Real-time navigation guidance with intraoperative CT imaging for pedicle screw placement using an augmented reality head-mounted display: a proof-of-concept study.

OBJECTIVE: Augmented reality (AR) has the potential to improve the accuracy and efficiency of instrumentation placement in spinal fusion surgery, increasing patient safety and outcomes, optimizing ergonomics in the surgical suite, and ultimately lowering procedural costs. The authors sought to describe the use of a commercial prototype Spine AR platform (SpineAR) that provides a commercial AR head-mounted display (ARHMD) user interface for navigation-guided spine surgery incorporating real-time navigation images from intraoperative imaging with a 3D-reconstructed model in the surgeon's field of view, and to assess screw placement accuracy via this method. METHODS: Pedicle screw placement accuracy was assessed and compared with literature-reported data of the freehand (FH) technique. Accuracy with SpineAR was also compared between participants of varying spine surgical experience. Eleven operators without prior experience with AR-assisted pedicle screw placement took part in the study: 5 attending neurosurgeons and 6 trainees (1 neurosurgical fellow, 1 senior orthopedic resident, 3 neurosurgical residents, and 1 medical student). Commercially available 3D-printed lumbar spine models were utilized as surrogates of human anatomy. Among the operators, a total of 192 screws were instrumented bilaterally from L2-5 using SpineAR in 24 lumbar spine models. All but one trainee also inserted 8 screws using the FH method. In addition to accuracy scoring using the Gertzbein-Robbins grading scale, axial trajectory was assessed, and user feedback on experience with SpineAR was collected. RESULTS: Based on the Gertzbein-Robbins grading scale, the overall screw placement accuracy using SpineAR among all users was 98.4% (192 screws). Accuracy for attendings and trainees was 99.1% (112 screws) and 97.5% (80 screws), respectively. Accuracy rates were higher compared with literature-reported lumbar screw placement accuracy using FH for attendings (99.1% vs 94.32%; p = 0.0212) and all users (98.4% vs 94.32%; p = 0.0099). The percentage of total inserted screws with a minimum of 5° medial angulation was 100%. No differences were observed between attendings and trainees or between the two methods. User feedback on SpineAR was generally positive. CONCLUSIONS: Screw placement was feasible and accurate using SpineAR, an ARHMD platform with real-time navigation guidance that provided a favorable surgeon-user experience.

Sublaminar fixation for traumatic lumbar fracture subluxation with lateral listhesis in a 2-year-old patient.

Pediatric spinal trauma can present a surgeon with difficult management decisions given the rarity of these cases, pediatric anatomy, and a growing spine. The need to stabilize a traumatically unstable pediatric spine can be an operative challenge given the lack of instrumentation available. The authors present a surgical technique and an illustrative case that may offer a novel, less disruptive method of stabilization. A 2-year-old girl presented after an assault with an L1-2 fracture subluxation with lateral listhesis and fractured jumped facets exhibited on CT scans. CT also showed intact growth plates at the vertebral body, pedicles, and posterior elements. MRI showed severe ligamentous injury, conus medullaris compression, and an epidural hematoma. Neurologically, the patient moved both lower extremities asymmetrically. Given the severity of the deformity and neurological examination and disruption of the stabilizing structures, the authors made the decision to surgically decompress the L-1 and L-2 segments with bilateral laminotomies, evacuate the epidural hematoma, and reduce the deformity with sublaminar stabilization using braided polyester cables bilaterally, thus preserving the growth plates. They also performed a posterolateral onlay fusion at L-1 and L-2 using autograft and allograft placed due to the facet disruption. At the 42-month follow-up, imaging showed fusion of L-1 and L-2 with good alignment, and the hardware was subsequently explanted. The patient was neurologically symmetric in strength, ambulating, and had preserved alignment. Her bones and spinal canal continued to grow in relation to the other levels.

Combination scaffolds of salmon fibrin, hyaluronic acid, and laminin for human neural stem cell and vascular tissue engineering.

UNLABELLED: Human neural stem/progenitor cells (hNSPCs) are good candidates for treating central nervous system (CNS) trauma since they secrete beneficial trophic factors and differentiate into mature CNS cells; however, many cells die after transplantation. This cell death can be ameliorated by inclusion of a biomaterial scaffold, making identification of optimal scaffolds for hNSPCs a critical research focus. We investigated the properties of fibrin-based scaffolds and their effects on hNSPCs and found that fibrin generated from salmon fibrinogen and thrombin stimulates greater hNSPC proliferation than mammalian fibrin. Fibrin scaffolds degrade over the course of a few days in vivo, so we sought to develop a novel scaffold that would retain the beneficial properties of fibrin but degrade more slowly to provide longer support for hNSPCs. We found combination scaffolds of salmon fibrin with interpenetrating networks (IPNs) of hyaluronic acid (HA) with and without laminin polymerize more effectively than fibrin alone and generate compliant hydrogels matching the physical properties of brain tissue. Furthermore, combination scaffolds support hNSPC proliferation and differentiation while significantly attenuating the cell-mediated degradation seen with fibrin alone. HNSPCs express two fibrinogen-binding integrins, αVß1 and α5ß1, and several laminin binding integrins (α7ß1, α6ß1, α3ß1) that can mediate interaction with the scaffold. Lastly, to test the ability of scaffolds to support vascularization, we analyzed human cord blood-derived endothelial cells alone and in co-culture with hNSPCs and found enhanced vessel formation and complexity in co-cultures within combination scaffolds. Overall, combination scaffolds of fibrin, HA, and laminin are excellent biomaterials for hNSPCs. STATEMENT OF SIGNIFICANCE: Interest has increased recently in the development of biomaterials as neural stem cell transplantation scaffolds to treat central nervous system (CNS) injury since scaffolds improve survival and integration of transplanted cells. We report here on a novel combination scaffold composed of fibrin, hyaluronic acid, and laminin to support human neural stem/progenitor cell (hNSPC) function. This combined biomaterial scaffold has appropriate physical properties for hNSPCs and the CNS, supports hNSPC proliferation and differentiation, and attenuates rapid cell-mediated scaffold degradation. The hNSPCs and scaffold components synergistically encourage new vessel formation from human endothelial cells. This work marks the first report of a combination scaffold supporting human neural and vascular cells to encourage vasculogenesis, and sets a benchmark for biomaterials to treat CNS injury.

Odontoid pseudotumor and serial postfusion radiographic evaluation in a patient with a C1-2 mass.

Odontoid pseudotumor is a mass occurring around the odontoid process in the cervical spine and can cause significant neurological symptoms at the craniocervical junction due to compression of the spinal cord and cervicomedullary junction at this level. A literature review was performed to provide input on options for treatment and prognosis for this lesion. The literature search found 12 papers in which pseudotumor was treated with posterior decompression and fixation. Posterior decompression and fixation with serial imaging to monitor the size of the pseudotumor postsurgery is a safe and effective treatment option for odontoid pseudotumors.

Reduction of displaced Hangman's fracture by compression across crossed translaminar screws.

Hangman's fractures are fractures across the pars interarticularis of C2 with possible subluxation of C2 on C3. However, no criteria have been defined for the specific indications for surgical fixation. We describe a 30-year old man who sustained a displaced Hangman's fracture after a motor vehicle accident. The fracture was successfully reduced, in the operating room, by compression across crossed translaminar screws while lifting C1 relative to C2. Intra-operative reduction of a displaced Hangman's fracture by compression across crossed translaminar screws is safe and technically feasible.

Traumatic fracture of thin pedicles secondary to extradural meningeal cyst.

Spinal dural meningoceles and diverticula are meningeal cysts that have a myriad of clinical presentations and sequelae, secondary to local mass effect. Our objective is to report a technical case report, illustrating a traumatic spinal injury with multiple pedicle fractures, secondary to atrophic lumbar pedicles as well as the diagnostic workup and surgical management of this problem. Posterior lumbar decompression, resection of the meningeal cyst, ligation of the cyst ostium, instrumentation, and fusion were performed with the assistance of intraoperative isocentric fluoroscopy. The cyst's point of communication was successfully located with intraoperative fluoroscopy and the lesion was successfully excised. We suggest that patients with traumatic spinal injuries, having evidence of pre-existing anomalous bony architecture, undergo advanced imaging studies, to rule out intraspinal pathology. The positive clinical and radiographic results support the removal and closure of the pre-existing meningeal cyst at the time of treatment of traumatic spinal injury. Intraoperative isocentric fluoroscopy is a helpful tool in the operative management of these lesions.

Video-assisted thoracoscopic surgery combined with a tubular retractor system for minimally invasive thoracic discectomy.

BACKGROUND: Several approaches have been proposed for the treatment of thoracic disc herniations. Posterior approaches include transpedicular, costotransversectomy, and lateral extracavitary; anterior approaches include retropleural and transpleural thoracotomy and thoracoscopy. OBJECTIVE: We present a novel minimally invasive approach to thoracic discectomies, combining thoracoscopy and a tubular retractor system. We discuss the utility and safety of this technique. METHODS: The patient is placed in a lateral decubitus position, with a double-lumen endotracheal tube for single-lung ventilation. With use of thoracoscopic techniques, the disc space is identified; approximately 2 cm of the head and neck of the rib is removed to expose the pedicle of the lower vertebral body. The tubular retractor is deployed with continuous thoracoscopic visualization and a trough is created anterior to the canal by drilling the adjacent vertebral bodies straddling the disc space. The operative microscope is utilized to dissect the disc, pulling it anteriorly into the trough. RESULTS: There were 5 patients in the past 9 months who were candidates for anterior thoracic discectomy. Disc herniations from T3-4 to T10-11 were treated without any significant complications. Patients were followed up clinically and radiographically. CONCLUSION: Combining thoracoscopy with the tubular retractors allows continuous monitoring of the lung, aorta, and vena cava during the placement of the retractors. Additionally, use of the tubular retractors, as opposed to a complete thoracoscopic discectomy reduces the working distance and allows the use of the microscope with 3- dimensional visualization, thus enhancing the safety of this approach.

Utility of neurophysiological monitoring using dorsal column mapping in intramedullary spinal cord surgery.

OBJECT: Intramedullary spinal cord tumors can displace the surrounding neural tissue, causing enlargement and distortion of the normal cord anatomy. Resection requires a midline myelotomy to avoid injury to the posterior columns. Locating the midline for myelotomy is often difficult because of the distorted anatomy. Standard anatomical landmarks may be misleading in patients with intramedullary spinal cord tumors due to cord rotation, edema, neovascularization, or local scar formation. Misplacement of the myelotomy places the posterior columns at risk of significant postoperative disability. The authors describe a technique for mapping the dorsal column to accurately locate the midline. METHODS: A group of 10 patients with cervical and thoracic intramedullary spinal cord lesions underwent dorsal column mapping in which a strip electrode was used to define the midline. After the laminectomy and durotomy, a custom-designed multielectrode grid was placed on the exposed dorsal surface of the spinal cord. The electrode is made up of 8 parallel Teflon-coated stainless-steel wires (76-microm diameter, spaced 1 mm apart) embedded in silastic with each of the wires stripped of its insulating coating along a length of 2 mm. This strip electrode maps the amplitude gradient of conducted spinal somatosensory evoked potentials elicited by bilateral tibial nerve stimulation. Using these recordings, the dorsal columns are topographically mapped as lying between two adjacent numbers. RESULTS: The authors conducted a retrospective analysis of the preoperative, immediate, and short-term postoperative neurological status, focusing especially on posterior column function. There were 8 women and 2 men whose mean age was 52 years. There were 4 ependymomas, 1 subependymoma, 1 gangliocytoma, 1 anaplastic astrocytoma, 1 cavernous malformation, and 2 symptomatic syringes requiring shunting. In all patients the authors attempted to identify the midline by using anatomical landmarks, and then proceeded with dorsal column mapping to identify the midline electrophysiologically. In the 2 patients with syringomyelia and in 5 of the patients with tumors, the authors were unable to identify the midline anatomically with any certainty. In 2 patients with intramedullary tumors, they were able to identify the midline anatomically with certainty. Dorsal column mapping allowed identification of the midline and to confirm the authors' anatomical localization. In 2 patients with intramedullary tumors, posterior column function was preserved only on 1 side. All other patients had intact posterior column function preoperatively. CONCLUSIONS: Dorsal column mapping is a useful technique for guiding the surgeon in locating the midline for myelotomy in intramedullary spinal cord surgery. In conjunction with somatosensory evoked potential, motor evoked potential, and D-wave recordings, we have been able to reduce the surgical morbidity related to dorsal column dysfunction in this small group of patients.

Revision of Chiari decompression for patients with recurrent syrinx.

The management of adult patients with Chiari malformation associated with syrinx remains controversial. Although an abundance of literature exists for the pediatric population, there is an absence of guidelines for the adult population. It is unclear which of the different surgical approaches is appropriate in patients with Chiari I malformations and syringomyelia. A 36-year-old female patient had a posterior fossa decompression 3years prior to recurrence. The patient developed recurrent symptoms with sensory loss and hyperesthesia in the right upper extremity. MRI revealed decreased cerebrospinal fluid flow at the craniocervical junction. The patient was taken to the operating room for revision of the posterior fossa decompression, lysis of adhesions and duraplasty. Re-exploration of a Chiari decompression, lysis of adhesions and revision duraplasty is an effective treatment option for recurrent syringomyelia.

Transcervical drainage of epidural and retropharyngeal abscess.

This report describes treatment of concurrent epidural and retropharyngeal abscesses and presents a novel surgical approach to treating this pathology. The treatment of epidural and retropharyngeal prevertebral abscesses requires surgical drainage in addition to systemic antibiotics. After the patient's airway is secured, urgent otolaryngologic surgery consultation is obtained for transoral drainage of the retropharyngeal abscesses to minimize risk to vascular and nervous structures within the neck. If epidural extension is also present, urgent neurosurgical evaluation and decompression may be necessary. We report a patient with an epidural and prevertebral abscess. A posterior approach was taken for wide decompression of the cervical spine and evacuation of the epidural collection. During this procedure, under fluoroscopic guidance, an 8 Fr soft rubber catheter was slowly advanced ventrally in the epidural space through the C5-6 intervertebral disk into the retropharyngeal abscess with evacuation of this collection as well. Using a single, wide posterior approach, the dorsal epidural, the ventral epidural, and prevertebral abscesses were all successfully evacuated. This report describes a novel approach for evacuation of prevertebral abscess concurrent with multilevel laminectomy for epidural abscess evacuation.

Fixation of the axis.

OBJECTIVE: To review and compare the techniques of fixation of the axis vertebral segment. Also, to review the anatomy of the axis vertebrae, ligamentous attachments, and unique biomechanics of this segment. METHODS: The use of wire, cable, screw, and plate fixation techniques are reviewed and discussed in the treatment of fractures of C1 and C2 along with utilization of the halo vest and cervical collar during the postoperative period. RESULTS: All fixation methods were useful. However, the appropriate fixation technique is best determined by the local anatomy (eg, anomalous vertebral artery), posterior element fractures, or the necessity to remove the posterior elements for treatment of the underlying condition. CONCLUSION: New techniques for fixation and instrumentation for fixation of the axis are available. Advanced imaging allows for advanced aggressive instrumentation while avoiding injury to adjacent structures. Biomechanical studies have influenced the utility and popularity of each technique.

Distal subgaleal-peritoneal shunt migration into the abdominal wall with subsequent formation of a pre-peritoneal pseudocyst: a rare complication.

Distal ventriculo-peritoneal shunt migration and extra-peritoneal CSF pseudocyst formation are unusual complications of shunt placement. We present a 65-year-old-female who received a subgaleal-peritoneal shunt to decompress a post-surgical subgaleal fluid collection. Eight weeks later, shunt series showed tight coiling of the distal catheter, and operative exploration found the distal shunt tip to have migrated superficial to the rectus sheath, where it had become encapsulated in a pre-peritoneal CSF pseudocyst. Migration of the distal catheter into the abdominal wall was likely due to local inflammation of the inner surface of the abdomen, with pressure from intestinal peristaltic movements and intra-abdominal pressure, and continued inflammation at the distal catheter tip may have caused formation of a pre-peritoneal CSF pseudocystic dilatation. To date, this is the first reported case of distal shunt migration into the abdominal wall with subsequent formation of an extra-peritoneal pseudocyst and represents a rare event in the surgical management of peritoneal shunts.

Use of isocentric fluoroscopy during transoral odontoidectomy.

The intra-operative isocentric C-arm (Siremobil Iso-C 3D; Siemens Medical Solutions, Erlangen, Germany) allows for the acquisition and immediate interpretation of multiplanar three-dimensional images. The utility of isocentric fluoroscopy in surgery of the spine has been well described, in patients with percutaneous kyphoplasty, anterior cervical discectomy and fusion, fracture repair, as well as in percutaneous instrumentation at cervical, thoracic and lumbar levels. Two patients who underwent transoral odontoidectomy are presented in whom isocentric fluoroscopy was utilized to provide an intra-operative CT scan. Use of this technology allowed the surgeon to detect residual bone peri-operatively, thus allowing for a more extensive decompression and excellent clinical results. Intra-operative isocentric fluoroscopy in transoral odontoidectomy allows for peri-operative detection of residual bone fragments and intra-operative confirmation of complete decompression.

Digital photography using the intraoperative microscope in neurosurgery.

BACKGROUND: The ability to obtain high-resolution intraoperative microscopic images has previously been reserved for those with expensive microscope-mounted cameras, standard optical or digital. The authors review the technique and utility of intraoperative digital photography through the microscope. METHODS: We present a simple technique for obtaining high-quality digital micrographs without the need for special equipment that may be expensive, complex, and/or dedicated to a specific operative microscope. RESULTS: Images and video may be obtained using a standard personal digital camera. CONCLUSIONS: Use of the technique presented provides the surgeon with the ability to acquire high-quality intraoperative microphotographs and video.

Syringocephaly.

Syringomyelia is associated with Arnold-Chiari Type I malformations. Syringobulbia describes the phenomenon of syrinx extension into the brain stem. Syringocephaly is the further dissection of the fluid-filled cavity into the cerebral peduncles and cerebrum. In this case report, we describe a patient who presented with bulbar, sensory, motor, and coordination deficits both ipsilateral and contralateral to the lesion. This is most likely attributable to the wandering course the syrinx takes as it dissects through the spinal cord and into the internal capsule. This ill-defined syrinx disrupts various nuclei and fasciculi, both pre- and post-decussation, thus explaining the multiple deficits on each side. We initially treated this patient with a suboccipital craniectomy, C1 laminectomy, and duraplasty, which mildly improved his deficits. During follow-up, the patient was then found to have an exacerbation of his symptoms, at which time we performed a VP shunt revision (the patient had a history of hydrocephalus treated by a functioning VP shunt). Approximately 2 weeks after revision of the VP shunt, the patient had worsening of his symptoms, which we treated with a syringopleural shunt. This proved to be the most effective treatment with the greatest clinical improvement. Several months later, however, the patient died secondary to pulmonary disease exacerbated by VP shunt infection. In this paper, we also review the literature regarding the formation and treatment of syringocephaly, a rare and poorly understood entity.