Biomechanical comparison of a new staple technique with tension band wiring for transverse patella fractures

Abstract 

Background

The tension band wiring technique is the most common method of transverse patella fracture fixation. Since post-operative instabilities have been reported for this technique, alternative osteosynthesis solutions are of interest. We investigated the biomechanical behaviour of a new staple technique for treatment of transverse patella fractures in a cadaveric model.

Methods

Eight human cadaveric knees with femur and tibia including soft tissue were used. A transverse osteotomy of the patella was created. Each specimen was fixed consecutively with tension band wiring and two Nitinol compression staples. Testing was performed by pull on the quadriceps tendon between a 90° flexed position and full knee extension for up to 5000 cycles.

Findings

At 1000 cycles, fracture site displacements in flexion and extension were significantly smaller for the staple group at the ventral aspect of the patella as compared to the tension band wiring group. With a failure criterion of 2mm fracture site displacement, cycles until failure were significantly smaller for the staple group.

Interpretation

This study provides evidence based on a cadaveric model that compression staples have a promising potential to treat transverse patella fractures.

Keywords: Patella, Tension band, Staple, Fracture, Biomechanics