Vertical Femoral Neck Fractures Research Articles

A finite element analysis of a low-profile femoral neck system of screws in sleeves in a vertical femoral neck fracture model

BackgroundFemoral neck system (FNS) has exhibited some drawbacks, such as non-fit of the plate with the lateral femoral cortex, postoperative pain, and the potential risk of subtrochanteric fractures. We have developed a low-profile FNS system that addresses some compatibility issues in FNS. In this study, we conducted finite element analysis on the 1-hole FNS (1 H-FNS), 2-holes FNS (2 H-FNS), and low-profile FNS (LP-FNS) and compared their biomechanical performance.MethodsAfter the mesh convergence analysis, we established three groups of 1 H-FNS, 2 H-FNS, and LP-FNS. The interfragmentary gap, sliding distance, shear stress, and compressive stress and the bone-implant interface compression stress, stiffness, and displacement were determined under the neutral, flexion, or extension conditions of the hip joint, respectively. The stress and displacement of the femur after the implant removal were also investigated.Results(1) There were no obvious differences among the three FNS groups in terms of the IFM distance. However, the LP-FNS group showed less rotational angle compared with conventional FNS (neutral: 1 H-FNS, -61.64%; 2 H-FNS, -45.40%). Also, the maximum bone-implant interface compression stress was obviously decreased under the neutral, flexion, or extension conditions of the hip joint (1 H-FNS: -6.47%, -20.59%, or -4.49%; 2 H-FNS: -3.11%, 16.70%, or -7.03%; respectively). (2) After the implant removal, there was no notable difference in the maximum displacement between the three groups, but the maximum von Mises stress displayed a notable difference between LP-FNS and 1 H-FNS groups (-15.27%) except for the difference between LP-FNS and 2 H-FNS groups (-4.57%).ConclusionsThe LP-FNS may not only provide the same biomechanical stabilities as the 1 H-FNS and 2 H-FNS, but also have more advantages in rotational resistance especially under the neutral condition of the hip joint, in the bone-implant interface compression stress, and after the implant removal. In addition, the 1 H-FNS and 2 H-FNS have similar biomechanical stabilities except for the maximum von Mises stress after the implant removal. The femur after the LP-FNS removal not only is subjected to relatively little stress but also minimizes stress concentration areas.

Single-plane osteotomy model is inaccurate for evaluating the optimal strategy in treating vertical femoral neck fractures: A finite element analysis

Background and objectivesThe conventional method for simulating vertical femoral neck fractures (vFNFs) is via a vertical single-plane osteotomy (SPO) across the entire femur. However, the accuracy of SPO for evaluating the optimal internal fixation strategy (IFS) and the appropriate assessment parameters is not clear. This study thus aimed to examine the accuracy of SPO in evaluating IFSs and to identify appropriate evaluation parameters using finite element analysis. MethodsEighty patient-specific finite element models were developed based on CT images from eight vFNF patients. The natural fracture model was built using structural features of the affected side, while the SPO was simulated on the healthy side. Five different IFSs were applied to both the natural fracture and SPO groups. Thirteen parameters, including stress, displacement, and stiffness, were subjected to a two-way repeated measures ANOVA to determine the effect of IFSs and fracture morphology on stability. A Pearson correlation analysis was performed on varied parameters with various IFSs to identify independent parameters. Based on these independent parameters, the entropy evaluation method (EEM) score was used to rank the performance of IFSs for each patient. ResultsEight of the thirteen parameters were significantly influenced by IFSs (p < 0.05), two by fracture morphology (p < 0.01), and none by the interaction between IFS and fracture morphology. In the natural fracture group, parameters including screw stress and displacement, bone cut rate (BCR), and compression effects varied independently with distinct IFSs. In the SPO group, trunk displacement, BCR, cut-out risk, and compression effects parameters changed independently. The BCR of the Alpha strategy was significantly higher than that of the Inverted strategy in the natural fracture group (p = 0.002), whereas the opposite was observed in the SPO group (p = 0.016). Regarding compression effects, two IFS pairings in the natural fracture group and seven IFS pairings in the SPO group exhibited significant differences. None of the five IFSs achieved the optimal EEM score for each patient. ConclusionsThe single-plane osteotomy model may have limitations in assessing IFSs, particularly when the bone cut rate and compression effects are the main influencing factors. Parameters of the screw stress and displacement, BCR, and compression effects appear to be relevant in evaluating IFSs for natural fracture models. It indicates that individualized natural fracture models could provide more comprehensive insights for determining the optimal IFS in treating vFNFs.

Compressive buttress compared with off-axial screw fixation for vertical femoral neck fractures in young adults: a prospective, randomized controlled trial

BackgroundTo compare the clinical outcomes of compressive buttress screw (CBS) fixation, a novel screw fixation strategy, to off-axial screw fixation (off-axial partial threaded cannulated screw, OPTCS) for vertical femoral neck fractures (FNFs) in young adults.MethodsA total of 146 adults younger than 55 years old with high-energy Pauwels type III FNFs were randomized to receive CBS fixation or OPTCS fixation. Primary outcomes were complication rates, including fixation failure, fracture nonunion, and avascular necrosis of the femoral head (ANFH) at 24 months after treatment. Fixation loosening, femoral neck shortening and varus collapse, patient function and quality of life using the Harris hip score (HHS), and EuroQol-5 dimensional-5 levels (EQ-5D-5L) questionnaire (including EQ-5D-5L and EQ-VAS) were assessed as secondary outcomes at 24 months.ResultsCBS and OPTCS fixation groups were similar with regard to demographics at baseline. At 24 months, patients in the CBS fixation cohort had a significantly lower rate of fixation failure (10.5% vs. 25.0%, p = 0.041) and fracture nonunion (1.8% vs. 18.3%, p = 0.003) compared with patients who received OPTCS fixation. There was no difference in rate of ANFH (7.0% vs. 11.7%, p = 0.389) between groups. Additionally, patients managed with CBS fixation showed significantly less fixation loosening (19.3% vs. 58.3%, p < 0.001), less severe femoral neck shortening and varus collapse (10.5% vs. 25.0%, p = 0.007), higher HHS (93 vs. 83, p = 0.001) and more excellent grade (68.4% vs. 36.7%, p = 0.008), higher EQ-5D-5L (0.814 vs, 0.581, p < 0.001) and EQ-VAS (85 vs. 80, p = 0.002).ConclusionCBS screw fixation confers significantly lower complication rate in addition to higher functional and quality of life outcomes for young adults with high-energy FNF compared with OPTCS fixation.Trial registrationThis prospective, randomized controlled trial was approved by the institutional review board of our center, Ethics Committee of Shanghai sixth people's Hospital, and registered at www.chictr.org.cn (Approval Number: ChiCTR1900026283; Registered 29 September 2019—Retrospectively registered, https://www.chictr.org.cn/showproj.html?proj=43164).

The novel magnesium–titanium hybrid cannulated screws for the treatment of vertical femoral neck fractures: Biomechanical evaluation

BackgroundConventional cannulated screws are commonly used for internal fixation in the treatment of vertical femoral neck fractures. However, the noticeably high rates of undesirable outcomes such as nonunion, malunion, avascular necrosis, and fixation failure still troubled the patients and surgeons. It is urgent to develop new cannulated screws to improve the above clinical problems. The purpose of this study was to design a novel magnesium-titanium hybrid cannulated screw and to further evaluate its biomechanical performance for the treatment of vertical femoral neck fractures. MethodsA novel magnesium-titanium hybrid cannulated screw was designed, and the conventional titanium cannulated screw was also modeled. The finite element models for vertical femoral neck fractures with magnesium-titanium hybrid cannulated screws and conventional cannulated screws were respectively established. The hip joint contact force during walking gait calculated by a subject-specific musculoskeletal multibody dynamics model, was used as loads and boundary conditions for both finite element models. The stress and displacement distributions of the cannulated screws and the femur, the micromotion of the fracture surfaces of the femoral neck, and the overall stiffness were calculated and analyzed using finite element models. The biomechanical performance of the Magnesium–Titanium hybrid cannulated screws was evaluated. ResultsThe maximum stresses of the magnesium-titanium hybrid cannulated screws and the conventional cannulated screws were 451.5 ​MPa and 476.8 ​MPa, respectively. The maximum stresses of the femur with the above different cannulated screws were 140.3 ​MPa and 164.8 ​MPa, respectively. The maximum displacement of the femur with the hybrid cannulated screws was 6.260 ​mm, lower than the femur with the conventional cannulated screws, which was 7.125 ​mm. The tangential micromotions in the two orthogonal directions at the fracture surface of the femoral neck with the magnesium-titanium hybrid cannulated screws were comparable to those with the conventional cannulated screws. The overall stiffness of the magnesium-titanium hybrid cannulated screw system was 490.17 ​N/mm, higher than that of the conventional cannulated screw system, which was 433.92 ​N/mm. ConclusionThe magnesium-titanium hybrid cannulated screw had superior mechanical strength and fixation stability for the treatment of the vertical femoral neck fractures, compared with those of the conventional cannulated screw, indicating that the magnesium-titanium hybrid cannulated screw has great potential as a new fixation strategy in future clinical applications.The translational potential of this article: This study highlights an innovative design of the magnesium-titanium hybrid cannulated screw for the treatment of vertical femoral neck fractures. The novel magnesium-titanium hybrid cannulated screw not only to provide sufficient mechanical strength and fixation stability but also to contribute to the promotion of fracture healing, which could provide a better treatment for the vertical femoral neck fractures, beneficially reducing the incidence of nonunion and reoperation rates.

Medial Locking Plate Can Increase the Fixation Stability of Vertical Femoral Neck Fracture in Young Adults?

Introduction: Vertical femoral neck fractures in young adults are usually caused by high-energy trauma. These injuries are difficult to stabilize due to significant shear forces acting on the fracture site. Their treatment is challenging and with high risks of complications, such as fixation failure, malunion, nonunion, and avascular necrosis of the femoral head. Material and Methods: It compared the biomechanical stability provided by 3 different fixation methods: (1) dynamic hip screw with derotation screw, (2) cannulated screws with a conventional medial bone plate, and (3) cannulated screws with a locked medial bone plate. These fixation structures were applied on fourth-generation medium-sized synthetic bones, with a 17 pound per cubic foot cellular foam core and cervico-diaphyseal angle of 120 degrees were used. The comparison was performed through biomechanical tests under cyclic loading followed by an ultimate load. The interfragmentary movement at the fracture site was the main variable for the cyclical phase. Results: The biomechanical comparison showed no statistical differences (P &gt; 0.05) in stiffness, micromovement level, and mechanical resistance among the fixation techniques evaluated. Discussion: To stabilize the vertical femoral neck fracture in young patients, the use of a medial bone plate associated with cannulated screws on a “tie-rod” assembly is an option that supports the mechanical demand until the fracture healing. The locked medial plate did not provide an advantage compared with the conventional bone plate.

A biomechanical comparison of three fixation methods for unstable femoral neck fractures with medial calcar defect

BackgroundUnstable femoral neck fractures with medial calcar defects are difficult to manage. The optimal fixation methods for these fractures have been a subject of ongoing debate among orthopedic surgeons. In this study, three different fixation techniques for vertical, medial defected femoral neck fractures were compared.MethodsIn this study, a biomechanical analysis was conducted to compare three fixation methods: cannulated screws (Group 1), cannulated screws combined with a medial buttress plate (Group 2), and intramedullary nails (Group 3). Synthetic composite bone models representing vertical collum femoris fractures with medial calcar defects were used. Each group consisted of seven specimens, and, to maintain consistency, a single surgeon performed the surgical procedure. Biomechanical testing involved subjecting the specimens to axial loading until failure, and the load to failure, stiffness, and displacement values were recorded. Normality was tested using the Shapiro–Wilk test. One-way ANOVA and Tukey’s HSD post hoc test were used for comparisons.ResultsThe difference in the load to failure values was statistically significant among the groups, with Group 2 exhibiting the highest load to failure value, followed by Group 3 and Group 1. Stiffness values were significantly higher in Group 2 than in the other groups. Displacement values were not significantly different between the groups. Fracture and displacement patterns at the point of failure varied across the groups.ConclusionThe results of this study indicate that fixation with a medial buttress plate in combination with cannulated screws provides additional biomechanical stability for vertical femoral neck fractures with medial calcar defects. Intramedullary nail fixation also demonstrated durable stability in these fractures. These findings can be used to better understand current management strategies for these challenging fractures to promote the identification of better evidence-based recommendations.

Femoral neck system and cannulated compression screws in the treatment of non-anatomical reduction Pauwels type-III femoral neck fractures: A finite element analysis

BackgroundHigh shear force is a major factor detrimental to the healing of vertical femoral neck fractures. In addition to firm fixation, reduction quality is crucial for postoperative stability. The present study aimed to compare the biomechanical stability of the newly invented femoral neck system and three inverted-triangle cannulated compression screws treatments for non-anatomical reduction of Pauwels type-III femoral neck fractures. MethodsA total of 18 non-anatomical reduction Pauwels type-III femoral neck fracture finite element models were fabricated and fixed using three inverted-triangle cannulated compression screws or the femoral neck system. A 1950-N force was applied to the femoral head to simulate the physiological load during a single-leg stance. Parameters of the maximum total deformation, the interfragmentary gap, and the maximum von Mises stress of the implants and the proximal femur were analyzed. FindingsThe results of the maximum total deformation, interfragmentary gap, and maximum von Mises stress of the implants in the negative-negative buttress model fixed by the femoral neck system were the largest among all groups (3.58 mm, 0.252 mm, and 729.68 MPa, respectively). In contrast, the anatomical-anatomical reduction model fixed by three inverted-triangle cannulated compression screws demonstrated the minimum total deformation, interfragmentary gap, and minimum von Mises stress of implants (1.107 mm, 0.09 mm, and 189.83 MPa, respectively). InterpretationAnatomical reduction or positive buttress in femoral neck fractures should be recommended during fracture reduction. The femoral neck system showed weaker biomechanical stability than three inverted-triangle cannulated compression screws in treating Pauwels type-III femoral neck fractures.

What makes vertical femoral neck fracture with posterior inferior comminution different? An analysis of biomechanical features and optimal internal fixation strategy

Background and purposeFracture comminution occurs in 83.9%-94% of vertical femoral neck fractures (VFNFs), the majority of which were located in posterior-inferior region, and poses a clinical challenge in fixation stability. We conducted a subject-specific finite element analysis to determine the biomechanical features and optimal fixation selection for treating VFNF with posterior-inferior comminution. Patients and methodsEighteen models with three fracture types (VFNF without comminution [NCOM], with comminution [COM], with comminution + osteoporosis [COMOP]) and six internal fixation types (alpha [G-ALP], buttress [G-BUT], rhomboid [G-RHO], dynamic hip screw [G-DHS], invert triangle [G-ITR], femoral neck system (G-FNS)) were created based on the computed tomography data. By using the subject-specific finite element analysis method, stiffness, implant stress, yielding rate (YR) were compared. Additionally, in order to elucidate distinct biomechanical characters of different fracture types and fixation strategies, we calculated interfragmentary movement (IFM), detached interfragmentary movement (DIM), shear interfragmentary movement (SIM) of all fracture surface nodes. ResultsGenerally, in comparison with NCOM, COM showed a 30.6% reduction of stiffness and 1.46-times higher mean interfragmentary movement. Besides, COM had a 4.66-times (p = 0.002) higher DIM at the superior-middle position, but similar SIM across fracture line, which presented as varus deformation. In COM and COMOP, among all six fixation strategies, G-ALP had significantly the lowest IFM (p<0.001) and SIM (p<0.001). Although G-FNS had significantly highest IFM and SIM (p<0.001), it had the highest stiffness and lowest DIM (p<0.001). In COMOP, YR was the lowest in G-FNS (2.67%). ConclusionsPosterior-inferior comminution primarily increases superior-middle detached interfragmentary movement in VFNF, which results in varus deformation. For comminuted VFNF with or without osteoporosis, alpha fixation has the best interfragmentary stability and anti-shear property among six current mainstream fixation strategies, but a relatively weaker stiffness and anti-varus property compared to fixed-angle devices. FNS is advantageous owing to stiffness, anti-varus property and bone yielding rate in osteoporosis cases, but is insufficient in anti-shear property.

Comparison of femoral neck system and three cannulated cancellous screws in the treatment of vertical femoral neck fractures: clinical observation and finite element analysis

ObjectiveThe purpose of this study was to compare the biomechanical and clinical results of two surgical methods for the treatment of vertical femoral neck fractures: Femoral neck system (FNS) and traditional three cannulated cancellous screws (CCS).MethodsFirst, we developed three different vertical femoral neck fracture models for the finite element analysis, with angles of 55°, 65°, and 75°, respectively. Two experimental groups were set up: the FNS group and the CCS group. Each fracture group was tested under axial loads of 2100 N to measure the femur's displacement, Von Mises stress (VMS), and its internal fixation components. Secondly, we retrospectively included the cases of vertical femoral neck fractures with FNS and CCS in our hospital from May 2019 to May 2021. In this study, we compared the duration of intraoperative fluoroscopy, operative time, hospital stay, fracture healing time, Hemoglobin loss, Harris score of hip joint function, and postoperative complications among patients undergoing hip joint replacement.ResultsIn terms of finite element analysis, FNS has better anti-displacement stability than CCS at 55°and 65°, while FNS is greater than CCS in Von Mises stress. Clinically, we followed up on 87 patients for an average of 12 months. FNS was superior to traditional CCS in fracture healing time, operation time, fluoroscopy duration, fracture healing time, and Harris hip function score.ConclusionFNS is superior to traditional CCS in biomechanical and clinical aspects of treating vertical femoral neck fractures. There is potential for FNS to become a new treatment option for vertical femoral neck fractures.

Novel screw fixation placement configuration for the treatment of Pauwels type III femoral neck fractures: a finite element analysis.

Verticality of transcervical hip fractures in young patients is usually connected with typically high-energy fractures which are known as Pauwels type III. Artificial femoral head replacement surgery is mostly not considered for treating femoral neck fractures in such patients. The commonly used devices for the fixation of vertical femoral neck fractures are multiple screws or a sliding hip screw with or without an antirotation screw. Size, location and length of the screws are the most effective parameters in terms of the structural performance of internal fixation implants, but the optimal configuration of the screws is necessary to be investigated to direct the clinical practice. The aim of this study is to compare the biomechanical stability of the standard inverted triangle configuration with the various newly proposed x-crossed screw configurations. FEA simulations carried out in this study demonstrated that using an x-crossed-right assembly in treating Pauwels type III femoral neck fractures satisfies the biomechanical stability in terms of maximum von Mises stresses and maximum femoral head displacement. However, in terms of maximum relative neck fracture displacement, the x-crossed-right assembly would not entirely suffice the desired biomechanical stability. Therefore, using an x-crossed screw assembly in treating femoral neck fractures would provide the needed biomechanical stability.

Assessment of Internal Fixation Implants for Treating Vertical Femoral Neck Fractures through Finite Element Analysis

Assessment of Internal Fixation Implants for Treating Vertical Femoral Neck Fractures through Finite Element Analysis

Biomechanical evaluation of compression buttress screw and medial plate fixation for the treatment of vertical femoral neck fractures

ObjectiveTo compare the biomechanical properties of compression buttress screw (CBS) fixation with three plate fixation methods for the treatment of vertical femoral neck fractures (FNFs). MethodsA total of forty synthetic femoral models with simulated Pauwels type III fractures (angle of 70°) were equally assigned to one of four fixation groups: CBS fixation, anteromedial plate fixation (AMP), medial buttress plate fixation (MBP) and medial buttress plate fixation without proximal screw (MBPw). Within each group, half of the specimens were randomly assigned to two loading settings, an axial compression loading test and a hip-flexion torsion test. ResultsThere were no significant differences in axial load to failure, axial stiffness, torsional strength, or torsional stiffness when comparing CBS with MBP (p>0.05). In the axial compression loading test, both CBS and MBP showed higher load to failure and axial stiffness than MBPw (p<0.05). In torsional testing, AMP exhibited superior torsional strength and torsional stiffness than both MBPw and MBP (all p<0.05) and a higher torsional strength than CBS fixation (p<0.05). There were no significant differences in torsional stiffness between the CBS and AMP fixation groups (p>0.05). ConclusionThe biomechanical parameters of CBS fixation are comparable to that of AMP and MBP, and demonstrate superior axial stiffness than MBPw fixation. Although the CBS method for surgical fixation of vertical FNF holds promise as a less invasive surgical technique than plate fixation with similar biomechanical assessments, further clinical evaluation is warranted.

Outcome of valgus osteotomy in recent fracture of neck of femur with powels angle more than 50 degree

Background: Vertical femur neck fractures are prone to nonunion due to shear forces. This mechanical component that causes nonunion is corrected with intertrochanteric valgus osteotomy. Osteotomy has historically been reserved for fractures that have been neglected for more than three weeks or for nonunion following screw fixation failure. In the primary therapy of a fracture neck of the femur, valgus repositioning osteotomy is not a conventional method. In this study, we assess this management strategy as an alternate treatment for specific conditions. Patients and Methods: This study comprised 12 adult patients with recent vertical femoral neck fractures. The age ranged from 20 to 48 years old. Ten guys and two ladies were present. There were seven mid-cervical fractures and five subcapital fractures. Vertical fractures were treated with valgus osteotomy (angle more than 50 degrees). Due to renal insufficiency, three individuals developed osteoporotic fractures. The intertrochanteric osteotomy was performed to transform shear pressures into compression forces with the goal of reducing the fracture angle to 25 degrees. The average follow-up time was 45 months. Results: The average postoperative angle was 28 degrees.

Medial Locking Plate Can Increase the Fixation Stability of Vertical Femoral Neck Fracture in Young Adults?

Vertical femoral neck fractures in young adults are usually caused by a high-energy trauma. These injuries are difficult to stabilize due to significant shear forces acting on the fracture site. Their treatment is challenging and has a high risk of complications, such as fixation failure, malunion, nonunion and avascular necrosis of the femoral head. In recent years, several studies have focused on the use of direct reduction of vertical femoral neck fractures in young adult patients. This technique allows for anatomical reduction as well as the placement of an intra-articular implant to avoid shear forces at the fracture site. The aim of this study was to evaluate, based on in vitro experimental tests, the biomechanical stability provided by three different fixation methods: (i) dynamic hip screw with derotation screw, (ii) cannulated screws with a conventional medial bone plate and (iii) cannulated screws with a locked medial bone plate. For the biomechanical tests, these techniques were applied to reduce the vertical osteotomy performed on synthetic bones for later verification of the mechanical behavior under axial cyclic loading and destructive axial loading. There were no statistical differences in stiffness, micromovement displacement and mechanical strength during the biomechanical comparison of the fixation methods. Therefore, we conclude that the use of a conventional medial bone plate associated with cannulated screws, with a transverse trochanteric screw, supports the mechanical demand while the fracture is healing and this option can be used to stabilize vertical femoral neck fractures in young patients.

Comparison of Transverse Cancellous Lag Screw and Ordinary Cannulated Screw Fixations in Treatment of Vertical Femoral Neck Fractures

Aim of the Work: To compare the clinical therapeutic effect of transverse cancellous lag screw (TCLS) fixations and ordinary cannulated screw (OCS) fixations for vertical femoral neck fractures. Patients and Methods: This prospective randomized controlled study was conducted in Ain Shams University hospitals and El-Zaitoun hospital in Cairo. It included twenty two cases, who sustained femoral neck fractures. Patients were divided into 2 groups; Group A: using ordinary cannulated screws as a method of fixation. Group B: using transverse lag screws as a method of fixation. A randomized controlled study involved twenty two cases, who complained of fracture neck femur femoral neck fractures. Results: There was statistically significant slightly improved in TCLS group compared to OCS group. The results showed 5 patients out of 22 having complications, 2 patients (18.2%) belong to TCLS Group compared to 3 patients (27.3%) belong to OCS group, with avascular Necrosis 1 patient (9.1%) in TCLS regarding Neck Shortening 1 patient (9.1%) in TCLS and 2 patients (18.2%) OCS group. Regarding Non Union 1 patient (9.1%) in OCS group, there were high complications in OCS group compared to TCLS group but insignificant. Conclusion: A new study suggests that using the TCLS method to treat vertical femoral neck fractures may improve hip function and reduce neck shortening rates. Type III femoral neck fractures in Pauwels patients may benefit from this study's findings. Keywords: transverse cancellous lag screw, ordinary cannulated screw, fixation, vertical femoral neck, fractures

Clinical and Biomechanical Effects of Femoral Neck Buttress Plate used for Vertical Femoral Neck Fractures

PurposeTo investigate both the biomechanical and clinical effect of an inferomedial femoral neck buttress plate (FNBP) used to augment a sliding hip screw (SHS) and anti-rotational screw (ARS) in the treatment of traumatic vertical femoral neck fractures. MethodsPart 1: Clinical - Retrospective review of patients under age 65 treated with open reduction of a vertical femoral neck fracture. Patients were divided into two groups: Group 1 patients (18 patients) had SHS/ARS fixation augmented with a FNBP, while Group 2 patients (18 patients) had SHS/ARS fixation alone and were matched for age and sex. Demographic data, OTA fracture classification, immediate post-operative and follow-up radiographs were analyzed for quality of reduction, femoral neck shortening (FNS), neck-shaft angle (NSA), avascular necrosis (AVN) and union.Part 2: Biomechanical - Pauwels III femoral neck osteotomy was created in five pairs of cadaveric specimens, then each fracture was reduced and stabilized with a SHS/ARS construct. Specimens were matched and split into Groups 1 and 2, similar to Part 1. Cadaveric specimens were axially loaded in cyclical fashion to analyze for construct stiffness, fracture displacement femoral neck shortening and changes in the neck shaft angle. ResultsPart 1: There were 18 matched patients (14 males and 4 females) in both Group 1 and Group 2. There were no statistically significant differences between the two groups with respect to Pauwels angle, femoral neck shortening, changes in neck-shaft angle, AVN or nonunion. One reoperation in Group 1 and four in Group 2.Part 2: All five cadaveric specimens in both groups survived the 10,000-cycle loading regimen. We were unable to detect any significant differences between the two groups with respect to construct stiffness, change in neck-shaft angle or amount of femoral neck shortening. ConclusionBased on the results of both clinical case series and biomechanical testing, an inferomedial neck buttress plate does not appear to offer long-term benefits with respect to maintenance of alignment or achieving union but may potentially help in obtaining the reduction.

Mapping of Vertical Femoral Neck Fractures in Young Patients Using Advanced 2 and 3-Dimensional Computed Tomography.

To better describe the pathoanatomy of young patients' femoral neck fractures with the goal of improving surgeons' decisions for treatment including reduction and fixation. This is a retrospective study of patient records, plain radiographs, and the modern computed tomography scans to study the pathoanatomy of Pauwels II and III femoral neck fractures (coronal angle >30 degrees) in young adults. One American College of Surgeons Level 1 trauma center. All patients 18-49 years of age with a surgically repaired Pauwels' II and III (>30 degrees) femoral neck fracture between 2013 and 2017. Fifty-six adult patients younger than 50 years were identified with a femoral neck fracture in the study period, of whom 30 met study criteria. We evaluated plain radiography and computed tomography data including fracture orientation, characteristics of fracture morphology including size, shape, and dimensions, comminution, displacement, and deformity. Fracture morphology typically included a wide-based caudal head-neck segment (80%) that ends at a variable location along the medial calcar, sometimes as caudal as the lesser trochanter. Comminution was present in 90% of cases mostly located in the inferior quadrant, but anterior or posterior to the void left by the head-neck's caudal segment. The fractures orientations and deformities were reported by means and ranges. We investigated and reported on the pathoanatomy of high-energy femoral neck fractures in young adults with the goal of increasing understanding of the injury and improving surgeons' ability to provide for improved treatment decisions and quality fracture repair. Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Fixation effects of different types of cannulated screws on vertical femoral neck fracture: A finite element analysis and experimental study

Femoral neck fractures (FNFs) in young patients usually result from high-energy violence, and the vertical transcervical type is typically challenging for its instability. FNFs are commonly treated with three cannulated screws (CS), but the role of screws type on fixation effects (FE) is unclear. The purpose of this study was to evaluate the FE of ten types of CS with different diameters, lengths, depths, and pitches of thread via finite element analysis which was validated by a biomechanical test. Ten vertical FNF models were grouped, fixed by ten types of CS, respectively, all in a parallel, inverted triangular configuration. Their FE were scored comprehensively from six aspects via an entropy evaluation method, as higher scores showed better results. For partial-thread screws, thread length and thread shape factor (TSF) are determinative factors on stability of FNF only if thread depth is not too thick, and they have less cut-out risk, better compression effects and better detached resistance of fracture than full-thread screws, whereas full-thread screws appear to have better shear and shortening resistance. A combination of two superior partial-thread screws and one inferior full-thread screw for vertical FNF may get optimal biomechanical outcomes. The type of cannulated screw is important to consider when treating vertical FNF.

Biomechanical study of two alternative methods for the treatment of vertical femoral neck fractures – A finite element analysis

BackgroundNo consensus has been reached for the treatment of vertical femoral neck fractures (vFNFs). Recently, two alternative methods were invented to treat vFNFs, one of which is a new plate with a sliding groove, which was designed as a substitution of the medial buttress locking plate to combine with cannulated compression screws (CCS) for reducing the breakage possibility of the proximal locking screw during the bone healing. Another one is the femoral neck system (FNS), which was believed with biomechanical superiority. This study aims to compare the biomechanics of these two new implants with three previous methods via finite element analysis (FEA) to validate whether they are suitable for the treatment of vFNFs. MethodsFive 70-degree Pauwels type III transcervical FNFs (vFNFs, AO/OTA 31B2.3r) models were built and fixed by CCS augmented with the newly designed sliding groove buttress plate (CCS+BS) and FNS. For comparison, models fixed by three parallel cannulated compression screws (CCS), biplane double-supported screw fixation (BDSF), CCS augmented with a medial buttress locking plate (CCS+BL) were also built. A 2100N load was applied along with the mechanical axis. Parameters of the maximal stress as well as the maximal displacement of the implants and bone, the maximal relative displacement of interfragments, and the stiffness, were analyzed to compare the biomechanical characteristics of the five models. ResultsCCS+BS and CCS+BL showed stronger fixation strength with improved stiffness (1012.05N/mm, 1092.04N/mm), reduced maximal displacement of the implants (1.976mm, 1.838mm) and bone (2.075mm, 1.923mm), when compared with CCS (925.11N/mm, 2.158mm and 2.270mm) and BDSF (842.36N/mm, 2.299mm and 2.493mm). While FNS showed the weakest stiffness (593.22N/mm) and largest maximal displacement of the implants (3.234mm) and bone (3.540mm) among the five models. ConclusionsCCS+BS has a better biomechanical performance than CCS and BDSF, which offers a new choice to deal with vFNFs. The construction stability of FNS is weaker than CCS, BDSF, and CCS+BL, indicating that this method may not as stable as reported in the previous study.

Enhanced interfragmentary stability and improved clinical prognosis with use of the off-axis screw technique to treat vertical femoral neck fractures in nongeriatric patients

BackgroundThe optimal internal fixation strategy for vertical femoral neck fractures (VFNFs) in nongeriatric patients remains uncertain. Therefore, the purpose of this study was to compare the clinical prognoses and underlying mechanical characteristics of a novel off-axis screw technique with dynamic hip screws (DHSs) and three traditional parallel screws.MethodsThis study included a clinical investigation and a patient-specific finite element analysis (FEA). In the clinical investigation, VFNF patients were grouped by fixation type: (1) use of three parallel screws (G-TRI); (2) augmentation with an off-axis screw (G-ALP); and (3) DHS with an anti-rotational screw (G-DHS). Fixation failures (nonunion, femoral neck shortening (FNS), varus deformation, screw cut-out) and avascular necrosis (AVN) consequent to the three types of fixations were compared. In the FEA, twenty-four fixation models with the three fixation types were created based on the data of eight healthy volunteers. Models were assessed under walking conditions. Stiffness, interfragmentary motion (IFM), and implant stress were evaluated.ResultsIn the clinical investigation, the fixation failure rate was significantly (p < 0.05) lower in G-ALP (18.5%) than in G-DHS (37.5%) and G-TRI (39.3%). No significant difference in AVN was observed among the three fixation groups. In the FEA, stiffness and implant stress in the G-DHS models were significantly (p < 0.05) higher, and the IFM of G-ALP was significantly (p < 0.05) lower among the groups.ConclusionsAmong fixation types for VFNFs, the off-axis screw technique exhibited better interfragmentary stability (lowest IFM) and a lower fixation failure rate (especially FNS). Analyzing interfragmentary stability in biomechanical experiments is more consistent with clinical prognosis than construct stability for VFNFs, suggesting that internal fixations should aim for this outcome.