Corrugated Sheet of Unsintered Hydroxyapatite Poly-L-Lactide for Sternal Fixation: A Preclinical Study

Purpose: To stabilize the sternum after median sternotomy, unsintered hydroxyapatite poly-L-lactide (u-HA/PLLA) sternal pins are frequently used in Japan. However, sternal pins are ineffective in the fragile bone marrow. Thus, a corrugated sheet made of u-HA/PLLA was developed as a new sternal fixation device. Methods: To examine the effects of the device, we measured the shear force using a sternal model and cadaver. The shear force of the corrugated sheet, sternal pin, and simple wire was compared. The device size was determined after reviewing the sternal computed tomography (CT) of 128 patients. Results: The shear force of the model with the corrugated sheet (286 [256–295] N) was higher than that with sternal pins (135 [134–139] N, p = 0.03) and simple wire (94 [90–104] N, p = 0.03) at 2-mm displacement. In the cadaver test, the shear force of the sternal halves with the device was about two times higher than that without the device. Retrospective CT showed that 18-mm wide device applies to 99% male and 87% female patients at the fourth intercostal level. Conclusion: The corrugated sheet might provide a stronger fixation effect in the fragile bone marrow. The device width was modified to 18 mm to be applicable for most Japanese patients.