Mechanical and histological evaluation of improved grit-blast implant in dogs: pilot study

Orthopedic fixation of irreversibly damaged joints entails the use of artificial joints. Porous coated prostheses require no bone cement, but coating to the implant is susceptible to avulsion from the surface. The purpose of this pilot study was to test an improved non-coated grit blast titanium implant having a direct surface roughness of 33.4 microm with a wide contrast of 251.6 microm between the valleys and peaks, i.e., about ten times rougher than conventional grit blast, and designed with bumpy, acutely articulated depressions. Fifty-six implants (28 grit blast, 28 smooth) were tested in the femora of 7 healthy beagles. Four roughened grit-blast implants were implanted in the left femur and four smooth implants (controls) in the right femur. The 33.4-microm grit-blasted roughening dramatically enhanced the histological effectiveness, and the mechanical effectiveness improved as a consequence. Bone-to-implant on growth attained high apposition and integrity at weeks 12 (76.38%) and 16 (80.35%). Shear strength increased with time and continued to be acceptable (14.5 MPa) at the end of the study. Bone matrix was particularly abundant and thick at the end of week 16, indicating progressive mineralization and maturation of remodeled bone matrix and compatibility of the roughened implant. In conclusion, the new grit blast device shows promise as a potentially useful prosthetic implant. Grit blast roughening would facilitate use of the bare implant without coatings or cement, would likely minimize the cost of joint fixation, and would allow relatively easy implantation.