Vibratory and conventional impaction of acetabular components into porcine acetabula.

Abstract

Aims: Sufficient primary implant stability with minimal bone damage is one of the challenges for uncemented implant fixation to prevent periprosthetic fractures and implant loosening. A pilot study on a non-viscoelastic material (polyurethane foam) showed a reduced impaction force when using vibratory implant insertion. This study assessed the effectiveness of vibratory implant insertion compared to an established implant insertion method in physiological viscoelastic bone from porcine hips.

Methods: Acetabular components were impacted line-to-line and into 1 mm nominal undersized cavities in porcine acetabula (n = 24 in total, n = 6 acetabula per group of study) using vibration (60 Hz) and 1 Hz (established) impaction methods. The impaction force, remaining polar gap, and lever-out moment were measured and compared between the impaction methods and different press-fits.

Results: The vibratory impaction method produced almost 40% lower impaction forces at both press-fit levels. However, complete seating at the nominal press-fit of 1 mm was not achieved, and primary stability was lower for the vibratory impaction for either press-fit.

Conclusion: Bone fracture risk due to high impaction forces could be reduced by vibrational implant insertion at the cost of a reduction in primary stability. The outcome of the vibratory impaction method in porcine bone was similar to a previous study using polyurethane foams, suggesting that the viscoelasticity of bone may not play a crucial role during press-fit implant impaction.