Finite Element Analysis of Coronal Shear Fractures of the Femoral Neck: Displacement of the Femoral Head and Effect of Osteosynthetic Implants

Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynthesis method has not been elucidated yet. This study investigated the displacement direction of the femoral head fragment and its effect on the bone using finite element method. A finite element model for CSFF was developed from CT image data of a patient with osteoporosis using Mechanical Finder (ver. 11). Subsequently, finite element analyses were performed on six osteosynthesis models under maximum load applied during walking. The compressive stresses, tensile stresses, and compressive strains of each model were examined. The results suggested that the compressive and tensile stress distributions were concentrated on the anterior side of the femoral neck. Compressive strain distribution in the femoral head and neck was concentrated in four areas: at the tip of the blade or lag screw, the anteroinferior side of the blade or lag screw near the fracture site, and the upper right and lower left near the junction of the blade or lag screw and nail. Thus, the distribution of both these stresses revealed that the femoral head fragment was prone to anterior and inferior displacement. Distribution of compressive strains revealed the direction of the stress exerted by the osteosynthetic implant on the bone. The same results were observed in all osteosynthetic implants;thus, the findings could lay the foundation for developing methods for placing osteosynthetic implants less prone to displacement and the osteosynthetic implants themselves. In particular, the study provides insight into the optimal treatment of CSFF.

Application of proximal femur locking compression plate for unstable four part intertrochanteric fractures

Objective To evaluate the clinical results of proximal femur locking compression plate (LCP) for unstable four-part intertrochanteric femoral fractures.Methods Clinical data of53patients wiith unstable four-part intertrochanteric

Total hip arthroplasty following the failure of intertrochanteric nailing:First implant or salvage surgery?

BACKGROUND Proximal femur fractures,including both intracapsular(femoral neck fractures)and extracapsular fractures(intertrochanteric femoral fractures,IFFs),affect around 1.5 million people per year worldwide.Mechanical failures of intertrochanteric nailing in IFFs could be managed with revision total hip arthroplasty(THA).AIM To describe the surgical complexity and the procedure-related complication rates in patients with trochanteric nailing failure and treated with THA.METHODS Patients referred to our level I trauma center between April 2012 and July 2018 with failed cephalomedullary nailing following trochanteric fractures were retrospectively recruited.All patients underwent a salvage surgical procedure,i.e.,cephalomedullary nail removal and conversion to THA.The same surgical and anesthesiology team performed the surgical procedures under spinal anesthesia.All patients underwent clinical and radiographic follow-ups for at least 24 mo.Complications and re-operations were recorded.RESULTS Seventy-four patients met the inclusion criteria(male:29;female:45;mean age:73.8-years-old;range:65-89)and were included in the current study.The average operative time was 117 min(76-192 min).The average blood loss was 585 mL(430-1720 mL).Among the 74 patients,43(58.1%)required transfusion of three or more blood units.Two patients died within the 4th d after surgery because of pulmonary embolism,and 1 patient died 9 mo after surgery due to ischemic myocardial infarction.The complication rate in the 71 patients who completed the minimum 24-mo follow-up was 22.5%.In 3 cases out of 71(4.2%)periprosthetic acetabular fracture was observed during the followup.One of these periacetabular fractures occurred intraoperatively.An intraoperative periprosthetic femur fracture was observed in 5 patients out of 71(7.0%).Four of these patients needed a re-operation to fix the fracture with plates and cerclages;in one of these patients,femoral stem revision was also necessary.In 4 patients out of 71(5.6%),an early THA dislocation was observed,whereas in 1 case(1.4%)a late THA dislocation was observed.Three patients out of 71(4.2%)developed a periprosthetic joint infection during the study follow-up.CONCLUSION The present study demonstrated that salvage options for IFF fixation failure are complex procedures with a relevant intraoperative and postoperative complication rate.

Regional Variations in Trabecular Morphological Features of Femoral Head of Patients with Proximal Femoral Fractures

The regional microstructural variations in femoral head from proximal femoral fracture patients were investigated. Mi- cro-CT scanning was performed on seven femoral heads from proximal femoral fracture patients. Each femoral head was divided into three regions according to the trabecular orientation from the fovea of femoral head to the femoral neck. Eight three-dimensional trabecular cube models were reconstructed from each region. A total of 154 trabecular cubic models were reconstructed because the corresponding areas for 14 cubic models were damaged during the surgeries. Eight trabecular mor- phological parameters were measured and analyzed, namely, trabecular thickness （Tb.Th）, trabecular separation （Tb.Sp）, spe- cific bone surface （BS/BV）, bone volum在不 fraction （BV/TV）, structural model index （SMI）, degree of anisotropy （DA）, trabecular pattern factor （Tb.Pf）, and trabecular number （Tb.N）. Bivariate correlation analyses were performed for all mor- phological parameters. One-way ANOVA tests were performed to analyze the differences of each parameter among three re- gions. Post-hoc multiple comparisons （Student-Newman-Keuls method） were performed to analyze the morphological differ- ence between two regions. Trabecular bone of proximal femoral fracture patients significantly degenerated in all regions of femoral heads. BV/TV was statistically correlated with Tb.Th, Tb.Sp, BS/BV, Tb.Pf, and Tb.N （p 〈 0.05）. Statistical differences in morphological parameters were observed between regions （p 〈 0.05）. The trabecular strength in the middle regions was significantly higher than that in other regions because of the relationships between morphological parameters and mechanical parameters. Trabeculae in the medial region were more uniform and stable along each direction than those in the lateral region. Most trabeculae in the lateral region only grew along the weight-bearing direction, and those along the other directions de- generated significantly. This study provides detailed trabecular morphological information on fractured femoral heads, as well as references for the prevention of high fracture risk in the elderly.