Background: Percutaneous transforaminal endoscopic discectomy (PTED) is a minimally invasive technique for the treatment of symptomatic lumbar disc herniation (LDH) that is growing in popularity. The procedure involves the insertion of a transforaminal spinal endoscope for direct access and removal of intra and extra-foraminal disc fragments ¹ . Description: The patient is preferably placed in a prone position. A spinal needle is advanced under fluoroscopic guidance into the foramen to the medial border of the inferior pedicle. A guidewire is introduced through the needle cannula, and sequential dilators are advanced into the foramen. A partial facetectomy/foraminotomy is performed so that a 10-mm working cannula and spinal endoscope can be introduced. Endoscopic pituitary rongeurs are utilized to remove the extruded disc material. Once the extruded fragments are no longer visualized, a probe is utilized to verify that no remaining disc material is present, and a diagnostic endoscopy is performed. The cannula is removed, and the incision is closed in a standard fashion. Alternatives: Nonoperative alternatives to PTED include activity modification, nonsteroidal anti-inflammatory drugs and/or acetaminophen, physical therapy, and epidural steroid injections ² . When surgical intervention is indicated, alternative techniques for decompression include conventional microdiscectomy, tubular microdiscectomy, and unilateral biportal endoscopic discectomy ³ , as well as lumbar fusion techniques. Rationale: PTED shares similar indications as open and tubular discectomy, including soft LDH confirmed on imaging, persistent radiculopathy, new sensory/motor neurologic deficits, and failed nonoperative treatment of >6 weeks ¹ . Compared with open and tubular discectomy, PTED offers several advantages, including a smaller skin incision, feasibility under local anesthesia, direct visualization, avoidance of muscle retraction, minimal bone removal and neural manipulation, preservation of spine stability and adjacent anatomy, decreased intraoperative blood loss, and shorter operative times ^4–11 . In patients with a far lateral or foraminal LDH, PTED may avoid the need for fusion ¹² . Considerations for PTED include the narrow working corridor, representing a risk of iatrogenic injury or incomplete decompression, and the associated learning curve ^13,14 . Relative contraindications include recurrent LDH, paracentral LDH, extruded LDH, sequestration of the disc, significant obesity, isthmic spondylolisthesis, and severe canal stenosis ¹¹ . Additionally, accessing the lower lumbar levels via a transforaminal approach may be difficult in patients with a high iliac crest. Expected Outcomes: PTED is a safe procedure that has been shown to improve patient-reported outcomes and functional status. In a recent meta-analysis, Gadjradj et al. reported a pooled complication rate of 4.6% (range, 0% to 8.6%) for PTED ⁸ . Hoogland et al. reported 85% excellent/good satisfaction in patients who underwent PTED, compared with 8% poor satisfaction, as well as improvements in visual analogue scale back and leg pain scores of 6.0 and 5.6, respectively, at 2-year follow-up. Chen et al. found that PTED resulted in similar patient-reported outcomes with similar rates of complications, recurrence, and reoperation and shorter in-bed times and lengths of stay compared with open discectomy ⁵ . Important Tips: The exiting nerve root is at risk during the approach. The foramen is entered at the furthest point from the nerve root by targeting the superior-most portion of the inferior pedicle (anteroposterior view) and the posterior-inferior corner of the disc (lateral view). For procedures performed with the patient under awake anesthesia, the patient should be monitored for nerve-root injury by asking them to report pain and move their feet. When a patient is fully anesthetized, neuromonitoring should be utilized. Neuromonitoring is especially important to remove fragments in difficult-to-access locations. Because of the narrow corridor, it may be difficult to confirm full decompression. Thoroughly reviewing the patient imaging to understand the fragment location is necessary. Postoperatively, it is important to evaluate patients to identify cases of incomplete decompression. The dorsal root ganglion is sensitive to irritation. Prior to closure, we irrigate the working cannula with a steroidal solution. The learning curve for PTED has been shown to be 31 cases, which is longer than traditional microdiscectomy techniques ¹⁴ . Acronyms and Abbreviations: PTED = percutaneous transforaminal endoscopic discectomy LDH = lumbar disc herniation AP = anteroposterior PSH = past surgical history MRI = magnetic resonance imaging OR = operating room PACU = post-anesthesia care unit

Background/Objectives: Sagittal spinal alignment goals for adult spinal deformity (ASD) surgery are predominantly derived from standing radiographs, despite the biomechanical relevance of sitting posture. Existing studies on sitting alignment involve young, healthy cohorts, which poorly represent ASD patients. This study assessed posture-dependent changes in spinopelvic parameters, including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and lumbar lordosis (LL), and examined how age, BMI, and gender influence these changes. Methods: In this retrospective cohort study, sitting and standing lateral radiographs of 1447 patients were evaluated. Spinopelvic parameters were measured, and changes (ΔPI, ΔPT, ΔSS, and ΔLL) were calculated. Multiple regression analysis was used to determine associations between these changes and age, BMI, and gender. Results: All parameters differed significantly between positions (p < 0.001); PT and PI increased in sitting (ΔPT = −19.20°; ΔPI = −4.52°), while SS and LL increased in standing (ΔSS = 14.67°; ΔLL = 18.44°). Older age correlated with increased ΔPT (p < 0.001) and ΔPI (p = 0.049) but reduced ΔLL and ΔSS (p < 0.001). Higher BMI was associated with decreased ΔPI, ΔPT, and ΔLL (p < 0.001, 0.003, and 0.025). Females showed greater ΔPT (p = 0.013) but smaller ΔPI, ΔSS, and ΔLL (p = 0.043, <0.001, and 0.001). Conclusions: Spinopelvic parameters vary significantly between sitting and standing positions, affected by age, BMI, and gender. The observed PI change suggests SIJ involvement, highlighting the need for posture-specific and demographic-adjusted alignment goals in ASD surgery to optimize outcomes.

Background: Postoperative urinary retention (POUR), a common complication after spine surgery, can contribute to longer hospital stays, urinary tract infection, pain, and morbidity. This study aimed to determine the incidence of POUR in patients who underwent lumbar decompression and to construct a predictive model for preoperatively identifying high-risk patients. Methods: This was a retrospective review of patients undergoing primary lumbar decompression from 2017 to 2023. Demographic characteristics, comorbidities, and perioperative data were collected. Factors associated with POUR were assessed, and multivariable logistic regressions were performed to identify independent predictors of the development of POUR. A nomogram to predict the development of POUR was developed within a training subset, based on a multivariable logistic regression model of preoperative variables, followed by the internal validation of the model in a validation subset and assessment of its performance. Results: Of the 1,938 patients included in this study, 133 (6.9%) developed POUR. Following multivariable analysis, the following risk factors for POUR were identified: a history of urinary retention (odds ratio [OR], 4.956 [95% confidence interval (CI), 2.157 to 11.383]; p < 0.001), insurance that was not commercial (private) (OR, 2.256 [95% CI, 1.298 to 3.922]; p = 0.004), intraoperative Foley catheter use (OR, 5.967 [95% CI, 3.506 to 10.156]; p < 0.001), inpatient opioid consumption of >93 morphine milligram equivalents (OR, 1.898 [95% CI, 1.220 to 2.952]; p = 0.004), and anticholinergic medication use during hospitalization (OR, 3.450 [95% CI, 2.313 to 5.148]; p < 0.001). The nomogram, which included the preoperative variables of male sex, age of >65 years, history of urinary retention, history of benign prostatic hyperplasia, not having commercial insurance, and American Society of Anesthesiologists (ASA) classification of >2, demonstrated good discrimination in the training subset (area under the curve [AUC], 0.725 [95% CI, 0.673 to 0.776]) and the validation subset (AUC, 0.709 [95% CI, 0.599 to 0.819]). The Hosmer-Lemeshow goodness-of-fit test demonstrated that the model fit the data well (chi-square test = 9.063; p = 0.170). Conclusions: The incidence of POUR after lumbar decompression surgery was found to be 6.9%. A history of urinary retention, not having commercial (private) insurance, intraoperative Foley catheter usage, inpatient opioid consumption of >93 morphine milligram equivalents, and the administration of anticholinergic medication during hospitalization increased the risk of developing POUR. Furthermore, we constructed a preoperative predictive model with good performance metrics to help clinicians to identify patients at elevated risk for developing POUR. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: 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 trajectories ¹² . Although instrumentation complications are multifactorial, robotic guidance is another surgical tool to improve instrumentation accuracy and minimize invasiveness following MI-TLIF. Description: 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. Alternatives: 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 fusion ¹³ . Rationale: 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 purchase ²¹ . Expected Outcomes: 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 . Important Tips: 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 growth ²⁵ . 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. Acronyms and Abbreviations: RA = robotic-assisted MI = minimally invasive TLIF = transforaminal lumbar interbody fusion PSIS = posterior superior iliac spine PLIF = posterior lumbar interbody fusion LLIF = lateral lumbar interbody fusion ALIF = anterior lumbar interbody fusion DRB = dynamic reference base BMP = bone morphogenetic protein BMI = body mass index CT = computed tomography XR = X-ray MRI = magnetic resonance imaging OR = operating room AP = anteroposterior CSF = cerebrospinal fluid VAS = visual analog scale EBL = estimated blood loss LOS = length of stay PT = physical therapy PRN = as needed

Case: A 69-year-old man underwent a C3-4 anterior cervical discectomy and fusion and developed postoperative hypoglossal and glossopharyngeal palsies that resolved with symptomatic treatment. Conclusion: Cranial nerve palsy is a rare and possibly under-reported injury after higher-level cervical spine surgery. Conscientious positioning and awareness of these nerves during surgical exposure are crucial to minimizing cranial nerve palsies. Proper workup to identify these palsies and differentiate them from other complications is necessary to guide proper treatment.