Augmented screwdrivers reduce bone stripping rates and optimize tightness when inserting non-locking screws (TightRight)

Background

Non-locking screws remain the most commonly used orthopedic implants, however they are often poorly inserted. Exceeding the stripping torque for a screw hole reduces pullout strength by more than 80%.

Goal

To quantify stripping rates and screw tightness for orthopedic trauma surgeons and assess how these change when using a screwdriver that indicates when optimum tightness is reached.

Results

At the AO Davos Courses, orthopedic trauma surgeons tightened 20 screws in two phases: (1) screws tightened to the surgeon’s perception of optimum tightness, and (2) using an augmented screwdriver indicating when a predetermined optimum tightness – defined as 70% of the maximum stripping torque – was reached. Within each phase, 10 partially inserted   3.5 mm non-locking cortical screws were tightened through a 3.5 mm plate into 4 mm thick artificial bone analogue. The stopping torque for each screw was recorded and compared to the stripping torque; if the stopping torque greatly exceeded the stripping torque, tightness values higher than 100% were possible.

With a normal screwdriver, stripping rates were high, though varied greatly amongst surgeons. Using an augmented screwdriver greatly improved insertion, with optimum tightness being achieved alongside with a significantly reduced rate of bone stripping.

Fund:

Royal College of Surgeons, UK, GBP 5'000, Period: 2019.