Development and Verification of a Porous Acetabular Shell Design Manufactured Using Additive Technology.

Introduction: Porous surface acetabular shells have been successfully used in cementless total hip arthroplasty. Recent advances in additive manufacturing have provided opportunities to optimize the shell designs. The current study describes the design and verification of a new acetabular shell design.

Materials And Methods: Additive manufacturing technology was used to fabricate acetabular shells using Ti6Al4V powder. A large computed tomography (CT) database was used to verify the screw hole location to ensure the screw trajectories were directed in the safe zone. Benchtop stability tests were conducted to compare the fixation stability of the new shell design to a clinically successful design.

Results: Shells were designed with an average pore size of 434 microns, surface porosity of 76%, and a coefficient of friction of 1.2. The CT analysis of various shell orientations demonstrated that at least two useful screws were typically directed toward the acetabular safe zone. The sawbone testing showed that the fixation stability of the new shell was either better or equivalent to the clinically successful design under two different bone preparation conditions.

Conclusions: Using additive manufacturing technology, thin walled acetabular shells were fabricated which allowed for at least two ancillary fixation screws in the safe zone. The thin walls enable the use of a 36mm femoral head with a 48mm diameter shell which may enhance the joint stability in small stature patients. The equivalent or better fixation stability of the new design indicates that good initial fixation may be expected in vivo.