Bone formation and resorption in patients after implantation of β-tricalcium phosphate blocks with 60% and 75% porosity in opening-wedge high tibial osteotomy

Abstract

Most of the implanted porous β-tricalcium phosphate (β-TCP) can be resorbed. However, β-TCP block with 75% porosity is inadequate for weight-bearing sites until bone incorporation occurs. Thus, the authors have recently developed β-TCP block with 60% porosity, which is approximately sevenfold greater in terms of compressive strength than that of β-TCP with 75% porosity. The authors investigated bone formation and resorption of β-TCP after implantation in patients of β-TCP blocks with two different porosities. From May 2003 to November 2004, medial opening high tibial osteotomy was performed in 25 patients with a mean age of 66 years. The opened defect was fixed with a Puddu plate. Then 6-8 cm3 of β-TCP block with 75% porosity was used to fill the cancellous bone defect, except on the medial side where 2.83-3.18 cm3 of wedge-shaped β-TCP block with 60% porosity was implanted. At least 2 years after surgery, the 25 patients had no correction loss, and bone formation was noted in all cases. Complete or nearly complete resorption of β-TCP with 60 and 75% porosity was obtained within 3.5 years. Thirteen biopsy samples obtained from the 60% porosity implantation sites showed good lamellar bone formation, and the percentage of β-TCP remaining relative to the newly formed bone plus β-TCP ranged from 0.3 to 14.5%, with a mean of 6.7%. The authors suspect that mechanical stress loading to the medial side of the tibia facilitated bone formation and resorption of β-TCP with 60% porosity. © 2008 Wiley Periodicals, Inc.