A comparative study of two types of sternal pins used for sternal closure: Poly-l-lactide sternal pins versus uncalcined hydroxyapatite poly-l-lactide sternal pins

Bioabsorbable poly-l-lactide (PLLA) sternal pins are applied to reinforce sternal closure during cardiac surgery. However, these pins lack osteoconductivity. A new bioabsorbable sternal pin with osteoconductivity, made of uncalcined hydroxyapatite and poly-l-lactide (u-HA-PLLA) has been developed. This study was conducted to compare the two types of sternal pins in terms of sternal stability and healing after median sternotomy. Between October 2006 and January 2012, 105 patients underwent aortic surgery for aortic aneurysms or dissection via median sternotomy and sternal closure with sternal pins. Among these patients, 75 were followed for 12 months using serial computed tomography (CT). PLLA sternal pins were used in 30 patients (group A) and u-HA-PLLA sternal pins were used in 45 patients (group B). The incidence rates of transverse sternal dehiscence, anteroposterior displacement and complete sternal fusion were evaluated using CT. The cross-sectional cortical bone density area (CBDA) of the sternum around the sternal pins was examined to evaluate the osteoconductivity of the sternal pins. There were no significant differences between groups A and B in the sternal dehiscence rate (6.7 vs 4.4 %), sternal displacement rate (6.7 vs 2.2 %) or 12-month sternal fusion rate (63.3 vs 73.3 %). The CBDA around the sternal pins significantly increased between discharge and 12 months after surgery in group B (P < 0.001) but not in group A. These results show that u-HA-PLLA sternal pins exhibit certain osteoconductivity; however, both PLLA and u-HA-PLLA sternal pins provide comparable clinical outcomes regarding sternal stability and healing.