Robotic guidance provides indirect visualization of key anatomic landmarks to facilitate minimally invasive surgery (MIS) and is emerging as a reliable and accurate technique for posterior spine instrumentation. We sought to describe eight years of experience with robotic guidance at a high-volume, multi-surgeon center. We hypothesize that robotic guidance will lead to (1) low rates of complication, readmissions, and revision surgery, (2) reduced fluoroscopic radiation exposure, (3) and accurate thoracolumbar instrumentation.
A retrospective review of complications, revision surgery, and readmission rates in patients undergoing thoracolumbar fusion surgery utilizing three robotic generations. Secondary analysis was conducted comparing the three robotic generations for complications, revision surgery, accuracy, and readmission rates along with intraoperative fluoroscopic duration.
A total of 628 patients (3,874 robotic-guided screws) ages 12–81 years-old (43.9% male) were included in the study. At one year, the cumulative complication incidence was 15.5% with a 10.3% incidence of surgical complications (3.7% wound, 1.2% robot-related, and 5.4% non-robot-related complications). At one year, the revision surgery incidence was 9.4%. There was no statistical difference between complications, readmission, or revision surgery after initial admission among the three robotic generations. The average intraoperative fluoroscopic duration was 53.8 seconds (11.9 seconds per screw and 17.6 seconds per instrumented level).
Robotic guidance in thoracolumbar instrumented fusions was associated with low complication, revision surgery, and readmission rates. Our results suggest robotic guidance can provide accurate guidance with minimal adverse events in thoracolumbar instrumentation.
Since the introduction of the first surgical robotic system over twenty years ago, robotic-guided surgery has become an integral tool in multiple surgical fields [
The currently available guidance systems in spine surgery can be classified into three general categories: standard navigation-based systems with optical tracking reference markers (NAV), robotic arms combined with a NAV system (RNAV), and anatomy recognition-based robotic systems. RNAV systems utilize optical reference markers attached to the patient and a floor-mounted robotic arm registered with intraoperative 3-dimensional (3D) imaging; anatomy recognition-based robotic systems utilize bed- or patient-mounted systems fixed to bony landmarks and preoperative planning from 3D imaging. Mazor CoreTM technology (MCT) (Medtronic, Minneapolis, MN, USA) utilizes automated anatomy recognition software that registers individual vertebrae on two-view intraoperative fluoroscopic imaging with preoperative 3D images and determines the patient’s intraoperative location relative to the robotic system.
The current literature suggests that robotic guidance systems can be used to perform reliable and accurate thoracolumbar pedicle instrumentation [
This study was approved by the Institutional Review Board of Advarra (IRB No. Pro00034175).
We conducted a retrospective review of robotic-guided thoracolumbar spine surgeries at a multi-surgeon, single center between July 2012 and March 2020. The experience included three robotic generations using MCT evolving over time. Renaissance® (R), Mazor X® (X), and Mazor X Stealth Edition® (MXSE) systems were utilized for robotic guidance (Medtronic, Minneapolis, MN, USA) as shown in
All consecutive adolescent and adult patients undergoing robotic-guided thoracolumbar fusions for deformity or degenerative spine conditions were included in the study. These included both primary and revision surgeries, as well as MIS and open approaches. All patients or their legal guardians signed written informed consent within the institute’s Notice of Privacy Practices prior to surgery. IRB approval was granted by Advarra, a centralized IRB (Pro00034175).
Data including short- and long-term complications, revision surgery, and intraoperative fluoroscopic exposure were retrospectively collected from medical records and operative reports. Complications were subdivided into the following time periods: intraoperative, initial hospitalization, and postoperative at 30-days, 90-days, and 1-year. Intraoperative records were reviewed for the following: dural tear, estimated blood loss (EBL), neurologic deficit, other complications, and misplaced screws. For the purposes of this study, ‘misplaced’ was defined as any screw that required intraoperative revision of trajectory or removal as a result of pedicle screw stimulation less than 10 mA or if a breach was identified on intraoperative 3D imaging when available. Intraoperative fluoroscopic exposure was measured by intraoperative fluoroscopic duration in seconds and reported as total radiation duration, time per instrumented level, and time per robotic-executed screw. Postoperative complications were divided into surgical and medical complications. Surgical complications were subdivided into wound (including infection), robot-related (including misplaced screws and implant-related durotomy), and non-robot-related complications. Revision surgeries were reviewed at the initial admission, 30-days, 90-days, and 1-year. Medical complications occurring after 90 days postoperatively were deemed unlikely related to the robotic-guided portion of surgery and were not included.
Patient demographics, Charlson comorbidity index (CCI), body mass index (BMI), nicotine status, and primary preoperative diagnosis were collected from medical records and operative reports. Perioperative variables including EBL, number of screws, types of screws, procedure time, number of instrumented levels, length of hospital stay (LOS), and readmissions were also recorded. Postoperative computed tomography (CT) scans were available for 184 cases (a total of 1,255 screws). An independent, board-certified neuroradiologist reviewed and graded these screws for accuracy using the Gertzbein-Robbins (GR) classification [
Descriptive statistics and cohort comparison analysis were performed using IBM SPSS Statistics for Windows, Version 26.0 (IBM Corp., Armonk, NY, USA). Fisher’s exact test and chi-squared test were used to compare variables across robotic cohorts. A p-value threshold of 0.05 was used to determine statistical significance.
This study included a total of 3,874 robotic-guided screws in 628 patients ages 12–81 years-old (mean 51.8±13.7 years) who were 43.9% male. Patients had an average BMI of 29.8 kg/m2, CCI score of 1.2, and 7.8% were nicotine users (
A total of 9 patients (1.4%) experienced an intraoperative complication, including 8 durotomies unrelated to instrumentation and 1 episode of bradycardia. Of the 3,874 screws placed with robotic guidance, 46 (1.2%) were considered misplaced resulting in an initial robotic-guided screw placement accuracy of 98.7% (
A total of 33 patients (5.3%) experienced a complication following surgery, during the initial admission (
Twelve patients (1.9%) required a revision surgery during the initial admission including: the 6 symptomatic malpositioned screws, 2 retroperitoneal hematomas requiring evacuation, 3 patients with radiculopathy unrelated to the instrumentation requiring posterior decompression, and 1 anterior migration of interbody implant after posterior instrumentation, requiring revision (
At 30-days the cumulative number of patients who experienced a complication was 68 (10.8%). Cumulative surgical complications at 30 days included 14 wound (2.2%), 7 robot-related (1.1%), and 18 non-robot-related complications (2.9%). These included the following new wound complications since admission: 7 wound infections, 2 seromas, 2 retroperitoneal hematomas, and 1 epidural hematoma. One patient underwent a postoperative CT scan due to non-robot-related distal construct fracture and a screw breach was noted proximally within the construct incidentally, which was asymptomatic. This was counted as the 1 new robot-related complication because the misplaced screw was removed during the revision surgery to extend the construct distally (
The 30-day cumulative revision surgery rate was 4.8% including: 12 wound-related incision and drainage (I&D), 1 incision and drainage for arterial line site infection, 4 decompressions, 1 revision PIF, and 1 PIF extended proximally for junctional failure. The 30-day cumulative readmission rate was 3.8%, including six medical readmissions and eighteen for revision surgery (
The 90-day cumulative complication incidence was 13.5% (
Eighteen patients underwent revision surgery between the 30- and 90-day marks, resulting in a 7.5% cumulative revision surgery rate. The 90-day revision surgeries included: 11 wound-related I&Ds, 5 additional decompressions, 1 ALIF revision, and 1 PIF extended distally for distal junctional failure. The cumulative readmission rate at 90 days was 6.5%. Twenty new readmissions occurred between the 30- and 90-day period, 18 for revision surgery and 2 for medical complications (
A total of 406 patients reached a 1-year follow-up. The cumulative complication incidence for these patients was 15.5%. Surgical complications were 3.7% wound, 1.2% robot-related, and 5.4% non-robot-related cumulative complications. Between 90 days and 1 year follow-up, 10 new complications occurred that were not robot-related. These included one wound infection, five patients with radiculopathy, and four patients with proximal junctional kyphosis. All ten patients underwent revision surgery resulting in a cumulative revision surgery incidence of 9.4% (
Over time, patients undergoing robotic-guided surgery were older with a higher CCI score, a greater number of instrumented levels, and more likely to require an open procedure versus MIS (
The average total fluoroscopic duration was 53.8 seconds. The average fluoroscopic duration per screw was 11.9 seconds per screw and 17.6 seconds per instrumented level. The mean fluoroscopic duration in the MXSE cohort was 41.0 seconds, the lowest across the three generations (vs. X: 55.3 seconds and R: 61.6 seconds, p<0.001). Over time, the evolving robotic guidance systems led to less intraoperative radiation. A statistically significant decrease in intraoperative radiation was found in the MXSE cohort compared to the X and R cohorts (
Of the 3,874 screws, 1,255 screws had postoperative computed tomography (CT) scans available for independent review. Of the graded screws, 1,153 screws (91.9%) were classified as Gertzbein-Robbins (GR) grade A or B. There was no statistically significant difference in GR grading between the three robotic cohorts (
Innovation in robotic guidance has been driven by a desire to improve patient safety and surgical efficacy. The current generations of robotic systems combine precise anatomic landmark identification with specialized surgical planning software to achieve this goal. The literature supports improved accuracy and reliability with robotic-guided systems in spine surgery with accuracy rates as high as 99% [
Our results found low cumulative complication (15.5%), revision surgery (9.4%), and 90-day readmission rates (6.5%) across all three generations of robotic systems at 1 year follow up. These results are consistent with or better than the limited literature on instrumentation-related complications and revision surgery. In our study of 628 consecutive cases and 3,874 robotic-guided screws, seven patients required revision surgery for robot-related complications, an overall rate of 1.1%. Six of the seven required revision surgery during their initial admission for implant-related radiculopathy. Siccoli et al.’s [
Two recent studies evaluated perioperative outcomes between robotic guidance (RG) and fluoro-guidance (FG) in adult lumbar fusions in the prospectively collected, multicenter MIS ReFRESH database [
Lieber et al. [
Staartjes et al. [
This study found an average total fluoroscopic duration of 53.8 seconds (11.9 seconds per screw, 17.6 seconds per instrumented level). The current literature suggests that robotic guidance reduces intraoperative fluoroscopic duration and radiation exposure compared to conventional freehand technique [
In a randomized control trial comparing MIS robotic-guided and fluoroscopy-guided lumbar fusions, Hyun et al. [
In the current study, 91.9% of the 1,255 robotic screws with postoperative CT scans were GR Grade A or B. In the R cohort, 92.2% of screws were GR Grade A or B (vs. 92.0% and 90.8%, in the X and MSE cohorts respectively). No statistically significant difference was seen in GR Grade between the three robotic cohorts (p=0.976). The accuracy rate found in the current study is consistent with rates reported in the current literature, ranging from 90% to 100% [
The retrospective observational study design results in several inherent limitations. In this multi-surgeon, single-center study, differences among surgical techniques and robotic experience between surgeons may introduce unrecognized confounding. Without a control group, the current study cannot reach conclusions comparing robotic-guided instrumentation with other techniques. The goal of this study is to present a high-volume, multi-surgeon spine institute’s experience with complication, revision surgery, and readmission rates in robotic-guided thoracolumbar instrumentation.
This study supports that robotic-guided thoracolumbar instrumented fusions are associated with low rates of complication, revision surgery, and readmission; high levels of screw placement accuracy; and a reduction of intraoperative radiation exposure.
IRB approval was granted by Advarra, a centralized IRB (Pro00034175).
No potential conflict of interest relevant to this article.
Statistical analytic support by Dr. Leah Y. Carreon, MD, Clinical Research Director, Norton Leatherman Spine, Louisville, KY, USA.
Images demonstrating the (A) Renaissance robotic system, (B) Mazor X robotic system, and (C) Mazor X Stealth Edition robotic system which includes the addition of the navigation camera and software upgrade.
Cohort comparison (patient demographics)
Total (N=628) | R (N=210) | X (N=258) | MXSE (N=160) | p-value | |
---|---|---|---|---|---|
Age (yr) | 51.8±13.7 | 50.0±14.6 | 51.9±13.5 | 53.9±12.6 | 0.021 |
BMI (kg/m2) | 29.8±6.1 | 29.1±6.2 | 30.4±6.0 | 29.9±5.9 | 0.092 |
CCI | 1.2±1.2 | 1.1±1.2 | 1.1±1.2 | 1.4±1.3 | 0.032 |
Preoperative VAS (1–10 scale) | 6.0±2.3 | 6.3±2.2 | 5.9±2.4 | 5.9±2.1 | 0.093 |
Sex, male | 276 (43.9) | 93 (44.3) | 108 (41.9) | 75 (46.9) | 0.600 |
Nicotine user | 49 (7.8) | 13 (6.2) | 26 (10.1) | 10 (6.3) | 0.207 |
1 yr VAS | 3.5±2.7 | 3.6±2.6 | 3.4±2.8 | 4.0±2.5 | 0.255 |
VAS change (over 1 yr) | 2.4±3.0 | 2.7±3.1 | 2.4±3.0 | 1.8±2.6 | 0.185 |
Total F/U duration (mo) | 18.0±16.7 | 30.2±22.4 | 14.4±8.0 | 8.0±4.0 | <0.001 |
Values represent the number of patients (%) or mean±standard deviation
BMI: body mass index, CCI: Charlson comorbidity index, VAS: visual analog scale, F/U: follow-up.
Significant p-values.
Cohort comparison (surgical variables)
Total (N=628) | R (N=210) | X (N=258) | MXSE (N=160) | p-value | |
---|---|---|---|---|---|
Open | 177 (28.2) | 48 (22.9) | 71 (27.5) | 58 (36.3) | 0.017 |
Diagnosis | |||||
Spondylolisthesis | 290 (46.2) | 120 (57.1) | 116 (45.0) | 54 (33.8) | 0.001 |
DDD | 121 (19.3) | 40 (19.0) | 51 (19.8) | 30 (18.8) | |
Deformity | 115 (18.3) | 28 (13.3) | 46 (17.8) | 41 (25.6) | |
Stenosis | 66 (10.5) | 15 (7.1) | 28 (10.9) | 23 (14.4) | |
Other | 36 (5.7) | 7 (3.3) | 17 (6.6) | 12 (7.5) | |
Approach | |||||
Posterior only | 52 (8.3) | 18 (8.6) | 16 (6.2) | 18 (11.3) | 0.219 |
AP staged | 557 (88.7) | 183 (87.1) | 236 (91.5) | 138 (86.3) | |
AP same day | 18 (2.9) | 9 (4.3) | 6 (2.3) | 3 (1.9) | |
Revision surgery | 72 (11.5) | 26 (12.4) | 27 (10.5) | 19 (11.9) | 0.797 |
No. instrumented levels | 3.9±3.0 | 3.2±2.2 | 4.0±3.0 | 4.6±3.6 | <0.001 |
Mean screws/case | 6.8±5.8 | 5.3±4.5 | 7.2±6.2 | 8.1±6.4 | <0.001 |
Mean robot screws/case | 6.2±2.3 | 4.9±4.0 | 6.5±5.5 | 7.3±5.9 | <0.001 |
Mean free-hand screws/case | 0.5±2.2 | 0.5±1.7 | 0.3±1.8 | 0.7±3.1 | 0.211 |
Total procedure time (min) | 177.7±122.4 | 158.9±106.5 | 179.7±123.7 | 199.2±135.7 | 0.007 |
Net robot time (min) | 35.5±30.4 | 33.9±23.5 | 32.2±30.4 | 62.3±49.3 | <0.001 |
Total fluoro (sec) | 53.8±51.2 | 61.6±70.2 | 55.3±39.9 | 41.0±32.3 | <0.001 |
Total fluoro/screw (sec) | 11.9±9.8 | 15.6±11.4 | 11.9±8.7 | 7.4±6.8 | <0.001 |
Total fluoro per level (sec) | 17.6±13.5 | 22.4±15.5 | 17.4±11.7 | 11.9±10.8 | <0.001 |
EBL (mL) | 173.8±326.8 | 117.5±207.0 | 196.5±357.5 | 207.7±384.9 | 0.012 |
Values represent the number of patients (%) or mean±standard deviation
R: Renaissance, X: Mazor X, MSXE: Mazor X Stealth Edition, AP: anterior-posterior, No.: number, EBL: estimated blood loss.
Significant p-values.
Complication, revision surgery, and readmission comparison
Total (N=628) | R (N=210) | X (N=258) | MXSE (N=160) | p-value | ||
---|---|---|---|---|---|---|
Index admission | Intraoperative complications | 9 (1.4) | 3 (1.4) | 2 (0.8) | 4 (2.5) | 0.353 |
Total complications | 33 (5.3) | 10 (4.8) | 16 (6.2) | 7 (4.4) | 0.664 | |
Medical complications | 13 (2.1) | 4 (1.9) | 5 (1.9) | 4 (2.5) | 0.906 | |
Surgical complications | 21 (3.3) | 6 (2.9) | 12 (4.7) | 3 (1.9) | 0.274 | |
Wound complications | 2 (0.3) | 1 (0.5) | 1 (0.4) | 0 (0.0) | 0.700 | |
Robot-related | 6 (1.0) | 1 (0.5) | 5 (1.9) | 0 (0.0) | 0.096 | |
Non-robot related | 13 (2.0) | 4 (1.9) | 6 (2.3) | 3 (1.9) | 0.712 | |
Revision surgery | 12 (1.9) | 3 (1.4) | 9 (3.5) | 0 (0.0) | 0.033 |
|
30 days | Total complications | 68 (10.8) | 22 (10.5) | 27 (10.5) | 19 (11.9) | 0.887 |
Medical complications | 32 (5.1) | 10 (4.8) | 13 (5.0) | 9 (5.6) | 0.966 | |
Surgical complications | 38 (6.1) | 13 (6.2) | 15 (5.8) | 10 (6.3) | 0.980 | |
Wound complications | 14 (2.2) | 7 (3.3) | 3 (1.2) | 4 (2.5) | 0.407 | |
Robot-related | 7 (1.1) | 1 (0.5) | 5 (1.9) | 1 (0.6) | 0.384 | |
Non-robot related | 18 (2.9) | 6 (2.9) | 7 (2.7) | 5 (3.1) | 0.828 | |
Revision surgery | 30 (4.8) | 11 (5.2) | 12 (4.7) | 7 (4.4) | 0.809 | |
Readmission | 24 (3.82) | 11 (5.2) | 6 (2.3) | 7 (4.4) | 0.372 | |
90 days | Total complications | 85 (13.5) | 26 (12.4) | 35 (13.6) | 24 (15.0) | 0.767 |
Medical complications | 36 (5.7) | 10 (4.8) | 14 (5.4) | 12 (7.5) | 0.604 | |
Surgical complications | 55 (8.8) | 17 (8.1) | 23 (8.9) | 15 (9.4) | 0.905 | |
Wound complications | 25 (4.0) | 10 (4.8) | 10 (3.9) | 5 (3.1) | 0.474 | |
Robot-related | 7 (1.1) | 1 (0.5) | 5 (1.9) | 1 (0.6) | 0.229 | |
Non-robot related | 24 (3.8) | 7 (3.3) | 8 (3.1) | 9 (5.6) | 0.383 | |
Revision surgery | 47 (7.5) | 15 (7.1) | 20 (7.8) | 12 (7.5) | 0.970 | |
Readmission | 41 (6.5) | 15 (7.1) | 14 (5.4) | 12 (7.5) | 0.641 |
Data collected cumulatively. Values represent the number of patients (%).
R: Renaissance, X: Mazor X, MSXE: Mazor X Stealth Edition.
Significant p-values.
One year complication, revision surgery, and readmission comparison
Total (N=406) | R (N=164) | X (N=183) | MXSE (N=59) | p-value | ||
---|---|---|---|---|---|---|
1 yr | Total complications | 63 (15.5) | 24 (14.6) | 27 (14.8) | 12 (20.3) | 0.541 |
Surgical complications | 42 (10.3) | 15 (9.2) | 18 (9.8) | 8 (13.6) | 0.619 | |
Wound complications | 15 (3.7) | 7 (4.3) | 7 (3.8) | 1 (1.7) | 0.662 | |
Robot-related | 5 (1.2) | 1 (0.6) | 4 (2.2) | 0 (0.0) | 0.269 | |
Non-robot related | 22 (5.4) | 7 (4.3) | 8 (4.4) | 7 (11.9) | 0.061 | |
Revision surgery | 38 (9.4) | 13 (7.9) | 18 (9.8) | 7 (11.9) | 0.148 |
Accuracy comparison using Gertzbein and Robbins (GR) grade
All (N=1,255) | R (N=459) | X (N=589) | MXSE (N=207) | p-value | |
---|---|---|---|---|---|
Grade A | 73.6% (924) | 74.5% (342) | 73.3% (432) | 72.5% (150) | 0.976 |
Grade B | 18.2% (229) | 17.6% (81) | 18.7% (110) | 18.4% (38) | |
Grade C | 4.6% (58) | 5.0% (23) | 4.1% (24) | 5.3% (11) | |
Grade D | 2.2% (28) | 2.0% (9) | 2.4% (14) | 2.4% (5) | |
Grade E | 1.3% (16) | 0.9% (4) | 1.5% (9) | 1.4% (3) |