Reasons for Retirement Following Ulnar Collateral Ligament Reconstruction Among Major League Baseball Pitchers

Background:

Ulnar collateral ligament reconstruction (UCLR) has become an increasingly common procedure among Major League Baseball (MLB) pitchers. The long-term effects of this procedure on the career of an MLB pitcher are largely unknown.

Purpose/Hypothesis:

The purpose of this study was to determine why and when MLB pitchers who underwent UCLR during their careers retired from baseball as compared with controls. We hypothesized that pitchers who underwent UCLR are no more likely than control pitchers to retire from elbow or shoulder problems.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

All MLB pitchers who underwent UCLR were identified through publicly available data. A cohort of pitchers who did not undergo UCLR were matched to pitchers with a history of UCLR, based on sex, age, draft year, and draft round. Of those who were no longer pitching in the MLB, the reason for retirement was determined. Reason for retirement and length of career following UCLR (surgical group) and index year (control group) were determined and compared through prior studies via the MLB HITS database, MLB team websites, and publicly available internet-based injury reports.

Results:

Overall, 153 MLB pitchers who underwent UCLR between 1974 and 2015 are currently retired. Mean ± SD time to retirement was 4.4 ± 4.7 years (range, 0-26 years) after the index year in the control group and 4.4 ± 3.5 years (range, 0-15 years) after surgery in the UCLR group (P = .388). Patients who were status post-UCLR were significantly more likely to be released during the season (34 of 144, 23.6%) than were players who were not status post-UCLR (14 of 144, 9.7%) (P = .002). Shoulder injury as a reason for retirement was more common in the control group than the UCLR group (P = .011). Elbow injury as a reason for retirement was not more common in either group (P = .379). Leg injury as a reason for retirement was more common in the control group (P = .013). Performance as a reason for retirement was more common in the UCLR group than the control group (P < .001).

Conclusion:

MLB pitchers who have undergone UCLR are no more likely to retire from shoulder or elbow injuries than are those who have not undergone UCLR. MLB career length was similar between pitchers with and without a history of UCLR.

Results of Database Studies in Spine Surgery Can Be Influenced by Missing Data

BACKGROUND

National databases are increasingly being used for research in spine surgery; however, one limitation of such databases that has received sparse mention is the frequency of missing data. Studies using these databases often do not emphasize the percentage of missing data for each variable used and do not specify how patients with missing data are incorporated into analyses. This study uses the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database to examine whether different treatments of missing data can influence the results of spine studies.

QUESTIONS/PURPOSES

(1) What is the frequency of missing data fields for demographics, medical comorbidities, preoperative laboratory values, operating room times, and length of stay recorded in ACS-NSQIP? (2) Using three common approaches to handling missing data, how frequently do those approaches agree in terms of finding particular variables to be associated with adverse events? (3) Do different approaches to handling missing data influence the outcomes and effect sizes of an analysis testing for an association with these variables with occurrence of adverse events?

METHODS

Patients who underwent spine surgery between 2005 and 2013 were identified from the ACS-NSQIP database. A total of 88,471 patients undergoing spine surgery were identified. The most common procedures were anterior cervical discectomy and fusion, lumbar decompression, and lumbar fusion. Demographics, comorbidities, and perioperative laboratory values were tabulated for each patient, and the percent of missing data was noted for each variable. These variables were tested for an association with "any adverse event" using three separate multivariate regressions that used the most common treatments for missing data. In the first regression, patients with any missing data were excluded. In the second regression, missing data were treated as a negative or "reference" value; for continuous variables, the mean of each variable's reference range was computed and imputed. In the third regression, any variables with > 10% rate of missing data were removed from the regression; among variables with ≤ 10% missing data, individual cases with missing values were excluded. The results of these regressions were compared to determine how the different treatments of missing data could affect the results of spine studies using the ACS-NSQIP database.

RESULTS

Of the 88,471 patients, as many as 4441 (5%) had missing elements among demographic data, 69,184 (72%) among comorbidities, 70,892 (80%) among preoperative laboratory values, and 56,551 (64%) among operating room times. Considering the three different treatments of missing data, we found different risk factors for adverse events. Of 44 risk factors found to be associated with adverse events in any analysis, only 15 (34%) of these risk factors were common among the three regressions. The second treatment of missing data (assuming "normal" value) found the most risk factors (40) to be associated with any adverse event, whereas the first treatment (deleting patients with missing data) found the fewest associations at 20. Among the risk factors associated with any adverse event, the 10 with the greatest effect size (odds ratio) by each regression were ranked. Of the 15 variables in the top 10 for any regression, six of these were common among all three lists.

CONCLUSIONS

Differing treatments of missing data can influence the results of spine studies using the ACS-NSQIP. The current study highlights the importance of considering how such missing data are handled.

CLINICAL RELEVANCE

Until there are better guidelines on the best approaches to handle missing data, investigators should report how missing data were handled to increase the quality and transparency of orthopaedic database research. Readers of large database studies should note whether handling of missing data was addressed and consider potential bias with high rates or unspecified or weak methods for handling missing data.

Associations between resistance phenotype and gene expression in response to serial exposure to oxacillin and ciprofloxacin in Staphylococcus aureus

This study was designed to delineate the relationship between resistance phenotypes and gene expression in wild-type (SA^WT ), oxacillin-induced (SA^OXA ), ciprofloxacin-induced (SA^CIP ) and clinically acquired antibiotic-resistant Staphylococcus aureus (SA^CA ) exposed to oxacillin (β-lactam) and ciprofloxacin (fluoroquinolone). The phenotypic response and gene expression were varied with the antibiotic exposure. SA^WT was highly resistant to oxacillin (MIC = 8 μg ml^-1 ) after serial exposure to oxacillin, while the oxacillin susceptibility was not changed in SA^WT when exposed to ciprofloxacin (MIC = 0·25 μg ml^-1 ). The clinical isolate, SA^CA , was highly resistant to all classes of antibiotics used in this study. The increased resistance of SA^OXA and SA^CIP to penicillinase-labile penicillins was attributed to the production of β-lactamase, which is in good agreement with the overexpression of blaZ (>2-fold). The overexpression of efflux pump-related genes (norA, norB, norC, mdeA, mepR, mgrA and lmrS) was associated with the increased resistance of SA^CIP and SA^CA to aminoglycosides and quinolones. This study confirmed that the linkage between resistance phenotypes and molecular genotypes highly varied depending on intrinsic resistance profile, response to antibiotic exposure and genes conferring resistance. This study provides useful information for understanding the mechanisms of methicillin resistance in S. aureus in association with phenotypic and genotypic resistance determinants.

SIGNIFICANCE AND IMPACT OF THE STUDY

The improvement in current standards is essential to accurately detect methicillin-resistant Staphylococcus aureus in consideration of various resistance phenotypes and genotypes. The varied and distinctive expression patterns of antibiotic resistance-related genes were observed in S. aureus exposed to oxacillin and ciprofloxacin. It is worth noting the relationship between resistance phenotype and resistance genotype in terms of MIC values and expression of antibiotic resistance determinants. This study provides useful information for understanding the mechanisms of methicillin resistance in S. aureus in association with phenotypic and genotypic resistance determinants.

Lateral lumbar interbody fusion: a systematic review of complication rates

BACKGROUND CONTEXT

Lateral lumbar interbody fusion (LLIF) is a frequently used technique for the treatment of lumbar pathology. Despite its overall success, LLIF has been associated with a unique set of complications. However, there has been inconsistent evidence regarding the complication rate of this approach.

PURPOSE

To perform a systematic review analyzing the rates of medical and surgical complications associated with LLIF.

STUDY DESIGN

Systematic review.

PATIENT SAMPLE

6,819 patients who underwent LLIF reported in clinical studies through June 2016.

OUTCOME MEASURES

Frequency of complications within cardiac, vascular, pulmonary, urologic, gastrointestinal, transient neurologic, persistent neurologic, and spine (MSK) categories.

METHODS

This systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant studies that identified rates of any complication following LLIF procedures were obtained from PubMed, MEDLINE, and EMBASE databases. Articles were excluded if they did not report complications, presented mixed complication data from other procedures, or were characterized as single case reports, reviews, or case series containing less than 10 patients. The primary outcome was frequency of complications within cardiac, vascular, pulmonary, urologic, gastrointestinal, transient neurologic, persistent neurologic, and MSK categories. All rates of complications were based on the sample sizes of studies that mentioned the respective complications. The authors report no conflicts of interest directly or indirectly related to this work, and have not received any funds in support of this work.

RESULTS

A total of 2,232 articles were identified. Following screening of title, abstract, and full-text availability, 63 articles were included in the review. A total of 6,819 patients had 11,325 levels fused. The rate of complications for the categories included were as follows: wound (1.38%; 95% confidence interval [CI]=1.00%-1.85%), cardiac (1.86%; CI=1.33%-2.52%), vascular (0.81%; CI=0.44%-1.36%), pulmonary (1.47; CI=0.95%-2.16%), gastrointestinal (1.38%; CI=1.00%-1.87%), urologic (0.93%; CI=0.55%-1.47%), transient neurologic (36.07%; CI=34.74%-37.41%), persistent neurologic (3.98%; CI=3.42%-4.60%), and MSK or spine (9.22%; CI=8.28%-10.23%).

CONCLUSIONS

The current study is the first to comprehensively analyze the complication profile for LLIFs. The most significant reported complications were transient neurologic in nature. However, persistent neurologic complications occurred at a much lower rate, bringing into question the significance of transient symptoms beyond the immediate postoperative period. Through this analysis of complication profiles, surgeons can better understand the risks to and expectations for patients following LLIF procedures.

Hybrid polymer microfluidic platform to mimic varying vascular compliance and topology

Several cardiovascular pathologies and aging have been associated with alterations in the mechanical and structural properties of the vascular wall, leading to a reduction in arterial compliance and the development of constriction. In the past, rare efforts have been directed to understand the endothelial cell response to combined mechanical stimuli from fluid flow and substrate rigidity. Recent approaches using microfluidic platforms have limitations in precisely mimicking healthy and diseased vasculature conditions from altered topological and substrate compliance perspectives. To address this, we demonstrated an effective fabrication process to realize a hybrid polymer platform to test these mechanistic features of blood vessels. The salient features of the platform include circular microchannels of varying diameters, variation in substrate rigidity along the channel length, and the coexistence of microchannels with different cross sections on a single platform. The platform demonstrates the combined effects of flow-induced shear forces and substrate rigidity on the endothelial cell layer inside the circular microchannels. The experimental results indicate a pronounced cell response to flow induced shear stress via its interplay with the underlying substrate mechanics.

Patient knowledge regarding radiation exposure from spinal imaging

BACKGROUND CONTEXT

Spine surgeons employ a high volume of imaging in the diagnosis and evaluation of spinal pathology. However, little is known regarding patients' knowledge of the radiation exposure associated with these imaging techniques.

PURPOSE

To characterize spine patients' knowledge regarding radiation exposure from various imaging modalities.

STUDY DESIGN/SETTING

A cross-sectional survey study.

PATIENT SAMPLE

One hundred patients at their first clinic visit with a single spine surgeon at an urban institution.

OUTCOME MEASURES

The primary outcome was patient estimate of radiation dose for various common spinal imaging modalities as compared with true dose.

METHODS

An electronic survey was administered to all new patients before their first appointment with a single spinal surgeon. The survey asked patients to estimate how many chest x-rays (CXRs) worth of radiation were equivalent to various common spinal imaging modalities. Patient estimates were compared to true effective radiation doses determined from the literature. The survey also asked patients whether they would consider avoiding types of imaging modalities out of concern for excessive radiation exposure.

RESULTS

Patients accurately approximated the radiation associated with two views of the cervical spine, with a median estimate of 3.5 CXRs, compared with an actual value of 4.7 CXRs. However, patients underestimated the dose for computed tomography (CT) scans of the cervical spine (2.0 CXRs vs. 145.3 CXRs), two views of the lumbar spine (3.0 CXRs vs. 123.3 CXRs), and CT scans of the lumbar spine (2.0 CXRs vs. 638.3 CXRs). The majority of patients believed that there is at least some radiation exposure associated with magnetic resonance imaging (MRI). The percent of patients who would consider forgoing imaging recommend by their surgeon out of concern for radiation exposure was 14% for x-rays, 13% for CT scans, and 9% for MRI.

CONCLUSION

These results demonstrate a lack of patient understanding regarding radiation exposure associated with common spinal imaging techniques. These data suggest that patients might benefit from increased counseling and/or educational materials regarding radiation exposure before undergoing diagnostic imaging of the cervical or lumbar spine.

Severity Weighting of Postoperative Adverse Events in Orthopedic Surgery

Studies of adverse events (AEs) after orthopedic surgery commonly use composite AE outcomes. An example of such an outcome is any AE. These types of outcomes treat AEs with different clinical significance (eg, death, urinary tract infection) similarly. We conducted a study to address this shortcoming in research methodology by creating a single severity-weighted outcome that can be used to characterize the overall severity of a given patient's postoperative course. All orthopedic faculty members at 2 academic institutions were invited to complete a severity-weighting exercise in which AEs were assigned a percentage severity of death. Mean (standard error) severity weight for urinary tract infection was 0.23% (0.08%); blood transfusion, 0.28% (0.09%); pneumonia, 0.55% (0.15%); hospital readmission, 0.59% (0.23%); wound dehiscence, 0.64% (0.17%); deep vein thrombosis, 0.64% (0.19%); superficial surgical-site infection, 0.68% (0.23%); return to operating room, 0.91% (0.29%); progressive renal insufficiency, 0.93% (0.27%); graft/prosthesis/flap failure, 1.20% (0.34%); unplanned intubation, 1.38% (0.53%); deep surgical-site infection, 1.45% (0.38%); failure to wean from ventilator, 1.45% (0.48%); organ/space surgical-site infection, 1.76% (0.46%); sepsis without shock, 1.77% (0.42%); peripheral nerve injury, 1.83% (0.47%); pulmonary embolism, 2.99% (0.76%); acute renal failure, 3.95% (0.85%); myocardial infarction, 4.16% (0.98%); septic shock, 7.17% (1.36%); stroke, 8.73% (1.74%); cardiac arrest requiring cardiopulmonary resuscitation, 9.97% (2.46%); and coma, 15.14% (3.04%). Future studies may benefit from using this new severity-weighted outcome score.

Developing new automated alternation flicker using optic disc photography for the detection of glaucoma progression

PurposeTo evaluate a progression-detecting algorithm for a new automated matched alternation flicker (AMAF) in glaucoma patients.MethodsOpen-angle glaucoma patients with a baseline mean deviation of visual field (VF) test>-6 dB were included in this longitudinal and retrospective study. Functional progression was detected by two VF progression criteria and structural progression by both AMAF and conventional comparison methods using optic disc and retinal nerve fiber layer (RNFL) photography. Progression-detecting performances of AMAF and the conventional method were evaluated by an agreement between functional and structural progression criteria. RNFL thickness changes measured by optical coherence tomography (OCT) were compared between progressing and stable eyes determined by each method.ResultsAmong 103 eyes, 47 (45.6%), 21 (20.4%), and 32 (31.1%) eyes were evaluated as glaucoma progression using AMAF, the conventional method, and guided progression analysis (GPA) of the VF test, respectively. The AMAF showed better agreement than the conventional method, using GPA of the VF test (κ=0.337; P<0.001 and κ=0.124; P=0.191, respectively). The rates of RNFL thickness decay using OCT were significantly different between the progressing and stable eyes when progression was determined by AMAF (-3.49±2.86 μm per year vs -1.83±3.22 μm per year; P=0.007) but not by the conventional method (-3.24±2.42 μm per year vs -2.42±3.33 μm per year; P=0.290).ConclusionsThe AMAF was better than the conventional comparison method in discriminating structural changes during glaucoma progression, and showed a moderate agreement with functional progression criteria.

Minimally invasive lumbar decompression-the surgical learning curve

BACKGROUND CONTEXT

Minimally invasive spine surgery (MIS) procedures carry an inherently difficult learning curve based upon anecdotal evidence. Few studies have investigated the surgeon's learning curve for MIS lumbar laminectomy or laminotomy with or without discectomy.

PURPOSE

To characterize the learning curve of a 1- or 2-level MIS lumbar decompression (LD) based on perioperative and postoperative parameters .

STUDY DESIGN/SETTING

Retrospective analysis of a prospectively maintained registry was used for this study.

PATIENT SAMPLE

There were 228 consecutive patients who underwent a primary 1- or 2-level MIS LD by a single surgeon for degenerative spinal pathology from 2009 to 2014. From 2005 to 2006, 50 patients underwent 1- or 2-level open LD consecutively.

OUTCOME MEASURES

Perioperative and postoperative outcomes (complications, visual analogue scale [VAS] scores, reoperations) were the outcome measures for this study.

METHODS

Patients were stratified into first and second groups as determined by the case number at which the procedural time reached a plateau. Demographics, comorbidity, pain scores, and surgical outcomes were compared between the first 50 patients and the subsequent 178 patients. The secondary analysis compared the surgical outcomes between the initial 50 MIS and 50 open LD patients. No funds were received in support of this work.

RESULTS

The initial cohort was older with a higher comorbidity burden (p<.05). However, body mass index, gender, smoking status, and ethnicity did not differ between cohorts. The initial cohort incurred a greater procedural time (p<.001) and longer length of hospitalization (p<.05) than the second cohort. Estimated blood loss (EBL), pain scores, complication rates, recurrent herniation rates, and reoperation rates were similar between groups. In the secondary analysis, the open LD patients demonstrated greater procedural time, higher EBL, and longer length of hospital stay than the MIS patients. However, the reoperation rate and 30-day readmission rate were not different between the MIS and open patients.

CONCLUSIONS

Continued surgical experience was associated with a reduced operative time, shorter length of hospitalization, and similar blood loss following an MIS LD. Independent of surgical experience, all patients demonstrated similar improvements in clinical outcomes. These findings appear to suggest that although surgical experience may improve perioperative parameters (operative time, length of hospitalization), an MIS LD may initially be performed safely without prior experience.

A systematic review of diagnostic accuracy of vertebral fracture assessment (VFA) in postmenopausal women and elderly men

This systematic review was performed to compare the diagnostic accuracy of vertebral fracture assessment (VFA) with that of spinal radiography for identification of vertebral fractures (VFs). VFA appeared to have moderate sensitivity and high specificity for detecting VFs when compared with spinal radiography.

INTRODUCTION

VFs are recognized as the hallmark of osteoporosis, and a previous VF increases the risk of a future fracture. Therefore, the timely detection of VFs is important for prevention of further fractures. This systematic review examined the diagnostic accuracy of VFA using dual X-ray absorptiometry (DXA) to identify VFs.

METHODS

We searched for potentially relevant studies using electronic databases, including Ovid-Medline, Ovid-EMBASE, Cochrane library, and four Korean databases, from their inception to May 2013. We compared the diagnostic accuracy of VFA with that of spinal radiography for detection of VFs by analyzing the sensitivity and specificity using a 2 × 2 contingency table. Subgroup analyses were also performed on studies with a low risk of bias and applicability.

RESULTS

Twelve studies were analyzed for the diagnostic accuracy of VFA. The sensitivity and specificity were 0.70-0.93 and 0.95-1.00, respectively, analyzed on a per-vertebra basis, and 0.65-1.00 and 0.74-1.00 on a per-patient basis. The sensitivity and specificity of five studies in subgroups with a low risk of bias in the intervention test were 0.70-0.84 and 0.96-0.99, respectively. In studies with a low risk of bias in the patient selection, those based on a per-vertebra basis in three studies were 0.70-0.93 and 0.96-1.00, respectively.

CONCLUSIONS

VFA had moderate sensitivity and high specificity for detecting VF when compared with spinal radiography. However, the present findings are insufficient to assess whether spinal radiography should be replaced by VFA.

RHEB: a potential regulator of chondrocyte phenotype for cartilage tissue regeneration

As articular cartilage has a limited ability to self-repair, successful cartilage regeneration requires clinical-grade chondrocytes with innate characteristics. However, cartilage regeneration via chondrocyte transplantation is challenging, because chondrocytes lose their innate characteristics during in vitro expansion. Here, we investigated the mechanistic underpinning of the gene Ras homologue enriched in brain (RHEB) in the control of senescence and dedifferentiation through the modulation of oxidative stress in chondrocytes, a hallmark of osteoarthritis. Serial expansion of human chondrocytes led to senescence, dedifferentiation and oxidative stress. RHEB maintained the innate characteristics of chondrocytes by regulating senescence, dedifferentiation and oxidative stress, leading to the upregulation of COL2 expression via SOX9 and the downregulation of p27 expression via MCL1. RHEB also decreased the expression of COL10. RHEB knockdown mimics decreased the expression of SOX9, COL2 and MCL1, while abrogating the suppressive function of RHEB on p27 and COL10 in chondrocytes. RHEB-overexpressing chondrocytes successfully formed cartilage tissue in vitro as well as in vivo, with increased expression of GAG matrix and chondrogenic markers. RHEB induces a distinct gene expression signature that maintained the innate chondrogenic properties over a long period. Therefore, RHEB expression represents a potentially useful mechanism in terms of cartilage tissue regeneration from chondrocytes, by which chondrocyte phenotypic and molecular characteristics can be retained through the modulation of senescence, dedifferentiation and oxidative stress. Copyright © 2016 John Wiley & Sons, Ltd.

Healthy Eating Exploratory Program for the Elderly: Low Salt Intake in Congregate Meal Service

OBJECTIVES

This study reported on an exploratory program to help the low income elderly improve healthy eating behavior, specifically by reducing salt intake.

DESIGN

We conducted an exploratory program for 4 weeks for this study. The exploratory program involved offering menus with reduced salt and providing education on healthy eating. After the exploratory program, a survey of the elderly and in-depth interviews allowed us to evaluate the program for foodservice providers (dietitian, social workers, and volunteer workers). This study included both foodservice workers and elderly who actually used the foodservice in a congregate meal service system. This is a unique approach.

SETTING

A congregate meal service center in Seoul, Korea.

PARTICIPANTS

Seventy four elderly in a congregate meal service center.

MEASUREMENTS

Demographics were collected, and the healthy eating program and healthy eating education for elderly respondents were evaluated.

RESULTS

The elderly showed high satisfaction with the exploratory program for healthy eating. We found no significant differences in satisfaction with the program between the elderly who attended education sessions and those who did not, but more of the elderly from the education sessions showed positive behavioral change intentions.

CONCLUSION

The exploratory program influenced to reduce the salt intake of the elderly in congregate meal service. This study suggests cooperation of foodservice providers and the support of administrators is critical to the success of such programs.

Incidence and risk factors for pneumonia following anterior cervical decompression and fusion procedures: an ACS-NSQIP study

BACKGROUND CONTEXT

Postoperative pneumonia has important clinical consequences for both patients and the health-care system. Few studies have examined pneumonia following anterior cervical decompression and fusion (ACDF) procedures.

PURPOSE

This study aimed to determine the incidence and risk factors for development of pneumonia following ACDF procedures.

STUDY DESIGN/SETTING

A retrospective cohort study of data collected prospectively by the American College of Surgeons National Surgical Quality Improvement Program was carried out.

PATIENT SAMPLE

This study comprised 11,353 patients undergoing ACDF procedures during 2011-2013.

OUTCOME MEASURES

The primary outcome was diagnosis of pneumonia in the first 30 postoperative days.

METHODS

Independent risk factors for the development of pneumonia were identified using multivariate regression. Readmission rates were compared between patients who did and did not develop pneumonia using multivariate regression that adjusted for all demographic, comorbidity, and procedural characteristics.

RESULTS

The incidence of pneumonia was 0.45% (95% confidence interval=0.33%-0.57%). In the multivariate analysis, independent risk factors for the development of pneumonia were greater age (p<.001), dependent functional status (relative risk [RR]=5.3, p<.001), chronic obstructive pulmonary disease (RR=4.4, p<.001), and greater operative duration (p=.020). Patients who developed pneumonia following discharge had a higher readmission rate than other patients (72.7% vs. 2.4%, adjusted RR=24.5, p<.001). In total, 10.2% of all readmissions were caused by pneumonia.

CONCLUSIONS

Pneumonia occurs in approximately 1 in 200 patients following ACDF procedures. Patients who are older, are functionally dependent, or have chronic obstructive pulmonary disease are at greater risk. These patients should be counseled, monitored, and targeted with preventative interventions accordingly. Greater operative duration is also an independent risk factor. Approximately three in four patients who develop pneumonia following hospitalization for ACDF procedures are readmitted. This elevated readmission rate has implications for bundled payments and hospital performance reports.

AIMP1 downregulation restores chondrogenic characteristics of dedifferentiated/degenerated chondrocytes by enhancing TGF-β signal

Dedifferentiation and degeneration of chondrocytes critically influences the efficiency of cartilage repair. One of the causes is the defect of transforming growth factor (TGF)-β signaling that promotes chondrogenic differentiation and degeneration. In the present study, we found that aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1) negatively regulates TGF-β signaling via interactions with Smad2 and Smad3 in immunoprecipitation assay and luciferase assay. In addition, we observed that the AIMP1 expression level was significantly increased in osteoarthritis (OA) patient-derived degenerated chondrocytes compared with healthy control. So, we hypothesized that downregulation of AIMP1 using small-interfering RNA (siRNA) technology in dedifferentiated (collected at passage #6) and degenerated (obtained from OA-affected areas) chondrocytes could lead to recover TGF-β signaling in both chondrocytes. Indeed, AIMP1 downregulation restored TGF-β signaling by promoting phosphorylation of Smad2 and Smad3, which shows redifferentiated characteristics in both dedifferentiated and degenerated chondrocytes. Additionally, implantation analyses using in vivo mouse model clearly showed that AIMP1 downregulation resulted in the increased chondrogenic potential as well as the enhanced cartilage tissue formation in both dedifferentiated and degenerated chondrocytes. Histological analyses clarified that AIMP1 downregulation increased expression levels of collagen type II (Col II) and aggrecan, but not Col I expression. Taken together, these data indicate that AIMP1 downregulation using siRNA is a novel tool to restore TGF-β signaling and thereby increases the chondrogenic potential of dedifferentiated/degenerated chondrocytes, which could be further developed as a therapeutic siRNA to treat OA.

Mesenchymal stem cell allograft as a fusion adjunct in one- and two-level anterior cervical discectomy and fusion: a matched cohort analysis

BACKGROUND CONTEXT

Live mesenchymal stem cell (MSC) allograft-containing allogeneic bone grafts have recently gained popularity and currently account for greater than 17% of all bone grafts and bone graft substitutes used in spinal surgery. Although the claim of cellular bone matrices containing osteogenic cells with osteoinductive properties is attractive, little is known about their clinical success when used in anterior cervical discectomy and fusion (ACDF).

PURPOSE

The objective of this study was to report on the radiographic fusion rates in one- and two-level instrumented ACDF using an MSC.

STUDY DESIGN/SETTING

This was a retrospective review of prospectively matched cohort of patients with radiologic assessment of fusion as the primary end point.

PATIENT SAMPLE

Two matched cohorts of adult patients who underwent ACDF with MSC or standard allograft were included.

OUTCOMES MEASURES

The outcome measures included radiographic and clinical evidence of healing at 1 year.

METHODS

A consecutive series of 57 patients who underwent a one- or two-level instrumented ACDF procedure between 2010 and 2012 were retrospectively analyzed. All fusion constructs comprised an interbody allograft, an anterior plate, and Osteocel (NuVasive, San Diego, CA, USA). These patients were matched to a control group of 57 patients.

RESULTS

Of the 57 cases in both cohorts, 29 (50.9%) were single-level, and 28 (49.1%) were two-level instrumented ACDFs. There were no significant differences in patient age (p=.71), gender, comorbidity burden (Charlson Comorbidity Index [CCI]: 1.95; 2.42, p=.71) or body mass index (p=.79). At the 1-year follow-up, 50 of 57 (87.7%) patients in the Osteocel cohort demonstrated a solid fusion compared with 54 of 57 (94.7%) in the control group (p=.19). Seven (12.3%) patients in the Osteocel cohort were reported as having a failed fusion at 1 year.

CONCLUSIONS

This is the first non-industry sponsored study to analyze a matched cohort assessing the 1-year arthrodesis rates associated with a nonstructural MSC allograft in one- and two-level ACDF procedures. Although not statistically significant, patients treated with MSC allografts demonstrated lower fusion rates compared with a matched non-MSC cohort.