OBJECTIVE The accuracy of percutaneous pedicle screw placement has increased with the advent of robotic and surgical navigation technologies. However, the effect of robotic intraoperative screw size and trajectory templating remains unclear. The purpose of this study was to compare pedicle screw sizes and accuracy of placement using robotic navigation (RN) versus skin-based intraoperative navigation (ION) alone in minimally invasive lumbar fusion procedures. METHODS A retrospective cohort study was conducted using a single-institution registry of spine procedures performed over a 4-year period. Patients who underwent 1- or 2-level primary or revision minimally invasive surgery (MIS)–transforaminal lumbar interbody fusion (TLIF) with pedicle screw placement, via either robotic assistance or surgical navigation alone, were included. Demographic, surgical, and radiographic data were collected. Pedicle screw type, quantity, length, diameter, and the presence of endplate breach or facet joint violation were assessed. Statistical analysis using the Student t-test and chi-square test was performed to evaluate the differences in pedicle screw sizes and the accuracy of placement between both groups. RESULTS Overall, 222 patients were included, of whom 92 underwent RN and 130 underwent ION MIS-TLIF. A total of 403 and 534 pedicle screws were placed with RN and ION, respectively. The mean screw diameters were 7.25 ± 0.81 mm and 6.72 ± 0.49 mm (p < 0.001) for the RN and ION groups, respectively. The mean screw length was 48.4 ± 4.48 mm in the RN group and 45.6 ± 3.46 mm in the ION group (p < 0.001). The rates of “ideal” pedicle screws in the RN and ION groups were comparable at 88.5% and 88.4% (p = 0.969), respectively. The overall screw placement was also similar. The RN cohort had 63.7% screws rated as good and 31.4% as acceptable, while 66.1% of ION-placed screws had good placement and 28.7% had acceptable placement (p = 0.661 and p = 0.595, respectively). There was a significant reduction in high-grade breaches in the RN group (0%, n = 0) compared with the ION group (1.2%, n = 17, p = 0.05). CONCLUSIONS The results of this study suggest that robotic assistance allows for placement of screws with greater screw diameter and length compared with surgical navigation alone, although with similarly high accuracy. These findings have implied that robotic platforms may allow for safe placement of the “optimal screw,” maximizing construct stability and, thus, the ability to obtain a successful fusion.

Study Design. Retrospective cohort. Objective. To compare robotics and navigation for minimally invasive elective lumbar fusion in terms of radiation exposure and time demand. Summary of Background Data. Although various studies have been conducted to demonstrate the benefits of both navigation and robotics over fluoroscopy in terms of radiation exposure, literature is lacking in studies comparing robotics versus navigation. Materials and Methods. Patients who underwent elective one-level or two-level minimally invasive transforaminal lumbar interbody fusion (TLIF) by a single surgeon using navigation (Stryker SpineMask) or robotics (ExcelsiusGPS) were included (navigation 2017–2019, robotics 2019–2021, resulting in prospective cohorts of consecutive patients for each modality). All surgeries had the intraoperative computed tomography workflow. The two cohorts were compared for radiation exposure [fluoroscopy time and radiation dose: image capture, surgical procedure, and overall) and time demand (time for setup and image capture, operative time, and total operating room (OR) time]. Results. A total of 244 patients (robotics 111, navigation 133) were included. The two cohorts were similar in terms of baseline demographics, primary/revision surgeries, and fusion levels. For one-level TLIF, total fluoroscopy time, total radiation dose, and % of radiation for surgical procedure were significantly less with robotics compared with navigation (20 vs. 25 s, P<0.001; 38 vs. 42 mGy, P=0.05; 58% vs. 65%, P=0.021). Although time for setup and image capture was significantly less with robotics (22 vs. 25 min, P<0.001) and operative time was significantly greater with robotics (103 vs. 93 min, P<0.001), there was no significant difference in the total OR time (145 vs. 141 min, P=0.25). Similar findings were seen for two-level TLIF as well. Conclusion. Robotics for minimally invasive TLIF, compared with navigation, leads to a significant reduction in radiation exposure both to the surgeon and patient, with no significant difference in the total OR time.

Study Design. Retrospective review of prospectively collected data. Objective. To analyze the postoperative factors that led delayed discharge in patients who would have been eligible for ambulatory lumbar fusion (ALF). Summary of Background Data. Assessing postoperative inefficiencies is vital to increase the feasibility of ALF. Materials and Methods. Patients who underwent single-level minimally invasive transforaminal lumbar interbody fusion and would have met the eligibility criteria for ALF were included. Length of stay (LOS); time in postanesthesia recovery unit (PACU); alertness and neurological examination, and pain scores at three and six hours; type of analgesia; time to physical therapy (PT) visit; reasons for PT nonclearance; time to per-oral (PO) intake; time to voiding; time to readiness for discharge were assessed. Time taken to meet each discharge criterion was calculated. Multiple regression analyses were performed to study the effect of variables on postoperative parameters influencing discharge. Results. Of 71 patients, 4% were discharged on the same day and 69% on postoperative day 1. PT clearance was the last-met discharge criterion in 93%. Sixty-six percent did not get PT evaluation on the day of surgery. Seventy-six percent required intravenous opioids and <60% had adequate pain control. Twenty-six percent had orthostatic intolerance. The median postoperative LOS was 26.9 hours, time in PACU was 4.2 hours, time to PO intake was 6.5 hours, time to first void was 6.3 hours, time to first PT visit was 17.7 hours, time to PT clearance was 21.8 hours, and time to discharge readiness was 21.9 hours. Regression analysis showed that time to PT clearance, time to PO intake, time to voiding, time in PACU, and pain score at three hours had a significant effect on LOS. Conclusions. Unavailability of PT, surgery after 1 pm, orthostatic intolerance, inadequate pain control, prolonged PACU stay, and long feeding and voiding times were identified as modifiable factors preventing same-day discharge. Level of Evidence. 4.

Study Design. Retrospective review of prospectively collected data. Objective. To determine the Oswestry Disability Index (ODI) cutoff for achieving Patient Acceptable Symptom State (PASS) at one year following minimally invasive lumbar spine surgery. Summary of Background Data. An absolute score denoting PASS, rather than a change score denoting minimal clinically important difference (MCID), might be a better metric to assess clinical outcomes. Materials and Methods. Patients who underwent primary minimally invasive transforaminal lumbar interbody fusion or decompression were included. The outcome measure was ODI. The anchor question was the Global Rating Change. "Compared with preoperative, you feel (1) much better, (2) slightly better, (3) same, (4) slightly worse, or (5) much worse." For analysis, it was collapsed to a dichotomous outcome variable (acceptable = response of 1 or 2, unacceptable = response of 3, 4, or 5). Proportion of patients achieving PASS and the ODI cutoff using receiver operating characteristic curve analyses were assessed for the overall cohort as well as subgroups based on age, sex, type of surgery, and preoperative ODI. Differences between the PASS and MCID metrics were analyzed. Results. A total of 137 patients were included. In all, 87% of patients achieved PASS. Patients less than or equal to 65 years and those undergoing fusion were more likely to achieve PASS. The receiver operating characteristic curve analysis revealed an ODI cutoff of 25.2 to achieve PASS (area under the curve. 0.872, sensitivity: 82%, specificity: 83%). The subgroup analyses based on age, sex, and preoperative ODI revealed area under the curve > 0.8 and ODI threshold values consistent between 25.2 and 25.5 (except 28.4 in patients with preoperative ODI > 40). PASS was found to have significantly higher sensitivity compared with MCID (82% vs. 69%, P = 0.01). Conclusions. Patients with ODI <25 are expected to achieve PASS, irrespective of age, sex, and preoperative disability. PASS was found to have significantly higher sensitivity than MCID.

OBJECTIVE The objective of this study was to assess the outcomes of minimally invasive lumbar decompression in patients ≥ 80 years of age and compare them with those of younger age groups. METHODS This was a retrospective cohort study. Patients who underwent primary unilateral laminotomy for bilateral decompression (ULBD) (any number of levels) and had a minimum of 1 year of follow-up were included and divided into three groups by age: < 60 years, 60–79 years, and ≥ 80 years. The outcome measures were 1) patient-reported outcome measures (PROMs) (visual analog scale [VAS] back and leg, Oswestry Disability Index [ODI], 12-Item Short-Form Health Survey [SF-12] Physical Component Summary [PCS] and Mental Component Summary [MCS] scores, and Patient-Reported Outcomes Measurement Information System Physical Function [PROMIS PF]); 2) percentage of patients achieving the minimal clinically important difference (MCID) and the time taken to do so; and 3) complications and reoperations. Two postoperative time points were defined: early (< 6 months) and late (≥ 6 months). RESULTS A total of 345 patients (< 60 years: n = 94; 60–79 years: n = 208; ≥ 80 years: n = 43) were included in this study. The groups had significantly different average BMIs (least in patients aged ≥ 80 years), age-adjusted Charlson Comorbidity Indices (greatest in the ≥ 80-year age group), and operative times (greatest in 60- to 79-year age group). There was no difference in sex, number of operated levels, and estimated blood loss between groups. Compared with the preoperative values, the < 60-year and 60- to 79-year age groups showed a significant improvement in most PROMs at both the early and late time points. In contrast, the ≥ 80-year age group only showed significant improvement in PROMs at the late time point. Although there were significant differences between the groups in the magnitude of improvement (least improvement in ≥ 80-year age group) at the early time point in VAS back and leg, ODI, and SF-12 MCS, no significant difference was seen at the late time point except in ODI (least improvement in ≥ 80-year group). The overall MCID achievement rate decreased, moving from the < 60-year age group toward the ≥ 80-year age group at both the early (64% vs 51% vs 41% ) and late (72% vs 58% vs 52%) time points. The average time needed to achieve the MCID in pain and disability increased, moving from the < 60-year age group toward the ≥ 80-year age group (2 vs 3 vs 4 months). There was no significant difference seen between the groups in terms of complications and reoperations except in immediate postoperative complications (5.3% vs 4.8% vs 14%). CONCLUSIONS Although in this study minimally invasive decompression led to less and slower improvement in patients ≥ 80 years of age compared with their younger counterparts, there was significant improvement compared with the preoperative baseline.

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Study Design/Setting. Systematic review. Objective. The primary purpose was to propose patient selection criteria and perioperative best practices that can serve as a starting point for an ambulatory lumbar fusion program. The secondary purpose was to review patient-reported outcomes (PROs) after ambulatory lumbar fusion. Summary of Background. As healthcare costs rise, there is an increasing emphasis on cost saving strategies (i.e. outpatient/ambulatory surgeries). Lumbar fusion procedures remain a largely inpatient surgery. Early studies have shown that fusion procedures can be safely preformed in an outpatient setting but no review has summarized these findings and best practices. Materials and Methods. This study was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed/MEDLINE, The Cochrane Library, and Embase were searched. The following data were collected: (1) study design; (2) number of participants; (3) patient population; (4) procedure types; (5) procedure setting; (6) inclusion criteria; (7) protocols; (8) adverse events; (9) PROs; and (10) associations between patient/surgical factors, setting, and outcomes. Results. The search yielded 20 publications. The following selection criteria for ambulatory lumbar fusion were identified: age below 70, minimal comorbidities, low/normal body mass index, no tobacco use, and no opioid use. The perioperative protocol can include a multimodal analgesic regimen. The patient should be observed for at least three hours after surgery. The patient should not be discharged without an alertness check and a neurological examination. Patients experienced significant improvements in PROs after ambulatory lumbar fusion; similarly, when compared to an inpatient group, ambulatory lumbar fusion patients experienced a comparable or superior improvement in PROs. Conclusion. There are two critical issues surrounding ambulatory lumbar fusion: (1) Who is the ideal patient, and (2) What needs to be done to enable expedited discharge? We believe this review will provide a foundation to assist surgeons in making decisions regarding the performance of lumbar fusion on an ambulatory basis. Level of Evidence. Level III.

Robotics in spinal surgery offers a promising potential to refine and improve the minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) technique. Suitable surgeons for this technique include those who are already familiar with robotic-guided lumbar pedicle screw placement and want to advance their skillset by incorporating posterior-based interbody fusion. We provide a step-by-step guide for robotic-guided MI-TLIF. The procedure is divided into 7 practical and detailed techniques. The steps in sequential order include: (I) planning trajectories for pedicle screws and the tubular retractor; (II) robotic-guided pedicle screw placement; (III) placement of tubular retractor; (IV) unilateral facetectomy using the surgical microscope; (V) discectomy & disc preparation; (VI) interbody implant insertion; and(VII) percutaneous rod placement. We standardize surgeon training in robotic MI-TLIF by teaching our spine surgery fellows these 7 key technical steps highlighted in this guide. Current-generation robotics offers integrated navigation capability, K-wireless placement of pedicle screws through a rigid robotic arm, compatibility with tubular retractor systems to perform facetectomy, and allows for placement of interbody devices. We have found robotic-guided MI-TLIF to be a safe procedure that allows for accurate and reliable pedicle screw placement, less collateral damage to the soft tissues of the low back, and decreased radiation exposure.