1 Scope

This standard specifies the test method for testing the fracture torque and fracture torsion angle of metal bone screws used in surgical procedures. The mechanical performance requirements for bone screws are specified in Appendix A

Note 1: The current data only applies to bone screws made of stainless steel material according to ISO 5832-1 and conforming to the dimensions specified in ISO 5835. When other materials and/or bone screw data that meet other standard sizes are obtained, these data will be added to the new appendix.

Note 2: For the interrelationships between international standards for bone plates, bone screws, and related tools, please refer to Appendix B

2 Normative References

The clauses in the following documents become clauses of this standard by reference. Any referenced document marked with a date shall not be subject to any subsequent revisions (excluding errata) or revisions to this standard. However, parties to agreements based on this standard are encouraged to explore the possibility of using versions of these documents. Any referenced document without a date shall be subject to the version specified in this standard.

ISO 5832-1 Surgical Implants - Metallic Materials - Part 1: Forged Stainless Steel

ISO 5835 Surgical Implant Hexagonal Transmission Connection Spherical Lower Surface, Asymmetric Thread Metal Bone Screw Dimensions

3 Experimental methods

3.1 Equipment

Testing equipment with the following characteristics should be used:

a) The maximum sensitivity on the measuring range shall not be less than 0.01N. m or equivalent, and the maximum sensitivity on full-scale readings on other measuring ranges shall not be less than 1%;

b) Range selection (see 3.) 2.4);

c) Can record the maximum torque achieved during the experiment;

d) Equipped with a device to prevent screws from falling off the torque applying component.

Note: The testing equipment must comply with the requirements specified by the national testing institution.

3.2 Program

3.2.1 Insert the bone screw into the jaws of the device and lock it so that it meets the following conditions:

a) When possible, there should be 5 complete exposed threads at the end of the thread;

Note: Starting from the clamping position at the end of the thread, there are 5 complete threads exposed towards the head of the screw.

b) The clamping part shall not be loose;

e) The axis of the screw should coincide with the axis of the torque applying element.

3.2.2 Select a constant angular velocity within the range of 1r/min~5r/min and continuously apply torque to the screw head until the screw fractures.

3.2.3 Record the maximum fracture torque and fracture torsion angle

If the recorded maximum breaking torque is less than 20% of the full-scale reading of the test, the result should be ignored and the above test should be repeated at a lower range.

Note: When tested using an electronic torsion tester, the results should be valid within the measurement accuracy range of the instrument.

Instrument selection: PBSC-TTM20 bone screw torsion performance tester

Product Introduction

The Puchuang microcomputer controlled torsion testing machine is composed of a loading system, a transmission system, a digital data acquisition and processing system, and a computer measurement control display system. It is suitable for testing the static torsional mechanical performance of metal materials, non-metal materials, as well as screws, bone screws, steel pipes, aviation plugs, shafts, bimetallic material components, and joints. The machine adopts a horizontal structure, computer screen display, and FTS precision testing system composition. Adopting a reducer transmission, it has the characteristics of uniform loading, stability, no impact phenomenon, and accurate data acquisition and control.

Product features

Windows7、 8 Chinese operating platform, realizing multiple controls of torque, torsion angle, and deformation. Using a window based operating system with a graphical interface, the display screen and operation panel can be configured;

Can set test speed and various control parameters;

Real time display of torque, in torque, out torque, minimum fracture torque, maximum torque, torsional strength, minimum fracture torsion angle, and torsional speed;

Real time display of various relevant parameter graphics during the experimental process; Can achieve system diagnosis and display diagnostic results

Product Parameters

量程 0.2～20 N.m（50N.m）

Accuracy level 1

Moving distance between clamps 0-200mm

The relative error of the test torque indication is better than ± 1% of the indication

Torque resolution 0.01N. m

The measurement range of torsion angle is infinite

Twisting speed 0.2 ° -720 °/min, stepless speed regulation

Within ± 1% of the set value for relative error of torsional speed

Power supply AC220V 50Hz 0.4kw

Twist direction: forward, reverse