Digital Torque Instrument

With the submission of the final report on 28.02.2023, we have completed the joint R&D project with Furtwangen University, AG Prof. Dr. Möller, on the digital torque instrument. Here is a deep dive into the advantages of a digital torque instrument.

Torque instruments are used to tighten screws in a controlled manner. Orthopedic implants are fixed to the bone and to each other with the help of screws. In order to insert the implant or the implant construction correctly, an optimal torque must be met within narrow limits. For this purpose, there are torque instruments that are customised to the implants.

Conventional solutions

The conventional torque instruments work mechanically, often with a release mechanism to prevent the permissible torque being exceeded. The disadvantage of these instruments is that they are difficult to calibrate and the set release value may shift over time. In addition, there are situations in which a controlled exceeding of the set maximum torque may be objectively indicated or a screw has to be temporarily loosened again, which is prevented by the release mechanism. In addition, users complain that these instruments do not allow “hand feeling” when tightening due to the interrupted shaft.

Kammerer Medical Group manufactures mechanical torque instruments without release mechanism. With these instruments, measuring accuracy is much better and thanks to the continuous shaft, they also allow the hand feeling when tightening the screws. However, the current torque has to be read on a (side) scale and when the target torque is reached, the tightening must be stopped. The disadvantage of this solution is that the users have to observe the implant and therefore need a second person to read the scale.

Innovative torque instrument

We have developed a digital torque instrument that solves the disadvantages of existing instruments by digitizing torque monitoring.

First and foremost, the digital torque instrument promises to contribute to patient well-being through precise calibration without measuring drift. Secondly, to achieve the correct torque, users have all the assessment options available to them that are mutually exclusive with previous solutions: their hand feeling, an acoustic and an easily visible LED signal on the instrument when the target torque is approached or reached, as well as a graphic display of the detailed torque progression with numerical values on a screen. Loosening and retightening of individual screws is also possible. Loosening and retightening of individual screws is also possible.

The stored torque sequences automate the documentation and can be uploaded directly to the patient file. They provide the clinics with the evidence that they can use to prove at any time that the screws have been tightened correctly.

Advantages in the course of the operation

Due to the trend towards minimally invasive surgery, more and more frequently the implant is not fully visible. The digital torque instrument can give a warning in the event of unusual torque curves, e. g. due to incorrect positioning of connection elements of the implant, angling of the insertion screw or pinching of tissue.

Due to the possibility of setting a target torque on the digital torque instrument (which can be automated by changing the working end), it can replace several instruments that are currently required. For users, there is also no need to switch between a normal screwdriver and a torque instrument when tightening each individual screw.

The digitalization of the measurement provides the necessary basis for further supporting functions such as the visualization of the rotational state of each individual screw in real time for more detailed error detection and to prevent screws from being forgotten, especially in long-chain scoliosis operations. It also makes it possible to individually adapt the target torque to the bone strength of the patients.