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Background: In recent years, the use of tapered-wedge short stems has increased due to their ability to preserve bones and tendons. Surgical techniques occasionally result in a varus position of the stem, which is particularly pronounced in short stems. Although the varus position is not clinically problematic, there are reports of an increased incidence of stress shielding and cortical hypertrophy. Thus, we evaluated and examined the acceptable range of varus angles using finite element analysis., Methods: Patients diagnosed with osteoarthritis of the hip joint who had undergone arthroplasty were selected and classified into three types [champagne-flute (type A), intermediate (type B), and stovepipe (type C)]. Finite element analysis was performed using Mechanical Finder. The model was created using a Taperloc microplasty stem with the varus angle increased by 1° from 0° to 5° from the bone axis and classified into seven zones based on Gruen's zone classification under loading conditions in a one-leg standing position. The volume of interest was set, the mean equivalent stress for each zone was calculated., Results: A significant decrease in stress was observed in zone 2, and increased stress was observed in zones 3 and 4, suggesting the emergence of a distal periosteal reaction, similar to the results of previous studies. In zone 2, there was a significant decrease in stress in all groups at a varus angle ≥ 3°. In zone 3, stress increased from ≥ 3° in type B and ≥ 4° in type C. In zone 4, there was a significant increase in stress at varus angles of ≥ 2° in types A and B and at ≥ 3° in type C., Conclusion: In zone 2, the varus angle at which stress shielding above Engh classification grade 3 may appear is expected to be ≥ 3°. Distal cortical hypertrophy may appear in zones 3 and 4; the narrower the medullary cavity shape, the smaller the allowable angle of internal recession, and the wider the medullary cavity shape, the wider the allowable range. Long-term follow-up is required in patients with varus angles > 3°., (© 2024. The Author(s).)

Introduction: Treatment of femoral neck fractures in young adults may require total hip arthroplasty or hip hemiarthroplasty using a bipolar cup. The latter can, however, result in migration of the femoral head and poor long-term results., Case Presentation: We report a case of femoral head migration after hemiarthroplasty performed for femoral neck fracture that had occurred 22 years earlier, when the patient (a Japanese man) was 20 years old. He experienced peri-prosthetic fracture of the femur, subsequent migration of the prosthesis, and a massive bone defect of the pelvic side acetabular roof. After bone union of the femoral shaft fracture, the patient was referred to our hospital for reconstruction of the acetabular roof. Intra-operatively, we placed two alloimplants of bone from around the transplanted femoral head into the weight-bearing region of the acetabular roof using an impaction bone graft method. We then implanted an acetabular roof reinforcement plate and a cemented polyethylene cup in the position of the original acetabular cup. Eighteen months post-operatively, X-rays showed union of the transplanted bone., Conclusions: Treatment of femoral neck fractures in young adults is usually accomplished by osteosynthesis, but it may be complicated by femoral head avascular necrosis or by infection or osteomyelitis. In such cases, once an infection has subsided, either hip hemiarthroplasty using a bipolar cup or total hip arthroplasty may be required. However, if the acetabular side articular cartilage is damaged, a bipolar cup should not be used. Total hip arthroplasty should be performed to prevent migration of the implant.

Background: Pulmonary thromboembolism after upper extremity operation is rare. We report a patient with thromboembolism after debridement open reduction and internal fixation for bilateral open distal radius fractures., Case Presentation: The Japanese patient was an 80-year-old previously healthy female who was able to walk on her own. She fell down and was taken to our hospital. She was diagnosed with bilateral open distal radius fractures and we performed debridement open reduction and internal fixation on the same day. Although she could not walk and was depressed, she was discharged on the ninth postoperative day. However, on the eleventh postoperative day, she returned to our emergency department with complaints of dyspnea and cold sweat. Her serum D-dimer level was 19.0 μg/dl, troponin T was positive, and urgent contrast computed tomography scan of her thorax revealed thrombosis in the bilateral main pulmonary artery. She was diagnosed with pulmonary thromboembolism and admitted to our hospital again. On the second admission, although she had breathing problems, she did not require a respirator. Oxygen was supplied as well as anticoagulants. On the seventh day after being diagnosed with embolism, thrombosis in the bilateral main pulmonary arteries had disappeared., Conclusion: The patient did not have any "strong" risk factors as reported in the Japanese Orthopedic Association Clinical Practice Guideline on the Prevention of Venous Thromboembolism in Patients Undergoing Orthopedic Treatments. In general, upper extremity operation carries a low risk for pulmonary thromboembolism. For patients with decreased activity of daily living and depression, we should consider postponing discharge and performing rehabilitation until activity of daily living is improved.