The FDA Reclassification of Cervical Pedicle and Lateral Mass Screws: A Case Study in Regulatory History

The classification of medical devices by the Food and Drug Administration (FDA) involves rigorous scrutiny from specialized panels that designate devices as Class I, II, or III depending on their levels of relative risk to patient health. Posterior rigid pedicle screw systems were first classified by the FDA in 1984 and have since revolutionized the treatment of many spine pathologies. Despite this early classification by the FDA, posterior cervical pedicle and lateral mass screws were not reclassified from unclassified to Class III and then to Class II until 2019, nearly 35 years after their initial classification. This reclassification process involved a decades-long interplay between the FDA, formal panels, manufacturers, academic leaders, practicing physicians, and patients. It was delayed by lawsuits and a paucity of data demonstrating the ability to improve outcomes for cervical spinal pathologies. The off-label use of thoracolumbar pedicle screw rigid fixation systems by early adopters assisted manufacturers and professional organizations in providing the necessary data for the reclassification process. This case study highlights the collaboration between physicians and professional organizations in facilitating FDA reclassification and underscores changes to the current classification process that could avoid the prolonged dichotomy between common medical practice and FDA guidelines.

The Accreditation Council for Graduate Medical Education 20-Year Trends in Diversity, Equity, and Inclusion in the United States: How Does Neurological Surgery Compare?

BACKGROUND

Within the current medical workforce, diversity is limited among surgical specialties. However, diversity allows physicians to provide culturally competent care. This paper discusses the trends in racial, ethnic, and gender representation within different surgical subspecialties with an emphasis on neurosurgery over a 20-year time frame.

METHODS

A retrospective review of data collected by the Accreditation Council for Graduate Medical Education over the past twenty years, as reported in Journal of the American Medical Association, was conducted. Residents from 5 surgical specialties were evaluated based on gender, race, and ethnic identifications from 2002 to 2022. One-way analysis of variance was performed to compare the levels and retention rates of racial, ethnic, and gender diversity within these specialties.

RESULTS

Analysis of resident demographics of the 5 surgical specialties reveals an overall trend of increasing diversity over the study period. Over the past 20 years, neurosurgery had an overall increase in Asian (+5.1%), Hispanic (+3.0%), and female (+11.4%) residents, with a decrease in White residents by 2.1% and Black residents by 1.1%. Among the surgical specialties analyzed, otolaryngology had the greatest overall increase in minority residents. Notably, there has been an overall increase in female residents across all 5 surgical specialties, with the highest in otolaryngology (+20.3%) which was significantly more than neurosurgery (P < 0.001).

CONCLUSIONS

This chronological analysis spanning 20 years demonstrates that neurosurgery, like other specialties, has seen a growth in several racial and ethnic categories. Relative differences are notable in neurosurgery, including Black, Asian, Hispanic, and White ethnic categories, with growth in females, but at a significantly lesser pace than seen in otolaryngology and plastic surgery.

Cross-hemicord spinal fiber reorganization associates with cortical sensory and motor network expansion in the rat model of hemicontusion cervical spinal cord injury

Magnetic resonance imaging plays an important role in characterizing microstructural changes and reorganization after traumatic injuries to the nervous system. In this study, we tested the feasibility of ex-vivo spinal cord diffusion tensor imaging (DTI) in combination with in vivo brain functional MRI to characterize spinal reorganization and its supraspinal association after a hemicontusion cervical spinal cord injury (SCI). DTI parameters (fractional anisotropy [FA], mean diffusion [MD]) and fiber orientation changes related to reorganization in the contused cervical spinal cord were compared to sham specimens. Altered fiber density and fiber directions occurred across the ipsilateral and contralateral hemicords but with only ipsilateral FA and MD changes. The hemicontusion SCI resulted in ipsilateral fiber breaks, voids and vivid fiber reorientations along the injury epicenter. Fiber directional changes below the injury level were primarily inter-hemispheric, indicating prominent below-level cross-hemispheric reorganization. In vivo resting state functional connectivity of the brain from the respective rats before obtaining the spinal cord samples indicated spatial expansion and increased connectivity strength across both the sensory and motor networks after SCI. The consistency of the neuroplastic changes along the neuraxis (both brain and spinal cord) at the single-subject level, indicates that distinctive reorganizational relationships exist between the spinal cord and the brain post-SCI.

Six-Year Follow-up of a Randomized Controlled Trial of i-FACTOR Peptide-Enhanced Bone Graft Versus Local Autograft in Single-Level Anterior Cervical Discectomy and Fusion

BACKGROUND

Previous analyses of the US Food and Drug Administration (FDA) Investigational Device Exemption study demonstrated the superiority of i-FACTOR compared with local autograft bone in single-level anterior cervical discectomy and fusion (ACDF) at 12 and 24 months postoperatively in a composite end point of overall success.

OBJECTIVE

To report the final, 6-year clinical and radiological outcomes of the FDA postapproval study.

METHODS

Of the original 319 subjects enrolled in the Investigational Device Exemption study, 220 participated in the postapproval study (106 i-FACTOR and 114 control).

RESULTS

The study met statistical noninferiority success for all 4 coprimary end points. Radiographic fusion was achieved in 99% (103/104) and 98.2% (109/111) in i-FACTOR and local autograft subjects, mean Neck Disability Index improvement from baseline was 28.6 (24.8, 32.3) in the i-FACTOR and 29.2 (25.6, 32.9) in the control group, respectively (noninferiority P < .0001). The neurological success rate at 6 years was 95.9% (70/73) in i-FACTOR subjects and 93.7% (70/75) in local autograft subjects (noninferiority P < .0001). Safety outcomes were similar between the 2 groups. Secondary surgery on the same or different cervical levels occurred in 20/106 (18.9%) i-FACTOR subjects and 23/114 (20.2%) local autograft subjects ( P = .866). Secondary outcomes (pain, SF-36 physical component score and mental component score) in i-FACTOR subjects were similar to those in local autograft subjects.

CONCLUSION

i-FACTOR met all 4 FDA-mandated noninferiority success criteria and demonstrated safety and efficacy in single-level anterior cervical discectomy and fusion for cervical radiculopathy through 6 years postoperatively. Safety outcomes are acceptable, and the clinical and functional outcomes observed at 12 and 24 months remained at 72 months.

Augmenting Career Longevity: An Analysis of Ergonomics Training Among 134 Neurological Surgeons

BACKGROUND

Work-related pain among neurosurgeons remains understudied, yet can have long-term consequences which affect operative efficiency and efficacy, career longevity, and life outside of work.

OBJECTIVE

This study provides insight into the extent of pain experienced by neurosurgeons and the effect of ergonomics training on pain.

METHODS

An online survey pertaining to ergonomics and pain was sent to all neurosurgeons on the Council of State Neurosurgical Societies (CSNS) email distribution list. Statistical comparisons of age groups against pain levels and ergonomics training against pain levels, as well as multivariate linear regression of demographics, training, and operating factors against pain levels were performed.

RESULTS

One hundred and thirty-four neurosurgeons responded to the survey. The mean average severity of pain across respondents was 3.3/10 and the mean peak severity of pain was 5.1/10. Among the reported peak pain severity scores, neurosurgeons with 21-30 years of operating experience had significantly higher pain scores than those with 11-20 years of experience (mean 6.2 vs. 4.2; P < 0.05), while neurosurgeons with more than 30 years of experience had significantly less pain than those with 21-30 years of experience (mean 4.4 vs. 6.2, P = 0.005). Training in ergonomics did not significantly improve respondents' reported peak or mean pain severities (17.9% reported having ergonomics training).

CONCLUSIONS

Ergonomics training did not appear to make a difference in neurosurgeons' pain severities. This may signify a need to optimize ergonomics pedagogy to achieve observable benefits.

Roles of neuronal toll-like receptors in neuropathic pain and central nervous system injuries and diseases

Toll-like receptors (TLRs) are innate immune receptors that are expressed in immune cells as well as glia and neurons of the central and peripheral nervous systems. They are best known for their role in the host defense in response to pathogens and for the induction of inflammation in infectious and non-infectious diseases. In the central nervous system (CNS), TLRs modulate glial and neuronal functions as well as innate immunity and neuroinflammation under physiological or pathophysiological conditions. The majority of the studies on TLRs in CNS pathologies investigated their overall contribution without focusing on a particular cell type, or they analyzed TLRs in glia and infiltrating immune cells in the context of neuroinflammation and cellular activation. The role of neuronal TLRs in CNS diseases and injuries has received little attention and remains underappreciated. The primary goal of this review is to summarize findings demonstrating the pivotal and unique roles of neuronal TLRs in neuropathic pain, Alzheimer's disease, Parkinson's disease and CNS injuries. We discuss how the current findings warrant future investigations to better define the specific contributions of neuronal TLRs to these pathologies. We underline the paucity of information regarding the role of neuronal TLRs in other neurodegenerative, demyelinating, and psychiatric diseases. We draw attention to the importance of broadening research on neuronal TLRs in view of emerging evidence demonstrating their distinctive functional properties.

The role of electrical stimulation for rehabilitation and regeneration after spinal cord injury

Electrical stimulation is used to elicit muscle contraction and can be utilized for neurorehabilitation following spinal cord injury when paired with voluntary motor training. This technology is now an important therapeutic intervention that results in improvement in motor function in patients with spinal cord injuries. The purpose of this review is to summarize the various forms of electrical stimulation technology that exist and their applications. Furthermore, this paper addresses the potential future of the technology.

Lumbar Spine Surgery and What We Lost in the Era of the Coronavirus Pandemic: A Survey of the Lumbar Spine Research Society

STUDY DESIGN

This was a survey of the surgeon members of the Lumbar Spine Research Society (LSRS).

OBJECTIVE

The purpose of this study was to assess trends in surgical practice and patient management involving elective and emergency surgery in the early months of the coronavirus pandemic.

SUMMARY OF BACKGROUND DATA

The novel coronavirus has radically disrupted medical care in the first half of 2020. Little data exists regarding the exact nature of its effect on spine care.

METHODS

A 53-question survey was sent to the surgeon members of the LSRS. Respondents were contacted via email 3 times over a 2-week period in late April. Questions concentrated on surgical and clinical practice patterns before and after the pandemic. Other data included elective surgical schedules and volumes, as well as which emergency cases were being performed. Surgeons were asked about the status of coronavirus disease 2019 (COVID-19) virus testing. Circumstances for performing surgical intervention on patients with and without testing as well as patients testing positive were explored.

RESULTS

A total of 43 completed surveys were returned of 174 sent to active surgeons in the LSRS (25%). Elective lumbar spine procedures decreased by 90% in the first 2 months of the pandemic, but emergency procedures did not change. Patients with "stable" lumbar disease had surgeries deferred indefinitely, even beyond 8 weeks if necessary. In-person outpatient visits became increasingly rare events, as telemedicine consultations accounted for 67% of all outpatient spine appointments. In total, 91% surgeons were under some type of confinement. Only 11% of surgeons tested for the coronavirus on all surgical patients.

CONCLUSIONS

Elective lumbar surgery was significantly decreased in the first few months of the coronavirus pandemic, and much of outpatient spine surgery was practiced via telemedicine. Despite these constraints, spine surgeons performed emergency surgery when indicated, even when the COVID-19 status of patients was unknown.

LEVEL OF EVIDENCE

Level IV.

An ACGME-based comparison of neurosurgical and orthopedic resident training in adult spine surgery via a case volume and hours-based analysis

OBJECTIVE

In a 2014 analysis of orthopedic and neurological surgical case logs published by the Accreditation Council for Graduate Medical Education (ACGME), it was reported that graduating neurosurgery residents performed more than twice the number of spinal procedures in their training compared with graduating orthopedic residents. There has, however, been no follow-up assessment of this trend. Moreover, whether this gap in case volume equates to a similar gap in procedural hours has remained unstudied. Given the association between surgical volume and outcomes, evaluating the status of this disparity has value. Here, the authors assess trends in case volume and procedural hours in adult spine surgery for graduating orthopedic and neurological surgery residents from 2014 to 2019.

METHODS

A retrospective analysis of ACGME case logs from 2014 to 2019 for graduating orthopedic and neurological surgery residents was conducted for adult spine surgeries. Case volume was converted to operative hours by using periprocedural times from the 2019 Medicare/Medicaid Physician Fee Schedule. Graduating residents' spinal cases and hours, averaged over the study period, were compared between the two specialties by using 2-tailed Welch's unequal variances t-tests (α = 0.05). Longitudinal trends in each metric were assessed by linear regression followed by cross-specialty comparisons via tests for equality of slopes.

RESULTS

From 2014 to 2019, graduating neurosurgical residents logged 6.8 times as many spinal cases as their orthopedic counterparts, accruing 431.6 (95% CI 406.49-456.61) and 63.8 (95% CI 57.08-70.56) cases (p < 0.001), respectively. Accordingly, graduating neurosurgical residents logged 6.1 times as many spinal procedural hours as orthopedic surgery residents, accruing 1020.7 (95% CI 964.70-1076.64) and 166.6 (95% CI 147.76-185.35) hours (p < 0.001), respectively. Over these 5 years, both fields saw a linear increase in graduating residents' adult spinal case volumes and procedural hours, and these growth rates were higher for neurosurgery (+16.2 cases/year vs +4.4 cases/year, p < 0.001; +36.4 hours/year vs +12.4 hours/year, p < 0.001).

CONCLUSIONS

Graduating neurosurgical residents accumulated substantially greater adult spinal case volumes and procedural hours than their orthopedic counterparts from 2014 to 2019. This disparity has been widened by a higher rate of growth in adult spinal cases among neurosurgery residents. Accordingly, targeted efforts to increase spinal exposure for orthopedic surgery residents-such as using cross-specialty collaboration-should be explored.

Two-Year Clinical and Radiological Outcomes in Patients With Diabetes Undergoing Single-Level Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Secondary analysis of data from the multicenter, randomized, parallel-controlled Food and Drug Administration (FDA) investigational device exemption study.

OBJECTIVE

Studies on outcomes following anterior cervical discectomy and fusion (ACDF) in individuals with diabetes are scarce. We compared 24-month radiological and clinical outcomes in individuals with and without diabetes undergoing single-level ACDF with either i-FACTOR or local autologous bone.

METHODS

Between 2006 and 2013, 319 individuals with single-level degenerative disc disease (DDD) and no previous fusion at the index level underwent ACDF. The presence of diabetes determined the 2 cohorts. Data collected included radiological fusion evaluation, neurological outcomes, Neck Disability Index (NDI), Visual Analog Scale (VAS) scores, and the 36-Item Short Form Survey Version 2 (SF-36v2) Physical and Mental component summary scores.

RESULTS

There were 35 individuals with diabetes (11.1%; average body mass index [BMI] = 32.99 kg/m²; SD = 5.72) and 284 without (average BMI = 28.32 kg/m²; SD = 5.67). The number of nondiabetic smokers was significantly higher than diabetic smokers: 73 (25.70%) and 3 (8.57%), respectively. Preoperative scores of NDI, VAS arm pain, and SF-36v2 were similar between the diabetic and nondiabetic participants at baseline; however, VAS neck pain differed significantly between the cohorts at baseline (P = .0089). Maximum improvement for NDI, VAS neck and arm pain, and SF-36v2 PCS and MCS scores was seen at 6 months in both cohorts and remained stable until 24 months.

CONCLUSIONS

ACDF is effective for cervical radiculopathy in patients with diabetes. Diabetes is not a contraindication for patients requiring single-level surgery for cervical DDD.

Effect of Ventral vs Dorsal Spinal Surgery on Patient-Reported Physical Functioning in Patients With Cervical Spondylotic Myelopathy: A Randomized Clinical Trial

IMPORTANCE

Cervical spondylotic myelopathy is the most common cause of spinal cord dysfunction worldwide. It remains unknown whether a ventral or dorsal surgical approach provides the best results.

OBJECTIVE

To determine whether a ventral surgical approach compared with a dorsal surgical approach for treatment of cervical spondylotic myelopathy improves patient-reported physical functioning at 1 year.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial of patients aged 45 to 80 years with multilevel cervical spondylotic myelopathy enrolled at 15 large North American hospitals from April 1, 2014, to March 30, 2018; final follow-up was April 15, 2020.

INTERVENTIONS

Patients were randomized to undergo ventral surgery (n = 63) or dorsal surgery (n = 100). Ventral surgery involved anterior cervical disk removal and instrumented fusion. Dorsal surgery involved laminectomy with instrumented fusion or open-door laminoplasty. Type of dorsal surgery (fusion or laminoplasty) was at surgeon's discretion.

MAIN OUTCOMES AND MEASURES

The primary outcome was 1-year change in the Short Form 36 physical component summary (SF-36 PCS) score (range, 0 [worst] to 100 [best]; minimum clinically important difference = 5). Secondary outcomes included 1-year change in modified Japanese Orthopaedic Association scale score, complications, work status, sagittal vertical axis, health resource utilization, and 1- and 2-year changes in the Neck Disability Index and the EuroQol 5 Dimensions score.

RESULTS

Among 163 patients who were randomized (mean age, 62 years; 80 [49%] women), 155 (95%) completed the trial at 1 year (80% at 2 years). All patients had surgery, but 5 patients did not receive their allocated surgery (ventral: n = 1; dorsal: n = 4). One-year SF-36 PCS mean improvement was not significantly different between ventral surgery (5.9 points) and dorsal surgery (6.2 points) (estimated mean difference, 0.3; 95% CI, -2.6 to 3.1; P = .86). Of 7 prespecified secondary outcomes, 6 showed no significant difference. Rates of complications in the ventral and dorsal surgery groups, respectively, were 48% vs 24% (difference, 24%; 95% CI, 8.7%-38.5%; P = .002) and included dysphagia (41% vs 0%), new neurological deficit (2% vs 9%), reoperations (6% vs 4%), and readmissions within 30 days (0% vs 7%).

CONCLUSIONS AND RELEVANCE

Among patients with cervical spondylotic myelopathy undergoing cervical spinal surgery, a ventral surgical approach did not significantly improve patient-reported physical functioning at 1 year compared with outcomes after a dorsal surgical approach.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02076113.

Is Youth Football Safe? An Analysis of Youth Football Head Impact Data

BACKGROUND

The issue of whether sports-related head trauma at the youth level can result in long-term sequelae that may negatively impact the participant has been widely debated.

OBJECTIVE

To investigate head impacts in the Summit Youth Football League equipped with helmets using the Riddell InSite impact monitoring system. The monitoring system allowed for analysis of the number of impacts and severity of impacts by player.

METHODS

Data were obtained for all 20 members of the youth football team. Impacts were recorded as "low," "medium," and "high" intensity.

RESULTS

All 20 players participated in all practices and games throughout the season. No player suffered a concussion throughout the entire season. There were 817 recorded impacts throughout the season. This was an average of 41 impacts per player over the course of the season and fewer than 4 impacts per player per week. Only one impact registered as "high."

CONCLUSION

We demonstrate that there are few head impacts over the course of an entire season at the middle school level. Guardian Caps, safe tackling techniques, and the age of participants may have contributed to the very low number of impacts recorded and the complete lack of injuries. This study only provides data demonstrating that youth football, when Guardian Caps and safe tackling techniques are enforced, does not appear to result in significant head impacts causing immediate head injuries. This study cannot comment on the safety of playing football at the collegiate or professional level.

Role of astroglial toll-like receptors (TLRs) in central nervous system infections, injury and neurodegenerative diseases

Central nervous system (CNS) innate immunity plays essential roles in infections, neurodegenerative diseases, and brain or spinal cord injuries. Astrocytes and microglia are the principal cells that mediate innate immunity in the CNS. Pattern recognition receptors (PRRs), expressed by astrocytes and microglia, sense pathogen-derived or endogenous ligands released by damaged cells and initiate the innate immune response. Toll-like receptors (TLRs) are a well-characterized family of PRRs. The contribution of microglial TLR signaling to CNS pathology has been extensively investigated. Even though astrocytes assume a wide variety of key functions, information about the role of astroglial TLRs in CNS disease and injuries is limited. Because astrocytes display heterogeneity and exhibit phenotypic plasticity depending on the effectors present in the local milieu, they can exert both detrimental and beneficial effects. TLRs are modulators of these paradoxical astroglial properties. The goal of the current review is to highlight the essential roles played by astroglial TLRs in CNS infections, injuries and diseases. We discuss the contribution of astroglial TLRs to host defense as well as the dissemination of viral and bacterial infections in the CNS. We examine the link between astroglial TLRs and the pathogenesis of neurodegenerative diseases and present evidence showing the pivotal influence of astroglial TLR signaling on sterile inflammation in CNS injury. Finally, we define the research questions and areas that warrant further investigations in the context of astrocytes, TLRs, and CNS dysfunction.

Chronicling the philanthropic arm of neurological surgery: a review of the growth and development of the Neurosurgery Research & Education Foundation

OBJECTIVE

The Neurosurgery Research & Education Foundation (NREF), previously known as the Research Foundation of the American Association of Neurological Surgeons (AANS), was established in 1980 to encourage and facilitate innovation through financial support to young neurosurgeons in the process of honing their competencies in neurosciences and neurological surgery. This article provides a historical overview of NREF, its mission, and charitable contributions and the ever-expanding avenues for neurosurgeons, neurosurgical residents and fellows, and medical students to supplement clinical training and to further neurosurgical research advances.

METHODS

Data were collected from the historical archives of the AANS and NREF website. Available data included tabulated revenue, geographic and institutional records of funding, changes in funding for fellowships and awards, advertising methods, and sources of funding.

RESULTS

Since 1984, NREF has invested more than $23 million into the future of neurosurgery. To date, NREF has provided more than 500 fellowship opportunities which have funded neurosurgeons' education and research efforts at all stages of training and practice.

CONCLUSIONS

NREF is designed to serve as the vehicle through which the neurosurgical community fosters the continued excellence in the care of patients with neurosurgical diseases.

Astroglial TLR9 antagonism promotes chemotaxis and alternative activation of macrophages via modulation of astrocyte-derived signals: implications for spinal cord injury

BACKGROUND

The recruitment of immune system cells into the central nervous system (CNS) has a profound effect on the outcomes of injury and disease. Glia-derived chemoattractants, including chemokines, play a pivotal role in this process. In addition, cytokines and chemokines influence the phenotype of infiltrating immune cells. Depending on the stimuli present in the local milieu, infiltrating macrophages acquire the classically activated M1 or alternatively activated M2 phenotypes. The polarization of macrophages into detrimental M1 versus beneficial M2 phenotypes significantly influences CNS pathophysiology. Earlier studies indicated that a toll-like receptor 9 (TLR9) antagonist modulates astrocyte-derived cytokine and chemokine release. However, it is not known whether these molecular changes affect astrocyte-induced chemotaxis and polarization of macrophages. The present studies were undertaken to address these issues.

METHODS

The chemotaxis and polarization of mouse peritoneal macrophages by spinal cord astrocytes were evaluated in a Transwell co-culture system. Arrays and ELISA were utilized to quantify chemokines in the conditioned medium (CM) of pure astrocyte cultures. Immunostaining for M1- and M2-specific markers characterized the macrophage phenotype. The percentage of M2 macrophages at the glial scar was determined by stereological approaches in mice sustaining a mid-thoracic spinal cord contusion injury (SCI) and intrathecally treated with oligodeoxynucleotide 2088 (ODN 2088), the TLR9 antagonist. Statistical analyses used two-tailed independent-sample t-test and one-way analysis of variance (ANOVA) followed by Tukey's post hoc test. A p value < 0.05 was considered to be statistically significant.

RESULTS

ODN 2088-treated astrocytes significantly increased the chemotaxis of peritoneal macrophages via release of chemokine (C-C motif) ligand 1 (CCL1). Vehicle-treated astrocytes polarized macrophages into the M2 phenotype and ODN 2088-treated astrocytes promoted further M2 polarization. Reduced CCL2 and CCL9 release by astrocytes in response to ODN 2088 facilitated the acquisition of the M2 phenotype, suggesting that CCL2 and CCL9 are negative regulators of M2 polarization. The percentage of M2 macrophages at the glial scar was higher in mice sustaining a SCI and receiving ODN 2088 treatment as compared to vehicle-treated injured controls.

CONCLUSIONS

TLR9 antagonism could create a favorable environment during SCI by supporting M2 macrophage polarization and chemotaxis via modulation of astrocyte-to-macrophage signals.

Kinematics Following 3-Screw Integrated Interbody Spacers in the Lumbar Spine

BACKGROUND

"Stand-alone" fusion implants attempt to alleviate the need for supplemental posterior instrumentation.

OBJECTIVE

A biomechanical study was conducted to assess the stability of an integrated 3- screw interbody cage with, and without, supplemental posterior fixation.

METHODS

Nondestructive biomechanical testing was performed on 19 healthy cadaver spine segments. Specimens were tested in 6 degrees of motion and a maximum pure bending moment of 10 Nm was applied. Specimens were evaluated in the following sequence: Intact, cage, cage ± facet bolts, and cage ± pedicle screws. Nonconstrained motion was measured at both the index and adjacent levels.

RESULTS

The index levels were L2-L3 and L5-S1. The cage alone provided a significant decrease in motion at the L2-L3 level but not at L5-S1. At L2-L3, cage + pedicle screws decreased motion more effectively than cage + facet bolts, however, both the supplemented constructs outperformed intact (P < .05). At L5-S1, both posterior fixation systems appeared to have smaller degree of displacement compared to intact; however, no significant differences were observed at L5-S1 among the various constructs. Furthermore, the adjacent segments for each level (L1-L2 and L4-L5) had no significantly increased motion, compared to intact, for all 6 degrees of motion tested.

CONCLUSION

The stand-alone cage was more effective at L2-L3, than at L5-S1, in limiting motion. At L5-S1, supplemental fixation may need to be considered. No abnormal motion was identified at the adjacent, normal segments, for the stand-alone, or the circumferential constructs at either level tested.

Posterior foraminotomy versus anterior decompression and fusion in patients with cervical degenerative disc disease with radiculopathy: up to 5 years of outcome from the national Swedish Spine Register

OBJECTIVE

The long-term efficacy of posterior foraminotomy compared with anterior cervical decompression and fusion (ACDF) for the treatment of degenerative disc disease with radiculopathy has not been previously investigated in a population-based cohort.

METHODS

All patients in the national Swedish Spine Register (Swespine) from January 1, 2006, until November 15, 2017, with cervical degenerative disc disease and radiculopathy were assessed. Using propensity score matching, patients treated with posterior foraminotomy were compared with those undergoing ACDF. The primary outcome measure was the Neck Disability Index (NDI), a patient-reported outcome score ranging from 0% to 100%, with higher scores indicating greater disability. A minimal clinically important difference was defined as > 15%. Secondary outcomes were assessed with additional patient-reported outcome measures (PROMs).

RESULTS

A total of 4368 patients (2136/2232 women/men) met the inclusion criteria. Posterior foraminotomy was performed in 647 patients, and 3721 patients underwent ACDF. After meticulous propensity score matching, 570 patients with a mean age of 54 years remained in each group. Both groups had substantial decreases in their NDI scores; however, after 5 years, the difference was not significant (2.3%, 95% CI -4.1% to 8.4%; p = 0.48) between the groups. There were no significant differences between the groups in EQ-5D or visual analog scale (VAS) for neck and arm scores. The secondary surgeries on the index level due to restenosis were more frequent in the foraminotomy group (6/100 patients vs 1/100), but on the adjacent segments there was no difference between groups (2/100).

CONCLUSIONS

In patients with cervical degenerative disc disease and radiculopathy, both groups demonstrated clinical improvements at the 5-year follow-up that were comparable and did not achieve a clinically important difference from one another, even though the reoperation rate favored the ACDF group. This study design obtains population-based results, which are generalizable.

Pathological pain processing in mouse models of multiple sclerosis and spinal cord injury: contribution of plasma membrane calcium ATPase 2 (PMCA2)

Background

Neuropathic pain is often observed in individuals with multiple sclerosis (MS) and spinal cord injury (SCI) and is not adequately alleviated by current pharmacotherapies. A better understanding of underlying mechanisms could facilitate the discovery of novel targets for therapeutic interventions. We previously reported that decreased plasma membrane calcium ATPase 2 (PMCA2) expression in the dorsal horn (DH) of healthy PMCA2^+/− mice is paralleled by increased sensitivity to evoked nociceptive pain. These studies suggested that PMCA2, a calcium extrusion pump expressed in spinal cord neurons, plays a role in pain mechanisms. However, the contribution of PMCA2 to neuropathic pain processing remains undefined. The present studies investigated the role of PMCA2 in neuropathic pain processing in the DH of wild-type mice affected by experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and following SCI.

Methods

EAE was induced in female and male C57Bl/6N mice via inoculation with myelin oligodendrocyte glycoprotein fragment 35–55 (MOG_35–55) emulsified in Complete Freund’s Adjuvant (CFA). CFA-inoculated mice were used as controls. A severe SC contusion injury was induced at thoracic (T8) level in female C57Bl/6N mice. Pain was evaluated by the Hargreaves and von Frey filament tests. PMCA2 levels in the lumbar DH were analyzed by Western blotting. The effectors that decrease PMCA2 expression were identified in SC neuronal cultures.

Results

Increased pain in EAE and SCI was paralleled by a significant decrease in PMCA2 levels in the DH. In contrast, PMCA2 levels remained unaltered in the DH of mice with EAE that manifested motor deficits but not increased pain. Interleukin-1β (IL-1β), tumor necrosis factor α (TNFα), and IL-6 expression were robustly increased in the DH of mice with EAE manifesting pain, whereas these cytokines showed a modest increase or no change in mice with EAE in the absence of pain. Only IL-1β decreased PMCA2 levels in pure SC neuronal cultures through direct actions.

Conclusions

PMCA2 is a contributor to neuropathic pain mechanisms in the DH. A decrease in PMCA2 in DH neurons is paralleled by increased pain sensitivity, most likely through perturbations in calcium signaling. Interleukin-1β is one of the effectors that downregulates PMCA2 by acting directly on neurons.

Surgical Treatment With Thoracic Pedicle Screw Fixation of Vertebral Osteomyelitis With Long-Term Follow-up

BACKGROUND

While recent data has demonstrated the utility of lumbar pedicle screws for the treatment of vertebral osteomyelitis, the data are limited for thoracic pedicle screws.

OBJECTIVE

To investigate the effectiveness of thoracic pedicle screws for the surgical treatment of vertebral osteomyelitis.

METHODS

A retrospective review of all operations performed by 2 spinal neurosurgeons from 1999 to 2012 yielded 30 cases of vertebral osteomyelitis that were treated with thoracic pedicle screws. Sixteen (53%) of which underwent combined anterior and posterior fusion and 14 patients (47%) underwent standalone posterior fusion. Postoperative records were analyzed for pertinent clinical, laboratory, and radiographic data.

RESULTS

Of the 30 patients, 21 were males (70%), 8 were females (27%), and 1 was transsexual (3%). The mean age was 47 yr (range 18-69). The most common organism cultured was Staphylococcus aureus in 12 cases (50%). The mean patient stay in the hospital was 12.4 d after surgery (range 5-38 d). The mean antibiotic duration after discharge was 8 wk (range 1-24 wk). Of the 25 patients with long-term follow-up (mean, 49 mo), 92% had improved back pain (6/25 marked improvement, 17/25 complete resolution), 83% had improved muscle weakness (8/18 marked improvement, 7/18 complete resolution), and 100% had improved urinary incontinence (3/8 marked improvement, 5/8 complete resolution). Two patients (7%) required additional surgical revision due to instrumentation failure or wound infection.

CONCLUSION

This study demonstrates the efficacy of utilizing thoracic pedicle screws as a primary intervention to treat vertebral osteomyelitis.

i-Factor™ Bone Graft vs Autograft in Anterior Cervical Discectomy and Fusion: 2-Year Follow-up of the Randomized Single-Blinded Food and Drug Administration Investigational Device Exemption Study

BACKGROUND

i-Factor™ Bone Graft (Cerapedics Inc, Westminster, Colorado) is a composite bone substitute material consisting of P-15 synthetic collagen fragment adsorbed onto anorganic bone mineral suspended in an inert biocompatible hydrogel carrier. A pivotal, noninferiority, US FDA Investigational Device Exemption study demonstrated the benefits of i-Factor™ compared to local autograft bone in single-level anterior cervical discectomy and fusion at 1-yr postoperative.

OBJECTIVE

To report 2-yr follow-up.

METHODS

Subjects randomly received either autograft (n = 154) or i-Factor™ (n = 165) in a cortical ring allograft and followed using radiological, clinical, and patient-reported outcomes.

RESULTS

At 2 yr, the fusion rate was 97.30% and 94.44% in i-Factor™ and autograft subjects, respectively (P = .2513), and neurological success rate was 94.87% (i-Factor™) and 93.79% (autograft; P = .7869). Neck Disability Index improved 28.30 (i-Factor™) and 26.95 (autograft; P = .1448); Visual Analog Scale arm pain improved 5.43 (i-Factor™) and 4.97 (autograft) (p = .2763); Visual Analog Scale neck pain improved 4.78 (i-Factor™) and 4.41 (autograft; P = .1652), Short Form-36 (SF-36v2) Physical Component Score improved 10.23 (i-Factor™) and 10.18 (autograft; P = .4507), and SF36v2 Mental Component Score improved 7.88 (i-FactorTM) and 7.53 (autograft; P = .9872). The composite endpoint of overall success (fusion, Neck Disability Index improvement >15, neurological success, and absence of re-operations) was greater in i-Factor™ subjects compared to autograft subjects (69.83% and 56.35%, respectively, P = .0302). Twelve (7.45%) i-Factor™ subjects and 16 (10.53%) autograft subjects underwent re-operation (P = .3411). There were no allergic reactions associated with i-Factor™.

CONCLUSION

Use of i-Factor™ in anterior cervical discectomy and fusion is effective and safe, and results in similar outcomes compared to local autograft bone at 2 yr following surgery.

A link between plasma membrane calcium ATPase 2 (PMCA2), estrogen and estrogen receptor α signaling in mechanical pain

Earlier studies on genetically modified mice indicated that plasma membrane calcium ATPase 2 (PMCA2), a calcium extrusion pump, plays a novel and sex-dependent role in mechanical pain responses: female, but not male, PMCA2^+/− mice manifest increased mechanical pain compared to female PMCA2^+/+ mice. The goal of the present studies was to determine the contribution of ovarian steroids to the genotype- and sex-dependent manifestation of mechanical pain in PMCA2^+/+ versus PMCA2^+/− mice. Ovariectomy increased mechanical pain sensitivity and 17β-estradiol (E2) replacement restored it to basal levels in PMCA2^+/+ mice, but not in PMCA2^+/− littermates. Intrathecal administration of an estrogen receptor alpha (ERα) agonist induced ERα signaling in the dorsal horn (DH) of female PMCA2^+/+ mice, but was ineffective in PMCA2^+/− mice. In male PMCA2^+/+ and PMCA2^+/− mice, E2 treatment following orchidectomy did not recapitulate the genotype-dependent differential pain responses observed in females and the agonist did not elicit ERα signaling. These findings establish a novel, female-specific link between PMCA2, ERα and mechanical pain. It is postulated that PMCA2 is essential for adequate ERα signaling in the female DH and that impaired ERα signaling in the female PMCA2^+/− mice hinders the analgesic effects of E2 leading to increased sensitivity to mechanical stimuli.

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.

Cervical spondylotic myelopathy: A two decade experience

Context Cervical myelopathy occurs as a result of compression of the cervical spinal cord. Symptomatology includes, but is not limited to, pain, weakness, paresthesias, or gait/balance difficulties. Objective To present a two-decade experience with the management of cervical myelopathy. Methods Literature was reviewed to provide current guidelines for management as well as accompanying clinical presentations. Results Surgical decompression, if necessary, may be achieved from either an anterior, a posterior, or a combined anterior-posterior (AP) approach. The indications for each approach, as well as the surgical techniques, are described. Conclusion Several etiologies may lead to cord compression and cervical myelopathy. The best vector of approach with regard to anterior versus posterior surgical intervention is still under investigation. Regardless, management via surgical decompression has been demonstrated repeatedly to improve the CSM patients' quality of life.

A toll-like receptor 9 antagonist restores below-level glial glutamate transporter expression in the dorsal horn following spinal cord injury

Spinal cord (SC) trauma elicits pathological changes at the primary lesion and in regions distant from the injury epicenter. Therapeutic agents that target mechanisms at the injury site are likely to exert additional effects in these remote regions. We previously reported that a toll-like receptor 9 (TLR9) antagonist, oligodeoxynucleotide 2088 (ODN 2088), improves functional deficits and modulates the milieu at the epicenter in mice sustaining a mid-thoracic contusion. The present investigations use the same paradigm to assess ODN 2088-elicited alterations in the lumbar dorsal horn (LDH), a region remote from the injury site where SCI-induced molecular alterations have been well defined. We report that ODN 2088 counteracts the SCI-elicited decrease in glial glutamate aspartate transporter (GLAST) and glutamate transporter 1 (GLT1) levels, whereas the levels of the neuronal glutamate transporter excitatory amino acid carrier 1 (EAAC1) and astroglial GABA transporter 3 (GAT3) were unaffected. The restoration of GLAST and GLT1 was neither paralleled by a global effect on astrocyte and microglia activation nor by changes in the expression of cytokines and growth factors reported to regulate these transporters. We conclude that the effects of intrathecal ODN 2088 treatment extend to loci beyond the epicenter by selectively targeting glial glutamate transporters.

Novel Association Between Intrathecal Drug Administration and Arachnoiditis Ossificans

BACKGROUND

We present a case of delayed progression of adhesive arachnoiditis to arachnoiditis ossificans (AO) in a patient being treated with a high-dose polypharmaceutical intrathecal regimen.

CASE DESCRIPTION

The patient is a 39-year-old Caucasian male who was implanted with an intrathecal pump in 2006 to control severe low back pain and administered intrathecal pain medication for a period of 10 years. In 2016, he developed new-onset radicular pain and worsened sensation in his lower extremities. Computed tomography scan of the lumbar spine at that time demonstrated profound calcification of the arachnoid consistent with a diagnosis of AO. It was presumed that prolonged high-dose intrathecal medication precipitated this condition, and his intrathecal medications were titrated down with removal of the pump.

CONCLUSIONS

It is unlikely that his condition occurred as a result of prior surgery, with the more likely cause being hyperplasia of the spinal arachnoid, leading to scarring and calcification, due to the high-dose intrathecal regimen. This case highlights the delayed progression from stable arachnoiditis to AO concurring with a regimen of high-dose intrathecal medications. Clinicians should closely monitor patients undergoing intrathecal drug administration, particularly at elevated doses, for indications of damage to the spinal arachnoid mater.

Previously unreported complications associated with integrated cage screws following anterior lumbar interbody fusion: report of 2 cases

Anterior lumbar interbody fusion (ALIF) is a widely performed surgical treatment for various lumbar spine pathologies. The authors present the first reports of virtually identical cases of complications with integrated screws in stand-alone interbody cages. Two patients presented with the onset of S-1 radiculopathy due to screw misplacements following an ALIF procedure. In both cases, an integrated screw from the cage penetrated the dorsal aspect of the S-1 cortical margin of the vertebra, extended into the neural foramen, and injured the traversing left S-1 nerve roots. Advanced neuroimaging findings indicated nerve root impingement by the protruding screw tip. After substantial delays, radiculopathic symptoms were treated with removal of the offending instrumentation, aggressive posterior decompression of the bony and ligamentous structures, and posterolateral fusion surgery with pedicle screw fixation. Postoperative radiographic findings demonstrated decompression of the symptomatic nerve roots via removal of the extruded screw tips from the neural foramina.

Adjacent-segment disease after thoracic pedicle screw fixation

OBJECTIVE Pedicle screw fixation is a technique widely used to treat conditions ranging from spine deformity to fracture stabilization. Pedicle screws have been used traditionally in the lumbar spine; however, they are now being used with increasing frequency in the thoracic spine as a more favorable alternative to hooks, wires, or cables. Although safety concerns, such as the incidence of adjacent-segment disease (ASD) after cervical and lumbar fusions, have been reported, such issues in the thoracic spine have yet to be addressed thoroughly. Here, the authors review the literature on ASD after thoracic pedicle screw fixation and report their own experience specifically involving the use of pedicle screws in the thoracic spine. METHODS Select references from online databases, such as PubMed (provided by the US National Library of Medicine at the National Institutes of Health), were used to survey the literature concerning ASD after thoracic pedicle screw fixation. To include the authors' experience at Rutgers New Jersey Medical School, a retrospective review of a prospectively maintained database was performed to determine the incidence of complications over a 13-year period in 123 consecutive adult patients who underwent thoracic pedicle screw fixation. Children, pregnant or lactating women, and prisoners were excluded from the review. By comparing preoperative and postoperative radiographic images, the occurrence of thoracic ASD and disease within the surgical construct was determined. RESULTS Definitive radiographic fusion was detected in 115 (93.5%) patients. Seven incidences of instrumentation failure and 8 lucencies surrounding the screws were observed. One patient was observed to have ASD of the thoracic spine. The mean follow-up duration was 50 months. CONCLUSIONS This long-term radiographic evaluation revealed the use of pedicle screws for thoracic fixation to be an effective stabilization modality. In particular, ASD seems to be less of a problem in the relatively immobile thoracic spine than in the more mobile cervical and lumbar spines.

Elastic modulus in the selection of interbody implants

BACKGROUND

The modulus of elasticity of an assortment of materials used in spinal surgery, as well as cortical and cancellous bones, is determined by direct measurements and plotting of the appropriate curves. When utilized in spine surgery, the stiffness of a surgical implant can affect its material characteristics. The modulus of elasticity, or Young's modulus, measures the stiffness of a material by calculating the slope of the material's stress-strain curve. While many papers and presentations refer to the modulus of elasticity as a reason for the choice of a particular spinal implant, no peer-reviewed surgical journal article has previously been published where the Young's modulus values of interbody implants have been measured.

METHODS

Materials were tested under pure compression at the rate of 2 mm/min. A maximum of 45 kilonewtons (kN) compressive force was applied. Stress-strain characteristics under compressive force were plotted and this plot was used to calculate the elastic modulus.

RESULTS

The elastic modulus calculated for metals was more than 50 Gigapascals (GPa) and had significantly higher modulus values compared to poly-ether-ether-ketone (PEEK) materials and allograft bone.

CONCLUSIONS

The data generated in this paper may facilitate surgeons to make informed decisions on their choices of interbody implants with specific attention to the stiffness of the implant chosen.

Effects of early surgical decompression on functional and histological outcomes after severe experimental thoracic spinal cord injury

OBJECTIVE

In acute traumatic brain injury, decompressive craniectomy is a common treatment that involves the removal of bone from the cranium to relieve intracranial pressure. The present study investigated whether neurological function following a severe spinal cord injury improves after utilizing either a durotomy to decompress the intradural space and/or a duraplasty to maintain proper flow of cerebrospinal fluid.

METHODS

Sixty-four adult female rats (n = 64) were randomly assigned to receive either a 3- or 5-level decompressive laminectomy (Groups A and B), laminectomy + durotomy (Groups C and D), or laminectomy + duraplasty with graft (Group E and F) at 24 hours following a severe thoracic contusion injury (200 kilodynes). Duraplasty involved the use of DuraSeal, a hydrogel dural sealant. Uninjured and injured control groups were included (Groups G, H). Hindlimb locomotor function was assessed by open field locomotor testing (BBB) and CatWalk gait analysis at 35 days postinjury. Bladder function was analyzed and bladder wall thickness was assessed histologically. At 35 days postinjury, mechanical and thermal allodynia were assessed by the Von Frey hair filament and hotplate paw withdrawal tests, respectively. Thereafter, the spinal cords were dissected, examined for gross anomalies at the injury site, and harvested for histological analyses to assess lesion volumes and white matter sparing. ANOVA was used for statistical analyses.

RESULTS

There was no significant improvement in motor function recovery in any treatment groups compared with injured controls. CatWalk gait analysis indicated a significant decrease in interlimb coordination in Groups B, C, and D (p < 0.05) and swing speed in Groups A, B, and D. Increased mechanical pain sensitivity was observed in Groups A, C, and F (p < 0.05). Rats in Group C also developed thermal pain hypersensitivity. Examination of spinal cords demonstrated increased lesion volumes in Groups C and F and increased white matter sparing in Group E (p < 0.05). The return of bladder automaticity was similar in all groups. Examination of the injury site during tissue harvest revealed that, in some instances, expansion of the hydrogel dural sealant caused compression of the spinal cord.

CONCLUSIONS

Surgical decompression provided no benefit in terms of neurological improvement in the setting of a severe thoracic spinal cord contusion injury in rats at 24 hours postinjury. Decompressive laminectomy and durotomy did not improve motor function recovery, and rats in both of these treatment modalities developed neuropathic pain. Performing a durotomy also led to increased lesion volumes. Placement of DuraSeal was shown to cause compression in some rats in the duraplasty treatment groups. Decompressive duraplasty of 3 levels does not affect functional outcomes after injury but did increase white matter sparing. Decompressive duraplasty of 5 levels led to neuropathic pain development and increased lesion volumes. Further comparison of dural repair techniques is necessary.

Biomechanical Analysis of Range of Motion and Failure Characteristics of Osteoporotic Spinal Compression Fractures in Human Cadaver

BACKGROUND

Vertebroplasty is a treatment for osteoporotic vertebral compression fractures. The optimal location of needle placement for cement injection remains a topic of debate. As such, the authors assessed the effects of location of two types of cement instillations. In addition, the motion and failure modes at the index and adjacent segments were measured.

MATERIALS AND METHODS

Seven human osteoporotic cadaver spines (T1-L4), cut into four consecutive vertebral segments, were utilized. Of these, following the exclusion of four specimens not suitable to utilize for analysis, a total of 24 specimens were evaluable. Segments were randomly assigned into four treatment groups: unipedicular and bipedicular injections into the superior quartile or the anatomic center of the vertebra using confidence (Confidence Spinal Cement System^®, DePuy Spine, Raynham, MA, USA) or polymethyl methacrylate. The specimens were subjected to nondestructive pure moments of 5 Nm, in 2.5 Nm increments, using pulleys and weights to simulate six degrees of physiological motion. A follower preload of 200 N was applied in flexion extension. Testing sequence: range of motion (ROM) of intact specimen, fracture creation, cement injection, ROM after cement, and compression testing until failure. Nonconstrained motion was measured at the index and adjacent levels.

RESULTS

At the index level, no significant differences were observed in ROM in all treatment groups (P > 0.05). There was a significant increase in adjacent level motion only for the treatment group that received a unipedicular cement injection at the anatomic center.

CONCLUSION

The location of the needle (superior or central) and treatment type (unipedicular or bipedicular) had no significant effect on the ROM at the index site. At the adjacent levels, a significant increase occurred with therapy through a unipedicular approach into the centrum of the vertebra at the treated segment.

Impaired sensitivity to pain stimuli in plasma membrane calcium ATPase 2 (PMCA2) heterozygous mice: a possible modality- and sex-specific role for PMCA2 in nociception

Plasma membrane calcium ATPase 2 (PMCA2) is a calcium pump that plays important roles in neuronal function. Although it is expressed in pain-associated regions of the CNS, including in the dorsal horn (DH), its contribution to pain remains undefined. The present study assessed the role of PMCA2 in pain responsiveness and the link between PMCA2 and glutamate receptors, GABA receptors (GABARs), and glutamate transporters that have been implicated in pain processing in the DH of adult female and male PMCA2^+/+ and PMCA2^+/- mice. Behavioral assays evaluated mechanical and thermal pain responsiveness. Mechanical sensitivity was significantly increased by 52% and heat sensitivity was reduced by 29% in female, but not male, PMCA2^+/- mice compared with PMCA2^+/+ controls. There were female-specific changes in metabotropic glutamate receptor 1, NMDA receptor 2A, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit GluR1, GABA_BR1, and GABA_BR2 levels, whereas metabotropic glutamate receptor 5, NMDA receptor 2B, GluR2, and GABA_ARα2 levels were not altered. Glutamate aspartate transporter levels were higher and glial glutamate transporter 1 levels were lower in the DH of female, but not male, PMCA2^+/- mice. These findings indicate a novel role for PMCA2 in modality- and sex-dependent pain responsiveness. Female-specific molecular changes potentially account for the altered pain responses.-Khariv, V., Ni, L., Ratnayake, A., Sampath, S., Lutz, B. M., Tao, X.-X., Heary, R. F., Elkabes, S. Impaired sensitivity to pain stimuli in plasma membrane calcium ATPase 2 (PMCA2) heterozygous mice: a possible modality- and sex-specific role for PMCA2 in nociception.

Suitability of carbon fiber–reinforced polyetheretherketone cages for use as anterior struts following corpectomy

OBJECTIVE

Fibular allograft remains a widely used strut for corpectomy surgeries. The amount of graft material that can be packed into an allograft strut has not been quantified. Cages are an alternative to fibular allograft for fusion surgeries. The authors of this study assessed the suitability of carbon fiber–reinforced polyetheretherketone (CFRP) cages for anterior corpectomy surgeries. They further explored the parameters known to affect fusion rates in clinical practice.

METHODS

Six fibular allografts were tested at standard lengths. Three sets of carbon fiber cages (Bengal, DePuy Spine), each with a different footprint size but the same lengths, were tested. The allografts and cages were wrapped in adhesive, fluid-tight transparent barriers and filled with oil. The volume and weight of the oil instilled as well as the implant footprints were measured. The fibular allografts and cages were tested at 20-, 40-, and 50-mm lengths. Two investigators independently performed all measurements 5 times. Five CFRP cubes (1 × 1 × 1 cm) were tested under pure compression, and load versus displacement curves were plotted to determine the modulus of elasticity.

RESULTS

Significantly more oil fit in the CFRP cages than in the fibular allografts (p < 0.0001). The weight and volume of oil was 4–6 times greater in the cages. Interobserver (r = 0.991) and intraobserver (r = 0.993) reliability was excellent. The modulus of elasticity for CFRP was 16.44 ± 2.07 GPa.

CONCLUSIONS

Carbon fiber–reinforced polyetheretherketone cages can accommodate much more graft material than can fibular allografts. In clinical practice, the ability to deliver greater amounts of graft material following a corpectomy may improve fusion rates.

Toll like receptor 9 antagonism modulates spinal cord neuronal function and survival: Direct versus astrocyte-mediated mechanisms

Toll like receptors (TLRs) are expressed by cells of the immune system and mediate the host innate immune responses to pathogens. However, increasing evidence indicates that they are important contributors to central nervous system (CNS) function in health and in pathological conditions involving sterile inflammation. In agreement with this idea, we have previously shown that intrathecal administration of a TLR9 antagonist, cytidine-phosphate-guanosine oligodeoxynucleotide 2088 (CpG ODN 2088), ameliorates the outcomes of spinal cord injury (SCI). Although these earlier studies showed a marked effect of CpG ODN 2088 on inflammatory cells, the expression of TLR9 in spinal cord (SC) neurons and astrocytes suggested that the antagonist exerts additional effects through direct actions on these cells. The current study was undertaken to assess the direct effects of CpG ODN 2088 on SC neurons, astrocytes and astrocyte-neuron interactions, in vitro. We report, for the first time, that inhibition of TLR9 in cultured SC neurons alters their function and confers protection against kainic acid (KA)-induced excitotoxic death. Moreover, the TLR9 antagonist attenuated the KA-elicited endoplasmic reticulum (ER) stress response in neurons, in vitro. CpG ODN 2088 also reduced the transcript levels and release of chemokine (C-X-C) motif ligand 1 (CXCL1) and monocyte chemotactic protein 1 (MCP-1) by astrocytes and it diminished interleukin-6 (IL-6) release without affecting transcript levels in vitro. Conditioned medium (CM) of CpG ODN 2088-treated astroglial cultures decreased the viability of SC neurons compared to CM of vehicle-treated astrocytes. However, this toxicity was not observed when astrocytes were co-cultured with neurons. Although CpG ODN 2088 limited the survival-promoting effects of astroglia, it did not reduce neuronal viability compared to controls grown in the absence of astrocytes. We conclude that the TLR9 antagonist acts directly on both SC neurons and astrocytes. Neuronal TLR9 antagonism confers protection against excitotoxic death. It is likely that this neuroprotection is partly due to the attenuation of the ER stress response provoked by excitotoxicity. Although CpG ODN 2088 limits the supportive effects of astrocytes on neurons, it could potentially exert beneficial effects by decreasing the release of pro-inflammatory cytokines and chemokines by astroglia. These findings highlight the multiple roles of TLR9 in the SC and have implications for pathological conditions including SCI where excitotoxicity and neuroinflammation play a prominent role in neuronal degeneration.

Iatrogenic spondylolisthesis following laminectomy for degenerative lumbar stenosis: systematic review and current concepts

OBJECT Decompression without fusion for degenerative lumbar stenosis is an effective treatment for both the pain and disability of neurogenic claudication. Iatrogenic instability following decompression may require further intervention to stabilize the spine. The authors review the incidence of postsurgical instability following lumbar decompression, and assess the impact of surgical technique as well as study design on the incidence of instability. METHODS A comprehensive literature search was performed to identify surgical cohorts of patients with degenerative lumbar stenosis, with and without preexisting spondylolisthesis, who were treated with laminectomy or minimally invasive decompression without fusion. Data on patient characteristics, surgical indications and techniques, clinical and radiographic outcomes, and reoperation rates were collected and analyzed. RESULTS A systematic review of 24 studies involving 2496 patients was performed, assessing both open laminectomy and minimally invasive bilateral canal enlargement. Postoperative pain and functional outcomes were similar across the various studies, and postoperative radiographie instability was seen in 5.5% of patients. Instability was seen more frequently in patients with preexisting spondylolisthesis (12.6%) and in those treated with open laminectomy (12%). Reoperation for instability was required in 1.8% of all patients, and was higher for patients with preoperative spondylolisthesis (9.3%) and for those treated with open laminectomy (4.1%). CONCLUSIONS Instability following lumbar decompression is a common occurrence. This is particularly true if decompression alone is selected as a surgical approach in patients with established spondylolisthesis. This complication may occur less commonly with the use of minimally invasive techniques; however, larger prospective cohort studies are necessary to more thoroughly explore these findings.

Severe holocord syrinx in a child with megalencephaly-capillary malformation syndrome

The authors present the case of a child with megalencephaly-capillary malformation syndrome who developed a rapidly progressive holocord syringomyelia that was treated surgically. A 3-year-old boy with megalencephaly-capillary malformation-polymicrogyria (MCAP) syndrome presented with several months of right leg weakness, worsening scoliosis, and increased seizures. An MRI study of the brain demonstrated a Chiari I malformation and massively dilated syringomyelia extending from C-2 to the conus medullaris. The patient underwent an urgent suboccipital craniectomy with C1-3 laminectomies to relieve the CSF outflow obstruction with significant clinical improvement. Surgery was complicated by bleeding from intracranial vascular malformations. This report describes a very rapidly developing, massive holocord syringomyelia related to CSF obstruction due to an unusual congenital brain malformation and associated vascular overgrowth at the site. Serial, premorbid MRI studies demonstrated the very rapid progression from no Chiari malformation, to progressively greater cerebellar tonsillar herniation, to holocord syrinx. This complication has never been reported in MCAP syndrome and should be considered in any affected MCAP patient with a progressive neurological decline, even if previous spine imaging findings were normal. Surgical complications due to hemorrhage also need to be considered in this vascular brain malformation.

Defensive medicine in neurosurgery: the Canadian experience

OBJECT

Recent studies have examined the impact of perceived medicolegal risk and compared how this perception impacts defensive practices within the US. To date, there have been no published data on the practice of defensive medicine among neurosurgeons in Canada.

METHODS

An online survey containing 44 questions was sent to 170 Canadian neurosurgeons and used to measure Canadian neurosurgeons’ perception of liability risk and their practice of defensive medicine. The survey included questions on the following domains: surgeon demographics, patient characteristics, type of physician practice, surgeon liability profile, policy coverage, defensive behaviors, and perception of the liability environment. Survey responses were analyzed and summarized using counts and percentages.

RESULTS

A total of 75 neurosurgeons completed the survey, achieving an overall response rate of 44.1%. Over one-third (36.5%) of Canadian neurosurgeons paid less than $5000 for insurance annually. The majority (87%) of Canadian neurosurgeons felt confident with their insurance coverage, and 60% reported that they rarely felt the need to practice defensive medicine. The majority of the respondents reported that the perceived medicolegal risk environment has no bearing on their preferred practice location. Only 1 in 5 respondent Canadian neurosurgeons (21.8%) reported viewing patients as a potential lawsuit. Only 4.9% of respondents would have selected a different career based on current medicolegal risk factors, and only 4.1% view the cost of annual malpractice insurance as a major burden.

CONCLUSIONS

Canadian neurosurgeons perceive their medicolegal risk environment as more favorable and their patients as less likely to sue than their counterparts in the US do. Overall, Canadian neurosurgeons engage in fewer defensive medical behaviors than previously reported in the US.