MRI Tracking of the Effect of Bioabsorbable Pins on Bone Marrow Edema After Fixation of the Osteochondral Fragment in the Talus

Background:: Large osteochondral lesions of the talus (OLT) with good articular cartilage can be fixed by using bioabsorbable pins. These pins have various advantages but they can have adverse effects such as foreign body inflammation. This negative impact of pins on subchondral bone can be seen as bone marrow edema (BME) on magnetic resonance imaging (MRI). The purpose of this study was to investigate the course of change in BME on MRI, including osteolytic change around pins in OLT treated with pin fixation.

Methods:: This study comprised 13 ankles in 12 patients, who underwent surgeries to fix an OLT using poly-l-lactide acid pins. MRIs were taken at preoperative, 3, 6, and 12 months after surgery. The area of BME was measured at each time point, and osteolytic change around pins was evaluated. Moreover, pin insertion angle was measured.

Results:: BME significantly decreased from preoperative to 6 and 12 months. At 1 year, 28.1% of pins exhibited osteolytic change around them. Pin insertion angle was significantly lower in those with osteolytic change than those with no osteolytic change. At 3 and 6 months and 1 year postoperatively, BME with osteolytic change was significantly greater than those patients with no osteolytic change. The American Orthopaedic Foot & Ankle Society score significantly improved from preoperative (76.6±3.4 points) to 1 year after surgery (98.5±3.8 points).

Conclusion:: A shallow pin insertion angle was associated with osteolytic change around pins and persistence of BME on MRI, although excellent results were obtained at 1 year after surgery.

Level Of Evidence:: Level III, retrospective comparative series.