Effect of implant surface roughness on bone fixation: the differences between bone and metal pegs

Pegs made from cortical bone are used to fix osteochondral fractures and osteochondral dissecans. This technique has many advantages, but it requires long-term immobilization. This study examined the effect of surface roughness on fixation with bone and metal pegs.

Pegs with either rough or smooth surfaces were made of cortical bone from Japanese black cattle or from stainless steel (SUS316L). The mean roughness of the rough surface was 15.0 microm, whereas that of the smooth surface was less than 0.6 microm. Pegs were inserted into holes made in the distal femurs of 34 rabbits. At the time of surgery and 14 days later, mechanical tests and micro-computed tomography were performed.

At the time of surgery, although the push-out forces were less than 0.3 N, the rough surface had a higher value than the smooth surface (P = 0.0002). No difference was observed according to the material (P = 0.54). Fourteen days after surgery, no significant difference was detected in the push-out forces between bone pegs with rough and smooth surfaces (489.0 +/- 149.6 vs 478.3 +/- 134.4 N (mean +/- SD), respectively), but a marked difference was seen with the metal pegs (235.7 +/- 115.7 vs 2.2 +/- 1.6 N). The bone pegs with rough surfaces made contact with the recipient bone at the high points on the abraded surfaces. After the mechanical tests, the fusion was broken within the new bone for bone pegs with rough or smooth surfaces, but no breakage occurred at the junction of bone peg and new bone.

The surface roughness of bone pegs has little effect on bone-to-bone fusion 2 weeks postoperatively, unlike the effect with metal pegs.