Abstract
Purpose
To compare the fixation strength and loads on insertion of a titanium alloy interference screw with a modified tip against a conventional titanium interference screw.
Methods
Slippage of bovine digital extensor tendons (as substitutes for human tendon grafts) under cyclic loading and interference fixation strength under a pullout test were recorded in 10 cadaveric knees, with 2 tunnels drilled in each femur and tibia to provide pair‐wise comparisons between the modified‐tip screw (MS) and conventional screw (CS). To analyze screw insertion, 10 surgeons blindly inserted pairs of the MS and CS into bone‐substitute blocks (with polyester shoelaces as graft substitutes), with insertion loads measured using a force/torque sensor.
Results
No differences were found between the MS and CS either in graft slippage from the femur (
P
= .661) or tibia (
P
= .950) or in ultimate load to failure from the femur (
P
= .952) or tibia (
P
= .126). On insertion, the MS required less axial force application (78 ± 38 N,
P
= .001) and fewer attempted turns (2 ± 1,
P
Conclusions
The MS was found to be easier to engage with the bone tunnel and initially insert than the CS while still achieving similar immediate postsurgical fixation strength.
Clinical Relevance
The study shows that screw designs can be improved to ease insertion into a bone tunnel, which should reduce any likelihood of ligament reconstruction graft damage.