Biomechanical Comparison of Tibial Nail Stability in a Proximal Third Fracture: Do Screw Quantity and Locked, Interlocking Screws Make a Difference?

Abstract

In this study, proximal segment stability was improved with a greater quantity of screws and with locked interlocking screws.

An in vitro biomechanical investigation of an interlocking nail system developed for buffalo tibia

“…Several earlier studies involving the standard interlocking nail demonstrated construct slack due to less rigid interaction between the locking device and the nail hole (15,17,19,36). The BIN constructs with eight modified locking bolts had significantly higher stiffness, yield load and ultimate failure load than the constructs with eight standard bolts, which could be due to the snug fit of the modified locking bolts within the threaded holes of BIN, thereby reducing the slack in the fixation (21).…”

“…Higher values (approximately 1.5 times) of bending moment, stiffness, yield load and ultimate failure load for constructs with eight standard locking bolts than for constructs with four bolts is in agreement with the findings of previous studies with external skeletal fixation, where three-point fixation per bone segment was found to be more stable and stronger than two-point fixation (35). Similarly, constructs with modified locking bolts were also found significantly stronger than with standard bolts under bending, probably due to more rigid fixation with reduced intrinsic slack in the fixation (21). Earlier studies using an angle-stable locking nail have shown elimination of slack in both medio-lateral and cranio-caudal bending directions, in turn improving the construct stability in a canine tibial model (18,19).…”

“…Investigations with external skeletal fixation have shown that increasing the number of pins distributes the physiological load among the pins and increases the stiffness of the overall construct (35). Likewise, the overall fatigue life and stability of fixation of an interlocking nail used in a human tibial fracture were increased with the increase in number of locking screws (21). Several earlier studies involving the standard interlocking nail demonstrated construct slack due to less rigid interaction between the locking device and the nail hole (15,17,19,36).…”

“…Each bone-BIN construct was prepared as a static fixation, as per the technique used for human interlocking nails, with some modifications (21). The tibia was placed in a support jig for insertion of the nail (▶ Figure 6) and creation of an ostectomy.…”

“…Failure of a proximal bone fragment under compression also indicates that the proximal fragment is likely to be subjected to more axial compression load than the distal fragment in a clinical situation. So by increasing the number and locking quality of bolts in the proximal fragment, the stability and strength of the fixation may be increased, especially against axial compressive force (21).…”