The field of spine surgery has changed significantly over the past few decades as once technological fantasy has become reality. The advent of stereotaxis, intra-operative navigation, endoscopy, and percutaneous instrumentation have altered the landscape of spine surgery. The concept of minimally invasive spine (MIS) surgery has blossomed over the past ten years and now robot-assisted spine surgery is being championed by some as another potential paradigm altering technological advancement. The application of robotics in other surgical specialties has been shown to be a safe and feasible alternative to the traditional, open approach. In 2004 the Mazor Spine Assist robot was approved by FDA to assist with placement of pedicle screws and since then, more advanced robots with promising clinical outcomes have been introduced. Currently, robotic platforms are limited to pedicle screw placement. However, there are centers investigating the role of robotics in decompression, dural closure, and pre-planned osteotomies.Robot-assisted spine surgery has been shown to increase the accuracy of pedicle screw placement and decrease radiation exposure to surgeons. However, modern robotic technology also has certain disadvantages including a high introductory cost, steep learning curve, and inherent technological glitches. Currently, robotic spine surgery is in its infancy and most of the objective evidence available regarding its benefits draws from the use of robots in a shared-control model to assist with the placement of pedicle screws. As artificial intelligence software and feedback sensor design become more sophisticated, robots could facilitate other, more complex surgical tasks such as bony decompression or dural closure. The accuracy and precision afforded by the current robots available for use in spinal surgery potentially allow for even less tissue destructive and more meticulous MIS surgery. This article aims to provide a contemporary review of the use of robotics in MIS surgery.

OBJECTIVENumerous studies have attempted to delineate the normative value for T1S−CL (T1 slope minus cervical lordosis) as a marker for both cervical deformity and a goal for correction similar to how PI-LL (pelvic incidence–lumbar lordosis) mismatch informs decision making in thoracolumbar adult spinal deformity (ASD). The goal of this study was to define the relationship between T1 slope (T1S) and cervical lordosis (CL).METHODSThis is a retrospective review of a prospective database. Surgical ASD cases were initially analyzed. Analysis across the sagittal parameters was performed. Linear regression analysis based on T1S was used to provide a clinically applicable equation to predict CL. Findings were validated using the postoperative alignment of the ASD patients. Further validation was then performed using a second, normative database. The range of normal alignment associated with horizontal gaze was derived from a multilinear regression on data from asymptomatic patients.RESULTSA total of 103 patients (mean age 54.7 years) were included. Analysis revealed a strong correlation between T1S and C0–7 lordosis (r = 0.886), C2–7 lordosis (r = 0.815), and C0–2 lordosis (r = 0.732). There was no significant correlation between T1S and T1S−CL. Linear regression analysis revealed that T1S−CL assumed a constant value of 16.5° (R2 = 0.664, standard error 2°). These findings were validated on the postoperative imaging (mean absolute error [MAE] 5.9°). The equation was then applied to the normative database (MAE 6.7° controlling for McGregor slope [MGS] between −5° and 15°). A multilinear regression between C2–7, T1S, and MGS demonstrated a range of T1S−CL between 14.5° and 26.5° was necessary to maintain horizontal gaze.CONCLUSIONSNormative CL can be predicted via the formula CL = T1S − 16.5° ± 2°. This implies a threshold of deformity and aids in providing a goal for surgical correction. Just as pelvic incidence (PI) can be used to determine the ideal LL, T1S can be used to predict ideal CL. This formula also implies that a kyphotic cervical alignment is to be expected for individuals with a T1S < 16.5°.

The advent and widespread adoption of pedicle screw instrumentation prompted the need for image guidance in spine surgery to improve accuracy and safety. Although the conventional method, fluoroscopy, is readily available and inexpensive, concerns regarding radiation exposure and the drive to provide better visual guidance spurred the development of computer-assisted navigation.Contemporaneously, a non-navigated robotic guidance platform was also introduced as a competing modality for pedicle screw placement. Although the robot could provide high precision trajectory guidance by restricting four of the six degrees of freedom (DOF), the lack of real-time depth control and high capital acquisition cost diminished its popularity, while computer-assisted navigation platforms became increasingly sophisticated and accepted. The recent integration of real-time 3D navigation with robotic platforms has resulted in a resurgence of interest in robotics in spine surgery with the recent introduction of numerous navigated robotic platforms. The currently available navigated robotic spine surgery platforms include the

OBJECT Evaluation of lumbar stability is fundamentally dependent on a clear understanding of normal lumbar motion. There are inconsistencies in reported lumbar motion across previously published studies, and it is unclear which provide the most reliable reference data. New technology now allows valid and reliable determination of normal lumbar intervertebral motion (IVM). The object of this study was to provide normative reference data for lumbar IVM and center of rotation (COR) using validated computer-assisted measurement tools. METHODS Sitting flexion-extension radiographs were obtained in 162 asymptomatic volunteers and then analyzed using a previously validated and widely used computerized image analysis method. Each lumbar level was subsequently classified as “degenerated” or “nondegenerated” using the Kellgren-Lawrence classification. Of the 803 levels analyzed, 658 were nondegenerated (Kellgren-Lawrence grade < 2). At each level of the lumbar spine, the magnitude of intervertebral rotation and translation, the ratio of translation per degree of rotation (TPDR), and the position of the COR were calculated in the nondegenerative cohort. Translations were calculated in millimeters and percentage endplate width. RESULTS All parameters were significantly dependent on the intervertebral level. The upper limit of the 95% CIs for anteroposterior intervertebral translation in this asymptomatic cohort ranged from 2.1 mm (6.2% endplate width) to 4.6 mm (13.3% endplate width). Intervertebral rotation upper limits ranged from 16.3° to 23.5°. The upper limits for TPDR ranged from 0.49% to 0.82% endplate width/degree. The COR coordinates were clustered in level-dependent patterns. CONCLUSIONS New normal values for IVM, COR, and the ratio of TPDR in asymptomatic nondegenerative lumbar levels are proposed, providing a reference for future interpretation of sagittal plane motion in the lumbar spine.

Background:The authors present a novel case of a hemangioblastoma of the optic nerve producing bilateral optic tract edema in a patient with von Hippel–Lindau disease (VHL). This is the only case in the literature documenting optic tract edema secondary to a hemangioblastoma of the optic nerve.Case Description:The patient was a 34-year-old female in whom this lesion was causing retro-orbital pain and proptosis. She had previously lost vision in the symptomatic eye secondary to a retinal hemangioblastoma. The optic nerve lesion was excised by sectioning the optic nerve both proximally and distally to the lesion. There were no complications and patient's symptoms resolved postoperatively. A follow-up magnetic resonance imaging (MRI) scan revealed complete excision of the mass and resolution of the optic tract edema.Conclusion:Optic nerve hemangioblastomas in patients with VHL are rare, but are manageable with meticulous microneurosurgery and with appropriate patient expectations. This is the first known case of an optic nerve hemangioblastoma producing bilateral optic tract edema, which resolved after resection of the prechiasmal tumor. Hemangioblastoma should remain in the differential diagnosis of optic nerve tumors, especially in the setting of VHL.