Optimum Configuration of Cannulated Compression Screws for the Fixation of Unstable Femoral Neck Fractures: Finite Element Analysis Evaluation

Biomechanical analysis of various internal fracture fixation devices used for treating femoral neck fractures: A comparative finite element analysis

INTRODUCTION

Several internal fixation devices are available for treating Pauwels type I, II and III femoral neck fractures. The present study compared various fixation implants for all Pauwels fracture types using a CT-based subject-specific finite element model of the femur and determined the most effective implant for each fracture type.

MATERIALS AND METHODS

The analysis included four different configurations of cannulated screw models, Femoral Neck System, Dynamic Hip Screw and Dynamic Condylar Screw (with and without anti-rotational screw). Ti-alloy was considered as the implant material. Heterogeneous bone material property was assigned based on CT grey value. Frictional contact was assumed in the contact interfaces. Peak loading corresponding to normal walking and stair-climbing were considered. Equivalent strain in bone, equivalent stress in the implants, femoral head deformation and rotation, micromotion in the contact interfaces, and strain-shielding in bone were evaluated for each implanted model.

RESULTS

Stresses generated in the implants were within the yield limit of the implant material. In Pauwels I and II, the micromotion predicted at the contact regions in all the implanted models was within 100 µm, which is suitable for bone integration. However, in Pauwels III fracture, most of the implanted models other than DHS with AR-screw model exhibited micromotion of more than 150 µm in the contact regions, which is expected to inhibit bone growth.

CONCLUSIONS

The DHS with AR-screw implanted model was identified as the most effective in treating Pauwels I and III fractures. However, for Pauwels type II, DCS with an AR-screw implant was deemed superior to the other configurations.

Global trends of Pauwels type III femoral neck fractures: bibliometric analysis and visualized study

Background

Pauwels type III femoral neck fractures, as a serious type of femoral neck fractures, have brought about a heavy economic burden on families and society for the high disability rate. Through bibliometric research and visualized analysis, this study aimed at elucidating the global research status of Pauwels type III femoral neck fractures to date, and predicting the future research trends in this field.

Methods

Publications and associated information on Pauwels type III femoral neck fractures to date were retrieved from Web of Science Core Collection, and by VoSviewer and R package "bibliometrix", bibliometric analysis and visual presentation was conducted.

Results

By retrieval, a total of 98 studies were refinedly extracted, and the volume of publications in this field increased year-over-year. China ranked first in terms of total publication volume and H-Index, with its total citation records second only to the United States. The country with the highest average citation frequency was Switzerland. SHANGHAI JIAO TONG UNIVERSITY was the most productive research institution. Among the authors in this field, Li, Jiantao had published the most researches. INJURY INTERNATIONAL JOURNAL OF THE CARE OF THE INJURED and JOURNAL OF ORTHOPAEDIC TRAUMA were the two magazines with the highest publication volume, total citation records, and H-index. According to keywords co-occurrence analysis, the research content in the past 24 years is mainly divided into four different dimensions. Finite element analysis, femoral neck system, medial buttress plate, cannulated screws, hip screw, open reduction, complications are hot topics for future research.

Conclusions

According to the global trends analysis of publications production, Pauwels type III femoral neck fractures are receiving increasing attention and input from scholars. China has made the greatest scientific research contribution among countries, but its academic quality should be improved further. The modified therapeutic methods designed for addressing the complications of traditional internal fixation for Pauwels III femoral neck fractures will be the future research hotspot.

Low avascular necrosis rates in femoral neck fractures: efficacy of cannulated screw fixation

PURPOSE

Cannulated screw fixation for femoral neck fractures is often limited by concerns of avascular necrosis (AVN) occurring, historically seen in 5-40% of fixed intracapsular fractures. This study aims to assess the outcomes, particularly the AVN rate, associated with current surgical techniques within our unit.

METHODS

We conducted a single-center cross-sectional study, manually searching operative records between July 14, 2014, and December 1, 2018, identifying patients with intracapsular fractured neck of femur fixed with cannulated screws, with a minimum of two years follow-up. Patient records and radiographs were reviewed for clinical and radiographic diagnoses of AVN, non-union, post-operative metalwork infection, and screw penetration of the head. Additionally, fracture pattern and displacement, screw configuration, reduction techniques, and adequacy of reduction were recorded, with radiographs independently analyzed by four orthopedic surgeons.

RESULTS

Fifty-six patients were included; average age of 67 years (range 30-100). Forty-two patients (75%) sustained displaced fractures and 14 patients (25%) had undisplaced fractures. Two (4%) patients developed AVN, with no cases of non-union, post-operative metalwork infection or screw penetration of the head. Eight patients (14%) sustained a high-energy injury, though none of these patients developed AVN. All fractures required closed reduction; no open reductions performed. Twenty-seven (64%) of reductions were adequate.

CONCLUSION

Our observed AVN rate is notably lower than the widely reported figures, even among a significant proportion of displaced fractures that were fixed. This study underscores that with adequate fixation, cannulated screws represent an excellent option for treating intracapsular neck of femur fractures, even in cases of displaced fracture patterns with imperfect reduction.

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

BACKGROUND

Femoral neck system (FNS) has exhibited some drawbacks, such as non-fit of the plate with the lateral femoral cortex, postoperative pain, and the potential risk of subtrochanteric fractures. We have developed a low-profile FNS system that addresses some compatibility issues in FNS. In this study, we conducted finite element analysis on the 1-hole FNS (1 H-FNS), 2-holes FNS (2 H-FNS), and low-profile FNS (LP-FNS) and compared their biomechanical performance.

METHODS

After the mesh convergence analysis, we established three groups of 1 H-FNS, 2 H-FNS, and LP-FNS. The interfragmentary gap, sliding distance, shear stress, and compressive stress and the bone-implant interface compression stress, stiffness, and displacement were determined under the neutral, flexion, or extension conditions of the hip joint, respectively. The stress and displacement of the femur after the implant removal were also investigated.

RESULTS

(1) There were no obvious differences among the three FNS groups in terms of the IFM distance. However, the LP-FNS group showed less rotational angle compared with conventional FNS (neutral: 1 H-FNS, -61.64%; 2 H-FNS, -45.40%). Also, the maximum bone-implant interface compression stress was obviously decreased under the neutral, flexion, or extension conditions of the hip joint (1 H-FNS: -6.47%, -20.59%, or -4.49%; 2 H-FNS: -3.11%, 16.70%, or -7.03%; respectively). (2) After the implant removal, there was no notable difference in the maximum displacement between the three groups, but the maximum von Mises stress displayed a notable difference between LP-FNS and 1 H-FNS groups (-15.27%) except for the difference between LP-FNS and 2 H-FNS groups (-4.57%).

CONCLUSIONS

The LP-FNS may not only provide the same biomechanical stabilities as the 1 H-FNS and 2 H-FNS, but also have more advantages in rotational resistance especially under the neutral condition of the hip joint, in the bone-implant interface compression stress, and after the implant removal. In addition, the 1 H-FNS and 2 H-FNS have similar biomechanical stabilities except for the maximum von Mises stress after the implant removal. The femur after the LP-FNS removal not only is subjected to relatively little stress but also minimizes stress concentration areas.

Structural characteristics, biomechanics and clinical significance of calcar femorale: A review

The calcar femorale, first identified by Merkel in 1874, plays a pivotal role in the weight-bearing capacity of the proximal femur, and its structural integrity is crucial for the efficient distribution of mechanical loads. Originating at the vertical ridge where the pubofemoral ligament anchors, this bony prominence extends laterally behind the neutral axis from the medial to lateral aspects. Its presence is not merely an anatomical curiosity but significantly influences the biomechanics of the hip joint by providing additional strength and support against compressive forces encountered during activities such as walking or jumping. Despite its clear description in orthopedic texts, misconceptions persist about its exact function and importance. This article delves into the nuanced anatomy and biomechanical properties of the calcar femorale, offering a detailed literature-based examination that demonstrates its relevance in clinical practice. The review highlights how the robustness of the calcar femorale contributes to the prevention of femoral neck fractures as well as the stabilization of hip prostheses. Furthermore, the indispensable role of the calcar femorale in surgical outcomes is discussed, especially in the context of fracture repair and joint replacement, thus illustrating its enduring significance in contemporary medical applications.

Factors associated with increased radiation exposure in the fixation of proximal femoral fractures

INTRODUCTION

When using radiation intraoperatively, a surgeon should aim to keep the radiation dose as low as is reasonably achievable to obtain the therapeutic goal. We aimed to investigate factors associated with increased radiation exposure in fixation of proximal femur fractures.

METHODS

We assessed 369 neck of femur fractures over a 1-year period in a district general hospital. All hip fracture subtypes that had undergone surgical fixation were included. We assessed the relationship between type of fracture, implants used and surgeon level of experience with the dose-area product (DAP; cGy/cm2) and screening time (dS). We also looked at the quality of reduction and fixation and its effect on the radiation exposure.

RESULTS

A total of 184 patients were included in our analysis; 185 patients who were treated with hip arthroplasty were excluded. There was a significant association between higher DAP and fracture subtype (p = 0.001), fracture complexity (p < 0.001), if an additional implant was used (p = 0.001), if fixation was satisfactory (p = 0.002) and operative time (p < 0.001). DAP was higher with a proximal femoral nail than with a dynamic hip screw, especially when a long nail was used. There was some evidence of an association between the surgeon's level of experience and DAP exposure, although this was not statistically significant (p = 0.069).

CONCLUSIONS

Increased radiation in proximal femur fractures is seen in the fixation of complex fractures, some subtypes, with certain types of implants used and if an additional implant was required. Surgeon seniority did not result in less radiation exposure, which is in contrast to other published studies.

Biomechanical Research of Three Parallel Cannulated Compression Screws in Oblique Triangle Configuration for Fixation of Femoral Neck Unstable Fractures

OBJECTIVE

Surgical treatment with internal fixation, specifically percutaneous fixation with three cannulated compression screws (CCSs), is the preferred choice for young and middle-aged patients. The mechanical advantage of the optimal spatial configuration with three screws provides maximum dispersion and cortical support. We suspect that the spatial proportion of the oblique triangle configuration (OTC) in the cross-section of the femoral neck isthmus (FNI) may significantly improve shear and fatigue resistance of the fixed structure, thereby stabilizing the internal fixation system in femoral neck fracture (FNF). This study aims to explore the mechanical features of OTC and provide a mechanical basis for its clinical application.

METHODS

Twenty Sawbone femurs were prepared as Pauwels type III FNF models and divided equally into two fixation groups: OTC and inverted equilateral triangle configuration (IETC). Three 7.3 mm diameter cannulated compression screws (CCSs) were used for fixation. The specimens of FNF after screw internal fixation were subjected to static loading and cyclic loading tests, respectively, with five specimens for each test. Axial stiffness, 5 mm failure load, ultimate load, shear displacement, and frontal rotational angle of two fragments were evaluated. In the cyclic loading test, the load sizes were 700 N, 1400 N, and 2100 N, respectively, and the fracture end displacement was recorded. Results were presented as means ± SD. Data with normal distributions were compared by the Student's t test.

RESULTS

In the static loading test, the axial stiffness, ultimate load, shear displacement, and frontal rotational angle of two fragments were (738.64 vs. 620.74) N/mm, (2957.61 vs. 2643.06) N, (4.67 vs. 5.39) mm, and (4.01 vs. 5.52)° (p < 0.05), respectively. Comparison between the femoral head displacement after 10,000 cycles of 700N cyclic loading and total displacement after 20,000 cycles of 700-1400N cyclic loading showed the OTC group was less than the IETC group (p < 0.05). A comparison of femoral head displacement after 10,000 cycles of 1400N and 2100N cycles and total displacement after 30,000 cycles of 700-2100N cycles showed the OTC group was less than another group, but the difference was not significant (p > 0.05).

CONCLUSION

When three CCSs are inserted in parallel to fix FNF, the OTC of three screws has obvious biomechanical advantages, especially in shear resistance and early postoperative weight-bearing, which provides a mechanical basis for clinical selection of ideal spatial configuration for unstable FNF.

[Translated article] The configuration of the screws in the osteosynthesis of fractures of the femoral neck does not influence the functional or mechanical outcomes

BACKGROUND AND OBJECTIVE

Synthesis with cannulated screws is one of the accepted methods in femoral neck fractures, although its optimal configuration is a subject in continuous debate. The main objective was to compare the results of the patient with a femoral neck fracture fixed with three screws in triangle and inverted triangle configuration in the frontal plane.

MATERIALS AND METHODS

Retrospective and comparative study of 53 patients with femoral neck fracture, operated between 2015 and 2022 with fixation with three cannulated screws, 22 with a triangle configuration (triangle group) and 31 in an inverted triangle (inverted triangle group). Functionality was evaluated using the modified Merlé d'Aubigné scale, walking ability using the Koval scale, as well as postoperative complications.

RESULTS

On the Merlé d'Aubigné scale, the mean score was 16.7 in the triangle group and 16.1 in the inverted triangle group (p=.259). On the Koval scale, a significant decrease was observed, going from 1.6 preoperative mean to 2.2 after surgery (p=.000), finding no differences between groups. There were six postoperative complications in the triangle group and three in the inverted triangle group (p=.140).

CONCLUSION

The configuration of the screws in the femoral neck, both in the form of a triangle and an inverted triangle, did not influence the functional or mechanical outcomes of the patients with a femoral neck fracture fixed with three cannulated screws.

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.

Biomechanical comparison of fixation methods on third-generation femoral composite bone models in Pauwels type 3 femoral neck fractures: Contribution of the medial buttress plate to fixation

OBJECTIVE

To compare the use of cannulated screws in an inverted triangular configuration, medial buttress plates, and the combination of these 2 fixation methods in the treatment of Pauwels type 3 femoral neck fractures.

METHODS

Twenty-eight anatomical composite third-generation femoral bone models were divided into 4 groups. The control group (group 1) was formed with 7 third-generation intact bone models. The fracture model was created with a 70° cutting block to fit 21 Pauwels type 3 fracture configurations. Seven models were fixed with an isolated 3.5 mm one-third semi-tubular medial buttress plate (group 2), 7 were fixed in an inverted triangular configuration with 6.5 mm cannulated screws (group 3), and 7 were fixed using a combination of 6.5 mm cannulated screws and a medial buttress plate (group 4). Cyclic loading was applied using axial forces ranging from 60 N to 600 N and moments ranging from 0.7 Nm to 7.0 Nm for 500 cycles. Once the cyclic loading stage was completed, the loads were removed from the system, and the quasi-static loading stage was employed to determine the stiffness and failure forces of the system under both axial and torsional forces. Quasi-static tests were performed with an axial speed of 1.8 mm/min and a torsional speed of 4.5°/min. The biomechanical properties of all groups were examined in terms of axial stiffness, torsional stiffness, and maximum axial force parameters.

RESULTS

The stiffness values of groups 1, 2, 3, and 4 were 303 ± 35.8 N/mm, 159.6 ± 25 N/mm, 232 ± 35.9 N/mm, and 366.9 ± 58 N/mm, respectively, under axial forces (P < .01); 2172.7 ± 252.1 Nmm/°, 1225.3 ± 238.6 Nmm/°, 2123 ± 359.4 Nmm/°, and 2721.85 ± 304 Nmm/°, respectively, under torsional moments (P < .01); and 2072.1 ± 256.1 N, 1379.9 ± 290.6 N, 2099.1 ± 454.2 N, and 2648.4 ± 364.6 N, respectively, under the maximum force (P < .01).

CONCLUSION

This study showed that in the fixation of Pauwels type 3 fractures formed on third-generation bone models, the utilization of half-thread cannulated screws in an inverted triangle configuration, along with a medial buttress plate, provided stronger fixation compared to the remaining implant groups and the control group. According to the evaluation of the parameters, the isolated application of a medial buttress plate had poorer biomechanical properties than other fixation methods.

Biomechanical Comparison between Inverted Triangle and Vertical Configurations of Three Kirschner Wires for Femoral Neck Fracture Fixation in Dogs: A Cadaveric Study

The purpose of this study was to compare single-cycle axial load and stiffness between inverted triangle and vertical configurations of three Kirschner wires (K-wires) for femoral neck fracture fixation in small dog cadaveric models. In each of the eight cadavers, the basilar femoral neck fracture model was prepared on both sides of the femur. One side of the femur was stabilized with three 1.0 mm K-wires of an inverted triangle configuration (group T), and the other femur was stabilized with a vertical configuration (group V). Postoperatively, the placement of the K-wires was evaluated with radiographic and computed tomography (CT) images, and static vertical compressive loading tests were performed. The mean yield load and the lateral spread were significantly higher in group T compared to group V (p = 0.023 and <0.001). On the cross-section of femoral neck at the level of the fracture line, the surface area between K-wires was significantly larger (p < 0.001) and the mean number of cortical supports was significantly higher in group T (p = 0.007). In this experimental comparison, the inverted triangle configuration of three K-wires was more resistant to failure under axial loading than the vertical configuration for canine femoral neck fracture fixation.

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.

Biomechanical study of internal fixation methods for femoral neck fractures based on Pauwels angle

Objective: To select the most appropriate internal fixation method based on the Pauwels angle, in order to provide a new concept for clinical accurate treatment of femoral neck fractures (FNFs). Methods: FNFs models of Pauwels 30 ° ; 40 ° ; 50 ° ; 60 ° were created respectively. For Pauwels ≤ 50 ° , 1, 2 and 3 Cannulated Compression Screws (CCS) and Porous Tantalum Screws (PTS) were used to fix the fracture for the models. For Pauwels 60 ° , 3CCS and Medial Buttress Plate (MBP) combined with 1, 2 and 3CCS were used to fix the fracture. Based on the results of the finite element (FE) analysis, the biomechanical properties of each model were compared by analyzing and evaluating the following four parameters: maximal stress of the bone (MBS), maximal stress of the implants (MIS), maximal displacement of bone (MBD), interfragmentary motion (IFM). Results: At Pauwels 30 ° , the larger parameters were found in 1CCS, which was 94.8 MPa (MBS), 307.7 MPa (MIS), 0.86 mm (MBD) and 0.36 mm (IFM). In 2CCS group, the parameters were 86.1 MPa (MBS), 254.4 MPa (MIS), 0.73 mm (MBD) and 0.27 mm (IFM), which were similar to those of PTS. At Pauwels 40 ° ; 50 ° , with the increase of the number of used CCS, accordingly, the parameters decreased. Particularly, the MIS (Pauwels 50 ° ) of 1CCS was 1,195.3 MPa, but the other were less than the yield range of the materials. At Pauwels 60 ° , the MBS of 3CCS group was 128.6 Mpa, which had the risk of failure. In 2CCS + MBP group, the parameters were 124.2 MPa (MBS), 602.5 MPa (MIS), 0.75 mm (MBD) and 0.48 mm (IFM), The model stability was significantly enhanced after adding MBP. Conclusion: Pauwels type Ⅰ (< 30 ° ) fractures can reduce the number of CCS, and PTS is an appropriate alternative treatment. For Pauwels type Ⅱ fractures ( 30 ° ∼ 50 ° ), the 3CCS fixation method is still recommended. For Pauwels type Ⅲ fractures (> 50 ° ), it is recommended to add MBP to the medial femoral neck and combine with 2CCS to establish a satisfactory fracture healing environment.

Should cannulated screws be removed after a femoral neck fracture has healed, and how? A finite element analysis of the femur before and after cannulated screw removal

PURPOSE

The removal of three inverted triangular parallel cannulated screws after the femoral neck fracture healing is sometimes accompanied by osteonecrosis of the femoral head (ONFH) or its refracture. The purpose of this study was to determine the biomechanical changes of the femur before and after the screw removal using a finite element analysis.

METHODS

The CT data of the femurs were obtained from a 69-year-old healthy female to establish the femur models. The established finite element models consisted of N, C, and R groups: N group, the normal femur; C group (to simulate the femoral neck fracture healing after the internal fixation), the normal femur with three inverted triangular parallel cannulated screws (C1) or with two upper parallel screws (C2). For the R1 or R2 groups, the screws in the model of the C1 or C2 individuals were gradually removed in seven or three types of different screw combinations, respectively. The stresses and displacements of the femur were determined.

RESULTS

(1) Compared with the N group, a uniform stress distribution was stopped by the addition of three screws in the C1 group; in contrast, all screw removals resulted in the stress concentration on the screw holes and the disappearance of stress shielding. Moreover, the average stress of the femoral head in C1 group increased by 37.85%, while that of the femoral neck decreased by 23.03%. (2) Compared with the C1 group, while only the lowest femoral calcar screw was removed, there was a similar stress distribution in the proximal femur, and the average stress of the femoral head increased only by 0.35% although that of the femoral neck increased by 63.62%; however, removal by any other means resulted in a significant stress concentration in the proximal femur and a significant increase in the average stresses of the femoral head and neck (5.96-40.95% and 12.82-75.46%, respectively). (3) Compared with the N or C1 group, there was a significant stress concentration on the screws and its surrounding proximal femur in the C2 group. (4) Compared with the C2 group, the simultaneous removal of two upper screws not only did not cause a significant stress concentration on the proximal femur but also significantly reduced the average stresses of the femoral head and neck by 87.49% and 65.51% respectively. On the contrary, the gradual removal of two screws caused a significant stress concentration on the screw and its surrounding proximal femur although the average stresses of the femoral head and neck decreased by 88.79-89.06% and 67.00-67.22%, respectively. (5) Compared with the N group, the average displacements of the femoral head and neck in the C1 group increased only by 3.12% and 3.37%, respectively. Additionally, compared with the C1 group, while three, two, or one screw was simultaneously removed, the average displacements of the femoral head and neck only fluctuated - 5.51-1.65% and 1.78-9.03%, respectively.

CONCLUSIONS

Residual internal fixation after femoral neck fracture healing may lead to stress concentration on screws and stress shielding around screws. The first removal of the lowest femoral calcar screw and then the second removal of two upper residual screws have a minimum effect on the stress concentration on the proximal femur and the average stress on the femoral head. The incorrect screw removal and resulting femoral load may well be closely related to occurrence in ONFH or its refracture.

Finite element analysis of femoral neck system in the treatment of Pauwels type III femoral neck fracture

The optimal treatment strategy for femoral neck fractures remained controversial, especially the Pauwels type III femoral neck fracture of young patients was a challenge. Femoral neck system (FNS) was a newly developed internal fixation for treating femoral neck fracture and this study aimed to compare the biomechanical advantages and disadvantages between FNS and 3 cannulated configuration screws (CCS) with or without an additional medial buttress plate (MBP). In this study, Pauwels type III femoral neck fracture model with an angle of 70° was constructed and 3 different fixation models, FNS, CCS + MBP, CCS alone, were developed. A vertical force of 2100N was applied on the femoral head, then the maximum von Mises stress of whole model, distal femur, femoral head, and internal fixation was recorded, as well as the stress distribution of whole model, proximal fracture section, and internal fixation of the 3 models. Moreover, the maximum displacement of the whole model, distal femur, femoral head, internal fixation, and the relative displacement of the proximal and distal portion was also compared. The maximum von Mises stress value was 318.302 MPa in FNS, 485.226 MPa in CCS + 1/3 plate, and 425.889 MPa in CCS. The FNS showed lowest maximum von Mises stress values in distal part, femoral head, and internal implant. All fixation configurations were observed stress concentrated at the posteroinferior area of cross-section of femoral head and at the fracture section area of implant; however, FNS had more uniform stress distribution. For displacement, the maximum displacement value was 8.5446 mm in FNS, 8.2863 mm in CCS + 1/3 plate, and 8.3590 mm in CCS. However, FNS had higher maximum displacement in femoral head and internal implant, but lower maximum displacement in the distal part of fracture model. The FNS represented a significantly higher relative displacement between the femoral head and distal femur when compared with the other 2 fixation configurations. The newly developed FNS could achieve the dual effect of angular stability and sliding compression for the treatment of Pauwels type III femoral neck fractures, which provided superior biomechanical stability than CCS alone and CCS with additional MBP.

A comparison between the femoral neck system and other implants for elderly patients with femoral neck fracture: A preliminary report of a newly developed implant

BACKGROUND

Femoral neck system (FNS) is an implant for patients with femoral neck fracture. It has superior angular and rotatory stability; it is less invasive because of its established locking plate system. To the best of our knowledge, there are no studies yet concerning the clinical outcomes of elderly patients with femoral neck fracture who have been treated using the FNS.

METHODS

Data of patients with femoral neck fracture aged >65 years and who had undergone internal fixation with the FNS and other implants were retrospectively analyzed in this study. The follow-up period was a minimum of six months between January 2006 and November 2020. In total, 52 patients were included in the clinical evaluations, using the FNS (group F) was 25 and using other implants (group O) was 27. Outcome measurements were surgical time, the amount of blood loss, union rate and the cases that underwent reoperation.

RESULTS

The average surgical time in the group F was 42 ± 13 min (range: 26-83 min) and was shorter than that in the group O (53 ± 21 min, range: 13-111 min, P = 0.032). The average blood loss in the group F was calculated to 36 ± 25 g (range: 0-91 g), while it was 41 ± 40 g (range: 0-169 g) in group O. No significant difference among the groups. The union rate of the group F was 100%, and the reoperation rate of the group F was significantly less than that of the group O (0% vs 22%, P = 0.023).

CONCLUSION

Internal fixation using the FNS can be an alternative option with shorter surgical time and lower reoperation rate for elderly patients with femoral neck fracture.

Effect of the Number, Size, and Location of Cannulated Screws on the Incidence of Avascular Necrosis of the Femoral Head in Pediatric Femoral Neck Fractures: A Review of 153 Cases

BACKGROUND

The correlation between the number, size, and location of cannulated screws and the incidence of avascular necrosis (AVN) in children with femoral neck fractures treated surgically is uncertain.

METHODS

We retrospectively reviewed 153 children (mean age: 10.6±3.7 y) with femoral neck fractures treated by internal fixation with 2 (n=112) or 3 (n=41) cannulated screws. The severity of initial displacement was divided into incomplete (type I) and complete (type II, angulation <50 degrees; type III, angulation >50 degrees) fractures. The diameter of the screw was measured and recorded as a percentage of the femoral neck width. The distance (D) between the mid-point of each screw at the base (B) of the femoral neck and at the tip (T) of each screw and the superior and anterior cortices of the femoral neck, respectively, were measured on anteroposterior (AP) and lateral (L) radiographs. Values were expressed as the ratio between the measured distance and the width of the femoral neck (BDAP%, TDAP%, BDL%, and TDL%). The correlation between the number, size, and location of the screws and AVN was analyzed.

RESULTS

Patients with type II of initial displacement treated with 2 cannulated screws had a lower AVN rate (21.4%) than those treated with 3 screws (44.8%) (P=0.027). Screw diameter (19%) in patients with AVN was larger than (17%) in patients without AVN (P<0.001); patients with AVN had a lower BDAP% (48.6%) than those without AVN (56.4%) (P<0.001). Screw size and BDAP% were risk factors for AVN (P<0.05). Further, screw diameter >16.5% and BDAP% <51.6% of the femoral neck width were the cutoff values for an increased AVN rate (P<0.05).

CONCLUSIONS

Patients treated with 2 cannulated screws showed a lower rate of AVN than patients treated with 3 screws. Screws of larger size and screws closer to the piriformis fossa on AP radiographs increased the risk of AVN in children with femoral neck fractures treated surgically.

LEVEL OF EVIDENCE

Level III.

Comparison of oblique triangular configuration and inverted equilateral triangular configuration of three cannulated screws in treating unstable femoral neck fracture: A finite element analysis

BACKGROUND

The cross-sectional area of three parallel screws might affect the stability of the internal fixation of femoral neck fractures. The screws fixed in the oblique-triangle configuration (OTC) were assumed to have a larger cross-sectional area, but the biomechanical stability has not yet been validated. In this study, finite element analyses were performed to compare the biomechanical properties of the internal fixation fixed by the OTC and the traditional Inverted Equilateral Triangle Configuration (IETC).

METHOD

Pauwels type III fracture was established on the three-dimensional femoral model and three cannulated screws with the OTC and traditional IETC methods were applied. The oblique-triangle configuration with the largest area inscribed the femoral neck isthmus by the three screws was determined, the area and circumference of the cross-section formed by the OTC and IETC model were compared. Stress, strain, and displacement peaks of the two configuration models under different loads were compared. Twelve pairs of nodes on the fracture ends were selected and the displacement of the fracture ends was evaluated through the displacement between these nodes.

RESULTS

The area and circumference of the cross-section formed by the OTC were larger than those in the IETC model. The degree of stress dispersion around the screw holes in the OTC model was better than that of the IETC, but the stress distribution order of the three screws in the two models was consistent. The maximum stress, strain, displacement, and displacement of the fracture end in the OTC model were smaller than those in the IETC model. The stress, strain, displacement, and fracture end displacement peaks of the two fixed models gradually increase with the increase of loads.

CONCLUSION

The oblique-triangle configuration showed superior mechanical properties than the IETC in finite element analyses. This study suggests that when three screws are fixed in parallel method, the larger the cross-sectional area of the screw configuration, the better stability of the internal fixation might be obtained. Furthermore, the biomechanical properties of various spatial configurations and screw holes of the three parallel screws need to be considered before clinical practice.

The oblique triangle configuration of three parallel screws for femoral neck fracture fixation using computer-aided design modules

Closed reduction and internal fixation with three cannulated compression screws is a common method for treating femoral neck fractures in young and middle-aged patients. Protocols including the inverted triangle configuration and dispersion of the screws still needed further supports. The purpose of this study was to explore a novel oblique triangle configuration (OTC) of three screws in fixing femoral neck fractures based on the morphology of the femoral neck isthmus (FNI). The computer-aided design modules were used to explore the ideal spatial configuration with largest triangle by three parallel screws. A univariate evaluation model was established based on the oval-like cross-section of the FNI. When the three screws were positioned by the OTC, Inverted Equilateral Triangle Configuration (IETC), and the Maximum Area Inverted Isosceles Triangle Configuration (MA-IITC) respectively, the proportion of area and circumference in the cross-section of FNI and the changing trend of proportion were compared under various torsion angles, eccentricity, and cross-sectional area of FNI. The area and circumference ratios of the parallel screws using the OTC method were significantly higher than in the IETC and MA-IITC groups. In the univariate evaluation model, the OTC area ratio and circumference ratio remained stable under the different femoral neck torsion angles, FNI cross-sectional area, and eccentricity. The OTC method provided an ideal spatial configuration for the FNA fixation with the largest area using three parallel screws. The position of the posterior screw was also away from the metaphyseal artery, potentially reducing the possibility of vascular injury and screw penetrating.

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

BACKGROUND

No consensus has been reached for the treatment of vertical femoral neck fractures (vFNFs). Recently, two alternative methods were invented to treat vFNFs, one of which is a new plate with a sliding groove, which was designed as a substitution of the medial buttress locking plate to combine with cannulated compression screws (CCS) for reducing the breakage possibility of the proximal locking screw during the bone healing. Another one is the femoral neck system (FNS), which was believed with biomechanical superiority. This study aims to compare the biomechanics of these two new implants with three previous methods via finite element analysis (FEA) to validate whether they are suitable for the treatment of vFNFs.

METHODS

Five 70-degree Pauwels type III transcervical FNFs (vFNFs, AO/OTA 31B2.3^r) models were built and fixed by CCS augmented with the newly designed sliding groove buttress plate (CCS+BS) and FNS. For comparison, models fixed by three parallel cannulated compression screws (CCS), biplane double-supported screw fixation (BDSF), CCS augmented with a medial buttress locking plate (CCS+BL) were also built. A 2100N load was applied along with the mechanical axis. Parameters of the maximal stress as well as the maximal displacement of the implants and bone, the maximal relative displacement of interfragments, and the stiffness, were analyzed to compare the biomechanical characteristics of the five models.

RESULTS

CCS+BS and CCS+BL showed stronger fixation strength with improved stiffness (1012.05N/mm, 1092.04N/mm), reduced maximal displacement of the implants (1.976mm, 1.838mm) and bone (2.075mm, 1.923mm), when compared with CCS (925.11N/mm, 2.158mm and 2.270mm) and BDSF (842.36N/mm, 2.299mm and 2.493mm). While FNS showed the weakest stiffness (593.22N/mm) and largest maximal displacement of the implants (3.234mm) and bone (3.540mm) among the five models.

CONCLUSIONS

CCS+BS has a better biomechanical performance than CCS and BDSF, which offers a new choice to deal with vFNFs. The construction stability of FNS is weaker than CCS, BDSF, and CCS+BL, indicating that this method may not as stable as reported in the previous study.

Controversies in the management of pediatric neck femur fractures- a systematic review

Purpose

To review controversies systematically in the management of pediatric neck femur fracture from the literature and to develop consensus for the optimum management.

Methods

Authors searched literature by using keywords of pediatric neck femur fracture, proximal femur fracture, complications, management by following PRISMA guidelines. A common dilemma was listed.

Results

Age, mechanism of injury, fracture type, presentation, treatment method, implant, and nature of complications were compared. Inference from recent literature was extracted for optimum management.

Conclusion

Immediate anatomical reduction with stable fixation must be accomplished. Complications continue to happen despite the best efforts and a longer follow-up is important.

The Effect on the Fracture Healing following Femoral Neck Shortening after Osteoporotic Femoral Neck Fracture Treated with Internal Fixation: Finite Element Analysis

Objective

To evaluate the stress status of fracture site caused by femoral neck shortening and to analyze the stress of fracture site and the implants from the finite element point of view.

Methods

CT scan data of hip of a normal adult female were collected. Three-dimensional reconstruction MICs and related module function simulation was used to establish the postoperative shortening model of femoral neck fracture with Pauwels angle > 50°, which was treated with cannulated screws. The models were divided into four groups: normal femoral neck, shortening in 2.5 mm, shortening in 7.5 mm, and shortening in 12.5 mm. The finite element analysis software msc.nastran2012 was used, and the data of maximum stress and stress nephogram of fracture site and implants were carried out.

Results

From normal femoral neck to shortening in 12.5 mm of the femoral neck, the maximum tensile stress increased gradually in the fracture site above the cannulated screws while compressive stress decreased gradually in the fracture site below the cannulated screws, and the maximum stress of the cannulated screws increased gradually with obvious stress concentration at the screw holes in the fracture site, and the peak value of stress concentration was about 179 MPa.

Conclusion

The biomechanical environment of the fracture site changed by femoral neck shortening. With the increasing of femoral neck shortening, the stress of the fracture site and implants would be uneven; then, the stability of fracture site would become worse, and the possibility of implant sliding or even breakage would be increased.

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.

Migration Measurement of Pins in Postoperative Recovery of the Proximal Femur Fractures Based on 3D Point Cloud Matching

Background and objectives: Internal fixation is one of the most effective methods for the treatment of proximal femur fractures. The migration of implants after the operation can seriously affect the reduction of treatment and even cause complications. Traditional diagnosis methods can not directly measure the extent of displacement. Methods: Based on the analysis of Hansson pins, this paper proposes a measurement method based on three-dimensional matching, which uses computerized tomography (CT) images of different periods of patients after the operation to analyze the implants' migration in three-dimensional space with the characteristics of fast speed and intuitive results. Results and conclusions: The measurement results show that the method proposed in this paper has more minor errors, more flexible coordinate system conversion, and more explicit displacement analysis than the traditional method of manually finding references in CT images and measuring displacement.

The Oval-like Cross-section of Femoral Neck Isthmus in Three-dimensional Morphological Analysis

Objectives

To investigate the cross‐section shape of the femoral neck isthmus (FNI) in three‐dimensional reconstruction model of the femoral neck.

Methods

From December 2009 to December 2012, computed tomography (CT) data of bilateral hip joint from 200 consecutive patients (137 males and 63 females, 69.41 ± 9.21 years old, ranged from 50–85 years old) who underwent surgical treatments for proximal femoral fracture were retrospectively reviewed. The 3D model of the proximal femur was reconstructed, and the “inertia axis” method, which was applied to measure the long and short axes of the cross‐section of the FNI, was established. The cross‐sectional area and perimeter were calculated by a formula using the length of the long and short axes and then compared with the actual measured values by the software. Correlation between the descriptive parameters of the FNI cross‐section (area, perimeter, and eccentricity) and patients' demographics (age, height, and weight) was analyzed. Stepwise linear regression analysis was used to determine the main relevant factors.

Results

The ICC results showed excellent data reproducibility ranged from 0.989 to 0.996. There was no significant difference in the cross‐sectional area of the FNI between the actual measured values and the predicted values using the formula (732.83 ± 126.74 mm²vs 731.62 ± 128.15 mm², P = 0.322). The perimeter using the two methods showed narrow while significant difference (97.86 ± 8.60 mm vs 92.84 ± 8.65 mm, P < 0.001), the actual measured values were about 5 mm greater than the predicted values. The parameters (area, perimeter, and eccentricity) were significantly larger in male than female (P < 0.001). A positive correlation between the cross‐sectional area, perimeter, height, and weight was observed. The stepwise linear regression analysis showed that the regression equation of the FNI area was as follows: Y = −1083.75 + 1033.86 × HEIGHT + 1.92 × WEIGHT, R² = 0.489.

Conclusion

The cross‐section shape of the FNI appears to be oval‐like in the 3D model, which is separated according to the inertia axis, and the findings proposed an anatomical basis for the further study of the spatial configuration of cannulated screws in the treatment of femoral neck fractures.

Current controversies in management of fracture neck femur in children: A review

Paediatric femur neck fracture is an uncommon injury and is known for high rate of complications. This in turn, can have significant impact on development of hip and overall function of the child. Controversy prevails in many areas of management and it still remains a difficult injury to manage. Through this paper, an attempt has been made to summarize the current concepts in management and suggest current recommendations regarding the controversies so that these injuries can be managed judiciously. A systematic review was done as per PRISMA guidelines using pre-defined inclusion and exclusion criteria. 18 studies with better scientific evidence after quality assessment were included in the systematic review. Current trends and Controversial issues in management were then identified and discussed. It was observed that existing literature is inconclusive regarding several aspects of management of this injury with no clear guideline available. However, certain recommendations useful for decision making could be made. These injuries should be managed aggressively with operative fixation at the earliest and one should not hesitate to open reduce if acceptable alignment is not obtained after one or two gentle closed manipulations. Choice of implant and their configuration in neck can vary depending on age and weight of patient, type of injury and surgeon's preference. Initial fracture displacement could be considered to be most predictive for development of osteonecrosis of the femoral head, whereas, role of surgical decompression, type of fixation and timing of surgery is still debatable. Functional outcome is primarily affected by osteonecrosis of the femoral head, nonunion and severe coxa vara, whereas mild coxa vara, shortening, and premature closure of physis when considered alone, don't have significant influence on functional outcome in short term. Treatment of fracture neck femur in children is still controversial in many aspects and needs further research. It should be understood that complications can occur regardless of the method of treatment and might reveal their full impact many years after injury. Hence, a guarded prognosis should be explained to the parents and care-givers at the time of injury.

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.

A quantitative biomechanical study of positive buttress techniques for femoral neck fractures: a finite element analysis

Background:

Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing. We evaluated the biomechanical effects of positive, negative, and anatomic reduction of various degrees of displacement in Pauwels I femoral neck fractures by a finite element analysis.

Methods:

Five reduction models of Pauwels type I femoral neck fracture were established using the Mimics 17.0 (Materialize, Leuven, Belgia) and Hypermesh 12.0 (Altair Engineering, Troy, MI, USA). According to the degree of fracture displacement, there were three models of positive support, an anatomic reduction model, and a negative 2 mm reduction model. Finite element analysis was conducted using the ABAQUS 6.9 software (Simulia, Suresnes, France). The von Mises stress distribution and the stress peak of internal fixation in different models, the displacement between fracture blocks, and the principal strain of the femoral neck cancellous bone model were recorded under the axial stress of 2100 N.

Results:

The peak von Mises stress on screw of each model was located at the thread of the screw tip. The peak von Mises stress was the lowest at the tip of the anatomic reduction model screw (261.2 MPa). In the positive 4 mm model, the von Mises stress peak was the highest (916.1 MPa). The anatomic reduction model showed the minimum displacement (0.388 mm) between fracture blocks. The maximum displacement was noted in the positive 4 mm model (0.838 mm). The displacement in the positive 3 mm model (0.721 mm) was smaller than that in the negative 2 mm model (0.786 mm). Among the five models, the strain area of the femoral neck cancellous bone was mainly concentrated around the screw hole, and the area around the screw hole could be easily cut.

Conclusions:

Compared with negative buttress for femoral neck fracture, positive buttress can provide better biomechanical stability. In Pauwel type I fracture of femoral neck, the range of positive buttress should be controlled below 3 mm as far as possible.

The Influence of Geometry of Implants for Direct Skeletal Attachment of Limb Prosthesis on Rehabilitation Program and Stress-Shielding Intensity

The purpose of the research was to evaluate the influence of selected parameters of the implants for bone anchored prostheses on possibility of conducting static load bearing exercises and stress-shielding intensity. A press-fit implant, a threaded implant, and the proposed design were compared using the finite element method. For the analyses two features were examined: diameter (19.0 – 21.0 mm) and length (75.0 – 130.0 mm). To define the possibility of conducting rehabilitation exercises the micromotion of implants while axial loading with a force up to 1000 N was examined to evaluate the changes at implant-bone interface. The stress-shielding intensity was estimated by bone mass loss over 60 months. The results suggest that, in terms of micromotion generated during rehabilitation exercises, the threaded (max. micromotion of 16.00 μm) and the proposed (max. micromotion of 45.43 μm) implants ensure low and appropriate micromotion. In the case of the press-fit solution the load values should be selected with care, as there is a risk of losing primary stabilisation. The allowed forces (that do not stimulate the organism to generate fibrous tissue) were approx. 140 N in the case of the length of 75 mm, increasing up to 560 N, while using the length of 130 mm. Moreover, obtained stress-shielding intensities suggest that the proposed implant should provide appropriate secondary stability, similar to the threaded solution, due to the low bone mass loss during long-term use (improving at the same time more bone remodelling in distal Gruen zones, by providing lower bone mass loss by approx. 13% to 20% in dependency of the length and diameter used). On this basis it can be concluded that the proposed design can be an appropriate alternative to commercially used implants.