Objectives: Bone rivets were developed as an alternative method to fasten plates during internal fixation of fractures when screw anchorage may be inadequate. This study examined whether such rivets allow proper fracture healing without eliciting adverse bone remodelling and whether they can be removed safely.
Methods: A proximal diaphyseal fracture of the tibia was stabilized with a conventional plate (low-contact dynamic compression plate, Synthes) in 10 sheep. The distal fragment was anchored using bicortical screws, and the proximal fragment (1-2.5 mm thick cortex) with 3 rivets following screw stripping. Postoperative care included immediate weight bearing and biweekly radiographs. After 12 weeks, implants were removed from 6 sheep and the tibial strength measured. Tibiae with empty and filled rivet holes (at 12 and 24 weeks) were examined histologically.
Results: In all sheep, secondary bone healing was observed without length and angulation deformities. All fracture gaps were bridged and filled with new bone. The average torsional strength after 12 weeks was 75 +/- 11% of the intact tibia (mean +/- SD), and failure never occurred through an empty rivet hole. After 12 weeks, there was intensive cortical remodelling at the rivets correlating with slight to moderate nonprogressive periosteal radiolucency around 55% of the rivets. However, there was also endosteal appositional bone growth at 85% of the rivets. There was no observable macroscopic or microscopic osseous damage after implant removal. After 24 weeks, remodelling activity had decreased and was noted only sporadically.
Conclusions: In this study, the efficacy of bone rivets for the internal fixation of a fracture with plates, where anchorage of screws may be difficult and/or insufficient, was demonstrated.