The internal fixation of fractures in bone with the aid of plates and screws is a common
procedure in orthopaedic surgery. The prevention of over-tightening is entirely dependent
upon the skill and judgement of the surgeon.
The research reported here proposed two independent methods for the prevention of overtightening
of orthopaedic screws.
The first method developed by this research was a mathematical model for predicting the
maximum torque that may be applied to a screw before over-tightening occurs. Use of the
model would allow surgeons to set a torque-limiting device to prevent over-tightening
during surgery. The model would also allow the surgeon to predict the maximum pullout
force that screwlbone interface can withstand before failure occurs.
The second method developed in this research to prevent over-tightening was the
automated screwdriver. It was shown that the automated screwdriver could detect the
onset of tightening thus preventing over-tightening without the aid of the mathematical
model. The automated screwdriver was demonstrated to perform the following tasks:-
(ii) Tightening of non-self-tapping and self-tapping screws.
(iii) Insertion of self-drilling external screws.
This research has conclusively demonstrated that both the proposed methods for the
prevention of over-tightening orthopaedic screws are a contribution to orthopaedic
The Author recommends that the mathematical model and the automated screwdriver are
both further developed to prevent over-tightening and increase the speed and safety of
screw insertion in surgery.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University