Optimizing Surgical Performance Using Preoperative Virtual Reality Planning: A Systematic Review.

BACKGROUND: Surgery is often a complex process that requires detailed 3-dimensional anatomical knowledge and rigorous interplay between team members to attain ideal operational efficiency or "flow." Virtual Reality (VR) represents a technology by which to rehearse complex plans and communicate precise steps to a surgical team prior to entering the operating room. The objective of this study was to evaluate the use of VR for preoperative surgical team planning and interdisciplinary communication across all surgical specialties. METHODS: A systematic review of the literature was performed examining existing research on VR use for preoperative surgical team planning and interdisciplinary communication across all surgical fields in order to optimize surgical efficiency. MEDLINE, SCOPUS, CINAHL databases were searched from inception to July 31, 2022 using standardized search clauses. A qualitative data synthesis was performed with particular attention to preoperative planning, surgical efficiency optimization, and interdisciplinary collaboration/communication techniques determined a priori. Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines were followed. All included studies were appraised for their quality using the Medical Education Research Study Quality Instrument (MERSQI) tool. RESULTS: One thousand and ninety-three non-duplicated articles with abstract and full text availability were identified. Thirteen articles that examined preoperative VR-based planning techniques for optimization of surgical efficiency and/or interdisciplinary communication fulfilled inclusion and exclusion criteria. These studies had a low-to-medium methodological quality with a MERSQI mean score of 10.04 out of 18 (standard deviation 3.61). CONCLUSIONS: This review demonstrates that time spent rehearsing and visualizing patient-specific anatomical relationships in VR may improve operative efficiency and communication across multiple surgical specialties.

Anatomical positional changes in the lateral lumbar interbody fusion.

INTRODUCTION: ALIFs and LLIFs are now becoming more utilized for adult spinal disease. As technologies advance, so do surgical techniques, with surgeons now modifying traditional supine-ALIF and lateral-LLIF to lateral-ALIF and prone-LLIF approaches to allow for more efficient surgeries. The objective of this study is to characterize the anatomical changes in the surgical corridor that occur with changes in patient positioning. METHODS: MRIs of ten healthy volunteers were evaluated in five positions: supine, prone with hips flexed, prone with hips extended, lateral with hips flexed, and lateral with hips extended. All lateral scans were in the left lateral decubitus position. The anatomical changes of the psoas muscles, inferior vena cava, aorta, iliac vessels were assessed with relation to fixed landmarks on the disc spaces from L1 to S1. RESULTS: The most anteriorly elongated ipsilateral to approach psoas when compared to supine was seen in lateral-flexed position (- 5.82 mm, p < 0.001), followed by lateral-extended (- 2.23 mm, p < 0.001), then prone-flexed (- 1.40 mm, p = 0.014), and finally supine and prone-extended (- 0.21 mm, p = 0.643). The most laterally extending or "thickest" psoas was seen in prone-flexed (- 1.40 mm, p = 0.004) and prone-extended (- 1.17 mm, p = 0.002). The psoas was "thinnest" in lateral-extended (2.03 mm, p < 0.001) followed by lateral-flexed (1.11 mm, p = 0.239). The contralateral psoas did not move as anteriorly as the ipsilateral. 3D volumetric analysis showed that the greatest changes in the psoas occur at its proximal and distal poles near T12-L1 and L4-S1. In lateral-flexed compared to prone-extended, the IVC moves medially to the left (p < 0.001). The aorta moves laterally to the left (p = 0.005). The venous structures appeared more full and open in the lateral positions and flattened in the supine and prone positions. The arteries remain in full calibre. CONCLUSION: The MRI anatomical evaluation shows that the psoas, and therefore lumbar plexus, and vasculature move significantly with changes in positioning. This is important for preoperative planning for proper intraoperative execution from preoperative supine MRI. Understanding that the psoas and vessels move the most anteriorly in the lateral-flexed position and to a least degree in the prone-extended is essential for safe and efficient utilization of techniques such as the traditional LLIF, traditional ALIF, prone-LLIF.

Nationwide Trends in Carotid Endarterectomy and Carotid Artery Stenting in the Post-CREST Era.

Background and Purpose- The CREST (Carotid Revascularization Endarterectomy Versus Stenting Trial) demonstrated equivalent composite outcomes between carotid endarterectomy (CEA) and carotid artery stenting (CAS) for treating carotid stenosis. We investigated nationwide trends in these procedures and associated periprocedural stroke, myocardial infarction, death, cost, and readmission rates since CREST outcomes were published. Methods- We queried the Nationwide Readmissions Database to identify patients undergoing CEA and CAS for asymptomatic and symptomatic carotid stenosis from 2010 to 2015. Patients were matched based on demographics, comorbidities, and severity of illness. Results- In total, 378 354 CEA and 57 273 CAS patients were treated during this 6-year period. CEA volume decreased by an average of 2669 procedures annually (P=0.001) with stable CAS volume (P=0.225). After matching, CEA patients had a higher rate of periprocedural stroke than CAS patients, driven by increased stroke risk in symptomatic CEA patients (8.1% versus 5.6%; odds ratio, 1.47 [CI, 1.29-1.68]; P<0.001) but a lower rate of overall inpatient mortality (0.8% versus 1.4%; odds ratio, 0.57 [CI, 0.48-0.68]; P<0.001). CEA patients were less likely to be readmitted within 30 days (7.2% versus 8.0%; odds ratio, 0.90 [CI, 0.84-0.96]; P=0.018) and 90 days (12.3% versus 14.1%; odds ratio, 0.86 [CI, 0.81-0.90]; P<0.001), and mean hospital costs were lower for CEA compared with CAS ($14 433 versus $19 172; P<0.001). Conclusions- The procedural treatment of carotid stenosis has changed dramatically in the post-CREST era. When matched for characteristics and illness severity, patients undergoing CEA had a higher rate of perioperative stroke than patients undergoing CAS, primarily among symptomatic patients. These findings are in contrast to the findings of CREST, which showed nearly twice the risk of stroke in CAS patients compared with CEA patients. CEA was associated with lower procedure cost and readmission rate.

Single-position prone lateral approach: cadaveric feasibility study and early clinical experience.

OBJECTIVE: Lateral lumbar interbody fusion (LLIF) is a useful minimally invasive technique for achieving anterior interbody fusion and preserving or restoring lumbar lordosis. However, achieving circumferential fusion via posterior instrumentation after an LLIF can be challenging, requiring either repositioning the patient or placing pedicle screws in the lateral position. Here, the authors explore an alternative single-position approach: LLIF in the prone lateral (PL) position. METHODS: A cadaveric feasibility study was performed using 2 human cadaveric specimens. A retrospective 2-center early clinical series was performed for patients who had undergone a minimally invasive lateral procedure in the prone position between August 2019 and March 2020. Case duration, retractor time, electrophysiological thresholds, implant size, screw accuracy, and complications were recorded. Early postoperative radiographic outcomes were reported. RESULTS: A PL LLIF was successfully performed in 2 cadavers without causing injury to a vessel or the bowel. No intraoperative subsidence was observed. In the clinical series, 12 patients underwent attempted PL surgery, although 1 case was converted to standard lateral positioning. Thus, 11 patients successfully underwent PL LLIF (89%) across 14 levels: L2-3 (2 of 14 [14%]), L3-4 (6 of 14 [43%]), and L4-5 (6 of 14 [43%]). For the 11 PL patients, the mean (± SD) age was 61 ± 16 years, mean BMI was 25.8 ± 4.8, and mean retractor time per level was 15 ± 6 minutes with the longest retractor time at L2-3 and the shortest at L4-5. No intraoperative subsidence was noted on routine postoperative imaging. CONCLUSIONS: Performing single-position lateral transpsoas interbody fusion with the patient prone is anatomically feasible, and in an early clinical experience, it appeared safe and reproducible. Prone positioning for a lateral approach presents an exciting opportunity for streamlining surgical access to the lumbar spine and facilitating more efficient surgical solutions with potential clinical and economic advantages.

Use of a wrist-mounted device for continuous outpatient physiologic monitoring after transsphenoidal surgery: a pilot study.

PURPOSE: Patients who undergo transsphenoidal surgery can experience hormonal, electrolyte, and fluid disturbances in the postoperative period leading to outpatient readmissions for medical management. Our goal was to determine whether use of a wrist-mounted physiologic tracking device is feasible in this setting and whether changes or trends in these parameters after discharge can help predict aberrant physiology in these patients. METHODS: Wrist-mounted physiologic tracking devices that transmit data via Bluetooth to a mobile device were used to monitor patients. Preoperative baseline data and postoperative data were aggregated daily to compare within-patient and between-patient trends. RESULTS: Of 11 patients enrolled in the study, 1 was readmitted for symptomatic hyponatremia. Device data completeness ranged from 78 to 93% with the exception of oxygen saturation (25% completeness). The patient with hyponatremia had a significantly lower baseline level of activity compared with other patients. Nonreadmitted patient activity variables (steps, calories, and distance) decreased by 48-52% after the operation (P < 0.001). The activity variables for the patient with hyponatremia were statistically unchanged after the operation; however, the patient did experience a significant decrease in heart rate compared with baseline. CONCLUSION: Deployment of a wrist-based physiologic tracking device is feasible for surgical patients in elective clinical practice. Overall, the device was associated with good patient adherence and high patient satisfaction. Patient activity significantly decreased after surgery. A significant decrease in heart rate was detected in a patient with hyponatremia who required readmission, which reflects the known intravascular volume expansion in this state.

Association of Angiotensin-Converting Enzyme Inhibitors with Increased Mortality Among Patients with Isolated Severe Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI) is associated with one-third of all deaths from trauma. Preinjury exposure to cardiovascular drugs may affect TBI outcomes. Angiotensin-converting enzyme inhibitors (ACEIs) exacerbate brain cell damage and worsen functional outcomes in the laboratory setting. ß-blockers (BBs), however, appear to be associated with reduced mortality among patients with isolated TBI. OBJECTIVE: Examine the association between preinjury ACEI and BB use and clinical outcome among patients with isolated TBI. METHODS: A retrospective cohort study of patients age ≥ 40 years admitted to an academic level 1 trauma center with isolated TBI between January 2010 and December 2014 was performed. Isolated TBI was defined as a head Abbreviated Injury Scale (AIS) score ≥ 3, with chest, abdomen, and extremity AIS scores ≤ 2. Preinjury medication use was determined through chart review. All patients with concurrent BB use were initially excluded. In-hospital mortality was the primary measured outcome. RESULTS: Over the 5-year study period, 600 patients were identified with isolated TBI who were naive to BB use. There was significantly higher mortality (P = .04) among patients who received ACEI before injury (10 of 96; 10%) than among those who did not (25 of 504; 5%). A multivariate stepwise logistic regression analysis revealed a threefold increased risk of mortality in the ACEI cohort (P < .001), which was even greater than the twofold increased risk of mortality associated with an Injury Severity Score ≥ 16. A second analysis that included patients who received preinjury BBs (n = 98) demonstrated slightly reduced mortality in the ACEI cohort with only a twofold increased risk in multivariate analysis (P = .05). CONCLUSIONS: Preinjury exposure to ACEIs is associated with an increase in mortality among patients with isolated TBI. This effect is ameliorated in patients who receive BBs, which provides evidence that this class of medications may provide a protective benefit.

Optimizing Surgical Efficiency in Complex Spine Surgery Using Virtual Reality as a Communication Technology to Promote a Shared Mental Model: A Case Series and Review.

BACKGROUND AND OBJECTIVES: Virtual reality (VR) is an emerging technology that can be used to promote a shared mental model among a surgical team. We present a case series demonstrating the use of 3-dimensional (3D) VR models to visually communicate procedural steps to a surgical team to promote a common operating objective. We also review the literature on existing uses of VR for preoperative communication and planning in spine surgery. METHODS: Narrations of 3 to 4-minute walkthroughs were created in a VR visualization platform, converted, and distributed to team members through text and email the night before surgical intervention. A VR huddle was held immediately before the intervention to refine surgical goals. After the intervention, the participating team members' perceptions on the value of the tool were assessed using a survey that used a 5-point Likert scale. MEDLINE, Google Scholar, and Dimensions AI databases were queried from July 2010 to October 2022 to examine existing literature on preoperative VR use to plan spine surgery. RESULTS: Three illustrative cases are presented with accompanying video. Postoperative survey results demonstrate a positive experience among surgical team members after reviewing preoperative plans created with patient-specific 3D VR models. Respondents felt that preoperative VR video review was "moderately useful" or more useful in improving their understanding of the operational sequence (71%, 5/7), in enhancing their ability to understand their role (86%, 6/7), and in improving the safety or efficiency of the case (86%, 6/7). CONCLUSION: We present a proof of concept of a novel preoperative communication tool used to create a shared mental model of a common operating objective for surgical team members using narrated 3D VR models. Initial survey results demonstrate positive feedback among respondents. There is a paucity of literature investigating VR technology as a means for preoperative surgical communication in spine surgery. ETHICS: Institutional review board approval (IRB-300009785) was obtained before this study.

Virtual Reality-Enabled Resident Education of Lateral-Access Spine Surgery.

OBJECTIVE: Lateral-access spine surgery has many benefits, but adoption has been limited by a steep learning curve. Virtual reality (VR) is gaining popularity and lends itself as a useful tool in enhancing neurosurgical resident education. We thus sought to assess whether VR-based simulation could enhance the training of neurosurgery residents in lateral spine surgery. METHODS: Neurosurgery residents completed a VR-based lateral spine module on lateral patient positioning and performing lateral lumbar interbody fusion using the PrecisionOS VR system on the Meta Quest 2 headset. Simulation occurred 1×/week every other week for a total of 3 simulations over 6 weeks. Pre- and postintervention surveys as well as intrasimulation performance metrics were assessed over time. RESULTS: The majority of resident participants showed improvement in performance scores, including an automated PrecisionOS precision score, number of radiographs used within the simulation, and time to completion. All participants showed improvement in comfort with anatomic landmarks for lateral access surgery, confidence performing lateral surgery without direct supervision, and assessing fluoroscopy in spine surgery for hardware placement and image interpretation. Participant perception on the utility of VR as an educational tool also improved. CONCLUSIONS: VR-based simulation enhanced neurosurgical residents' ability to understand lateral access surgery. Immersive surgical simulation resulted in improved resident confidence with surgical technique and workflow, perceived improvement in anatomical knowledge, and simulation performance scores. Trainee perceptions on virtual simulation and training as a curriculum supplement also improved following completion of VR training.

Reliability of a Novel Classification System for Thoracic Disc Herniations.

STUDY DESIGN: This is a cross-sectional survey. OBJECTIVE: The aim was to assess the reliability of a proposed novel classification system for thoracic disc herniations (TDHs). SUMMARY OF BACKGROUND DATA: TDHs are complex entities varying substantially in many factors, including size, location, and calcification. To date, no comprehensive system exists to categorize these lesions. METHODS: Our proposed system classifies 5 types of TDHs using anatomic and clinical characteristics, with subtypes for calcification. Type 0 herniations are small (≤40% of spinal canal) TDHs without significant spinal cord or nerve root effacement; type 1 are small and paracentral; type 2 are small and central; type 3 are giant (>40% of spinal canal) and paracentral; and type 4 are giant and central. Patients with types 1 to 4 TDHs have correlative clinical and radiographic evidence of spinal cord compression. Twenty-one US spine surgeons with substantial TDH experience rated 10 illustrative cases to determine the system's reliability. Interobserver and intraobserver reliability were determined using the Fleiss kappa coefficient. Surgeons were also surveyed to obtain consensus on surgical approaches for the various TDH types. RESULTS: High agreement was found for the classification system, with 80% (range 62% to 95%) overall agreement and high interrater and intrarater reliability (kappa 0.604 [moderate to substantial agreement] and kappa 0.630 [substantial agreement], respectively). All surgeons reported nonoperative management of type 0 TDHs. For type 1 TDHs, most respondents (71%) preferred posterior approaches. For type 2 TDHs, responses were roughly equivalent for anterolateral and posterior options. For types 3 and 4 TDHs, most respondents (72% and 68%, respectively) preferred anterolateral approaches. CONCLUSIONS: This novel classification system can be used to reliably categorize TDHs, standardize description, and potentially guide the selection of surgical approach. Validation of this system with regard to treatment and clinical outcomes represents a line of future study.

Spine Deformity Associated with Chiari I Malformation and Syringomyelia.

The management of scoliosis in patients with Chiari I malformation and syringomyelia is a complex decision-making process, which is changing due to evolving evidence. Headache and scoliosis are common presenting symptoms of an underlying Chiari. History, physical examination, and screening with MRI are cornerstones of diagnosis. Posterior fossa decompression provides curve stabilization or regression in about half of patients. In those who require spinal fusion, careful attention must be paid to intraoperative neurological monitoring data to minimize risk of neurologic injury.

Neurosurgery Applicant Perspective of Neurosurgery Residency Websites.

OBJECTIVE: Applicants rely heavily on virtual information in the form of neurosurgery residency websites (NRWs) to better understand a program's culture, faculty, and opportunities. There is a paucity of information regarding the value of NRW on applicant decision making. The advent of the supplemental ERAS application and continuation of virtual interviews may increase the propensity of which applicants use NRW. The objective of our study was to distribute a survey to further understand applicants' perceptions and opinions of NRW, as well as provide future direction for NRW optimization. METHODS: The current study is a single-institution, retrospective survey design. A survey was designed via Qualtrics software to evaluate applicant demographics, resident education, resident recruitment, and future directions. The survey includes the most frequently used variables on NRW. The survey was distributed to neurosurgery applicants who received an interview at the University of Alabama at Birmingham. Data were analyzed using Microsoft Excel. RESULTS: Among the 293 applicants who received a link to the survey, 87/293 (29.7%) completed it. Respondents elected that useful website variables were "resident rotation schedules and hospital locations," "faculty listings and biographies," and "neurosurgery residency websites served as a first impression of a neurosurgery residency program." More than half of the respondents agreed that their rank list would not be the same without an NRW. The most strongly received statement for future directions was "Neurosurgery residency programs will benefit from renovating their residency website." CONCLUSIONS: Our data suggest NRWs play a vital role in resident recruitment and decision making. Residency programs will benefit from this data and may use it to restructure their virtual recruitment tools and discover innovative virtual recruitment strategies. Our team elucidated the most important variables found on NRWs and proposed future directions for their improvement and the virtual application and recruitment process.

Technique for Validation of Intraoperative Navigation in Minimally Invasive Spine Surgery.

BACKGROUND: Intraoperative 3-dimensional navigation is an enabling technology that has quickly become a commonplace in minimally invasive spine surgery (MISS). It provides a useful adjunct for percutaneous pedicle screw fixation. Although navigation is associated with many benefits, including improvement in overall screw accuracy, navigation errors can lead to misplaced instrumentation and potential complications or revision surgery. It is difficult to confirm navigation accuracy without a distant reference point. OBJECTIVE: To describe a simple technique for validating navigation accuracy in the operating room during MISS. METHODS: The operating room is set up in a standard fashion for MISS with intraoperative cross-sectional imaging available. A 16-gauge needle is placed within the bone of the spinous process before intraoperative cross-sectional imaging. The entry level is chosen such that the space between the reference array and the needle encompasses the surgical construct. Before placing each pedicle screw, accuracy is verified by placing the navigation probe over the needle. RESULTS: This technique has identified navigation inaccuracy and led to repeat cross-sectional imaging. No screws have been misplaced in the senior author's cases since adopting this technique, and there have been no complications attributable to the technique. CONCLUSION: Navigation inaccuracy is an inherent risk in MISS, but the described technique may mitigate this risk by providing a stable reference point.

Morbid Obesity Increases Length of Surgery in Elective Anterior Cervical Discectomy and Fusion Procedures but Not Readmission or Reoperation Rates: A Cohort Study.

BACKGROUND: As the obesity epidemic grows, the number of morbidly obese patients undergoing anterior cervical discectomy and fusion (ACDF) continues to increase. Despite the association of obesity with perioperative complications in anterior cervical surgery, the impact of morbid obesity on ACDF complications remains controversial, and studies examining morbidly obese cohorts are limited. METHODS: A single-institution, retrospective analysis of patients undergoing ACDF from September 2010 to February 2022 was performed. Demographic, intraoperative, and postoperative data were collected via review of the electronic medical record. Patients were categorized as nonobese (body mass index [BMI] <30), obese (BMI 30-39.9), or morbidly obese (BMI ≥40). Associations of BMI class with discharge disposition, length of surgery, and length of stay were assessed using multivariable logistic regression, multivariable linear regression, and negative binomial regression, respectively. RESULTS: The study included 670 patients undergoing single-level or multilevel ACDF: 413 (61.6%) nonobese, 226 (33.7%) obese, and 31 (4.6%) morbidly obese patients. BMI class was associated with prior history of deep venous thrombosis (P < 0.01), pulmonary thromboembolism (P < 0.05), and diabetes mellitus (P < 0.001). In bivariate analysis, there was no significant association between BMI class and reoperation or readmission rates at 30, 60, or 365 days postoperatively. In multivariable analysis, greater BMI class was associated with increased length of surgery (P = 0.03), but not length of stay or discharge disposition. CONCLUSIONS: For patients undergoing ACDF, greater BMI class was associated with increased length of surgery, but not reoperation rate, readmission rate, length of stay, or discharge disposition.

Advances in Pediatric Surgery Simulation-Based Training.

Pediatric surgery is the diagnostic, operative, and postoperative surgical care of children with congenital and acquired anomalies and diseases. The early history of the specialty followed the classic "see one, do one, teach one" philosophy of training but has since evolved to modern methods including simulation-based training (SBT). Current trainees in pediatric surgery face numerous challenges, such as the decreasing incidence of congenital disease and reduced work hours. SBT consists of several modalities that together assist in the acquisition of technical skills and improve performance in the operating room. SBT has evolved to incorporate simulator models and video gaming technology, in parallel with the development of simulation in other surgical and non-surgical pediatric fields. SBT has advanced to a level of sophistication that means that it can improve the skills of not only pediatric surgery trainees but also practicing attending surgeons. In this review, we will discuss the history of pediatric surgery, simulation in pediatric surgery training, and the potential direction of pediatric surgical simulation training in the future.

Rod Attachment Induces Significant Strain in Lumbosacral Fixation.

STUDY DESIGN: This was a laboratory investigation. OBJECTIVE: Rod attachment can induce significant pedicle screw-and-rod pre- strain that may predispose the instrumentation to failure. This study investigated how in vitro L5-S1 rod strain and S1 screw strain during rod-screw attachment (pre-strain) compared with strains recorded during pure-moment bending ( test- strain). SUMMARY OF BACKGROUND DATA: The lumbosacral junction is highly vulnerable to construct failure due to rod fatigue fracture, sacral screw pull-out, and screw fatigue fracture. MATERIALS AND METHODS: Twelve cadaveric specimens were instrumented with L2-ilium pedicle screws and rod. Strain gauges on contoured rods and sacral screws recorded strains during sequential rod-to-screw tightening (pre-strains). The same instrumented constructs were immediately tested in a 6-degree-of-freedom apparatus under continuous loading to 7.5 Nm in multidirectional bending while recording instrumentation test-strains. Rod and screw pre-strains and test-strains were compared using 1-way repeated-measures analysis of variance followed by Holm-Sidák paired analysis (significant at P <0.05). RESULTS: The mean first (171±192 µE) and second (322±269 µE) rod attachment pre-strains were comparable to mean test-strains during flexion (265±109 µE) and extension (315±125 µE, P ≥0.13). The mean rod attachment pre-strain was significantly greater than mean test-strains during bidirectional lateral bending (40±32 µE ipsilateral and 39±32 µE contralateral, P <0.001) and axial rotation (72±60 µE ipsilateral and 60±57 µE contralateral, P <0.001). The mean first and second sacral screw pre-strains during rod attachment (1.03±0.66 and 1.39±1.00 Nm, respectively) did not differ significantly ( P =0.41); however, the mean sacral screw pre-strain during final (second) rod attachment was significantly greater than screw test-strains during all directions of movement (≤0.81 Nm, P ≤0.03). CONCLUSIONS: Instrumentation pre-strains imposed during in vitro rod-screw attachment of seemingly well-contoured rods in L2-ilium fixation are comparable to, and at times greater than, strains experienced during in vitro bending. Spine surgeons should be aware of the biomechanical consequences of rod contouring and attachment on construct vulnerability.

Biomechanical Assessment of a Novel Sharp-Tipped Screw for 1-Step Minimally Invasive Pedicle Screw Placement Under Navigation.

BACKGROUND: The objective of this study was to assess the pullout force of a novel sharp-tipped screw developed for single-step, minimally invasive pedicle screw placement guided by neuronavigation compared with the pullout force for traditional screws. METHODS: A total of 60 human cadaveric lumbar pedicles were studied. Three different screw insertion techniques were compared: (A) Jamshidi needle and Kirschner wire without tapping; (B) Jamshidi needle and Kirschner wire with tapping; and (C) sharp-tipped screw insertion. Pullout tests were performed at a displacement rate of 10 mm/min recorded at 20 Hz. Mean values of these parameters were compared using paired t tests (left vs right in the same specimen): A vs B, A vs C, and B vs C. Additionally, 3 L1-L5 spine models were used for timing each screw insertion technique for a total of 10 screw insertions for each technique. Insertion times were compared using 1-way analysis of variance. RESULTS: The mean pullout force for insertion technique A was 1462.3 (597.5) N; for technique B, it was 1693.5 (805.0) N; and for technique C, it was 1319.0 (735.7) N. There was no statistically significant difference in pullout force between techniques (P > 0.08). The average insertion time for condition C was significantly less than that for conditions A and B (P < 0.001). CONCLUSIONS: The pullout force of the novel sharp-tipped screw placement technique is equivalent to that of traditional techniques. The sharp-tipped screw placement technique appears biomechanically viable and has the advantage of saving time during insertion. CLINICAL RELEVANCE: Single-step screw placement using high resolution 3-dimensional navigation has the potential to streamline workflow and reduce operative time.

Predictors of subsidence after lateral lumbar interbody fusion.

OBJECTIVE: Lateral lumbar interbody fusion (LLIF) facilitates the restoration of disc height and the indirect decompression of neural elements. However, these benefits are lost when the graft subsides into the adjacent endplates. The factors leading to subsidence after LLIF are poorly understood. This article presents a case series of patients who underwent LLIF and reports factors correlating with subsidence. METHODS: A retrospective review of a consecutive, prospectively collected, single-institution database of patients who underwent LLIF over a 29-month period was performed. The degree of subsidence was measured on the basis of postoperative imaging. The timing of postoperative subsidence was determined, and intraoperative fluoroscopic images were reviewed to determine whether subsidence occurred as a result of endplate violation. The association of subsidence with age, sex, cage size and type, bone density, and posterior instrumentation was investigated. RESULTS: One hundred thirty-one patients underwent LLIF at a total of 204 levels. Subsidence was observed at 23 (11.3%) operated levels. True subsidence, attributable to postoperative cage settling, occurred for 12 (5.9%) of the levels; for the remaining 11 (5.4%) levels, subsidence was associated with intraoperative endplate violation noted on fluoroscopy during cage placement. All subsidence occurred within 12 weeks of surgery. Univariate analysis showed that the prevalence of true subsidence was significantly lower among patients with titanium implants (0 of 55; 0%) than among patients with polyetheretherketone cages (12 of 149; 8.1%) (p = 0.04). In addition, the mean ratio of graft area to inferior endplate area was significantly lower among the subsidence levels (0.34) than among the nonsubsidence levels (0.42) (p < 0.01). Finally, subsidence among levels with posterior fixation (4.4% [6/135]) was not significantly different than among those without posterior fixation (8.7% [6/69]) (p = 0.23). Multivariate analysis results showed that the ratio of cage to inferior endplate area was the only significant predictor of subsidence in this study (p < 0.01); increasing ratios were associated with a decreased likelihood of subsidence. CONCLUSIONS: Overall, the prevalence of subsidence after LLIF was low in this clinical series. Titanium cages were associated with a lower prevalence of observed subsidence on univariate analysis; however, multivariate analysis demonstrated that this effect may be attributable to the increased surface area of these cages relative to the inferior endplate area.

Microendoscopic lumbar discectomy with general versus local anesthesia: A systematic review and meta-analysis.

Background: While general anesthesia (GA) is the most commonly used anesthetic method during lumbar microendoscopic discectomy (MED), local ± epidural anesthesia (LA) has been gaining popularity as an alternate method. Theoretical advantages of LA include reduced morbidity of anesthesia and improved surgeon-patient communication facilitating less nerve root manipulation and yielding improved surgical outcomes. The objective of this systematic review is to examine the impact of anesthesia type on patient reported outcomes (PROs) and complications with MED. Methods: A systematic review and meta-analysis of the available literature examining MED performed under GA or LA was performed. The PubMed, EMBASE and SCOPUS databases were searched from inception to August 16, 2021, utilizing strict inclusion and exclusion criteria with all studies reporting greater than 6 months of follow-up and PRO data. PROs including Visual Analog Scale (VAS)-leg/back, Oswestry Disability Index (ODI), Japanese Orthopedic Association (JOA) and/or 36-Item Short Form (SF-36) physical component scores were collected. Complication, recurrent disc herniation, durotomy and reoperation rates as well as surgical factors were collected. All outcomes were compared between pooled studies examining GA or LA. Risk of bias was assessed with the Newcastle-Ottawa Scale. Results: A total of 23 studies consisting of 2,868 patients (1,335 GA, 1,533 LA) were included in the meta-analysis. There were no significant differences between GA and LA groups in regard to overall complication rate, durotomy rate, recurrent disc herniation rate, reoperation rate, blood loss, or surgical time (p > 0.05). Both groups demonstrated significant improvements in ODI and JOA (p<0.0004), however leg and back VAS was only improved in GA (p<0.0025) and not in LA (p>0.058), and SF-36 only in LA (p=0.003). Conclusions: Patients undergoing MED under both anesthetic techniques demonstrated significant improvements in ODI and JOA, with no significant differences in complication or reoperation rates. However, patients undergoing GA demonstrated significant improvement in VAS leg and back pain at last follow-up while LA did not. LA may be offered to carefully selected patients and prior studies have demonstrated reduced costs and risks with LA. Conclusions are limited by a high level of study bias and heterogeneity. Further investigation is needed to assess the true effects of GA and LA on outcomes after MED.

Outpatient outcomes of patients with femoral nerve neurapraxia after prone lateral lumbar interbody fusion at L4-5.

OBJECTIVE: Single-position prone lateral lumbar interbody fusion (LLIF) improves the efficiency of staged minimally invasive lumbar spine surgery. However, laterally approaching the lumbar spine, especially L4-5 with the patient in the prone position, could increase the risk of complications and presents unique challenges, including difficult ergonomics, psoas migration, and management of the nearby lumbar plexus. The authors sought to identify postoperative femoral neurapraxia after single-position prone LLIF at L4-5 to better understand how symptoms evolve over time. METHODS: This retrospective analysis examined a prospectively maintained database of LLIF patients who were treated by two surgeons (J.S.U. and J.D.T.). Patients who underwent single-position prone LLIF at L4-5 and percutaneous pedicle screw fixation for lumbar stenosis or spondylolisthesis were included if they had at least 6 weeks of follow-up. Outpatient postoperative neurological symptoms were analyzed at 6-week, 3-month, and 6-month follow-up evaluations. RESULTS: Twenty-nine patients (16 women [55%]; overall mean ± SD age 62 ± 11 years) met the inclusion criteria. Five patients (17%) experienced complications, including 1 (3%) who had a femoral nerve injury with resultant motor weakness. The mean ± SD transpsoas retractor time was 14.6 ± 6.1 minutes, the directional anterior electromyography (EMG) threshold before retractor placement was 20.1 ± 10.2 mA, and the directional posterior EMG threshold was 10.4 ± 9.1 mA. All patients had 6-week clinical follow-up evaluations. Ten patients (34%) reported thigh pain or weakness at their 6-week follow-up appointment, compared with 3/27 (11%) at 3 months and 1/20 (5%) at 6 months. No association was found between directional EMG threshold and neurapraxia, but longer transpsoas retractor time at L4-5 was significantly associated with femoral neurapraxia at 6-week follow-up (p = 0.02). The only case of femoral nerve injury with motor weakness developed in a patient with a retractor time that was nearly twice as long as the mean time (27.0 vs 14.6 minutes); however, this patient fully recovered by the 3-month follow-up evaluation. CONCLUSIONS: To our knowledge, this is the largest study with the longest follow-up duration to date after single-position prone LLIF at L4-5 with percutaneous pedicle screw fixation. Although 34% of patients reported ipsilateral sensory symptoms in the thigh at the 6-week follow-up evaluation, only 1 patient sustained a nerve injury; this resulted in temporary weakness that resolved by the 3-month follow-up evaluation. Thus, longer transpsoas retractor time at L4-5 during prone LLIF is associated with increased ipsilateral thigh symptoms at 6-week follow-up that may resolve over time.

Surgical anatomy of minimally invasive lateral approaches to the thoracolumbar junction.

OBJECTIVE: The thoracolumbar (TL) junction spanning T11 to L2 is difficult to access because of the convergence of multiple anatomical structures and tissue planes. Earlier studies have described different approaches and anatomical structures relevant to the TL junction. This anatomical study aims to build a conceptual framework for selecting and executing a minimally invasive lateral approach to the spine for interbody fusion at any level of the TL junction with appropriate adjustments for local anatomical variations. METHODS: The authors reviewed anatomical dissections from 9 fresh-frozen cadaveric specimens as well as clinical case examples to denote key anatomical relationships and considerations for approach selection. RESULTS: The retroperitoneal and retropleural spaces reside within the same extracoelomic cavity and are separated from each other by the lateral attachments of the diaphragm to the rib and the L1 transverse process. If the lateral diaphragmatic attachments are dissected and the diaphragm is retracted anteriorly, the retroperitoneal and retropleural spaces will be in direct continuity, allowing full access to the TL junction. The T12-L2 disc spaces can be reached by a conventional lateral retroperitoneal exposure with the rostral displacement of the 11th and 12th ribs. With caudally displaced ribs, or to expose T12-L1 disc spaces, the diaphragm can be freed from its lateral attachments to perform a retrodiaphragmatic approach. The T11-12 disc space can be accessed purely through a retropleural approach without significant mobilization of the diaphragm. CONCLUSIONS: The entirety of the TL junction can be accessed through a minimally invasive extracoelomic approach, with or without manipulation of the diaphragm. Approach selection is determined by the region of interest, degree of diaphragmatic mobilization required, and rib anatomy.