Michael A. Bohl

The role of therapeutic hypothermia in the management of acute spinal cord injury

This review paper investigates the history, efficacy, and administration of systemic and local hypothermia for spinal cord injury (SCI). It summarizes the published experimental and clinical evidence on hypothermia for SCI and analyzes the potential for further research. Early experimental animal research showed that local hypothermia improved recovery and gain of function after acute SCI. However, in the early 1970s, clinical research findings did not coincide with results of these animal trials, which led to a loss of interest in local hypothermia. Since the 1980s, systemic hypothermia has been successfully used to treat SCI in both animals and humans. An abundance of positive evidence suggests that clinical trials are needed to determine the effectiveness of hypothermia for SCI. As a first step, we investigated the published clinical and experimental evidence on the use of hypothermia for SCI patients, who have few available treatment options. We searched PubMed for English-language reports published from 1940 to 2016 containing terms related to SCI treatment using hypothermia. We reviewed all articles on local hypothermia and acute SCI or on systemic hypothermia and acute SCI. Bibliographies of retrieved publications were also screened for additional citations. Ninety-six papers were selected. The clinical use of hypothermia is most successful if applied according to certain optimized parameters (e.g., duration, temperature, time from injury to initiation of cooling, and rewarming time). Preliminary data suggest that modest systemic hypothermia applied for 48h provides the best therapeutic value, but the parameters for use of local hypothermia vary greatly. Experimental evidence and some clinical evidence suggest that both local hypothermia and systemic hypothermia are beneficial for acute SCI. Future research should focus on defining the optimal levels of parameters. Large, multicenter, controlled clinical trials are needed to investigate its therapeutic potential.

Analysis of overlapping surgery in patients undergoing microsurgical aneurysm clipping: acute and long-term outcomes from the Barrow Ruptured Aneurysm Trial

OBJECTIVE Overlapping surgery is a controversial subject in medicine today; however, few studies have examined the outcomes of this practice. The authors analyzed outcomes of patients with acutely ruptured saccular aneurysms who were treated with microsurgical clipping in a prospectively collected database from the Barrow Ruptured Aneurysm Trial. Acute and long-term outcomes for overlapping versus nonoverlapping cases were compared. METHODS During the study period, 241 patients with ruptured saccular aneurysms underwent microsurgical clipping. Patients were separated into overlapping (n = 123) and nonoverlapping (n = 118) groups based on surgical start/stop times. Outcomes at discharge and at 6 months, 1 year, 3 years, and 6 years after surgery were analyzed. RESULTS Patient variables (e.g., age, smoking status, cardiovascular history, Hunt and Hess grade, Fisher grade, and aneurysm size) were similar between the 2 groups. Aneurysm locations were similar, with the exception of the overlapping group having more posterior circulation aneurysms (18/123 [15%]) than the nonoverlapping group (8/118 [7%]) (p = 0.0495). Confirmed aneurysm obliteration at discharge was significantly higher for the overlapping group (109/119 [91.6%]) than for the nonoverlapping group (95/116 [81.9%]) (p = 0.03). Hospital length of stay, discharge location, and proportions of patients with a modified Rankin Scale (mRS) score > 2 at discharge and up to 6 years postoperatively were similar. The mean and median mRS, Glasgow Outcome Scale, Mini-Mental State Examination, National Institutes of Health Stroke Scale, and Barthel Index scores at all time points were not statistically different between the groups. CONCLUSIONS Compared with nonoverlapping surgery, overlapping surgery was not associated with worse outcomes for any variable at any time point, despite the complexity of the surgical management in this patient population. These findings should be considered during the discussion of future guidelines on the practice of overlapping surgery.

The Barrow Innovation Center: A Novel Program in Neurosurgery Resident Education and Medical Device Innovation

Medical innovation is the application of scientific knowledge and problem solving for the betterment of the human condition. Every great advancement in the field of neurosurgery can be traced back to a novel surgical procedure or technology that challenged existing standards of care. Considering the critical importance of innovation to the advancement of neurosurgery, and a surprising lack of formal training in innovation among residency programs, we sought to create a residency training program in neurosurgical innovation. Neurosurgery residents at the authors’ institution envisioned the creation of a program that contained all the necessary equipment, personnel, and information required to bring their ideas from theoretical concepts to functional devices implemented in a clinical setting. The Barrow Innovation Center was established as a result. The center currently comprises a rapid prototyping laboratory and several collaborative partnerships between neurosurgery residents, patent law students, and biomedical engineering students. The creation of this model was guided by an overarching mission to educate the next generation of neurosurgical innovators. With modest start-up capital and strong faculty and institutional support, the center has grown from a simple idea to a multistate, multidisciplinary collaboration in just 18 months; it has generated substantial intellectual property, educational opportunities, and a new business entity. We hope that by continuing to advance the Barrow Innovation Center and its core mission of innovation education, we will advance the field of neurosurgery by providing the next generation of surgeon-scientists with the skills, knowledge, and opportunity needed to revolutionize the field.

Pedicled Vascularized Clavicular Graft for Anterior Cervical Arthrodesis: Cadaveric Feasibility Study, Technique Description, and Case Report

Study Design. Cadaveric feasibility study. Objective. To assess the anatomic and technical feasibility of rotating a clavicular segment on a sternocleidomastoid muscle (SCM) pedicle into the ventral cervical spine using a cadaveric model and to provide the first clinical case description of performing this procedure. Summary of Background Data. Reconstruction of the anterior cervical spine in patients with a high risk of pseudoarthrosis may require the use of a vascularized bone graft (VBG). A vascularized clavicular graft rotated on an SCM pedicle would afford all the benefits of a VBG without the added morbidity of free-tissue transfer; however, this technique has not been described. Methods. A multidisciplinary team hypothesized that it would be anatomically and technically feasible to rotate a pedicled clavicular bone graft from the bottom of C2 to the top of T2 via an anterior approach. Five cadavers underwent bilateral anterior neck dissections for a total of 10 clavicular graft assessments. A case report describes the use of a clavicular VBG in a patient with a 3-level corpectomy defect and a history of failed fusion. Results. Ten clavicles were rotated on an SCM pedicle. The grafts were either harvested as an entire segment or as the superior two-thirds of clavicle, leaving the inferior one-third in situ with pectoralis attachments intact. All grafts reached from the bottom of C2 to the top of T2. When the entire length of exposed clavicle was mobilized, it could cover five to six levels. The case report highlights technical challenges of this procedure in a living patient and provides the clinical context for its potential utility in the reconstruction of the ventral cervical spine. Conclusion. This surgical technique is best suited for patients with long-segment cervical defects and an increased risk of pseudarthrosis. Further clinical experience with this technique is required before definitive conclusions can be made. Level of Evidence: 5

Bedside iohexol ventriculography for patients with obstructive colloid cysts: a protocol to identify auto-fenestration of the septum pellucidum

OBJECTIVE Patients with hydrocephalus secondary to third ventricular colloid cysts can require bilateral external ventricular drain (EVD) placement while awaiting surgery. However, some patients could develop auto-fenestration of the septum pellucidum (AFSP) and only require 1 EVD. We evaluated our experience with bedside iohexol ventriculography and staged EVD placement for patients with obstructive hydrocephalus. METHODS We retrospectively identified 34 patients who had been treated for third ventricular colloid cysts (2013-2016). The preoperative and postoperative data, including age, sex, colloid cyst size, preoperative hydrocephalus, preoperative EVD placement, preoperative iohexol ventriculography, operative approach, intraoperative findings, and postoperative ventriculoperitoneal shunt requirements, were reviewed. RESULTS Hydrocephalus was found in 23 patients (68%) on initial presentation. Nine patients (26%) had EVDs placed before surgery. Six patients (18%) underwent iohexol ventriculography after insertion of a right-sided EVD. Five patients (15%) demonstrated no evidence of ventricular communication. Four patients (67%) required left-sided EVD placement. One patient (17%) had robust communication between the lateral ventricles after intraventricular iohexol injection, which was managed with a single EVD. AFSP was observed during surgical resection of this patients colloid cyst. One other patient who did not undergo preoperative EVD placement was noted to have AFSP intraoperatively, resulting in 2 of 34 patients (6%) with AFSP in our series. CONCLUSIONS A subset of patients with obstruction at the foramina of Monro can develop AFSP. Iohexol ventriculography after unilateral EVD placement allows clinicians to assess for the presence of AFSP and identify patients who can be treated with a single EVD before surgery.

Pedicled Vascularized Bone Grafts for Posterior Lumbosacral Fusion: A Cadaveric Feasibility Study and Case Report

STUDY DESIGN Cadaveric feasibility study and case report. OBJECTIVE To determine if it is feasible to rotate pedicled vascularized bone graft (VBG) from L1 to S1 via a posterior approach. VBG has been used to successfully augment fusion rates in various skeletal pathologies. Pedicled VBG has numerous advantages over free-transfer VBG, including the maintenance of a robust vascular supply to the graft without the need for vascular anastomoses. Pedicled VBG options have not been well described for posterior lumbosacral fusion. METHODS A multidisciplinary team of plastic surgeons and neurosurgeons hypothesized that it is feasible to rotate pedicled VBG from L1 to S1 via a posterior approach. In six cadavers, two VBG donor sites were evaluated: posterior element (PE-VBG) and iliac crest (IC-VBG). A single case report of a patient with lumbar Charcot joint treated with IC-VBG is also presented. RESULTS For the PE-VBG, the laminae and spinous processes were mobilized en bloc via Gill laminectomy on a unilateral sacrospinalis pedicle. Mean ± standard deviation (SD) length × width graft dimensions were 2.8±0.48 cm × 2.2±0.81 cm. The inter-transverse process (inter-TP) distance was less than the corresponding lamina length at all levels. For the IC-VBG, iliac crest was mobilized on a quadratus lumborum pedicle. Mean±SD length × width × thickness graft dimensions were 7.7±1.28 cm × 2.2±0.69 cm × 1.5±0.79 cm. The IC-VBGs reached from L1 (T12-S1) to S1 (S1-S3), and all IC-VBGs were able to cover three levels. CONCLUSIONS This feasibility cadaveric study and the case report are the first demonstrations that pedicled VBGs can be successfully applied to posterior lumbosacral spinal arthrodesis. Patients at high risk for nonunion may benefit from these strategies. Further clinical experience with these techniques is warranted. LEVEL OF EVIDENCE Level IV.STUDY DESIGN Cadaveric feasibility study and case report. OBJECTIVE To determine if it is feasible to rotate pedicled vascularized bone graft (VBG) from L1 to S1 via a posterior approach. SUMMARY OF BACKGROUND DATA VBG has been used to successfully augment fusion rates in various skeletal pathologies. Pedicled VBG has numerous advantages over free-transfer VBG, including the maintenance of a robust vascular supply to the graft without the need for vascular anastomoses. Pedicled VBG options have not been well described for posterior lumbosacral fusion. METHODS A multidisciplinary team of plastic surgeons and neurosurgeons hypothesized that it is feasible to rotate pedicled VBG from L1 to S1 via a posterior approach. In six cadavers, two VBG donor sites were evaluated: posterior element (PE-VBG) and iliac crest (IC-VBG). A single case report of a patient with lumbar Charcot joint treated with IC-VBG is also presented. RESULTS For the PE-VBG, the laminae and spinous processes were mobilized en bloc via Gill laminectomy on a unilateral sacrospinalis pedicle. Mean ± standard deviation (SD) length × width graft dimensions were 2.8±0.48 cm × 2.2±0.81 cm. The inter-transverse process (inter-TP) distance was less than the corresponding lamina length at all levels. For the IC-VBG, iliac crest was mobilized on a quadratus lumborum pedicle. Mean±SD length × width × thickness graft dimensions were 7.7±1.28 cm × 2.2±0.69 cm × 1.5±0.79 cm. The IC-VBGs reached from L1 (T12-S1) to S1 (S1-S3), and all IC-VBGs were able to cover three levels. CONCLUSIONS This feasibility cadaveric study and the case report are the first demonstrations that pedicled VBGs can be successfully applied to posterior lumbosacral spinal arthrodesis. Patients at high risk for nonunion may benefit from these strategies. Further clinical experience with these techniques is warranted. LEVEL OF EVIDENCE Level IV.

The Barrow Biomimetic Spine: Comparative Testing of a 3D-Printed L4-L5 Schwab Grade 2 Osteotomy Model to a Cadaveric Model

Introduction The Barrow Biomimetic Spine project is an ongoing effort to develop a three-dimensional (3D)-printed synthetic spine model with high anatomical and biomechanical fidelity to human tissue. The purpose of this study was to evaluate the biomechanical performance of an L4-L5 3D-printed synthetic spine model in a lordotic correction test after Schwab grade 2 osteotomies as compared to human cadaveric spines that have undergone the same osteotomies and lordotic correction. Methods Ten different L4-L5 synthetic spine models were 3D printed. Each print varied in either the material used for the soft tissue components, the infill density of the bony and soft tissue structures, the pre-correction disc height, or the model orientation on the print bed. Each print was instrumented with pedicle screws and underwent a Schwab grade 2 osteotomy. Changes in disc height measurements and end-plate angle were compared against cadaveric data acquired using the same study method. Results A simple linear correlation analysis demonstrated that for horizontally printed models using PolyFlex (Polymaker, New York, NY, USA)(models 1-3, 8, 10), the pre-correction posterior disc height and lordotic correction were moderately correlated (r = 0.56), but this correlation did not achieve statistical significance (P = 0.12). Regression analysis demonstrated a very strong correlation between lordotic correction and change in posterior disc height (r = 0.92, P < 0.001). Models printed either vertically (models 4-6) or with low bone density and high soft tissue density (model 10) appeared to perform the most similarly to the cadaveric tissue. Discussion The 3D-printed synthetic spine models demonstrated predictable and reliable performance in a lordotic correction test based on their respective material qualities and print densities. The print variables tested further demonstrated that this model is capable of achieving high biomechanical fidelity to cadaveric tissue when subjected to the same lordotic correction test after Schwab grade 2 osteotomies.

Pedicled Vascularized Bone Grafts for Posterior Occipitocervical and Cervicothoracic Fusion: A Cadaveric Feasibility Study

BACKGROUND Arthrodesis is critical for achieving favorable outcomes in reconstructive spine surgery. Vascularized bone grafts (VBGs) have been successfully used to augment fusion rates in a variety of skeletal pathologies, and pedicled VBG has numerous advantages over free transfer VBG. Pedicled VBG has not previously been described for the posterior occipitocervicothoracic spine. OBJECTIVE To identify, describe, and assess potential donor sites for pedicled VBGs from occiput to T12 using a cadaver model and to describe important technical considerations for graft harvest and placement. METHODS A multidisciplinary team of plastic surgeons and neurosurgeons hypothesized that it is feasible to rotate a pedicled VBG from the occiput to T12 via a posterior approach. In 6 cadavers, 3 VBG donor sites were identified as anatomically feasible: occiput, scapula, and rib. RESULTS Split- and full-thickness occipital VBGs were mobilized on a semispinalis pedicle. Occipital VBGs could be mobilized from occiput to T1 and span up to 4 levels. Scapular VBGs were mobilized on a subscapular pedicle and could be mobilized from occiput to T7 and span up to 8 levels. Rib VBGs were mobilized on subcostal pedicles and could be mobilized from C6 to T12. Ribs T2 to T4 and T11 and T12 could cover 2 levels, and ribs T5 to T10 could cover 3 levels. The first rib was anatomically unsuitable as a VBG due to its primarily ventral course. CONCLUSION Pedicled VBGs can feasibly be applied to posterior spinal arthrodesis from occiput to T12. Patients at high risk for nonunion may benefit from this strategy.