The global increase in femoral neck fractures due to aging and osteoporosis is a major clinical challenge. The debate on the optimal surgical intervention for femoral neck fractures remains unresolved. This large-scale study explores femoral neck fractures among the elderly, focusing on the comparative outcomes of Total Hip Arthroplasty (THA) versus Bipolar Hemiarthroplasty (BHA) in Japanese patients. Using the Japanese National Administrative Diagnosis Procedure Combination (DPC) database, we studied cases of femoral neck fracture from April 2016 to March 2023, and after propensity score matching by age, sex, and comorbidities, we examined the association between THA, complications, and clinical outcomes, and the usefulness of THA for elderly patients with femoral neck fracture. One-to-one propensity score matching identified 7741 pairs of THA and BHA cases. There was no difference in length of stay between the THA and BHA groups. Significantly more blood transfusions were required in the THA group. There was no significant difference in mortality between the THA and BHA groups, but there was a reduced risk of pneumonia in the THA group, with a ratio of 0.547 (95% CI: 0.418-0.715). On the other hand, the THA group had a higher risk of pulmonary embolism, with a ratio of 1.607 (95% CI: 1.379-1.874). The THA group shows improved discharge rates directly home from the facility where the operation was performed, with a ratio of 1.798 (95% CI: 1.675-1.929). The findings of this research indicate that THA is more effective than BHA in enabling elderly Japanese patients with femoral neck fractures to be discharged directly home and in preventing pneumonia, despite concerns about pulmonary embolism. These findings suggest that THA may improve functional prognosis in elderly patients with femoral neck fractures, although there is a trade-off with an increased risk of pulmonary embolism.

Osteonecrosis of the femoral head (ONFH) and osteoarthritis (OA) are two common diagnoses for patients undergoing total hip arthroplasty (THA). The early surgical complications in THA for ONFH compared to OA are inconsistently reported. Therefore, this study aimed to evaluate whether THA for ONFH was associated with early postoperative complications in comparison to THA for OA using a large database of Japanese patients. In this cohort study, using a Japanese national medical claims database on ONFH and OA patients undergoing THA from December 2011 to March 2023, we assessed the surgical-related complications, medical complications, and mortality during hospitalization after propensity score matching by age, sex, body mass index, and comorbidities. A total of 24,326 pairs of THAs for ONFH and OA were included. In the THA for ONFH group, the odds ratios for various complications were as follows: dislocation (1.3, 95% CI [confidence interval]: 1.1 to 1.6, P < 0.01), infection (1.0, 95% CI: 0.8 to 1.2, P = 0.94), periprosthetic fracture (1.0, 95% CI: 0.8 to 1.4, P = 0.86), nerve palsy during hospitalization (0.4, 95% CI: 0.2 to 0.9, P = 0.034), pneumonia (1.7, 95% CI: 1.1 to 2.5, P < 0.01), deep vein thrombosis (0.9, 95% CI: 0.8 to 1.0, P = 0.018), pulmonary embolism (1.5, 95% CI: 0.9 to 2.5, P = 0.14), cardiac events (0.7, 95% CI: 0.3 to 2.1, P = 0.55), cerebrovascular events (0.7, 95% CI: 0.5 to 1.0, P = 0.084), acute renal failure (1.4, 95% CI: 0.4 to 4.4, P = 0.56), and mortality during hospitalization (1.8, 95% CI: 1.3 to 2.4, P < 0.01). These findings contribute to identifying postoperative risks for ONFH patients and suggest that more attention should be paid to preoperative planning and postoperative care for ONFH patients.

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Stress shielding remains a major concern in cementless total hip arthroplasty (THA) due to the stiffness mismatch between femoral stems and surrounding bone. This study investigated the biomechanical and clinical performance of a novel Ti-33.6Nb-4Sn (Ti-Nb-Sn) alloy stem with a graded Young’s modulus achieved through localized heat treatment. A finite element model (FEM) of the Ti-Nb-Sn stem, incorporating experimentally validated Young’s modulus gradients, was constructed and implanted into a patient-specific femoral model. Stress distribution and micromotion were assessed under physiological loading conditions. Clinical validation was performed by evaluating radiographic outcomes at 1 and 3 years postoperatively in 40 patients who underwent THA using the Ti-Nb-Sn stem. FEM analysis showed low micromotion at the proximal press-fit region (4.89 μm rotational and 11.74 μm longitudinal), well below the threshold for osseointegration and loosening. Stress distribution was concentrated in the proximal region, effectively reducing stress shielding distally. Clinical results demonstrated minimal stress shielding, with no cases exceeding Grade 3 according to Engh’s classification. The Ti-Nb-Sn stem with a gradient Young’s modulus provided biomechanical behavior closely resembling in vivo conditions and showed promising clinical results in minimizing stress shielding. These findings support the clinical potential of modulus-graded Ti-Nb-Sn stems for improving implant stability in THA.

Introduction: Total knee arthroplasty (TKA) is a widely used treatment for advanced knee osteoarthritis. While cemented fixation is the standard technique, cementless fixation has demonstrated comparable long-term outcomes. However, the association between cement use and postoperative complications, including venous thromboembolism and surgical site infections, remains unclear, particularly in Japanese patients. This study aimed to investigate the incidence of postoperative complications in cemented and cementless TKA using a nationwide database. Methods: A nationwide cohort study was conducted using Japan’s DPC database from April 2016 to March 2023. Patients who underwent TKA were identified, and postoperative complications, including deep vein thrombosis, pulmonary embolism, pneumonia, cerebrovascular events, postoperative cognitive dysfunction, and surgical site infection, were analyzed. One-to-one propensity score (PS) matching was performed based on age, sex, body mass index, type of anesthesia, simultaneous bilateral surgery, Charlson comorbidity index, and comorbidities to ensure comparability. Statistical analyses included χ² tests, Student’s t-tests, and multivariate logistic regression analysis. Results: A total of 228,595 patients met the eligibility criteria, with 21,906 matched pairs in the cemented and cementless groups after PS matching. The incidence of deep vein thrombosis (OR: 1.231, 95% CI: 1.151–1.316, p < 0.0001) and surgical site infection (OR: 1.716, 95% CI: 1.420–2.073, p < 0.0001) was significantly higher in the cemented group. No significant differences were observed in pulmonary embolism or other complications. Conclusion: Cement application was associated with an increased risk of deep vein thrombosis and surgical site infection. These findings suggest that careful perioperative management may be warranted in patients undergoing cemented TKA.