Characterization of ion release from a novel biomaterial, Molybdenum-47.5Rhenium, in physiologic environments

BACKGROUND CONTEXT

Metals from spinal implants are released into surrounding tissues by various mechanisms. Metal ion release has been associated with clinical implant failure, osteolysis, and remote site accumulation with adverse events. Significant corrosion and associated metal ion release has been described with currently used spinal implant alloys. A novel metal alloy, Molybdenum-47.5Rhenium alloy (MoRe®), was approved for use in medical implants in 2019 by the FDA.

PURPOSE

To evaluate the metal ion release profile of MoRe alloy after immersion in both a stable physiologic, as well as in an inflammatory environment.

STUDY DESIGN

In vitro study.

METHODS

The ion release profile of the MoRe alloy was comprehensively evaluated in-vitro after prolonged immersion in physiologic and inflammatory environments. Ion concentration analyses were then conducted using inductively coupled plasma-mass spectrometry (ICP-MS) methods. Comparative testing of titanium (Ti-6Al-4V) and cobalt chromium (Co-28Cr-6Mo) was also performed.

RESULTS

Under baseline physiologic conditions, the MoRe alloy demonstrates very low molybdenum and rhenium ion release rates throughout the 30-day test period. During the first time interval (day 0-1), low levels of molybdenum and rhenium ions are detected (<0.3 μg/cm² day) followed by a rapid reduction in the ion release rates to <0.05 μg/cm² day during the second time interval (days 1-3) followed by a further reduction to very low steady-state rates <0.01 μg/cm² day during the third time interval (days 3-7), which were maintained through 30 days. In the inflammatory condition (H₂O₂ solution), there was a transient increase in the release of molybdenum and rhenium ions, followed by a return to baseline ion release rates (days 2-4), with a further reduction to low steady-state rates of ∼0.01 μg/cm² day (days 4-8). The measured molybdenum and rhenium ion release rates in both steady state (<0.01 μg/cm² day), and inflammatory environments (0.01 μg/cm² day) were far below the established FDA-permitted daily exposure (PDE) of 1,900 μg/cm² day for molybdenum and 4,400 μg/cm² day for rhenium. In contrast, titanium and cobalt chromium approached or exceeded their established PDE values in an inflammatory environment.

CONCLUSIONS

The novel biomaterial MoRe demonstrated a lower metal ion release profile in both a physiologic and inflammatory environment and was well below the established PDE.  Comparative testing of the cobalt-chromium and titanium alloys found higher levels of ion release in the inflammatory environment that exceeded the PDE for cobalt and vanadium.

Mild and Severe Obesity Reduce the Effectiveness of Lumbar Fusions: 1-Year Patient-Reported Outcomes in 8171 Patients

BACKGROUND

Elevated body mass index (BMI) is a well-known risk factor for surgical complications in lumbar surgery. However, its effect on surgical effectiveness independent of surgical complications is unclear.

OBJECTIVE

To determine increasing BMI's effect on functional outcomes following lumbar fusion surgery, independent of surgical complications.

METHODS

We retrospectively analyzed a prospectively built, patient-reported, quality of life registry representing 75 hospital systems. We evaluated 1- to 3-level elective lumbar fusions. Patients who experienced surgical complications were excluded. A stepwise multivariate regression model assessed factors independently associated with 1-yr Oswestry Disability Index (ODI), preop to 1-yr ODI change, and achievement of minimal clinically important difference (MCID).

RESULTS

A total of 8171 patients met inclusion criteria: 2435 with class I obesity (BMI 30-35 kg/m2), 1328 with class II (35-40 kg/m2), and 760 with class III (≥40 kg/m2). Increasing BMI was independently associated with worse 12-mo ODI (t = 8.005, P < .001) and decreased likelihood of achieving MCID (odds ratio [OR] = 0.977, P < .001). One year after surgery, mean ODI, ODI change, and percentage achieving MCID worsened with class I, class II, and class III vs nonobese cohorts (P < .001) in stepwise fashion.

CONCLUSION

Increasing BMI is associated with decreased effectiveness of 1- to 3-level elective lumbar fusion, despite absence of surgical complications. BMI ≥ 30 kg/m2 is, therefore, a risk factor for both surgical complication and reduced benefit from lumbar fusion.

Outpatient anterior cervical discectomy and fusion in the ambulatory surgery center setting: safety assessment for the Medicare population

OBJECTIVE

Several studies have demonstrated that anterior cervical discectomy and fusion (ACDF) surgery in the outpatient versus hospital setting provides improved efficiency, cost-effectiveness, and patient satisfaction without a compromise in safety or outcome. Recent anecdotal reports, however, have questioned whether outpatient ACDF surgery is safe in the > 65-year-old Medicare population. To date, no clinical study has assessed the safety of outpatient ACDF in an ambulatory surgery center (ASC), specifically in a Medicare population. The authors set out to analyze their 3-year experience with Medicare-enrolled patients undergoing ACDF surgery at a single ASC to determine its safety profile, perioperative care protocol, and associated outcomes.

METHODS

A retrospective analysis of 119 consecutive patients > 65 years (Medicare-eligible) who underwent 1-, 2-, or 3-level ACDF at a single ASC from 2015 to 2018 (since Medicare payment approval) was conducted. All patients were in American Society of Anesthesiologists classes I-III. Postoperatively, patients were observed for a minimum of 4 hours in a recovery setting for the following factors: neck swelling, neurological status, ability to swallow solid food, and urination capacity. All patients received a multimodal pain management regimen prior to discharge home. Data were collected on patient demographics, comorbidities, operative details, and all perioperative and 90-day morbidity.

RESULTS

Complete data were available for all 119 consecutive Medicare-eligible patients, 97 (81.5%) of whom were actively enrolled in Medicare. One-, 2-, and 3-level ACDFs were performed in 103 (86.6%), 15 (12.6%), and 1 (0.8%) patients, respectively. No patients required return to the operating room for intervention within the 4-hour postanesthesia care unit observation window. No patients required transfer from the ASC to the hospital setting for further observation or intervention. Thirty-day adverse events were reported in 2.4% of cases, all of which resolved by 90 days after surgery. The incidence of 90-day hospital readmission was 1.7% (n = 2), with 1 patient (0.8%) requiring reoperation at the index level for deep infection. All-cause 90-day mortality was 0%.

CONCLUSIONS

An analysis of consecutive Medicare patients (American Society of Anesthesiologists classes I-III) who underwent mostly 1-level and some 2-level ACDFs in an ASC setting demonstrates that surgical complications occur at a low rate with a safety profile similar to that reported for both inpatient ACDF and patients younger than 65 years. In an effort to reduce cost and improve efficiency of care, surgeons can safely perform ACDF in the Medicare population in an ASC environment utilizing patient selection criteria and perioperative management similar to those reported here.

Patient characteristics of smokers undergoing lumbar spine surgery: an analysis from the Quality Outcomes Database

OBJECTIVE

In this analysis the authors compare the characteristics of smokers to nonsmokers using demographic, socioeconomic, and comorbidity variables. They also investigate which of these characteristics are most strongly associated with smoking status. Finally, the authors investigate whether the association between known patient risk factors and disability outcome is differentially modified by patient smoking status for those who have undergone surgery for lumbar degeneration.

METHODS

A total of 7547 patients undergoing degenerative lumbar surgery were entered into a prospective multicenter registry (Quality Outcomes Database [QOD]). A retrospective analysis of the prospectively collected data was conducted. Patients were dichotomized as smokers (current smokers) and nonsmokers. Multivariable logistic regression analysis fitted for patient smoking status and subsequent measurement of variable importance was performed to identify the strongest patient characteristics associated with smoking status. Multivariable linear regression models fitted for 12-month Oswestry Disability Index (ODI) scores in subsets of smokers and nonsmokers was performed to investigate whether differential effects of risk factors by smoking status might be present.

RESULTS

In total, 18% (n = 1365) of patients were smokers and 82% (n = 6182) were nonsmokers. In a multivariable logistic regression analysis, the factors significantly associated with patients’ smoking status were sex (p < 0.0001), age (p < 0.0001), body mass index (p < 0.0001), educational status (p < 0.0001), insurance status (p < 0.001), and employment/occupation (p = 0.0024). Patients with diabetes had lowers odds of being a smoker (p = 0.0008), while patients with coronary artery disease had greater odds of being a smoker (p = 0.044). Patients’ propensity for smoking was also significantly associated with higher American Society of Anesthesiologists (ASA) class (p < 0.0001), anterior-alone surgical approach (p = 0.018), greater number of levels (p = 0.0246), decompression only (p = 0.0001), and higher baseline ODI score (p < 0.0001). In a multivariable proportional odds logistic regression model, the adjusted odds ratio of risk factors and direction of improvement in 12-month ODI scores remained similar between the subsets of smokers and nonsmokers.

CONCLUSIONS

Using a large, national, multiinstitutional registry, the authors described the profile of patients who undergo lumbar spine surgery and its association with their smoking status. Compared with nonsmokers, smokers were younger, male, nondiabetic, nonobese patients presenting with leg pain more so than back pain, with higher ASA classes, higher disability, less education, more likely to be unemployed, and with Medicaid/uninsured insurance status. Smoking status did not affect the association between these risk factors and 12-month ODI outcome, suggesting that interventions for modifiable risk factors are equally efficacious between smokers and nonsmokers.

Does Obesity Correlate With Worse Patient-Reported Outcomes Following Elective Anterior Cervical Discectomy and Fusion?

BACKGROUND

Studies have investigated the impact of obesity in thoracolumbar surgery; however, the effect of obesity on patient-reported outcomes (PROs) following anterior cervical discectomy and fusion (ACDF) is unknown.

OBJECTIVE

To examine the relationship between obesity and PROs following elective ACDF.

METHODS

Consecutive patients undergoing ACDF for degenerative conditions were evaluated. Patients were divided into groups with a body mass index ≥35. The EuroQol-5D, Short-Form 12 (SF-12), modified Japanese Orthopaedic Association score, and Neck Disability Index were used. Correlations between PROs and obesity were calculated at baseline and 1 year.

RESULTS

A total of 299 patients were included, with 80 obese (27%) and 219 nonobese (73%). patients At baseline, obesity was associated with worse myelopathy (modified Japanese Orthopaedic Association score: 10.7 vs 12.2, P = .01), general physical health (SF-12 physical component scale score: 28.7 vs 31.8, P = .02), and general mental health (SF-12 mental component scale score: 38.9 vs 42.3, P = .04). All PROs improved significantly following surgery in both groups. There was no difference in absolute scores and change scores for any PRO at 12 months following surgery. Furthermore, there was no difference in the percentage of patients achieving a minimal clinically important difference for the Neck Disability Index (52% vs 56%, P = .51) and no difference in patient satisfaction (85% vs 85%, P = .85) between groups.

CONCLUSION

Obesity was not associated with less improvement in PROs following ACDF. There was no difference in the proportion of patients satisfied with surgery and those achieving a minimal clinically important difference across all PROs. Obese patients may therefore achieve meaningful improvement following elective ACDF.

ABBREVIATIONS

ACDF, anterior cervical discectomy and fusionBMI, body mass indexEQ-5D, EuroQol-5DMCID, minimal clinically important differenceMCS, mental component scalemJOA, modified Japanese Orthopaedic AssociationNDI, Neck Disability IndexNRS, Numerical Rating ScalePCS, physical component scalePROs, patient-reported outcomesSF-12, Short Form 12.

The Burden of Spinal Disorders in the Elderly

Disorders of the spine are common and have a significant and measurable burden on affected patients and on our healthcare economy. The burden of spinal disorders encompasses metrics such as the prevalence of spinal disorders, the impact of spinal disorders on health-related quality of life, and the use of resources associated with the operative and nonoperative management of spinal disorders. Measurement of the burden of spinal disorders is important in prioritizing the distribution of limited resources within our healthcare economy. In 1998, the Priority Setting Committee of the Institute of Medicine concluded that in defining health priorities for research and funding, the burden of disease and impact on the health of the population should be the primary determinants of resource allocation. The purpose of this article is to report metrics comprising the burden of spinal disorders, with a focus on the significant and growing burden of spinal disorders in our elderly population, and to demonstrate that allocation of resources to the management of spinal disorders should be a priority for our healthcare economy.

Neurosurgery value and quality in the context of the Affordable Care Act: a policy perspective

Neurosurgeons provide direct individualized care to patients. However, the majority of regulations affecting the relative value of patient-related care are drafted by policy experts whose focus is typically system- and population-based. A central, prospectively gathered, national outcomes-related database serves as neurosurgery’s best opportunity to bring patient-centered outcomes to the policy arena.

In this study the authors analyze the impact of the Affordable Care Act (ACA) on the determination of quality and value in neurosurgery care through the scope, language, and terminology of policy experts. The methods by which the ACA came into law and the subsequent quality implications this legislation has for neurosurgery will be discussed. The necessity of neurosurgical patient-oriented clinical registries will be discussed in the context of imminent and dramatic reforms related to medical cost containment.

In the policy debate moving forward, the strength of neurosurgery’s argument will rest on data, unity, and proactiveness. The National Neurosurgery Quality and Outcomes Database (N2QOD) allows neurosurgeons to generate objective data on specialty-specific value and quality determinations; it allows neurosurgeons to bring the patient-physician interaction to the policy debate.

Reconstruction of skull base defects in sphenoid wing dysplasia associated with neurofibromatosis I with titanium mesh

Sphenoid wing dysplasia occurs in 3-7% of patients with neurofibromatosis type 1 (NF1). The typical radiological features are partial or complete absence of the greater wing of the sphenoid. This condition is slowly progressive and may result in temporal lobe herniation into the orbital cavity, producing pulsating exophthalmos and gross facial deformity. Thus, reconstruction of the orbit is important for both cosmetic and functional reasons. Traditional surgical treatment of sphenoid dysplasia involves split bone grafting and repair of the anterior skull base defect. However, several reports have demonstrated complications of graft resorption and recurrence of proptosis and pulsating exopthalmos. In this case series, we present two patients suffering from pulsating exophthalmos due to sphenoid dysplasia. Radiological and MRI studies demonstrated orbital enlargement and complete absence of the greater wing of the sphenoid. Surgical management of these patients involved dural defect repair, and the use of titanium mesh in conjunction with bone graft to act as a barrier between the orbit and the middle cranial fossa. The mesh was fixed by fine screws. Proptosis improved markedly post-operatively and resolved within a few weeks. Ocular pulsation subsided and remained quiescent with at least 1-year follow-up.

The use of expandable cages in patients undergoing multilevel corpectomies for metastatic tumors in the cervical spine

Expandable cages have been used successfully to reconstruct the anterior spinal column in the treatment of traumatic, neoplastic, infectious, and degenerative spine disease. To the best of our knowledge, no studies report the results of the use of expandable cages in patients undergoing multilevel corpectomies for cervical spine metastatic disease. We report our experience with the use of expandable cages in this subgroup of patients.From August 2006 to May 2008, 5 patients presenting with myelopathy, pain, and/or radiculopathy secondary to metastatic disease of the cervical spine underwent multilevel cervical corpectomies and placement of expandable cages in our institution. All procedures were supplemented with an anterior cervical plate and with posterior instrumentation to achieve a 360 degrees fusion. A visual analog scale (VAS), Nurick grade, Frankel grade, American Spinal Injuries Association (ASIA) grade, and Ranawat grade were used to evaluate patients pre- and postoperatively. The mean follow-up period was 13.2 months. Three patients underwent a 2-level corpectomy, 1 a 3-level corpectomy, and 1 a 4-level corpectomy. Postoperative imaging studies showed that all patients had correction of preoperative kyphosis. The mean VAS score was reduced from 6.4 to 1. All other indices of spinal cord injury measured improved postoperatively or were stabilized. Postoperative imaging studies showed stable constructs in 4 patients.The use of expandable cages in multilevel corpectomies for the treatment of metastatic cervical spine disease appears to be a safe and effective way to reconstruct the anterior column of the cervical spine, preventing further neurologic deterioration.

Intraventricular ganglioglioma: a short illustrated review

The following review of the literature describes the ganglioglioma, an uncommon mixed glioneuronal neoplasm, most often of low-grade histology, with a small, albeit well-documented, malignant potential. These tumors exhibit a strong epileptogenic propensity and most often present as new onset seizures or are discovered after a long history of refractory epilepsy. Despite their indolent course, the importance of gross total resection is well recognized to prevent anaplastic and malignant degeneration. Morphologically, the neoplasm is often cystic with an enhancing mural nodule, but can also be entirely solid. They are most often found in the temporal lobe but have been found throughout the neuraxis. An exceedingly rare location of the ganglioglioma is within the lateral ventricle. A systematic literature search revealed only eight reports documenting the occurrence of a ganglioglioma within the lateral ventricle. We describe an illustrative case of an intraventricular ganglioglioma with a prominent cystic component and enhancing mural nodule, which represents the classic radiographic appearance of gangliogliomas described in other locations. A superior parietal lobule approach offered excellent surgical access for tumor removal and the patient has remained free of neurological deficits following surgery. Regardless of location within the central nervous system, ganglioglioma should be on the differential diagnosis for any cystic mass with a mural nodule, particularly in the setting of epilepsy.

Surgical treatment of cervical spondylotic myelopathy with anterior compression: a review of 67 cases

Object

In patients with cervical spondylotic myelopathy (CSM), ventral disease and loss of cervical lordosis are considered to be relative indications for anterior surgery. However, anterior decompression and fusion operations may be associated with an increased risk of swallowing difficulty and an increased risk of nonunion when extensive decompression is performed. The authors reviewed cases involving patients with CSM treated via an anterior approach, paying special attention to neurological outcome, fusion rates, and complications.

Methods

Retrospectively, 67 cases involving consecutive patients with CSM requiring an anterior decompression were reviewed: 46 patients underwent anterior surgery only (1-to3-level anterior cervical discectomy and fusion [ACDF] or 1-level corpectomy), and 21 patients who required > 3-level ACDF or ≥ 2-level corpectomy underwent anterior surgery supplemented by a posterior instrumented fusion procedure.

Results

Postoperative improvement in Nurick grade was seen in 43 (93%) of 46 patients undergoing anterior decompression and fusion alone (p < 0.001) and in 17 (81%) of 21 patients undergoing anterior decompression and fusion with supplemental posterior fusion (p = 0.0015). The overall complication rate for this series was 25.4%. Interestingly, the overall complication rate was similar for both the lone anterior surgery and combined anterior-posterior groups, but the incidence of adjacent-segment disease was greater in the lone anterior surgery group.

Conclusions

Significant improvement in Nurick grade can be achieved in patients who undergo anterior surgery for cervical myelopathy for primarily ventral disease or loss of cervical lordosis. In selected high-risk patients who undergo multilevel ventral decompression, supplemental posterior fixation and arthrodesis allows for low rates of construct failure with acceptable added morbidity.