YY/T 0346-2022Implants for osteosynthesis-Metallic fixation screw for femur neck (English PDF)

3.1 Metallic fixation screw for femur neck

An implant that is made of metallic materials, used alone or in conjunction with other implants (such as angle fixers, intramedullary nails, and internal fixation plates) during femur neck fracture surgery, and implanted in the femur neck.

3.2 Axial insert strength

The maximum pressure required to fully insert the working part of the femur neck screw, which is implanted into the human body by percussion (see Figure C.1 in Appendix C), into the test block, and the unit is Newton (N).

4.1 Materials

Femur neck screws shall be preferably made of surgical implant materials specified by international standards, national standards, and industry standards.

Note: This item is only applicable to self-tapping femur neck screws implanted into the human body by screwing in.

4.2.7 Static compression bending performance

The manufacturer shall specify the compression bending strength and compression bending stiffness of femur neck screws.

4.2.8 Fatigue compression bending performance

The manufacturer shall specify the fatigue compression bending performance of femur neck screws.

4.3 Corrosion resistance

The pitting potential (Eb) of the stainless-steel femur neck screw shall not be less than 800 mV.

4.4 Surface quality

4.4.1 Surface defects

The surface of the femur neck screw must have no discontinuities.

4.4.2 Surface roughness

The manufacturer shall specify the requirements for the surface roughness (Ra) value according to the product design characteristics.

4.4.3 Appearance

The surface of the femur neck screw shall be free from defects such as oxide scale, knife marks, small notches, scratches, cracks, depressions, sharp edges (except cutting edges), burrs, and shall also be free from inlays, final processing deposits, and other pollutants.

4.4.4 Anodic oxidation surface treatment

After anodic oxidation surface treatment, femur neck screws shall at least be conducted a qualitative analysis of surface elements and evaluation of cytotoxicity.

4.5 Dimensions

The manufacturer shall specify the dimensions and tolerances of the product according to the product design characteristics.

4.6 Coordination performance

Where the femur neck screw has a connection, the coordination performance shall be good, and there must be no looseness or jamming.

5.1 Materials

The chemical composition and microstructure shall be sampled on the final product, and inspected according to the method specified in the selected material standard or the method in the standard recommended in Appendix A.

5.2 Mechanical properties

5.2.1 Maximum torque and breaking angle

The test shall be carried out according to the method of YY/T 0662 and the instructions in Appendix B. If an electronic torsion testing machine is used for the torsion test, the range shall be selected to ensure that the recorded maximum torque and breaking angle are within the effective range of the testing machine. If possible, counting from the thread close to the screw head, there shall be 5 complete threads exposed; if less than 5 threads are completely exposed, it shall be indicated in the report. It is recommended to use a fixed angular velocity of 3 r/min, rotate the femur neck screw in the direction of insertion until the femur neck screw breaks, and record the maximum torque and breaking angle. The samples shall not be less than 5 pieces.

5.2.2 Hardness

The test shall be carried out according to the method specified in GB/T 4340.1, and the number of samples shall not be less than 3 pieces.

5.2.3 Axial insert strength

The test shall be carried out according to the method specified in Appendix C, and the number of samples shall not be less than 3 pieces.

Note: The test method in Appendix C is not the only method for measuring the axial insert strength of the femur neck screw, and the enterprise can also formulate the test method by itself according to the product design characteristics.

5.2.4 Axial pullout strength

The femur neck screw implanted into the human body by screwing-in shall be tested in accordance with the method specified in YY/T 1504. The femur neck screw implanted into the human body by percussion can be subjected to the axial pullout strength test with reference to the method specified in YY/T 1504 after the test in 5.2.3. The number samples shall not be less than 3 pieces.

5.4.3 Appearance

It shall be inspected by normal or corrected vision, and the number of samples shall not be less than 3 pieces.

5.4.4 Anodic oxidation surface treatment

Qualitative analysis of surface elements shall be carried out by using a scanning electron microscope and energy-dispersive spectrometer, and the cytotoxicity shall be tested in accordance with the provisions of GB/T 16886.5.

5.5 Dimensions

The dimensions shall be measured with general measuring tools or special measuring tools, and the number of samples shall not be less than 3 pieces.

5.6 Coordination performance

The test shall be carried out by imitating the working situation, and the number of samples shall not be less than 3 pieces.

9.1 Labeling

It shall comply with the provisions of YY/T 0640.

9.2 Marking

It shall comply with the provisions of YY/T 0640.

C.1 Overview

This test method specifies the test method for measuring the axial insert strength of the femur neck screw. The femur neck screw is installed in the loading device, and the testing machine applies a compressive load to fully insert the working part of the femur neck screw (as shown in Figure C.1) into the test block; the maximum pressure is the axial insert strength.

The purpose of this test method is to provide a test method for measuring the axial insert strength of femur neck screws, so as to compare femur neck screws of different types, materials, designs, processes, and surface treatments. The result obtained by this test method is not equivalent to the force value required by the femur neck screw when it is knocked into the human body.

C.2 Test device

The test device used to determine the axial insert strength of the femur neck screw is shown in Figure C.2. The test device shall include a test block made of materials conforming to ASTM F1839, a fixture, and a loading device. At the same time, the test block fixture and loading device shall have sufficient stiffness so that the deformation under the required loading conditions can be ignored.

a) Test block The test block shall preferably be made of polyurethane foam conforming to ASTM F1839. The upper and lower surfaces of the test block shall be flat, smooth, and parallel to each other (the deviation shall be within the range of ±0.4 mm) to ensure that when it is fixed in the fixture, its upper surface is perpendicular to the centerline of the femur neck screw. The test block shall be square or other shapes that can ensure that there is no relative movement and deformation of the test block during clamping or testing. The thickness of the test block shall be at least 10 mm greater than the length of the working part of the femur neck screw, and the distance from the edge of the insertion position to the edge of the test block shall be at least 1.5 times the diameter of the femur neck screw.

b) Loading device It is a device used to apply a compressive load to the femur neck screw, the load

D.1 Overview

The femur neck is located at the proximal end of the femur, which bears the weight of the upper body of the human body, transmits the elements of human mechanics from top to bottom, and maintains the biomechanical functions of the lower limbs. The femur neck screws implanted in the femur neck are subjected to compressive bending loads in the human body, which is the most common type of loading in the human body.

The purpose of this test method is to provide a test method for measuring the compression bending performance of femur neck screws, which can be used for comparison between femur neck screws of different types, materials, designs, processes, and surface treatments, so as to provide more useful information for the evaluation on the safety and practicality of the products. The results are not suitable as the basis for predicting the use of the product in the human body.

D.2 Test methods and procedures for the static compression bending performance of femur neck screws D.2.1 Rigidly fix the head end of the femur neck screw on the testing machine, as shown in Figure D.1. The fixed end shall be strong enough and shall not be loose during the test. In principle, the loading moment arm L shall not be lower than 1/2 of the full length of the femur neck screw. The femur neck screw forms an angle alpha with the horizontal direction (in general, alpha is recommended to be 45°±1°), and a vertical downward load is applied to the tail end of the femur neck screw. The loading device shall be able to eliminate the side load during the compression bending process.