Hand-Drilled External Fixator Pins Have Superior Biomechanical Strength Compared to Power-Drilling

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Trauma care

Background:

• Surgeons in austere settings often use manual braces for external fixation pin insertion due to lack of power drills.
• The biomechanical integrity of manually inserted pins is not well-established.
• This study addresses the uncertainty surrounding the performance of manually inserted external fixation pins.

Purpose of the Study:

• To compare the pull-out strength of external fixator pins inserted manually with a brace versus those inserted with a power drill.
• To investigate the biomechanical performance of different pin insertion techniques.

Main Methods:

• Ninety porcine femoral segments were used to test three insertion techniques: hand-drilled, power-drilled, and pre-drilled/power-inserted.
• External fixation pins were inserted by three surgeons, with 30 specimens per technique.
• Pull-out strength to failure was measured using a materials testing machine, analyzed with a generalized linear mixed effects model.

Main Results:

• Drilling technique and diaphyseal pin location significantly predicted pin pull-out strength.
• Contrary to hypothesis, hand-drilled pins exhibited significantly greater pull-out strength (1,542.6 N) than power-drilled (1,344.2 N) and pre-drilled/power-inserted pins (1,248.5 N).
• No significant difference in pull-out strength was found between power-drilled and pre-drilled/power-inserted techniques.

Conclusions:

• Manual insertion of external fixation pins with a hand brace results in superior pull-out strength compared to power tools.
• This challenges the assumption that manual insertion is mechanically inferior.
• Findings support continued training and funding for manual drilling techniques in military and humanitarian settings.