Atomic force microscopy imaging for nanoscale and microscale assessments of extracellular matrix in intervertebral disc and degeneration.

Degeneration of the intervertebral disc (IVD) is a condition that is often associated with debilitating back pain. There are no disease-modifying treatments available to halt the progression of this ubiquitous disorder. This is partly due to a lack of understanding of extracellular matrix (ECM) changes that occur at the micro- and nanometer size scales as the disease progresses. Over the past decade, atomic force microscopy (AFM) has been utilized as a tool to investigate the impact of disease on nanoscale structure of ECM in bone, skin, tendon, and dentin. We have expanded this methodology to include the IVD and report the first quantitative analysis of ECM structure at submicron size scales in a murine model for progressive IVD degeneration. Collagen D-spacing, a metric of nanoscale structure at the fibril level, was observed as a distribution of values with an overall average value of 62.5 ± 2.5 nm. In degenerative discs, the fibril D-spacing distribution shifted towards higher values in both the annulus fibrosus and nucleus pulposus (NP) (P < .05). A novel microstructural feature, collagen toroids, defined by a topographical pit enclosed by fibril-forming matrix was observed in the NP. With degeneration, these microstructures became more numerous and the morphology was altered from circular (aspect ratio 1.0 ± 0.1) to oval (aspect ratio 1.5 ± 0.4), P < .005. These analyses provide ECM structural details of the IVD at size scales that have historically been missing in studies of disc degeneration. Knowledge gained from these insights may aid the development of novel disease-modifying therapeutics.

Lumbar Laminectomy in the Outpatient Setting Is Associated With Lower 30-Day Complication Rates.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To compare the incidence of complications in patients undergoing single-level and 2-level lumbar laminectomy in either the inpatient or outpatient settings. METHODS: Patients who underwent single-level and 2-level lumbar laminectomy were identified in the ACS NSQIP database from the years 2006 to 2015. Independent patient variables were recorded, including demographics and preoperative health characteristics. Logistic regression was used to determine the risk of postoperative complications for both a 1- and 2-level lumbar laminectomy as well as to identify independent risk factors for a complication. Comparisons were made between 2 groups: (1) inpatient and (2) outpatient as determined by billing data. RESULTS: A total of 18 076 single- and 2-level lumbar laminectomy cases were identified with 10 743 (59.4%) inpatient procedures and 7333 (40.6%) outpatient procedures. The incidence of any postoperative complication was significantly lower in the outpatient group than in the inpatient group among all cohorts including 1-level lumbar laminectomy (1.9% vs 6.7%), 2-level lumbar laminectomy (3.17% vs 7.38%), as well as in the combined cohort of 1- and 2-level laminectomies (2.47% vs 7.01%). Significant independent risk factors for complications after lumbar laminectomy were identified, including body mass index (BMI) >30 kg/m2, age ≥55 years, a functional status of partially dependent, chronic obstructive pulmonary disease (COPD), chronic steroid use, American Society of Anesthesiologists (ASA) class 3 or 4, and operative time >90 minutes. CONCLUSIONS: This study reports a lower overall complication rate in the 30-day postoperative period following 1- and 2-level lumbar laminectomy performed in an outpatient versus inpatient setting. Significant risk factors for complications included BMI >30 kg/m2, age ≥55 years, a functional status of partially dependent, COPD, chronic steroid use, ASA class 3 or 4, and operative time >90 minutes.

Comparative and Predictor Analysis of 30-day Readmission, Reoperation, and Morbidity in Patients Undergoing Multilevel ACDF Versus Single and Multilevel ACCF Using the ACS-NSQIP Dataset.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The aim of this study was to determine the differences in 30-day readmission, reoperation, and morbidity for patients undergoing multilevel anterior cervical discectomy and fusion (ACDF) or single and multilevel anterior cervical corpectomy and fusion (ACCF). SUMMARY OF BACKGROUND DATA: Despite increasing rates of surgical treatment of cervical spine disease, few studies have compared outcomes by surgical technique. To the best of our knowledge, this is the only large-scale administrative database study that directly evaluates early outcomes between multilevel ACDF and single and multilevel ACCF. METHODS: Patients who underwent ACDF and ACCF were identified using the NSQIP database. Multivariate regression was utilized to compare rates of readmission, reoperation, morbidity, and specific complications between surgical techniques, and to evaluate for predictors of primary outcomes. RESULTS: We identified 15,600 patients. ACCF independently predicted (P < 0.001) greater reoperation (odds ratio [OR] = 1.876) and morbidity (OR = 1.700), but not readmission, on multivariate analysis. ACCF was also associated with greater rates of transfusion (OR = 3.273, P < 0.001) and DVT/thrombophlebitis (OR = 2.852, P = 0.001). ACCF had significantly (P < 0.001) greater operative time and length of stay. In the cohort, increasing age (P < 0.001), diabetes (P = 0.025), chronic obstructive pulmonary disease (P = 0.027), disseminated cancer (P = 0.009), and American Society of Anesthesiologists (ASA) class ≥3 (P < 0.001) predicted readmission. Age (P = 0.011), female sex (P = 0.001), heart failure (P = 0.002), ASA class ≥3 (P < 0.001), and increased creatinine (P = 0.044), white cell count (P = 0.033), and length of stay (P < 0.001) predicted reoperation. Age (P < 0.001), female sex (P = 0.002), disseminated cancer (P = 0.010), ASA class ≥3 (P < 0.001), increased white cell count (P = 0.036) and length of stay (P < 0.001), and decreased hematocrit (P < 0.001) predicted morbidity. Within ACDF, three or more levels treated compared to two levels did not predict poorer 30-day outcomes. CONCLUSION: Compared to multilevel ACDF, ACCF was associated with an 88% increased odds of reoperation and 70% increased odds of morbidity; readmission was similar between techniques. Older age, higher ASA class, and specific comorbidities predicted poorer 30-day outcomes. These findings can guide surgical solution given specific factors. LEVEL OF EVIDENCE: 3.

Recurrent Shoulder Instability: Do Morbidity and Treatment Differ Based on Insurance?

BACKGROUND: Patients with public insurance often face barriers to obtaining prompt orthopaedic care. For patients with recurrent traumatic anterior shoulder instability, delayed care may be associated with increasing bone loss and subsequently more extensive surgical procedures. PURPOSE/HYPOTHESIS: The purpose of this study was to evaluate whether differences exist in patients undergoing treatment for shoulder instability between those with Medicaid versus non-Medicaid insurance. We hypothesized that at the time of surgery, Medicaid patients would have experienced greater delays in care, would have a more extensive history of instability, would have more bone loss, and would require more extensive surgical procedures than other patients. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Patients were identified who underwent surgical stabilization for traumatic anterior shoulder instability between January 1, 2011, and December 1, 2015, at a single sports medicine practice. Clinic, billing, and operative records were reviewed for each patient to determine age, sex, insurance type, total number of instability episodes, time from first instability episode to surgery, intraoperative findings, and procedure performed. Glenoid bone loss was quantified by use of preoperative imaging studies. RESULTS: During this time period, 206 patients (55 Medicaid, 131 private insurance, 11 Tricare, 9 workers' compensation) underwent surgical stabilization for traumatic anterior shoulder instability. Average wait time from initial injury to surgery was 1640 days (95% CI, 1155-2125 days) for Medicaid patients compared with 1237 days (95% CI, 834-1639 days) for others (P = .005). Medicaid patients were more likely to have sustained 5 or more instability events at the time of surgery (OR, 3.3; 95% CI, 1.64-6.69; P = .001), had a higher risk of having 15% or more glenoid bone loss on preoperative imaging (OR, 3.5; 95% CI, 1.3-10.0; P = .01), and had a higher risk of requiring Latarjet or other open stabilization procedures as opposed to an arthroscopic repair (OR, 3.0; 95% CI, 1.5-6.2; P = .002) when compared with other patients. CONCLUSION: Among patients undergoing surgery for traumatic anterior shoulder instability, patients with Medicaid had significantly more delayed care. Correspondingly, they reported a more extensive history of instability, were more likely to have severe bone loss, and required more invasive stabilization procedures.

CD200-CD200R1 inhibitory signaling prevents spontaneous bacterial infection and promotes resolution of neuroinflammation and recovery after stroke.

BACKGROUND: Ischemic stroke results in a robust inflammatory response within the central nervous system. As the immune-inhibitory CD200-CD200 receptor 1 (CD200R1) signaling axis is a known regulator of immune homeostasis, we hypothesized that it may play a role in post-stroke immune suppression after stroke. METHODS: In this study, we investigated the role of CD200R1-mediated signaling in stroke using CD200 receptor 1-deficient mice. Mice were subjected to a 60-min middle cerebral artery occlusion and evaluated at days 3 and 7, representing the respective peak and early resolution stages of neuroinflammation in this model of ischemic stroke. Infarct size and behavioral deficits were assessed at both time points. Central and peripheral cellular immune responses were measured using flow cytometry. Bacterial colonization was determined in lung tissue homogenates both after acute stroke and in an LPS model of systemic inflammation. RESULTS: In wild-type (WT) animals, CD200R1 was expressed on infiltrating monocytes and lymphocytes after stroke but was absent on microglia. Early after ischemia (72 h), CD200R1-knockout (KO) mice had significantly poorer survival rates and an enhanced susceptibility to spontaneous bacterial colonization of the respiratory tract compared to wild-type (WT) controls, despite no difference in infarct or neurological deficits. While the CNS inflammation was resolved by day 7 post-stroke in WT mice, brain-resident microglia and monocyte activation persisted in CD200R1-KO mice, accompanied by a delayed, augmented lymphocyte response. At this time point, CD200R1-KO mice displayed greater weight loss, more severe neurological deficits, and impaired motor function compared to WT. Systemically, CD200R1-KO mice exhibited signs of persistent infection including lymphopenia, T cell activation and memory conversion, and narrowing of the TCR repertoire. These findings were confirmed in a second model of acute neuroinflammation induced by systemic endotoxin challenge. CONCLUSION: This study defines an essential role of CD200-CD200R1 signaling in stroke. Loss of CD200R1 led to high mortality, increased rates of post-stroke infection, and enhanced entry of peripheral leukocytes into the brain after ischemia, with no increase in infarct size. This suggests that the loss of CD200 receptor leads to enhanced peripheral inflammation that is triggered by brain injury.

Approach-based Comparative and Predictor Analysis of 30-day Readmission, Reoperation, and Morbidity in Patients Undergoing Lumbar Interbody Fusion Using the ACS-NSQIP Dataset.

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to determine the difference in 30-day readmission, reoperation, and morbidity for patients undergoing either posterior or anterior lumbar interbody fusion. SUMMARY OF BACKGROUND DATA: Despite increasing utilization of lumbar interbody fusion to treat spinal pathology, few studies compare outcomes by surgical approach, particularly using large nationally represented cohorts. METHODS: Patients who underwent lumbar interbody fusion were identified using the NSQIP database. Rates of readmission, reoperation, morbidity, and associated predictors were compared between posterior/transforaminal (PLIF/TLIF) and anterior/lateral (ALIF/LLIF) lumbar interbody fusion using multivariate regression. Bonferroni-adjusted alpha-levels were utilized whereby variables were significant if their P values were less than the alpha-level or trending if their P values were between 0.05 and the alpha-level. RESULTS: We identified 26,336 patients. PLIF/TLIF had greater operative time (P = 0.015), transfusion (P < 0.001), UTI (P = 0.008), and stroke/CVA (P = 0.026), but lower prolonged ventilation (P < 0.001) and DVT (P = 0.002) rates than ALIF/LLIF. PLIF/TLIF independently predicted greater morbidity on multivariate analysis (odds ratio: 1.155, P = 0.0019).In both groups, experiencing a complication and, in PLIF/TLIF, ASA-class ≥3 predicted readmission (P < 0.001). Increased age trended toward readmission in ALIF/LLIF (P = 0.003); increased white cell count (P = 0.003), dyspnea (P = 0.030), and COPD (P = 0.005) trended in PLIF/TLIF. In both groups, increased hospital stay and wound/site-related complication predicted reoperation (P < 0.001). Adjunctive posterolateral fusion predicted reduced reoperation in ALIF/LLIF (P = 0.0018). ASA-class ≥3 (P = 0.016) and age (P = 0.021) trended toward reoperation in PLIF/TLIF and ALIF/LLIF, respectively. In both groups, age, hospital stay, reduced hematocrit, dyspnea, ASA-class ≥3, posterolateral fusion, and revision surgery and, in PLIF/TLIF, bleeding disorder predicted morbidity (P < 0.001). Female sex (P = 0.010), diabetes (P = 0.042), COPD (P = 0.011), and disseminated cancer (P = 0.032) trended toward morbidity in PLIF/TLIF; obesity trended in PLIF/TLIF (P = 0.0022) and ALIF/LLIF (P = 0.020). CONCLUSION: PLIF/TLIF was associated with a 15.5% increased odds of morbidity; readmission and reoperation were similar between approaches. Older age, higher ASA-class, and specific comorbidities predicted poorer 30-day outcomes, while procedural-related factors predicted only morbidity. These findings can guide surgical approach given specific factors. LEVEL OF EVIDENCE: 3.

Aging alters the immunological response to ischemic stroke.

The peripheral immune system plays a critical role in aging and in the response to brain injury. Emerging data suggest inflammatory responses are exacerbated in older animals following ischemic stroke; however, our understanding of these age-related changes is poor. In this work, we demonstrate marked differences in the composition of circulating and infiltrating leukocytes recruited to the ischemic brain of old male mice after stroke compared to young male mice. Blood neutrophilia and neutrophil invasion into the brain were increased in aged animals. Relative to infiltrating monocyte populations, brain-invading neutrophils had reduced phagocytic potential, and produced higher levels of reactive oxygen species and extracellular matrix-degrading enzymes (i.e., MMP-9), which were further exacerbated with age. Hemorrhagic transformation was more pronounced in aged versus young mice relative to infarct size. High numbers of myeloperoxidase-positive neutrophils were found in postmortem human brain samples of old (> 71 years) acute ischemic stroke subjects compared to non-ischemic controls. Many of these neutrophils were found in the brain parenchyma. A large proportion of these neutrophils expressed MMP-9 and positively correlated with hemorrhage and hyperemia. MMP-9 expression and hemorrhagic transformation after stroke increased with age. These changes in the myeloid response to stroke with age led us to hypothesize that the bone marrow response to stroke is altered with age, which could be important for the development of effective therapies targeting the immune response. We generated heterochronic bone marrow chimeras as a tool to determine the contribution of peripheral immune senescence to age- and stroke-induced inflammation. Old hosts that received young bone marrow (i.e., Young → Old) had attenuation of age-related reductions in bFGF and VEGF and showed improved locomotor activity and gait dynamics compared to isochronic (Old → Old) controls. Microglia in young heterochronic mice (Old → Young) developed a senescent-like phenotype. After stroke, aged animals reconstituted with young marrow had reduced behavioral deficits compared to isochronic controls, and had significantly fewer brain-infiltrating neutrophils. Increased rates of hemorrhagic transformation were seen in young mice reconstituted with aged bone marrow. This work suggests that age alters the immunological response to stroke, and that this can be reversed by manipulation of the peripheral immune cells in the bone marrow.

Chondral Injuries and Irreparable Meniscal Tears Among Adolescents With Anterior Cruciate Ligament or Meniscal Tears Are More Common in Patients With Public Insurance.

BACKGROUND: Access to health care services is a critical component of health care reform and may differ among patients with different types of insurance. Hypothesis/Purpose: The purpose was to compare adolescents with private and public insurance undergoing surgery for anterior cruciate ligament (ACL) and/or meniscal tears. We hypothesized that patients with public insurance would have a delayed presentation from the time of injury and therefore would have a higher incidence of chondral injuries and irreparable meniscal tears and lower preoperative International Knee Documentation Committee (IKDC) scores than patients with private insurance. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: This was a retrospective study of patients under 21 years of age undergoing ACL reconstruction and/or meniscal repair or debridement from January 2013 to March 2016 at a single pediatric sports medicine center. Patients were identified by a search of Current Procedural Terminology (CPT) codes. A chart review was performed for insurance type; preoperative diagnosis; date of injury, initial office visit, and surgery; preoperative IKDC score; intraoperative findings; and procedures. RESULTS: The study group consisted of 119 patients (mean age, 15.0 ± 1.7 years). Forty-one percent of patients had private insurance, while 59% had public insurance. There were 27 patients with isolated meniscal tears, 59 with combined meniscal and ACL tears, and 33 with isolated ACL tears. The mean time from injury to presentation was 56 days (range, 0-457 days) in patients with private insurance and 136 days (range, 0-1120 days) in patients with public insurance ( P = .02). Surgery occurred, on average, 35 days after the initial office visit in both groups. The mean preoperative IKDC score was 53 in both groups. Patients with meniscal tears with public insurance were more likely to require meniscal debridement than patients with private insurance (risk ratio [RR], 2.3; 95% CI, 1.7-3.1; P = .02). Patients with public insurance were more likely to have chondral injuries of grade 2 or higher (RR, 4.4; 95% CI, 3.9-5.0; P = .02). CONCLUSION: In adolescent patients with ACL or meniscal tears, patients with public insurance had a more delayed presentation than those with private insurance. They also tended to have more moderate-to-severe chondral injuries and meniscal tears, if present, that required debridement rather than repair. More rapid access to care might improve the prognosis of young patients with ACL and meniscal injuries with public insurance.

Nano-particle delivery of brain derived neurotrophic factor after focal cerebral ischemia reduces tissue injury and enhances behavioral recovery.

BACKGROUND: Low levels of brain-derived neurotrophic factor (BDNF) are linked to delayed neurological recovery, depression, and cognitive impairment following stroke. Supplementation with BDNF reverses these effects. Unfortunately, systemically administered BDNF in its native form has minimal therapeutic value due to its poor blood brain barrier permeability and short serum half-life. In this study, a novel nano-particle polyion complex formulation of BDNF (nano-BDNF) was administered to mice after experimental ischemic stroke. METHODS: Male C57BL/6J (8-10weeks) mice were randomly assigned to receive nano-BDNF, native-BDNF, or saline treatment after being subjected to 60min of reversible middle cerebral artery occlusion (MCAo). Mice received the first dose at 3 (early treatment), 6 (intermediate treatment), or 12h (delayed treatment) following stroke onset; a second dose was given in all cohorts at 24h after stroke onset. Post-stroke outcome was evaluated by behavioral, histological, and molecular analysis for 15days after stroke. RESULTS: Early and intermediate nano-BDNF treatment led to a significant reduction in cerebral tissue loss. Delayed treatment led to improved memory/cognition, reduced post-stroke depressive phenotypes, and maintained myelin basic protein and brain BDNF levels, but had no effect on tissue atrophy. CONCLUSIONS: The results indicate that administration of a novel nano-particle formulation of BDNF leads to both neuroprotective and neuro-restorative effects after stroke.

Chronic metformin treatment improves post-stroke angiogenesis and recovery after experimental stroke.

Metformin is currently the first-line treatment drug for type 2 diabetes. Metformin is a well-known activator of AMP-activated protein kinase (AMPK). In experimental studies, metformin has been shown to exert direct vascular effects by increasing vascular endothelial growth factor expression and improving microvascular density. As stroke is the leading cause of long-term disability and angiogenesis is implicated as an important mechanism in functional recovery, we hypothesized that chronic metformin treatment would improve post-stroke functional recovery by enhancing functional microvascular density. For this study, C57BL/6N male mice were subjected to a 60-min middle cerebral artery occlusion, and were given 50 mg/kg/day metformin beginning 24 h post-stroke for 3 weeks. Behavioral recovery was assessed using adhesive-tape removal and the apomorphine-induced turning test. The role of angiogenesis was assessed by counting vessel branch points from fluorescein-conjugated lectin-perfused brain sections. Importantly even if metformin treatment was initiated 24 h after injury it enhanced recovery and significantly improved stroke-induced behavioral deficits. This recovery occurred in parallel with enhanced angiogenesis and with restoration of endogenous cerebral dopaminergic tone and revascularization of ischemic tissue. We assessed if the effects on recovery and angiogenesis were mediated by AMPK. When tested in AMPK α-2 knockout mice, we found that metformin treatment did not have the same beneficial effects on recovery and angiogenesis, suggesting that metformin-induced angiogenic effects are mediated by AMPK. The results from this study suggest that metformin mediates post-stroke recovery by enhancing angiogenesis, and these effects are mediated by AMPK signaling.