and conventional fluoroscopy for the placement of spinal pedicle screws: a patient-level data cost-effectiveness analysis. Spine J . 2016; 16( 1): 23- 31. Google Scholar CrossRef Search ADS PubMed  Supplemental digital content is available for this article at operativeneurosurgery-online.com. COMMENT The authors performed a retrospective single center study looking at the relationship between utilization of spinal navigation and operative time in a relatively simple case-mix of patients. The main bias of this study is that surgeons decided if they were using the navigation or not, which introduces a selection bias, and could have selected more challenging cases for the navigation cohort, and potentially longer cases as well. While the improved accuracy of pedicle screw placement with navigation is well-established, high acquisition costs and longer operative time seem to be the principal obstacles to a more widespread usage of this technology. This study adds to the literature by showing, like others have found, that surgical navigation does not impact significantly operative duration and that other factors, like individual surgeon performance and surgical indication, are the main drivers of surgical time. Nicolas Dea Sherbrooke, Canada Copyright © 2017 by the Congress of Neurological Surgeons http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Operative Neurosurgery Oxford University Press

Operative and Perioperative Durations in O-Arm vs C-Arm Fluoroscopy for Lumbar Instrumentation

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Abstract

Abstract BACKGROUND Intraoperative 3-dimensional fluoroscopy (eg, O-arm) has been shown to improve accuracy of pedicle screw placement over 2-dimensional fluoroscopy (C-arm), but its effect on surgery duration remains unclear. OBJECTIVE To compare the durations of operative and perioperative times between O-arm and C-arm procedures for degenerative lumbar disorders. METHODS We analyzed 198 patients representing 987 pedicle screws treated in a single center by 4 different surgeons between 2013 and 2015. Accuracy of pedicle screw placement was assessed using the Laine classification on postoperative CT scans. Operative and perioperative durations were prospectively reported on the procedure sheet by anesthesiologists. RESULTS As expected, placement of pedicle screws using O-arm navigation was overall more accurate compared to C-arm fluoroscopy (strictly intrapedicular screws: 549/663 = 82.8% vs 239/324 = 73.8%, P = .008). This benefit did not depend on surgeon individual performance (P = .17). Average operative duration per instrumented level was significantly shorter in the O-arm group (57.3 min vs 66.1 min, P = .02) but also depended on the surgeon, indication, and interbody fusion. However, only surgeon individual performance remained significantly associated with surgery duration in multivariate analysis (P < .001). Similarly, the only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001). CONCLUSION This study shows that O-arm navigation does not independently decrease operative duration, nor increases perioperative time, while improving accuracy of pedicle screw placement. Accuracy, C-arm, Duration, Instrumentation, O-arm, Spine Instrumented procedures of the lumbar spine have drastically increased over the last 20 yr, raising from 77 682 procedures in 1998 to 210 407 procedures in 2008 according to the US national registry.1 In the same period, average hospital charges associated with spinal fusion discharges raised from $24 676 to $81 960.1 Nevertheless, whether this important economic cost is balanced by a clear clinical benefit for patients compared to noninstrumented procedures has recently been questioned.2,3 In this context, ensuring the safety and efficacy of instrumented osteosynthesis is crucial. Several methods are currently used to monitor pedicle screw placement during surgery. Among them, C-arm fluoroscopy is considered as the standard of care but is still associated with a significant number of misplacements: in a large survey including 1236 thoracolumbar screws in 273 consecutive patients, pedicle breaches were identified in 20% of postoperative CT scans, with severe (>4 mm) violations in 3.8% of the cases.4 Other methods for monitoring pedicle screws placement have been proposed, from electrical conductivity measurement systems5 to computer-assisted navigation.6 Computer guidance systems based on intraoperative data acquisition, such as the O-arm system (Medtronic, Dublin, Ireland), ensure a high rate of correct pedicle screw placement. In a large multicenter study, 97.5% of pedicle screws in 353 patients were correctly placed using the O-arm.7 However, whether this benefit regarding pedicle screw placement accuracy comes at a cost in terms of surgery duration and to what extent it depends on the surgeon himself hasnever been assessed. The goal of our study was to compare accuracy and durations between procedures relying on either C-arm or O-arm monitoring taking into account surgeon individual performance. METHODS We conducted a retrospective cohort study in a single adult neurosurgical center. We included all consecutive patients who underwent surgery with instrumented fusion for degenerative lumbar spinal disorders (stenosis, discopathy, spondylolisthesis, scoliosis) between 2012 and 2014. Patients with missing data (n = 15) and patients who already had lumbar surgery (n = 24) were excluded. Observational studies do not require ethics committee approval and patient informed consent at our institution, and therefore these were not sought. Procedures were performed under O-arm or C-arm fluoroscopy according to surgeon preference. Four senior neurosurgeons participated in the study. Medical variables of interest were extracted from patient reports while durations of surgery and anesthesia were obtained from operative reports that were prospectively informed by anesthesiologists. For each patient, accuracy of pedicle screw placement was analyzed on postoperative CT scans or 3-dimensional fluoroscopy reconstructions based on the Laine classification, where Laine 0 is a strictly intrapedicular screw; Laine I is a minor pedicle perforation (0-2 mm); Laine II is a moderate pedicle perforation (2-4 mm); Laine III is a severe pedicle perforation (4-6 mm); Laine IV is a complete extrapedicular trajectory.8 Operative duration was defined as the duration between incision and closure, as reported by the anesthesiologist. To compare procedures, we calculated the surgical duration per instrumented spinal level. Perioperative duration was defined as the time during which the patient was in the operating room minus the duration of the surgery. Univariate analysis was conducted using χ2 tests for categorical variables and analysis of variance for multiple continuous variables. Multivariate analysis was conducted using logistical or linear regression for categorical and continuous variables, respectively. Statistical analysis was performed with SPSS 20 (IBM, Armonk, New York). RESULTS Overall, 198 patients were included in this study: 123 patients were operated under O-arm navigation and 75 patients under C-arm navigation (Table 1). Demographic variables were similar in both groups. Indications differed in that patients with degenerative scoliosis (n = 9) were only operated under O-arm navigation. Each surgeon had a clear preference for 1 system, with 2 surgeons favoring each navigation modality (Table 1). There was no significant difference regarding complications requiring reoperations between the O-arm and C-arm procedures (3 vs 2 infections, 0 vs 1 hematoma, 5 vs 4 adjacent segment disease, 1 vs 1 pseudarthrosis, 3 vs 1 persistent radiculopathy). TABLE 1. Patients Characteristics     O-arm (n = 123)  C-arm (n = 75)  Patient  Age (mean)  64.3 (27-88)  63.9 (26-87)    Sex  M/F = 58/65  M/F = 32/43    ASA (1-2-3)  n = 14-78-12  n = 10-47-8  Indication  Stenosis  56 (45.5%)  32 (42.7%)    Spondylolisthesis  34 (27.6%)  30 (40.0%)    Discopathy  24 (19.5%)  13 (17.3%)    Scoliosis  9 (7.3%)  0  Surgery  Surgeon (A-B-C-D)  n = 27-88-5-3  n = 1-9-54-11    Average nb. of levels  2.9 (2-8)  2.4 (2-5)    Interbody fusion  77 (62.6%)  60 (80%)    MIS  15 (12.2%)  11 (14.7%)      O-arm (n = 123)  C-arm (n = 75)  Patient  Age (mean)  64.3 (27-88)  63.9 (26-87)    Sex  M/F = 58/65  M/F = 32/43    ASA (1-2-3)  n = 14-78-12  n = 10-47-8  Indication  Stenosis  56 (45.5%)  32 (42.7%)    Spondylolisthesis  34 (27.6%)  30 (40.0%)    Discopathy  24 (19.5%)  13 (17.3%)    Scoliosis  9 (7.3%)  0  Surgery  Surgeon (A-B-C-D)  n = 27-88-5-3  n = 1-9-54-11    Average nb. of levels  2.9 (2-8)  2.4 (2-5)    Interbody fusion  77 (62.6%)  60 (80%)    MIS  15 (12.2%)  11 (14.7%)  MIS: minimally invasive surgery; nb: number; ASA: American Society of Anesthesiologists; M: male; F: female. View Large Regarding accuracy of pedicle screws placement, over a total of 987 pedicle screws, O-arm navigation was significantly associated with more strictly intrapedicular (Laine 0) screws (549/623 = 82.8%) than C-arm fluoroscopy (239/324 = 73.8%, P = .008). O-arm procedures were also associated with fewer severe or extrapedicular screws (14/663 = 2.1% vs 17/324 = 5.2%, P = .01; Table 2 and Figure 1A). However, because other confounding factors such as the indication and the surgeon himself can interfere with the accuracy of pedicle screws placement, we conducted a multivariate analysis including indication, surgeon, whether it was an interbody fusion or minimally invasive procedure and concluded that the benefit of O-arm over C-arm navigation persisted independently of the surgeon and indication (Table 2 and Figures 1B and 1C). FIGURE 1. View largeDownload slide O-arm navigation enhances pedicle screw placement accuracy independently of surgeon individual performance and indication. A, Percentage of pedicle screws according to Laine classification: over a total of 987 pedicle screws, O-arm navigation was significantly associated with more strictly intrapedicular (Laine 0) screws (549/623 = 82.8%) than C-arm fluoroscopy (239/324 = 73.8%, P = .008). O-arm procedures were also associated with fewer severe or extrapedicular screws (14/663 = 2.1% vs 17/324 = 5.2%, P = .01). B, In univariate and multivariate analysis, the benefit of O-arm over C-arm navigation persisted independently of the surgeon (P = .45 and P = .17 respectively), and C, indication (P = .40 and P = .44 respectively). FIGURE 1. View largeDownload slide O-arm navigation enhances pedicle screw placement accuracy independently of surgeon individual performance and indication. A, Percentage of pedicle screws according to Laine classification: over a total of 987 pedicle screws, O-arm navigation was significantly associated with more strictly intrapedicular (Laine 0) screws (549/623 = 82.8%) than C-arm fluoroscopy (239/324 = 73.8%, P = .008). O-arm procedures were also associated with fewer severe or extrapedicular screws (14/663 = 2.1% vs 17/324 = 5.2%, P = .01). B, In univariate and multivariate analysis, the benefit of O-arm over C-arm navigation persisted independently of the surgeon (P = .45 and P = .17 respectively), and C, indication (P = .40 and P = .44 respectively). TABLE 2. Accuracy of Pedicle Screws Placement     Accuracy: Laine  Univ  Multiv      0  I  II  III  IV  P  P  Group  O-arm  549  84  16  9  5  .008  .007    C-arm  239  55  13  11  6      Surgeon  A  100  17  7  1  1  .45  .17    B  433  68  10  9  5        C  197  43  9  7  4        D  58  11  3  3  1      Indication  Stenosis  400  65  16  9  6  .40  .44    Discopathy  89  15  1  0  1        Scoliosis  85  12  2  1  0        Spondylo.  214  47  10  10  4      MIS  No  433  87  17  11  4  .22  .99    Yes  59  7  0  0  0      Intersomatic  No  287  48  13  9  6  .53  .89    Yes  498  90  16  11  5          Accuracy: Laine  Univ  Multiv      0  I  II  III  IV  P  P  Group  O-arm  549  84  16  9  5  .008  .007    C-arm  239  55  13  11  6      Surgeon  A  100  17  7  1  1  .45  .17    B  433  68  10  9  5        C  197  43  9  7  4        D  58  11  3  3  1      Indication  Stenosis  400  65  16  9  6  .40  .44    Discopathy  89  15  1  0  1        Scoliosis  85  12  2  1  0        Spondylo.  214  47  10  10  4      MIS  No  433  87  17  11  4  .22  .99    Yes  59  7  0  0  0      Intersomatic  No  287  48  13  9  6  .53  .89    Yes  498  90  16  11  5      MIS: minimally invasive surgery; Univ.: univariate analysis; “Multiv.”: multivariate analysis; Spondylo.: spondylolisthesis. View Large We next analyzed durations of operative and perioperative times to see whether the benefit of O-arm fluoroscopy in terms of accuracy was associated with either longer or shorted durations. In univariate analysis, it seemed that O-arm navigation was associated with shorter operative durations per instrumented spinal level (57.3 min vs 66.1 min, P = .02; Table 3 and Figure 2A). Similarly, interbody fusions (65.5 vs 52.4 min, P = .001) and indication (P < .001) seemed to interfere with surgery duration. However, in multivariate analysis including confounding factors, only surgeon individual performance remained significantly associated with shorter operative durations (P < .001; Table 3 and Figure 2B). To look for an effect of experience in either accuracy of pedicle screw placement or duration of surgery using the O-arm, we plotted these data per surgeon over time, and found no “learning curve” effect (Figure, Supplemental Digital Content). FIGURE 2. View largeDownload slide O-arm navigation does not reduce operative duration independently of surgeon nor increase perioperative duration. A, Although it seemed that O-arm navigation was associated with shorter operative durations per instrumented spinal level (57.3 min vs 66.1 min, P = .02) in univariate analysis, this result was negative in multivariate analysis (P = .36). B, In multivariate analysis, only surgeon individual performance remained significantly associated with shorter operative durations (P < .001). C, O-arm and C-arm navigation were associated with similar perioperative durations (57.4 vs 58.3 min, univariate: P = .78; multivariate: P = .29). D, The only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001) FIGURE 2. View largeDownload slide O-arm navigation does not reduce operative duration independently of surgeon nor increase perioperative duration. A, Although it seemed that O-arm navigation was associated with shorter operative durations per instrumented spinal level (57.3 min vs 66.1 min, P = .02) in univariate analysis, this result was negative in multivariate analysis (P = .36). B, In multivariate analysis, only surgeon individual performance remained significantly associated with shorter operative durations (P < .001). C, O-arm and C-arm navigation were associated with similar perioperative durations (57.4 vs 58.3 min, univariate: P = .78; multivariate: P = .29). D, The only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001) TABLE 3. Operative and Perioperative Durations     Operative duration per instrumented level (min)  Perioperative duration (min)      Mean  Univ.  Multiv.  Mean  Univ.  Multiv.  Group  O-arm  57.3  .02  .36  57.4  .78  .29    C-arm  66.1      58.3      Surgeon  A (O/C-arm)  77.6 (72.6/95.7)  <.001 (< .01)  <.001  63.5 (59.8/76.0)  .001 (.06)  .12    B (O/C-arm)  48.3 (42.0/48.5)      54.1 (55.0/53.8)        C(O/C-arm)  63.0 (61.9/68.0)      52.5 (58.2/51.5)        D (O/C-arm)  75.8 (73.0/76.7)      72.5 (72.7/72.3)      Indication  Stenosis  63.3  <.001  0.51  64.5  <.001  <.001    Discopathy  61.3      47.2        Scoliosis  32.3      75.0        Spondylo.  64.0      54.5      MIS  No  62.9  .06  0.85  60.7  .001  .72    Yes  54.9      46.7      Intersomatic  No  52.4  .001  0.28  63.8  .014  .27    Yes  65.5      55.0          Operative duration per instrumented level (min)  Perioperative duration (min)      Mean  Univ.  Multiv.  Mean  Univ.  Multiv.  Group  O-arm  57.3  .02  .36  57.4  .78  .29    C-arm  66.1      58.3      Surgeon  A (O/C-arm)  77.6 (72.6/95.7)  <.001 (< .01)  <.001  63.5 (59.8/76.0)  .001 (.06)  .12    B (O/C-arm)  48.3 (42.0/48.5)      54.1 (55.0/53.8)        C(O/C-arm)  63.0 (61.9/68.0)      52.5 (58.2/51.5)        D (O/C-arm)  75.8 (73.0/76.7)      72.5 (72.7/72.3)      Indication  Stenosis  63.3  <.001  0.51  64.5  <.001  <.001    Discopathy  61.3      47.2        Scoliosis  32.3      75.0        Spondylo.  64.0      54.5      MIS  No  62.9  .06  0.85  60.7  .001  .72    Yes  54.9      46.7      Intersomatic  No  52.4  .001  0.28  63.8  .014  .27    Yes  65.5      55.0      MIS: minimally invasive surgery; Univ.: univariate analysis; “Multiv.”: multivariate analysis; Spondylo.: spondylolisthesis. View Large Lastly, we compared perioperative durations to see whether installation and uninstallation of the O-arm navigation system had an impact. We showed that both O-arm and C-arm navigation were associated with similar perioperative durations (57.4 vs 58.3 min, P = .78; Figure 2C). Although surgeon, indication, interbody fusion, or minimally invasive procedures seemed to interfere with perioperative durations in univariate analysis, the only factor that remained significantly associated with longer perioperative durations in multivariate analysis was the indication of surgery (P < .001, Table 3 and Figure 2D). DISCUSSION This study was conducted in order to examine the balance between accuracy and durations when considering O-arm vs C-arm navigation in lumbar instrumentation, taking into account individual performance of the surgeon relative to these 2 former factors. Based on this retrospective study involving 4 surgeons, 198 patients, and 987 pedicle screws, we demonstrated that (1) O-arm navigation is associated with improved accuracy, avoiding severe pedicle perforations and increasing the percentage of strictly intrapedicular screws; (2) O-arm navigation does not independently lead to shorter surgical durations nor to longer perioperative durations; (3) improved accuracy with O-arm navigation does not depend on surgeon individual performance but operative duration does. As with all retrospective studies, these conclusions must be interpreted cautiously. In particular, the fact that each surgeon had a preferred method of navigation could have statistically biased the results. However, it also allowed the surgeon to choose the navigation modality he felt the most comfortable with and therefore corroborates our conclusions regarding accuracy and duration. Because immediate postoperative CT scans as well as operative reports were documented prospectively and systematically for each patient undergoing lumbar instrumentation in our department, biases associated with the retrospective design of the study are minimized, as evidenced by the small number of patients with missing data. Intraoperative 3-dimensional navigation, such as the O-arm and StealthStation® systems (Medtronic), has been associated with enhanced pedicle screw placement accuracy in both open and percutaneous thoracolumbar procedures.7,9,10 Another clear benefit of O-arm navigation is the reduction of radiation exposure to the surgeon,11 while increased exposure to the patient may be compensated by avoiding immediate postoperative CT scans.12,13 Lastly, cost-effectiveness studies demonstrated that O-arm monitoring is overall less costly by reducing reoperation rates and the need for postoperative CT scans.14,15 CONCLUSION The interplay between the navigation system, surgeon indi-vidual performance, and operative and perioperative durations has, to our knowledge, never been examined. Here, we confirm that O-arm navigation improves accuracy independently of surgeon performance and demonstrate that the surgeon is the only independent determinant of operative duration, whereas patient condition drives perioperative duration. Altogether, this study emphasizes the dynamics between innovative tools and individual skills in improving surgical outcomes. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Rajaee SS, Bae HW, Kanim LEA, Delamarter RB. Spinal fusion in the United States: analysis of trends from 1998 to 2008. Spine . 2012; 37( 1): 67- 76. Google Scholar CrossRef Search ADS PubMed  2. Försth P, Ólafsson G, Carlsson T et al.   A randomized, controlled trial of fusion surgery for lumbar spinal stenosis. N Engl J Med . 2016; 374( 15): 1413- 1423. Google Scholar CrossRef Search ADS PubMed  3. Ghogawala Z, Dziura J, Butler WE et al.   Laminectomy plus fusion versus laminectomy alone for lumbar spondylolisthesis. N Engl J Med . 2016; 374( 15): 1424- 1434. Google Scholar CrossRef Search ADS PubMed  4. Nevzati E, Marbacher S, Soleman J et al.   Accuracy of pedicle screw placement in the thoracic and lumbosacral spine using a conventional intraoperative fluoroscopy-guided technique: a national neurosurgical education and training center analysis of 1236 consecutive screws. World Neurosurg . 2014; 82( 5): 866- 71.e1- 2. doi:10.1016/j.wneu.2014.06.023. Google Scholar CrossRef Search ADS PubMed  5. Bolger C, Kelleher MO, McEvoy L et al.   Electrical conductivity measurement: a new technique to detect iatrogenic initial pedicle perforation. Eur Spine J . 2007; 16( 11): 1919- 1924. Google Scholar CrossRef Search ADS PubMed  6. Costa F, Cardia A, Ortolina A, Fabio G, Zerbi A, Fornari M. Spinal navigation: standard preoperative versus intraoperative computed tomography data set acquisition for computer-guidance system: radiological and clinical study in 100 consecutive patients. Spine . 2011; 36( 24): 2094- 2098. Google Scholar CrossRef Search ADS PubMed  7. Van de Kelft E, Costa F, Van der Planken D, Schils F. A prospective multicenter registry on the accuracy of pedicle screw placement in the thoracic, lumbar, and sacral levels with the use of the O-arm imaging system and StealthStation navigation. Spine . 2012; 37( 25): E1580- E1587. Google Scholar CrossRef Search ADS PubMed  8. Laine T, Schlenzka D, Mäkitalo K, Tallroth K, Nolte LP, Visarius H. Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients. Spine . 1997; 22( 11): 1254- 1258. Google Scholar CrossRef Search ADS PubMed  9. Ohba T, Ebata S, Fujita K, Sato H, Haro H. Percutaneous pedicle screw placements: accuracy and rates of cranial facet joint violation using conventional fluoroscopy compared with intraoperative three-dimensional computed tomography computer navigation. Eur Spine J . 2016; 25( 6): 1775- 1780. Google Scholar CrossRef Search ADS PubMed  10. Yson SC, Sembrano JN, Sanders PC, Santos ERG, Ledonio CGT, Polly DW Jr. Comparison of cranial facet joint violation rates between open and percutaneous pedicle screw placement using intraoperative 3-D CT (O-arm) computer navigation. Spine . 2013; 38( 4): E251- E258. Google Scholar CrossRef Search ADS PubMed  11. Abdullah KG, Bishop FS, Lubelski D, Steinmetz MP, Benzel EC, Mroz TE. Radiation exposure to the spine surgeon in lumbar and thoracolumbar fusions with the use of an intraoperative computed tomographic 3-dimensional imaging system. Spine . 2012; 37( 17): E1074- E1078. Google Scholar CrossRef Search ADS PubMed  12. Mendelsohn D, Strelzow J, Dea N et al.   Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation. Spine J . 2016; 16( 3): 343- 354. Google Scholar CrossRef Search ADS PubMed  13. Lange J, Karellas A, Street J et al.   Estimating the effective radiation dose imparted to patients by intraoperative cone-beam computed tomography in thoracolumbar spinal surgery. Spine . 2013; 38( 5): E306- E312. Google Scholar CrossRef Search ADS PubMed  14. Sanborn MR, Thawani JP, Whitmore RG et al.   Cost-effectiveness of confirmatory techniques for the placement of lumbar pedicle screws. Neurosurg Focus . 2012; 33( 1): E12- E18. Google Scholar CrossRef Search ADS PubMed  15. Dea N, Fisher CG, Batke J et al.   Economic evaluation comparing intraoperative cone beam CT-based navigation and conventional fluoroscopy for the placement of spinal pedicle screws: a patient-level data cost-effectiveness analysis. Spine J . 2016; 16( 1): 23- 31. Google Scholar CrossRef Search ADS PubMed  Supplemental digital content is available for this article at operativeneurosurgery-online.com. COMMENT The authors performed a retrospective single center study looking at the relationship between utilization of spinal navigation and operative time in a relatively simple case-mix of patients. The main bias of this study is that surgeons decided if they were using the navigation or not, which introduces a selection bias, and could have selected more challenging cases for the navigation cohort, and potentially longer cases as well. While the improved accuracy of pedicle screw placement with navigation is well-established, high acquisition costs and longer operative time seem to be the principal obstacles to a more widespread usage of this technology. This study adds to the literature by showing, like others have found, that surgical navigation does not impact significantly operative duration and that other factors, like individual surgeon performance and surgical indication, are the main drivers of surgical time. Nicolas Dea Sherbrooke, Canada Copyright © 2017 by the Congress of Neurological Surgeons

Journal

Operative NeurosurgeryOxford University Press

Published: Mar 1, 2018

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