Abstract
Objective
The biomechanical characteristics of proximal femoral trabeculae are closely related to the occurrence and treatment of proximal femoral fractures. Therefore, it is of great significance to study its biomechanical effects of cancellous bone in the proximal femur. This study examines the biomechanical effects of the cancellous bone in the proximal femur using a controlled variable method, which provide a foundation for further research into the mechanical properties of the proximal femur.
Methods
Seventeen proximal femoral specimens were selected to scan by quantitative computed tomography (QCT), and the gray values of nine regions were measure to evaluated bone mineral density (BMD) using Mimics software. Then, an intact femur was fixed simulating unilateral standing position. Vertical compression experiments were then performed again after removing cancellous bone in the femoral head, femoral neck, and intertrochanteric region, and data were recorded. According to the controlled variable method, the femoral head, femoral neck, and intertrochanteric trabeculae were sequentially removed based on the axial loading of the intact femur, and the displacement and strain changes of the femur samples under axial loading were recorded. Gom software was used to measure and record displacement and strain maps of the femoral surface.
Results
There was a statistically significant difference in anteroposterior displacement of cancellous bone destruction in the proximal femur (p < 0.001). Proximal femoral bone mass explained 77.5% of the strength variation, in addition proximal femoral strength was mainly affected by bone mass at the level of the upper outer, lower inner, lower greater trochanter, and lesser trochanter of the femoral head. The normal stress conduction of the proximal femur was destroyed after removing cancellous bone, the stress was concentrated in the femoral head and lateral femoral neck, and the femoral head showed a tendency to subside after destroying cancellous bone.
Conclusion
The trabecular removal significantly altered the strain distribution and biomechanical strength of the proximal femur, demonstrating an important role in supporting and transforming bending moment under the vertical load. In addition, the strength of the proximal femur mainly depends on the bone density of the femoral head and intertrochanteric region.
Keywords: Biomechanics, Bone density, Cancellous bone, Proximal femur
This figure shows the biomechanical effects (strain and displacement changes) of the cancellous bone in the proximal femur using a controlled variable method and analyzes the association between the strength and bone mass of the proximal femur.
Introduction
Proximal femoral fractures have gradually become an important disease affecting the quality of life and life expectancy of the elderly. 1 , 2 According to statistics, the incidence of hip fracture is 0.05%–0.44%, 3 which affects 18% of elderly women and 6% of elderly men worldwide. 4 , 5 However, the unique physiological structure of the proximal femur, which results in the inconsistence of the femoral anatomy axis and the mechanical axis, as well as the peculiarities of the proximal femoral blood supply, make it extremely challenging for fracture healing and will place a heavy burden on society. 6 Therefore, it is necessary to investigate the biomechanical properties of cancellous bone in the proximal femur.
In the proximal femur, primary compression trabeculae, primary tension trabeculae, secondary compression trabeculae, secondary tension trabeculae, and calcar bone form a unique triangular structure. Proximal femoral trabeculae play an important role in the occurrence and treatment of proximal femoral fractures. It has been reported that proximal femoral fractures often begin with the rupture of a small number of proximal femoral trabeculae, and the junction of the trabeculae is often the site of proximal femoral fractures. 7 , 8 In addition, the strength of compression and tension trabeculae are key factors in determining the stability of intertrochanteric fractures, which is closely related to fixation failure. 9 And, some studies have suggested that the difficulty of principal tension and pressure trabecular reconstruction after fracture can increase the risk of postoperative nonunion and osteonecrosis of the femoral head. 10 Although the anatomical structure of the proximal femoral trabecular bone has been analyzed in detail, the mechanical role of the proximal femoral trabecular bone remains controversial. 11 Holzer et al.'s study found no statistical difference in strength of the femoral specimen after removal of cancellous bone of the femoral neck. 12 Moreover, bone mineral density (BMD) was the gold standard for evaluating hip osteoporosis, but it is unclear whether bone mass of a specific trabecula in the proximal femur is crucial for assessing bone strength.
In summary, this study included femoral samples to describe the biomechanical effects of different trabecular group removals on the proximal femur is biomechanics by the controlled variable method, and to analyze the relationship between trabecular bone mass and proximal femoral strength at different sites. Therefore, this study aimed to: (i) indirectly demonstrate the contribution of proximal femoral cancellous bone to the overall bone stiffness and strength by the control variable method; (ii) elaborate the relationship between BMD in each region of the proximal femur and proximal femoral stiffness; and (iii) more clearly investigate the relationship between biomechanics of trabeculae with the occurrence and treatment of hip fracture.
Materials and Methods
Specimen Selection and Test Equipment
Ten pairs of male femur specimens preserved with formalin were selected. The mean age of the donor was 56.1 ± 6.3 years (47–64 years). X‐ray examination was performed to rule out bone abnormalities such as tumor, severe osteoporosis, and deformity. Soft tissues such as femoral skin, muscle and periosteum were removed and truncated at the mid‐shaft of the femur 25 cm from the femoral head. They were wrapped in polyethylene film and kept at −20°C and ablated at room temperature 12 h before the experiment. The main equipment used in this study included Bose Electroforce 3520‐AT Biomechanical Experimental Machine (Bose, Framingham, MA, USA), ARAMIS 3D Camera Systems (Gom, Braunschweig, Germany). This study was approved by the Ethics Committee of Hebei Medical University Third Hospital (2015‐003‐1).
Bone Mineral Density Measurement
The CT data of all specimens were scanned before the experiment, and then the data were saved as Dicom format, and then the gray values of four regions of the specimen femoral head, two regions of the femoral neck, and three regions between the trochanters (gray values represent bone mineral density) were measured using Mimics software. The area size of selected areas keeps equal, and nine areas were selected in the coronal plane for measurement (Figure 1). Measurements were taken every 4 mm and then averaged.
FIGURE 1.
Schematic diagram of the location selected for measuring the gray value of the proximal femur. (A)–(D) The four selected areas in femoral head; (E) and (F) The two selected areas in femoral neck; (G) and (H) The two selected areas in greater trochanter; (I) The one selected area in femoral calcar.
Specimen Assembled to Biomechanical Testing Machine
With the software 3D optical deformation measurement system ARAMIS (Gom, Braunschweig, Germany) and its supporting software analysis (Gom Correlate Pro, Braunschweig, Germany), the entire process of stress deformation of the proximal femur was recorded by the ARAMIS 3D camera during the vertical load test. First, grind the surface of test sample with sandpaper, clean with ethanol and acetone, wait for natural drying, make painting pretreatment on the surface of normal femoral specimen (Figure 2), so that the optical three‐dimensional deformation tracking measurement system can identify the mark point on its surface, and then fix the specimen on the biomechanical tester through a 7° inclination angle within the fixture (simulating unilateral standing position) (Figure 2). After natural drying, apply painting pretreatment to the surface of a normal femoral specimen (refer to Figure 2). This will allow the optical three‐dimensional deformation tracking measurement system to identify the mark point on its surface. Then, fix the specimen on the biomechanical tester through a 7° inclination angle within the fixture.
FIGURE 2.
(A), (B), (C), and (D) are the intact femur model after spraying paint.
Establishment of Trabeculae Removal Model
The surface of proximal femoral specimen was sanded. First, a Kirschner wire was used to perforate the foramen ovale of the femoral head, the lateral femoral cortex, and the tip of the greater trochanter of the proximal femur. The diameter of the hole was maintained at 5 mm. A mill drill bit was used to separately drill holes to remove bone trabeculae to provide access for further treatment. In addition, a special drill was used to gradually remove the bone trabeculae from the posterior to the anterior side to widen the canal. A special curette was used to remove the free bone trabeculae. Furthermore, drill bits of different lengths and diameters were repeatedly selected to remove the trabeculae from the femoral head, greater trochanter, and lateral femoral cortex. Additionally, radiographic film was used to indicate the location of underlying bone trabeculae during removal process, and the remaining bone trabeculae were removed with drill. Finally, all trabeculae removal was performed by one experimenter to ensure consistency of the trabecular bone removal model. The degree and extent of trabecular bone removal was also evaluated by two surgeons to ensure complete removal of trabecular bone (Figure 3 and Supporting Information Figure S1).
FIGURE 3.
Constructing a Proximal Femoral Trabecular Removal Model and corresponding X‐ray image. (A) Perforation of the lateral femoral cortex and imaging images of intact femur. (B) Perforation of the tip of the greater trochanter of the proximal femur and X‐ray image of trabeculae removal from greater and lesser trochanters. (C) Perforation of the fossa ovalis of the femoral head and X‐ray image of trabeculae removal in proximal femur.
Strain and Displacement Measurement and Collection
The weight borne by the hip joint during unilateral lower limb standing is five sixths of the body weight, assuming that the body weight of the study subjects is 72 kg and the weight bearing load during unilateral standing is 600 N. Pre‐load 200 N for 2 min before testing to eliminate elastic creep. The vertical loading of each specimen started at 0 N, increased to 600 N at an acceleration of 10 N/s for 2 min.
The displacement and strain of the specimen were measured and recorded using an optical three‐dimensional deformation tracking measurement system throughout the process, and the above operation was repeated by adjusting the specimen angle (four faces: anterior, posterior, medial, and lateral of the femur). The images were processed in the accompanying software, and the displacement and strain cloud maps of the intact femur and trabeculae removal model were obtained under a load of 600 N (Figure 4).
FIGURE 4.
(A) Specimen Assembled to Biomechanical Testing Machine. (B) and (C) The optical three‐dimensional deformation tracking measurement system was used to record the strain and displacement distribution.
Statistical Analysis
SPSS 25.0 statistical software (IBM, Armonk, NY, USA) was used for statistical analysis. Measurement data were first assessed for normality and homogeneity of variance using the Shapiro–Wilk test and Levene's test. Displacement values before and after specimen failure and did not follow a normal distribution, so the Mann–Whitney test was used. Linear regression analysis was performed on the difference in displacement and gray values in each region of the proximal femur. Differences were considered statistically significant at p < 0.05.
Results
The Relation between the Proximal Femoral Strength and Bone Mass
According to the two‐sample nonparametric test, there was statistical significance in the displacement before and after cancellous bone removal in the proximal femur (p < 0.001; Table S1). In addition, it is worth knowing by analyzing the displacement difference and the gray level of each region of the proximal femur, the proximal femoral bone mass could explain 77.5% of the strength change (Tables S2 and S3). In addition, the proximal femoral strength was mainly affected by the bone mass in the upper outer, lower inner, lower greater trochanter, and level of the lesser trochanter of the femoral head (Tables S2 and S3).
Altered Displacement Distribution Associated with Cancellous Bone Removal
On the anterior side of the femur, the most affected site following destruction of cancellous bone was the femoral head as shown in (Figure 5). Displacement vectors showed a tendency to remove subsidence in the femoral head of intact bone, which was more pronounced after destruction of cancellous bone (Figure 4A). As shown in Figure 5B, the horizontal displacement showed layering characteristics, while the overall characteristics of horizontal displacement did not change significantly before and after failure, but this layering phenomenon showed an upward shift. As shown in Figure 5C, the vertical displacement also showed layering characteristics, and this layering phenomenon almost disappeared after failure. In the posterior aspect of the femur, the most affected site after destruction of cancellous bone was also the femoral head, as shown in (Figure 6). Subsidence was also more pronounced in the femoral head (Figure 6A). As shown in Figure 6B,C, the changes in horizontal and vertical directions were similar to those in the previous direction. There was no significant change in the lateral femoral displacement vector, but there was a layering phenomenon of displacement after cancellous bone failure. We did not observe a significant difference in the anterior–posterior displacement vector of the disrupted cancellous bone in the medial femur (Figures 7 and 8). Size 12 femur presented with a fracture at the last test. We do not believe this affected the final results and therefore we did not exclude this specimen. Video of failures during specimen testing is shown in Attachment 1 (Video S1).
FIGURE 5.
(A1), (B1), and (C1) show the total displacement vector, horizontal displacement and vertical displacement of intact femur under 600 N vertical load, respectively. Under 600 N vertical load, (A2), (B2), and (C2) showed no change of total displacement vector, horizontal displacement and vertical displacement in front and side of cancellous bone model.
FIGURE 6.
(A1), (B1), and (C1) show the changes of the total displacement vector, horizontal displacement, and vertical displacement of the posterior side of the intact femur under 600 N vertical load, respectively. (A2), (B2), and (C2) showed no change of total displacement vector, horizontal displacement and vertical displacement on the rear side of cancellous bone model under 600 N vertical load, respectively.
FIGURE 7.
(A1), (B1), and (C1) show the changes of total displacement vector, horizontal displacement and vertical displacement on the external side of the intact femur under 600 N vertical load, respectively. (A2), (B2), and (C2) showed no change of total displacement vector, horizontal displacement and vertical displacement on the external side of cancellous bone model under 600 N vertical load, respectively.
FIGURE 8.
(A1), (B1), and (C1) show the changes of total displacement vector, horizontal displacement and vertical displacement on the medial side of the intact femur under 600 N vertical load, respectively. Under 600 N vertical load, (A2), (B2), and (C2) showed no change in the total displacement vector, horizontal displacement, and vertical displacement of the cancellous bone model.
Altered Strain Distribution Associated with Cancellous Bone Removal
The strain distribution of intact femur was uniform, and no strain concentration occurred. After cancellous bone destruction, the strain concentration appeared on the lateral femoral neck, and horizontal strain clouds showed that the strain concentration phenomenon here was mainly due to the increase of transverse strain (Figures 9 and 10). While in the medial aspect of the femur the change in strain occurred mainly in the vertical direction (Figure 11). The strain on the lateral surface of the femur did not change significantly before and after failure (Figure 12).
FIGURE 9.
(A1), (B1), and (C1) show the total strain, horizontal strain, and vertical strain cloud images of intact femur under 600 N vertical load, respectively. For (A2), (B2), and (C2), there was no total strain, horizontal strain, and vertical strain cloud image of the cancellous bone model under 600 N vertical load, respectively.
FIGURE 10.
(A1), (B1), and (C1) show the total strain, horizontal strain, and vertical strain cloud images of the intact posterior side of the femur under 600 N vertical load, respectively. The total strain, horizontal strain, and vertical strain cloud maps of the posterior side of cancellous bone model were not obtained under 600 N vertical load for (A2), (B2), and (C2), respectively.
FIGURE 11.
(A1), (B1), and (C1) show the total strain, horizontal strain, and vertical strain cloud images of the intact femur at 600 N vertical load, respectively. For (A2), (B2), and (C2), there were no total strain, horizontal strain, and vertical strain cloud images in the inner side of cancellous bone model under 600 N vertical load, respectively.
FIGURE 12.
(A1), (B1), and (C1) show the total strain, horizontal strain, and vertical strain cloud images of intact femur lateral surface under 600 N vertical load, respectively. The total strain, horizontal strain, and vertical strain cloud maps of the cancellous bone model were not obtained under vertical load of 600 N for (A2), (B2), and (C2), respectively.
Discussion
In this study, the mechanical effect of cancellous bone on the whole proximal femur was analyzed by removing the cancellous bone from the proximal femur and destroying the structural integrity of the trabeculae in the five groups. Based on our study, the removal of cancellous bone affects the strength and strain distribution of proximal femoral which shows an important role in supporting and transforming bending moment for biomechanics of the proximal femur. In addition, the strength of the proximal femur mainly depends on the bone density of the femoral head and intertrochanteric region.
Biomechanical Characteristics of Trabeculae in the Proximal Femur
Our study found the trabecular bone of the proximal femur has unique biomechanical properties. First, the proximal femur shows a decreasing trend in overall stiffness following removal of the cancellous bone. The vector maps indicated an increase in femoral head downward deviation after cancellous bone removal. However, other regions such as the femoral neck and intertrochanteric displacement showed less change. A previous study on a finite element model of an intact femur also found that the femoral head had the greatest displacement under vertical pressure, which is consistent with our findings. 13 There are several possible mechanisms to explain the displacement of the femoral head. First, the femoral head deviates anatomically from the mechanical axis of the femur and forms a neck‐shaft angle, which gives the proximal femur a unique structure. The main trabecular bone that bears pressure begins on the upper side of the femoral head and ends in the calcar like a cone, which supports the femoral head. This structure is destroyed during the destruction process, causing the femoral head to lose support. Second, it is suggested that the primary tension in trabecular bone originates from the bone surface at the lower edge of the greater trochanter of the femur. It then runs anteriorly, superiorly, and medially along the femoral neck FNA, and extends to the femoral head after fusing with the cortical bone in the anterosuperior femoral neck, ending in the inferomedial femoral head. This structure acts as a transverse support to reduce shear stress for the lateral femoral neck cortex. However, the shear stress on the lateral cortex of the femoral neck increased after the structure was damaged.
Furthermore, our study showed that bone density was greatest at the head of the femur, while trabecular bone density was least at the lateral neck of the femur and the greater trochanteric region. A study of the bone mass of the proximal femur showed that cancellous bone at the femoral head has the largest bone volume fraction (BV/TV), with the smallest values located in the lateral femoral neck as well as in the intertrochanteric region, 14 , 15 this is highly similar to our findings, which may explain that the lateral femoral neck and intertrochanteric region are frequent sites of proximal femoral fractures. And, stress concentration appeared on the lateral femoral neck after cancellous bone removal in this study, which is similar to those of Nawathe et al. 16 Finally, in physiological factors, the cortical bone of the femoral head is thin, and even it can be considered that cortical bone has little effect on biomechanical transduction of the femoral head. So, there was a big femoral head subsidence. Our experiments provide an answer to this phenomenon. During this experiment, we performed cortical bone displacement measurement experiments before and after cancellous bone destruction to measure the biomechanical effects of cancellous bone on the proximal femur by means of controlled variables. We measured the trend of displacement in the four planes of the proximal femur by a global domain image acquisition system. After cancellous bone destruction, the most affected part was the femoral head, and interesting layering phenomenon appeared in the displacement clouds of both models, whether the intact femoral model or the cancellous bone model was absent. And this stratification appears only in the horizontal or vertical direction. Stratification in the vertical direction demonstrates that each cross section of the bone is subjected to the same strain.
Relationship between Proximal Femoral Strength and Bone Mass at Different Sites
In clinical practice, osteoporosis is usually diagnosed and treated based on BMD. 17 To personalize the contribution of bone density to bone strength, we used Mimics software to perform a mid‐gray value function for measurement. However, BMD alone cannot accurately predict fracture risk. Many hip fractures arise in people who do not have severely reduced hip bone mineral density. 18 , 19 However, we do not know if bone mass in a region of the proximal femur is critical for bone strength assessment. Accurate assessment of patients' hip fracture risk can therefore identify high‐risk groups and thus take preventive measures. Our study suggests that bone density in the femoral head and intertrochanteric region better reflects bone strength. Similarly, Johannesdottir et al.'s study showed that the femoral neck and intertrochanteric region had the greatest impact on bone strength. 20 In addition, Link et al.'s study showed significant correlations between femoral head, femoral neck (Ward's triangle), and intertrochanteric area and femoral strength. 21 But our study showed that only bone density in the medial superior and lateral inferior femoral head, as well as density in the intertrochanteric region, correlated with bone strength. This may be related to our measurement method, which divided the femoral neck region into two parts when measuring it, and it is possible that the Ward's triangle region was avoided during the measurement, resulting in inconsistent results with Link et al. A study of the relationship between bone mass and bone strength at the proximal end of the femur showed that trabecular bone density in the neck region of the femur contributed more to the bone strength provided by trabecular bone density in the trochanteric region. 23 However, this is contrary to our findings and may be due to the fact that we simulated a standing experiment, whereas this study simulated a lateral femur fall. The greatest compressive stresses and strains during lateral falls occur above the femoral neck, while lower tensile stresses and strains occur below the femur, 22 , 23 with the greatest stresses on the lateral side of the femoral neck and at the same time the initial site of neck fracture. 22 During lateral falls, it is advocated that the force trabeculae are mainly subjected to compressive stresses, which are not consistent with their original function of bearing tensile stresses, which may also be one of the reasons why fractures are likely to occur here.
Lu et al. 24 showed that femoral neck fractures are closely related to degeneration of the trabecular bone by pressure and tension, and intertrochanteric fractures are associated with degeneration of the trabecular bone of the greater trochanter as well as enlargement of the Ward triangle. Therefore, it is known that defects in cancellous bone in the Ward's triangle region have a greater impact on bone strength. 9
Association between Biomechanics of Trabeculae with the Occurrence and Treatment of Hip Fracture
Cancellous bone bears 40% to 70% of the body load in the proximal femur. 25 In an experimental study, researchers demonstrated that approximately 1.5%–6.4% of trabeculae first fractured during fracture, followed by destruction of the entire cancellous reticular formation, and finally cortical bone fracture. Cancellous bone has a strong energy absorption effect, in the normal human body, slight violence or short duration of violence does not lead to the occurrence of fractures, which is because the occurrence of cancellous bone microfractures provides a way for energy release. This phenomenon showed no fracture on X‐ray and CT examination, while MRI showed bone marrow edema and bone contusion. 26 During violent loading, cancellous bone resorbed energy gradually increased, and microdamage to trabeculae gradually accumulated, releasing energy. However, energy accumulates faster when bones are subjected to high‐energy violence, while cancellous bone has a limited ability to carry violence, resulting in fractures.
The trabeculae of the proximal femur constitute a truss system, and when the human body stands normally, the proximal femur is subjected to an axial force conducted along the femoral neck, which decomposes this force into a horizontal outward force and a vertical downward force. When the force is transmitted to the truss system, the force in the vertical direction is mainly borne by the main compression trabecular bone, and the lower trabecular elastic modulus is higher among the main compression trabeculae, and its lower third ultimate strength is the highest. 10 And, each trabecula rod in the main tension trabeculae is regarded as a transverse rod. When the transverse rod bears shear stress, it will produce convex surface on one side of the transverse rod and concave surface on the other side. The trabecula on the convex surface will produce tensile stress, and the trabecula on the concave surface of the transverse rod will produce compressive stress. The same trabecular rod bears both tensile stress and compressive stress. Ma et al.10 found that although the tensile elastic modulus in the force direction was higher than that in the compression elastic modulus, the difference was not statistically significant, 19 indicating that the biomechanical properties of the main tension trabeculae were complex. Studies have shown that the thickness of advocated main tension trabeculae decreases significantly with increasing age, but the thickness of main compression trabeculae does not change significantly with increasing age. 27 In addition, the main tension bone trabeculae take significantly longer to appear as well as to mature than the main compression trabeculae in young children. 28 This is because osteocytes are more vulnerable to compressive stresses, generating an inhibitory signal that is transmitted to osteoclasts through cell processes to prevent bone resorption. 29 Therefore, some scholars have suggested that the difficulty of reconstructing the main compression trabeculae is the most important mechanism for the postoperative complications. Based on the anatomical and structural characteristics of the proximal femoral trabeculae, different scholars have proposed different concepts of hip fracture treatment to reduce postoperative complications. Ding et al. proposed the concept of triangular support internal fixation based on the structural characteristics of the main compression and tension trabeculae, and developed the proximal femoral bionic intramedullary nails (PFBN). 30 , 31 Compared with the commonly used internal fixation, the stability and stress distribution of PFBN fixation of femoral neck fracture and intertrochanteric fracture are significantly improved. 32 , 33 In addition, Ding et al. 13 Chen et al. 13 , 34 proposed the design concept of bionic internal fixation based on the blockage of trabecular reconstruction by traditional internal fixation, and developed bionic cannulated screws and gamma nails. When bionic internal fixation is used to treat hip fractures, it promotes trabecular reconstruction and improves the biomechanical characteristics such as force concentration in the proximal femur and stress shielding of internal fixation. The above internal fixations improve the biomechanical characteristics of proximal femur fracture based on the biomechanical characteristics and anatomy structure of bone trabeculae.
Limitations and Prospect of Clinical Application
There are still some shortcomings in this study. First, the sample size of this study is small, and we will continue to increase the sample size to improve the accuracy of the experiment in the future. Second, bone density is not directly measured during this study, but is reflected laterally by measuring gray values, and there may be errors in the measurement. Finally, when cancellous bone is removed, it is impossible to evaluate whether the removal is up to standard with objective indicators, which may lead to errors in the experiment.
Through this study, we confirmed the important mechanical role of the proximal cancellous bone, which provided a basis for the subsequent study of the biomechanical properties of the proximal femur, and a theoretical basis for the new design of internal fixation of the proximal femoral fracture. It also provides a theoretical basis for the placement and orientation of internal fixators for femoral neck fractures and intertrochanteric fractures. In addition, this study suggests the BMD of localized trabeculae in different areas can significantly affect the biomechanical strength of the proximal femur, and demonstrates that utilizing hip CT data of the femoral head and intertrochanteric bone mass is a crucial factor in predicting osteoporosis in the proximal femur. Furthermore, this study highlights the biomechanical properties of the proximal femoral trabeculae, providing a new reference for the occurrence and treatment of proximal femoral fractures. In the future, we will conduct more detailed mechanical test experiments for different cancellous bone defect sites to further determine the specific biomechanical effects of cancellous bone in various regions of the proximal femur. According to the results of this experiment, we will improve the existing proximal femoral fixation.
Conclusion
In summary, cancellous bone translates the proximal femoral bending moment and transmits body loads uniformly to the proximal femoral cortex, which plays a crucial role in mechanical transduction of proximal femur. In addition, the strength of the proximal femur depends primarily on the BMD of femoral head and intertrochanteric trabeculae. Therefore, these findings illustrate the important biomechanical properties of the proximal femoral trabeculae and suggest that extra attention should be paid to trabecular reconstruction in proximal femoral fractures.
Author Contributions
WC and QZ designed the study. WC, CR, and YZ searched relevant studies. HW, YZ, and HH analyzed and interpreted the data. HW wrote the manuscript. WC, HW, and KD contributed most in the revision of this manuscript. All authors approved the final version of the manuscript.
Conflict of Interest Statement
All authors have read and contributed to the submitted manuscript and have no conflict of interest to declare.
Ethics Statement
This study was approved by the ethics committee of the Third Hospital of Hebei Medical University. Informed consent was obtained from all the participants.
Supporting information
FIGURE S1. Fabrication of specific structural Kirschner pins and selection of specific grinding drill bits for removal of proximal femoral trabeculae.
TABLE S1. Anterior–posterior displacement values for proximal femoral failure.
TABLE S2. Measured gray values for each proximal femur.
TABLE S3. Linear regression analysis of displacement difference and gray values in various regions of proximal femur.
VIDEO S1. Displacement imaging of the fractured femur specimen in biomechanical testing.
Acknowledgments
We thank Dr. Wei Chen for his technical guidance and support of the Biomechanical Experiment. This study was supported by the Hebei National Science Foundation‐Outstanding Youth Foundation (Grant No. H2021206329, H2022206387) and the Support Program for the National Natural Science Foundation of China (Grant No. 82072447, 82272578). The funding source has no role in study design, conduction, data collection, or statistical analysis.
Haicheng Wang, Kai Ding, and Yifan Zhang are co‐first authors.
Qi Zhang and Wei Chen are corresponding authors.
Contributor Information
Qi Zhang, Email: drzhangqi1@163.com.
Wei Chen, Email: drchenwei1@163.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
FIGURE S1. Fabrication of specific structural Kirschner pins and selection of specific grinding drill bits for removal of proximal femoral trabeculae.
TABLE S1. Anterior–posterior displacement values for proximal femoral failure.
TABLE S2. Measured gray values for each proximal femur.
TABLE S3. Linear regression analysis of displacement difference and gray values in various regions of proximal femur.
VIDEO S1. Displacement imaging of the fractured femur specimen in biomechanical testing.