Osteoclasts, multinucleated cells of myeloid-monocytic origin, are responsible for bone resorption, which is crucial for maintenance of bone homeostasis in concert with bone-forming osteoblasts of nonhematopoietic, mesenchymal origin. Receptor activator of NF-κB ligand (RANKL) and M-CSF, expressed on the surface of and secreted by osteoblasts, respectively, are essential factors that facilitate osteoclast formation. In contrast to the activation processes for osteoclast formation, inhibitory mechanisms for it are poorly understood. Herein we demonstrate that inhibitory Ig-like receptors recruiting Src homology 2 domain-containing tyrosine phosphatase 1 (SHP-1) are expressed on osteoclast precursor cells like other myeloid cells, and that they play a regulatory role in the development of osteoclasts. We detected cell-surface expression of paired Ig-like receptor (PIR)-B and four isoforms of leukocyte Ig-like receptor (LILR)B on cultured osteoclast precursor cells of mouse and human origin, respectively, and showed that all of these ITIM-harboring inhibitory receptors constitutively recruit SHP-1 in the presence of RANKL and M-CSF, and that some of them can suppress osteoclast development in vitro. Fluorescence energy transfer analyses have suggested that the constitutive binding of either murine PIR-B or its human ortholog LILRB1 to MHC class I molecules on the same cell surface comprises one of the mechanisms for developmental regulation. These results constitute the first evidence of the regulation of osteoclast formation by cell-surface, ITIM-harboring Ig-like receptors. Modulation of these regulatory receptors may be a novel way to control various skeletal system disorders and inflammatory arthritis.

The purpose of this study was to facilitate the understanding of the SAPHO (Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis) syndrome by analyzing the clinical and radiological features of 67 Japanese patients with SAPHO syndrome. Sixty-seven Japanese patients (female/male: 44/23, mean age at onset: 48.5 years) were diagnosed with SAPHO syndrome from 2002 to 2013 at our hospital. Medical records and radiological imaging of these patients were retrospectively reviewed. Among the 67 patients, 41 had dermatological manifestations, such as palmoplantar pustulosis, acne, and psoriasis. Initial symptom was local pain in all patients, and the most common initial site of the symptom was the anterior chest. Bacterial and fungal cultures from 20 bone biopsies were all negative. Histopathological diagnosis of the specimens was non-specific inflammation in all cases. Bone lesions were observed in 65 patients (97.0%). On the other hand, articular lesions including enthesitis were found in 31 patients (46.2%). SAPHO syndrome had different clinical and radiological aspects. The clinical features were not remarkable, except the dermatological manifestations and the involvement of the anterior chest. Bone lesions including hyperostosis and osteitis were found radiographically in the majority of patients with SAPHO syndrome. These are the characteristics of the SAPHO syndrome, with the exclusion of other bone diseases.

Introduction: The efficacy of early surgery in preventing complications among Japanese elderly patients with hip fractures requires further investigation. This study aims to use a comprehensive Japanese hip fracture case database to determine whether surgery within the day of admission and the following day reduces the incidence of complications and mortality during hospitalization in elderly hip fracture patients. Materials and methods: We retrospectively analyzed the Japanese National Administrative DPC (Diagnosis Procedure Combination) database from April 2016 to March 2022. Approximately 1100 DPC-affiliated hospitals consistently provided medical records with consent for research. The study investigated the association between postoperative pneumonia, deep vein thrombosis, pulmonary embolism, and mortality during hospitalization after propensity score matching, focusing on surgeries conducted on the day of admission and the following day. Results: After one-to-one propensity score matching for age, gender, and comorbidity, we identified 146,441 pairs of patients who underwent surgery either within the day of admission and the following day or after the third day of admission. Surgery on the third day or later was independently associated with increased risks of pneumonia, deep vein thrombosis, pulmonary embolism, and mortality during hospitalization with risk ratios of 1.367 (95% CI 1.307–1.426), 1.328 (95% CI 1.169–1.508), 1.338 (95% CI 1.289–1.388), and 1.167 (95% CI 1.103–1.234), respectively. Conclusion: A comprehensive study of elderly Japanese patients with hip fractures in the DPC database showed that surgery on admission and the following day is crucial for preventing complications like pneumonia, deep vein thrombosis, pulmonary embolism, and mortality during hospitalization.

The bone healing process is influenced by various physiological factors. Fracture fixation traditionally relied on rigid metallic implants. However, excessively rigid constructs can lead to complications, necessitating revision surgery. This review focuses on approaches to improve bone healing by introducing adequate interfragmentary movement (IFM) at the fracture site. IFM promotes secondary fracture healing and callus formation. Studies suggest that rigid fixation may impair fracture healing by inhibiting callus formation and causing stress shielding. Titanium alloy locking plates have been shown to be biomechanically superior to stainless steel. Flexible fixation and techniques to regulate implant stiffness are crucial for managing fractures with bridge plating. Materials with a lower Young’s modulus balance biomechanical properties. A novel TiNbSn alloy with a low Young’s modulus has been developed to address stress shielding issues. It is effective in promoting osteosynthesis, bone healing, and superior mechanical properties compared with materials with higher Young’s moduli. The enhanced formation of bone and callus associated with TiNbSn alloy suggests its promise for use in fracture treatment plates. Understanding the biomechanics of fracture healing, optimizing fixation stiffness, and exploring innovative materials like TiNbSn alloys, are crucial for advancing approaches to accelerate and enhance bone healing.