Symmetry and structure of carbon-nitrogen complexes in gallium arsenide from infrared spectroscopy and first-principles calculations

Molecular-like carbon-nitrogen complexes in GaAs are investigated both experimentally and theoretically. Two characteristic high-frequency stretching modes at \num{1973} and \SI{2060}{cm^{-1}}, detected by Fourier transform infrared absorption (FTIR) spectroscopy, appear in carbon- and nitrogen-implanted and annealed layers. From isotopic substitution it is deduced that the chemical composition of the underlying complexes is CN$_2$ and C$_2$N, respectively. Piezospectroscopic FTIR measurements reveal that both centers have tetragonal symmetry. For density functional theory (DFT) calculations linear entities are substituted for the As anion, with the axis oriented along the \hkl direction, in accordance with the experimentally ascertained symmetry. The DFT calculations support the stability of linear N-C-N and C-C-N complexes in the GaAs host crystal in the charge states ranging from $+3$ to $-3$. The valence bonds of the complexes are analyzed using molecular-like orbitals from DFT. It turns out that internal bonds and bonds to the lattice are essentially independent of the charge state. The calculated vibrational mode frequencies are close to the experimental values and reproduce precisely the isotopic mass splitting from FTIR experiments. Finally, the formation energies show that under thermodynamic equilibrium CN$_2$ is more stable than C$_2$N

Bone graft substitutes and bone morphogenetic proteins for osteoporotic fractures: What is the evidence?

Despite improvements in implants and surgical techniques, osteoporotic fractures remain challenging to treat. Among other major risk factors, decreased expression of morphogenetic proteins has been identified for impaired fracture healing in osteoporosis. Bone grafts or bone graft substitutes are often used for stabilizing the implant and for providing a scaffold for ingrowth of new bone. Both synthetic and naturally occurring biomaterials are available. Products generally contain hydroxyapatite, tricalcium phosphate, dicalcium phosphate, calcium phosphate cement, calcium sulfate (plaster of Paris), or combinations of the above. Products have been used for the treatment of osteoporotic fractures of the proximal humerus, distal radius, vertebra, hip, and tibia plateau. Although there is generally consensus that screw augmentation increased the biomechanical properties and implant stability, the results of using these products for void filling are not unequivocal. In osteoporotic patients, Bone Morphogenetic Proteins (BMPs) have the potential impact to improve fracture healing by augmenting the impaired molecular and cellular mechanisms. However, the clinical evidence on the use of BMPs in patients with osteoporotic fractures is poor as there are no published clinical trials, case series or case studies. Even pre-clinical literature on in vitro and in vivo data is weak as most articles focus on the beneficial role for BMPs for restoration of the underlying pathophysiological factors of osteoporosis but do not look at the specific effects on osteoporotic fracture healing. Limited data on animal experiments suggest stimulation of fracture healing in ovariectomized rats by the use of BMPs. In conclusion, there is only limited data on the clinical relevance and optimal indications for the use of bone graft substitute materials and BMPs on the treatment of osteoporotic fractures despite the clinical benefits of these materials in other clinical indications. Given the general compromised outcome in osteoporotic fractures and limited alternatives for enhancement of fracture healing, clinicians and researchers should focus on this important topic and provide more data in this field in order to enable a sound clinical use of these materials in osteoporotic fractures

Bilateral septic arthritis with rapid progressive destruction of the femoral head after joint injection in rheumatoid arthritis

This report is on a 61-year-old patient with steroid therapy for rheumatoid arthritis and pain in the groin on both sides who got injections with hyaluronic acid in both hip joints. After 12 weeks the X-ray of the pelvis showed rapid progressive destruction of both hip joints

Treatment of bone infections in children in low-income countries – A practical guideline based on clinical cases

In low-income countries (LIC), the management of bone infections is a huge challenge. A high number of patients are in the pediatric age group. Children and adolescents exhibit good bone healing potential offering treatment options that mainly rely on the biological response of the infected bone. The purpose of this article is to highlight treatment options for these patients in LIC, which is based on clinical cases that illustrate the principles of the treatment, focusing on bone reaction and healing potential. First, identification of emergency cases is of importance. Sepsis of the patient due to bone infections is a lifethreatening disease that requires immediate surgical attention with abscess incision. It should be tailored to the surgeon’s experience and local conditions to avoid unwanted complications, such as excessive bleeding, fracture or bone loss. In non-septic patients, uncomplicated cases should be distinguished from complicated cases as the first might often require only abscess incision, particularly in small children, without any other major surgical intervention. Biomechanical stability and bone formation capacity, soft tissue conditions and joint involvement are decisive factors differentiating uncomplicated from complicated cases. Central treatment column is the immobilization of the infected bone with simple methods, such as plaster of Paris, braces or external fixation. This is intended to provide sufficient stability to allow for new bone formation that subsequently downsizes the infection site and that can bridge previously infected non-union sites or bone defects. In most cases, antibiotic treatment is not performed as antibiotics are not available or affordable. Severe soft tissue defects remain a major challenge as microvascular surgical experience is often required for reliable coverage, for which referral to one of the very few specialized centers is recommended. Major bone defects should also be treated in centers with sufficient expertise for bone reconstruction procedures. Regular follow-ups are important to ensure healing and to avoid aggravation of the disease. Encouraging success rates can be achieved by these treatment principles. However, it should not be forgotten that poverty in these countries, including limited access to health care, remains one of the world’s most important problems

Aged Tendon Stem/Progenitor Cells Are Less Competent to Form 3D Tendon Organoids Due to Cell Autonomous and Matrix Production Deficits

Tendons are dense connective tissues, which are critical for the integrity and function of our musculoskeletal system. During tendon aging and degeneration, tendon stem/progenitor cells (TSPCs) experience profound phenotypic changes with declined cellular functions that can be linked to the known increase in complications during tendon healing process in elderly patients. Tissue engineering is a promising approach for achieving a complete recovery of injured tendons. However, use of autologous cells from aged individuals would require restoring the cellular fitness prior to implantation. In this study, we applied an established cell sheet model for in vitro tenogenesis and compared the sheet formation of TSPC derived from young/healthy (Y-TSPCs) versus aged/degenerative (A-TSPCs) human Achilles tendon biopsies with the purpose to unravel differences in their potential to form self-assembled three-dimensional (3D) tendon organoids. Using our three-step protocol, 4 donors of Y-TSPCs and 9 donors of A-TSPCs were subjected to cell sheet formation and maturation in a period of 5 weeks. The sheets were then cross evaluated by weight and diameter measurements; quantification of cell density, proliferation, senescence and apoptosis; histomorphometry; gene expression of 48 target genes; and collagen type I protein production. The results revealed very obvious and significant phenotype in A-TSPC sheets characterized by being fragile and thin with poor tissue morphology, and significantly lower cell density and proliferation, but significantly higher levels of the senescence-related gene markers and apoptotic cells. Quantitative gene expression analyses at the mRNA and protein levels, also demonstrated abnormal molecular circuits in the A-TSPC sheets. Taken together, we report for the first time that A-TSPCs exhibit profound deficits in forming 3D tendon tissue organoids, thus making the cell sheet model suitable to investigate the molecular mechanisms involved in tendon aging and degeneration, as well as examining novel pharmacologic strategies for rejuvenation of aged cells

Severe acidosis due to 5-oxoprolinase inhibition by flucloxacillin in a patient with shoulder prosthesis joint infection

We report a case of a 64-year-old female patient with severe metabolic acidosis. Inhibition of 5-oxoprolinase by flucloxacillin was found to be the cause of the metabolic derailment

Evaluation of Comorbidities as Risk Factors for Fracture-Related Infection and Periprosthetic Joint Infection in Germany

Introduction: Fracture-related infections (FRI) and periprosthetic joint infections (PJI) represent a major challenge in orthopedic surgery. Incidence of both entities is annually growing. Comorbidities play an important role as an influencing factor for infection and thus, for prevention and treatment strategies. The aims of this study were (1) to analyze the frequency of comorbidities in FRI and PJI patients and (2) to evaluate comorbidities as causative risk factor for PJI and FRI. Methods: This retrospective cohort study analysed all ICD-10 codes, which were coded as secondary diagnosis in all in hospital-treated FRI and PJI in the year 2019 in Germany provided by the Federal Statistical Office of Germany (Destatis). Prevalence of comorbidities was compared with the prevalence in the general population. Results: In the year 2019, 7158 FRIs and 16,174 PJIs were registered in Germany, with 68,304 comorbidities in FRI (mean: 9.5 per case) and 188,684 in PJI (mean: 11.7 per case). Major localization for FRI were infections in the lower leg (55.4%) and forearm (9.2%), while PJI were located mostly at hip (47.4%) and knee joints (45.5%). Mainly arterial hypertension (FRI: n = 3645; 50.9%—PJI: n = 11360; 70.2%), diabetes mellitus type II (FRI: n = 1483; 20.7%—PJI: n = 3999; 24.7%), obesity (FRI: n = 749; 10.5%—PJI: n = 3434; 21.2%) and chronic kidney failure (FRI: n = 877; 12.3%—PJI: n = 3341; 20.7%) were documented. Compared with the general population, an increased risk for PJI and FRI was reported in patients with diabetes mellitus (PJI: 2.988; FRI: 2.339), arterial hypertension (PJI: 5.059; FRI: 2.116) and heart failure (PJI: 6.513; FRI: 3.801). Conclusion: Patients with endocrinological and cardiovascular diseases, in particular associated with the metabolic syndrome, demonstrate an increased risk for orthopedic implant related infections. Based on the present results, further infection prevention and treatment strategies should be evaluated

Comment on Lunz et al. Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections. J. Clin. Med. 2023, 12, 1262

We read with great interest the article by Lunz et al. [1], in which the authors dealt with the new Periprosthetic Joint Infection (PJI)-TNM classification that was recently published by our group (Table 1) [2–4]. PJI represents one of the most feared complications in the orthopedic field, resulting in impaired quality of life, repeated and prolonged hospital stays, and significant morbidity and mortality in affected patients. Still, there is no commonly used classification system that could facilitate the comparison of treatment strategies and patient outcomes [5,6]. Therefore, we are delighted with the authors’ conclusions that “clinicians and researchers should be familiar with the new PJI-TNM classification and start implementing it into their routine practice” [1]. The work of Lunz et al. [1] retrospectively assessed 80 consecutive PJI patients treated with a two-stage exchange and was the first to correlate the PJI-TNM classification to surgical parameters and some clinical outcome parameters, such as need for revision surgery after stage one surgery, the duration of the interim period, and mortality. In addition, Lunz et al. [1] believed that the initial PJI-TNM publication from our group could be improved through certain modifications to the TNM backbone, resulting in a “pTNM” version. An additional “p-status” (type of prosthesis) was proposed to distinguish between standard implants (p0), revision implants (p1), and megaprostheses (p2). Further suggestions were to add an “x” in front of the “p-status” to indicate a loosened implant and to limit the criteria parameters for p, T, N, and M to only 0 = least serious, 1 = moderate, and 2 = most serious by eliminating the letters for the subclassifications of the 0, 1, and 2 categories of our initially proposed classification. They also proposed the replacement of the CCI for the assessment of patients’ comorbidities with the American Society of Anesthesiologists (ASA) Physical Status Classification System [7]

Treatment of Fracture-Related Infections with Bone Abscess Formation after K-Wire Fixation of Pediatric Distal Radius Fractures in Adolescents—A Report of Two Clinical Cases

Abstract Closed reduction and K-wire fixation of displaced distal radius fractures in children and adolescents is an established and successful surgical procedure. Fracture-related infections after K-wire fixation are rare but can have significant consequences for the patient. There is a lack of literature on the treatment of K-wire-associated fracture-related infections in children and adolescents. Herein, we report two cases of fracture-related infection after initial closed reduction and Kirschner wire fixation in two adolescents. One 13-year-old boy and one 11-year-old girl were seen for fracture-related infections 4 and 8 weeks after closed reduction and percutaneous K-wire fixation of a distal radius, respectively. X-ray and magnetic resonance imaging (MRI) revealed a healed fracture with osteolytic changes in the metaphyseal radius with periosteal reaction and abscess formation of the surrounding soft tissue structures. A two-staged procedure was performed with adequate debridement of the bone and dead space management with an antibiotic-loaded polymethyl methacrylate (PMMA) spacer at stage 1. After infection control, the spacer was removed and the defect was filled with autologous bone in one case and with a calcium sulphate–hydroxyapatite biomaterial in the other case. In each of the two patients, the infection was controlled and a stable consolidation of the distal radius in good alignment was achieved. In one case, the epiphyseal plate was impaired by the infection and premature closure of the epiphyseal plate was noted resulting in a post-infection ulna plus variant. In conclusion, a fracture-related infection after Kirschner wire fixation of pediatric distal radius fractures is a rare complication but can occur. A two-stage procedure with infection control and subsequent bone defect reconstruction was successful in the presented two cases. Premature closure of the epiphyseal growth plate of the distal radius is a potential complication