The influence of hydroxyapatite granules on the healing of a segmental defect filled with autologous bone marrow

Hydroxyapatite(HA) ceramics are frequently used as a bone graft substitutes for the filling of bony defects. The addition of autologous bone marrow to HA ceramics does improve defect healing. There is conflicting evidence in the literature whether autologous bone marrow transplatation alone is as ef fective as the combination of HA ceramics and bone marrow combined. It was the purpose of this study to identify the role of additional HA ceramic gra nules on the healing of a sheep tibia segmental defect filled with autologo us bone marrow. After permission of the local animal rights committee was obtained, a 3 cm segmental defect in the midshaft of 31 adult sheep was stabilized with an u nreamed tibia nail. The animals were divided into 4 groups according to the mode of defect filling: HA plus autologous bone marrow (HA+MAR) (n=8), aut ologous bone marrow (MAR) (n=9), empty defect (DEF) (n=6), cancellous bone graft (CAN) (n=8). After three months follow up animals were sacrificed and analysed for the key parameters of union and maximum torque at failure. One nonunion was present in each of the HA+MAR, MAR, and CAN groups. Four o f the six animals in the DEF group developed a nonunion. Maximum torque at failure was reported as percentage of the intact contralateral tibia: HA+MA R 39%+/-24%, MAR 26%+/-17%, DEF 22%+/-13%, CAN 41%+/-20%. The difference be tween the groups was statistically significant, but appeared to be relevant . We conclude from our data, that HA ceramics do improve healing of a segment al defect in the sheep tibia filled with autologous bone marrow. The result s of this combination are comparable to cancellous autograft.