Local FK506 delivery induces osteogenesis in in vivo rat bone defect and rabbit spine fusion models.

Bone grafting procedures are commonly used for the repair, regeneration, and fusion of bones in in a wide range of orthopaedic surgeries, including large bone defects and spine fusion procedures. Autografts are the clinical gold standard, though recombinant human bone morphogenetic proteins (rhBMPs) are often used, particularly in difficult clinical situations. However, treatment with rhBMPs can have off-target effects and significantly increase surgical costs, adding to patients' already high economic and mental burden. Recent studies have identified that FDA-approved immunosuppressant drug, FK506 (Tacrolimus), can also activate the BMP pathway by binding to its inhibitors. This study tested the hypothesis that FK506, as a standalone treatment, could induce osteogenic differentiation of human mesenchymal stromal cells (hMSCs), as well as functional bone formation in a rat segmental bone defect model and rabbit spinal fusion model. FK506 potentiated the effect of low dose BMP-2 to enhance osteogenic differentiation and mineralization of hMSCs in vitro. Standalone treatment with FK506 delivered on a collagen sponge, produced consistent bone bridging of a rat critically-sized femoral defect with functional mechanical properties comparable to naïve bone. In a rabbit single level posterolateral spine fusion model, treatment with FK506 delivered on a collagen sponge successfully fused the L5-L6 vertebrae at rates comparable to rhBMP-2 treatment. These data demonstrate the ability of FK506 to induce bone formation in human cells and two challenging in vivo models, and indicate FK506 can be utilized either as a standalone treatment or in conjunction with rhBMP to treat a variety of spine disorders.

Cell-based versus corticosteroid injections for knee pain in osteoarthritis: a randomized phase 3 trial.

Various types of cellular injection have become a popular and costly treatment option for patients with knee osteoarthritis despite a paucity of literature establishing relative efficacy to each other or corticosteroid injections. Here we aimed to identify the safety and efficacy of cell injections from autologous bone marrow aspirate concentrate, autologous adipose stromal vascular fraction and allogeneic human umbilical cord tissue-derived mesenchymal stromal cells, in comparison to corticosteroid injection (CSI). The study was a phase 2/3, four-arm parallel, multicenter, single-blind, randomized, controlled clinical trial with 480 patients with a diagnosis of knee osteoarthritis (Kellgren-Lawrence II-IV). Participants were randomized to the three different arms with a 3:1 distribution. Arm 1: autologous bone marrow aspirate concentrate (n = 120), CSI (n = 40); arm 2: umbilical cord tissue-derived mesenchymal stromal cells (n = 120), CSI (n = 40); arm 3: stromal vascular fraction (n = 120), CSI (n = 40). The co-primary endpoints were the visual analog scale pain score and Knee injury and Osteoarthritis Outcome Score pain score at 12 months versus baseline. Analyses of our primary endpoints, with 440 patients, revealed that at 1 year post injection, none of the three orthobiologic injections was superior to another, or to the CSI control. In addition, none of the four groups showed a significant change in magnetic resonance imaging osteoarthritis score compared to baseline. No procedure-related serious adverse events were reported during the study period. In summary, this study shows that at 1 year post injection, there was no superior orthobiologic as compared to CSI for knee osteoarthritis. ClinicalTrials.gov Identifier: NCT03818737.

Sclerostin small-molecule inhibitors promote osteogenesis by activating canonical Wnt and BMP pathways.

Background: The clinical healing environment after a posterior spinal arthrodesis surgery is one of the most clinically challenging bone-healing environments across all orthopedic interventions due to the absence of a contained space and the need to form de novo bone. Our group has previously reported that sclerostin in expressed locally at high levels throughout a developing spinal fusion. However, the role of sclerostin in controlling bone fusion remains to be established. Methods: We computationally identified two FDA-approved drugs, as well as a single novel small-molecule drug, for their ability to disrupt the interaction between sclerostin and its receptor, LRP5/6. The drugs were tested in several in vitro biochemical assays using murine MC3T3 and MSCs, assessing their ability to (1) enhance canonical Wnt signaling, (2) promote the accumulation of the active (non-phosphorylated) form of ß-catenin, and (3) enhance the intensity and signaling duration of BMP signaling. These drugs were then tested subcutaneously in rats as standalone osteoinductive agents on plain collagen sponges. Finally, the top drug candidates (called VA1 and C07) were tested in a rabbit posterolateral spine fusion model for their ability to achieve a successful fusion at 6 wk. Results: We show that by controlling GSK3b phosphorylation our three small-molecule inhibitors (SMIs) simultaneously enhance canonical Wnt signaling and potentiate canonical BMP signaling intensity and duration. We also demonstrate that the SMIs produce dose-dependent ectopic mineralization in vivo in rats as well as significantly increase posterolateral spine fusion rates in rabbits in vivo, both as standalone osteogenic drugs and in combination with autologous iliac crest bone graft. Conclusions: Few if any osteogenic small molecules possess the osteoinductive potency of BMP itself - that is, the ability to form de novo ectopic bone as a standalone agent. Herein, we describe two such SMIs that have this unique ability and were shown to induce de novo bone in a stringent in vivo environment. These SMIs may have the potential to be used in novel, cost-effective bone graft substitutes for either achieving spinal fusion or in the healing of critical-sized fracture defects. Funding: This work was supported by a Veteran Affairs Career Development Award (IK2-BX003845).

Multifocal heterotopic ossification in a man with germline variants of LIM Mineralization Protein-1 (LMP-1).

A 54-year-old man with a history of unimelic, post-traumatic multifocal heterotopic ossification (HO) and normal genetic analysis of ACVR1 and GNAS had variants of unknown significance (VUS) in PDLIM-7 (PDZ and LIM Domain Protein 7), the gene encoding LMP-1 (LIM Mineralization Protein-1), an intracellular protein involved in the bone morphogenetic protein (BMP) pathway signaling and ossification. In order to determine if the LMP-1 variants were plausibly responsible for the phenotype observed, a series of in vitro experiments were conducted. C2C12 cells were co-transfected with a BMP-responsive reporter as well as the LMP-1 wildtype (wt) construct or the LMP-1T161I or the LMP-1D181G constructs (herein designated as LMP-161 or LMP-181) corresponding to the coding variants detected in the patient. A significantly increased BMP-reporter activity was observed in LMP-161 or LMP-181 transfected cells compared to the wt cells. The LMP-181 variant exhibited BMP-reporter activity with a four-fold increase over the LMP-1 wt protein. Similarly, mouse pre-osteoblastic MC3T3 cells transfected with the patient's LMP-1 variants expressed higher levels of osteoblast markers both at mRNA and protein levels and preferentially mineralized when stimulated with recombinant BMP-2 compared to control cells. Presently, there are no pathogenic variants of LMP-1 known to induce HO in humans. Our findings suggest that the germline variants in LMP-1 detected in our patient are plausibly related to his multifocal HO (LMP1-related multifocal HO). Further observations will be required to firmly establish this gene-disease relationship.

Telehealth Can Be Implemented Across a Musculoskeletal Service Line Without Compromising Patient Satisfaction.

Background: The COVID-19 pandemic has led to changes to in-office orthopedic care, with a rapid shift to telemedicine. Institutions' lack of established infrastructure for these types of visits has posed challenges requiring attention to confidentiality, safety, and patient satisfaction. Purpose: The aim of this study was to analyze the feasibility of telemedicine in orthopedics during the pandemic and its effect on efficiency and patient satisfaction. Methods: Patients seen by the Emory University Department of Orthopaedics Sports Medicine and Upper Extremity Divisions via telemedicine from March 23 to April 24, 2020, were contacted by telephone. Each patient was asked to respond to questions on satisfaction, ease of use, and potential future use; satisfaction with telemedicine and previous clinical visits were measured using a modified 5-point Likert scale. Results: Of the 762 patients seen, 346 (45.4%) completed the telemedicine questionnaire. Satisfaction varied by visit type, with average scores of 4.88/5 for in-office clinic visits versus 4.61/5 for telemedicine visits. There was no significant difference among age groups for satisfaction ratings. Patients 65 years old or older reported significantly longer visit times and decreased ease of use with the telemedicine platform. Conclusion: Telemedicine in a large orthopedics department was successfully implemented without compromising patient satisfaction. The use of telemedicine allows many patients to be seen quickly and efficiently without diminishing their musculoskeletal clinical experience.

The temporal and spatial expression of sclerostin and Wnt signaling factors during the maturation of posterolateral lumbar spine fusions.

The bone healing environment in the posterolateral spine following arthrodesis surgery is one of the most challenging in all of orthopedics and our understanding of the molecular signaling pathways mediating osteogenesis during spinal fusion is limited. In this study, the spatial and temporal expression pattern of Wnt signaling factors and inhibitors during spinal fusion was assessed for the first time. Bilateral posterolateral spine arthrodesis with autologous iliac crest bone graft was performed on 21 New Zealand White rabbits. At 1-, 2-, 3-, 4-, and 6-weeks, the expression of sclerostin and a variety of canonical and noncanonical Wnts signaling factors was measured by qRT-PCR from tissue separately collected from the transverse processes, the Outer and Inner Zones of the fusion mass, and the adjancent paraspinal muscle. Immunohistochemistry for sclerostin protein was also performed. Sclerostin and many Wnt factors, especially Wnt3a and Wnt5a, were found to have distinct spatial and temporal expression patterns. For example, harvesting ICBG caused a significant increase in sclerostin expression. Furthermore, the paraspinal muscle immediately adjacent to the transplanted ICBG also had significant increases in sclerostin expression at 3 weeks, suggesting new potential mechanisms for pseudarthroses following spinal arthrodesis. The presented work is the first description of the spatial and temporal expression of sclerostin and Wnt signaling factors in the developing spine fusion, filling an important knowledge gap in the basic biology of spinal fusion and potentially aiding in the development of novel biologics to increase spinal fusion rates.

Current Procedural Terminology-based Procedure Categorization Enhances Cost Prediction of Medicare Severity Diagnosis Related Group in Spine Surgery.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The aim of this study was to analyze how a Current Procedural Terminology (CPT)-based categorization method can predict cost variation in surgical spine procedures. SUMMARY OF BACKGROUND DATA: Neck and back disorders affect a majority of the adult population and account for tens of billions of dollars in health care spending each year. In the era of bundled payments and value-based reimbursement, it is imperative for surgeons to identify sources of cost variability across surgical spine procedures. Historically, this has been accomplished using Medicare Severity Diagnosis Related Group (MS-DRG) codes, but they utilize an overly simplistic categorization of surgical procedures. The specificity and familiarity of the CPT coding structure makes it a better option for categorizing differences in surgical decision making and technique. METHODS: Hospital billing data for patients undergoing a surgical spine procedure requiring an overnight, in-patient stay was retrospectively collected over 4 fiscal years (2012-2016) from a single health care system. Linear regression analysis was performed to assess the correlation between cost variation and: spine-specific MS-DRG codes; a novel CPT-based categorization method; and the combination of MS-DRG codes and CPT-based categorization. RESULTS: There were 5020 surgical procedures were analyzed with respect to 16 different MS-DRG codes and 30 distinct CPT-based surgical categories (CSCs). Linear regression results were: MS-DRG R2 = 0.6545 (P < 0.001); CSC R2 = 0.5709 (P < 0.001); and R2 = 0.744 for the combined MS-DRG and CSC methods (P < 0.05). Median difference between the actual and predicted cost for the combined model was -$261.00, compared with -$727.50 for the CSC model and -$478.70 for the MS-DRG model. CONCLUSION: Addition of the CPT-based categorization method to MS-DRG coding provides an enhanced method to evaluate the association between predicted and actual cost when using linear regression analysis to assess cost variation in spine surgery.Level of Evidence: 3.

A scalable tool for adjudication of time sensitive cases during COVID-19 pandemic.

BACKGROUND: During the COVID-19 pandemic, prioritization of care and utilization of scarce resources are daily considerations in healthcare systems that have never experienced these issues before. Elective surgical cases have been largely postponed, and surgery departments are struggling to correctly and equitably determine which cases need to proceed. A resource to objectively prioritize and track time sensitive cases would be useful as an adjunct to clinical decision-making. METHODS: A multidisciplinary working group at Emory Healthcare developed and implemented an adjudication tool for the prioritization of time sensitive surgeries. The variables identified by the team to form the construct focused on the patient's survivability according to actuarial data, potential impact on function with delay in care, and high-level biology of disease. Implementation of the prioritization was accomplished with a database design to streamline needed communication between surgeons and surgical adjudicators. All patients who underwent time sensitive surgery between 4/10/20 and 6/15/20 across 5 campuses were included. RESULTS: The primary outcomes of interest were calculated patient prioritization score and number of days until operation. 1767 cases were adjudicated during the specified time period. The distribution of prioritization scores was normal, such that real-time adjustment of the empiric algorithm was not required. On retrospective review, as the patient prioritization score increased, the number of days to the operating room decreased. This confirmed the functionality of the tool and provided a framework for organization across multiple campuses. CONCLUSIONS: We developed an in-house adjudication tool to aid in the prioritization of a large cohort of canceled and time sensitive surgeries. The tool is relatively simple in its design, reproducible, and data driven which allows for an objective adjunct to clinical decision-making. The database design was instrumental in communication optimization during this chaotic period for patients and surgeons.

Examination of the Role of Cells in Commercially Available Cellular Allografts in Spine Fusion: An in Vivo Animal Study.

BACKGROUND: Despite the extensive use of cellular bone matrices (CBMs) in spine surgery, there is little evidence to support the contribution of cells within CBMs to bone formation. The objective of this study was to determine the contribution of cells to spinal fusion by direct comparisons among viable CBMs, devitalized CBMs, and cell-free demineralized bone matrix (DBM). METHODS: Three commercially available grafts were tested: a CBM containing particulate DBM (CBM-particulate), a CBM containing DBM fibers (CBM-fiber), and a cell-free product with DBM fibers only (DBM-fiber). CBMs were used in viable states (CBM-particulatev and CBM-fiberv) and devitalized (lyophilized) states (CBM-particulated and CBM-fiberd), resulting in 5 groups. Viable cell counts and bone morphogenetic protein-2 (BMP-2) content on enzyme-linked immunosorbent assay (ELISA) within each graft material were measured. A single-level posterolateral lumbar fusion was performed on 45 athymic rats with 3 lots of each product implanted into 9 animals per group. After 6 weeks, fusion was assessed using manual palpation, micro-computed tomography (µ-CT), and histological analysis. RESULTS: The 2 groups with viable cells were comparable with respect to cell counts, and pairwise comparisons showed no significant differences in BMP-2 content across the 5 groups. Manual palpation demonstrated fusion rates of 9 of 9 in the DBM-fiber specimens, 9 of 9 in the CBM-fiberd specimens, 8 of 9 in the CBM-fiberv specimens, and 0 of 9 in both CBM-particulate groups. The µ-CT maturity grade was significantly higher in the DBM-fiber group (2.78 ± 0.55) compared with the other groups (p < 0.0001), while none of the CBM-particulate samples demonstrated intertransverse fusion in qualitative assessments. The viable and devitalized samples in each CBM group were comparable with regard to fusion rates, bone volume fraction, µ-CT maturity grade, and histological features. CONCLUSIONS: The cellular component of 2 commercially available CBMs yielded no additional benefits in terms of spinal fusion. Meanwhile, the groups with a fiber-based DBM demonstrated significantly higher fusion outcomes compared with the CBM groups with particulate DBM, indicating that the DBM component is probably the key determinant of fusion. CLINICAL RELEVANCE: Data from the current study demonstrate that cells yielded no additional benefit in spinal fusion and emphasize the need for well-designed clinical studies on cellular graft materials.

Managing Resident Workforce and Education During the COVID-19 Pandemic: Evolving Strategies and Lessons Learned.

BACKGROUND: The novel coronavirus and associated Coronavirus Disease 2019 (COVID-19) is rapidly spreading throughout the world, with robust growth in the United States. Its drastic impact on the global population and international health care is swift, evolving, and unpredictable. The effects on orthopaedic surgery departments are predominantly indirect, with widespread cessation of all nonessential orthopaedic care. Although this is vital to the system-sustaining measures of isolation and resource reallocation, there is profound detriment to orthopaedic training programs. METHODS: In the face of new pressures on the finite timeline on an orthopaedic residency, the Emory University School of Medicine Department of Orthopaedics has devised a 5-pronged strategy based on the following: (1) patient and provider safety, (2) uninterrupted necessary care, (3) system sustainability, (4) adaptability, and (5) preservation of vital leadership structures. RESULTS: Our 5 tenants support a 2-team system, whereby the residents are divided into cycling "active-duty" and "working remotely" factions. In observation of the potential incubation period of viral symptoms, phase transitions occur every 2 weeks with strict adherence to team assignments. Intrateam redundancy can accommodate potential illness to ensure a stable unit of able residents. Active duty residents participate in in-person surgical encounters and virtual ambulatory encounters, whereas remotely working residents participate in daily video-conferenced faculty-lead, case-based didactics and pursue academic investigation, grant writing, and quality improvement projects. To sustain this, faculty and administrative 2-team systems are also in place to protect the leadership and decision-making components of the department. CONCLUSIONS: The novel coronavirus has decimated the United States healthcare system, with an unpredictable duration, magnitude, and variability. As collateral damage, orthopaedic residencies are faced with new challenges to provide care and educate residents in the face of safety, resource redistribution, and erosion of classic learning opportunities. Our adaptive approach aims to be a generalizable tactic to optimize our current landscape.

Correction: Sangadala, S. et al. FK506 Induces Ligand-Independent Activation of the Bone Morphogenetic Protein Pathway and Osteogenesis. Int. J. Mol. Sci. 2019, 20, 1900.

The authors wish to make the following corrections to this paper [...].

Rational Selection of Patient-Reported Outcomes Measures in Lumbar Spine Surgery Patients.

BACKGROUND: The Short Form-12 (SF-12) was developed as a shorter version of the SF-36, yet there has been limited validation of its reliability at measuring postoperative changes. The purpose of this study was to determine if the SF-12 could safely substitute for the SF-36 in measuring postoperative change in lumbar spine surgery patients and if the condition specific (Oswestry Disability Index [ODI]) or pain (visual analog scale [VAS]) instruments, provided additional utility. METHODS: A total of 972 patients from a single center who underwent lumbar spine surgery for a predominant symptom of radiating leg pain with (n = 237) or without (n = 735) fusion and prospectively completed both SF-36 and ODI instruments before and after surgery were included. The SF-12 score was calculated from the appropriate subset of SF-36 responses. The absolute sensitivity and the intraclass correlation coefficient were calculated. Reliability of each instrument to measure preoperative to postoperative change was calculated as the standardized response mean. RESULTS: The SF-12 and SF-36 demonstrated a strong correlation with each other ([0.97, P < .001] and [0.93, P < .001], respectively) preoperatively and postoperatively. The SF-12 and SF-36 scores were moderately to strongly inversely correlated with the ODI. The ODI showed greater reliability at measuring change than the SF-12 for both fusion (0.94 versus 0.72) and nonfusion (0.81 versus 0.33) lumbar surgery patients. CONCLUSIONS: The SF-12 was as effective as the SF-36 to measure general health status in lumbar spine surgery patients, and both were moderate to strong predictors of ODI preoperatively and postoperatively, but lack the reliability to detect change seen with the ODI or VAS after surgical intervention. LEVEL OF EVIDENCE: 3. CLINICAL RELEVANCE: These data suggest that the SF-12 is a valid substitute for the SF-36 to measure postoperative outcomes changes, but that the ODI should continue to be used to measure condition specific changes in function.

Spine Infections Reduced at Dedicated Orthopaedics and Spine Hospital.

BACKGROUND: Previous studies stratified postoperative infection risk by patient comorbidities. However, it is unclear whether the incidence varies by surgical approach in a specialized orthopaedic setting. This study aims to compare infection rates and microbiologic characteristics of postoperative spine infections requiring return to the operating room for debridement by hospital setting: a dedicated orthopaedic and spine hospital versus a general hospital serving multiple surgical specialties. METHODS: The study is a retrospective review of prospectively collected data. Procedures performed between March 2006 and August 2008 at the multispecialty university hospital were compared with cases at an orthopaedic specialty hospital from September 2008 through August 2016. The surgeons, residents, and patients were similar, but the operative venue changed in 2008. RESULTS: The overall general university hospital infection rate was 2.03%, higher than the overall infection rate at the dedicated orthopaedic and spine hospital of 1.31% (P < .0104). The general university infection rate was 2.27% in the final years of practice, compared with 0.91% at the dedicated orthopaedic and spine hospital (P < .0001) during a recent 2-year time frame. Demographic variables did not significantly differ between the 2 settings. The overall proportion of Gram-negative infection rates was not statistically different (21.7% vs 18.6%), despite an increased proportion of Gram-negative infections at the general university hospital following surgery from an anterior approach. Most of the organisms isolated in both facilities were Staphylococcus species. There was no difference in the seasonality of postoperative spine infections in either setting. CONCLUSIONS: In transitioning from a multispecialty university hospital to a dedicated orthopaedic hospital, the incidence of postoperative spine infections was significantly reduced to 0.91%. Despite the change in venue, the proportion of Gram-negative infections (∼20%) following spine surgery did not significantly change. These results suggest improved infection rates during the course of the last 10 years with consistent proportions of Gram-negative infections. LEVEL OF EVIDENCE: 3.

Noggin regulates foregut progenitor cell programming, and misexpression leads to esophageal atresia.

Esophageal atresia (EA/TEF) is a common congenital abnormality present in 1 of 4000 births. Here we show that atretic esophagi lack Noggin (NOG) expression, resulting in immature esophagus that contains respiratory glands. Moreover, when using mouse esophageal organoid units (EOUs) or tracheal organoid units (TOUs) as a model of foregut development and differentiation in vitro, NOG determines whether foregut progenitors differentiate toward esophageal or tracheal epithelium. These results indicate that NOG is a critical regulator of cell fate decisions between esophageal and pulmonary morphogenesis, and its lack of expression results in EA/TEF.

Modifiable, Postoperative Risk Factors for Delayed Discharge Following Total Knee Arthroplasty: The Influence of Hypotension and Opioid Use.

BACKGROUND: We sought to identify independent modifiable risk factors for delayed discharge after total knee arthroplasty (TKA) that have been previously underrepresented in the literature, particularly postoperative opioid use, postoperative laboratory abnormalities, and the frequency of hypotensive events. METHODS: Data from 1033 patients undergoing TKA for primary osteoarthritis of the knee between June 2012 and August 2014 at an academic orthopedic specialty hospital were reviewed. Patient demographics, comorbidities, inpatient opioid medication, postoperative hypotensive events, and abnormalities in laboratory values, all occurring on postoperative day 0 or 1, were collected. Multivariate logistic regression analysis was performed to identify independent risk factors for a prolonged length of stay (LOS) >3 days. RESULTS: The average age of patients undergoing primary TKA in our cohort was 65.9 (standard deviation, 9.1) years, and 61.7% were women. The mean LOS for all patients was 2.64 days (standard deviation, 1.14; range, 1-9). And 15.3% of patients had a LOS >3 days. On multivariate logistic regression analysis, nonmodifiable risk factors associated with a prolonged LOS included nonwhite race (odds ratio [OR], 2.01), single marital status (OR, 1.53), and increasing age (OR, 1.47). Modifiable risk factors included every 5 postoperative hypotensive events (OR, 1.31), 10-mg increases in oral morphine equivalent consumption (OR, 1.04), and postoperative laboratory abnormalities (hypocalcemia: OR, 2.15; low hemoglobin: OR, 2.63). CONCLUSION: This study identifies potentially modifiable factors that are associated with increased LOS after TKA. Doubling down on efforts to control the narcotic use and to use opioid alternatives when possible will likely have efficacy in reducing LOS. Attempts should be made to correct laboratory abnormalities and to be cognizant of patient opioid use, age, and race when considering potential avenues to reduce LOS.

FK506 Induces Ligand-Independent Activation of the Bone Morphogenetic Protein Pathway and Osteogenesis.

Osteoinductive bone morphogenetic proteins (BMPs), including BMP-2, have a unique capability of mediating bone formation both in orthotopic and ectopic locations. Immunosuppresive macrolides have been shown to potentiate BMP-2 activity through FKBP12, but these have yet to translate to effective osteoinductive therapies. Herein, we show the osteogenic activity of FK506 as a stand-alone agent in direct comparison to BMP-2 both in vitro and in vivo. FK506 was capable of producing stand-alone alkaline phosphatase induction in C2C12 cells comparable to that seen with rhBMP-2. FK506 treatment activated the BMP receptor, as shown by increased pSmad1/5 levels, and produced significantly higher mRNA levels of the early response genes in BMP and TGF-ß pathways. Additionally, the FK506 induction of alkaline phosphatase was shown to be resistant to Noggin treatment. In vivo osteogenic activity of FK506 was tested by local delivery on a collagen sponge in an ectopic subcutaneous implantation model in the rat. Dose responses of FK506 showed increasing levels of ectopic mineralization comparable to the mineral volume produced by BMP-2 delivery. These findings suggest that the use of FK506 can enhance osteoblastic differentiation in vitro and can induce mineralization when delivered locally in vivo.

Prosthetic Joint Infection Trends at a Dedicated Orthopaedics Specialty Hospital.

INTRODUCTION: Historically, a majority of prosthetic joint infections (PJIs) grew Gram-positive bacteria. While previous studies stratified PJI risk with specific organisms by patient comorbidities, we compared infection rates and microbiologic characteristics of PJIs by hospital setting: a dedicated orthopaedic hospital versus a general hospital serving multiple surgical specialties. METHODS: A retrospective review of prospectively collected data on 11,842 consecutive primary hip and knee arthroplasty patients was performed. Arthroplasty cases performed between April 2006 and August 2008 at the general university hospital serving multiple surgical specialties were compared to cases at a single orthopaedic specialty hospital from September 2008 to August 2016. RESULTS: The general university hospital PJI incidence rate was 1.43%, with 5.3% of infections from Gram-negative species. In comparison, at the dedicated orthopaedic hospital, the overall PJI incidence rate was substantially reduced to 0.75% over the 8-year timeframe. Comparing the final two years of practice at the general university facility to the most recent two years at the dedicated orthopaedics hospital, the PJI incidence was significantly reduced (1.43% vs 0.61%). Though the overall number of infections was reduced, there was a significantly higher proportion of Gram-negative infections over the 8-year timeframe at 25.3%. CONCLUSION: In transitioning from a multispecialty university hospital to a dedicated orthopaedic hospital, the PJI incidence has been significantly reduced despite a greater Gram-negative proportion (25.3% versus 5.3%). These results suggest a change in the microbiologic profile of PJI when transitioning to a dedicated orthopaedic facility and that greater Gram-negative antibiotic coverage could be considered.