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Background: To improve the performance of cannulated screws (CSs) in the treatment of femoral neck fractures (FNF), a number of new screw configurations have been proposed. However, most of the studies have only analyzed the biomechanical performance of different screw configurations under static conditions. This study aimed to investigate the biomechanical performance of three cannulated screws configurations under different loadings through finite element analysis. Methods: In this FEA study, nine numerical models of proximal femur were employed to analyze the mechanical response of various fracture types and different fixation strategies (three inverted triangular parallel cannulated screws (TCS), four non-parallel cannulated screws (FCS) and biplane double-supported screw fixation (BDSF) respectively). The maximum principal strain (MPS) on the proximal femur and the von Mises stress on the screws were compared for different models. Results: In Pauwels I and II fractures, FCS had the lowest peak MPS on the proximal femur and the BDSF had highest peak MPS value. In Pauwels III fractures, BDSF performance in MPS is improved and better than FCS under partial loading conditions. FCS exhibits the lowest von Mises stress in all load conditions for all fracture types, demonstrating minimal risk of screws breakage. Conclusions: FCS is an ideal screw configuration for the treatment of FNF. And BDSF has shown potential in the treatment of Pauwels type III FNF.

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OBJECTIVE: There is limited research on the effectiveness of orthopedic robot-assisted treatment for sarcopenia combined with femoral neck fractures (FNF) in clinical settings. This study aimed to compare the clinical outcomes of orthopedic robot-assisted screw placement with traditional manual screw placement for treating sarcopenia combined with FNF. METHODS: The retrospective study included patients with FNF under the age of 65 who were admitted to the Department of Orthopedics at XX Hospital Affiliated to XX University between January 2019 and March 2022 and underwent internal fixation with cannulated screws. Grip strength of the dominant hand was measured, and the skeletal muscle index (SMI) was calculated based on the muscle tissue area at the level of the 12th thoracic vertebrae on chest CT divided by height squared. Sarcopenia was diagnosed when SMI was below 42.6 cm2/m2 for men or 30.6 cm2/m2 for women. Patients were then grouped based on whether they underwent orthopedic robot-assisted surgery, as the robot-assisted (RA) group or the freehand (FH) group. Follow-up evaluations over 24-36 months included various parameters such as operation time, blood loss, X-ray shots, number of needle drilling, cannulated nail parallelism, C-reactive protein (CRP) levels, time to weight-bearing, perioperative infection, VAS (visual analogue scale) scores at 1 and 6 months post-surgery, Harris hip score at 6 months post-surgery, and incidence of nonunions and femoral head necrosis within 24 months post-surgery. RESULTS: A total of 127 participants were enrolled in this study, with 46 individuals in the RG group and 81 in the FG group. Across both groups, factors such as gender, age, SMI, injury sides, Garden classifications, intraoperative blood loss, preoperative CRP, and VAS scores at 6 months post-surgery did not show statistically significant differences (p > 0.05). The RA group exhibited shorter operation time, fewer intraoperative X-ray shots, less needle drilling, and lower postoperative CRP levels compared to the FH group. The VAS score of the RA group was lower one month after surgery, whereas the Harris score was higher six months post-surgery (p < 0.05). The parallel angle of the hollow screws in the RA group was superior to that in the FH screw placement group, with an earlier time to bear weight on the ground post-surgery (p < 0.05). There were no statistically significant differences in incision infection, femoral neck nonunion (within 9 months after surgery), and patient satisfaction between the two groups (p > 0.05). Furthermore, the rate of femoral head necrosis after fracture within 2 years in the RA group was lower compared to the FH screw placement group, with statistically significant differences (p < 0.05).

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Purposes: The magnesium alloy bionic cannulated screw (MABCS) was designed in a previous study promoting cortical-cancellous biphasic healing of femoral neck fractures. The main purpose was to analyze the bore diameters that satisfy the torsion standards and further analyze the optimal pore and implantation direction for stabilizing femoral neck fractures. Methods: The MABCS design with bionic holes with a screw diameter of less than 20% met the torsion standard for metal screws. The MABCS was utilized to repair the femoral neck fracture via Abaqus 6.14 software, which simulated the various stages of fracture healing to identify the optimal biomechanical environment for bionic hole size (5%, 10%, 15%, and 20%) and implantation direction (0°, 45°, 90°, and 135°). Results: The stress distribution of the MABCS fracture fixation model is significantly improved with an implantation orientation of 90°. The MABCS with a bionic hole and a screw diameter of 10% provides optimal stress distribution compared with the bionic cannulated screw with diameters of 5%, 15%, and 20%. In addition, the cannulated screw fixation model with a 10% bionic hole size has optimal bone stress distribution and better internal fixation than the MABCS fixation models with 5%, 15%, and 20% screw diameters. Conclusion: In summary, the MABCS with 10% screw diameter bionic holes has favorable biomechanical characteristics for stabilizing femoral neck fractures. This study provides a biomechanical foundation for further optimization of the bionic cannulated screw.

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BACKGROUND: Previous studies have reported that positive buttress is as effective as anatomical reduction in treating young femoral neck fractures, but whether this effect is related to the Pauwels classification remains unclear. The purpose of this study was to retrospectively analyze the clinical prognosis of positive buttress in young femoral neck fractures with different Pauwels classifications, as well as to assess its biomechanical properties. METHODS: A total of 170 young patients with femoral neck fractures who were treated with three cannulated screws were included in this study. Patients were divided into three groups based on their preoperative Pauwels classification. Each group was divided into three subgroups based on the reduction quality: positive buttress, negative buttress and anatomical reduction. The femoral neck shortening, the incidence of necrosis of the femoral head (AVN) and the Harris hip scores at the last follow-up were compared across the three reduction quality within each Pauwels classification. Subsequently, a volunteer was recruited, CT data of the hip was obtained, and finite element models representing different reduction quality under varying Pauwels classifications were established. The biomechanical properties of each model were then evaluated following the application of strains. RESULTS: In Pauwels type I, there were no significant differences in postoperative femoral neck shortening, incidence of AVN, or Harris score among the three types of reduction quality (P > 0.05). However, positive buttress provided superior biomechanical stability compared to negative buttress and anatomical reduction. In Pauwels type II, the incidence of AVN was similar between the positive buttress and the anatomical reduction groups, and both were significantly lower than that in the negative buttress (P < 0.05). The Harris score of the positive buttress was higher than that of the negative buttress, and there was no significant difference in the occurrence of femoral neck shortening between the three groups (P > 0.05). Finite element analysis showed that the biomechanical stability of positive buttress was equivalent to anatomical reduction, and both were better than negative buttress. In Pauwels type III, the incidence of AVN in the anatomical reduction group was lower than that in both the positive buttress and negative buttress (P < 0.05). There was no significant difference in the occurrence of AVN or femoral neck shortening between positive buttress and negative buttress (P > 0.05). There was also no difference in postoperative Harris scores between the three reduction qualities (P > 0.05). Both positive buttress and negative buttress exhibited identical biomechanical qualities and were inferior to anatomical reduction. CONCLUSIONS: The biomechanical and clinical dominance of positive buttress correlates with Pauwels type. Specifically, Positive buttress is biomechanically stable in Pauwels types I and II. In Pauwels type III, positive buttress is not advantageous. As the Pauwels angle increases, the biomechanical benefit of the positive buttress is lost. Therefore, regardless of the Pauwels classification, negative buttress should be avoided after reduction of femoral neck fractures in young patients.

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This systematic review compares Kirschner wires versus a single cannulated screw for the treatment of lateral humeral condyle fractures in children. The purpose of this review is to review the current literature on fixation of lateral condyle fractures of the humerus, and to ascertain whether there is a difference in clinical outcomes of these fractures when fixated with K-wires vs screws. This systematic review of the literature comparing surgical management of paediatric (0-17 years of age) lateral condyle fractures with K-wire versus screw fixation was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic searches of three databases from inception to March 2022 yielded 17 studies which satisfied inclusion criteria, comprising 1,272 patients with a median age of 8.5 years. Eight hundred and fifty-five (67.2%) patients underwent K-wire fixation and 417 (32.8%) underwent screw fixation. Results were divided into comparative and single-arm studies. The median follow-up time was 23.3 months (range 3 months-22 years). A lateral prominence was observed in 114 (13.3%) patients with K-wires and 41 (9.8%) patients with a cannulated screw. An infection developed in 52 (6.1%) patients with K-wires, while only five (1.2%) patients with a screw developed an infection. A carrying angle deformity occurred in 61 (7.1%) patients with K-wires and seven (1.7%) patients with a screw. K-wires and cannulated screws are effective and safe methods of fixation for lateral humeral condyle fractures in children. K-wire fixation may have a greater incidence of infection but allows for safe non-operative removal and versatility with fractures of greater comminution, while screw fixation necessitates a second operation for removal following union.Level of Evidence III Systematic review.

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OBJECTIVE: To biomechanically evaluate the stability of internal fixation methods for femoral neck fractures in small-breed dogs. Furthermore, the possibility of replacing the headed screw with fully threaded headless cannulated screws in the fixation method was assessed. METHODS: The study was conducted from December 12, 2023, to February 7, 2024. A total of 18 femurs from 9 canine cadavers were used in this study. After a simple neck fracture was created, in group A (n = 6), the fracture was stabilized with three 1.1-mm parallel Kirschner wires (K-wires). In group B (n = 6), a 3.0-mm partially threaded cannulated screw and an antirotation pin were used. In group C (n = 6), a 2.5-mm fully threaded headless cannulated screw and an antirotation pin were used. A mechanical test was conducted to apply a single axial compressive load to the femoral head. RESULTS: 9 adult small-breed dogs weighing 3.6 to 8.3 kg (mean ± SD; 5.9 ± 1.6). The mean maximum failure load was highest in group C (495 ± 81 N), followed by group B (454 ± 50.4 N), and then group A (222 ± 21.6 N). Significant differences in maximum failure load were observed between groups A and B as well as groups A and C but not between groups B and C. CONCLUSION: The use of fully threaded headless cannulated screws presents a promising method for internal fixation of canine femoral neck fractures. CLINICAL RELEVANCE: To demonstrate the potential stability and reliability of fully threaded headless cannulated screws.

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Femoral neck fractures present significant challenges in orthopedic surgery, particularly due to technical difficulties and a high complication rate. Surgical intervention is generally recommended, with osteosynthesis and arthroplasty being the main treatment options. Osteosynthesis techniques, including dynamic hip screw (DHS), multiple cannulated screws (MCS), and the femoral neck system (FNS), aim to achieve stable fixation and facilitate fracture healing. Factors influencing the choice of osteosynthesis include fracture displacement, bone quality, patient age, and the presence of posterior tilt. While DHS offers high stability, MCS is preferred in stable type fractures with minimal invasive procedures. FNS, a newer technique, combines the advantages of DHS and MCS, providing strong fixation with minimal soft tissue damage. Considering the comprehensive findings of biomechanical and clinical studies to date, when performing osteosynthesis for unstable femoral neck fractures, caution should be exercised with MCS as it may have slightly inadequate fixation strength compared to DHS and FNS. FNS, being the newest technique, demonstrates superior fixation strength comparable to DHS and is as minimally invasive as MCS. However, it is essential to remember that long-term follow-up results are lacking for FNS.

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BACKGROUND: Chevron osteotomy is a popular technique for repairing complex distal humerus intraarticular fractures. However, re-fixation presents challenges like hardware prominence and soft tissue damage. Headless cannulated screws are gaining popularity for fixation due to better bone purchase and less irritation. This study aims to compare different fixation strategies with headless screws for chevron osteotomy fixation. METHODS: This study utilized 32 polyurethane foam ulna specimens for biomechanical testing. The Chevron osteotomy was performed with an oscillating saw for all specimens. Four different techniques were used for re-fixation: modified tension band wire fixation, plate-screw fixation, cannulated screw fixation, and headless cannulated screw fixation. The constructs were mounted to the testing machine, simulating the elbow in 90 degrees of flexion. All specimens were tested under axial traction. Displacements at 350N and 500N and loads at the failure were recorded. RESULTS: At the load of the implant failure, headless cannulated screw fixation revealed higher force values when compared to the other constructs, and modified tension band wire fixation showed lower force values compared to the other three groups (p < 0.001). The headless cannulated screw fixation group showed no significant differences in osteotomy displacements when tested to a 350N load. There were no significant differences in displacements at a 500N load between the four groups (p = 0.275). CONCLUSION: This study suggests that headless cannulated screw fixation is a viable and effective option for Chevron osteotomies. Headless cannulated screw fixation makes it a promising alternative to traditional fixation methods. This technique may be a more reliable fixation technique during daily activities and moderate elbow motions, indicating that it has the potential to succeed.

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A validated femoral neck fracture model stabilized with three inverted cannulated screws was used to consider different intraoperative scenarios when the inferior screw hole is inadvertently started too inferiorly. These scenarios were to: (1) abandon the misplaced inferior screw hole and restart this hole more proximally, or (2) accept the mispositioned placement of the inferior screw and insert the remaining superior screws parallel or convergent to the inferior screw. Utilizing the second option and accepting the errant hole was associated with the greatest interfragmentary motion and stresses in the bone and hardware. In contrast, the first option created an improved mechanical environment for healing.

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BACKGROUND: As an innovative internal fixation system, FNS (femoral neck system) is increasingly being utilized by surgeons for the treatment of femoral neck fractures. At present, there have been numerous finite element analysis experiments studying the immediate stability of FNS and CSS in treating femoral neck fractures. However, there is scarce mechanical analysis available regarding the effects post internal fixation removal. This study aimed to investigate the alterations in mechanical parameters of the proximal femur before and after the removal of FNS (femoral neck system), and to assess potential distinctions in indicators following the extraction of CSS (Cannulated Screws). METHODS: A proximal femur model was reconstructed using finite element numerical techniques. The models for CSS and FNS were formulated utilizing characteristics and parametric definitions. The internal fixation was combined with a normal proximal femur model to simulate the healing state after fracture surgery. Within the framework of static analysis, consistent stress burdens were applied across the entirety of the models. The total deformation and equivalent stress of the proximal femur were recorded before and after the removal of internal fixation. RESULTS: Under the standing condition, the total deformation of the model before and after removing CSS was 0.99 mm and 1.10 mm, respectively, indicating an increase of 12%. The total deformation of the model before and after removing FNS was 0.65 mm and 0.76 mm, respectively, indicating an increase of 17%. The equivalent stress for CSS and FNS were 55.21 MPa and 250.67 MPa, respectively. The average equivalent stress on the cross-section of the femoral neck before and after removal of CSS was 7.76 MPa and 6.11 MPa, respectively. The average equivalent stress on the cross-section of the femoral neck before and after removal of FNS was 9.89 MPa and 8.79 MPa, respectively. CONCLUSIONS: The retention of internal fixation may contribute to improved stability of the proximal femur. However, there still existed risks of stress concentration in internal fixation and stress shielding in the proximal femur. Compared to CSS, the removal of FNS results in larger bone tunnels and insufficient model stability. Further clinical interventions are recommended to address this issue.

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OBJECTIVE: To analyze and compare the clinical effects of femoral neck dynamic cross screw system (FNS) and cannulated screws(CS) in the treatment of vertically unstable femoral neck fractures. METHODS: The clinical data and short-term follow-up results of 40 patients with vertically unstable femoral neck fractures admitted from July 2020 to August 2021 were retrospectively analyzed. According to different internal fixation methods, 40 patients were divided into two groups, 20 cases in FNS group included 11 males and 9 females with a median of 58.5(50.3, 62.5) years old, and 20 in CS group included 9 males and 11 females with a median of 52.0(40.5, 58.0) years old. The operation time, knife edge length, blood loss and treatment cost of two gruops were observed and compared. The postoperative fracture healing and internal fixation were evaluated with X-ray imaging data, and the femoral neck shortening of the affected side was measured. The incidence of thigh irritation, the time of partial weight bearing and full weight bearing, early necrosis of femoral head, reoperation revision and Harris scores were compared between two groups. RESULTS: FNS group was followed up for 18.0(15.0, 19.0) months, CS group for 17.0(15.0, 18.8) months. There was no significant difference in operation time, incision length and blood loss between two groups(P>0.05). The cost of diagnosis and treatment in FNS group was higher than that in CS group(P<0.001). In FNS group, there was no irritation sign of the affected side thigh, while in CS group, there were 6 cases with discomfort or irritation sign of the lateral thigh(P<0.05). The average time of partial weight bearing activity in CS group was later than that in FNS group(P<0.05); However, there was no significant difference in the activity time of complete weight bearing between two groups(P=0.011>0.05). At the last follow-up, the shortened length of the affected femoral neck in CS group was greater than that in FNS group(P<0.05). There was no early necrosis of femoral head and reoperation in both groups. There was no significant difference in Harris score between two groups 12 months after operation(P>0.05). CONCLUSION: FNS treatment of vertically unstable femoral neck fractures can significantly reduce the incidence of lateral thigh irritation sign, and effectively reduce the postoperative shortening rate of vertically unstable femoral neck fractures, which can provide a relatively stable anti rotation force and anti cutting force, so that patients can go to the ground relatively early, which is conducive to the recovery of the affected hip joint function after surgery. It is a new option for the surgical treatment of vertically unstable femoral neck fractures. However, due to the high cost of treatment, In clinical practice, appropriate surgical treatment is selected according to the actual situation.

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Background: The treatment of unstable femoral neck fractures (FNFs) remains a challenge. In this study, a new cannulated screw for unstable FNFs was designed to provide a new approach for the clinical treatment of these injuries, and its biomechanical stability was analyzed using finite element analysis and mechanical tests. Methods: An unstable FNF model was established. An internal fixation model with parallel inverted triangular cannulated screws (CSs) and a configuration with two superior cannulated screws and one inferior new cannulated screw (NCS) were used. The biomechanical properties of the two fixation methods were compared and analyzed by using finite element analysis and mechanical tests. Results: The NCS model outperformed the CSs model in terms of strain and stress distribution in computer-simulated reconstruction of the inverted triangular cannulated screw fixation model for unstable FNFs. In the biomechanical test, the NCS group showed significantly smaller average femoral deformation (1.08 ± 0.15 mm vs. 1.50 ± 0.37 mm) and fracture line displacement (1.43 ± 0.30 mm vs. 2.01 ± 0.47 mm). In the NCS group, the mean stiffness was significantly higher than that in the CSs group (729.37 ± 82.20 N/mm vs. 544.83 ± 116.07 N/mm), and the mean compression distance was significantly lower than that in the CSs group (2.87 ± 0.30 mm vs. 4.04 ± 1.09 mm). Conclusion: The NCS combined with two ordinary cannulated screws in an inverted triangle structure to fix unstable FNFs can provide better biomechanical stability than CSs and exhibit a length- and angle-stable construct to prevent significant femoral neck shortening.

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Background: Femoral neck fractures need to be treated in their early stages with accurate reduction and stable fixation to reduce complications. The authors compared the early radiologic outcomes of femoral neck fractures treated with the recently introduced Femoral Neck System (FNS, Depuy-Synthes) with conventional cannulated screws (CS) in a multicenter design. Furthermore, the factors associated with early failure after FNS were analyzed. Methods: The FNS group included 40 patients treated between June 2019 and January 2020, and the CS group included 65 patients treated between January 2015 and May 2019. The operation was performed in 3 university hospitals. Patient demographics, fracture classification, postoperative reduction quality, sliding distance of FNS or CS, union and time to union, and complication rates were examined. Logistic regression analysis was performed on candidate factors for early failure of the FNS group. Results: The FNS group had a 90% union rate and a mean time to union of 4.4 months, while the CS group had similar results with an 83.1% union rate and a mean time to union of 5.1 months. In the subgroup analysis of Pauwels type III fractures, the union rates were 75.0% and 58.8% in the FNS and CS groups, respectively, and the time to union was significantly shorter in the FNS group with 4.8 months compared to 6.8 months in the CS group. Early failure rate within 6 months of FNS fixation was observed to be 10%, which included 3 reduction failures and 1 excessive sliding with a broken implant. Risk factors for early failure after FNS were identified as displaced fractures (Garden classification type III or IV), poor reduction quality, longer tip-apex distance, greater sliding distance, and 1-hole implants, of which sliding distance was the only significant risk factor in multivariate analysis. Conclusions: In femoral neck fractures, FNS and CS did not show significant differences for short-term radiologic results. FNS resulted in shorter operative time than cannulated screw fixation and favorable outcomes in Pauwels type III femoral neck fractures. The FNS could be considered a reliable and safe alternative to CS when treating femoral neck fractures.

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OBJECTIVE: The incidence of fragility fractures of the pelvis (FFPs) is increasing in the elderly population, and FFPs that require fixation are a challenge for orthopedic surgeons. The insertion of implants is not risk free due to the complex anatomical and osteoporotic bones and requires a steep learning curve. This study aimed to investigate the clinical efficacy of TiRobot-assisted percutaneous cannulated screw fixation in the treatment of elderly FFP patients. METHOD: The clinical data of 46 elderly FFP patients who had been treated with percutaneous cannulated screw fixation from May 2020 to September 2022 were retrospectively analyzed. Twenty-four patients were treated with percutaneous cannulated screw fixation assisted by the TiRobot (TiRobot-assisted group) and 22 patients were treated with conventional freehand surgery (freehand group). Postoperative outcomes, including Matta value, excellent and good rate (EGR) of fracture reduction, and accuracy of screw placement (ASP), were compared. Changes in the Visual analog scale (VAS) pain score and the Majeed score were recorded and compared between groups before and after surgery and during the 24-week follow-up. Repeated-measures analysis of variance (ANOVA) and effect sizes were used as analysis methods. RESULTS: A total of 90 screws were implanted, 51 screws in the TiRobot-assisted group and 39 screws in the freehand group. The operation time of the two groups was 34.1 ± 2.67 min versus 64.5 ± 4.19 min (p < 0.001). There were no screw-related complications or revision surgeries in any group. The Matta value of the TiRobot-assisted group was 5.13 ± 3.52, which was significantly lower than that of the freehand group (9.00 ± 3.68, p < 0.001), while the EGR was 91.67% versus 72.73%, with statistical significance (p < 0.001). The ASP was 100% in the TiRobot-assisted group, better than that in the freehand group, where it was 85.7% (p = 0.043). At each timepoint in the early postoperative period, the VAS score of the TiRobot-assisted group was significantly lower than that of the freehand group and was close to consistent by the last follow-up; the Majeed score of the former was significantly higher than that of the latter at each timepoint of follow-up, with statistical significance (p < 0.001). CONCLUSION: TiRobot-assisted percutaneous cannulated screw fixation of elderly FFP patients is advantageous over conventional freehand surgery, with less invasion, more accurate screw placement, better fracture reduction, early pain relief, and rapid recovery, suggesting that Freehand method to stabilize FFP in the elderly population.

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OBJECTIVE: A novel technique and outcomes for correction of ununited anconeal process (UAP) via CT-guided cannulated lag screw placement in 7 canine patients is described. ANIMALS: Cases of canine patients (7 patients/8 elbows) diagnosed with UAP that subsequently underwent CT-guided cannulated lag screw placement were retrospectively evaluated. CLINICAL PRESENTATION: Pre- and postoperative exam findings (lameness and pain on range of motion) are presented. Preoperative radiographs and postoperative radiographs at 2 time points (approximately 8 weeks postoperatively and at the time of the most recent imaging; mean, 221 days; range, 85 to 828 days) were scored for degree of arthrosis and postoperative radiographs were evaluated for radiographic union. Complications were reported and stratified by severity and time postoperatively. RESULTS: Minor perioperative (0 to 3 months postoperatively) complications included seroma formation (n = 1) and major perioperative complications involved development of surgical site infections (2), with 2 patients requiring implant removal in the perioperative period (44 and 82 days postoperatively). All patients achieved radiographic union, defined as partial or complete bridging of the anconeal process to the ulna within the study period (mean radiographic follow-up time 221 days postoperatively; range, 85 to 828 days; 5/8 joints partial bridging, 3/8 joints complete bridging) and pre- versus postoperative elbow arthrosis scores remained static in all patients. CLINICAL RELEVANCE: The case outcomes described support the use of CT-guided cannulated lag screw placement as a feasible option for treatment of UAP.

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PURPOSE: We have developed a novel technique for osteotomy/discectomy during en bloc resection of spine tumors named two-step osteotomy/discectomy through cannulated screw (TOCS). This study aims at describing the procedure of TOCS technique and assessing its efficiency and safety. METHODS: We retrospectively reviewed fourteen patients who underwent en bloc resection for spine tumors using TOCS technique in our center between August 2018 and September 2022. The technique was based on a specially designed "slotted" cannulated screw which was a cannulated screw with a longitudinal slot to provide the accessibility of T-saw. During osteotomy/discectomy, the "slotted" cannulated screw was inserted obliquely along the plane between the dura and the posterior wall of spine in light of the planned osteotomy/discectomy plane under routine fluoroscopic imaging guidance. The T-saw was introduced through the screw, and the osteotomy/discectomy was performed sequentially in two steps under the guidance of the screw by turning the slot away and toward the dura. The intra-/perioperative complication, neurological function (determined by Frankel grading), surgical margin (determined by a pathologist using AJCC R system), follow-up details were documented. RESULTS: The mean duration of surgery was 599.3 (360-890) min with a mean volume of intra-operative hemorrhage of 2021.4 (800-5000) mL. The intra-/perioperative complications were found in four patients (28.6%). R0 and R1 resections were achieved in nine and five patients, respectively. There was no R2 resection. After a mean follow-up period of 30.6 (10-67) months, all patients were alive except one patient died ten months after surgery due to unrelated cause. No recurrence and implant failure were found. Thirteen patients (92.9%) exhibited completely normal neurological function same as their preoperative neurological status. CONCLUSION: Using TOCS technique can facilitate a precise, complete and safe osteotomy/discectomy procedure during en bloc resection for spine tumor without the aid of intra-operative navigation.

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Percutaneous antegrade (anterior to posterior) fixation for subtalar joint (STJ) arthrodesis offers various intraoperative and biomechanical advantages. Currently, the entry point for percutaneous antegrade STJ screw fixation is not clearly described and variable. To our knowledge, there are no publications that evaluate anatomic structures at risk or define an anatomically safe entry point for this fixation. The aim of this investigation was to define an anatomically safe and reproducible entry point for percutaneous antegrade STJ arthrodesis fixation, while also describing anatomic structures at risk when undertaking this method of fixation. We hypothesized that percutaneous single screw antegrade STJ fixation would encroach upon named anatomic structures in more than one cadaveric specimen. Ten cadaver limbs were used in this investigation. A percutaneous guidewire was inserted 5 mm lateral to the tibialis anterior tendon. The midpoint of the talar neck served as the sagittal plane starting point, as seen on the lateral fluoroscopic view. A cannulated 6.5-mm headed screw was inserted antegrade through the STJ into the calcaneus. Each specimen was dissected to assess the distance from the screw to nearby anatomic structures and distance from the tibialis anterior tendon to named structures. Our hypothesis was found to be incorrect, as 0/10 screws invaded neurovascular or tendinous structures. The dorsalis pedis artery and deep peroneal nerve were on average 12.1 ± 2.79 mm and 12.2 ± 2.82 mm lateral to the screw, respectively. These findings are clinically relevant and ultimately allow us to define an anatomic safe starting point for percutaneous antegrade STJ single screw fixation.

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BACKGROUND:After the internal fixation of cannulated screws in femoral neck fractures,because the affected limb is often unable to bear weight in the short term and the implants with high stiffness have a stress shielding effect on the fracture end,it is easy to cause osteoporosis of the affected limb and changes in the biomechanical distribution of the proximal femur,the incidence of osteonecrosis of the femoral head is high after surgery.At present,few studies have been conducted on the biomechanical effects of osteoporosis at the proximal end of the femur occurring after femoral neck fracture surgery on femoral neck fracture treated with cannulated screws. OBJECTIVE:Using finite element analysis,to investigate the biomechanical effects of osteoporosis occurring after femoral neck fracture surgery on femoral neck fracture treated with cannulated screws and explore the role of biomechanical factors in osteonecrosis of the femoral head. METHODS:Based on the obtained CT scan data of the femur in a patient with a femoral neck fracture,a proximal femoral model for internal fixation for femoral neck fracture was established by Mimics 19.0,3-Matic,UG 11.0,Hypermesh 14.0,and Abaqus software.One finite element model of the proximal femur without osteoporosis and three finite element models of the proximal femur with osteoporosis were analyzed using Abaqus software.The stress,contact pressure,displacement peak and cloud map under different components of the four models were measured and analyzed,and the internal stress changes and distribution of the femoral head were compared and analyzed. RESULTS AND CONCLUSION:The stresses and contact pressures of the femoral head and lower anterior cannulated screws varied more with the degree of osteoporosis.The peak displacement of the four models increased slowly with the degree of osteoporosis.By one-way analysis of variance,there was no significant effect of the degree of osteoporosis on the peak stress,contact pressure,and displacement of the different components.The internal stress distribution of the femoral head changed with the degree of osteoporosis.Changes in the biomechanical environment of the proximal femur have an important impact on osteonecrosis of the femoral head.

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BACKGROUND:The more vertical the femoral neck fracture line,the more shear force the femoral neck fracture may bear,so it may be prone to internal fixation failure,nonunion,or necrosis of the femoral head.At present,there is controversy as to which hollow nail fixation mode is ideal. OBJECTIVE:To evaluate different configurations and numbers of cannulated screw configurations to learn more about the biomechanical differences in vertical fractures of the femoral neck using finite element analysis. METHODS:Femoral CT data were collected from a 24-year-old healthy male volunteer and imported into Mimics software to build a three-dimensional geometric model of the femur.Model refinement and surface fitting processing were carried out in Geomagic software and imported into SolidWorks software to establish a vertical fracture model of the femoral neck.Six cannulated screw models were established,including three triangle configuration,three inverted triangle configuration,three double-plane double-support configuration(F scheme),three transverse configuration,four diamond configuration and four Alpha configuration.The peak stress,strain and displacement of internal fixation and femoral fracture models under different loads(350,700,1 400,and 2 100 N)were compared among different configurations. RESULTS AND CONCLUSION:(1)Under four kinds of loads,screw stress conditions were as follows:biplanar double-supported configuration(F scheme)>transverse configuration>inverted triangle configuration>positive triangular configuration>Alpha configuration>rhombus configuration.The peak value of Von mises stress was concentrated in the screw close to the fracture line.(2)Under four kinds of loads,the screw displacement was Alpha configuration>inverted triangle configuration>positive triangular configuration>biplanar double-supported configuration(F scheme)>rhombus configuration>transverse configuration,and the peak displacement was mainly concentrated on the hollow screw head.(3)Under four kinds of loads,the stress conditions of the proximal femoral bone block were biplanar double-supported configuration(F scheme)>transverse configuration>inverted triangle configuration>Alpha configuration>positive triangular configuration>rhombus configuration,and the stress peak mainly concentrated in the lower neck of femur.(4)Under 350 N load,the displacement of the proximal femur bone block was transverse configuration>biplanar double-supported configuration(F scheme)>positive triangular configuration>Alpha configuration>inverted triangle configuration>rhombus configuration.In the other three loads,the peak displacement of the inverted triangle configuration was smaller than that of the rhombus configuration.The peak displacement was mainly concentrated in the head.(5)The rhombus configuration was the most dispersed in the stress distribution of the proximal femoral bone.The rhombus configuration was the smallest in the peak displacement of the femur.The stress,displacement and peak displacement of the fracture end of each internal fixed model increased gradually with the increase of load.(6)The biomechanical performance of the four diamond-shaped models in the internal fixation of vertical femoral neck fractures is better than that of other groups of models.The four rhomboid models have stable fixation,small displacement value of fracture end and dispersed stress,which can help resist shear force and prevent varus collapse and create a good mechanical environment for fracture healing.

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BACKGROUND:Pauwels Ⅲ femoral neck fracture is a typical unstable fracture characterized by high vertical shear force and high incidence of postoperative complications.At present,there are many fixation methods for Pauwels Ⅲ fracture,and there is no clear conclusion as to which internal fixation is the best fixation method for Pauwels Ⅲ femoral neck fracture in young adults. OBJECTIVE:To compare the clinical effect of three inverted triangle cannulated screws assisted transverse lag screws and femoral neck system in fixing Pauwels Ⅲ femoral neck fractures of young adults. METHODS:From May 2021 to December 2022,21 young and middle-aged patients with Pauwels Ⅲ femoral neck fracture were treated with three inverted triangle cannulated screws assisted by transverse lag screws and femoral neck system in Affiliated Hospital of Southwest Medical University.Of them,9 patients were treated with three inverted triangle cannulated screws and one transverse lag screws perpendicular to the fracture line as the 3+1 cannulated screw group and 12 patients were treated with femoral neck system as the femoral neck system group.The two fixation methods were compared in terms of operation time,intraoperative blood loss,total incision length,intraoperative fluoroscopy times,fracture healing time,and limb function. RESULTS AND CONCLUSION:(1)All patients were followed up.Patients in the 3+1 cannulated screw group were followed up for 10-25 months,with a mean of(17.44±4.30)months.The patients in the femoral neck system group were followed up for 8-24 months,with a mean of(15.58±4.68)months.(2)The intraoperative fluoroscopy times and Harris score at 3 months postoperatively in the femoral neck system group were better than those in the 3+1 cannulated screw group,and the difference was statistically significant(P<0.05).The intraoperative blood loss,total incision length,and femoral neck shortening distance in the 3+1 cannulated screw group were better than those in the femoral neck system group,and the differences were statistically significant(P<0.05).There was no significant difference in operation time,fracture healing time,and Harris score at the last follow-up between the two groups(P>0.05).(3)It is indicated that three inverted triangle cannulated screws assisted transverse lag screw and femoral neck system can achieve good clinical effects in the treatment of young and middle-aged Pauwels Ⅲ femoral neck fracture.The femoral neck system has fewer intraoperative fluoroscopy times and better early overall stability,while the 3+1 cannulated screw is more minimally invasive,easier to operate.Both fixation methods are worthy of clinical application and promotion,and can be selected according to the actual clinical situation.