Transarticular versus extraarticular ankle pin fixation: a biomechanical study

Area of Science:

• Orthopedic surgery
• Biomechanics
• Anatomy

Background:

• Transarticular pin fixation for ankle stabilization can lead to ankle joint arthrosis.
• An extraarticular technique may circumvent these drawbacks.
• This study compares fixation stiffness between transarticular and extraarticular methods.

Purpose of the Study:

• To compare the stiffness of transarticular versus extraarticular ankle fixation under minimal dorsiflexion loading.
• To evaluate the potential of extraarticular fixation to avoid complications associated with transarticular methods.

Main Methods:

• Ten matched pairs of cadaveric lower extremity specimens were randomized to transarticular or extraarticular fixation.
• Transarticular fixation involved retrograde axial pins through the plantar heel, calcaneus, subtalar, talar body, and ankle joint.
• Extraarticular fixation used antegrade pins from the distal tibia to the calcaneus and from the tibial metaphysis to the navicular.

Main Results:

• No significant difference in stiffness was observed between the transarticular (17.93 N/mm) and extraarticular (18.61 N/mm) groups.
• The lateral pin in the extraarticular group was an average of 4.2 mm from the flexor hallucis longus (FHL) tendon.
• Extraarticular fixation did not disrupt the ankle or plantar skin.

Conclusions:

• Extraarticular crossed antegrade pin fixation demonstrates comparable stiffness to transarticular fixation.
• This extraarticular technique avoids disruption of the ankle joint and plantar skin.
• Extraarticular ankle fixation presents a viable alternative to mitigate complications associated with transarticular fixation.