Mechanical analysis of the femoral neck dynamic intersection system with different nail angles and clinical applications.

BACKGROUND: The femoral neck dynamic intersection system (FNS) is mechanically more stable than other internal fixation techniques. Current studies have confirmed that the structural design of FNS has good biomechanical properties in European and American populations. However, whether the suitability of the FNS's 130° main nail angle design for Asian populations has been thoroughly investigated remains unclear. AIM: To compare the biomechanical stability differences among different main nail angles of the FNS in the treatment of femoral neck fractures in Asian populations. METHODS: Computed tomography data of the femur of healthy adult male volunteers were imported into Mimics software to create a three-dimensional model of the femur. The model was adapted to the curve using Geomagic software and imported into Solidworks software to construct the Pauwels I femoral neck fracture model and design the FNS internal fixation model using different main nail angles. Afterward, the models were assembled with the FNS fracture model and meshed using the preprocessing Hypermesh software. Subsequently, they were imported into Abaqus software to analyze and evaluate the biomechanical effects of different angles of the FNS main nail on the treatment of femoral neck fractures. RESULTS: The peak displacement of the proximal femur under different angles of FNS fixation under stress was 7.446 millimeters in the 120° group and 7.416 millimeters in the 125° group; in the 130°, 135°, and 140° FNS fixation groups, the peak displacement was 7.324 millimeters, 8.138 millimeters, and 8.246 millimeters, respectively. In the 120° and 125° FNS fixation groups, the maximum stresses were concentrated at the main nail and the anti-rotation screw, which intersected the fracture line of the femur neck, resulting in peak stresses of 200.7 MPa and 138.8 MPa, respectively. Peak stresses of 208.8 MPa, 219.8 MPa, and 239.3 MPa were observed on the angular locking plate distal to the locking screw in the 130°, 135°, and 140° fixation groups. CONCLUSION: FNS has significant stress distribution properties, a minimal proximal femoral displacement, and an optimal stability for treating femoral neck fractures in Asian populations when performed with a 130° main nail angle.

Spatiotemporal and kinematic gait analysis in patients with knee osteoarthritis and femoral varus deformity.

BACKGROUND: Knee osteoarthritis (OA) is commonly combined with the presentation of a coronal deformity of the knee. The bony origin of the knee varus deformity can be classified as tibial origin, femoral origin, or a combination of tibial and femoral causes. Deformities of tibial origin are mostly common clinically, while patients with knee OA with femoral varus deformity are less common. RESEARCH QUESTION: Do hip, knee and ankle kinematics and spatiotemporal parameters differ between patients with knee OA with femoral varus deformity and healthy subjects? METHODS: Twenty-five patients (14 females and 11 males) with knee OA and femoral varus deformity and 20 healthy subjects (12 males and 8 females) as control group were included in this study. The kinematic parameters of the hip-knee-ankle joint and spatiotemporal gait parameters were included in the study. RESULTS: This study found that the step speed and step length of the knee OA with femoral varus (KOAF) group were smaller than those of the control group, while double support period percentage was greater in the KOAF group. Significant differences were found in the maximum knee extension angle, maximum knee flexion angle, knee flexion range of motion, maximum hip flexion angle, maximum hip extension angle, and hip flexion range of motion between the two groups. After comparing the ankle motion between the two groups, significant differences were found in the maximum eversion angle, inversion range of motion, maximum ankle abduction angle, and abduction range of motion. SIGNIFICANCE: Knee OA with femoral varus deformity causes adaptive changes in the kinematic parameters of hip, knee and ankle joints and spatiotemporal gait parameters to alleviate symptoms and maintain normal activity.

Intra-articular opening wedge osteotomy for varus ankle arthritis with computer-assisted planning and patient-specific surgical guides: a retrospective case series.

BACKGROUND: Computer-assisted preoperative planning, combined with PSI has become an effective technique for treating complex limb deformities. The purpose of this study was to evaluate the efficacy and safety of the novel technique in corrective osteotomy for intra-articular varus ankle deformities associated with osteoarthritis and ankle instability. METHODS: Nineteen patients with intra-articular varus ankle arthritis were reviewed between April 2017 and June 2019, including ten men and nine women with a mean age of 58.3 ± 9.9 years (range, 38 to 76 years). All patients underwent intra-articular opening wedge osteotomy assisted by 3D virtual planning and PSI. Weight-bearing radiographs were used to assess the radiographic results, including TAS angle, TT angle, TMM angle, TC angle, TLS angle, opening-wedge angle, and wedge height. Functional outcomes were assessed by the AOFAS score, VAS score, and ROM of the ankle. RESULTS: The average follow-up time was 32.2 ± 9.0 months (range, 22 to 47 months). The average union time was 4.4 ± 0.9 months (range, 3.0 to 6.5 months). The TAS angle significantly changed from 84.1 ± 4.6° preoperatively to 87.7 ± 3.1° at the 1-year follow-up and 86.2 ± 2.6° at the latest follow-up. Similarly, the TT angle, TMM angle and TC angle changed significantly at the 1-year follow-up compared with the preoperative assessment and remained stable until the last follow-up. However, the TLS was not corrected significantly. The postoperative obtained opening-wedge angle, and wedge height showed no significant change with preoperative planning. The overall complication rate was 15.8%. The mean VAS score improved from 5.3 ± 0.6 to 2.7 ± 0.7. The mean AOFAS score improved from 56.2 ± 7.6 to 80.6 ± 4.6. However, the ROM showed no significant change. CONCLUSIONS: Accurate correction and satisfactory functional recovery were attained with computer-assisted planning and PSI in the corrective osteotomy of intra-articular varus ankle deformities.

Reinforcement strategy for medial open-wedge high tibial osteotomy: a finite element evaluation of the additional opposite screw technique and bone grafts.

BACKGROUND AND OBJECTIVE: bone grafts (bgs) and the opposite screw insertion technique are reported to enhance initial stability after medial open-wedge high tibial osteotomy (OWHTO); however, it is unclear how the general and local biomechanical stability of the proximal tibia is affected by these reinforcement strategies. In this study, we aimed to assess the biomechanical differences among different fixation configurations for OWHTO under two loading conditions using finite element analysis, and to assess the biomechanical contribution of an opposite screw insertion. METHODS: Models of the proximal tibia with three different gap defects were created to simulate different distraction heights in OWHTO. Four groups of models were then assembled with different fixation configurations, including the no BG (NBG) group, BG group, partially threaded screw (PT) group, and fully threaded screw (FT) group. Testing loads were applied to simulate the static forces on the knee joint during double-limb and single-limb standing. For each group, the stresses of the lateral hinge area (LHA) and the medial implant area (MIA), the maximum displacement of the tibia and the relative displacement (RD) of the medial gap were evaluated. RESULTS: Compared to NBG group, bone block grafting effectively reduced the stress of the tibia and implant, as well as the maximum displacement of the tibia and the RD of the medial gap. The opposite screw group showed similar trends in alleviating the stress concentration on the LHA and MIA, and contributing to the maintaining the medial gap reduction, especially in the FT group; however, additional stresses were concentrated on the opposite screw itself, which indicated the potential risk of screw breakage. CONCLUSIONS: Compared to NBG group, the BG group bone graft showed superior biomechanical advantages in decreasing the risk of implant failure and lateral hinge fracture, and maintaining the reduction in OWHTO. The additional opposite screw provided an extra support to the proximal tibia, with similar contributions to improve the structural stability after osteotomy, especially in the FT group.

Correction to: Finite element analysis of two cephalomedullary nails in treatment of elderly reverse obliquity intertrochanteric fractures: zimmer natural nail and proximal femoral nail antirotation-ΙΙ.

In the original publication of this article [1], Chinese text of the Figs. 3, 4, 5 has not been converted to English.

Comparative finite element analysis of three implants fixing stable and unstable subtrochanteric femoral fractures: Proximal Femoral Nail Antirotation (PFNA), Proximal Femoral Locking Plate (PFLP), and Reverse Less Invasive Stabilization System (LISS).

BACKGROUND: The optimal type of fixation implant for managing subtrochanteric fractures (STFs) is debated, as uncertainty continues to surround the comparative biomechanical performance of the proximal femoral nail antirotation (PFNA), proximal femoral locking plate (PFLP), and reverse less invasive stabilisation system (LISS). No studies have used finite element analysis (FEA) to compare these three devices. The objective of this study was to use FEA to compare the PFNA, PFLP, and LISS used to treat STFs based on the following criteria: (1) stress distribution on the femur and implant, (2) peak stress and stress on the medial side of the femur near the fracture site, and (3) smallest axial displacement of the femoral head. HYPOTHESIS: Of the three implants, the PFNA has the best biomechanical performance when used for STF fixation. METHODS: FEA was used to assess synthetic bone responses to the three implants used to fix three STF types, namely, Seinsheimer I, III, and IV, characterised by increasing bone loss and/or comminution with subsequent instability. Loading was with 1400N axial compression force. RESULTS: The LISS and PFLP exhibited similar biomechanical properties in all three fracture types. However, with the Seinsheimer IV fracture, the triangular configuration of the PFLP resulted in stress concentration at the medial and lateral sides of the implant junction. With the Seinsheimer I and III fractures, the PFNA resulted in higher peak stress (183.85MPa and 364.58MPa, respectively) compared to the PFLP (102.90MPa and 177.52MPa) and LISS (116.55MPa and 227.97MPa). With the Seinsheimer IV fracture, peak stress was highest with LISS (2310.40MPa) and was higher with PFLP (2054.90MPa) than with PFNA (1313.30MPa). With the Seinsheimer I and III fractures, the axial femoral head displacement was greater with the PFNA (0.74mm and 1.13mm, respectively) than with the PFLP (0.48mm and 1.02mm) and LISS (0.52mm and 0.92mm). With the Seinsheimer IV fracture, in contrast, the PFNA produced less axial femoral head displacement (4.1mm) compared to the PFLP (12.03mm) and LISS (16.56mm). DISCUSSION: With unstable (Seinsheimer IV) STFs, fixation stability was better with the PFNA compared to the PFLP and LISS. In contrast, with stable STFs (Seinsheimer I and III), the PFLP and LISS offered greater stability, with similar biomechanical effects. However, with Seinsheimer III fractures, the stress on the implant-femur interface was greater with the LISS. LEVEL OF EVIDENCE: IV, basic science study.

Finite element analysis of two cephalomedullary nails in treatment of elderly reverse obliquity intertrochanteric fractures: zimmer natural nail and proximal femoral nail antirotation-ΙΙ.

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.

Comparison of Less Invasive Stabilization System Plate and Retrograde Intramedullary Nail in the Fixation of Femoral Supracondylar Fractures in the Elderly: A Biomechanical Study.

OBJECTIVE: To compare the biomechanical stabilities of less invasive stabilization system (LISS) plate and retrograde intramedullary nail (IMN) for the comminuted femoral supracondylar fracture fractures in the elderly. METHODS: Sixteen pairs of embalmed cadaver femurs were obtained to simulate a comminuted supracondylar femur fracture (AO/OTA33-A3) gap model. All left-side specimens were fixed with LISS plate, and retrograde IMN were applied to the right-side specimens. All specimens were tested in torsional, axial and cyclic load mode on an Instron testing machine. RESULTS: The mean torsional stiffness for LISS plate group was 34.1% greater than retrograde IMN group (2.90 vs. 1.91 Nm/degree, P = 0.002), but the mean axial stiffness was greater for the retrograde IMN (199.16 vs. 303.93 N/mm, P < 0.001). The total deformation of LISS plate caused by cyclic axial loading was greater than retrograde IMN (4.17 vs. 3.57 mm, P = 0.014). Significantly less mean irreversible deformation was detected in LISS plate than in retrograde IMN (1.64 vs. 1.69 mm, P = 0.699). Failure loads of the constructs were significantly different between the two groups (LISS plate: 2941±128 N; retrograde IMN: 4022±176 N, P < 0.001). CONCLUSION: For comminuted femoral supracondylar fractures in the elderly, the tested instruments can both maintain sufficient biomechanical stabilities, but retrograde IMN is superior to LISS plate in deformation of fracture site.

Custom-made Prosthesis for Reconstruction after Radical Resection for Chondrosarcoma of Manubrium.

The clinical incidence of tumors in the manubrium is not high. Regardless of whether the tumor is primary or metastatic, the tumor should be completely removed as long as the patient is able to tolerate the surgery. This procedure can lead to sternal defects. Deciding on the method of defect reconstruction is a critical problem that clinicians face. In this , to reduce the limitations of the patient's upper body movement after surgery due to the inflexibility in the connections of the sternal prosthesis, we created a prosthesis using a computer-assisted design method and a 3-D technique, to completely preserve the agility of the sternum and maximize the patient's post-operational movement. The method used in the present study takes into consideration the individual's chest anatomy, sternum stress, and many other biological characteristics. Care is taken to measure the sternum size accurately, to provide personalized treatment, to accomplish precise results, and to reduce potential future damage. The patient's shoulder function was improved following the procedure.

Bone Microarchitecture and Biomechanics of the Necrotic Femoral Head.

The mechanism behind osteonecrosis of the femoral head (ONFH) remains unclear. The aim of this study was to explore the pathogenesis of ONFH from a biomechanical standpoint to provide a theoretical basis for improved treatments. We compared the bone structure of fractured femoral heads with that of necrotic femoral heads by Micro-CT scanning and histological evaluation. In addition, we compared the biomechanical properties of each zone in fractured femoral heads with those in necrotic femoral heads by using biomechanical tests. Compared with fractured femoral heads, bone microarchitecture and bone morphometry in necrotic zone and sclerotic zone of necrotic femoral heads have altered markedly. In addition, the biomechanical properties of the necrotic zone in femoral heads weaken markedly, while those of the sclerotic zone strengthen. We hypothesize that discordance between bone structure and function of the femoral head may be involved in the pathogenesis of ONFH and that more attention should be paid to the prevention and treatment of such discordance.

TET3 Mediates Alterations in the Epigenetic Marker 5hmC and Akt pathway in Steroid-Associated Osteonecrosis.

Steroid-associated osteonecrosis (SAON) is one of the common complications of clinical glucocorticoid (GC) administration, with osteocyte apoptosis appearing as the primary histopathological lesion. However, the precise mechanism underlying SAON remains unknown. Epigenetic modification may be a major cause of SAON. Recently, cumulative research revealed that Ten-Eleven Translocation (TET) proteins can catalyze the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and then alter the epigenetic state of DNA. Here, we report that TET3-5hmC was upregulated in the femoral head tissues of SAON patients and MLO-Y4 cells with dexamethasone (Dex) treatment. Knockdown of TET3 in MLO-Y4 cells decreased 5hmC enrichment and rescued Dex-induced apoptosis. Meanwhile, the local intramedullary injection of TET3 siRNA in Sprague-Dawley rats abrogated GC-induced osteocyte apoptosis, histopathological changes, abnormal MRI signals, and bone microstructure declines in the femoral head in vivo. Moreover, a hydroxymethylated DNA immunoprecipitation (hMeDIP)-chip analysis of Dex-treated osteocytes revealed 456 different 5hmC-enriched genes. The Akt pathway was found to mediate the functional effect of Dex-induced dynamic 5hmC change; this was further verified in clinical samples. The loss of TET3 in MLO-Y4 cells abrogated Dex-induced Akt signaling pathway inhibition. Therefore, our data for the first time identify the effect of TET3-5hmC on the Akt pathway and the necessity of this signaling cascade in SAON, identifying a new potential therapeutic target. © 2016 American Society for Bone and Mineral Research.