Background The capacity of skeletal muscles to regenerate relies on Pax7 + muscle stem cells (MuSC). While in vitro-amplified MuSC are activated and lose part of their regenerative capacity, in vitro-generated human muscle reserve cells (MuRC) are very similar to quiescent MuSC with properties required for their use in cell-based therapies. Methods In the present study, we investigated the heterogeneity of human MuRC and characterized their molecular signature and metabolic profile. Results We observed that Notch signaling is active and essential for the generation of quiescent human Pax7 + MuRC in vitro. We also revealed, by immunofluorescence and flow cytometry, two distinct subpopulations of MuRC distinguished by their relative Pax7 expression. After 48 h in differentiation medium (DM), the Pax7 High subpopulation represented 35% of the total MuRC pool and this percentage increased to 61% after 96 h in DM. Transcriptomic analysis revealed that Pax7 High MuRC were less primed for myogenic differentiation as compared to Pax7 Low MuRC and displayed a metabolic shift from glycolysis toward fatty acid oxidation. The bioenergetic profile of human MuRC displayed a 1.5-fold decrease in glycolysis, basal respiration and ATP-linked respiration as compared to myoblasts. We also observed that AMPKα1 expression was significantly upregulated in human MuRC that correlated with an increased phosphorylation of acetyl-CoA carboxylase (ACC). Finally, we showed that fatty acid uptake was increased in MuRC as compared to myoblasts, whereas no changes were observed for glucose uptake. Conclusions Overall, these data reveal that the quiescent MuRC pool is heterogeneous for Pax7 with a Pax7 High subpopulation being in a deeper quiescent state, less committed to differentiation and displaying a reduced metabolic activity. Altogether, our data suggest that human Pax7 High MuRC may constitute an appropriate stem cell source for potential therapeutic applications in skeletal muscle diseases.

Nowadays, Kingella kingae (K. kingae) is considered as the main bacterial cause of osteoarticular infections (OAI) in children aged less than 48 months. Next to classical acute hematogenous osteomyelitis and septic arthritis, invasive K. kingae infections can also give rise to atypical osteoarticular infections, such as cellulitis, pyomyositis, bursitis, or tendon sheath infections. Clinically, K. kingae OAI are usually characterized by a mild clinical presentation and by a modest biologic inflammatory response to infection. Most of the time, children with skeletal system infections due to K. kingae would not require invasive surgical procedures, except maybe for excluding pyogenic germs' implication. In addition, K. kingae's OAI respond well even to short antibiotics treatments, and, therefore, the management of these infections requires only short hospitalization, and most of the patients can then be treated safely as outpatients.

The authors report a rare case of an unusual primary pyomyositis of the biceps cruralis assigned to Kingella kingae in a 21-month-old girl. The reported case demonstrated that primary pyomyositis may be encountered during invasive infection due to K. kingae even if this manifestation remains rare. This bacterial etiology must, therefore, be evoked when a primary pyomyositis is observed, and this is in particular in children under 4 years of age.

Background: Hematoma formation and the need for blood transfusions are commonly reported complications after shoulder arthroplasty. Tranexamic acid (TXA) has been widely used in hip and knee arthroplasty to decrease perioperative blood loss. The role of TXA is still being established in shoulder arthroplasty. Materials and methods: We conducted a double-blind randomized controlled trial comparing intravenous TXA vs. placebo in 60 patients undergoing primary anatomic or reverse shoulder arthroplasty. Of these patients, 29 received a placebo whereas 31 received a single dose of 2 g of intravenous TXA. Patient demographic characteristics, as well as drain tube output, blood loss, hematoma formation, transfusion requirement, length of hospital stay, and pain score, were recorded. Patients were followed up for 12 weeks to assess for complications. Results: Patients who received TXA had a lower drain tube output at all time points: 41 mL vs. 133 mL at 6 hours, 75 mL vs. 179 mL at 12 hours, and 94 mL vs. 226 mL at 24 hours (P < .001 for all). They also had a higher postoperative hemoglobin (Hb) level (12.3 g/dL vs. 11.4 g/dL, P = .009), lower change in Hb level (1.7 g/dL vs. 2.3 g/dL, P = .011), lower total Hb loss (0.078 g vs. 0.103 g, P = .042), lower blood volume loss (0.55 L vs. 0.74 L, P = .021), higher postoperative hematocrit level (36.7% vs. 34.6%, P = .020), and lower hematocrit change (5.4% vs. 7.6%, P = .022). There was no significant difference in pain score or length of hospital stay, and no patients required a transfusion. Conclusion: A single dose of 2 g of intravenous TXA decreases blood loss and drain tube output in primary anatomic and reverse arthroplasty of the shoulder. No differences were detected in the occurrence of complications, need for transfusion, pain score, or length of hospital stay. With the mounting evidence now available, patients undergoing elective primary shoulder arthroplasty should be given intravenous TXA to decrease perioperative blood loss. (C) 2021 The Authors.

Aims The aim of this study was to report a retrospective, consecutive series of patients with adolescent idiopathic scoliosis (AIS) who were treated with posterior minimally invasive surgery (MIS) with a mean follow-up of two years (SD 1.4; 0.9 to 0 3.7). Our objectives were to measure the correction of the deformity and record the peri-operative morbidity. Special attention was paid to the operating time (ORT), estimated blood loss (EBL), length of stay (LOS) and further complications. Patients and Methods We prospectively collected the data of 70 consecutive patients with AIS treated with MIS using three incisions and a muscle-splitting approach by a single surgeon between June 2013 and February 2016 and these were retrospectively reviewed. There were eight male and 62 female patients with a mean age of 15 years (SD 4.5) with a mean body mass index of 19.8 kg/m(2) (SD 5.4). The curves were classified according to Lenke; 40 curves were type 1, 15 were type 2, three were type 3, two were type 4, eight were type 5 and two were type 6. Results The mean primary Cobb angle was corrected from 58.9 degrees (SD 12.6 degrees) pre-operatively to 17.7 degrees (SD 10.2 degrees) post-operatively with a mean correction of 69% (SD 20%, p < 0.001). The mean kyphosis at T5 to T12 increased from 24.2 degrees (SD 12.2 degrees) pre-operatively to 30.1 degrees (SD 9.6 degrees, p < 0.001) post-operatively. Peri-operative (30 days) complications occurred in three patients(4.2%): one subcutaneous haematoma, one deep venous thrombosis and one pulmonary complication. Five additional complications occurred in five patients (7.1%): one superficial wound infection, one suture granuloma and three delayed deep surgical site infections. The mean ORT was 337.1 mins (SD 121.3); the mean EBL was 345.7 ml (SD 175.1) and the mean LOS was 4.6 days (SD 0.8). Conclusion The use of MIS for patients with AIS results in a significant correction of spinal deformity in both the frontal and sagittal planes, with a low EBL and a short LOS. The rate of peri-operative complications compares well with that following a routine open technique. The longer term safety and benefit of MIS in these patients needs to be evaluated with further follow-up of a larger cohort of patients.