Bone substitutes and implantation depths for subchondral bone repair in osteochondral defects of porcine knee joints.

Abstract

PURPOSE: The purpose of this study was to identify the optimal material and implantation method for subchondral bone repair. METHODS: Four osteochondral defects in a femoral groove were created in both knees of 12 pigs, and the total number of defects was 96. Eight defects were left empty (empty group). Beta-tricalcium phosphate (β-TCP) bone substitutes with 75 and 67 % porosity were implanted in 30 and 29 defects, respectively (β-TCP75 and β-TCP67 groups). Hydroxyapatite (HA) bone substitutes with 75 % porosity were filled in 29 defects (HA group). Bone substitutes were implanted at 0, 2, or 4 mm below the subchondral bone plate (SBP). The reparative tissue was assessed using microfocus computed tomography and histology 3 months after implantation. RESULTS: Regardless of the kind of bone substitutes, the defects were filled almost completely after implanting them at the level of the SBP, while the defects remained after implanting them at 2 or 4 mm below the SBP. Reparative tissue of the β-TCP75 group was similar to the normal cancellous bone, while that of the β-TCP67 or HA group was not. CONCLUSIONS: Subchondral bone defects were filled almost completely only when bone substitutes were implanted at the level of the SBP. The reparative tissue after implanting the β-TCP bone substitutes with 75 % porosity was the most similar to the normal cancellous bone. Therefore, implanting the β-TCP bone substitutes with 75 % porosity at the level of the SBP could be recommended as a treatment method for subchondral bone repair in osteochondral defects. LEVEL OF EVIDENCE: I.