Monitoring the Progression of Spontaneous Articular Cartilage Healing with Infrared Spectroscopy

Objective. Evaluation of early compositional changes in healing articular cartilage is critical for understanding tissue repair and for therapeutic decision-making. Fourier transform infrared imaging spectroscopy (FT-IRIS) can be used to assess the molecular composition of harvested repair tissue. Furthermore, use of an infrared fiber-optic probe (IFOP) has the potential for translation to a clinical setting to provide molecular information in situ. In the current study, we determined the feasibility of IFOP assessment of cartilage repair tissue in a rabbit model, and assessed correlations with gold-standard histology. Design. Bilateral osteochondral defects were generated in mature white New Zealand rabbits, and IFOP data obtained from defect and adjacent regions at 2, 4, 6, 8, 12, and 16 weeks postsurgery. Tissues were assessed histologically using the modified O’Driscoll score, by FT-IRIS, and by partial least squares (PLS) modeling of IFOP spectra. Results. The FT-IRIS parameters of collagen content, proteoglycan content, and collagen index correlated significantly with modified O’Driscoll score (P = 0.05, 0.002, and 0.02, respectively), indicative of their sensitivity to tissue healing. Repair tissue IFOP spectra were distinguished from normal tissue IFOP spectra in all samples by PLS analysis. However, the PLS model for prediction of histological score had a high prediction error, which was attributed to the spectral information being acquired from the tissue surface only. Conclusion. The strong correlations between FT-IRIS data and histological score support further development of the IFOP technique for clinical applications, although further studies to optimize data collection from the full sample depths are required

Genetic Determinants of Lipid Traits in Diverse Populations from the Population Architecture using Genomics and Epidemiology (PAGE) Study

For the past five years, genome-wide association studies (GWAS) have identified hundreds of common variants associated with human diseases and traits, including high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels. Approximately 95 loci associated with lipid levels have been identified primarily among populations of European ancestry. The Population Architecture using Genomics and Epidemiology (PAGE) study was established in 2008 to characterize GWAS–identified variants in diverse population-based studies. We genotyped 49 GWAS–identified SNPs associated with one or more lipid traits in at least two PAGE studies and across six racial/ethnic groups. We performed a meta-analysis testing for SNP associations with fasting HDL-C, LDL-C, and ln(TG) levels in self-identified European American (∼20,000), African American (∼9,000), American Indian (∼6,000), Mexican American/Hispanic (∼2,500), Japanese/East Asian (∼690), and Pacific Islander/Native Hawaiian (∼175) adults, regardless of lipid-lowering medication use. We replicated 55 of 60 (92%) SNP associations tested in European Americans at p<0.05. Despite sufficient power, we were unable to replicate ABCA1 rs4149268 and rs1883025, CETP rs1864163, and TTC39B rs471364 previously associated with HDL-C and MAFB rs6102059 previously associated with LDL-C. Based on significance (p<0.05) and consistent direction of effect, a majority of replicated genotype-phentoype associations for HDL-C, LDL-C, and ln(TG) in European Americans generalized to African Americans (48%, 61%, and 57%), American Indians (45%, 64%, and 77%), and Mexican Americans/Hispanics (57%, 56%, and 86%). Overall, 16 associations generalized across all three populations. For the associations that did not generalize, differences in effect sizes, allele frequencies, and linkage disequilibrium offer clues to the next generation of association studies for these traits

Changes in leg length and hip offset in navigated imageless vs. conventional total hip arthroplasty

Abstract While previous studies on navigated total hip replacement (nTHA) focused on acetabular component positioning, we compared the results of nTHA with conventional total hip replacement (cTHA) in respect of changes in leg length and hip offset. In a single-center study results radiographic parameters of patients with unilateral THA were included. Data were retrospectively analyzed from computer navigation data and radiographs. Analysis concentrated on the discrepancy in leg length (LLD) and hip offset (OSD) between the affected and unaffected hip. The effect of the procedure was defined as the difference between postoperative and preoperative LLD and OSD values in each group. 2332 patients were analyzed. Both nTHA and cTHA were effective in restoring LLD and OSD by reducing the preoperative value significantly (p < 0.001). Regarding changes in LLD, no statistical difference between nTHA and cTHA could be found. Changes in OSD nTHA was a slightly more effective than cTHA (− 2.06 ± 6.00 mm vs. − 1.50 ± 5.35 mm; p < 0.05). Both navigated and conventional THA were successful in reconstruction of leg length and hip offset, while postoperative offset discrepancy was significantly lower in the navigated group at the cost of longer operation times. If these results are clinically relevant further investigation is needed

Hofmeister Effects in Membrane Biology: The Role of Ionic Dispersion Potentials

The Hofmeister effects in membrane biology were studied. The influence of ionic dispersion potentials on the binding of peptides to memebranes was also demonstrated. It was shown that the large attractive ionic disperion potentials acting on anions at biological concentrations result in negative interfacial tension changes. It was shown why the ionic dispersion potential near an oil-water interface was similar to the chemical potential of different n-alkanes

Case report: Good prognosis in leiomyosarcoma of the kidney

The Casimir-Polder force is an important long-range interaction involved in adsorption and desorption of molecules in fluids. We explore Casimir-Polder interactions between methane molecules in water, and between a molecule in water near SiO2 and hexane surfaces. Inclusion of the finite molecular size in the expression for the Casimir-Polder energy leads to estimates of the dispersion contribution to the binding energies between molecules and between one molecule and a planar surface

Vancomycin-laden calcium phosphate-calcium sulfate composite allows bone formation in a rat infection model.

ObjectiveLocal antibiotic delivery systems with differing chemical and mechanical properties have been developed to assist in the management of osteomyelitis. We investigated the bone conductive and resorptive capabilities of a calcium phosphate-calcium sulfate (CaP/CaS) composite compared with commercially available polymethylmethacrylate (PMMA). In addition, we compared the in vivo preventative and treatment efficacies of both biomaterials in a proven osteomyelitis model.MethodsSixty-four, male Sprague-Dawley rats were inoculated with 10 μl of 1.5 x 108 CFU/ml of Staphylococcus aureus in a surgically drilled defect in the right proximal tibia. Infected animals were randomly allocated into prevention and treatment groups with 32 rats each. In the prevention group, the defect was filled with a plug containing either PMMA or CaP/CaS immediately after the inoculation. In the treatment group, the infected defects were irrigated, debrided, and filled with either a PMMA or CaP/CaS plug. Both CaP/CaS and PMMA were impregnated with 10% weight of vancomycin. Rats were sacrificed 6 weeks after cement insertion. Infection was detected by bacterial culture and histological analysis. Bone formation in the defect was assessed with micro-computed tomography and histology.ResultsNo bacteria were detected in any group. Both the prevention and treatment groups using CaP/CaS had significantly more bone volume fraction, bone area, and cartilage area than the PMMA groups.ConclusionsWhen loaded with 10% of vancomycin, CaP/CaS and PMMA have the same efficacy for treatment and prevention of osteomyelitis. CaP/CaS enhances bone defect healing through improved bone remodeling in our osteomyelitis rat model

Mechanical instability induces osteoclast differentiation independent of the presence of a fibrous tissue interface and osteocyte apoptosis in a rat model for aseptic loosening

Background and purpose - Insufficient initial fixation or early micromotion of an implant is associated with a thin layer of fibrous tissue at the peri-implant interface. It is unknown if bone loss is induced by the fibrous tissue interface acting as an active biological membrane, or as a membrane that will produce supraphysiologic fluid flow conditions during gait, which activates the mechanosensitive osteocytes to mediate osteoclast differentiation. We investigated whether mechanically induced osteolysis is dependent on the fibrous tissue interface as a biologically active scaffold, or if it merely acts as a conduit for fluid flow, affecting the mechanosensitive osteocytes in the peri-prosthetic bone. Methods - Using a rat model of mechanically instability-induced aseptic loosening, we assessed whether the induction of osteoclast differentiation was dependent on the presence of a peri-implant fibrous interface. We analyzed the amount of osteoclast differentiation, osteocyte apoptosis, pro-resorptive cytokine expression and bone loss using immunohistochemistry, mRNA expression and micro-CT. Results - Osteoclast differentiation and bone loss were induced by mechanical instability but were not affected by the presence of the fibrous tissue membrane or associated with osteocyte apoptosis. There was no increased mRNA expression of any of the cytokines in the fibrous tissue membrane compared with the peri-implant bone. Interpretation - Our data show that the fibrous tissue membrane in the interface plays a minor role in inducing bone loss. This indicates that the peri-implant bone adjacent to loose bone implants might play an important role for osteoclast differentiation

Subspecialty Rotation Exposure Across Accreditation Council for Graduate Medical Education-Accredited Orthopaedic Surgery Residency Programs.

INTRODUCTION: The Accreditation Council for Graduate Medical Education (ACGME) mandates certain procedural minimums for graduating residents of orthopaedic surgery programs and provides residency programs with comparative data on surgical case volume. It provides much less guidance and feedback to programs regarding the amount of time residents should spend on different rotations during residency. Comparative data regarding how much time residents are spending on general and subspecialty rotations may be of use to educational leadership as they consider curriculum changes and alternative training structures. The purpose of this study is to summarize the subspecialty rotation exposure across ACGME-accredited orthopaedic residency programs and to correlate the subspecialty rotation exposure with available program-specific factors. METHODS: This study contacted 162 ACGME-accredited orthopaedic residency programs and received rotation schedules from 115 programs (70.1%). Rotation schedules for postgraduate year 2 to 5 residents were categorized into the number of months spent on the following rotations: general orthopaedics, trauma, pediatrics, hand, sport, foot and ankle, arthroplasty, oncology, spine, research, and elective. The percentage of residency spent in each category was then calculated as the number of months divided by 48 months. Differences in the percent of residency spent on subspecialty rotations were compared for the following variables: program size and presence of subspecialty fellowships at the institution. RESULTS: On average, the greatest percentage of residency spent was in the following categories: trauma (16.6%; 8.0 months), general orthopaedics (13.7%; 6.6 months), and pediatrics (12.5%; 6.0 months). Rotations with the highest variation between programs included the following: general orthopaedics (SD 5.8 months; range 0 to 30 months), sport (SD 2.5 months; range 0 to 15 months), and arthroplasty (SD 2.3 months; range 0 to 11.8 months). Sixty-seven programs (63.2%) had dedicated blocks for research, and 25 programs (23.6%) had dedicated blocks for electives. No notable correlations were found between subspecialty exposure and program size or availability of subspecialty fellowship training at the program. CONCLUSION: Variability exists between ACGME-accredited orthopaedic surgery residency programs in subspecialty rotation exposure. Summarizing the subspecialty rotation exposure across accredited orthopaedic residency programs is useful to graduate medical education leadership for comparative purposes because they design and modify resident curricula