Effectiveness of the surgical torque limiter: a model comparing drill- and hand-based screw insertion into locking plates

Abstract

BackgroundThe objective of this study is to analyse the effectiveness of the surgical torque limiter during operative use. The study also investigates the potential differences in torque between hand and drill-based screw insertion into locking plates using a standardised torque limiter.MethodsTorque for both hand and power screw insertion was measured through a load cell, registering 6.66 points per second. This was performed in a controlled environment using synthetic bone, a locking plate and locking screws to simulate plate fixation. Screws were inserted by hand and by drill with torque values measured.ResultsThe surgical torque limiter (1.5 Nm) was effective as the highest recorded reading in the study was 1.409 Nm. Comparatively, there is a statistically significant difference between screw insertion methods. Torque produced for manually driven screw insertion into locking plates was 1.289 Nm (95 % CI 1.269–1.308) with drill-powered screw insertion at 0.740 Nm (95 % CI 0.723–0.757).ConclusionsThe surgical torque limiter proved to be effective as per product specifications. Screws inserted under power produce significantly less torque when compared to manual insertion by hand. This is likely related to the mechanism of the torque limiter when being used at higher speeds for which it was designed. We conclude that screws may be inserted using power to the plate with the addition of a torque limiter. It is recommended that all screws inserted by drill be hand tightened to achieve adequate torque values.

Biomechanical Investigation of Bone Screw Head Design for Extracting Stripped Screw Heads: Integration of Mechanical Tests and Finite Element Analyses

“…For example, for 3.5 mm nominal thread diameter cortical screws, the minimum breaking torque is estimated at 2300 N•mm. Similarly, for 4.0 mm nominal threaded diameter cancellous screws, the minimum breaking torque is 1300 N•mm, while for 3.5 mm nominal threaded diameter locking screws, it is 1500 N•mm [31]. The FE simulations in this study showed that the maximum torque to failure for some cases was lower than the standard values specified by ISO 6475 (Figure 4).…”

“…In accordance with ISO 6475, the minimum breaking torque values are established for different types of screws based on the nominal thread diameter [31]. For example, for 3.5 mm nominal thread diameter cortical screws, the minimum breaking torque is estimated at 2300 N•mm.…”

Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

“…During the internal fixation procedures, after all implants had been placed, the screws need to be tightened at the end of the procedure to ensure primary stability has been achieved. Several studies have shown a difference between the torque exhibited by different surgeons ( 39 , 40 ). However, insertional torque in locking plates is related to the screw and plate interface and satisfactory torque is achieved when the screw head fully engages the plate and can no longer be advanced.…”

Model-based bone material property identification

“…This approach is effective at preventing overtightening but does little to ensure a minimum torque. Torque-limiting devices exist for some cases [9], especially in orthodontics, which uses small screws with low torque values [10], but these still require the surgeon to know and select the correct torque or limiter manually, in contrast to the proposed automatic model-based method.…”