Inducible Cre-ERT recombinase technology is widely used for gene targeting studies. The second generation of inducible Cre-ERT recombinase, hemizygous B6.129S-Tg(UBC-cre/ERT2)1Ejb/J (hereafter abbreviated as Cre-ERT2), a fusion of a mutated estrogen receptor and Cre recombinase, was engineered to be more efficient and specific than the original Cre-ERT. The putative mechanism of selective Cre-mediated recombination is Cre sequestration in the cytoplasm in the basal state with translocation to the nucleus only in the presence of tamoxifen. We utilized both a reporter mouse (B6.129 (Cg)-Gt(ROSA)26Sor /J) and endothelin converting enzyme-1 floxed transgenic mouse line to evaluate Cre-ERT2 activity. We observed spontaneous Cre activity in both settings. Unintended Cre activity is a confounding factor that has a potentially large impact on data interpretation. Thus, it is important to consider background Cre activity in experimental design.

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Age and the length of time since injury correlated with a higher rate of shoulder, elbow, and wrist pain. The completeness of injury, neurological level, and gender were correlated with shoulder, elbow, and wrist pain, respectively.

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Background Calls to reform the US resident selection process are growing, given increasing competition and inefficiencies of the current system. Though numerous reforms have been proposed, they have not been comprehensively cataloged. Objective This scoping review was conducted to characterize and categorize literature proposing systems-level reforms to the resident selection process. Methods Following Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines, searches of Embase, MEDLINE, Scopus, and Web of Science databases were performed for references published from January 2005 to February 2020. Articles were included if they proposed reforms that were applicable or generalizable to all applicants, medical schools, or residency programs. An inductive approach to qualitative content analysis was used to generate codes and higher-order categories. Results Of 10 407 unique references screened, 116 met our inclusion criteria. Qualitative analysis generated 34 codes that were grouped into 14 categories according to the broad stages of resident selection: application submission, application review, interviews, and the Match. The most commonly proposed reforms were implementation of an application cap (n = 28), creation of a standardized program database (n = 21), utilization of standardized letters of evaluation (n = 20), and pre-interview screening (n = 13). Conclusions This scoping review collated and categorized proposed reforms to the resident selection process, developing a common language and framework to facilitate national conversations and change.

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Background Reverse total shoulder arthroplasty is a common treatment for patients with rotator cuff arthropathy who have failed a prior rotator cuff repair. Latissimus dorsi transfer can be performed simultaneously to reverse total shoulder arthroplasty for patients with preoperative external rotation deficiency. Current literature is limited with several studies providing functional and pain improvements at short-term follow-up; however, there is a deficit in data regarding mid-term outcomes. The purpose of this study was to evaluate the clinical and radiographic outcomes following reverse total shoulder arthroplasty with latissimus dorsi transfer with mid-term follow-up. We hypothesized significant improvement in external rotation and shoulder functionality for patients with preoperative external rotation lag. Methods We retrospectively reviewed patients who underwent reverse total shoulder arthroplasty with latissimus dorsi transfer. Preoperative and postoperative changes in range of motion were assessed. American Shoulder and Elbow Surgeon Score and the Simple Shoulder Test were used to evaluate changes in shoulder function while pain scores were assessed using the Visual Analog Scale (VAS). Radiographs were reviewed for rotator cuff arthropathy, fatty infiltration, scapular notching, baseplate loosening, and osteolysis. We reported frequency and mean ± standard deviation for categorical and continuous variables, respectively. Means were compared using the paired Student's t-test and proportions using the Chi-square test. Results Fifteen patients met the inclusion criteria. The mean age of the cohort was 71.7 ± 8.4 years (range 51.2–87.8 years) with a mean follow-up of 6.3 ± 4.1 years (range 1.0–14.5 years). Reverse total shoulder arthroplasty with latissimus dorsi transfer improved external rotation (−7 ± 21.3° to 38 ± 15.8°; p value = 0.001). There was no statistically significant difference regarding forward flexion (116.3 ± 45.4° to 133.7 ± 14.7°; p value = 0.17) and internal rotation (T12 to L2; p value = 0.57). The procedure led to an increase in American Shoulder and Elbow Surgeon Score scores (37 ± 19 to 62 ± 22; p = 0.005) and Simple Shoulder Test scores (2 ± 2 to 6 ± 3; p value = 0.001) with a significant reduction in Visual Analog Scale scores (5 ± 3 to 2 ± 3; p value = 0.022). The procedure corrected external rotation lag in 10 patients. Radiographically, rotator cuff arthropathy was found to be grade 3 in two patients, grade 4 A in four patients, grade 4B in eight patients, and grade 5 in one patient. On postoperative imaging, scapular notching was found in six patients (40%). Twelve patients had cortical humeral erosion at the site of the latissimus dorsi transfer. Only one patient experienced a shoulder-related complication which was aseptic baseplate loosening and required a revision reverse total shoulder arthroplasty with allograft. Conclusions In this study, patients undergoing reverse total shoulder arthroplasty with latissimus dorsi transfer experienced improvements in range of motion, functional scores, and pain at mid-term follow-up. The shoulder-related complication rate was low. Level of evidence: IV; Case series.

A pleiotropic quantitative trait locus (QTL) for bone geometry and mechanical performance in mice was mapped to distal chromosome 4 via an intercross of recombinant congenic mice HcB-8 and HcB-23. To study the QTL in isolation, we have generated C3H.B10-(rs6355453-rs13478087) (C.B.4.3) and C3H.B10-(rs6369860-D4Mit170) (C.B.4.2) congenic strains that harbor ~20 Mb and ~3 Mb, respectively, of chromosome 4 overlapping segments from C57BL/10ScSnA (B10) within the locus on a C3H/DiSnA (C3H) background. Using 3-point bend testing and standard beam equations, we phenotyped these mice for femoral mid-diaphyseal geometry and biomechanical performance. We analyzed the results via 2-way ANOVA, using sex and genotype as factors. In the C.B.4.3 strain, we found that homozygous B10/B10 male mice had smaller cross sectional area (CSA) and reduced total displacement than homozygous C3H/C3H mice. Sex by genotype interaction was also observed for maximum load and stiffness for C3H/C3H and B10/B10 mice, respectively. In C.B.4.2 strain, we found that homozygous B10/B10 mice had lower total displacement, post-yield displacement (PYD), stiffness, yield load and maximum load than mice harboring C3H allele. Sex by genotype interaction was observed in B10/B10 mice for perimeter, outer minor axis (OMA) and CSA. There were no significant differences in tissue level mechanical performance, which suggest that the QTL acts primarily on circumferential bone size. These data confirm the prior QTL mapping data and support other work demonstrating the importance of chromosome 4 QTL on bone modeling and bone responses to mechanical loading.