Correlation between the Closest Pin Distance of the Fracture line to the Stability of the External Fixation: A Biomechanical Study on Bovine Tibia

Aims: To determine the effect of the closest pin distance from the fracture line on the stability of the external fixation which is applied axial compression force.

Study Design: This study was an experimental study with a post-test only controlled group design, using bovine tibia.

Place and Duration of Study: This research was conducted in the Orthopedic and Traumatology Department of Dr. Moewardi Hospital and Engineering Laboratory of Sebelas Maret University from June to September 2020.

Methodology: External fixation stability measured using a Universal Testing Machine. There were three treatment groups with different closest pin spacing (2 cm, 3 cm, 4 cm).

Results: This study used 30 bovine tibial bones (10 bones for each treatment group). The closest 2 cm pin distance group has the largest mean value of compressive strength 7036.56 ± 453.37 Newton. Linear regression analysis shows the value of p = 0.000 with a regression coefficient of -912.55. The significant relationship proves the near-far law theory, where the pins are placed as close as possible from the fracture line could give the greater amount of external fixation stability.

Conclusion: Shorter pin distances from the fracture line were associated with increased compressive strength.