K-wire Pull-Out Force After Multiple Redirection Attempts

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Materials science

Background:

• Kirschner wires (K-wires) are commonly used in orthopedic fixation.
• Understanding the mechanical integrity of K-wire fixation is crucial for successful surgical outcomes.
• The impact of K-wire redirection on fixation strength requires detailed investigation.

Purpose of the Study:

• To determine if redirecting a K-wire through the same proximal hole weakens its pull-out force.
• To assess if multiple K-wire redirections lead to a progressive decrease in fixation strength.

Main Methods:

• K-wire pull-out force was measured using an Instron testing machine.
• K-wires (0.062 inches) were inserted bicortically into a bone substrate using an angled drill guide.
• Experimental groups involved 0 to 5 redirections through the same proximal hole, plus unicortical and control groups.

Main Results:

• Any K-wire redirection significantly reduced pull-out force compared to the no-redirect control group.
• No significant difference in pull-out force was observed between redirected groups and a unicortical fixation group.
• Regression analysis indicated no stepwise decrease in pull-out force with increasing numbers of redirections beyond the first.

Conclusions:

• K-wire redirection, even once, substantially weakens the fixation construct.
• The pull-out force after any redirection is comparable to that of a unicortically placed wire.
• Surgical techniques should aim to avoid K-wire redirection to maintain construct stability.