Does implantation site influence bone ingrowth into 3D-printed porous implants?

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Regenerative Medicine

Background:

• Osseointegration, the biological fixation of implants, is crucial for implant success.
• The effectiveness of osseointegration may depend on the anatomical location and biomechanical forces acting on the implant.
• 3D-printed implants offer novel designs for enhanced bone integration.

Purpose of the Study:

• To investigate how the anatomical site influences the osseointegration of 3D-printed implants.
• To compare bone ingrowth in different bone types (cortical vs. cancellous) and in spinal fusion models.

Main Methods:

• A preclinical study in adult sheep compared 3D-printed titanium alloy implants in long bone cortical and cancellous sites.
• Evaluated bone ingrowth using radiography, mechanical testing, and histology at 4 and 12 weeks.
• Assessed single-level lumbar interbody fusions using 3D-printed cages with autograft or allograft.

Main Results:

• Bone ingrowth was robust in cortical bone sites but limited in cancellous sites, even with press-fit implantation.
• Osseointegration into porous interbody cages resembled cancellous bone response, not cortical bone.
• Porous domains of implants showed fibrovascular tissue, with limited bone integration into cages unless fusion occurred within the aperture.

Conclusions:

• Anatomical site significantly impacts the in vivo response of 3D-printed implants.
• Bone ingrowth observed in long bone cortical and cancellous sites does not directly predict success in interbody fusion applications.
• Factors like surgical technique, biomechanics, and graft choice are critical for successful osseointegration in different anatomical contexts.