Preparation method of test piece for cortical bone compression mechanics experiment

Abstract

The invention discloses a cortical bone compression mechanics experiment test piece preparation method, which comprises: 1, full bone marking and positioning, which is used for determining the cortical bone distribution position on a backbone and marking a loop line perpendicular to the axis of the backbone in a segmented manner; 2, bone body annular cutting is carried out, wherein the bone is annularly cut along the mark, and it is guaranteed that the central axis of the segmented bone section is kept consistent with the original femur; 3, annular end face marking is conducted, specifically, a cutting area is marked in the circumferential direction of the bone ring, and it is guaranteed that all sections are located on the same circumference during sampling; fourthly, cylindrical coring is conducted, specifically, cutting is conducted one by one through a coring drill bit according to the marked cutting areas, and the rotating speed of the coring drill bit is lower than 200 rpm; and step 5, sample polishing: polishing the end surfaces of the two sides of the cylindrical sample, and reducing the parallelism of the two ends to be less than 0.01 mm. According to the method, the cylindrical cortical bone sample can be effectively prepared, and the axial characteristics of the cortical bone serving as a material can be more accurately reflected.

Description

Technical Field

[0001] The invention belongs to the technical field of biomaterial processing, in particular to a method for preparing a cortical bone compression mechanics experimental specimen. Background Art

[0002] With the development of science and technology, people need to face many complex and changeable impact events such as traffic collisions, fall injuries, explosion impacts, etc. Bones are important parts that bear external damage, and the response characteristics of bones when facing these loads directly determine the severity of the injury. Therefore, studying the mechanical properties of bones not only helps to evaluate the degree of damage to the human body when it is impacted, but also effectively helps to study mechanical substitutes for bones, so as to better conduct mechanical experiments under different strain rates. In orthopedic biomechanics research, the preparation of high-quality cortical bone cylindrical specimens is the basis for compression, tension or fatigue testing. When traditional coring drills rotate at high speed, the heat generated by the friction between bone tissue and the drill bit can easily lead to local temperature increases, which may cause bone protein denaturation, increase microcracks, and even damage the trabecular structure, affecting the mechanical properties of the specimen. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing cortical bone compression mechanics test specimens, adopt a processing method that minimizes the impact on the biological activity of cortical bone, thereby providing more detailed mechanical property information, achieving uniform heat dissipation through a dedicated coring drill bit, reducing thermal damage to bone tissue, and improving the accuracy and success rate of sample preparation.

[0004] The technical solutions for achieving the purpose of the present invention are:

[0005] A method for preparing a cortical bone compression mechanics test specimen, comprising:

[0006] Step 1: Whole bone marking and positioning, which is used to determine the distribution of cortical bone on the backbone and mark out segments of circular lines perpendicular to the backbone axis;

[0007] Step 2: Circular cutting of the bone body, which is used to cut the bone along the marked circular shape to ensure that the central axis of the divided bone segment is consistent with the original femur;

[0008] Step 3: Annular end face marking is used to mark the cutting area circumferentially on the bone ring to ensure that each section is sampled on the same circumference;

[0009] Step 4: Coring the cylinder, using a coring drill to cut the marked cutting area one by one, wherein the coring drill speed is less than 200 rpm;

[0010] Step 5: Sample grinding: grinding the end faces of both sides of the cylindrical sample to reduce the parallelism of the two ends to less than 0.01mm.

[0011] Compared with the prior art, the present invention has the following significant advantages:

[0012] (1) The present invention controls the temperature of the cutting zone below 40°C through the synergistic effect of the internal cooling channel of the drill bit and the through-holes on the outer wall. It can not only remove the waste material from the cutting through the through-holes to prevent it from affecting the cutting process, but also realize heat control during the cutting process, preventing excessively high cutting temperatures from causing the biological activity to decrease or even disappear, thereby improving the success rate of sample preparation.

[0013] (2) The present invention adopts a circumferential positioning method for drilling the specimens, ensuring that the specimens are distributed on the same circumference and that the layered bone plates of each circumferential specimen are similarly distributed, thereby improving the accuracy of specimen preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the preparation process of the femoral cortical bone cylindrical specimen in the present invention

[0015] Figure 2 This is a marked diagram of the end face of the bone ring.

[0016] Figure 3 It is a three-dimensional schematic diagram of the coring drill bit of the present invention. Figure 4 Schematic cross-sectional view of the coring drill bit of the present invention. Figure 5 The following is a comparison chart of the results. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1

[0019] like Figure 1 As shown, a method for preparing a cortical bone compression mechanics test specimen in this embodiment includes: a whole bone marking and positioning step, a bone annular cutting step, an annular end face marking step, a cylindrical coring step, and a specimen polishing step.

[0020] Step 1: Select a fresh, frozen porcine femur, moisten it with saline, and remove any soft tissue. Measure the total length of the femoral shaft, determine the midpoint of the shaft, and use a marker to mark a circular line perpendicular to the femoral axis at this location. Using the midpoint circular line as a reference, move toward each end of the femur, marking a circular line every 10 mm to determine the position of the remaining bone rings along the femoral axis.

[0021] Step 2: If Figure 1As shown, using a cutting machine, precisely cut along the marked lines according to the markings to obtain bone rings at different axial positions. During the cutting process, ensure that the saw is aligned with the marked lines to maintain a uniform thickness of the bone ring. Use saline solution during cutting to ensure that the temperature of the cut surface does not rise too high, which would cause a decrease in its physiological activity. Immediately soak in saline solution after cutting for preservation.

[0022] Step 3: If Figure 2 As shown, a circle with the same radius was marked on the end surface of each bone ring to ensure that the lamellar bone plate distribution of each circular specimen was similar.

[0023] Step 4: If Figure 3 and Figure 4 As shown, the center of the sampling point is required to fall on the circumference of each bone ring. A dedicated coring drill is used for sampling, with a rotation speed of 100 rpm and a feed rate of 0.1 mm / s. The inner diameter of the coring drill is 4 mm. The specific dimension requirement is that the thickness of the cortical bone wall at the cutting point is greater than the selected drill inner diameter. Before drilling, coolant (normal saline, 6°C) is added to the reservoir above the coring drill. The coolant is delivered to the drill bit and the bone processing surface through symmetrical infusion grooves to avoid thermal damage. The drill bit and bone ring are always maintained perpendicular during the drilling process to ensure that the central axis of the specimen remains unchanged. After removing the bone core, it is immediately immersed in normal saline for storage. A cavity is provided in the core drill bit, with a partition 1 in the middle. The partition 1 divides the core drill bit cavity into two cavities, the upper cavity serving as a liquid storage chamber 2, and the lower cavity serving as a cutting chamber 3. A symmetrical liquid tank 4 is provided between the liquid storage chamber 2 and the cutting chamber. The liquid tank 4 is used to drain the liquid in the liquid storage chamber 2 to the cutting head 5 at the bottom of the core drill bit. A chip removal hole 6 is provided at the side end of the cutting chamber 3 for removing debris during the cutting process.

[0024] Step 5: The tail of the specimen processed by the core drill will have bone residue, and it is necessary to use an oil stone with a roughness of P200 to grind the specimen at a speed of 100 rpm under continuous pouring of physiological saline. After removing the tail residue by grinding, the specimen can be placed on the elastic chuck and the end face can be polished by high-speed rotation and an oil stone with a roughness of P800 to ensure that the end face is smooth without concave and convex points, and at the same time reduce the parallelism of the two ends to less than 0.01 mm, and finally the low strain rate (strain rate <1s -1 ) compression specimen size is φ4×8mm, high strain rate (strain rate>100s -1 The compression specimen is φ4 × 4 mm. These dimensions can be adjusted based on the actual cortical bone mechanical testing requirements. After preparation, it must be immediately stored at -20°C and the relevant mechanical testing completed within 24 hours. Obtaining mechanical property information facilitates the preparation of biomimetic specimens.

[0025] Comparative Example 1

[0026] The difference between this embodiment and embodiment 1 is that in step 4: the rotation speed of the coring drill is set to 200 rpm, and the other parameters remain unchanged, and then the strain rate is set to 0.01s -1 Compression experiment.

[0027] Comparative Example 2

[0028] The difference between this embodiment and embodiment 1 is that after obtaining the bone ring of the cortical bone in step 2, the end face of step 5 is directly polished using an oil stone with a roughness of P800, and then the strain rate is 0.01s -1 Compression experiment.

[0029] The results should be compared

[0030] The results are as follows Figure 5 As shown, at the same strain rate of 0.01s -1 Comparing the bone ring specimens with the cylindrical cortical bone specimens drilled at low speed revealed a clear linear growth segment in the low-speed drilled cylindrical cortical bone test, with a smooth rise. After reaching maximum compressive strength, the stress dropped dramatically. This indicates that the cortical bone in the low-speed cylindrical specimens was evenly distributed and had no significant changes in biological properties, maintaining a similar strength to the undrilled cortical bone ring.

[0031] Comparing cylindrical cortical bone specimens drilled at high speed with those drilled at low speed reveals a significant decrease in the maximum compressive strength of the high-speed specimens, and a very gradual decrease in stress after reaching maximum compressive strength. This suggests that a rotation speed of 100 rpm is more effective in ensuring that the mechanical properties of cortical bone are not affected by the machining process.

Claims

1. A method for preparing a cortical bone compression mechanics test specimen, characterized in that: include: Step 1: Whole bone marking and positioning, which is used to determine the distribution of cortical bone on the backbone and mark out segments of circular lines perpendicular to the backbone axis; Step 2: Circular cutting of the bone body, which is used to cut the bone along the marked circular shape to ensure that the central axis of the divided bone segment is consistent with the original femur; Step 3: Annular end face marking is used to mark the cutting area circumferentially on the bone ring to ensure that each section is sampled on the same circumference; Step 4: Coring the cylinder, using a coring drill to cut the marked cutting area one by one, wherein the coring drill speed is less than 200 rpm; Step 5: Sample grinding: grinding the end faces of both sides of the cylindrical sample to reduce the parallelism of the two ends to less than 0.01mm.

2. The method for preparing a cortical bone compression mechanics test specimen according to claim 1, characterized in that: During the whole bone marking and positioning process, the midpoint of the backbone is first determined, and a circular line perpendicular to the bone axis is marked at the midpoint. Using the midpoint circular line as a reference, the line is moved toward both ends of the femur. A circular line is marked every time a set distance is moved to determine the position of other bone rings on the femoral axis.

3. The method for preparing a cortical bone compression mechanics test specimen according to claim 1, characterized in that: During the annular end face marking process, a circle of the same radius is marked on the end face of each bone ring.

4. The method for preparing a cortical bone compression mechanics test specimen according to claim 1, characterized in that: When coring a cylinder, the center of the sampling point is required to fall on the circumference of each bone ring. The thickness of the cortical bone wall at the cutting point is greater than the inner diameter of the selected coring drill bit. Physiological saline is used for cooling during the sampling process. After the bone core is taken out, it is immersed in physiological saline for storage.

5. The method for preparing a cortical bone compression mechanics test specimen according to claim 1 or 4, characterized in that: There is a cavity inside the coring drill bit, with a partition in the middle. The partition divides the coring drill bit cavity into two cavities, the upper cavity serves as a liquid storage chamber, and the lower cavity serves as a cutting chamber. A symmetrical liquid trough is provided between the liquid storage chamber and the cutting chamber. The liquid trough is used to drain the liquid in the liquid storage chamber to the cutting head at the bottom of the coring drill bit. A chip removal hole is provided at the side end of the cutting chamber for removing debris during the cutting process.

6. The method for preparing a cortical bone compression mechanics test specimen according to claim 1, characterized in that: During the sample grinding process, an oil stone with a roughness of P200 was used to grind the sample under continuous pouring of physiological saline. After removing the tail residue, the end face was polished using an oil stone with a roughness of P800.

7. The method for preparing a cortical bone compression mechanics test specimen according to claim 1, characterized in that: During the sample grinding process, the strain rate is <1s -1 The compression specimen size is φ4×8mm, and the strain rate is >100s -1 The compression specimen is φ4×4mm.

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