Objective To analyze the incidence and possible risk factors of the chronic postsurgical pain (CPSP) in patients undergoing cardiac surgery with cardiopulmonary bypass via median sternotomy. Methods A total of 248 cardiac surgery patients (104 males, 144 females with age of 20–74 years) were enrolled in this single-center, prospective observational study. The severity of acute postoperative pain at first 7 days was evaluated by numeric rating scale (NRS) and pain at 30 days after surgery and CPSP at 3 and 6 months after surgery was evaluated with modified brief pain inventory. Results The CPSP at postoperative 6 months occurred in 45.2% (112/248) patients and 24.1% of them suffered moderate to severe pain (NRS≥4). The CPSP at postoperative 3 months occurred in 60.9% (151/248) patients and 25.8% of them suffered moderate to severe pain. Moderate to severe postoperative pain at postoperative 30 days and 3 months, and intraoperative remifentanil infusion were the risk factors of the CPSP at postoperative 6 months. Conclusion CPSP is common in patients undergoing cardiac surgery with median sternotomy. Moderate to severe postoperative pain at 30 days and 3 months, and intraoperative remifentanil infusion can predict the presence of CPSP at 6 months.
Although metal blocks have been widely used for reconstructing uncontained tibial bone defects, the influence of their elastic modulus on the stability of tibial prosthesis fixation remains unclear. Based on this, a finite element model incorporating constrained condylar knee (CCK) prosthesis, tibia, and metal block was established. Considering the influence of the post-restraint structure of the prosthesis, the effects of variations in the elastic modulus of the block on the von Mises stress distribution in the tibia and the block, as well as on the micromotion at the bone-prosthesis fixation interface, were investigated. Results demonstrated that collision between the insert post and femoral prosthesis during tibial internal rotation increased tibial von Mises stress, significantly influencing the prediction of block elastic modulus variation. A decrease in the elastic modulus of the metal block resulted in increased von Mises stress in the proximal tibia, significantly reduced von Mises stress in the distal tibia, decreased von Mises stress of the block, and increased micromotion at the bone-prosthesis fixation interface. When the elastic modulus of the metal block fell below that of bone cement, inadequate block support substantially increased the risk of stress shielding in the distal tibia and fixation interface loosening. Therefore, this study recommends that biomechanical investigations of CCK prostheses must consider the post-constraint effect, and the elastic modulus of metal blocks for bone reconstruction should not be lower than 3 600 MPa.