The effect of corticosteroids on tendons is poorly understood, and current data are insufficient and conflicting. To evaluate the effects of corticosteroid injections on intact and injured rotator cuffs (RCs) through biomechanical and radiographic analyses in a rat model. Controlled laboratory study. A total of 70 rats were assigned to 7 groups. Uninjured rats (no tear) received either a single saline injection, a single methylprednisolone acetate (MTA) injection, or triple MTA injections. Injured rats (unilateral supraspinatus injury) received either a single saline injection, triple saline injections, a single MTA injection, or triple MTA injections (injections were subacromial; repeat injections were administered weekly). Rats were sacrificed 1 week after final injection. Shoulders were harvested and grossly inspected, and the supraspinatus tendon was evaluated biomechanically. Bone density at the tendon insertion site on the greater tuberosity was assessed by micro–computed tomography. Intact RCs exposed to triple MTA injections had significantly decreased maximal load and stiffness compared with the control group (14.43 vs 21.25 N and 8.21 vs 16.6 N/mm, respectively; P < .05). Injured RCs exposed to steroid treatment had significantly lower maximal load (single saline: 10.91 N, single steroid: 8.43 N [P < .05]; triple control: 15.77 N, triple steroid: 11.65 N [P < .05]) compared with the control at 3 weeks. Greater tuberosity volume density and connectivity density were significantly lower in undamaged rats after triple MTA injection (P < .05). The study results clearly showed that repeated doses of corticosteroids significantly weaken rat RC and negatively affect bone quality in addition to possibly causing deterioration of the osteotendinous junction. However, data retrieved from animals must be scrupulously analyzed before extrapolation to humans. As such, the potential benefits and harms of subacromial corticosteroid treatment must be considered before administration. The potential benefit and detrimental effects of corticosteroid injection should be thoroughly considered before it is administered subacromially in patients with RC injuries.

Pulsed electromagnetic fields (PEMFs) have been considered a potential treatment modality for fracture healing, however, the mechanism of their action remains unclear. Mammalian target of rapamycin (mTOR) signaling may affect osteoblast proliferation and differentiation. This study aimed to assess the osteogenic differentiation of mesenchymal stem cells (MSCs) under PEMF stimulation and the potential involvement of mTOR signaling pathway in this process. PEMFs were generated by a novel miniaturized electromagnetic device. Potential changes in the expression of mTOR pathway components, including receptors, ligands and nuclear target genes, and their correlation with osteogenic markers and transcription factors were analyzed. Involvement of the mTOR pathway in osteogenesis was also studied in the presence of proinflammatory mediators. PEMF exposure increased cell proliferation and adhesion and the osteogenic commitment of MSCs even in inflammatory conditions. Osteogenic-related genes were over-expressed following PEMF treatment. Our results confirm that PEMFs contribute to activation of the mTOR pathway via upregulation of the proteins AKT, MAPP kinase, and RRAGA, suggesting that activation of the mTOR pathway is required for PEMF-stimulated osteogenic differentiation. Our findings provide insights into how PEMFs influence osteogenic differentiation in normal and inflammatory environments.

Proximal humerus fractures comprise approximately 5% of all fractures, with isolated greater tuberosity fractures accounting for approximately 20% of proximal humerus fractures. Although performing shoulder arthroscopy in situations including a fracture is technically demanding, it allows surgeons the opportunity to identify and treat other coexisting lesions that could have otherwise been missed. The incidence of these pathologies in combination with greater tuberosity fractures has not been established. This study aimed to identify the various types of pathologies that may coexist with greater tuberosity fractures but not be detected before fixation. Displaced 2-part greater tuberosity fractures were treated arthroscopically in the authors’ department. All patients initially underwent diagnostic arthroscopy during which other coexisting pathologies were detected and assessed, including rotator cuff tears, labral tears (Bankart or superior labral anterior posterior lesions), or long head of the biceps pathologies. Twenty-four patients underwent arthroscopic (n=10) or arthroscopic-assisted (n=14) greater tuberosity reduction and fixation. Thirteen (54.2%) fragments were fully displaced. Four (16.7%) patients had fracture dislocation of the glenohumeral joint. The concomitant soft-tissue pathologies were identified and treated arthroscopically in 22 (92%) patients. Arthroscopic evaluation before greater tuberosity fracture fixation revealed a high percentage of concomitant soft tissue pathologies. These pathologies may be overlooked otherwise, but they are easily detected arthroscopically, enabling their treatment during the same procedure.