Biomechanical evaluation of the Pinless external fixator

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Materials science

Background:

• External fixators are crucial for open fracture stabilization, especially with severe soft tissue damage.
• Classical external pin fixation presents complications like pin track infection and vascular damage.
• The Pinless external fixator was developed to mitigate these issues by minimizing bone penetration.

Purpose of the Study:

• To evaluate the functional performance and safety of the Pinless external fixator.
• To assess the device's ability to maintain stable fracture fixation over time.
• To investigate changes at the trocar-to-bone interface and potential for infection.

Main Methods:

• Mechanical trials and in vitro tests were conducted.
• A pinless clamp was subjected to a controlled load (50 N, 150 cycles/day) for 5 weeks in sheep.
• Simulated temporary, non-weight-bearing fracture stabilization conditions were used.

Main Results:

• The clamp retained 72% of its initial clamping force after 5 weeks, remaining tight upon removal.
• Clamping force decreased initially but stabilized after 20 days.
• No slippage or cortical penetration occurred; no signs of infection or pathological cultures were observed.
• Histology showed localized bone reactions with minimal trocar tip indentation (1.2 mm).

Conclusions:

• The Pinless external fixator demonstrates potential as a safe method for temporary fracture fixation.
• The device effectively maintains fixation stability with a low risk of infection and minimal tissue damage.
• Further clinical validation is warranted to confirm these findings in human patients.