Risk factors for revision after shoulder arthroplasty: 1,825 shoulder arthroplasties from the Norwegian Arthroplasty Register

Background and purpose Previous studies on shoulder arthroplasty have usually described small patient populations, and few articles have addressed the survival of shoulder implants. We describe the results of shoulder replacement in the Norwegian population (of 4.7 million) during a 12-year period. Trends in the use of shoulder arthroplasty during the study period were also investigated

Factors That Affect Large Subunit Ribosomal DNA Amplicon Sequencing Studies of Fungal Communities: Classification Method, Primer Choice, and Error

Nuclear large subunit ribosomal DNA is widely used in fungal phylogenetics and to an increasing extent also amplicon-based environmental sequencing. The relatively short reads produced by next-generation sequencing, however, makes primer choice and sequence error important variables for obtaining accurate taxonomic classifications. In this simulation study we tested the performance of three classification methods: 1) a similarity-based method (BLAST + Metagenomic Analyzer, MEGAN); 2) a composition-based method (Ribosomal Database Project naïve Bayesian classifier, NBC); and, 3) a phylogeny-based method (Statistical Assignment Package, SAP). We also tested the effects of sequence length, primer choice, and sequence error on classification accuracy and perceived community composition. Using a leave-one-out cross validation approach, results for classifications to the genus rank were as follows: BLAST + MEGAN had the lowest error rate and was particularly robust to sequence error; SAP accuracy was highest when long LSU query sequences were classified; and, NBC runs significantly faster than the other tested methods. All methods performed poorly with the shortest 50–100 bp sequences. Increasing simulated sequence error reduced classification accuracy. Community shifts were detected due to sequence error and primer selection even though there was no change in the underlying community composition. Short read datasets from individual primers, as well as pooled datasets, appear to only approximate the true community composition. We hope this work informs investigators of some of the factors that affect the quality and interpretation of their environmental gene surveys

Local Soft Tissue Compression Enhances Fracture Healing in a Rabbit Fibula

Local soft tissue compression of fractures enhances fracture healing. The mechanism remains uncertain. Past studies have focused on intermittent soft tissue compression. We report a preliminary study assessing the relationship between constant soft tissue compression and enhanced fracture healing in an osteotomy model designed to minimize confounding variables. Fibulae of nine New Zealand white rabbits were bilaterally osteotomized, openly stabilized, and fitted with spandex stockinets. Soft tissue at the osteotomy site was unilaterally compressed using a deforming element (load = 26 mmHg). The contralateral side was saved as the control and was not compressed. Osteotomies were monitored with weekly radiographs. All fibulae in both groups were healed 6 weeks postoperatively. Micro-CT analysis of bone mineral density (BMD) and bone volume (BV) was then performed on both the experimental and control sides. Radiographic measurement of transverse callus-to-shaft ratios (TCSR) was compared. BMD of the experimental callus was greater than the noncompressed controls. BV and TCSR were not different between controls and experimental osteotomies. Constant local soft tissue compression produced significant increases in BMD, but not in BV or transverse callus size, indicating significant measurable increases in callus composition without significant change in gross dimensions. Our experimental design minimizes confounding factors, such as micromotion, immobilization, and altered venous flow, suggesting that these are not the primary mechanisms for fracture healing enhancement. Further studies with more animals and study groups are necessary to confirm efficacy and identify optimal compression pressures and schedules

C-reactive protein may misdiagnose prosthetic joint infections, particularly chronic and low-grade infections

BACKGROUND: Periprosthetic tissue cultures, sonication and synovial fluid cultures remain the gold standard for prosthetic joint infection (PJI) diagnosis. However, some 15-20% culture-negative PJI are still reported. Therefore, there is the need for other diagnostic criteria. One point of concern relative to the different definitions of PJI is as to the inclusion of the c-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) as diagnostic criteria for PJI despite them being non-specific inflammatory blood tests. PURPOSE: The purpose of the present study was to determine the relevance of CRP and the ESR in the diagnosis of PJI. METHODS: All PJI with positive cultures over a two-year period in two hospitals were reviewed. The main variables of the present study were the type of prosthesis and the CRP level. More information was recorded in those patients with normal CRP: radiographs, physical examination records and the ESR. RESULTS: Seventy-three patients were included in study. Pre-operative CRP levels were normal (lower than 0.8 mg/dl) in 23 patients, representing 32% of all PJI with positive cultures. Low virulence micro-organisms, 12 coagulase-negative staphylococci and four P. acnes, grew in most of them. They represented 70% of all PJI with normal CRP levels. In addition, 17 patients (23% of all PJI with positive cultures) had a normal ESR, a normal physical examination (they only presented with pain) and no clear loosening was observed in the radiographs. CONCLUSIONS: Per the American Association of Orthopaedic Surgeons (AAOS) guidelines or the Musculoskeletal Infection Society (MSIS), 23% of the patients in the present study with PJI would never have been identified. Blood inflammatory markers such as the CRP level and ESR may not be accurate as diagnostic tools in PJI, particularly to identify low-grade and chronic PJI