Robotic-Assisted Minimally Invasive Transforaminal Lumbar Interbody Fusion

Robotic-assisted (RA) minimally invasive (MI) transforaminal lumbar interbody fusion (TLIF) is an advantageous combination of 2 techniques utilized to treat lumbar degenerative pathologies. Given the lack of direct visualization of anatomic landmarks in MI-TLIF, radiography is necessary for accurate pedicle screw placement^1-5. Navigation-guided systems have shown superiority over fluoroscopy by allowing for 3-D visualization and tracking^6-11. RA systems can potentially allow for greater accuracy via robotic-arm guidance adherent to planned trajectories¹². Although instrumentation complications are multifactorial, robotic guidance is another surgical tool to improve instrumentation accuracy and minimize invasiveness following MI-TLIF.

With the patient under general anesthesia and in a prone position, 2 reference arrays attached to the patient via bilateral posterior sacroiliac spine incisions are made in order to perform intraoperative computed tomography (CT) with an array-integrated CT scanner and to calibrate the robotic instruments. Surgical planning for the screws and interbody cage is performed on the interface of the robotic tool. With use of the robotic arm, percutaneous pedicle screws are placed bilaterally. A tubular retractor is then docked over the facet joint. A unilateral facetectomy is performed, followed by a complete discectomy with end plate preparation. Bone graft is placed into the disc space. An expandable interbody cage is filled with bone graft, tamped into place, and expanded. The disc space is then backfilled with more bone graft. Rods are inserted percutaneously. Placement of all instrumentation is confirmed fluoroscopically, and the wounds are closed in a multilayered approach.

Nonoperative alternatives to RA MI-TLIF include physical therapy, pharmacologic treatment, and lumbar and interlaminar transforaminal epidural corticosteroid injections. Surgical alternatives include RA open TLIF, MI-TLIF with fluoroscopy or navigation, posterior lumbar interbody fusion, lateral lumbar interbody fusion, and anterior lumbar interbody fusion¹³.

RA screw placement has been shown to be more accurate than fluoroscopy-guided placement, with a lower incidence of pedicle wall penetration or facet joint invasion, better insertion angle, and less blood loss^14-16. Compared with open TLIF, RA MI-TLIF provides improved screw placement, less blood loss, shorter length of stay, and better patient-reported outcome scores; however, it does increase operative time and radiation exposure^17,18. Furthermore, RA MI-TLIF has shown several advantages over fluoroscopy-assisted MI-TLIF, as it has similar 2-year fusion rates but is more accurate, has less complications, has less facet joint violation, yields greater adjacent disc height at 2 years, and exposes the surgeon to less radiation^19,20. Compared with navigation alone, RA navigation also allows for implantation of screws with a greater diameter and length without compromising accuracy, potentially allowing for more optimal osseous purchase²¹.

RA MI-TLIF offers several advantages compared with other types of MI-TLIF^17,22. A previous study showed 5.8 times greater and 11.0 times greater risks of complications and revision surgery, respectively, for fluoroscopy-assisted MI-TLIF (111 patients) compared with RA MI-TLIF (374 patients)²³. In another study comparing RA MI-TLIF and navigation-assisted TLIF, RA MI-TLIF had less intraoperative blood loss, shorter operative time (187.1 versus 152.3 minutes, respectively; p < 0.001), and a shorter hospital stay (92.3 versus 71.6 hours)²⁴.

Because of a smaller Kambin triangle, lateral lumbar interbody fusion is preferred for the upper lumbar levels. If MI-TLIF is chosen, RA is particularly valuable since screw trajectories can be planned to allow for removal of the superior portion of the caudal pedicle without compromising screw fixation.For successful fusion, utilize a large expandable interbody cage with autograft and allograft bone. The contralateral facet can be prepared as a fusion bed, as well. Avoid the use of bone morphogenetic protein, as this can result in neuroforaminal bone growth²⁵.Since all current robotic platforms are co-bot systems without independent robotic activity, the surgeon must employ the same skills and tactile feedback that would be utilized in placing instrumentation without guidance. Furthermore, the surgeon should know the visualized topographical anatomy and correct placement of every instrument in order to protect against unplanned placement.

RA = robotic-assistedMI = minimally invasiveTLIF = transforaminal lumbar interbody fusionPSIS = posterior superior iliac spinePLIF = posterior lumbar interbody fusionLLIF = lateral lumbar interbody fusionALIF = anterior lumbar interbody fusionDRB = dynamic reference baseBMP = bone morphogenetic proteinBMI = body mass indexCT = computed tomographyXR = X-rayMRI = magnetic resonance imagingOR = operating roomAP = anteroposteriorCSF = cerebrospinal fluidVAS = visual analog scaleEBL = estimated blood lossLOS = length of stayPT = physical therapyPRN = as needed.