Evolution of Cervical Endoscopic Spine Surgery: Current Progress and Future Directions-A Narrative Review.

Cervical endoscopic spine surgery is rapidly evolving and gaining popularity for the treatment of cervical radiculopathy and myelopathy. This approach significantly reduces muscular damage and blood loss by minimizing soft tissue stripping, leading to less postoperative pain and a faster postoperative recovery. As scientific evidence accumulates, the efficacy and safety of cervical endoscopic spine surgery are continually affirmed. Both anterior and posterior endoscopic approaches have surfaced as viable alternative treatments for various cervical spine pathologies. Newer techniques, such as endoscopic-assisted fusion, the anterior transcorporeal approach, and unilateral laminotomy for bilateral decompression, have been developed to enhance clinical outcomes and broaden surgical indications. Despite its advantages, this approach faces challenges, including a steep learning curve, increased radiation exposure for both surgeons and patients, and a relative limitation in addressing multi-level pathologies. However, the future of cervical endoscopic spine surgery is promising, with potential enhancements in clinical outcomes and safety on the horizon. This progress is fueled by integrating advanced imaging and navigation technologies, applying regional anesthesia for improved and facilitated postoperative recovery, and incorporating cutting-edge technologies, such as augmented reality. With these advancements, cervical endoscopic spine surgery is poised to broaden its scope in treating cervical spine pathologies while maintaining the benefits of minimized tissue damage and rapid recovery.

Advancing Prone-Transpsoas Spine Surgery: A Narrative Review and Evolution of Indications with Representative Cases.

The Prone Transpsoas (PTP) approach to lumbar spine surgery, emerging as an evolution of lateral lumbar interbody fusion (LLIF), offers significant advantages over traditional methods. PTP has demonstrated increased lumbar lordosis gains compared to LLIF, owing to the natural increase in lordosis afforded by prone positioning. Additionally, the prone position offers anatomical advantages, with shifts in the psoas muscle and lumbar plexus, reducing the likelihood of postoperative femoral plexopathy and moving critical peritoneal contents away from the approach. Furthermore, operative efficiency is a notable benefit of PTP. By eliminating the need for intraoperative position changes, PTP reduces surgical time, which in turn decreases the risk of complications and operative costs. Finally, its versatility extends to various lumbar pathologies, including degeneration, adjacent segment disease, and deformities. The growing body of evidence indicates that PTP is at least as safe as traditional approaches, with a potentially better complication profile. In this narrative review, we review the historical evolution of lateral interbody fusion, culminating in the prone transpsoas approach. We also describe several adjuncts of PTP, including robotics and radiation-reduction methods. Finally, we illustrate the versatility of PTP and its uses, ranging from 'simple' degenerative cases to complex deformity surgeries.

Chirality-induced avalanche magnetization of magnetite by an RNA precursor.

Homochirality is a hallmark of life on Earth. To achieve and maintain homochirality within a prebiotic network, the presence of an environmental factor acting as a chiral agent and providing a persistent chiral bias to prebiotic chemistry is highly advantageous. Magnetized surfaces are prebiotically plausible chiral agents due to the chiral-induced spin selectivity (CISS) effect, and they were utilized to attain homochiral ribose-aminooxazoline (RAO), an RNA precursor. However, natural magnetic minerals are typically weakly magnetized, necessitating mechanisms to enhance their magnetization for their use as effective chiral agents. Here, we report the magnetization of magnetic surfaces by crystallizing enantiopure RAO, whereby chiral molecules induce a uniform surface magnetization due to the CISS effect, which spreads across the magnetic surface akin to an avalanche. Chirality-induced avalanche magnetization enables a feedback between chiral molecules and magnetic surfaces, which can amplify a weak magnetization and allow for highly efficient spin-selective processes on magnetic minerals.

Does Coherence Affect the Multielectron Oxygen Reduction Reaction?

The oxygen reduction reaction (ORR) is the key for oxygen-based respiration and the operation of fuel cells. It involves the transmission of two pairs of electrons. We probed what type of interaction between the electrons is required to enable their efficient transfer into the oxygen. We show experimentally that the transfer of the electrons is controlled by the "hidden property" and present a theoretical model suggesting that it is related to coherent phase relations between the two electrons. Using spin polarization electrochemical measurements, with electrodes coated with different thicknesses of chiral coating, we confirm the special relation between the electrons. This relation is destroyed by multiple scattering events that result in the formation of hydrogen peroxide, which indicates a reduction in the ORR efficiency. Another indication for the possible role of coherence is the fluctuations in the reaction efficiency as a function of thickness of the chiral coated electrode.

Machine learning for automated and real-time two-dimensional to three-dimensional registration of the spine using a single radiograph.

OBJECTIVE: The goal of this work was to methodically evaluate, optimize, and validate a self-supervised machine learning algorithm capable of real-time automatic registration and fluoroscopic localization of the spine using a single radiograph or fluoroscopic frame. METHODS: The authors propose a two-dimensional to three-dimensional (2D-3D) registration algorithm that maximizes an image similarity metric between radiographic images to identify the position of a C-arm relative to a 3D volume. This work utilizes digitally reconstructed radiographs (DRRs), which are synthetic radiographic images generated by simulating the x-ray projections as they would pass through a CT volume. To evaluate the algorithm, the authors used cone-beam CT data for 127 patients obtained from an open-source de-identified registry of cervical, thoracic, and lumbar scans. They systematically evaluated and tuned the algorithm, then quantified the convergence rate of the model by simulating C-arm registrations with 80 randomly simulated DRRs for each CT volume. The endpoints of this study were time to convergence, accuracy of convergence for each of the C-arm's degrees of freedom, and overall registration accuracy based on a voxel-by-voxel measurement. RESULTS: A total of 10,160 unique radiographic images were simulated from 127 CT scans. The algorithm successfully converged to the correct solution 82% of the time with an average of 1.96 seconds of computation. The radiographic images for which the algorithm converged to the solution demonstrated 99.9% registration accuracy despite utilizing only single-precision computation for speed. The algorithm was found to be optimized for convergence when the search space was limited to a ± 45° offset in the right anterior oblique/left anterior oblique, cranial/caudal, and receiver rotation angles with the radiographic isocenter contained within 8000 cm3 of the volumetric center of the CT volume. CONCLUSIONS: The investigated machine learning algorithm has the potential to aid surgeons in level localization, surgical planning, and intraoperative navigation through a completely automated 2D-3D registration process. Future work will focus on algorithmic optimizations to improve the convergence rate and speed profile.

Easily processable spin filters: exploring the chiral induced spin selectivity of bowl-shaped chiral subphthalocyanines.

High spin polarization (SP) in studies of chiral induced spin selectivity (CISS) is only observed when chiral molecules are properly organized. This is generally achieved by using anchoring groups or complex supramolecular polymers. A new class of spin filters based on bowl-shaped aromatics is reported, which form high-quality thin-films by simply spin-coating and displaying high spin filtering properties. In particular, we fabricate devices containing enantiopure tribromo-subphthalocyanines (SubPcs), and measure the CISS effect by means of magnetic conductive probe atomic force microscopy (mc-AFM). Circular dichroism and AFM experiments reveal that the resulting thin-film presents a well-ordered chiral structure. Remarkably, the resulting devices show SPs as high as ca. 50%, which are comparable to those obtained by using the current complex methodologies. These results boost the potential of bowl-shaped aromatics as easily processable spin filters, opening new frontiers toward realistic and efficient spintronic devices based on the CISS effect.

Minimally invasive modification of the Goel-Harms atlantoaxial fusion technique: a case series and illustrative guide.

OBJECTIVE: The Goel-Harms atlantoaxial screw fixation technique for the treatment of atlantoaxial instability and unstable odontoid fractures is reliable and reproducible for a variety of anatomies. The drawbacks of the technique are the potential for significant bleeding from the C2 nerve root venous plexus and the risks associated with posterior midline exposure and retraction, such as pain and wound complications. The authors developed a minimally invasive surgical (MIS) modification of the Goel-Harms technique using intra-articular grafting to facilitate placement of percutaneous lateral mass and pars screws with extended tabs for minimally invasive subfascial rod placement. The objective of this study was to present the authors' first series of 5 patients undergoing minimally invasive modification in comparison with 51 patients undergoing open atlantoaxial fusion. METHODS: A retrospectiveanalysis of patient comorbid conditions, blood loss, length of surgery, and length of stay was performed on patients undergoing Goel-Harms instrumented fusion (GHIF) for unstable odontoid fractures performed between 2016 and 2021. RESULTS: Patients undergoing the minimally invasive procedure showed significantly less blood loss than those undergoing the open atlantoaxial fusion procedure, with a median blood loss of 30 ml compared with 150 ml using the open technique (p < 0.01). The patients showed no significant differences in length of stay (2 days for MIS vs 4 days for open atlantoaxial fusion, p = 0.25). There were no significant differences in length of surgery for MIS, but a possible trend toward increased operative duration (234 vs 151 minutes, p = 0.112). CONCLUSIONS: In this small pilot study, it was shown that MIS-GHIF can be performed with decreased blood loss in atlantoaxial instability and odontoid fractures. This technique may allow for greater and safer application of the procedure in the elderly and infirm.

Optical Activity and Spin Polarization: The Surface Effect.

Chirality ('handedness') is a property that underlies a broad variety of phenomena in nature. Chiral molecules appear in two forms, and each is a mirror image of the other, the two enantiomers. The chirality of molecules is associated with their optical activity, and circular dichroism is commonly applied to identify the handedness of chiral molecules. Recently, the chiral induced spin selectivity (CISS) effect was established, according to which transfer of electrons within chiral molecules depends on the electron's spin. Which spin is preferred depends on the handedness of the chiral molecule and the direction of motion of the electron. Several experiments in the past indicated that there may be a relation between the optical activity of the molecules and their spin selectivity. Here, we show that for a molecule containing several stereogenic axes, when adsorbed on a metal substrate, the peaks in the CD spectra have the same signs for the two enantiomers. This is not the case when the molecules are adsorbed on a nonmetallic substrate or dissolved in solution. Quantum chemical simulations are able to explain the change in the CD spectra upon adsorption of the molecules on conductive and nonconductive surfaces. Surprisingly, the CISS properties are similar for the two enantiomers when adsorbed on the metal substrate, while when the molecules are adsorbed on nonmetallic surface, the preferred spin depends on the molecule handedness. This correlation between the optical activity and the CISS effect indicates that the CISS effect relates to the global polarizability of the molecule.

Spin-induced asymmetry reaction-The formation of asymmetric carbon by electropolymerization.

We describe the spin polarization-induced chirogenic electropolymerization of achiral 2-vinylpyridine, which forms a layer of enantioenhanced isotactic polymer on the electrode. The product formed is enantioenriched in asymmetric carbon polymer. To confirm the chirality of the polymer film formed on the electrode, we also measured its electron spin polarization properties as a function of its thickness. Two methods were used: First, spin polarization was measured by applying magnetic contact atomic force microscopy, and second, magnetoresistance was assessed in a sandwich-like four-point contact structure. We observed high spin-selective electron transmission, even for a layer thickness of 120 nm. A correlation exists between the change in the circular dichroism signal and the change in the spin polarization, as a function of thickness. The spin-filtering efficiency increases with temperature.

Case report: Minimally invasive modification of the Goel-Harms atlantoaxial fusion utilizing percutaneous screws and intra-articular cage is feasible and results in decreased blood loss.

Treatment of atlantoaxial pathology is often associated with significant morbidity and mortality. While surgical techniques for fixation are well established, approaches that minimize blood loss and muscle dissection are advantageous for expediting recovering and minimizing surgical risk. We present a 34-year-old female who presented with a Type III odontoid fracture requiring surgical fixation. She underwent a C1-2 fusion employing a novel minimally invasive modification of the Goel-Harms atlantoaxial fusion using percutaneous screws and intra-articular cage.

Novel use of percutaneous cervical pedicle inlet screws for supplemental posterior fixation after anterior cervical deformity correction.

INTRODUCTION: Correction of cervical deformity can be achieved using anterior cervical fixation and fusion techniques. However, supplemental posterior fixation is a critical component for ensuring biomechanical longevity and favorable patient outcomes. We present a novel percutaneous technique for posterior cervical fixation in patients where cervical pedicle (CP) screws may not be feasible and midline muscle dissection is not needed. METHODS: Three patients presented to our hospital with cervical pathology amendable to circumferential cervical fusion. After adequate deformity correction was performed through an anterior cervical decompression and fusion, staged posterior supplemental fixation was achieved using percutaneous CP inlet (CPI) screws using a percutaneous muscle-sparing approach. RESULTS: All three patients underwent CPI screw placement without postoperative neurovascular complications. Postoperative radiographic follow-up showed the desired, proper screw placement, with continued maintained cervical alignment. CONCLUSIONS: CPI screw placement may be alternative hybrid screw that achieves a advantageous safety profile while also avoiding an open midline exposure.

Gender Disparities in Surgical Treatment of Axis Fractures in Older Adults.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: Gender appears to play in important role in surgical outcomes following acute cervical spine trauma, with current literature suggesting males have a significantly higher mortality following spine surgery. However, no well-adjusted population-based studies of gender disparities in incidence and outcomes of spine surgery following acute traumatic axis injuries exist to our knowledge. We hypothesized that females would receive surgery less often than males, but males would have a higher 1-year mortality following isolated traumatic axis fractures. METHODS: We performed a retrospective cohort study using Medicare claims data that identified US citizens aged 65 and older with ICD-9 (International Classification of Diseases, Ninth Revision) code diagnosis corresponding to isolated acute traumatic axis fracture between 2007 and 2014. Our primary outcome was defined as cumulative incidence of surgical treatment, and our secondary outcome was 1-year mortality. Propensity weighted analysis was performed to balance covariates between genders. Our institutional review board approved the study (IRB #16-0533). RESULTS: There was no difference in incidence of surgery between males and females following acute isolated traumatic axis fractures (7.4 and 7.5 per 100 fractures, respectively). Males had significantly higher 1-year weighted mortality overall (41.7 and 28.9 per 100 fractures, respectively, P < .001). CONCLUSION: Our well-adjusted data suggest there was no significant gender disparity in incidence of surgical treatment over the study period. The data also support previous observations that males have worse outcomes in comparison to females in the setting of axis fractures and spinal trauma regardless of surgical intervention.

Limitations on Postoperative Opioid Prescriptions and Effects on Health Care Resource Use Following Elective Anterior Cervical Discectomy and Fusion.

OBJECTIVE: To curb the misuse of postoperative prescription opioids, the state of North Carolina enacted the Strengthen Opioid Misuse Prevention (STOP) Act of 2017 limiting the duration of initial postoperative opioid prescriptions. The purpose of this study was to evaluate the STOP Act's effect on health care resource use by comparing patient outcomes and opioid prescribing practices following elective anterior cervical discectomy and fusion (ACDF). METHODS: Outcomes and opioid prescribing data were retrospectively evaluated for Pre-Law (January 1, 2017, to December 31, 2017) and Post-Law (January 1, 2018, to December 31, 2018) elective 1- to 4-level anterior cervical discectomy and fusion patient cohorts. Outcome measures included hospital and clinic resource use in the form of emergency department visits, readmissions, major postoperative complications, number of clinic visits, or number of clinic phone calls by patients reporting uncontrolled pain or requesting new opioid prescriptions. Opioid-prescribing practices in the form of discharge prescription number of pills and total morphine milliequivalents also were recorded. RESULTS: Surrounding the STOP Act's implementation, there was no significant difference (P > 0.05) in emergency department visits, readmissions, major complications, number of postoperative clinic visits, or number of clinic phone calls for uncontrolled pain or new prescription requests. There was a significant decline in mean discharge prescription number of pills (89.7 vs. 67.0, P < 0.001), and average morphine milliequivalents (683.4 vs. 509.6, P < 0.001). CONCLUSIONS: This may reflect overprescribing in this population, where larger opioid prescriptions were likely not needed to manage pain that would otherwise require a return to care.

1-Year Mortality and Surgery Incidence in Older US Adults with Cervical Spine Fracture.

BACKGROUND: Traumatic cervical spinal cord injuries (SCIs) can be lethal and are especially dangerous for older adults. Falls from standing and risk factors for a cervical fracture and spinal cord injury increase with age. This study estimates the 1-year mortality for patients with a cervical fracture and resultant SCI and compares the mortality rate with that from an isolated cervical fracture. METHODS: We performed a retrospective cohort study of U.S. Medicare patients older than 65 years of age. International Classification of Diseases (ICD)-9 codes were used to identify patients with a cervical fracture without SCI and patients with a cervical fracture with SCI between 2007 and 2014. Our primary outcome was 1-year mortality cumulative incidence rate; our secondary outcome was the cumulative incidence rate of surgical intervention. Propensity weighted analysis was performed to balance covariates between the groups. RESULTS: The SCI cohort had a 1-year mortality of 36.5%, compared with 31.1% in patients with an isolated cervical fracture (risk difference 5.4% (2.9%-7.9%)). Patients with an SCI were also more likely to undergo surgical intervention compared with those without a SCI (23.1% and 10.3%, respectively; risk difference 12.8% (10.8%-14.9%)). CONCLUSIONS: Using well-adjusted population-level data in older adults, this study estimates the 1-year mortality after SCI in older adults to be 36.5%. The mortality after a cervical fracture with SCI was 5 percentage points higher than in patients without SCI, and this difference is smaller than one might expect, likely representing the frailty of this population and unmeasured covariates.

Comparative Propensity-Weighted Mortality After Isolated Acute Traumatic Axis Fractures in Older Adults.

INTRODUCTION: In older patients with axis fractures, the survival benefit from surgery is unclear due to high baseline mortality. Comparative effectiveness research can provide evidence from population level cohorts. Propensity weighting is the preferred methodology for reducing bias when analyzing national administrative cohort data for these purposes but has not yet been utilized for this important surgical conundrum. We estimate the effect of surgery on mortality after isolated acute traumatic axis fracture in older adults. MATERIALS AND METHODS: We used a retrospective population-based cohort of Medicare patients and generated a propensity score-weighted nonsurgical cohort and compared mortality with and without surgery. This balanced the comorbid conditions of the treatment groups. Incident fractures were defined using a predetermined algorithm based on enrollment, code timing, and billing location. The primary outcome was adjusted all-cause 1-year mortality. RESULTS: From 12 372 beneficiaries with 1-year continuous enrollment and a coded axis fracture, 2676 patients met final inclusion/exclusion criteria. Estimated incidence was 16.5 per 100 000 person-years overall in 2014 (95% confidence interval [CI]: 15.0-18.0) and was stable from 2008 through 2014. Patients with axis fracture had a mean age of 82.8 years, 30.2% were male, and 91.9% were Caucasian. Mortality was 3.8 times higher (CI 3.6-4.1) compared with the general population of older US adults. Propensity-weighted mortality at 1 year for nonsurgical patients was 26.7 of 100 (CI: 24.5-29.0). Mortality for surgical patients was significantly lower (19.7/100; CI 14.5-25.0). Risk difference was 7.0 fewer surgical deaths per 100 patients (CI: 1.3-12.7). Surgical patients aged 65 to 74 years had the largest difference in mortality with 11.2 fewer deaths per 100 (CI: 1.1-21.3). DISCUSSION: Patients with axis fractures are predominantly older Caucasian women and have a higher mortality rate than the general population. Propensity-weighted mortality at 1-year was lower in the surgical patients with the largest risk difference occurring in patients 65 to 74 years old. CONCLUSIONS: Surgery may provide an independent survival benefit in patients aged 65 to 75 years, and the mortality difference diminishes thereafter.

Use of C2 vertebroplasty and stereotactic radiosurgery for treatment of lytic metastasis of the odontoid process.

Improvements in cancer therapy have led to increased patient survival times in spite of metastatic spinal disease in many forms of cancer. Conventional treatment methods often employ radiotherapy with or without surgery depending on the neurological status, mechanical instability, and the extent of tumor. Percutaneous vertebroplasty as well as stereotactic radiosurgery (SRS) have arisen as common modalities of treatment of spinal metastasis in which neurological compromise or spinal instability and deformity is not of significant concern. These treatments, when used in combination, have been shown to provide early pain relief and effective tumor control while avoiding surgical resection, fixation, and lengthy recovery times. We present a case unique in the literature for the use of this combination treatment for tumors of the C2 vertebral body. While limited in application to patients without overt atlantoaxial instability or significant spinal canal compromise, we believe it provides a significant benefit in decreasing morbidity and improving early adherence to systemic therapy.

Variant prostate carcinoma and elevated serum CA-125.

INTRODUCTION: About 10% of tumors derived from nongynecologic, noncoelomic tissues react with the OC125 antibody. Some patients with advanced prostate cancer were found to have elevated serum CA-125 level. MATERIALS AND METHODS: We examined the clinical history of 11 patients with castration resistant prostate cancer and an elevated serum CA-125 level. Pathological review and immunohistochemical staining were performed on tumors from eight of these patients. RESULTS: Patients with advanced prostate cancer and an elevated serum CA-125 level responded to androgen ablative therapy (median duration, 27 months). They were predisposed to develop persistent or recurrent urinary symptoms and visceral metastases. Eight of 11 patients had a low or undetectable serum prostate-specific antigen level (≤ 4 ng/mL) or an elevated serum carcinoembryonic antigen level (> 6 ng/mL). In 3 of 7 patients whose specimens were available for further review, the tumors contained histologic features compatible with a diagnosis of ductal or endometrioid adenocarcinoma of the prostate. CONCLUSIONS: Patients with prostate cancer and an elevated serum CA-125 level have unique clinical and pathologic characteristics. Some of these patients possess tumors compatible with a subtype of prostate cancer known as ductal adenocarcinoma. Additional studies need to be performed to elucidate the biologic basis of the various subtypes of prostate cancer.

Biomechanical analysis of the upper thoracic spine after decompressive procedures.

BACKGROUND CONTEXT: Decompressive procedures such as laminectomy, facetectomy, and costotransversectomy are routinely performed for various pathologies in the thoracic spine. The thoracic spine is unique, in part, because of the sternocostovertebral articulations that provide additional strength to the region relative to the cervical and lumbar spines. During decompressive surgeries, stability is compromised at a presently unknown point. PURPOSE: To evaluate thoracic spinal stability after common surgical decompressive procedures in thoracic spines with intact sternocostovertebral articulations. STUDY DESIGN: Biomechanical cadaveric study. METHODS: Fresh-frozen human cadaveric spine specimens with intact rib cages, C7-L1 (n=9), were used. An industrial robot tested all spines in axial rotation (AR), lateral bending (LB), and flexion-extension (FE) by applying pure moments (±5 Nm). The specimens were first tested in their intact state and then tested after each of the following sequential surgical decompressive procedures at T4-T5 consisting of laminectomy; unilateral facetectomy; unilateral costotransversectomy, and subsequently instrumented fusion from T3-T7. RESULTS: We found that in all three planes of motion, the sequential decompressive procedures caused no statistically significant change in motion between T3-T7 or T1-T12 when compared with intact. In comparing between intact and instrumented specimens, our study found that instrumentation reduced global range of motion (ROM) between T1-T12 by 16.3% (p=.001), 12% (p=.002), and 18.4% (p=.0004) for AR, FE, and LB, respectively. Age showed a negative correlation with motion in FE (r = -0.78, p=.01) and AR (r=-0.7, p=.04). CONCLUSIONS: Thoracic spine stability was not significantly affected by sequential decompressive procedures in thoracic segments at the level of the true ribs in all three planes of motion in intact thoracic specimens. Age appeared to negatively correlate with ROM of the specimen. Our study suggests that thoracic spinal stability is maintained immediately after unilateral decompression at the level of the true ribs. These preliminary observations, however, do not depict the long-term sequelae of such procedures and warrant further investigation.

Minimally invasive, robot-assisted, anterior lumbar interbody fusion: a technical note.

BACKGROUND: Minimally invasive techniques in spine surgery have gained significant popularity due to decreased tissue dissection and destruction, postoperative pain, and hospital stay. The laparoscopic anterior lumbar interbody fusion (ALIF), an innovation in minimally invasive spine surgery, is rarely done because it has marginal benefit over the mini-open ALIF technique in rates of retrograde ejaculation and vascular complications. We propose these outcomes can be improved with enhanced robotic-assisted dissection and exposure for ALIF. PATIENTS: Two patients with single-level degenerative spine disease at L5-S1, associated with mechanical back pain, underwent anterior spinal exposure using the da Vinci S Surgical Robot during ALIF. RESULTS: In this report, we provide the first description of the use of a surgical robot in the dissection and exposure for ALIF in patients with degenerative spine disease. We demonstrate successful use of the da Vinci Surgical Robot in separating the presacral nervous plexus from retroperitoneal structures without postoperative vascular or urological complications over a 1-year follow-up period. CONCLUSION: Use of the robotic assistance in the performance of ALIF is possible without significant operative complications. This technique may provide added benefit over conventional laparoscopic approaches to the spine.