UNASSIGNED: Conventional cephalomedullary nails (CMNs) are commonly employed for internal fixation in the treatment of reverse obliquity intertrochanteric (ROI) fractures. However, the limited effectiveness of conventional CMNs in addressing ROI fractures results in significant implant-related complications. To address challenges associated with internal fixation, a novel Proximal Femoral Bionic Nail (PFBN) has been developed.
UNASSIGNED: In this study, a finite element model was constructed using a normal femoral specimen, and biomechanical verification was conducted using the GOM non-contact optical strain measurement system. Four intramedullary fixation approaches-PFBN, Proximal Femoral Nail Antirotation InterTan nail (ITN), and Gamma nail (Gamma nail)-were employed to address three variations of ROI fractures (AO/OTA 31-A3). The biomechanical stability of the implant models was evaluated through the calculation of the von Mises stress contact pressure and displacement.
UNASSIGNED: Compared to conventional CMNs, the PFBN group demonstrated a 9.36%-59.32% reduction in the maximum VMS at the implant. The A3.3 ROI fracture (75% bone density) was the most unstable type of fracture. In comparison to conventional CMNs, PFBN demonstrated more stable data, including VMS values (implant: 506.33 MPa, proximal fracture fragment: 34.41 MPa), contact pressure (13.28 MPa), and displacement (17.59 mm).
UNASSIGNED: Compared to the PFNA, ITN, and GN, the PFBN exhibits improvements in stress concentration, stress conduction, and overall model stability in ROI fractures. The double triangle structure aligns better with the tissue structure and biomechanical properties of the proximal femur. Consequently, the PFBN has significant potential as a new fixation strategy for the clinical treatment of ROI fractures.

BACKGROUND: The aim of this study was to describe the clinical and radiological results of reverse obliquity intertrochanteric fractures treated with dynamic distal locked intramedullary hip nails.
METHODS: Patients with a reverse obliquity intertrochanteric fracture (AO/OTA type 31 A3.1 or A3.3) underwent surgical treatment with a dynamic distal locked intramedullary hip nail between August 2017 and September 2020. Fracture type, reduction quality, change in the position of the distal bone fragment, bone union, complications, and walking ability were evaluated.
RESULTS: Ten patients with reverse obliquity intertrochanteric fractures (seven females and three males) underwent dynamic distal locked intramedullary hip nailing. The mean age was 72.0 ± 18.9 years. Two patients were classi fied as having A3.1 fractures; eight patients were classified as having A3.3 fractures. Anatomical reduction was achieved in six patients, medial displacement remained in three patients, and lateral displacement remained in one patient postoperatively. In 9 out of 10 patients, the center of the proximal end of the distal bone fragment had moved laterally between the time immediately after surgery and the time of the final evaluation. Bone union was obtained uneventfully without any additional treatments in all patients. There were no complications such as infection or implant failure. Walking ability decreased in four patients.
CONCLUSIONS: In all patients, bone union was achieved due to good contact of the medial cortices or the migration of the distal bone fragment into the proximal bone fragment. This procedure can be an option for treating reverse obliquity intertrochanteric fractures.

BACKGROUND: More elderly patients are suffering from intertrochanteric fractures. However, the choice of internal fixation is still controversial, especially in the treatment of unstable intertrochanteric fracture; thus, previous implants continue to be improved, and new ones are being developed. The purpose of our study was to compare the biomechanical advantages between the zimmer natural nail (ZNN) and proximal femoral nail antirotation-II (PFNA-II) in the treatment of elderly reverse obliquity intertrochanteric fractures.
METHODS: A three-dimensional finite element was applied for reverse obliquity intertrochanteric fracture models (AO31-A3.1) fixed with the ZNN or PFNA-II. The distribution, peak value and position of the von Mises stress and the displacement were the criteria for comparison between the two groups.
RESULTS: The stresses of the internal fixation and femur in the ZNN model were smaller than those in the PFNA-II model, and the peak values of the two groups were 364.8 MPa and 171.8 MPa (ZNN) and 832.3 MPa and 1795.0 MPa (PFNA-II). The maximum amount of displacement of the two groups was similar, and their locations were the same, i.e., in the femoral head vertex (3.768 mm in the ZNN model and 3.713 mm in the PFNA-II model).
CONCLUSIONS: The displacement in the two models was similar, but the stresses in the implant and bone were reduced with the ZNN. Therefore, the ZNN implant may provide biomechanical advantages over PFNA-II in reverse obliquity intertrochanteric fractures, as shown through the finite element analysis. These findings from our study may provide a reference for the perioperative selection of internal fixations.