The Histology and Biomechanical Study of the Effect of Hydroxyapatite Impregnated Bone Cement Implanted in Rabbit Femur

Kim, Yong Sik; Kwon, Soon Yong; Kim, Sung Soo; Lee, Seong Jae; Yoon, Jong Kie; Woo, Young Kyun

Abstract

Hydroxyapatite particle(HA) impregnated polymethylmethacrylate(PMMA) bone cement was fabricated in order to induce bony tissue ingrowth into the pores left behind by the resorption of the HA. The amount of HA was 0, 10, and 30% by weight. After mixing the HA with bone cement it was cast in a 4mm inside diameter glass under(10mm long). Each specimen was cut into half and used for in vitro and in vivo experiment. Diametral and compressive mechanical test were made to evaluate it's mechanical properties. SEM(scanning electron microscope) and ESCA(electron spectroscopy for chemical analysis) were used to evaluate the surface characteristics of the specimen. Push-out test and histologic studies were made after implanting the specimens for 6 weeks in the distal portion of rabbit femur. The mechanical test results show that the average flexural and diametral strength decreased linearly with the increased amount of HA significant(p < 0.05). The SEM and qualitative analysis using ESCA of the implant specimens showed no definite exposure of HA particles due to PMMA covering the surface. The surface of the implanted specimens were ground for histologic comparative analysis and the halves of each sample were decalcified. The interfacial shear strength of the implanted specimens showed significant increases in the 30% HA specimens compared with the 0% ones but the 10% specimens did not show any difference. However, there was also no statistically significant(p>0.05) difference between nondecalcified and decalcified specimens in each 10% and 30%, although the latter showed higher interfacial shear strength. Histologic observation showed little evidence of bone ingrowth into HA, but not remarkable. In conclusion, this study could not confirm the earlier results of the bone particle impregnated bone cement without surface grinding since the HA particles were not exposed at the surface by casting it into a glass tube.