Text

Objectives and questions: Minimally invasive treatment of clavicle fracture has become increasingly popular due to reduced soft tissue damage, smaller incisions, low rates of infections and minimal scarring. Most commonly described options for minimally invasive fixation are titanium elastic nailing and plate osteosynthesis. Implant removal after a few months is standardly carried out, leading to a second surgery with corresponding risks and costs. Furthermore, biomechanical studies show a low rotational stability for this implant. There have been some suggestions for improvement of the implant. The aim of this study was to test the biomechanical values of new strategies for minimally invasive fixation of the clavicle in comparison to the titanium elastic nail.

Material and methods: Twelve anatomical composite clavicles with standardized oblique midshaft fractures (AO/OTA 15.2A) were allocated to two groups: fixation with a 2.5 mm titanium elastic nail (TEN) or a 5.0 mm rib splint (RS). Each specimen underwent a standardized testing protocol consisting of quasi-static non-destructive bending tests in anterior–posterior and superior–inferior directions, followed by cyclic loading and progressive cyclic loading to catastrophic failure. Axial load, displacement, stiffness, and rotational torque were analyzed for both test setups. Interfragmentary motion during cyclic loading was assessed using a high-resolution optical motion capture system (ARAMIS).

Results: In the quasi-static bending tests, the rib splint group demonstrated significantly higher construct stiffness than the titanium elastic nailing group (TEN) in the anterior and posterior directions (p = 0.036 and p = 0.012, respectively). Stiffness in the superior–inferior direction was higher for the rib splint but did not reach statistical significance. Rotational stability was significantly greater for the rib splint in both anterior and posterior loading, requiring higher rotational torque to achieve 5° of displacement (p = 0.005 and p = 0.01). No significant differences were observed for rotational torque in the superior or inferior directions. During cyclic loading, mean cycles to failure and initial construct stiffness did not differ significantly between groups. Interfragmentary displacement during cyclic testing showed no significant differences between fixation methods in either superior or inferior directions. Similarly, cyclic ramp loading to failure revealed no significant differences in displacement.

Discussion and conclusions: Both fixation methods demonstrated comparable biomechanical stability in this feasibility study. The rib splint might lead to fewer complications due to its slim design. Further studies are warranted to clarify the influence of the difference in implant design on clinical outcomes and construct stability.