Persistent inflammation is well known to promote the progression of arthropathy. mesenchymal stem cells (MSCs) have been shown to possess anti-inflammatory properties and tissue differentiation potency. Although the experience so far with the intraarticular administration of mesenchymal stem cell (MSC) to induce cartilage regeneration has been disappointing, MSC implantation is now being attempted using various surgical techniques. Meanwhile, prevention of osteoarthritis (OA) progression and pain control remain important components of the treatment of early-stage OA. We prepared a shoulder arthritis model by injecting monoiodoacetate (MIA) into a rat shoulder, and then investigated the intraarticular administration of MSC from the aspects of the cartilage protective effect associated with their anti-inflammatory property and inhibitory effect on central sensitization of pain. When MIA was administered in this rat shoulder arthritis model, anti-Calcitonin Gene Related Peptide (CGRP) was expressed in the joint and C5 spinal dorsal horn. Moreover, expression of A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), a marker of joint cartilage injury, was similarly elevated following MIA administration. When MSC were injected intraarticularly after MIA, the expression of CGRP in the spinal dorsal horn was significantly deceased, indicating suppression of the central sensitization of pain. The expression of ADAMTS 5 in joint cartilage was also significantly inhibited by MSC administration. In contrast, a significant increase in the expression of TNF-α stimulated gene/protein 6 (TSG-6), an anti-inflammatory and cartilage protective factor shown to be produced and secreted by MSC intraarticularly, was found to extend to the cartilage tissue following MSC administration. In this way, the intraarticular injection of MSC inhibited the central sensitization of pain and increased the expression of the anti-inflammatory and cartilage protective factor TSG-6. As the least invasive conservative strategies possible are desirable in the actual clinical setting, the intraarticular administration of MSC, which appears to be effective for the treatment of pain and cartilage protection in early-stage arthritis, may achieve these aims.

Cemented polished tapered femoral stems (PTS) made of cobalt–chrome alloy (CoCr) are a known risk factor for periprosthetic fracture (PPF). The mechanical differences between CoCr-PTS and stainless-steel (SUS) PTS were investigated. CoCr stems having the same shape and surface roughness as the SUS Exeter^® stem were manufactured and dynamic loading tests were performed on three each. Stem subsidence and the compressive force at the bone–cement interface were recorded. Tantalum balls were injected into the cement, and their movement was tracked to indicate cement movement. Stem motions in the cement were greater for the CoCr stems than for the SUS stems. In addition, although we found a significant positive correlation between stem subsidence and compressive force in all stems, CoCr stems generated a compressive force over three times higher than SUS stems at the bone–cement interface with the same stem subsidence (p < 0.01). The final stem subsidence amount and final force were greater in the CoCr group (p < 0.01), and the ratio of tantalum ball vertical distance to stem subsidence was significantly smaller for CoCr than for SUS (p < 0.01). CoCr stems appear to move more easily in cement than SUS stems, which might contribute to the increased occurrence of PPF with the use of CoCr-PTS.

Mesenchymal stem cells (MSCs) have been transplanted directly into lesions or injected intravenously. The administration of MSCs using these delivery methods requires specialized knowledge, techniques, and facilities. Here, we describe intrarectal systemic administration of MSCs, a simple, non-invasive route for homing to the injury sites to promote the regeneration of skeletal muscle injuries. Using a cardiotoxin (CTX)-induced rabbit skeletal muscle injury model, homing to the site of muscle injury was confirmed by intrarectal administration of MSCs; the time required for homing after intrarectal administration was approximately 5 days. In addition, the C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor-4 (CXCR4) axis was found to be involved in the homing process. Histopathological examinations showed that skeletal muscle regeneration was promoted in the MSCs-administered group compared to the CTX-only group. Myosin heavy polypeptide 3 (Myh3) expression, an indicator of early muscle regeneration, was detected earlier in the intrarectal MSCs group compared to the CTX-only group. These findings indicate that intrarectal administration of MSCs is effective in homing to the injured area, where they promote injury repair. Since intrarectal administration is a simple and non-invasive delivery route, these findings may be valuable in future research on stem cell therapy.

Tendinopathy is an aging-related disease, often caused by micro-scarring and degeneration due to overuse or trauma. Ascorbic acid (vitamin C) supplementation is reported to be a useful treatment for tendinopathy recovery. We compared the inhibitory effects of various ascorbic acid doses on tendon cell damage. H₂O₂ was added to human-derived tendon cells in vitro (Group H₂O₂, control), followed by incubation with 150 µM or 30 mM of ascorbic acid (Group C, Group HC). The oxidative injury degree was evaluated by determining reactive oxygen species levels. The cytoskeletal structure was examined via fluorescence immunostaining of actin filaments. Quantitative polymerase chain reaction (qPCR) was performed to analyze the expressions of mitochondria transcription factor A, adenosine triphosphate 5A, type I collagen, and p16. Cell death was reduced, and oxidative stress was inhibited in C and HC groups. The cytoskeleton was maintained in the HC group but not in the C group. qPCR analysis revealed that p16 expression was inhibited in both the C and HC groups compared to the H₂O₂ group; other markers had increased expression. The progression of cell death and cytoskeletal disruption was inhibited by the administration of high-dose vitamin C. Hence, high-dose vitamin C is a potential treatment for tendon cell degeneration.

After artificial joint surgery, bone density may decrease around the artificial joint; thus, postoperative bone density evaluation around the artificial joint is crucial. We investigated changes in bone mineral density and performed radiographic evaluation around the stem after reverse shoulder arthroplasty (RSA) surgery in 17 males (18 shoulders) and 19 females (19 shoulders), aged >65 years, with >1-year follow-up. In total, 20 and 17 cases involved massive rotator cuff tears and rotator cuff tear arthropathy, respectively. The Comprehensive Reverse Shoulder System (Standard Ingrowth) was used for all cases and cement was used in eight patients due to bone fragility. We examined lucent lines, loosening, bone resorption, and spot welds in non-cemented cases using plain radiography and postoperative bone density changes around the stem using dual-energy X-ray absorptiometry (DEXA). Lucent lines and bone resorption occurred in 5 (13.5%) and 19 (51.4%) shoulders, respectively. No loosening occurred. Compared to stem bone density at 2 weeks postoperatively, the decrease rate was the largest in the proximal medial humerus. One-year postoperative bone density was not related to sex, age, cement use, or preoperative diagnosis. Higher preoperative bone density was better maintained postoperatively. Furthermore, 1 year post RSA, spot welds were observed in approximately 48.2% of cases at the distal medial portion of the stem coating, and bone resorption occurred in the proximal medial humerus in 43.2% of cases. Therefore, postoperative bone density is related to preoperative bone density, suggesting the importance of maintaining high preoperative bone density.

Background: In reverse shoulder arthroplasty (RSA), preservation of the subscapularis (SSC) has gained attention because of its biomechanical and functional significance. However, when SSC preservation is attempted using the conventional deltopectoral (DP) approach, glenoid visualization and instrument access may be limited. The purpose of this Technical Note is to describe a modified deltopectoral exposure technique, hereafter referred to as the Margin-Shifted, Yawing, Subscapularis-Sparing, and Transitioned Lateralized Deltopectoral (MYST–LDP) approach, and to assess its feasibility in primary RSA. Methods: The MYST–LDP approach incorporates a laterally shifted incision apex, a proximally oriented curved arc (“yawing”) toward the acromion, complete preservation of the subscapularis, and a distally transitioned limb aligned with the anterior humeral axis. We describe the surgical technique and our initial experience in three consecutive primary RSA cases performed using an inlay implant system to minimize humeral lateralization and allow focused assessment of exposure geometry. Results: In all cases, the SSC was preserved without conversion to a standard DP exposure. Adequate glenoid visualization was achieved using three retractors without excessive soft-tissue tension, allowing controlled glenoid preparation and component implantation without additional exposure or conversion. No approach-related intraoperative complications were observed. Conclusions: The MYST–LDP approach is a feasible modification of the deltopectoral exposure that preserves both SSC and the deltoid while facilitating glenoid visualization and instrument alignment. This technique represents an ergonomic and tissue-preserving option within the familiar DP framework for surgeons performing SSC-preserving RSA. Further comparative and quantitative studies are warranted to determine its clinical value.