MR-IMAGING OF BIODEGRADABLE POLYLEVOLACTIDE OSTEOSYNTHESIS DEVICES INTHE ANKLE

Objective: To assess the feasibility of magnetic resonance (MR) imagin g in the postoperative follow-up after internal fracture fixation usin g biodegradable polylevolactide (PLLA) plugs and to investigate the MR characteristics of these devices. Study Design and Methods: MR findin gs in ten patients with displaced malleolar fractures treated by inter nal fixation using absorbable PLLA plugs were evaluated after three di fferent postoperative periods. The average postoperative follow-up tim e was thirty months for four patients, forty-two months for another fo ur patients, and fifty-one months for the remaining two patients. Resu lts: On T1-weighted coronal images, the geometry of the PLLA plug was clearly visible in all cases, without signs of fatigue failure or abso rption. The host-to-tissue area between the deployed two fins of the p lug showed higher signal intensity than the surrounding cancellous bon e on fat-saturated proton density (PD) and turbo inversion recovery (t IR) images. This area had signal intensity similar to articular cartil age on T1-weighted coronal images. In none of the cases could any flui d accumulation be seen around the plug. In all ten cases, a thin rim w ith signal intensity similar to the area between the deployed fins was detected around the PLLA plug on fat-saturated axial PD images. On fa t-saturated T2 and tIR sequences, this rim was less clearly detectable in all cases. No differences in the signal intensity or geometry of t he PLLA plug on the MR images emerged between the three patient groups with mean follow-ups of thirty, forty-two, and fifty-one months. No a rtifacts produced by the implants were seen on any of the MR images. A biopsy specimen obtained at a reoperation necessary seventeen months postoperatively showed no signs of degradation of the PLLA plug. Concl usions: MR imaging can visualize PLLA implants within bone. It also sh ows, without artifacts, the tissue interaction between the artificial biodegradable material and bone tissue in humans.