Comparison of Three Fixation Methods for Femoral Neck Fracture in Young Adults: Experimental and Numerical Investigations

Biomechanical study of a biplanar double support screw (BDSF) technique based on Pauwels angle in femoral neck fractures: finite element analysis

Objective

The objective of the present study is to conduct a comparative analysis of the biomechanical advantages and disadvantages associated with a biplanar double support screw (BDSF) internal fixation device.

Methods

Two distinct femoral neck fracture models, one with a 30° angle and the other with a 70° angle, were created using a verified and effective finite element model. Accordingly, a total of eight groups of finite element models were utilized, each implanted with different configurations of fixation devices, including distal screw 150° BDSF, distal screw 165° BDSF, 3 CLS arranged in an inverted triangle configuration, and 4 CLS arranged in a "α" configuration. Subsequently, the displacement and distribution of Von Mises stress (VMS) in the femur and internal fixation device were assessed in each fracture group under an axial load of 2100 N.

Results

At Pauwels 30° Angle, the femur with a 150°-BDSF orientation exhibited a maximum displacement of 3.17 mm, while the femur with a 165°-BDSF orientation displayed a maximum displacement of 3.13 mm. When compared with the femoral neck fracture model characterized by a Pauwels Angle of 70°, the shear force observed in the 70° model was significantly higher than that in the 30° model. Conversely, the stability of the 30° model was significantly superior to that of the 70° model. Furthermore, in the 70° model, the BDSF group exhibited a maximum femur displacement that was lower than both the 3CCS (3.46 mm) and 4CCS (3.43 mm) thresholds.

Conclusion

The biomechanical properties of the BDSF internal fixation device are superior to the other two hollow screw internal fixation devices. Correspondingly, superior biomechanical outcomes can be achieved through the implementation of distal screw insertion at an angle of 165°. Thus, the BDSF internal fixation technique can be considered as a viable closed reduction internal fixation technique for managing femoral neck fractures at varying Pauwels angles.

Effect of different constraining boundary conditions on simulated femoral stresses and strains during gait

Finite element analysis (FEA) is commonly used in orthopaedic research to estimate localised tissue stresses and strains. A variety of boundary conditions have been proposed for isolated femur analysis, but it remains unclear how these assumed constraints influence FEA predictions of bone biomechanics. This study compared the femoral head deflection (FHD), stresses, and strains elicited under four commonly used boundary conditions (fixed knee, mid-shaft constraint, springs, and isostatic methods) and benchmarked these mechanics against the gold standard inertia relief method for normal and pathological femurs (extreme anteversion and retroversion, coxa vara, and coxa valga). Simulations were performed for the stance phase of walking with the applied femoral loading determined from patient-specific neuromusculoskeletal models. Due to unrealistic biomechanics observed for the commonly used boundary conditions, we propose a novel biomechanical constraint method to generate physiological femur biomechanics. The biomechanical method yielded FHD (< 1 mm), strains (approaching 1000 µε), and stresses (< 60 MPa), which were consistent with physiological observations and similar to predictions from the inertia relief method (average coefficient of determination = 0.97, average normalized root mean square error = 0.17). Our results highlight the superior performance of the biomechanical method compared to current methods of constraint for  both healthy and pathological femurs.

Numerical evaluation of internal femur osteosynthesis based on a biomechanical model of the loading in the proximal equine hindlimb

Femoral fractures are often considered lethal for adult horses because femur osteosynthesis is still a surgical challenge. For equine femur osteosynthesis, primary stability is essential, but the detailed physiological forces occurring in the hindlimb are largely unknown. The objective of this study was to create a numerical testing environment to evaluate equine femur osteosynthesis based on physiological conditions. The study was designed as a finite element analysis (FEA) of the femur using a musculoskeletal model of the loading situation in stance. Relevant forces were determined in the musculoskeletal model via optimization. The treatment of four different fracture types with an intramedullary nail was investigated in FEA with loading conditions derived from the model. The analyzed diaphyseal fracture types were a transverse (TR) fracture, two oblique fractures in different orientations (OB-ML: medial-lateral and OB-AP: anterior-posterior) and a "gap" fracture (GAP) without contact between the fragments. For the native femur, the most relevant areas of increased stress were located distally to the femoral head and proximally to the caudal side of the condyles. For all fracture types, the highest stresses in the implant material were present in the fracture-adjacent screws. Maximum compressive (-348 MPa) and tensile stress (197 MPa) were found for the GAP fracture, but material strength was not exceeded. The mathematical model was able to predict a load distribution in the femur of the standing horse and was used to assess the performance of internal fixation devices via FEA. The analyzed intramedullary nail and screws showed sufficient stability for all fracture types.

Comparison of different internal fixation implants in the treatment of talar neck fractures: A finite element analysis

OBJECTIVES

This study aimed to analyze the biomechanics of cannulated screws (CS) with or without a lateral locking plate (LLP) in talar neck fractures through a finite element analysis.

PATIENTS AND METHODS

The computed tomography image of the talus from a healthy volunteer (adult male) was used to reconstruct a three-dimensional talar model. The method for fixing talar neck fractures with CS and an LLP was planned using computer-aided design software. Afterward, the three-dimensional models of comminuted talar neck fractures were used to simulate fixation with anteroposterior parallel dual CS, single CS+LLP, and dual CS+LLP. Finally, finite element analysis was carried out to compare the outcomes of dual CS+LLP to those of single CS+LLP and to those of using dual CS alone. The displacement and von Mises stress values of the three groups with different internal fixation were analyzed.

RESULTS

For a simple talar neck fracture, the lowest amount of displacement was obtained with CS+LLP (0.407 mm), while dual CS (0.459 mm) showed the highest amount of total displacement; the lowest amount of peak stresses was obtained with CS+LLP (5.38 MPa), while dual CS (8.749 MPa) showed the highest amount of total peak stresses. For a comminuted talar neck fracture, the lowest amount of displacement was obtained with CS+LLP (0.398 mm), while dual CS (0.408 mm) showed the highest amount of total displacement; the lowest amount of peak stresses was obtained with CS+LLP (129.9 MPa), while dual CS (205.9 MPa) showed the highest amount of peak stresses.

CONCLUSION

Compared to the other two groups, the dual CS+LLP group had better biomechanics properties in the displacement and stress peak of the talus and implant. Thus, the use of dual CS+LLP fixation is recommended for the surgical treatment of comminuted talar neck fractures.

Outcomes of three cannulated screws in a modified triangular transverse configuration for fixation of intra-capsular femoral neck fractures

BACKGROUND

Intra-capsular femoral neck fractures (FNF) are commonly encountered in trauma settings and are associated with high rates of morbidity and mortality. One of the most used methods of FNF treatment is the use of multiple cannulated screws. Many different screw constructs are reported in the literature, with no evidence of superiority of one construct over others. We present a series of patients treated by one senior surgeon with three cannulated screws positioned in a specific configuration.

MATERIALS AND METHODS

We conducted a retrospective monocentric analysis. All charts of patients hospitalized between January 2004 and June 2022 for an intra-capsular femoral neck fracture treated by three cannulated screws by the same senior surgeon were retrieved and analyzed. The clinical and radiological evaluations were performed by two independent researchers. Functional status of patients was assessed using the modified Harris Hip score (mHHS). Complications such as secondary displacement, non-union, avascular necrosis (AVN) and femoral neck shortening were all recorded.

RESULTS

A total of 38 patients met the inclusion criteria. There were 17 males and 21 females with an average age of 66.3 ± 13.6 years and a follow-up period of 16 ± 20 months. Bone union was observed in 34 (89.5%) patients. Mild shortening was observed in two patients (5.2%) with no functional limitation. Four patients (10.5%) underwent reoperations, three due to another fall and one due to AVN four years post-fracture fixation.

CONCLUSION

In our series, we demonstrate that the use of three cannulated screws in a triangular transverse configuration for fixation of intra-capsular femoral neck fractures provides excellent results with low rates of femoral neck shortening, AVN or non-union.

Busch-Hoffa fracture: A systematic review

BACKGROUND

Accomplish a thorough review on the existing biomechanical and clinical studies about coronal plane fractures of the distal femur.

METHODS

We performed an electronic search of PubMed/MEDLINE database from April to June, 2023. The terms for the database search included "Hoffa fractures," OR "Busch-Hoffa fractures" OR "coronal plane fractures of the distal femur."

RESULTS

The search identified 277 potentially eligible studies. After application of inclusion and exclusion criteria, 113 articles were analyzed in terms of the most important topics related to coronal plane fractures of the distal femur.

CONCLUSION

Lateral coronal plane fractures of the distal femur are more frequent than medial, present a more vertical fracture line, and usually concentrate on the weight bearing zone of the condyle. The Letenneur system is the most used classification method for this fracture pattern. Posterior-to-anterior fixation using isolated lag screws (for osteochondral fragments-Letenneur type 2) or associated with a posterior buttressing plate (when the fracture pattern is amenable for plate fixation-Letenneur types 1 and 3) is biomechanically more efficient than anterior-to-posterior fixation. Anterior-to-posterior fixation using lag screws complemented or not by a plate remains a widely used treatment option due to the surgeons' familiarity with the anterior approaches and lower risk of iatrogenic neurovascular injuries. There is no consensus in the literature regarding diameter and number of screws for fixation of coronal plane fractures of the distal femur.

Identification of screw spacing on pediatric hip locking plate in proximal femoral osteotomy

This study describes a computational analysis technique for evaluating the effect of screw spacing and angle on the pediatric hip locking plate system in proximal femoral osteotomy in pediatric patients having DDH with an aberrant femoral head and femoral angle. Under static compressive load conditions, the stresses of the screw and bone were examined as the screw spacing and angle changed. The spacing and angle of various screws were specifically considered as variables in this study based on the pile mechanism studied in civil engineering. As with the group pile mechanism, the tighter the screw spacing under static compressive loads, the more the overlapping effect between the bone stresses and the screws develops, increasing the risk of injuring the patient's bone. Therefore, a series of simulations was performed to determine the optimal screw spacing and angles to minimize the overlapping effect of bone stress. In addition, a formula for determining the minimum screw spacing was proposed based on the computational simulation results. Finally, if the outcomes of this study are applied to pediatric patients with DDH in the pre-proximal femoral osteotomy stage, post-operative load-induced femur damage will be reduced.

Titanium alloy cannulated screws and biodegrade ceramic nails for treatment of femoral neck fractures: A finite element analysis

BACKGROUND

Our previous studies have demonstrated the mechanical effect of sclerosis around screw paths on the healing of femoral neck fractures (FNF) after internal fixation. Furthermore, we discussed the possibility of using bioceramic nails (BNs) to prevent sclerosis. However, all these studies were conducted under static conditions as the patient was standing on one leg, while the effect of the stress generated during movement is unknown. The purpose of this study was to evaluate the stress and displacement under dynamic stress loading conditions.

METHODS

Two types of internal fixation, namely cannulated screws and bioceramic nails, were utilized in conjunction with various finite element models of the femur. These models included the femoral neck fracture healing model, the femoral neck fracture model, and the sclerosis around screws model. The resulting stress and displacement were analyzed by applying the contact forces associated with the most demanding activities during gait, including walking, standing, and knee bending. The present study establishes a comprehensive framework for investigating the biomechanical properties of internal fixation devices in the context of femoral fractures.

RESULTS

The stress at the top of the femoral head in the sclerotic model was increased by roughly 15 MPa during the knee bend and walking phases and by about 30 MPa during the standing phase compared to the healing model. The area of high stress at the top of the femoral head was increased during the sclerotic model's walking and standing phases. Additionally, the stress distribution throughout the dynamic gait cycle was comparable before and after the removal of internal fixations following the healing of the FNF. The overall stress distribution of the entire fractured femoral model was lower and more evenly distributed in all combinations of internal fixation. Furthermore, the internal fixation stress concentration was lower when more BNs were used. In the fractured model with three cannulated screws (CSs), however, the majority of the stress was concentrated around the ends of the fractures.The maximal stress in the healing model with one CS and two BNs was the highest at all stages of gait over three combinations of internal fixation, and the stress was mainly carried by CS.

CONCLUSIONS

The presence of sclerosis around screw paths increases the risk of femoral head necrosis. Removal of CS has little effect on the mechanics of the femur after healing of the FNF. BNs have several advantages over conventional CSs after FNF. Replacing all internal fixations with BNs after the healing of FNF may solve the problem of sclerosis formation around CSs to improve bone reconstruction owing to their bioactivity.

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.

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.

Prevention of sclerosis around cannulated screw after treatment of femoral neck fractures with bioceramic nails: a finite element analysis

PURPOSE

Conventional cannulated screws (CS) are the main treatment method for femoral neck fractures (FNF). However, the rate of femoral head necrosis remains high after FNF treatment. The study aimed to compare the biomechanical features of different internal fixation materials for the treatment of Pauwel type III FNF to explore new strategies for clinical management.

METHODS

A new material was prepared by applying casting, freeze drying and sintering process. The independently developed calcium magnesium silicate ceramic powder and hydrogel solution were evenly mixed to obtain a high-viscosity bio-ink, and a bioceramic nail (BN) with high mechanical strength and high fracture toughness was successfully prepared. Four internal fixations were developed to establish the Pauwel type III FNF and healed fracture finite element models: A, three CSs; B, three BNs; C, two BNs and one CS; D, one BN and two CSs. Von Mises stress and displacement of the implants and femur were observed.

RESULTS

The measured Mg content in ceramic powder was 2.08 wt%. The spectral data confirmed that the ceramic powder has high crystallinity, which coincides with the wollastonite-2 M (PDF# 27-0088). The maximum von Mises stresses for the four models were concentrated in the lower part of the fracture surface, at 318.42 Mpa, 103.52 MPa, 121.16 MPa, and 144.06 MPa in models A, B, C, and D, respectively. Moreover, the maximum Von-mises stresses of the implants of the four models were concentrated near the fracture end at 243.65 MPa (A) and 58.02 MPa (B), 102.18 MPa (C), and 144.06 MPa (D). The maximum displacements of the four models were 5.36 mm (A), 3.41 mm (B), 3.60 mm (C), and 3.71 mm (D). The displacements of the three models with BNs were similar and smaller than that of the triple CS fracture model. In the fracture healing models with and without three CSs, the greatest stress concentration was scattered among the lowest screw tail, femoral calcar region, and lateral femur shaft. The displacement and stress distributions in both models are generally consistent. The stress distribution and displacement of the three healed femoral models with BNs were essentially identical to the healing models with three CSs. The maximum von Mises stresses were 65.94 MPa (B), 64.61 MPa (C), and 66.99 MPa (D) while the maximum displacements of the three healed femoral models were 2.49 mm (B), 2.56 mm (C), and 2.49 mm (D), respectively.

CONCLUSIONS

Bioceramic nails offer greater advantages than conventional canulated screws after femoral neck fractures. However, the combination of bioceramic nails and CSs is more clinically realistic; replacing all internal fixations with bioceramic nails after the healing of femoral neck fractures can solve the problem of sclerosis formation around CSs and improve bone reconstruction by their bioactivity.

Trajectory of bolt and length of plate in femoral neck system determine the stability of femur neck fracture and risk of subsequent subtrochanteric fracture : a finite element analysis

BACKGROUND

This study aimed to analyze the differences in the stability of fractures, stress distribution around the distal-most screw according to the length of the plate and the trajectory of the bolt in Pauwels type III femoral neck fracture using the femoral neck system (FNS).

METHODS

Finite element models of Pauwels type III femoral neck fractures were established with surgical variations in the trajectory of the bolt (central, inferior, valgus, and varus) and length of the lateral plate (1- and 2-hole plate). The models were subsequently subjected to normal walking and stair-climbing loads.

RESULTS

The screw-holding cortical bone in subtrochanter in the model with a 2-hole plate and the bolt in the inferior trajectory and the models with 1-hole or 2-hole plate and the bolt in valgus trajectory had shown greater maximum principal strain than the models with central or varus trajectories. The gap and sliding distance on the fracture surface were larger with inferior or varus trajectories of the bolt and smaller with the valgus trajectory of the bolt under both loads, compared to those of the central trajectory.

CONCLUSION

For the fixation of Pauwels type III femoral neck fracture, the trajectory of the FNS bolt and the length of the plate affect the mechanical stability of the fracture and the strain of cortical bone around the distal-most screw. The surgical target should stay on the central trajectory of the bolt and the 2-hole plate's mechanical benefits did not exceed the risk.

Pipkin Type-II Femoral Head Fracture - A Biomechanical Evaluation by the Finite-Element Method

Objective  To evaluate the biomechanical capacity of two forms of fixation for Pipkin type-II fractures, describing the vertical fracture deviation, the maximum and minimum principal stresses, and the Von Mises equivalent stress in the syntheses used. Materials and Methods  Two internal fasteners were developed to treat Pipkin type-II fractures through finite elements: a 3.5-mm cortical screw and a Herbert screw. Under the same conditions, the vertical fracture deviation, the maximum and minimum principal stresses, and the Von Mises equivalent stress in the syntheses used were evaluated. Results  The vertical displacements evaluated were of 1.5 mm and 0.5 mm. The maximum principal stress values obtained in the upper region of the femoral neck were of 9.7 KPa and 1.3 Kpa, and the minimum principal stress values obtained in the lower region of the femoral neck were of -8.7 KPa and -9.3 KPa. Finally, the peak values for Von Mises stress were of 7.2 GPa and 2.0 GPa for the fixation models with the use of the 3.5-mm cortical screw and the Herbert screw respectively. Conclusion  The fixation system with the Herbert screw generated the best results in terms of reduction of vertical displacement, distribution of the maximum principal stress, and the peak Von Mises equivalent stress, demonstrating mechanical superiority compared to that of the 3.5-mm cortical screw in the treatment of Pipkin type-II fractures.

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

OBJECTIVE

The 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).

METHODS

First, 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.

RESULTS

In 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.

CONCLUSION

FNS 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.

Femoral neck fractures treated with cannulated screws: can surgeons predict functional outcomes and minimize the risk of necrosis?

BACKGROUND AND AIM

Femoral neck fractures are among the most frequent in mankind. Screw fixation is considered a suitable approach specially for undisplaced or slightly displaced fractures that occur to young patients. We conducted our study in order to evaluate both functional outcomes and complication rates of patients who received this treatment in our institution. A particular focus was given to the aseptic necrosis of the head, trying to identify if anamnestic, clinical or radiological data could play a significant role as prognostic factors.

METHODS

For each case who was treated with screw fixation due to a femoral neck fracture, we recorded data regarding, among the others, BMI and whether they used tobacco products or corticosteroids on a regular basis. Necrosis of the femoral head and mechanical complications were recorded. Functional outcome was evaluated using the Harris Hip Score.      Results: 74 cases were included in our study. The mean Harris Hip score was 89.5. Aseptic necrosis of the femoral head occurred in 9 cases (12.2%). Regular use of tobacco was associated with a higher risk to develop necrosis (p=0.007). The Body Mass Index was significantly higher in cases who had necrosis compared to the rest of our population (p=0.043) and was inversely proportional to the post-operative Harris hip score (p=0.001).

CONCLUSIONS

While considering screw fixation to treat cases with femoral neck fractures, patient's weight and use of tobacco should be considered as prognostic factors.  (www.actabiomedica.it).

What makes fixation of femoral neck fractures fail? A systematic review and meta-analysis of risk factors

INTRODUCTION

This systematic review aims to provide an overview of predictors for failure of treatment of displaced femoral neck fracture (dFNF) with internal fixation and quantify their risk of fixation failure in a meta-analysis.

PATIENTS AND METHODS

PubMed, Embase, Web of Science, Cochrane Library, and EMCare were searched for original studies published from January 2000, including adult patients with an internally fixated dFNF, that reported data on predictors for fixation failure defined as revision surgery due to non-union, avascular femoral head necrosis or cut-out of implant. RevMan version 5 software was used to pool univariable Odds Ratio's (OR) for predictors of fixation failure by means of a random effects model.

RESULTS

This review included 16 articles (15 articles cohort studies and one randomised trial). Twenty-four predictors for fixation failure were identified and analysed, 16 of which were evaluated in just one study. Data of 7 predictors were pooled in a meta-analysis. Female sex (OR 1.78, 95% confidence interval [CI] 1.26-2.52), smoking (OR 3.64, 95% CI 1.68-7.91), age >50 years (OR 3.64, 95% CI 1.68-7.91), inadequate fracture reduction (OR 2.28, 95% CI 1.62-3.22), fixation with cannulated screws (CS) or pins compared to fixed angle devices (OR 2.16, 95% CI 1.03-4.54) were identified as significant predictors for fixation failure.

CONCLUSION

This study can help surgeons to choose the preferred treatment for patients with a dFNF and substantiate future algorithms and guidelines for treatment of FNF.

Femoral neck fractures in non-geriatric patients: femoral neck system versus cannulated cancellous screw

BACKGROUND

The fractures of femoral neck account for 50% among hip fractures with around 3%-10% occurring in younger population of below 65 years. The newly introduced FNS as management approach appears to be a potential alternative to the traditional CCS. The aim of this study was to compare the clinical efficacy and outcome of the femoral neck system (FNS) and the cannulated cancellous screw (CCS) in the treatment of femoral neck fractures in adult below 65 years of age.

METHODS

Data of 114 patients between 18-65 years, admitted in our department for femoral neck fracture from January 2019 to March 2021 were retrospectively studied and ranged into two groups based on the surgical methods: FNS group (56 patients) and CCS group (58 patients). The variables of interest including demographic and clinical variables (age, gender, fracture mechanism, injury side and classification), perioperative parameters(operation time, intraoperative bleeding, incision length and hospitalization time), postoperative outcomes and complications (fracture healing time, nonunion rate, femoral neck avascular necrosis, aseptic screw loosening and the Harris Hip Score), were analyzed and compared between the two groups.

RESULTS

All 114 patients presented satisfactory reduction and were followed-up for a period of 12 to 36 months (mean 27 ± 2.07 months); there were no significant differences between both groups in terms of age, gender, fracture classification, side of injury, mechanism of injury, the operative time, intraoperative blood loss and the hospital length of stay. However, the fracture healing time between FNS group and CCS group was statistically significant (p < 0.05), respectively 2.86 ± 0.77 and 5.10 ± 0.81 months. The significant differences were also found in terms of numbers of fluoroscopies 8.34 ± 1.38 Vs 17.72 ± 2.19, the HHS 87.80 ± 1.92 Vs 84.28 ± 2.24, postoperative complications 8 (14.28%) Vs 26 (44.82) respectively in FNS and CCS group.

CONCLUSION

FNS presented satisfactory outcomes had significantly lower complications rate, therefore, can be one of the alternatives for internal implantation devices in treatment of femoral neck fracture in non-geriatric population.

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.

Finite element comparative analysis of three different internal fixation methods in the treatment of Pauwels type III femoral neck fractures

BACKGROUND

Comparison of 4 cannulated lag screws (3 inverted triangular cannulated screws + anti-rotating screws;4 CLS), dynamic hip screws + derotational screws (DHS + DS), and femoral neck fixation system (FNS) in the treatment of Biomechanical properties of middle-aged Pauwels type III femoral neck fractures.

METHODS

The femur CT data of a healthy young volunteer was selected and imported into Mimics software to construct a three-dimensional model of a normal femur. Pauwels type III femoral neck fractures were simulated according to the 70° fracture line. Use Geomagic and SolidWorks software to optimize and build CLS, DHS + DS, and FNS fracture internal fixation models. Finally, Ansys software was used to analyze the stress distribution, peak value, and maximum displacement of the proximal fracture fragment and internal fixation; the displacement distribution, and peak value of the fracture surface at the fracture end.

RESULTS

① The stress peaks of the proximal fracture fragments in the three groups were concentrated near the femoral calcar. The peak stress of the FNS group was the largest, and the DHS + DS group was the smallest. ②The displacement of the fracture fragments was all located at the top of the femur. The peak displacement of the FNS group was the largest, and the DHS + DS group was the smallest. ③ The internal fixation stress of the three groups is concentrated in the middle part of the device. The stress distribution of the first two groups of models is more uniform than that of FNS. The peak stress of FNS is the largest and the CLS is the smallest. ④ The internal fixed displacements are all located at the top of the model. The peak displacement of the CLS is the largest, and the DHS + DS is the smallest. ⑤ The displacement of the fracture surface is in the upper part of the fractured end. The peak displacement of the FNS group was the largest, and the DHS + DS group was the smallest.

CONCLUSION

Compared with the other two internal fixation methods, dynamic hip screw + derotational screw (DHS + DS) showed good biomechanical stability. When Pauwels type III femoral neck fracture occurs in young adults, DHS + DS can be given priority as the preferred treatment for this type of fracture.

Efficacy of the femoral neck system in femoral neck fracture treatment in adults: A systematic review and meta-analysis

BACKGROUND

Controversy remains around the available choices for the internal fixation of a femoral neck fracture. The femoral neck system (FNS) was developed in 2018 and has been widely applied since then as it can provide rigid fixation stability with less damage to the bone mass around the fracture. However, no systematic reviews and meta-analyses have investigated the efficacy of the FNS in comparison with that of traditional internal fixation in the treatment of femoral fractures.

AIM

To assess the efficacy of the FNS in comparison with that of cannulated compression screws (CCS) in the treatment of femoral fractures through systematic review and meta-analysis.

METHODS

Five electronic databases (PubMed, Embase, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, and Wanfang) were searched from the earliest publication date to December 31, 2021. Reference Citation Analysis (https://www.referencecitationanalysis.com/) was used to check the results and further analyze the related articles. Controlled trials were included if the FNS was applied for the femoral neck fracture in adults and if it was compared with CCS for the achievement of internal fixation. The measurement outcomes included the required operation time, observed patient’s blood loss, extent of fracture healing, patient’s Harris Hip score (HHS) at the last follow-up, and records of any complications (such as failure of internal fixation, femoral neck shortness, avascular necrosis of the femoral head, and delayed union or nonunion).

RESULTS

Ten retrospective controlled studies (involving 711 participants) were included in this meta-analysis. The meta-analysis showed that compared with CCS, use of the FNS could not decrease the operation time [standardized mean difference (SMD): -0.38, 95% confidence interval (CI): -0.98 to 0.22, P = 0.21, I² = 93%), but it could increase the intraoperative blood loss (SMD: 0.59, 95%CI: 0.15 to 1.03, P = 0.009, I² = 81%). The pooled results also showed that compared with CCS, the FNS could better promote fracture healing (SMD: -0.97, 95%CI: -1.65 to -0.30, P = 0.005, I² = 91%), improve the HHS at the last follow-up (SMD: 0.76, 95%CI: 0.31 to 1.21, P = 0.0009, I² = 84%), and reduce the chances of developing femoral neck shortness (OR: 0.29, 95%CI: 0.14 to 0.61, P = 0.001, I² = 0%) and delayed union or nonunion (OR: 0.47, 95%CI: 0.30 to 0.73, P = 0.001; I² = 0%) in adult patients with femoral neck fractures. However, there was no statistically significant difference between the FNS and CCS in terms of failure of internal fixation (OR: 0.49, 95%CI: 0.23 to 1.06, P = 0.07, I² = 0%) and avascular necrosis of the femoral head (OR: 0.46, 95%CI: 0.20 to 1.10, P = 0.08, I² = 0%).

CONCLUSION

Compared with CCS, the FNS could decrease the chances of developing femoral neck shortness and delayed union or nonunion in adults with femoral neck fractures. Simultaneously, it could accelerate fracture healing and improve the HHS in these patients.

Biomechanical evaluation of different internal fixation methods based on finite element analysis for Pauwels type III femoral neck fracture

BACKGROUND AND OBJECTIVE

The best internal fixation method for the treatment of Pauwels type III femoral neck fractures (FNFs) remains to be demonstrated. Through finite element analysis, this study explored whether dynamic hip screw (DHS) combined with anti rotation screw or medial buttress plate can improve the stability of internal fixation, and the femoral neck system (FNS) with similar structure to DHS and the traditional cannulated screw (CSs) were added for comparison. To evaluate their respective biomechanical advantages and disadvantages in the treatment of Pauwels type III FNFs.

METHODS

Six groups of internal fixation models for the treatment of FNFs were established, including CSs, DHS, DHS combined with single anti-rotation screw (DHS + SS), and DHS combined with both anti-rotation screw (DHS + BS), DHS combined with medial buttress plate (DHS + MBP), new femoral neck internal fixation system (Femoral Neck System, FNS). Four finite element analysis models were established for each group, evaluation of femoral displacement and internal fixation stress during stair climbing and walking conditions, and the contact force of the hip joint was used in two cases, dynamic and static.

RESULTS

The fracture plane motion and peak stress of internal fixators were the lowest with DHS + BS and CSs fixation, and the two results are very close, The peak value of DHS combined with anti rotation screw or medial buttress plate is much lower than that of DHS, indicating that the fixation effect of the combined model is enhanced, and there is no significant difference between FNS and DHS + SS.

CONCLUSION

Both the anti rotation screw and medial buttress plate can effectively reduce the movement of fracture section and share the shear force of DHS, FNS has the similar fixation stability to DHS + SS, DHS + BS has the biomechanical advantages of significantly reducing the risk of internal fixation failure and femoral yield. Therefore, the use of DHS + BS may be a more favorable choice in the case of Pauwels type III FNFs with higher fixation requirements.

Evaluation of a Locking Autocompression Screw Model in Pauwels Type-3 Femoral Neck Fracture: In Vitro Analysis

Femoral neck fractures in young adults are uncommon, resulting from high-energy trauma. Despite their infrequency in this population, there is higher rate of complications, especially in the more vertical fracture line, classified by Pauwels as a type-3 femoral neck fracture. The implant type is of paramount importance for maintaining anatomical reduction, since it must resist the deforming forces that act on the fracture. We comparatively evaluated two constructions of the novel locking autocompression implant (X-PIN and X-PIN+P) using the finite element method and previously established methods for treating Pauwels type-3 femoral neck fractures. Six fixation models were developed for the study: a dynamic hip screw (DHS), a DHS with an anti-rotation screw (DHS+P), the inverted triangle multiple cannulated screws construction (ASNIS), the multiple cannulated screws in an L-configuration (L), and the two models of the novel locking autocompression screw (X-PIN and X-PIN+P). Under the same conditions with a load of 2100 N, the following parameters were evaluated using SIMLAB® software: the main maximum (Max P), main minimum (Min P), localized maximum P1 (Max P1), localized maximum P2 (Max P2), total displacement, localized displacement, rotation displacement, and von Mises stress. Compared to the DHS+P and ASNIS models, the X-PIN+P model presented, respectively, increases of 51.6% and 64.7% for Max P, 85% and 247% for Min P, and 18.9% and 166.7% for von Mises stress. Max P1 did not differ between the models, but Max P2 was 55% and 50% lower for X-PIN+P than ASNIS and L, respectively. All displacement values were lower for X-PIN+P than the other models. In this FEM testing, the X-PIN+P was superior to the other models, which was due to improvement in all parameters of stress distribution, displacement, and von Mises stress compared to models using a lateral plate (DHS and DHS+P) or not (ASNIS and L).

Biomechanical study on parallel cannulated compression screw combined with medial buttress plate fixation and F-type cannulated compression screw fixation in Pauwels III femoral neck fracture：A finite element analysis

OBJECTIVES

Pauwels III fracture is a kind of femoral neck fractures, in which the angle of the fracture line in the coronal plane and the upper edge of the acetabulum is more than 50°. Internal fixation for the treatment of femoral neck fractures is largely performed by cannulated compression screw (CCS), dynamic hip screw, or locking plate. This study aims to compare the biomechanical properties of parallel CCS combined with medial buttress plate fixation and F-type CCS fixation in the treatment of Pauwels III femoral neck fracture by finite element modeling and to determinate the most suitable procedure for such fractures.

METHODS

A 52-year-old male volunteer, 176 cm in height and 72 kg in weight, with no history of hip joint, was selected. X-ray and CT examination confirmed that the morphology and bone condition of the right hip of the volunteer were normal. A simulation model of Pauwels III femoral neck fracture was established from the collected CT data of the right proximal femur of the volunteer by the finite element method. Four internal fixations were developed to treat the finite element model: Three CCSs in an inverted triangular parallel configuration combined with medial buttress plate model served as Group A, 2 CCSs in a vertical parallel configuration combined with medial buttress plate model served as Group B, 2 CCSs in a horizontal parallel configuration combined with medial buttress model served as Group C, and the "F" shaped CCS model served as Group D. The distribution of stress, the peak stress, the distribution and maximum of displacement of internal fixations and fracture ends in different models were evaluated.

RESULTS

For Groups A, B, C, and D, the peak stresses on the internal fixation were 362.74, 586.84, 558.25, and 208.66 mPa, respectively, all of which occurred near the fractures and the stress distribution in Group D was the most uniform. The maximum displacements of internal fixations in Groups A, B, C, and D were 0.39, 0.45, 0.44, and 0.41 mm, respectively; the peak stresses on the fracture ends were 70.62, 98.48, 55.84, and 65.39 mPa, respectively, all of which were concentrated on the base of femoral neck and lateral cortex of the femoral shaft, and the stresses of Groups C and D were more evenly distributed than those of Groups A and B. The maximum displacements of fracture ends in Groups A, B, C, and D were 0.44, 0.52, 0.50, and 0.44 mm, respectively.

CONCLUSIONS

The biomechanical stability of F-type CCS fixation is similar to that of 3 CCSs in an inverted triangular parallel configuration combined with medial buttress plate, with a better dispersion of stress. F-type CCS fixation may be a well option for the treatment of femoral neck fracture of Pauwels III.

Finite element analysis of necessity of reduction and selection of internal fixation for valgus-impacted femoral neck fracture

This study compared the biomechanical characteristics of different treatment strategies based on finite element analysis. Posterior tilt and valgus angle were measured on X-ray from ten valgus-impacted femoral neck fractures, and 7 finite element models that were generated to compare the stress and displacement. The results showed that in the intact femur, von Mises stress was concentrated at the medial and inferior sides of the femoral neck. In valgus-impacted femoral neck fractures, von Mises stress was at the same locations but was 5.66 times higher than that in the intact femur. When 3 cannulated screws were used for internal fixation, anatomic reduction diminished the stress at the fracture end from 140.6 to 59.14 MPa, although displacement increased from 0.228 to 0.450 mm. When the fracture was fixed with a sliding hip screw (SHS) + cannulated screw, there was less stress at the fracture end and greater displacement with anatomic reduction than that without reduction (stress: 15.9 vs 37.9 MPa; displacement: 0.329 vs 0.168 mm). Therefore, the SHS + cannulated screw has superior biomechanical stability than 3 cannulated screws, and is recommended following anatomic reduction to treat valgus-compacted femoral neck fractures.

Biomechanical comparison of the femoral neck system versus InterTan nail and three cannulated screws for unstable Pauwels type III femoral neck fracture

BACKGROUND

There are a variety of internal fixation methods for unstable femoral neck fractures (FNFs), but the best method is still unclear. Femoral neck system (FNS) is a dynamic angular stabilization system with cross screws, and is a new internal fixation implant designed for minimally invasive fixation of FNFs. In this study, we conducted a biomechanical comparison of FNS, InterTan nail and three cannulated screws for the treatment of Pauwels III FNFs and investigate the biomechanical properties of FNS.

METHODS

A total of 18 left artificial femurs were selected and randomly divide into Group A (fixation with FNS), Group B (fixation with InterTan nail) and Group C (fixation with three cannulated screws), with 6 specimens in each group. After creating Pauwels type III FNF models, the specimens in each were tested with non-destructive quasi-static tests, including torsion, A-P bending and axial compression tests. The average slope of the linear load-deformation curve obtained from quasi-static tests defines the initial torsional stiffness, A-P bending stiffness, and axial compression stiffness. After cyclic loading test was applied, the overall deformation of models and local deformation of implant holes in each group were assessed. The overall deformation was estimated as the displacement recorded by the software of the mechanical testing apparatus. Local deformation was defined as interfragmental displacement. Data were analyzed by one-way analysis of variance (ANOVA) followed by Bonferroni post hoc test using the SPSS software (version 24.0, IBM, New York, NY, USA). Correlation analysis was performed using Pearson's correlation analysis.

RESULTS

Group B exhibited significantly higher axial stiffness and A-P bending stiffness than the other two groups (P < 0.01), while Group A had significantly higher axial stiffness and A-P bending stiffness than Group C (P < 0.01). Groups A and B exhibited significantly higher torsional stiffness than Group C (P < 0.01), no statistical significance was observed between Groups A and B (P > 0.05). Group B exhibited significantly lower overall and local deformations than the other two groups (P < 0.01), while Group A had significantly lower overall and local deformations than Group C (P < 0.01). Correlation analysis revealed positive correlation between axial stiffness and A-P bending stiffness (r = 0.925, P < 0.01), torsional stiffness (r = 0.727, P < 0.01), between torsional stiffness and A-P bending stiffness; negative correlation between overall, local deformations and axial stiffness (r = - 0.889, - 0.901, respectively, both P < 0.01), and positive correlation between the two deformations (r = - 0.978, P < 0.01).

CONCLUSION

For fixation of unstable FNFs, InterTan nail showed the highest axial stiffness and A-P bending stiffness, followed by FNS, and then three cannulated screws. Torsional stiffness of FNS was comparable to that of the InterTan nail. FNS, as a novel minimally invasive implant, can create good mechanical environment for the healing of unstable FNFs. Clinical studies are needed to confirm the potential advantages of FNS observed in this biomechanical study.

Medial Buttress Plate and Allograft Bone-Assisted Cannulated Screw Fixation for Unstable Femoral Neck Fracture with Posteromedial Comminution: A Retrospective Controlled Study

Objective

To investigate the outcomes of open reduction and internal fixation combined with medial buttress plate (MBP) and allograft bone‐assisted cannulated screw (CS) fixation for patients with unstable femoral neck fracture with comminuted posteromedial cortex.

Methods

In a retrospective study of patients operated on for unstable femoral neck fractures with comminuted posteromedial cortex from March 2016 to August 2020, the clinical and radiographic outcomes of 48 patients treated with CS + MBP were compared with the outcomes of 54 patients treated with CS only. All patients in the CS + MBP group were fixed by three CS and MBP (one‐third tubular plates or reconstructive plates) with bone allografts. The surgery‐related outcomes and complications were evaluated, including operative time, blood loss, union time, femoral head necrosis, femoral neck shortening, and other complications after the operation. The Harris score was evaluated at 12 months after the operation.

Results

All patients were followed up for 12–40 months. The average age of patients in the CS‐only group (54 cases, 22 females) and CS + MBP group (48 cases, 20 females) was 48.46 ± 7.26 and 48.73 ± 6.38 years, respectively. More intraoperative blood loss was observed in the CS + MBP group than that of patients in CS‐only group (153.45 ± 64.27 vs 21.86 ± 18.19 ml, t = 4.058, P = 0.015). The average operative time for patients in the CS + MBP group (75.35 ± 27.67 min) was almost double than that of patients in the CS‐only group (36.87 ± 15.39 min) (t = 2.455, P < 0.001). The Garden alignment index of patients treated by CS + MBP from type I to type IV was 79%, 19%, 2%, and 0%, respectively. On the contrary, they were 31%, 43%, 24% and 2% for those in the CS‐only group, respectively. The average healing times for the CS‐only and CS + MBP groups were 4.34 ± 1.46 and 3.65 ± 1.85 months (t = 1.650, P = 0.102), respectively. Femoral neck shortening was better in the CS + MBP group (1.40 ± 1.73 mm, 9/19) than that in the CS‐only group (4.33 ± 3.32 mm, 24/44). Significantly higher hip function was found in the CS + MBP group (85.60 ± 4.36 vs 82.47 ± 6.33, t = 1.899, P = 0.06). There was no statistical difference between femoral head necrosis (4% vs 11%, χ² = 1.695, P = 0.193) and nonunion (6% vs 9%, χ² = 0.318, P = 0.719).

Conclusion

For unstable femoral neck fractures with comminuted posteromedial cortex, additional MBP combined with bone allografts showed better reduction quality and neck length control than CS fixation only, with longer operative time and more blood loss.

The effect of anteromedial support plate with three cannulated screws in the treatment of Pauwels type III femoral neck fracture in young adults

PURPOSE

This study is aimed to evaluate the clinical effects of anteromedial support plate combined with three cannulated screws on Pauwels type III femoral neck fractures in young adults.

METHODS

We conducted a retrospective study of 27 patients with Pauwels type III femoral neck fracture treated by anteromedial support plate combined with three cannulated screws. The results of fracture healing and complications for all patients were assessed by postoperative imaging examination. The Harris hip score was used to evaluate the functional outcome of the hip at the last follow-up.

RESULTS

The fracture union was achieved in 25 patients (92.6%). However, two patients required reoperation (two for nonunion). Early implant failure occurred in one patient, neck shortening in one patient and coxa vara in one patient. The excellent or good outcome of the Harris hip score was 96% for the 25 patients with satisfactory fracture union.

CONCLUSION

Our preliminary results indicate that anteromedial support plate combined with three cannulated screws is a good alternative in the treatment of Pauwels type III femoral neck fractures in young adults with high union rate and low incidence of complications including nonunion and avascular necrosis of the femoral head.

Influence of therapeutic grip exercises induced loading rates in distal radius fracture healing with volar locking plate fixation

BACKGROUND AND OBJECTIVE

Therapeutic exercises could potentially enhance the healing of distal radius fractures (DRFs) treated with volar locking plate (VLP). However, the healing outcomes are highly dependant on the patient-specific fracture geometries (e.g., gap size) and the loading conditions at the fracture site (e.g., loading frequency) resulted from different types of therapeutic exercises. The purpose of this study is to investigate the effects of different loading frequencies induced by therapeutic exercises on the biomechanical microenvironment of the fracture site and the transport of cells and growth factors within the fracture callus, ultimately the healing outcomes. This is achieved through numerical modelling and mechanical testing.

METHODS

Five radius sawbones specimens (Pacific Research Laboratories, Vashon, USA) fixed with VLP (VRP2.0+, Austofix) were mechanically tested using dynamic test instrument (INSTRON E3000, Norwood, MA). The loading protocol used in mechanical testing involved a series of cyclic axial compression tests representing hand and finger therapeutic exercises. The relationship between the dynamic loading rate (i.e., loading frequency) and dynamic stiffness of the construct was established and used as inputs to a developed numerical model for studying the dynamic loading induced cells and growth factors in fracture site and biomechanical stimuli required for healing.

RESULTS

There is a strong positive linear relationship between the loading rate and axial stiffness of the construct fixed with VLP. The loading rates induced by the moderate frequencies (i.e., 1-2 Hz) could promote endochondral ossification, whereas relatively high loading frequencies (i.e., over 3 Hz) may hinder the healing outcomes or lead to non-union. In addition, a dynamic loading frequency of 2 Hz in combination of a fracture gap size of 3 mm could produce a better healing outcome by enhancing the transport of cells and growth factors at the fracture site in comparison to free diffusion (i.e. without loading), and thereby produces a biomechanical microenvironment which is favourable for healing.

CONCLUSION

The experimentally validated numerical model presented in this study could potentially contribute to the design of effective patient-specific therapeutic exercises for better healing outcomes. Importantly, the model results demonstrate that therapeutic grip exercises induced dynamic loading could produce a better biomechanical microenvironment for healing without compromising the mechanical stability of the overall volar locking plate fixation construct.

A Comparative Analysis of Femoral Neck System and Three Cannulated Screws Fixation in the Treatment of Femoral Neck Fractures: A Six-Month Follow-Up

Objective

To investigate the efficacies of Femoral Neck System (FNS) and the three cannulated screws fixation (3CS) as therapeutic options for femoral neck fractures.

Method

This was a retrospective study involving 69 patients (26 males and 43 females; mean age of 54.9 years (range, 28–66 years)) subjected to either FNS or 3CS for femoral neck fracture therapy. These patients were treated in our hospital from October 2019 to May 2020. Patient follow up was done at 1, 2, 3 and 6 months. During the short‐term (6 months) follow‐up period, surgical procedures for the two groups and incidences of complications were analyzed. Perioperative parameters were recorded and analyzed. Postoperative hip joint functions were measured and compared using the Harris score. The assessed perioperative parameters included surgical time, hemoglobin loss, fluoroscopy duration, hospitalization length and hospitalization cost. The main complications at last follow‐up (6 months) included varus tilting, femoral neck shortness, and implant removal.

Results

Differences in the number of patients, age, Garden type of fracture and time from injury to surgery between the two groups were not significant (P > 0.05). With regards to perioperative parameters, compared to 3CS, FNS treatment performed better in surgical time (60.00 ± 12.44 vs 76.81 ± 13.10 min, P = 0.000), blood loss (13.67 ± 8.02 vs 16.58 ± 4.16 g/L, P = 0.059) and fluoroscopy time (39.73 ± 9.57 vs 58.14 ± 9.15 s, P = 0.000). Differences in hospitalization length and cost between the groups were not significant (P > 0.05). During the whole follow‐up period, all patients did not exhibit dysfunction, pulmonary embolism or even death as a result of long‐term immobilization of affected limbs. Surgical incisions for all patients healed well without infections. During the 6‐month follow‐up period, the FNS group exhibited a higher Harris score (84.61 ± 3.42 vs 78.67 ± 3.72, p = 0.000). In addition, treatment‐associated complications (FNS vs 3CS) included femoral neck varus tilt (3.03% vs 11.11%), femoral neck shortness (6.06% vs 13.89%), and implant removal (0% vs. 13.89%). Implant removal rate for the FNS group was significantly less than that of the 3CS group (P = 0.026). Differences in incidences of femoral neck varus tilt (P = 0.196) and femoral neck shortness (P = 0.282) between the two groups were not significant. However, the difference in number was significant (FNS group was less).

Conclusion

FNS treatment is associated with a smaller surgical trauma, stronger stability, and reductions in post‐operative complication incidences, therefore, it is a potential therapeutic option for femoral neck fractures.

Mechanical effects of surgical variations in the femoral neck system on Pauwels type III femoral neck fracture : a finite element analysis

AIMS

In this study, we aimed to explore surgical variations in the Femoral Neck System (FNS) used for stable fixation of Pauwels type III femoral neck fractures.

METHODS

Finite element models were established with surgical variations in the distance between the implant tip and subchondral bone, the gap between the plate and lateral femoral cortex, and inferior implant positioning. The models were subjected to physiological load.

RESULTS

Under a load of single-leg stance, Pauwels type III femoral neck fractures fixed with 10 mm shorter bolts revealed a 7% increase of the interfragmentary gap. The interfragmentary sliding, compressive, and shear stress remained similar to models with bolt tips positioned close to the subchondral bone. Inferior positioning of FNS provided a similar interfragmentary distance, but with 6% increase of the interfragmentary sliding distance compared to central positioning of bolts. Inferior positioning resulted in a one-third increase in interfragmentary compressive and shear stress. A 5 mm gap placed between the diaphysis and plate provided stability comparable to standard fixation, with a 7% decrease of interfragmentary gap and sliding distance, but similar compressive and shear stress.

CONCLUSION

Finite element analysis with FNS on Pauwels type III femoral neck fractures revealed that placement of the bolt tip close to subchondral bone provides increased stability. Inferior positioning of FNS bolt increased interfragmentary sliding distance, compressive, and shear stress. The comparable stability of the fixation model with the standard model suggests that a 5 mm gap placed between the plate and diaphysis could viably adjust the depth of the bolt. Cite this article: Bone Joint Res 2022;11(2):102-111.

Comparison of the clinical efficacy of a femoral neck system versus cannulated screws in the treatment of femoral neck fracture in young adults

BACKGROUND

To compare the clinical efficacy of a femoral neck system (FNS) and cannulated screws (CS) in the treatment of femoral neck fracture in young adults.

METHODS

Data from 69 young adults, who were admitted for femoral neck fracture between March 2018 and June 2020, were retrospectively analyzed. Patients were divided into two groups according to surgical method: FNS and CS. The number of intraoperative fluoroscopies, operative duration, length of hospital stay, fracture healing time, Harris score of hip function, excellent and good rate of hip function, and postoperative complications (infection, cut out the internal fixation, nail withdrawal, and femoral neck shortening) were compared between the two groups. Hip joint function was evaluated using the Harris Hip Scoring system.

RESULTS

All 69 patients had satisfactory reduction and were followed up for 12-24 months, with a mean follow-up of 16.91 ± 3.01 months. Mean time to fracture healing was13.82 ± 1.59 and 14.03 ± 1.78 weeks in the FNS and CS groups, respectively. There was a statistical difference in the number of intraoperative fluoroscopies between the 2 groups (P = 0.000). There were no significant differences, in operation duration, hospital length of stay, fracture healing time, complications, Harris Hip Score for hip function and excellent and good rate between the two groups (P > 0.05). The incidence of complications was 6.1%(2/33) in the FNS group lower than 25%(9/36) in the CS group, a difference that was statistically significant (P = 0.032). At the last follow-up, the Harris Hip Score of the hip joint in the FNS group was 90.42 ± 4.82and 88.44 ± 5.91 in the CS group.

CONCLUSIONS

Both treatment methods resulted in higher rates of fracture healing and excellent hip function. Compared with CS, the FNS reduced the number of intraoperative fluoroscopies, radiation exposure to medical staff and patients, and short-term complications including femoral neck shortening and bone nonunion.

Finite Element Analysis of a Novel Anatomical Locking Guide Plate for Anterior Column and Posterior Hemi-Transverse Acetabular Fractures

Purpose

The increasing worldwide prevalence of anterior column-posterior hemi-transverse fracture (ACPHTF) brings formidable challenges to orthopaedic surgeons. Our newly-designed locking plate had previously demonstrated promising effects in ACPHTF, but evidence of their direct comparison with conventional internal fixations remains lacking. In this study, we aimed to compare our novel plate with the traditional devices via finite element analysis.

Methods

The ACPHTF model was created based on a 48-year-old volunteer’s CT data, and then fixed in three different internal fixations: an anterior column locking plate with posterior column screws, double column locking plates, and our novel anatomical locking plate. These models were next loaded with a downward vertical force of 200 N, 400 N and 600 N, and the stress peaks and displacements of three different sites were recorded and analyzed.

Results

We first tested the rigidity and found that our newly-designed locking plate as well as its matched screws had a greater stiffness especially when they were under a higher loading force of 600 N. Then we evaluated the displacements of fracture ends after applying these fixations. Both our novel plate and DLP showed significantly smaller displacement than LPPCS at the anterior column fracture line and the pubic branch fracture line, while our novel plate was not obviously inferior to DLP in terms of the displacement.

Conclusion

This novel plate demonstrates a distinct superiority in the stiffness over LPPCS and DLP and comparable displacements to DLP in ACPHTF, which suggests this novel anatomical locking guide plate should be taken into consideration in ACPHTF.

Modified F configuration in the treatment of Pauwels type III femoral neck fracture: a finite element analysis

Background

The optimal treatment of Pauwels type III femoral neck fracture (FNF) in young patients remains a worldwide challenge in orthopedic surgery.

Methods

Finite element models of four internal fixations were developed to treat Pauwels type III FNF: a: the traditional inverted triangular parallel cannulated screw (PCS) model, b: the F-technique cannulated screw model, c: the modified F-technique cannulated screw model using a fully threaded screw instead of a partially threaded distally, d: the dynamic hip screw coupled with derotational screw (DHS + DS) model. Under the same conditions, finite element analyses were carried out to compare the displacement and von Mises stress distribution of four internal fixations and femurs, the maximum crack distances of the fracture surfaces, Z axis displacements of four models as well as the stress distribution in the subtrochanteric region.

Results

The modified F-technique configuration resulted in a more stable fixation as compared to the other three configurations, with respect to the maximum displacement and stress peaks of femur and internal fixations, the maximum crack distances of the fracture surfaces, Z axis displacements of four configurations as well as the stress distribution in the subtrochanteric region.

Conclusions

Our results suggested that modified F-technique configuration show a better performance in resisting shearing and rotational forces in treating Pauwels type III FNF compared to those using traditional inverted triangular PCS, the F-technique configuration or DHS + DS, providing a new choice for the treatment of FNFs.

How to choose the suitable FNS specification in young patients with femoral neck fracture: A finite element analysis

BACKGROUND

Consensus regarding the optimal approach for the treatment of femoral neck fractures remains lacking. A new internal fixation femoral neck system (FNS) was developed and used in clinical practice. We aimed to investigate the biomechanical outcomes of different types of FNS in the treatment of unstable femoral neck fractures.

METHOD

In this study, we constructed three different types of unstable femoral neck fractures of Pauwels classification with angles of 50°, 60°, and 70°. We set up four test groups, namely, the one-hole plated FNS group, two-hole plated FNS group, inverted cannulated screw group and triangle cannulated screw group. Under 2100 N axial loads, displacements and the von Mises stress of the femur and internal fixation components were measured for each fracture group.

RESULTS

When the Pauwels angle was 50°or 60°, the one-hole locking plated FNS was as superior as the two-hole plated FNS in terms of femur and internal fixation displacement, and the inverted cannulated screw had slightly better stability than the triangular cannulated screw. However, when the angle increases to 70°, the two-hole locking plate has the minimum displacement, followed by the triangular cannulated screw and inverted cannulated screw, which is the worst displacement for the single-hole locking plate. Regardless of the angle, the two sets of FNS have higher internal fixation stress than the two sets of cannulated screws, which is approximately 1.6-3.0 times that of the cannulated screw group.

CONCLUSION

From the perspective of biomechanics, we suggest that when the angle of the fracture line is less than 60°, both single-hole locking plated or double-hole locking plated FNS can be used to treat unstable femoral neck fractures. However, when the angle of the fracture line is greater than 70°, we recommend using a double-hole locking plated FNS. This result needs further verification in further clinical studies.

Analysis on risk factors for neck shortening after internal fixation for Pauwels II femoral neck fracture in young patients

Background

Femoral neck shortening can occur in young patients receiving internal fixation for Pauwels type II femoral neck fracture. The risk factors for neck shortening, which can affect hip function, are not clear. This study aimed to retrospectively identify risk factors for neck shortening after internal fixation with parallel partially threaded cannulated cancellous screws (FPTCS) for Pauwels type II femoral neck fracture in relatively young patients.

Methods

Clinical data from 122 cases with Pauwels type II femoral neck fracture from February 2014 to February 2019 were reviewed and analyzed, and causes of neck shortening were statistically analyzed. And the Chi-squared test or Fisher’s exact test was used to compare indicators. Multivariate analysis was conducted with non-conditional logistic regression analysis.

Results

Statistically significant differences were found in age, sex, BMD, BMI, fracture type, posterior medial cortex comminution, and reduction quality between patients with femoral neck shortening and those without femoral neck shortening. Logistic regression analysis showed that fracture type, posterior medial cortex comminution, and reduction quality were the main risk factors for neck shortening.

Conclusion

Fracture type, posterior medial cortex comminution, and reduction quality can be used as important reference indexes to predict the possibility of neck shortening after internal fixation with FPTCS for Pauwels type II femoral neck fracture in young patients. BMD and BMI may be also risk factors.

A comparative mechanical study of two types of femur bone implant using the finite element method

The femoral bone fracture is one of the most common fractures that orthopedic surgeons deal with. These fractures are associated with a significant percentage of death due to non-orthopedic complications. For this reason, it is necessary that the surgeon be well-aware of the condition of the patient and also of the biomechanical conditions of the bone and implant before surgery, in order to use the best surgical technique. Nowadays, the use of implants is a popular technique among the available methods for the treatment of femoral fractures. In the present study, two patients with different ages, three types of femoral bone fractures, that is, oblique, reverse oblique, and neck fracture, and two types of implants, namely, the dynamic hip screw (DHS) and the Gamma nail have been investigated. The behavior of the implants has been investigated at the two stages of treatment, that is, before and after bone union. The analysis of implants was based on the amount of stress and displacement induced in different parts of the bone and the implant. From the viewpoint of the stresses induced in the bone, all models are quite similar and in terms of the implant stresses, the Gamma nail is more reliable than the DHS. Additionally, the relative displacement of the fractured bone segments at the fracture planes was calculated. According to the obtained results, it can be concluded that the relative displacement of the fracture planes with the use of Gamma nail is somewhat less than the DHS, but this difference is not significant.

Finite Element Analysis of Femoral Neck Fracture Treated with Bidirectional Compression-Limited Sliding Screw

Background

The rate of femoral neck shortening after internal fixation for femoral neck fracture is high and this complication reduces the function of the affected lower limb. The aim of this study was to design a bidirectional compression-limited sliding screw (BCLSC) that can achieve a full balance between retaining the sliding pressure of the ends of and maintaining the length of the femoral neck.

Material/Methods

We constructed a 3-dimensional model of a Pauwels III femoral neck fracture and models of 3 internal fixation methods (3 cannulated screws [3CS], dynamic hip screw [DHS]+CS, and BCLSC) by finite element analysis (FEA).The finite element model simulated the loading of the human body when standing on 1 leg. Displacement and stress distribution of the models were calculated based on an axial stress of 600 N.

Results

The peak von Mises stress (VMS) values of fracture ends in the 3CS, DHS+CS and BCLSC groups were 94.687 MPa, 26.375 MPa and 45.698 MPa; the peak VMS values of internal fixed stress were 451.53 MPa, 174.45 MPa, and 337.34 MPa; the peak VMS values of the lateral femoral wall were 70.021 MPa, 53.033 MPa, and 20.009 MPa; maximum displacements of the femoral head were 1.4482 mm, 1.3813 mm, and 1.3889 mm; and the internal fixed displacement peaks were 4.1134 mm, 3.91 mm, and 4.1004 mm, respectively.

Conclusions

The FEA showed that compared with the CS, the new BCLSC showed better performance in resisting shearing force for Pauwels III femoral neck fracture, with better mechanical properties. These data provide a basis for further experiments and clinical application.

The elastoplastic numerical model and verification by macroindentation experiment of femoral head

For internal fixation of proximal femoral fractures, a screw is commonly placed into the femoral head; therefore, mechanical matching of the femoral head and screw is important. This article proposes an elastoplastic numerical model of the femoral head that takes nonlinear deformation and cancellous bone heterogeneity into account. Force-depth curves from finite element analysis based on the model were compared with those from macroindentation experiments. The maximum difference between the indentation depth shown by the finite element model and that found with macroindentation testing was 5.9%, which demonstrates that the model is valid.

Quasi-static analysis of hip cement spacers

The use of temporary hip prosthesis made of orthopedic cement (spacer) in conjunction with antibiotics became a widespread method used for treating prosthetic infections despite the fact that this method makes bone cement (PMMA) more fragile. The necessity to incorporate reinforcement is therefore crucial to strengthen the bone cement. In this study, a validated Finite Element Modelling (FEM) was used to analyze the behavior of spacers. This FEM model uses a non-linear dynamic explicit integration to simulate the mechanical behavior of the spacer under quasi-static loading. In addition to this FEM, Extended Finite Element Method (XFEM) was also used to investigate the fracture behavior of the spacers reinforced with titanium, ceramic and stainless-steel spacer stems. The effect of the material on the performance of the reinforced spacers was also analyzed. The results showed that numerical modelling based on explicit finite element using ABAQUS/Explicit is an effective method to predict the different spacers' mechanical behavior. The simulated crack initiation and propagation were in a good agreement with experimental observations. The FEM models developed in this study can help mechanical designers and engineers to improve the prostheses' quality and durability.

New fixation method for Pauwels type III femoral neck fracture: a finite element analysis of sliding hip screw, L-shaped, and L-shaped with medial plate

OBJECTIVE

In this study, we aimed to evaluate the biomechanical behavior of three fixations for Pauwels type III fractures (sliding hip screw (SHS), L-shaped, and L-shaped with medial plate), by finite element analysis (FEM).

METHODS

Three internal fixators were developed to treat Pauwels type III fracture by finite elements: SHS; L-shaped; and L-shaped with medial plate. Under the same conditions, localized and total vertical fracture displacement, maximum and minimum principal and von Mises stresses were evaluated.

RESULTS

The localized and total vertical displacement evaluated for the SHS, L-shaped, and L-shaped with medial plate were 0.15 mm, 0.17 mm, and 0.07 mm (localized), and 4.52 mm, 6.97 mm, and 6.83 mm (total), respectively. The maximum values obtained in the upper region of the femoral neck for the internal fixations were 1.43 MPa, 1.29 MPa, and 1.24 MPa, and the minimum values obtained in the lower region of the femoral neck were  - 0.73 MPa,  - 1.09 MPa, and  - 1.03 MPa, respectively. The maximum Von Mises peak stress values were 6.35 MPa, 10.7 MPa, and 16.2 MPa for the fixation models using the SHS, L-shaped, and L-shaped with medial plate, respectively.

CONCLUSION

The present FEM analysis showed that SHS yields better results in terms of total vertical displacements, maximum distribution, and Von Mises peak stresses reduction. On the other hand, the L-shaped construction plus a medial plate decreases localized vertical displacements and maximum principal distribution when compared to the SHS and L-shaped constructions. These results demonstrate that both constructions, SHS and L-shaped plus a medial plate, are biomechanically efficient for the fixation of Pauwels type III femoral neck fractures.

Lag screw with DHS (LSD) for vertical angle femoral neck fractures in young adults

Vertical Pauwels Type III fractures of the neck of femur in young patients are difficult fractures to treat. These are usually as a result of high energy trauma which are associated with a significant degree of fracture comminution in the neck of femur. This makes the fracture reduction and fixation difficult. Many fixation methods and implants have been described for use in these fractures but are not without reported complications such as non-union and varus collapse. In this article, we highlight the incidence of fracture comminution in both the anterior and posterior cortices of the femoral neck, better visualised with axial computed tomography scanning and describe a simple technique utilizing lag screws and a DHS implant to adequately address these fractures.

Biomechanical analysis for five fixation techniques of Pauwels-III fracture by finite element modeling

BACKGROUND AND OBJECTIVES

There are many fixation methods for Pauwels- III fracture, the most common implants are Locking Plate (LP), Dynamic Hip Screw (DHS), Multiple Lag Screw (MLS), and mixed fixture (DHS+MLS) implants, the common procedure is HemiArthroplasty (HA). However, how these fixtures biomechanically function is not clear. The aims of this study are to compare the mechanical behaviors of these five implants by finite element modeling and determinate the most suitable procedure for individuals with Pauwels- III fractures.

METHODS

We gathered 20 sets of femur images from CT scans in the *.dicom format first, and then processed them by using reverse engineering software programs, such as Mimics, Geomagic Studio, UG-8, Pro-Engineer and HyperMesh. Finally, we assembled and analyzed the five types of fixture models, the LP, DHS, MLS, DHS+LS and HA models, by AnSys.

RESULTS

These numerical models of Pauwels III fractures, including fixators and a simulative HA, were validated by a previous study and a cadaver test. Our analytical findings include the following: the displacements of all fixtures were between 0.3801 and 1.0834 mm, and the differences were not statistically significantly different; the resulting average peaks in stress were e(Ha) = 43.859 ≤ d(LP) = 60.435 ≤ b(MLS) = 68.678 < c(LS+DHS) = 98.478 < a(DHS) = 248.595 in Mpa, indicating that the stress of DHS and DHS+LS are greater than those of LP, HA and MLS, while the last 3 models were not significantly different.

CONCLUSIONS

To optimize the treatment for Pauwels III factures clinically, HA and LP should be proposed.

Analysis of mechanical variables in Hoffa fracture - A comparison of four methods by finite elements

BACKGROUND

Correct management of Hoffa fractures is a challenge in the clinical context. Open reduction along with internal fixation should be the therapy of choice. Mechanical trials with the main internal fixation systems conducted by individualized finite element (FEM) models, to date, have been neglected. The aim of this study was to biomechanically analyze four fixation methods for the treatment of Type II Hoffa fracture (OTA Classification: 33B3.2∗ lateral) using FEM.

METHODS

Four internal fixators were developed to treat Type II Hoffa fracture using finite elements: 4.5 mm cortical screws and 7 mm cannulated screw in anterior-to-posterior and posterior-to-anterior directions (4.5AP, 4.5 PA, 7AP and 7 PA). Under the same conditions, fractural deviation in the vertical, maximum and minimum principal and Von Mises directions in the syntheses used were evaluated.

RESULTS

The vertical displacements evaluated were 0.7 mm, 0.5 mm, 0.8 mm and 0.3 mm; the values of maximum were 6.14 Mpa, 6.15 hPa, 6.0 Mpa and 6.2 Mpa, the values obtained from minimum data were 6.26 Mpa, -6.45 Mpa, -7.3 MPa and -6.8 Mpa and the maximum values of Von Mises peak stress were 185.0 Mpa, 194.1 Mpa, 143.6 Mpa and 741.4 Mpa, for the fixation models 4.5AP, 4.5 PA, 7AP and 7 PA, respectively.

CONCLUSION

The 7 mm-cannulated screw fixation system yielded the best mechanical results evaluated by FEM in the treatment of Type II Hoffa fracture, causing a decrease in vertical displacement when used in retrograde and in Von Mises peak stress in anterograde.

Fixation of distal tibia fracture through plating, nailing, and nailing with Poller screws: A comparative biomechanical-based experimental and numerical investigation

The goal of this study was to investigate two commonly used methods of fixation of distal metaphyseal tibia fractures, plating and nailing as well as the less frequently employed nailing with Poller screws, from a biomechanical perspective. Despite numerous studies, the best method to repair fractures of tibia the remains up for of debate. This study includes an in vitro experimental phase on human cadaveric tibias followed by a finite element analysis. In the experimental phase, under partial weight-bearing axial loading, the axial stiffness of the bone-implant construct and interfragmentary movements for each of the fixation methods, bone-plate, bone-nail, and bone-nail-Poller screw, were measured and compared with each other. Shear interfragmentary movement and stress distribution in the bone-implant construct for the three mentioned fixation methods were also determined from FE models and compared with each other. Results of in vitro experiments, i.e., the exertion of axial loading on the tibia-plate, tibia-nail, and tibia-nail-Poller screw, showed that utilization of tibia-nail and tibia-nail-Poller screw led to a stiffer bone-implant construct, and consequently, lower interfragmentary movement, compared to the tibia-plate construct ( p values for tibia-nail and tibia-nail-Poller screw, and for both axial stiffness and interfragmentary movement, compared to those of tibia-plate construct, were less than 0.05). Numerical analyses showed that nailing produced less undesirable shear interfragmentary movement, compared to the plating, and application of a Poller screw decreased the shear movements, compared to tibia-nail. Furthermore, using the finite element analysis, maximum von Mises stress of adding a screw in tibia-nail, tibia-plate, and tibia-nail-Poller screw, was found to be: 51.5, 78.6, and 60.5 MPa, respectively. The results of this study suggested that from a biomechanical standpoint, nailing both with and without a Poller screw is superior to plating for the treatment of distal tibia fractures.

Biomechanical evaluation of locked plating fixation for unstable femoral neck fractures

Aims

Evaluate if treating an unstable femoral neck fracture with a locking plate and spring-loaded telescoping screw system would improve construct stability compared to gold standard treatment methods.

Methods

A 31B2 Pauwels' type III osteotomy with additional posterior wedge was cut into 30 fresh-frozen femur cadavers implanted with either: three cannulated screws in an inverted triangle configuration (CS), a sliding hip screw and anti-rotation screw (SHS), or a locking plate system with spring-loaded telescoping screws (LP). Dynamic cyclic compressive testing representative of walking with increasing weight-bearing was applied until failure was observed. Loss of fracture reduction was recorded using a high-resolution optical motion tracking system.

Results

LP constructs demonstrated the highest mean values for initial stiffness and failure load. LP and SHS constructs survived on mean over 50% more cycles and to loads 450 N higher than CS. During the early stages of cyclic loading, mean varus collapse of the femoral head was 0.5° (SD 0.8°) for LP, 0.7° (SD 0.7°) for SHS, and 1.9° (SD 2.3°) for CS (p = 0.071). At 30,000 cycles (1,050 N) mean femoral neck shortening was 1.8 mm (SD 1.9) for LP, 2.0 mm (SD 0.9) for SHS, and 3.2 mm (SD 2.5) for CS (p = 0.262). Mean leg shortening at construct failure was 4.9 mm (SD 2.7) for LP, 8.9 mm (SD 3.2) for SHS, and 7.0 mm (SD 4.3) for CS (p = 0.046).

Conclusion

Use of the LP system provided similar (hip screw) or better (cannulated screws) biomechanical performance as the current gold standard methods suggesting that the LP system could be a promising alternative for the treatment of unstable fractures of the femoral neck.Cite this article: Bone Joint Res 2020;9(6):314-321.

Risk of bony violation with standard triple screw configurations for fixation of femoral neck fractures: A preliminary computed tomography based analysis

PURPOSE

The reduction and fixation of femoral neck fractures is mainly an indirect one with intraoperative fluoroscopy being trusted for the safe containment of screws within the bony limits of the femoral neck. Radiologically undetected bony perforations may have an impact on the fracture stability and radiological outcomes that have not been studied previously. The purpose of this computed tomography (CT) based study is to analyze the safety of containment of triple screw configurations using standard 6.5 mm diameter screws for fixation of femoral neck fractures in the Indian population using a software-based analysis.

METHODS

Data from consecutive CT scans with intact proximal femur performed over a six month period were retrospectively analyzed using iPlan® BrainLab AG, Feldkirchen, Germany. The safe containment of virtual screw trajectories placed in inverted triangular and non-inverted triangular configurations for a 6.5 mm diameter screw was analyzed in intact femoral necks.

RESULTS

A total of 72 cases were considered for the final assessment. For 6.5 mm screws, the proportion for safe containment (without bony violation) of triple screw inverted triangular configuration was 75% with additional safety corridor to 1 mm around the screw trajectories and 31.94% for non-inverted triangular configuration. All male cases and 28% of female cases allowed safe placement of three 6.5 mm screw trajectories in an inverted triangular pattern with a safety margin of 1 mm around the screw. Replacement of one of the two superior 6.5 mm diameter screw trajectories with a 4.5 mm diameter trajectory resulted in 100% safe containment in female cases.

CONCLUSION

Inverted triangular configuration is a relatively safer configuration compared to the non-inverted triangular configuration. Standard triple 6.5 mm screws for fixation of femoral neck fractures carry a risk of bony violation, especially in females. A preoperative radiographic assessment to screen the cases with narrow vertical and anteroposterior extents of the femoral neck can help in reducing the risk of fluoroscopically undetected violation of the bony margins. Replacement of one of the two superior screws with a 4.5 mm diameter screw can be helpful in such cases.

Suboptimal outcomes after internal fixation for displaced intracapsular femoral neck fractures in 50- to 60-year-old patients

PURPOSE

The aim of this study was to evaluate outcomes of internal fixation for displaced femoral neck fracture (FNF) between 50 and 60 years old. The patient and surgical factors for the failure were identified.

METHODS

We retrospectively reviewed the records of 102 displaced FNF patients between 50 and 60 years old (mean age 54.9 years) who had undergone internal fixation between 2005 and 2016. The minimum follow-up was 12 months. Primary end points included loss of reduction, non-union, and osteonecrosis of the femoral head (ONFH). Preoperative Pauwel's angle, fixation timing and methods, reduction quality, removal of implant and medical comorbidities were analysed.

RESULTS

The overall failure rate was 44.1%. In multivariate logistic regression analysis, poor reduction quality (adjusted odds ratio [aOR] 4.38; 95% confidence interval [CI], 1.54-12.46) and internal fixation delayed more than 6 hours (aOR 3.24; 95% CI, 1.08-9.69) were risk factors for all causes of failure. In a stratified analysis, poor reduction quality (aOR 3.81; 95% CI, 1.11-13.04) and a history of alcohol dependency (aOR 4.91; 95% CI, 1.09-22.13) were risk factors for loss of reduction. Internal fixation delayed >6 hours (aOR 3.67; 95% CI, 1.05-12.77) and removal of implant (aOR 3.32; 95% CI, 1.02-10.77) were risk factors for ONFH.

CONCLUSIONS

The outcome of internal fixation of displaced FNF in patients between 50 and 60 years old is suboptimal. The patient selection is important. Non-alcohol dependency lowered early failure. Implant retention reduced ONFH. Surgery within 6 hours and good quality of reduction yield better results.

Biomechanical study of different internal fixations in Pauwels type III femoral neck fracture - A finite elements analysis

OBJECTIVE

To evaluate biomechanical behavior of different internal fixation methods for the treatment of Pauwels Type III femoral neck fractures.

METHODS

Three internal fixators were developed to treat Pauwels Type III femoral neck fracture using finite elements: dynamic hip screw (DHS); DHS combined with anti-rotation screw; three cannulated screws in an inverted triangular configuration (ASNIS). Under the same conditions, vertical fracture displacement, and maximum and minimum principal, and Von Mises stresses were evaluated.

RESULTS

The vertical displacements evaluated were: 5.43 mm, 5.33 mm and 6.22 mm, rotational displacements values were 1.1 mm, 0.4 mm and 1.3 mm; maximum principle stress values obtained for the upper region of the femoral neck were 3.26 hPa, 2.77 hPa, and 4.5 hPa, minimum principal stress values obtained for the inferior region of the femoral neck were -1.97 hPa, -1.8 hPa and t -3.15 hPa; Von Mises peak stress values were 340.0 MPa, 315.5 MPa and 326.1 Mpa, for DHS, DHS with anti-rotation device, and ASNIS, respectively. Conclusion: The DHS combined with anti-rotation screw yielded better results in terms of rotational and vertical displacements, traction and compression distributions on fractures, and Von Mises stress, demonstrating mechanical superiority for Pauwels Type III fracture.