The effects of dynamic loading on intracalcaneal wood implants and on the tissues surrounding them

The dorsal parts of the calcanei of rabbits were resected and replaced with similarly-shaped implants made of ash wood. In each case the Achilles tendon was reinserted into the projecting part of the implant so as to subject the latter to the dynamic loads generated by use of the limb. The implants were removed from some of the animals after 5 weeks and from the others after 14 weeks. They were evaluated by preparing undecalcified microtome sections and ground sections which were examined by light microscopy and microradiography. Some of the animals underwent vital staining so as to produce polychromatic sequential labelling of the calcaneal specimens. In the area of insertion of the Achilles tendon soft tissue grew into the larger pores of the wood and, in some cases, differentiated into cartilage. Every implant remained stably anchored in the calcaneus. In every animal the intracalcaneal part of the implant became surrounded by new bone which was in direct contact with the surface of the implant and which also formed in the pores of the wood, even all rabbits loaded the operated foot. The formation of new bone in and around the implants demonstrates the basic feasibility of using ash wood as an isoelastic implant material in bone.