A comparative radiological assessment of polylactide pins over 3 years in vivo

Biodegradable polylactide implants allow secure fixation of osteochondral fractures with minimal adverse effects. The goal of this prospective, randomized animal study was to show whether osteoconductive effects can be achieved through the development of poly-L/DL(70/30)lactide composite implants with 10% beta-tricalcium phosphate, and whether degradation can be positively influenced and adverse effects minimized using such implants. An additional goal was to clarify which radiological procedure is most suitable to observe the course of follow-up. Thirtysix medial femoral condyle osteotomies of sheep were fixed with either 3 poly-L/DL-lactide pins or 3 composite pins, and the pin canal widths were measured with conventional radiographs, with CT, MRI, and histologically after 3, 18, and 36 months. All fractures healed completely without displacement or clinically relevant complications. The pin canals dilated secondary to pin degradation at the 12th month, and then decreased in size later. At 36 months, the pins had microscopically disappeared, and the canals were filled with bone or scar tissue. There were no statistically significant differences between the pin-types. Poly-L/DL-lactide pins and composite C-pins are suitable for secure fixation of small osteochondral fractures. Osteoconductive effects of biocompatibility or osseous integration relating to composite development were not evident. Conventional radiography and computer tomography were suitable techniques for observation of pin canals. Due to frequently observed artifact, MRI was not suitable to observe the course of the implants.