Innovative growth and development of a neurological surgery residency cadaveric spine-simulation training program: a single-institution experience.

OBJECTIVE: Cadaveric and dry 3D model-based simulation training is a valuable educational tool for neurosurgical residents. Such simulation training is an opportunity for residents to hone technical skills and decision-making and enhance their neuroanatomy knowledge. The authors describe the growth and development of the Oregon Health & Science University Department of Neurological Surgery resident-focused, hands-on, spine-simulation surgery courses and provide details of course evaluations, layout, and setup. METHODS: A four-part spine surgical simulation series, including two human cadaveric and two dry 3D model-based courses, was created to provide resident spine procedure training. Residents participated in the spine simulation series (2017-2021) and completed annual course curriculum and anonymous post-course evaluations. Evaluations included both Likert scale items and free-text responses. Responses to Likert scale items were analyzed in Python. Free-text responses were quantified using the Valence Aware Dictionary for Sentiment Reasoner. Descriptive statistics were calculated and plotted using Python's seaborn and matplotlib library modules. RESULTS: The analysis included 129 spine (occipitocervical, thoracolumbar, and spine model fusion I and II) simulation course evaluations. Likert responses demonstrated high average responses for evaluation questions (4.67 ± 0.90 and above). The average compound sentiment value was 0.58 ± 0.28. CONCLUSIONS: This is the first time Likert responses and sentiment analysis have been used to demonstrate how neurosurgical residents positively value a hands-on spine simulation training. Simulation is an essential component of neurosurgical resident education training. The authors encourage other neurosurgical education programs to develop and leverage spine simulation as a teaching tool.

Anterior Cervical Arthrodesis With Polyetheretherketone Spacers: What is the Role of the Grafting Material?

STUDY DESIGN: This was a retrospective study of 2 surgeons' use of a single polyetheretherketone (PEEK) device. OBJECTIVE: Our objective was to investigate the fusion adjunct placed within PEEK devices to examine the likelihood of an arthrodesis, regardless of the PEEK interbody device itself. SUMMARY OF BACKGROUND DATA: The effectiveness of PEEK interbody devices in anterior cervical arthrodesis has been questioned. METHODS: The authors retrospectively reviewed the results of 121 patients with demineralized bone matrix (DBM) and 96 with local autograft bone placed within identical PEEK devices for anterior cervical arthrodesis (from 2011 to 2018); 1 surgeon used DBM and another local autograft bone. Arthrodesis was determined independently by a surgeon and 2 blinded neuroradiologists. RESULTS: For DBM versus autograft; mean age was 60 versus 61 years, smoking status 42.1% versus 31%, diabetes mellitus 18.2% versus 28%, mean body mass index 31 versus 30, and follow up averaged 17 months in both groups. For DBM versus autograft; a radiographic arthrodesis was observed in 22.3% versus 76% of patients. Refusion at the index level was required in 5.8% of the DBM and 0% of the autograft patients. CONCLUSIONS: A PEEK interbody device filled with local autograft resulted in a higher radiographic fusion rate and a lower need for reoperation at the index level than an identical device filled with DBM. Caution is warranted in assigning fusion failure to the PEEK device alone in anterior cervical discectomy and fusion surgery.

PEEK interbody devices for multilevel anterior cervical discectomy and fusion: association with more than 6-fold higher rates of pseudarthrosis compared to structural allograft.

OBJECTIVE: Common interbody graft options for anterior cervical discectomy and fusion (ACDF) include allograft and polyetheretherketone (PEEK). PEEK has gained popularity due to its radiolucent properties and a modulus of elasticity similar to that of bone. PEEK devices also result in higher billing costs than allograft, which may drive selection. A previous study found a 5-fold higher rate of pseudarthrosis with the use of PEEK devices compared with structural allograft in single-level ACDF. Here the authors report on the occurrence of pseudarthrosis with PEEK devices versus structural allograft in patients who underwent multilevel ACDF. METHODS: The authors retrospectively reviewed 81 consecutive patients who underwent a multilevel ACDF and had radiographic follow-up for at least 1 year. Data were collected on age, sex, BMI, tobacco use, pseudarthrosis, and rate of reoperation for pseudarthrosis. Logistic regression was used for data analysis. RESULTS: Of 81 patients, 35 had PEEK implants and 46 had structural allograft. There were no significant differences between age, sex, smoking status, or BMI in the 2 groups. There were 26/35 (74%) patients with PEEK implants who demonstrated radiographic evidence of pseudarthrosis, compared with 5/46 (11%) patients with structural allograft (p < 0.001, OR 22.2). Five patients (14%) with PEEK implants required reoperation for pseudarthrosis, compared with 0 patients with allograft (p = 0.013). CONCLUSIONS: This study reinforces previous findings on 1-level ACDF outcomes and suggests that the use of PEEK in multilevel ACDF results in statistically significantly higher rates of radiographic pseudarthrosis and need for revision surgery than allograft. Surgeons should consider these findings when determining graft options, and reimbursement policies should reflect these discrepancies.

Intraoperative neuromonitoring for one-level lumbar discectomies is low yield and cost-ineffective.

BACKGROUND: Intraoperative neuromonitoring is a common, well-established modality used in spine surgery to prevent intraoperative neural injury. Neuromonitoring use in lumbar discectomy, however, is based on surgeon preference, without evidence-based data. The purpose of this research was to determine intraoperative utility and overall cost effectiveness of neuromonitoring for lumbar discectomy. METHODS: We retrospectively reviewed adult patients who underwent a lumbar discectomy, with at least 1 month of follow-up at a single tertiary care center. Patient age, sex, body mass index (BMI), lumbar level operated, and operative time and cost were collected. Neuromonitoring and operative reports were reviewed for any electromyography (EMG) abnormalities noted intraoperatively, pre- and post-operative motor exam and post-operative pain relief were collected. RESULTS: Ninety-one (47 with and 44 without neuromonitoring) lumbar discectomy cases were reviewed. There was no significant difference between mean age, sex, and BMI between the two groups. There was a significant (p = 0.006) increase in operating room time (174 min; with vs. 144 min; without neuromonitoring). Neuromonitoring was associated with a significant (p = 0.006) overall operative cost ($21,949; with vs. $18,064; without). Of the 47 cases with neuromonitoring; one had abnormal intraoperative EMG activity, which returned to normal by case conclusion. No patient in either group demonstrated new post-operative motor weakness. There was no difference in the number of patients who endorsed post-operative pain relief between the two groups. CONCLUSIONS: Neuromonitoring for lumbar discectomy confers greater operative time and cost, without any difference in neurological outcome.

Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion.

In BriefThe authors examined fusion rates after single-level anterior cervical discectomy and fusion, comparing use of a structural allograft with use of polyetheretherketone (PEEK) interbody devices packed with bone graft. The results demonstrate superior results of structural allograft in terms of arthrodesis rates and reoperation rates. Currently, reimbursement rates substantially favor the use of PEEK and other synthetic devices, which the authors believe should be changed based on the results of this study.

Longitudinal relaxographic imaging of white matter hyperintensities in the elderly.

BACKGROUND: Incidental white matter hyperintensities (WMHs) are common findings on T2-weighted magnetic resonance images of the aged brain and have been associated with cognitive decline. While a variety of pathogenic mechanisms have been proposed, the origin of WMHs and the extent to which lesions in the deep and periventricular white matter reflect distinct etiologies remains unclear. Our aim was to quantify the fractional blood volume (vb) of small WMHs in vivo using a novel magnetic resonance imaging (MRI) approach and examine the contribution of blood-brain barrier disturbances to WMH formation in the deep and periventricular white matter. METHODS: Twenty-three elderly volunteers (aged 59-82 years) underwent 7 Tesla relaxographic imaging and fluid-attenuated inversion recovery (FLAIR) MRI. Maps of longitudinal relaxation rate constant (R1) were prepared before contrast reagent (CR) injection and throughout CR washout. Voxelwise estimates of vb were determined by fitting temporal changes in R1 values to a two-site model that incorporates the effects of transendothelial water exchange. Average vb values in deep and periventricular WMHs were determined after semi-automated segmentation of FLAIR images. Ventricular permeability was estimated from the change in CSF R1 values during CR washout. RESULTS: In the absence of CR, the total water fraction in both deep and periventricular WMHs was increased compared to normal appearing white matter (NAWM). The vb of deep WMHs was 1.8 ± 0.6 mL/100 g and was significantly reduced compared to NAWM (2.4 ± 0.8 mL/100 g). In contrast, the vb of periventricular WMHs was unchanged compared to NAWM, decreased with ventricular volume and showed a positive association with ventricular permeability. CONCLUSIONS: Hyperintensities in the deep WM appear to be driven by vascular compromise, while those in the periventricular WM are most likely the result of a compromised ependyma in which the small vessels remain relatively intact. These findings support varying contributions of blood-brain barrier and brain-CSF interface disturbances in the pathophysiology of deep and periventricular WMHs in the aged human brain.

Structure-function studies of blood and air capillaries in chicken lung using 3D electron microscopy.

Avian pulmonary capillaries differ from those of mammals in three important ways. The blood-gas barrier is much thinner, it is more uniform in thickness, and the capillaries are far more rigid when their transmural pressure is altered. The thinness of the barrier is surprising because it predisposes the capillaries to stress failure. A possible mechanism for these differences is that avian pulmonary capillaries, unlike mammalian, are supported from the outside by air capillaries, but the details of the support are poorly understood. To clarify this we studied the blood and air capillaries in chicken lung using transmission electron microscopy (EM) and two relatively new techniques that allow 3D visualization: electron tomography and serial block-face scanning EM. These studies show that the pulmonary capillaries are flanked by epithelial bridges composed of two extremely thin epithelial cells with large surface areas. The junctions of the bridges with the capillary walls show thickening of the epithelial cells and an accumulation of extracellular matrix. Collapse of the pulmonary capillaries when the pressure outside them is increased is apparently prevented by the guy wire-like action of the epithelial bridges. The enlarged junctions between the bridges and the walls could provide a mechanism that limits the hoop stress in the capillary walls when the pressure inside them is increased. The support of the pulmonary capillaries may also be explained by an interdependence mechanism whereby the capillaries are linked to a rigid assemblage of air capillaries. These EM studies show the supporting structures in greater detail than has previously been possible, particularly in 3D, and they allow a more complete analysis of the mechanical forces affecting avian pulmonary capillaries.