In vitro biomechanical comparison of 3.5 string of pearl plate fixation to 3.5 locking compression plate fixation in a canine fracture gap model.

Objective: To compare the 3.5 string of pearls (SOP) plate with a 3.5 mm locking compression plate (LCP) using a fracture model in static loading and cyclic fatigue testing.

Study Design: In vitro biomechanical testing of paired tibias with a mid-diaphyseal ostectomy, stabilized by 1 of 2 locking systems.

Sample Population: Cadaveric canine tibiae (n = 24 pairs).

Methods: Tibias were randomly divided into 4 equal groups: (1) 4-point bending single cycle to failure, (2) 4-point bending cyclic fatigue, (3) torsion single cycle to failure, and (4) torsion cyclic fatigue. Randomly assigned SOP and LCP bridged a 20 mm mid-diaphyseal ostectomy. Mean test variables values for each method were compared using a paired t-test within each group with significance set at P < .05.

Results: The SOP construct had significantly greater mean yield load, mean yield displacement, mean yield bending moment, mean composite rigidity and mean failure bending moment under static 4-point bending to failure than the LCP construct. Mean number of cycles to failure under 4-point bending was significantly greater for the SOP constructs but the mean number of cycles to failure in torsion was significantly greater for the LCP constructs. The LCP construct had significantly greater mean composite stiffness and significantly lesser mean displacement to yield and to failure in static torsion testing.

Conclusion: The SOP construct was superior under bending static and cycling testing but the LCP construct was superior in static and cycling torsion testing.