When treating a bone fracture, bone fragments are typically aligned in a first step. The aligned bone fragments may then be fixed by a bone plate having multiple through openings. Bone screws are screwed through the bone plate openings into the bone fragments using a surgical powertool driving a screw driver blade.
To prevent damage of bone screws or similar implants and the screw driver blade, a powertool with a torque-limiting function may be used. The torque-limiting function may be realized mechanically or electronically. Conventional powertools with an electronic torque-limiter often exceed the set target torque. Such torque overshooting is highly undesirable when screwing a bone screw into bone since the bone screw, the bone or the powertool may be damaged. Also mechanical torque-limiters have such drawbacks.
A torque-limiting function may be integrated as an assembly with the powertool or implemented as a separate, dedicated torque-limiter. When using the latter, the surgical procedure is complicated by additional steps: engaging the first few threads by hand or with a screwdriver, inserting the screw further with the powertool until only a few threads are remaining and final tightening by hand, using the dedicated torque-limiter.
Additionally, due to the fact that different bone screws may be dimensioned for different torques, a surgical procedure with conventional torque-limiting powertools is time consuming since the surgeon needs to manually adjust the target torque for each bone screw. Moreover, a surgical procedure using a powertool with a conventional target torque setting is vulnerable to the human factor and a bone screw may be tightened with a wrongly designated torque.